# document

id: 2d380ead6c08cf52b33fb736dd781c7d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5242
content:
"(one standard deviation) by combining estimates based on observed \r\ninterannual variability and the cloud controlling factors."


id: f682db795fdfdd047c3aff23e826c83
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40743
content:
"Mixed-phase clouds that consist of both liquid and ice are dominant \r\nover the Southern Ocean (50degS-80degS), which accounts for 20% of the \r\nnet CRE in the present climate (Matus and L'Ecuyer, 2017). It has been \r\nargued that the cloud optical depth (opacity) will increase over the \r\nSouthern Ocean as warming drives the replacement of ice-dominated \r\nclouds with liquid-dominated clouds (Tan et al., 2019). Liquid clouds \r\ngenerally consist of many small cloud droplets, while the crystals \r\nin ice clouds are orders of magnitude fewer in number and much \r\nlarger, causing the liquid clouds to be optically thicker and thereby \r\nresulting in a  negative feedback (Boucher et  al., 2013). However, \r\nthis phase-change feedback works effectively only below freezing \r\ntemperature (Lohmann and Neubauer, 2018; Terai et al., 2019) and \r\nother processes that increase or decrease liquid water path (LWP) \r\nmay also affect the optical depth feedback (McCoy et al., 2019)."


id: 687db0f9eb3c22276d670c4d3b5fc9b1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15648
content:
"The understanding of the response of clouds to warming and \r\nassociated radiative feedback has deepened since AR5 (Figure  7.9 \r\nand FAQ 7.2). Particular progress has been made in the assessment of \r\nthe marine low-cloud feedback, which has historically been a major \r\ncontributor to the cloud feedback uncertainty but is no longer the \r\nlargest source of uncertainty. Multiple lines of evidence (theory, \r\nobservations, emergent constraints and process modelling) are now \r\navailable in addition to ESM simulations, and the positive low-cloud \r\nfeedback is consequently assessed with high confidence."


id: aa332dbbf2f0a56eab1116e3e4beef92
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27171
content:
"The best estimate of net cloud feedback is obtained by summing \r\nfeedbacks associated with individual cloud regimes and assessed \r\nto be aC = 0.42 W  m-2 degC-1. By assuming that the uncertainties \r\nof individual cloud feedbacks are independent of each other, \r\ntheir standard deviations are added in quadrature, leading to the \r\nlikely range of 0.12 to 0.72 W  m-2 degC-1 and the very likely range "


id: a0d0e3c4ab4829c74a869ce208b4f899
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 25510
content:
"Table 7.9 | Assessed sign and confidence level of cloud feedbacks in different regimes in AR5 and AR6. For some cloud regimes, the feedback was not assessed \r\nin AR5, indicated by N/A."


id: ea50c02b0ec7c333137208099e3ce3ed
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38579
content:
"In reality, different types of cloud feedback may occur simultaneously in \r\none cloud regime. For example, an upward shift of high-clouds associated \r\nwith the altitude feedback could be coupled to an increase/decrease of \r\ncirrus/anvil cloud fractions associated with the cloud amount feedback. \r\nAlternatively, slowdown of the tropical circulation with surface warming \r\n(Section 4.5.3 and Figure 7.9) could affect both high and low-clouds \r\nso that their feedbacks are co-dependent. Quantitative assessments \r\nof such covariances require further knowledge about cloud feedback \r\nmechanisms, which will further narrow the uncertainty range."


id: 4e6c42be542e04ff70dc3b9052b82ef2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11074
content:
"In summary, deepened understanding of feedback processes in \r\nindividual cloud regimes since AR5 leads to an assessment of the \r\npositive net cloud feedback with high confidence. A small probability \r\n(less than 10%) of a net negative cloud feedback cannot be ruled \r\nout, but this would require an extremely large negative feedback \r\ndue to decreases in the amount of tropical anvil clouds or increases \r\nin optical depth of extratropical clouds over the Southern Ocean; \r\nneither is supported by current evidence."


id: 6b458cbe7e9c1f4b6697a4de171fcebc
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 16172
content:
"The chemical composition of the atmosphere (beyond CO2 and water \r\nvapour changes) is expected to change in response to a  warming \r\nclimate. These changes in greenhouse gases (methane, nitrous oxide \r\nand ozone) and aerosol amount (including dust) have the potential \r\nto alter the TOA energy budget and are collectively referred to as \r\n'non-CO2 biogeochemical feedbacks'. Methane (CH4) and nitrous \r\noxide (N2O) feedbacks arise partly from changes in their emissions \r\nfrom natural sources in response to temperature change; these are \r\nassessed in Chapter  5 (Section  5.4.7; see also Figure  5.29c). Here \r\nwe exclude the permafrost CH4 feedback (Section 5.4.9.1.2) because, \r\nalthough associated emissions are projected to increase under \r\nwarming on multi-decadal to centennial time scales, on longer time "


id: 55ebff76b92cc66265c99a0a01f11bf2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
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vector_id: 12391
content:
"The feedbacks presented in the previous sections (Sections 7.4.2.1-\r\n7.4.2.4) are directly linked to physical climate variables (for example \r\ntemperature, water vapour, clouds, or sea ice). The central role of "


id: aab4fe6e68f381b92362cb1006ed30de
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
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vector_id: 27257
content:
"biogeophysical feedback associated with surface-albedo change due \r\nto changes in phytoplankton (Frouin and Iacobellis, 2002; Park et al., \r\n2015), but there is not currently enough evidence to quantitatively \r\nassess this feedback."


id: f64cb35ffa23d7f61a0a9385888707f2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40700
content:
"Given the limited number of studies, we take the full range of estimates \r\ndiscussed above for the biogeophysical feedback parameter, and \r\nassess the very likely range to be from 0.0 to +0.3 W m-2 degC-1, with \r\na central estimate of +0.15 W m-2 degC-1 (low confidence). Although this \r\nassessment is based on evidence from both models and paleoclimate \r\nproxies, and the studies above agree on the sign of the change, there is \r\nnonetheless limited evidence. Higher confidence could be obtained if \r\nthere were more studies that allowed calculation of a biogeophysical \r\nfeedback parameter (particularly from paleoclimates), and if the \r\npartitioning between biogeophysical feedbacks and physiological \r\nforcing were clearer for all lines of evidence."


id: faa327e8d5dfab85d5d1d3aa6c1e8ff8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41470
content:
"The non-CO2 biogeochemical feedbacks are assessed in \r\nSection  7.4.2.5.1 to be -0.16 [-0.37 to +0.05] W m-2 degC-1 and the \r\nbiogeophysical feedbacks are assessed in Section  7.4.2.5.2 to be \r\n+0.15  [0.0 to +0.3] W  m-2 degC-1. The sum of the biogeophysical \r\nand non-CO2 biogeochemical feedbacks is assessed to have \r\na  central value of -0.01 W m-2 degC-1 and a  very likely range from "


id: e460a6b6c224859ee7b7b093f8e2eb45
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37474
content:
"-0.27  to  +0.25 W  m-2  degC-1 (Table  7.10). Given the relatively long \r\ntime scales associated with the biological processes that mediate the \r\nbiogeophysical and many of the non-CO2 biogeochemical feedbacks, \r\nin comparison with the relatively short time scale of many of the \r\nunderlying model simulations, combined with the small number of \r\nstudies for some of the feedbacks, and the relatively small signals, this \r\noverall assessment has low confidence."


id: ed4bdf0079916de5bb5469e2523cbfbe
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39124
content:
"and as a  result, long-term simulations are often carried out with \r\nlower complexity models, and/or are asynchronously coupled."


id: fc18aa2ed9bf6543f24e708a0c4b1821
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41714
content:
"In AR5, it was described that both the Greenland and Antarctic ice \r\nsheets would continue to lose mass in a warming world (M. Collins \r\net  al., 2013), with a  continuation in sea level rise beyond the year \r\n2500 assessed as virtually certain. However, there was low confidence\r\nin the associated radiative feedback mechanisms, and as such, there \r\nwas no assessment of the magnitude of long-term radiative feedbacks \r\nassociated with ice sheets. That assessment is consistent with SROCC, \r\nwherein it was stated that 'with limited published studies to draw \r\nfrom and no simulations run beyond 2100, firm conclusions regarding \r\nthe net importance of atmospheric versus ocean melt feedbacks on \r\nthe long-term future of Antarctica cannot be made.'"


id: a4bf314126a7e71450c4adb8e595b2e7
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26207
content:
"Although long-term radiative feedbacks associated with ice sheets are \r\nnot included in our definition of ECS (Box 7.1), the relevant feedback \r\nparameter is assessed here because the time scales on which these \r\nfeedbacks act are relatively uncertain, and the long-term temperature \r\nresponse to CO2 forcing of the entire Earth system may be of interest."


id: 3d87db3b4f2b94d66f4916f55fa4e098
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7999
content:
"Table  7.10 summarizes the estimates and the assessment of the \r\nindividual and the net feedbacks presented in the above sections. \r\nThe uncertainty range of the net climate feedback was obtained by \r\nadding standard deviations of individual feedbacks in quadrature, \r\nassuming that they are independent and follow the Gaussian "


id: ae6a42ac99cd281f3f2ff1c8d1261b91
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27915
content:
"The assessment of the net climate feedback presented above is \r\nbased on a single approach (i.e., process understanding) and directly \r\nresults in a value for ECS given in Section 7.5.1; this is in contrast to \r\nthe synthesis assessment of ECS in Section  7.5.5 which combines \r\nmultiple approaches. The total (net) feedback parameter consistent \r\nwith the final synthesis assessment of the ECS and Equation 7.1 \r\n(Box 7.1) is provided there."


id: 1c62159e2d558fedbf3851f35b9b62e3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 2184
content:
"Since AR5, many modelling groups have newly participated in CMIP \r\nexperiments, leading to an increase in the number of models in \r\nCMIP6 (Section 1.5.4). Other modelling groups that contributed to \r\nCMIP5 also updated their ESMs for carrying out CMIP6 experiments. \r\nWhile some of the CMIP6 models share components and are \r\ntherefore not independent, they are analysed independently when \r\ncalculating climate feedbacks. This, and more subtle forms of model \r\ninter-dependence, creates challenges when determining appropriate \r\nmodel weighting schemes (Section 1.5.4). Additionally, it must be kept \r\nin mind that the ensemble sizes of the CMIP5 and CMIP6 models are \r\nnot sufficiently large to sample the full range of model uncertainty."


id: c1fc2277c90a8c24c3a56b793f60e2a8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 31427
content:
"The multi-model mean values of all physical climate feedbacks are \r\ncalculated using the radiative kernel method (Section  7.4.1) and \r\ncompared with the assessment in the previous sections (Figure 7.10). \r\nFor CMIP models, there is a  discrepancy between the net climate \r\nfeedback calculated directly using the time evolutions of DT and DN\r\nin each model and the accumulation of individual feedbacks, but it \r\nis negligibly small (Supplementary Material 7.SM.4). Feedbacks \r\ndue to biogeophysical and non-CO2 biogeochemical processes are \r\nincluded in some models but neglected in the kernel analysis. In AR6, \r\nbiogeophysical and non-CO2 biogeochemical feedbacks are explicitly \r\nassessed (Section 7.4.2.5)."


id: d37b3d4239843401f6af4090bc60c314
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34544
content:
"All the physical climate feedbacks apart from clouds are very similar \r\nin the CMIP5 and CMIP6 model ensembles (see also Table 7.10). These \r\nvalues, where possible supported by other lines of evidence, are used \r\nfor assessing feedbacks in Sections 7.4.2.1-7.4.2.3. A  difference \r\nfound between CMIP5 and CMIP6 models is the net cloud feedback, "


id: e146ed77ae35091b7f4cf1e4a2b8da04
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 36896
content:
"Table 7.10 | Synthesis assessment of climate feedbacks (central estimate shown in bold). The mean values and their 90% ranges in CMIP5/6 models, derived using \r\nmultiple radiative kernels (Zelinka et al., 2020) are also presented for comparison."


id: 174a86c3ec87f171fe247c62a8e6fe89
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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"which is larger in CMIP6 by about 20%. This change is the major \r\ncause of less-negative values of the net climate feedback in CMIP6 \r\nthan in CMIP5 and hence an increase in modelled ECS (Section 7.5.1)."


id: e689f2660f86eb3f0109e618bc60d3d9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
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vector_id: 37858
content:
"including those reconstructed from the past (encompassing a range \r\nof states warmer and colder than today, with varying continental \r\ngeographies) or projected for the future. If this approximation holds, \r\nthen the equilibrium global surface temperature response to a fixed \r\nradiative forcing will be constant, regardless of the climate state \r\nto which that forcing is applied."


id: cd8847c5b7424f995fffc8950577ca9d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 33492
content:
"This approximation will break down if climate feedbacks are not \r\nconstant, but instead vary as a function of, for example, background \r\ntemperature (Roe and Baker, 2007; Zaliapin and Ghil, 2010; Roe and \r\nArmour, 2011; Bloch-Johnson et al., 2015), continental configuration \r\n(Farnsworth et al., 2019), or configuration of ice sheets (Yoshimori \r\net al., 2009). If the real climate system exhibits this state-dependence, \r\nthen the future equilibrium temperature change in response to \r\nlarge forcing may be different from that inferred using the standard \r\nframework, and/or different to that inferred from paleoclimates. Such \r\nconsiderations are important for the assessment of ECS (Section 7.5). \r\nClimate models generally include representations of feedbacks that \r\nallow state-dependent behaviour, and so model results may also \r\ndiffer from the predictions from the standard framework."


id: a15d9c9099ddd5c27102dbf60e67cfae
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 25607
content:
"In AR5 (Boucher et  al., 2013), there was a  recognition that climate \r\nfeedbacks could be state-dependent (Colman and McAvaney, 2009), \r\nbut modelling studies that explored this (e.g., Manabe and Bryan, 1985; \r\nVoss and Mikolajewicz, 2001; Stouffer and Manabe, 2003; Hansen et al., \r\n2005b) were not assessed in detail. Also in AR5 (Masson-Delmotte \r\net  al.,  2013), it was assessed that some models exhibited weaker \r\nsensitivity to Last Glacial Maximum (LGM; Cross-Chapter Box  2.1) \r\nforcing than to 4xCO2 forcing, due to state-dependence in shortwave \r\ncloud feedbacks."


id: acf2a9893797e2e8363bf2bd0803f88a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27668
content:
"In the standard framework of forcings and feedbacks (Section 7.4.1 \r\nand Box 7.1), the approximation is made that the strength of climate \r\nfeedbacks is independent of the background global mean surface \r\ntemperature. More generally, the individual feedback parameters, \r\nax, are often assumed to be constant over a range of climate states, "


id: c58ad8ed71e89125f87a9909d6f10111
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32061
content:
"Here, recent evidence for state-dependence in feedbacks from \r\nmodelling studies (Section  7.4.3.1) and from the paleoclimate \r\nrecord (Section 7.4.3.2) are assessed, with an overall assessment in \r\nSection 7.4.3.3. The focus is on temperature-dependence of feedbacks \r\nwhen the system is in equilibrium with the forcing; evidence for transient \r\nchanges in the net feedback parameter associated with evolving spatial \r\npatterns of warming is assessed separately in Section 7.4.4."


id: 732f86b96131108741a967d100d33a3c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17514
content:
"LGM, provide conflicting evidence of either decreased (Yoshimori \r\net al., 2011) or increased (Kutzbach et al., 2013; Stolpe et al., 2019) \r\ntemperature response per unit forcing during cold climates compared \r\nto the modern era."


id: 7dc51376904641cfdad010edd36d0bae
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19302
content:
"In contrast to most ESMs, the majority of Earth system models of \r\nintermediate complexity (EMICs) do not exhibit state-dependence, \r\nor have a  net feedback parameter that decreases with increasing \r\ntemperature (Pfister and Stocker, 2017). This is unsurprising since \r\nEMICs usually do not include process-based representations of \r\nwater-vapour and cloud feedbacks. Although this shows that care \r\nmust be taken when interpreting results from current generation \r\nEMICs, Pfister and Stocker (2017) also suggest that non-linearities \r\nin feedbacks can take a long time to emerge in model simulations \r\ndue to slow adjustment time scales associated with the ocean; \r\nlonger simulations also allow better estimates of equilibrium \r\nwarming (Bloch-Johnson et al., 2020). This implies that multi-century \r\nsimulations (Rugenstein et  al., 2020) could increase confidence in \r\nESM studies examining state-dependence."


id: 7cce2f037eb67fda6e3df64100c44e3d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19153
content:
"The possibility of more substantial changes in climate feedbacks, \r\nsometimes accompanied by hysteresis and/or irreversibility, has been \r\nsuggested from some theoretical and modelling studies. It has \r\nbeen postulated that such changes could occur on a global scale and \r\nacross relatively narrow temperature changes (Popp et al., 2016; von \r\nder Heydt and Ashwin, 2016; Steffen et al., 2018; Schneider et al., \r\n2019; Ashwin and von der Heydt, 2020; Bjordal et al., 2020). However, \r\nthe associated mechanisms are highly uncertain, and as such there is \r\nlow confidence as to whether such behaviour exists at all, and in the \r\ntemperature thresholds at which it might occur."


id: fe805dfe6ff4c5314e97005304af5147
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 42148
content:
"Overall, the modelling evidence indicates that there is medium \r\nconfidence that the net feedback parameter, a, increases (i.e., becomes \r\nless negative) with increasing temperature (i.e., that sensitivity \r\nto forcing increases with increasing temperature), under global \r\nsurface background temperatures at least up to 40degC (Meraner \r\net  al., 2013; Seeley and Jeevanjee, 2021), and medium confidence\r\nthat this temperature dependence primarily derives from increases \r\nin the water-vapour and shortwave cloud feedbacks. This assessment \r\nis further supported by recent analysis of CMIP6 model simulations \r\n(Bloch-Johnson et al., 2020) in the framework of nonlinMIP (Good \r\net  al., 2016), which showed that out of 10 CMIP6 models, seven \r\nof them showed an increase of the net feedback parameter with \r\ntemperature, primarily due to the water-vapour feedback."


id: 575181a4b0f5faada22f50961f0919d6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12619
content:
"Several studies have estimated ECS from observations of the \r\nglacial-interglacial cycles of the last approximately 2 million years, \r\nand found a  state-dependence, with more-negative a (i.e.,  lower \r\nsensitivity to forcing) during colder periods of the cycles and \r\nless-negative a during warmer periods (von der Heydt et al., 2014; \r\nKohler et al., 2015, 2017; Friedrich et al., 2016; Royer, 2016; Snyder, \r\n2019); see summaries in Skinner (2012) and von der Heydt et  al. \r\n(2016). However, the nature of the state-dependence derived from \r\nthese observations is dependent on the assumed ice-sheet forcing "


id: 9871b153b018d9fd52d25994fb1b4393
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 24032
content:
"Paleoclimate proxy evidence from past high-CO2 time periods much \r\nwarmer than present (the early Eocene and Paleocene-Eocene \r\nThermal Maximum, PETM; Cross-Chapter Box  2.1) show that the \r\nfeedback parameter increases as temperature increases (Anagnostou \r\net  al., 2016, 2020; Shaffer et  al., 2016). However, such \r\ntemperature-dependence of feedbacks was not found in the warm \r\nPliocene relative to the cooler Pleistocene (Martinez-Boti et al., 2015), \r\nalthough the temperature changes are relatively small at this time, \r\nmaking temperature-dependence challenging to detect given the \r\nuncertainties in reconstructing global mean temperature and forcing. \r\nOverall, the paleoclimate proxy record provides medium confidence\r\nthat the net feedback parameter, a, was less negative in these past \r\nwarm periods than in the present day."


id: edaabccaeffb91834b7f8469e66ebc1c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39176
content:
"lines of evidence would be obtained from stronger constraints on \r\natmospheric CO2 concentrations, ice-sheet forcing, and temperatures, \r\nduring past warm climates."


id: 5d46a43d8cc5220fb2905bae387f936c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 13687
content:
"The large-scale patterns of surface warming in observations since \r\nthe 19th  century (Section  2.3.1) and climate model simulations \r\n(Section  4.3.1 and Figure  7.12a) share several common features. \r\nIn particular, surface warming in the Arctic is greater than for the \r\nglobal average and greater than in the Southern Hemisphere (SH) \r\nhigh latitudes; and surface warming is generally greater over land \r\nthan over the ocean. Observations and climate model simulations \r\nalso show some notable differences. ESMs generally simulate \r\na weakening of the equatorial Pacific Ocean zonal (east-west) SST \r\ngradient on multi-decadal to centennial time scales, with greater \r\nwarming in the east than the west, but this trend has not been seen \r\nin observations (Section 9.2.1 and Figure 2.11b)."


id: e1b75755ab8ffab5e9c1027bedd8819d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36986
content:
"Chapter 4 (Section 4.5.1) discusses patterns of surface warming for \r\n21st-century climate projections under the Shared Socio-economic \r\nPathways (SSP) scenarios. Chapter  9 (Section  9.2.1) assesses \r\nhistorical SST trends and the ability of coupled ESMs to replicate the \r\nobserved changes. Chapter 4 (Section 4.5.1) discusses the processes \r\nthat cause the land to warm more than the ocean (land-ocean \r\nwarming contrast). This section assesses process understanding of \r\nthe large-scale patterns of surface temperature response from the "


id: 65e1374e9ec152e9d75b9eb30924adf1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15186
content:
"perspective of a regional energy budget. It then assesses evidence \r\nfrom the paleoclimate proxy record for patterns of surface warming \r\nduring past time periods associated with changes in atmospheric CO2\r\nconcentrations. Finally, it assesses how radiative feedbacks depend \r\non the spatial pattern of surface temperature, and thus how they \r\ncan change in magnitude as that pattern evolves over time, with \r\nimplications for the assessment of ECS based on historical warming \r\n(Sections 7.4.4.3 and 7.5.2.1)."


id: 770f26184a4fb96cdc537d1c34ec7ae1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18147
content:
"circulations (Alexeev et  al., 2005; Held and Soden, 2006; Hwang \r\nand Frierson, 2010; Hwang et al., 2011; Kay et al., 2012; Huang and \r\nZhang, 2014; Feldl et al., 2017a; Donohoe et al., 2020). ESMs project \r\nthat within the mid-latitudes, where eddies dominate the heat \r\ntransport, an increase in poleward latent energy transport arises from \r\nan increase in the equator-to-pole gradient in atmospheric moisture \r\nwith global warming, with moisture in the tropics increasing more \r\nthan at the poles as described by the Clausius-Clapeyron relation \r\n(Section  8.2). This change is partially compensated by a  decrease \r\nin dry-static energy transport arising from a  weakening of the \r\nequator-to-pole temperature gradient as the polar regions warm \r\nmore than the tropics."


id: 35a44fe77eb3005bd897631f5c773d12
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6690
content:
"Several processes contribute to polar amplification under greenhouse \r\ngas forcing, including the loss of sea ice and snow (an amplifying \r\nsurface-albedo feedback), the confinement of warming to near the \r\nsurface in the polar atmosphere (an amplifying lapse-rate feedback), \r\nand increases in poleward atmospheric and oceanic heat transport \r\n(Pithan and Mauritsen, 2014; Goosse et al., 2018; Dai et al., 2019; \r\nFeldl et  al., 2020). Modelling and process studies since AR5 have \r\nled to an improved understanding of the combined effect of these \r\ndifferent processes in driving polar amplification and how they differ \r\nbetween the hemispheres."


id: 5a7b73ce3636563dac9beec2d6d8418e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 13175
content:
"Regional energy budget analyses are commonly used to diagnose the \r\nrelative contributions of radiative feedbacks and energy fluxes to polar \r\namplification as projected by ESMs under increased CO2 concentrations \r\n(Figure  7.12; Feldl and Roe, 2013; Pithan and Mauritsen, 2014; \r\nGoosse et al., 2018; Stuecker et al., 2018). These analyses suggest that \r\na primary cause of amplified Arctic warming in ESMs is the latitudinal \r\nstructure of radiative feedbacks, which warm the Arctic more than \r\nthe tropics (Figure  7.12b), and enhanced latent energy transport \r\ninto the Arctic. That net atmospheric heat transport into the Arctic \r\ndoes not change substantially within ESMs, on average, under CO2\r\nforcing (Figure 7.12b) reflects a compensating decrease in poleward \r\ndry-static energy transport as a response to polar amplified warming \r\n(Hwang et al., 2011; Armour et al., 2019; Donohoe et al., 2020). The \r\nlatitudinal structure of radiative feedbacks primarily reflects that of "


id: 4a04717c04858374c988b0f1f052a288
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10264
content:
"Idealized modelling studies suggest that polar amplification would \r\noccur even in the absence of any amplifying polar surface-albedo \r\nor lapse-rate feedbacks owing to changes in poleward atmospheric \r\nheat transport under global warming (Hall, 2004; Alexeev et al., 2005; \r\nGraversen and Wang, 2009; Alexeev and Jackson, 2013; Graversen \r\net al., 2014; Roe et al., 2015; Merlis and Henry, 2018; Armour et al., \r\n2019). Poleward heat transport changes reflect compensating \r\nchanges in the transport of latent energy (moisture) and dry-static \r\nenergy (sum of sensible and potential energy) by atmospheric "


id: c8a1e1adcb8d1c7ea44db0ae70f4232a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32614
content:
"Figure 7.12 | Contributions of effective radiative forcing, ocean heat uptake, atmospheric heat transport, and radiative feedbacks to regional surface \r\ntemperature changes at year 100 of abrupt4xCO2 simulations of CMIP6 Earth system models (ESMs). "


id: 34826fd44174eecb2ff737c03001a89d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6474
content:
"The magnitude of polar amplification also depends on the type of \r\nradiative forcing applied (Section  4.5.1.1; Stjern et  al., 2019), with \r\nChapter  6 (Section  6.4.3) discussing changes in sulphate aerosol \r\nemissions and the deposition of black carbon aerosols on ice and \r\nsnow as potential drivers of amplified Arctic warming. The timing of "


id: 411d0c1527bfb35a9e15a5b999613c09
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8636
content:
"The energy budget analyses (Figure 7.12) suggest that greater surface \r\nwarming in the Arctic than the Antarctic under greenhouse gas forcing \r\narises from two main processes. The first is large surface heat uptake \r\nin the Southern Ocean (Figure 7.12c) driven by the upwelling of deep "


id: b9dc4e2a299c6afa4cb8a688ba609b57
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29918
content:
"long-term feedbacks associated with ice sheets (Section 7.4.2.6), and \r\nin particular for the Early Eocene there is a forcing associated with \r\npaleogeographic change (Farnsworth et al., 2019). However, because \r\nthese non-CO2 effects can all be included as boundary conditions in \r\nmodel simulations, these time periods allow an assessment of the \r\npatterns of modelled response to known forcing (although uncertainty \r\nin the forcing increases further back in time). Because these changes \r\nto boundary conditions can be complex to implement in models, \r\nand because long simulations (typically longer than 500 years) are \r\nrequired to approach equilibrium, these simulations have been carried \r\nout mostly by pre-CMIP6 models, with relatively few (or none for the \r\nEarly Eocene) fully coupled CMIP6 models in the ensembles."


id: 122ac554e5e0f0becf3f6943d08865eb
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 386
content:
"At the time of AR5, polar amplification was evident in proxy \r\nreconstructions of paleoclimate sea surface temperature (SST) \r\nand surface air temperature (SAT) from the LGM, MPWP and the \r\nEarly Eocene, but uncertainties associated with proxy calibrations \r\n(Waelbroeck et  al., 2009; Dowsett et  al., 2012; Lunt et  al., 2012a) \r\nand the role of orbital forcing (for the MPWP; Lisiecki and Raymo, \r\n2005) meant that the degree of polar amplification during these \r\ntime periods was not accurately known. Furthermore, although some \r\nmodels (CCSM3; Winguth et al., 2010; Huber and Caballero, 2011) \r\nat that time were able to reproduce the strong polar amplification \r\nimplied by temperature proxies of the Early Eocene, this was achieved \r\nat higher CO2 concentrations (>2000 ppm) than those indicated by \r\nCO2 proxies (<1500 ppm; Beerling and Royer, 2011)."


id: 892250cf7e418e2da99d3c856527146a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 21293
content:
"Since AR5 there has been progress in improving the accuracy of proxy \r\ntemperature reconstructions of the LGM (Cleator et al., 2020; Tierney \r\net  al., 2020b), the MPWP (McClymont et  al., 2020), and the Early \r\nEocene (Hollis et al., 2019) time periods. In addition, reconstructions \r\nof the MPWP have been focused on a short time slice with an orbit \r\nsimilar to modern-day (isotopic stage KM5C; Haywood et al., 2013, \r\n2016b). Furthermore, there are more robust constraints on CO2\r\nconcentrations from the MPWP (Martinez-Boti et  al., 2015; de la \r\nVega et  al., 2020) and the Early Eocene (Anagnostou et  al., 2016, \r\n2020). As such, polar amplification during the LGM, MPWP, and Early \r\nEocene time periods can now be better quantified than at the time \r\nof AR5, and the ability of climate models to reproduce this pattern \r\ncan be better assessed; model-data comparisons for SAT and SST for \r\nthese three time periods are shown in Figure 7.13."


id: 33cab2adaa90db432d90a4dcd51d642f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6355
content:
"7.4.4.1.2 Polar amplification from proxies and models during \r\npast climates associated with CO2 change"


id: 42f78e840efc9942eb72148210c4f112
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8979
content:
"with the most data and the time period with the least uncertainty in \r\nmodel boundary conditions, polar amplification in the PMIP4 ensemble \r\nmean is in good agreement with the proxies, especially for SAT (medium \r\nconfidence). Overall, the confidence in the ability of models to accurately \r\nsimulate polar amplification is higher than at the time of AR5, but \r\na more complete model evaluation could be carried out if there were \r\nmore CMIP6 paleoclimate simulations included in the assessment."


id: 3005d59288c742ed1942efb3ec8e3ec8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5710
content:
"proxies and DeepMIP models show greater terrestrial warming \r\nin the high latitudes than the mid-latitudes in both hemispheres \r\n(Figure 7.13a,d). SST proxies also exhibit polar amplification in both \r\nhemispheres, but the magnitude of this polar amplification is too low \r\nin the models, in particular in the south-west Pacific (Figure 7.13g,j)."


id: 7c2a43b7eeb40dbb88f270b3b4472777
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19056
content:
"Southern Ocean SSTs have been slow to warm over the instrumental \r\nperiod, with cooling since about 1980 owing to a  combination of \r\nupper-ocean freshening from ice-shelf melt, intensification of surface \r\nwesterly winds from ozone depletion, and variability in ocean \r\nconvection (Section 9.2.1). This stands in contrast to the equilibrium \r\nwarming pattern either inferred from the proxy record or simulated \r\nby ESMs under CO2 forcing. There is high confidence that the SH high \r\nlatitudes will warm more than the tropics on centennial time scales \r\nas the climate equilibrates with radiative forcing and Southern Ocean \r\nheat uptake is reduced. However, there is only low confidence that \r\nthis feature will emerge this century."


id: 8e0ffaa3e30c51ad0572b419e62fdc2f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22188
content:
"The Last Glacial Maximum (LGM) also gives an opportunity to \r\nevaluate model simulation of polar amplification under CO2 forcing, \r\nalbeit under colder conditions than today (Kageyama et al., 2021). \r\nTerrestrial SAT and marine SST proxies exhibit clear polar amplification \r\nin the Northern Hemisphere, and the PMIP4 models capture this well \r\n(Figure  7.13c,f,i,l), particularly for SAT. There is less proxy data in \r\nthe mid- to high latitudes of the Southern Hemisphere, but here the \r\nmodels exhibit polar amplification of both SST and SAT. LGM regional \r\nmodel-data agreement is also assessed in Chapter 3 (Section 3.8.2)."


id: 7cb55ce4d0d095a573f5e8c4e506e315
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19136
content:
"Overall, the proxy reconstructions give high confidence that there was \r\npolar amplification in the LGM, MPWP and EECO, and this is further \r\nsupported by model simulations of these time periods (Figure  7.13; \r\nZhu et al., 2019a; Haywood et al., 2020; Kageyama et al., 2021; Lunt \r\net al., 2021). For both the MPWP and EECO, models are more consistent \r\nwith the temperature and CO2 proxies than at the time of AR5 (high \r\nconfidence). For the LGM Northern Hemisphere, which is the region "


id: ce9ec8632eeda21ee0671518b0befb04
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 33693
content:
"Research published since AR5 identifies changes in the tropical \r\nPacific Ocean zonal SST gradient over time as a key factor affecting \r\nhow radiative feedbacks may evolve in the future (Section 7.4.4.3). "


id: eee13a99bca12da46045e9f07b18f498
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39400
content:
"There is now a much-improved understanding of the processes that \r\ngovern the tropical Pacific SST gradient (Section 7.4.4.2.1) and the \r\npaleoclimate record provides evidence for its equilibrium changes \r\nfrom time periods associated with changes in CO2 (Section 7.4.4.2.2)."


id: 716e80d20996d03aec60379f19b8a7a1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17211
content:
"Y. Luo  et  al., 2017) which will occur as the subducting waters in \r\nmid-latitudes warm by more than the tropics on average as polar \r\namplification emerges. An individual CMIP5 ESM (GFDL's ESM2M) \r\nhas been found to exhibit a La Nina-like pattern of Pacific temperature \r\nchange through the 21st  century, similar to the SST trends seen \r\nover the historical record (Section  9.2.1 and Figure  7.14a), owing \r\nto a  weakening asymmetry between El Nino and La Nina events \r\n(Kohyama et al., 2017), but this pattern of warming may not persist \r\nto equilibrium (Paynter et al., 2018)."


id: b374404863a00783d5089eb353e4feb3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28814
content:
"In the coupled climate system, changes in atmospheric and oceanic \r\ncirculations will influence the east-west temperature gradient \r\nas well. It is expected that as global temperature increases and \r\nas  the east-west temperature gradient weakens, east-west sea \r\nlevel pressure gradients and easterly trade winds (characterizing \r\nthe Walker circulation) will weaken as well (Sections 4.5.3, 8.2.2.2 \r\nand 8.4.2.3, and Figure 7.14b; Vecchi et al., 2006, 2008). This would, \r\nin turn, weaken the east-west temperature gradient through \r\na reduction of equatorial upwelling of cold water in the east Pacific \r\nand a  reduction in the transport of warmer water to the western \r\nequatorial Pacific and Indian Ocean (England et al., 2014; Dong and \r\nMcPhaden, 2017; Li et al., 2017; Maher et al., 2018)."


id: 469fc89a052e90c90c6d7f9cdc8aecc0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9629
content:
"Research published since AR5 (Burls and Fedorov, 2014b; Fedorov \r\net  al., 2015; Erfani and Burls, 2019) has built on an earlier theory \r\n(Liu and Huang, 1997; Barreiro and Philander, 2008) linking the \r\neast-west temperature gradient to the north-south temperature \r\ngradient. In particular, model simulations suggest that a reduction in the \r\nequator-to-pole temperature gradient (polar amplification) increases \r\nthe temperature of water subducted in the extra-tropics, which in turn \r\nis upwelled in the eastern Pacific. Thus, polar amplified warming, with \r\ngreater warming in the mid-latitudes and subtropics than in the deep \r\ntropics, is expected to contribute to the weakening of the east-west \r\nequatorial Pacific SST gradient on decadal to centennial time scales."


id: 4f5a0122dd272890ccc8f114c0e3586c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11247
content:
"The transient adjustment of the equatorial Pacific SST gradient is \r\ninfluenced by upwelling waters which delay surface warming in the \r\neast since they have not been at the surface for years-to-decades to \r\nexperience the greenhouse gas forcing. This 'thermostat mechanism' \r\n(Clement et al., 1996; Cane et al., 1997) is not thought to persist to \r\nequilibrium since it does not account for the eventual increase in \r\ntemperatures of upwelled waters (Liu et al., 2005; Xie et al., 2010; "


id: 3d26ea9f182df831817d20b14be95692
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7940
content:
"The AR5 stated that paleoclimate proxies indicate a  reduction in \r\nthe longitudinal SST gradient across the equatorial Pacific during the \r\nMid-Pliocene Warm Period (MPWP; Masson-Delmotte et al., 2013; "


id: bf8b498800e22f8d9c2a5a4cfbe4242b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30961
content:
"and enhanced warming in coastal upwelling regions, suggesting \r\nthat the tropical thermocline was deeper and/or less stratified during \r\nthe Pliocene. The Pliocene data therefore suggest that the observed \r\ncooling trend over the last 60 years in parts of the eastern equatorial \r\nPacific (Section 9.2.1.1 and Figure 9.3; Seager et al., 2019), whether \r\nforced or due to internal variability, involves transient processes \r\nthat are probably distinct from the longer-time scale process (Burls \r\nand Fedorov, 2014a, b; Luo et  al., 2015; Heede et  al., 2020) that \r\nmaintained warmer eastern Pacific SST during the Pliocene."


id: bd5aa8d78f32b4c8761f57b7338d1445
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30562
content:
"see  Cross-Chapter Box  2.1 and Cross-Chapter Box  2.4 in this \r\nReport). This assessment was based on SST reconstructions \r\nbetween two sites situated very close to the equator in the heart \r\nof the western Pacific warm pool and eastern Pacific cold tongue, \r\nrespectively. Multiple SST reconstructions based on independent \r\npaleoclimate proxies generally agreed that during the Pliocene the \r\nSST gradient between these two sites was reduced compared with \r\nthe modern long-term mean (Wara et al., 2005; Dekens et al., 2008; \r\nFedorov et al., 2013)."


id: 2234bb6550dc85338ae4a8b85f62d599
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 3237
content:
"7.4.4.2.3 Overall assessment of tropical Pacific sea surface \r\ntemperature gradients under CO2 forcing"


id: 7fc3f69ae1a4fad9a5f2be87e3dd9ce1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19616
content:
"The paleoclimate proxy record and ESM simulations of the MPWP, \r\nprocess understanding, and ESM projections of climate response to \r\nCO2 forcing provide medium evidence and a medium agreement and \r\nthus medium confidence that equilibrium warming in response to \r\nelevated CO2 will be characterized by a weakening of the east-west \r\ntropical Pacific SST gradient."


id: 1bbdbdb26044556fed45ac537f8944e6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2066
content:
"Overall the observed pattern of warming over the instrumental \r\nperiod, with a  warming minimum in the eastern tropical Pacific \r\nOcean (Figure 7.14a), stands in contrast to the equilibrium warming \r\npattern either inferred from the MPWP proxy record or simulated \r\nby ESMs under CO2 forcing. There is medium confidence that the \r\nobserved strengthening of the east-west SST gradient is temporary \r\nand will transition to a weakening of the SST gradient on centennial \r\ntime scales. However, there is only low confidence that this transition \r\nwill emerge this century owing to a low degree of agreement across \r\nstudies about the factors driving the observed strengthening of \r\nthe east-west SST gradient and how those factors will evolve in \r\nthe  future. These trends in tropical Pacific SST gradients reflect \r\nchanges in the climatology, rather than changes in ENSO amplitude \r\nor variability, which are assessed in Chapter 4 (Section 4.3.3)."


id: f24b5f5fc965905e93eea9f5f149ed3e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40022
content:
"While more western Pacific warm pool temperature reconstructions \r\nare needed to refine estimates of the longitudinal gradient, several \r\nPliocene SST reconstructions from the east Pacific indicate enhanced \r\nwarming in the centre of the eastern equatorial cold tongue \r\nupwelling region (Liu et  al., 2019). This enhanced warming in the \r\neast Pacific cold tongue appears to be dynamically consistent with \r\nreconstruction of enhanced subsurface warming (Ford et al., 2015) "


id: 3d06bc69e0b0ae0091c239b127edd273
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7918
content:
"resulting in an observed increase in low-cloud cover over the tropical \r\neastern Pacific (Figure 7.14a; Zhou et al., 2016; Ceppi and Gregory, \r\n2017; Fueglistaler and Silvers, 2021). Thus, tropical low-cloud cover \r\nincreased over recent decades even as global surface temperature \r\nincreased, resulting in a  negative low-cloud feedback which is \r\nat odds with the positive low-cloud feedback expected for the \r\npattern of equilibrium warming under CO2 forcing (Section 7.4.2.4 \r\nand Figure 7.14b)."


id: 517e7b6a74224255de4877f423ee8a23
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11614
content:
"The spatial pattern of SST changes since 1870 shows relatively \r\nlittle warming in key regions of less-negative radiative feedbacks, \r\nincluding the eastern tropical Pacific Ocean and Southern Ocean \r\n(Sections 7.4.4.1 and 7.4.4.2, and Figures 2.11b and 7.14a). Cooling \r\nin these regions since 1980 has occurred along with an increase in \r\nthe strength of the capping inversion in tropical descent regions, "


id: bc154aa40276b46e2e484b602dd7e377
created_at: 2023-04-19 13:21:37
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vector_id: 30328
content:
"While there are not yet direct observational constraints on the \r\nmagnitude of the pattern effect, satellite measurements of variations \r\nin TOA radiative fluxes show strong co-variation with changing \r\npatterns of SSTs, with a  strong dependence on SST changes in \r\nregions of deep convective ascent (e.g., in the western Pacific warm \r\npool; Loeb et al., 2018a; Fueglistaler, 2019). Cloud and TOA radiation \r\nresponses to observed warming patterns in atmospheric models have \r\nbeen found to compare favourably with those observed by satellite \r\n(Section 7.2.2.1 and Figure 7.3; Zhou et al., 2016; Loeb et al., 2020). \r\nThis observational and modelling evidence indicates the potential for \r\na  strong pattern effect in nature that will only be negligible if the \r\nobserved pattern of warming since pre-industrial levels persists to "


id: b4554be73a5bad99b885b0ee6e65ac3b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28962
content:
"more distinct from the equilibrium warming pattern expected under \r\nCO2 forcing (high confidence) (similar to CMIP6 projections shown in \r\nFigure 7.12a; Andrews et al., 2018)."


id: 70237e25ff9566718c964aa802da201c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 16980
content:
"Equilibrium climate sensitivity (ECS) and transient climate response \r\n(TCR) are metrics of the global surface air temperature (GSAT) \r\nresponse to forcing, as defined in Box  7.1. ECS is the magnitude \r\nof the long-term GSAT increase in response to a  doubling of \r\natmospheric CO2 concentration after the planetary energy budget is \r\nbalanced, though leaving out feedbacks associated with ice sheets; \r\nwhereas the TCR is the magnitude of GSAT increase at year 70 when \r\nCO2 concentration is doubled in a 1% yr-1 increase scenario. Both \r\nare idealized quantities, but can be inferred from paleoclimate or \r\nobservational records or estimated directly using climate simulations, \r\nand are strongly correlated with the climate response in realistic \r\nfuture projections (Sections 4.3.4 and 7.5.7; Grose et al., 2018)."


id: 9cf22c0b709b33f1aed389592406aead
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 24846
content:
"TCR is always smaller than ECS because ocean heat uptake acts to \r\nreduce the rate of surface warming. Yet, TCR is related to ECS across \r\nCMIP5 and CMIP6 models (Grose et al., 2018; Flynn and Mauritsen, \r\n2020) as expected since TCR and ECS are inherently measures \r\nof climate response to forcing; both depend on effective radiative \r\nforcing (ERF) and the net feedback parameter, a. The relationship \r\nbetween TCR and ECS is, however, non-linear and becomes more so "


id: 485d808968b52cf2855e3833827469b8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9944
content:
"by aggregating estimates of individual climate feedbacks based not \r\nonly on ESMs but also on theory, observations, and high-resolution \r\nprocess modelling (Section 7.4.2)."


id: d33e8a8ec74951151a60e93d2c0779f7
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34509
content:
"for higher ECS values (Hansen et al., 1985; Knutti et al., 2005; Millar \r\net  al., 2015; Flynn and Mauritsen, 2020; Tsutsui, 2020) owing to \r\nocean heat uptake processes and surface temperature pattern effects \r\ntemporarily reducing the rate of surface warming. When a is small \r\nin magnitude, and correspondingly ECS is large (recall that ECS is \r\ninversely proportional to a), these temporary effects are increasingly \r\nimportant in reducing the ratio of TCR to ECS."


id: ec6866a3f9fca44b978df28dae5ea108
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38951
content:
"The effective radiative forcing of CO2 doubling is assessed to be \r\nDF2xCO2 = 3.93 +- 0.47 W m-2 (Section 7.3.2.1), while the net feedback \r\nparameter is assessed to be a = -1.16 +- 0.40 W m-2 degC-1 (Table 7.10), \r\nwhere the ranges indicate one standard deviation. These values are \r\nslightly different from those directly calculated from ESMs because \r\nmore information is used to assess them, as explained above. Assuming \r\nDF2xCO2 and a each follow an independent normal distribution, the \r\nuncertainty range of ECS can be obtained by substituting the respective \r\nprobability density function into the expression of ECS (red curved bar \r\nin Figure 7.16). Since a is in the denominator, the normal distribution \r\nleads to a long tail in ECS towards high values, indicating the large \r\neffect of uncertainty in a in estimating the likelihood of a high ECS \r\n(Roe and Baker, 2007; Knutti and Hegerl, 2008)."


id: 11dab17097fa3afc30f9ef5cfefbabc6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 336
content:
"This section assesses the estimates of ECS and TCR based on process \r\nunderstanding of the ERF due to a  doubling of CO2 concentration \r\nand the net climate feedback (Sections 7.3.2 and 7.4.2). This \r\nprocess-based assessment is made in Section 7.5.1.1 and applied to \r\nTCR in Section 7.5.1.2."


id: 4f21e3e24970fc4d7e4dddf27aa6be21
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11207
content:
"The process-based assessment is based on the global energy budget \r\nequation (Box 7.1, Equation 7.1), where the ERF (DF) is set equal to \r\nthe effective radiative forcing due to a doubling of CO2 concentration \r\n(denoted as DF2xCO2) and the climate state reaches a new equilibrium, \r\nthat is, Earth's energy imbalance averages to zero (DN = 0). ECS is \r\ncalculated as the ratio between the ERF and the net feedback \r\nparameter: ECS = -DF2xCO2/a. Estimates of DF2xCO2 and a are obtained \r\nseparately based on understanding of the key processes that \r\ndetermine each of these quantities. Specifically, DF2xCO2 is estimated \r\nbased on instantaneous radiative forcing that can be accurately \r\nobtained using line-by-line calculations, to which uncertainty due \r\nto adjustments are added (Section 7.3.2). The range of a is derived "


id: 67d9e4497fd748208a2a8362447a1a8c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15545
content:
"dependence of radiative feedbacks and heat uptake on the evolving SST \r\npattern under CO2 forcing alone (Section 7.4.4). In the real world, natural \r\ninternal variability and aerosol radiative forcing also affect the efficacy \r\nparameter, but these effects are excluded for the current discussion."


id: e9fa2cc96b3f02355aa6bc9dcaa03578
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38516
content:
"In summary, the ECS based on the assessed values of DF2xCO2 and a is \r\nassessed to have a median value of 3.4degC with a likely range of 2.5 to \r\n5.1 degC and very likely range of 2.1 to 7.7 degC. To this assessed range of \r\nECS, the contribution of uncertainty in a is approximately three times \r\nas large as the contribution of uncertainty in DF2xCO2."


id: be09616c202bbbd62300f17dade755a1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30700
content:
"ECS estimated using the ERF due to a doubling of CO2 concentration \r\nand the net feedback parameter (ECS = -DF2xCO2/a) can be translated \r\ninto the TCR so that both climate sensitivity metrics provide consistent \r\ninformation about the climate response to forcing. Here a two-layer \r\nenergy budget emulator is used to transfer the process-based \r\nassessment of forcing, feedback, efficacy and heat uptake to TCR \r\n(Supplementary Material 7.SM.2.1 and Cross-Chapter Box 7.1). The \r\nemulator can reproduce the transient surface temperature evolution in \r\nESMs under 1pctCO2 simulations and other climate change scenarios, \r\ndespite the very low number of degrees of freedom (Held et al., 2010; \r\nGeoffroy et al., 2012, 2013a; Palmer et al., 2018). Using this model \r\nwith parameters given from assessments in Sections 7.2, 7.3, and 7.4, \r\nTCR is assessed based on the process-based understanding."


id: e4fd0e1e5645bf65d7ffc2520bb3490d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37581
content:
"temperature record (Section 7.5.2.2), and internal variability in global \r\ntemperature and TOA radiation (Section  7.5.2.3). Section  7.5.2.4 \r\nprovides an overall assessment of TCR and ECS based on these lines \r\nof evidence from the instrumental record."


id: 6bf4c5f73f9877d6d2b2fe09dbebc990
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 16294
content:
"k = 0.84 +- 0.38 W m-2 degC-1 (one standard deviation) by ignoring their \r\ncovariance (the mean value is very similar to that used for Box 4.1, \r\nFigure  1; see Supplementary Material 7.SM.2.1). By incorporating \r\nthis inter-model spread in k, the range of TCR is widened by about \r\n10% (blue bar in Figure 7.17b). Yet, the dominant contribution to the \r\nuncertainty range of TCR arises from the net feedback parameter a, \r\nconsistent with analyses of CMIP6 models (Williams et  al., 2020), \r\nand this assessment remains unchanged from AR5 stating that \r\nuncertainty in ocean heat uptake is of secondary importance."


id: aa67c5070f4c6520431255bb92a916e6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27210
content:
"In summary, the process-based estimate of TCR is assessed to have \r\nthe central value of 2.0degC with the likely range from 1.6 to 2.7 degC and \r\nthe very likely range from 1.3 to 3.1 degC (high confidence). The upper \r\nbound of the assessed range was slightly reduced from AR5 but can \r\nbe further constrained using multiple lines of evidence (Section 7.5.5)."


id: ff6bf15da2e7e464b15d4969df6b360
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 42337
content:
"This section assesses the estimates of ECS and TCR based on the \r\ninstrumental record of climate change and variability with an \r\nemphasis on new evidence since AR5. Several lines of evidence \r\nare assessed including the global energy budget (Section  7.5.2.1), \r\nthe use of simple climate models evaluated against the historical "


id: 4cdc1695eada03145a381bc749c1b540
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10795
content:
"Energy budget estimates of TCR and ECS assessed here are based \r\non improved observations and understanding of global surface \r\ntemperature trends extended to the year 2020 (Section  2.3.1), \r\nrevised estimates of Earth's energy imbalance (Section  7.2), and \r\nrevised estimates of ERF (Section  7.3). Accurate, in situ-based \r\nestimates of Earth's energy imbalance can be made from around \r\n2006 based on near-global ocean temperature observations \r\nfrom the ARGO array of autonomous profiling floats (Sections 2.3 \r\nand 7.2). Over the period 2006-2018 the Earth's energy imbalance \r\nis estimated to be 0.79 +- 0.27 W m-2 (Section 7.2) and it is assumed \r\nthat this value is also representative for the period 2006-2019. \r\nAnomalies are taken with respect to the baseline period 1850-1900, \r\nalthough other baselines could be chosen to avoid major volcanic \r\nactivity (Otto et al., 2013; Lewis and Curry, 2018). Several lines of \r\nevidence, including ESM simulations (Lewis and Curry, 2015), energy "


id: 3a77f1b8a7b42a09a3bc2fb9d59ad0f3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 7486
content:
"The traditional energy budget framework has been evaluated within \r\nESM simulations by comparing the effective ECS estimated under \r\nhistorical forcing with the ECS estimated using regression methods \r\n(Box 7.1) under abrupt4xCO2 (Andrews et al., 2019; Winton et al., \r\n2020). For one CMIP6 model (GFDL-CM4.0), the value of effective \r\nECS derived from historical energy budget constraints is 1.8degC while \r\nECS is estimated to be 5.0degC (Winton et al., 2020). For another model "


id: 9bfcfc577fb4d45b0f021b79b012070d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 24695
content:
"The values of ECS obtained from the techniques outlined above \r\nare all higher than those estimated from both AR5 and recently \r\npublished estimates (M. Collins et al., 2013; Otto et al., 2013; Lewis \r\nand Curry, 2015, 2018; Forster, 2016). Four revisions made in this \r\nReport are responsible for this increase: (i) an upwards revision of \r\nhistoric global surface temperature trends from newly published \r\ntrend estimates (Section  2.3.1); (ii) an 8% increase in the ERF for \r\nDF2xCO2 (Section  7.3.2); (iii) a  more negative central estimate of \r\naerosol ERF, which acts to reduce estimates of historical ERF trends; \r\nand (iv) accounting for the pattern effect in ECS estimates. Values of \r\nECS provided here are similar to those based on the historical energy \r\nbudget found in Sherwood et al. (2020), with small differences owing \r\nto methodological differences and the use of different estimates of \r\nobserved warming, Earth's energy imbalance, and ERF."


id: f1f0fab99df8c1a609e9ad13ac58e465
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39953
content:
"ERF, ECS and TCR from across the report. Therefore, the fact that the \r\nemulator effective ECS values estimated from previous studies tend to \r\nlie at the lower end of the range inferred from historical global energy \r\nbudget constraints may reflect that the energy budget constraints in \r\nSection 7.5.2.1 use updated estimates of Earth's energy imbalance, \r\nGSAT trends and ERF, rather than any methodological differences \r\nbetween the lines of evidence. The 'emergent constraints' on ECS \r\nbased on observations of climate variability used in conjunction with \r\ncomprehensive ESMs are assessed in Section 7.5.4.1."


id: 1a908df193b59c278068dbd2a2628ed0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1875
content:
"The median estimates of TCR and effective ECS inferred from emulator \r\nstudies generally lie within the 5-95% ranges of those inferred from \r\nhistorical global energy budget constraints (1.3 to 2.7 degC for TCR and \r\n1.6 to 4.8 degC for effective ECS). Their estimates would be consistent \r\nwith still-higher values of ECS when accounting for changes in \r\nradiative feedbacks as the spatial pattern of global warming evolves \r\nin the future (Section 7.5.2.1). Cross-Chapter Box 7.1 and references \r\ntherein show that four very different physically based emulators can \r\nbe calibrated to match the assessed ranges of historical GSAT change, "


id: d9d516320363de7cb8e3981ffa107e63
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35623
content:
"constraints on the upper bound of ECS, while the studies assessed in \r\nSection 7.5.2.3 based on climate variability provide low confidence\r\nin its value owing to limited evidence."


id: 73875e9aa58f38054a0265a50bb9f473
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17579
content:
"Finding such correlations within models requires simulations that \r\nspan multiple centuries, suggesting that the satellite record may \r\nnot be of sufficient length to produce robust feedback estimates. \r\nHowever, correlations between regression-based feedbacks and \r\nlong-term feedbacks have been found to be higher when focused on \r\nspecific processes or regions, such as for the cloud- or water-vapour \r\nfeedbacks (Section 7.4.2; Dessler, 2013; Zhou et al., 2015). Assessing \r\nthe global radiative feedback in terms of the more stable relationship \r\nbetween tropospheric temperature and TOA radiation offers another \r\npotential avenue for constraining ECS. The 'emergent constraints' \r\non ECS based on variability in the TOA energy budget are assessed \r\nin Section 7.5.4.1."


id: c572835a869d41cbacf9ca90b6bfd6e8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32047
content:
"Global energy budget constraints indicate a central estimate (median) \r\nTCR value of 1.9degC and that TCR is likely in the range 1.5 to 2.3 degC and \r\nvery likely in the range 1.3 to 2.7 degC (high confidence). Studies that \r\nconstrain TCR based on the instrumental temperature record used in \r\nconjunction with ESM simulations are summarized in Section 7.5.4.3."


id: 8561b0a157839adf4758ea5da65561cc
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 20602
content:
"AR5 stated that data and modelling of the Last Glacial Maximum \r\n(LGM; Cross-Chapter Box 2.1) indicated that it was very unlikely that \r\nECS lay outside the range 1degC-6degC (Masson-Delmotte et al., 2013). \r\nFurthermore, AR5 reported that climate records of the last 65 million \r\nyears indicated an ECS 95% confidence interval of 1.1 to 7.0 degC."


id: 2f44609c20da60ccc93b39611a857b13
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5583
content:
"Compared with AR5, there are now improved constraints on estimates \r\nof ECS from paleoclimate evidence. The strengthened understanding \r\nand improved lines of evidence come in part from the use of \r\nhigh-resolution paleoclimate data across multiple glacial-interglacial \r\ncycles, taking into account state-dependence (Section  7.4.3; von \r\nder Heydt et  al., 2014; Kohler et  al., 2015, 2017, 2018; Friedrich \r\net al., 2016; Snyder, 2019; Stap et al., 2019) and better constrained \r\npre-ice-core estimates of atmospheric CO2 concentrations (Martinez\u0002Boti et al., 2015; Anagnostou et al., 2016, 2020; de la Vega et al., \r\n2020) and surface temperature (Hollis et al., 2019; Inglis et al., 2020; \r\nMcClymont et al., 2020)."


id: a5c3e7dab05450252f117510a99570f4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26388
content:
"and emergent constraints on paleoclimate model simulations. This \r\nsection focuses on the first type only; the second type (emergent \r\nconstraints) are discussed in Section 7.5.4."


id: 89e40a266c681b7dc6b34e476ea69e1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 21430
content:
"In order to provide estimates of ECS, evidence from the paleoclimate \r\nrecord can be used to estimate forcing (DF) and global surface \r\ntemperature response (DT) in Equation 7.1, Box  7.1, under the \r\nassumption that the system is in equilibrium (i.e., DN = 0). However, \r\nthere are complicating factors when using the paleoclimate record \r\nin this way, and these challenges and uncertainties are somewhat \r\nspecific to the time period being considered."


id: 488cc681cb5c5380ce2e830fc9bcf7a4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9977
content:
"Since AR5, several studies have extended the Rohling et  al. \r\n(2012) approach (described above for the LGM) to the glacial-\r\ninterglacial cycles of the last approximately 1 to 2 million years "


id: ba6c035baaedfe0941c2747f1b583d8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30018
content:
"Further back in time, in the Early Eocene (Cross-Chapter Box  2.1), \r\nuncertainties in forcing and temperature change become larger, but \r\nthe signals are generally larger too (Anagnostou et al., 2016, 2020; "


id: e3a07cfc7c7c791181f9e45e4f8727bf
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37338
content:
"Shaffer et al., 2016; Inglis et al., 2020). Caution must be applied when \r\nestimating ECS from these time periods, due to differing continental \r\nposition and topography/bathymetry (Farnsworth et  al., 2019), \r\nand due to temperature-dependence of feedbacks (Section  7.4.3). \r\nOn even longer time scales of the last 500 million years (Royer, 2016) \r\nthe temperature and CO2 measurements are generally asynchronous, \r\npresenting challenges in using this information for assessments \r\nof ECS."


id: 7aa70ff6873cd55a1a4e07cc8f967a27
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18776
content:
"The lines of evidence directly constraining ECS from paleoclimates \r\nare summarized in Table  7.11. Although some of the estimates \r\nin Table  7.11 are not independent because they use similar proxy \r\nrecords to each other (e.g., von der Heydt et al., 2014; Kohler et al., \r\n2015, 2017; Stap et al., 2019), there are still multiple independent "


id: 3a4dd91e350dc7fca261c908d92c4532
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7464
content:
"Table 7.11 | Estimates of equilibrium climate sensitivity (ECS) derived from paleoclimates; from AR5 (above double lines) and from post-AR5 studies \r\n(below double lines). Many studies provide an estimate of ECS that includes only CO2 and the ice-sheet feedback as forcings, providing an estimate of S[CO2, LI] using the \r\nnotation of Rohling et al. (2012), which is equivalent to our definition of ECS (Box 7.1). However, some studies provide estimates of other types of sensitivity (column 4). Different \r\nstudies (column 1) focus on different time periods (column 2) and use a variety of different paleoclimate proxies and models (column 3) to give a best estimate (column 5) and/or \r\na range (column 5). The published ranges given account for varying sources of uncertainty (column 6). See Cross-Chapter Box 2.1 for definition of time periods. All temperature \r\nvalues in column 5 are shown to a precision of 1 decimal place."


id: 4cdd2a593c9d12ff3b575775b0cca192
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10797
content:
"a Sa\r\n in this table denotes a classification of climate sensitivity following Rohling et al. (2012). "


id: 1a10ba2729b575cd4f56259f273eea46
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1787
content:
"b\r\n Although our assessed value of ERF due to CO2 doubling is 3.93 W m-2 (Section 7.3.2.1), for these studies the best estimate and range of temperature is calculated from the \r\npublished estimate of sensitivity in units of degC (W m-2)\r\n-1 using an ERF of 3.7 W m-2, for consistency with the typical value used in the studies to estimate the paleo CO2 forcing."


id: d0dd86f45210eb47f2937fccb36cee42
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34094
content:
"None of the post-AR5 studies in Table 7.11 have an estimated lower \r\nrange for ECS below 1.6degC. As such, based solely on the paleoclimate \r\nrecord, it is assessed to be very likely that ECS is greater than 1.5degC \r\n(high confidence)."


id: 92f5bc16d773f070758bbcbdb4baef77
created_at: 2023-04-19 13:21:37
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vector_id: 23070
content:
"from warmer paleoclimates (Section  7.4.3.2). A  central estimate \r\nof  ECS, derived from the LGM (Section  7.5.3.1) and warm periods \r\nof the pre-Quaternary (Section  7.5.3.3), that takes into account \r\nsome of the interdependencies between the different studies, can be \r\nobtained by averaging across studies within each of these two time \r\nperiods, and then averaging across the two time periods; this results \r\nin a central estimate of 3.4degC. This approach of focussing on the LGM \r\nand warm climates was also taken by Sherwood et al. (2020) in their \r\nassessment of ECS from paleoclimates. An alternative method is to \r\naverage across all studies, from all periods, that have considered \r\nmultiple sources of uncertainty (Table  7.11); this approach leads \r\nto a  similar central estimate of 3.3degC. Overall, we assess medium \r\nconfidence for a central estimate of 3.3degC to 3.4degC."


id: 2090febc649431ee3f00a607444ee173
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2955
content:
"In general, it is the studies based on the warm periods of the \r\nglacial-interglacial cycles (Section 7.5.3.2) that give the largest values \r\nof ECS. Given the large uncertainties associated with estimating \r\nthe magnitude of the ice-sheet forcing during these intervals (Stap \r\net  al., 2019), and other uncertainties discussed in Section  7.5.3.2, \r\nin particular the direct effect of orbital forcing on estimates of ECS, \r\nthere is only low confidence in estimates from the studies based on \r\nglacial-interglacial periods. This low confidence also results from the \r\ntemperature-dependence of the net feedback parameter, a, resulting \r\nfrom several of these studies (Figure 7.10), that is hard to reconcile \r\nwith the other lines of evidence for a, including proxy estimates "


id: 27010f313ce8139056eb025800b1195b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4025
content:
"There is more variation in the upper bounds of ECS than in the lower \r\nbounds. Estimates of ECS from pre-Quaternary warm periods have an "


id: 7b661def1fa5aa0ba8635f9d8dc8766c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18910
content:
"average upper range of 4.9degC, and from the LGM of 4.4degC; taking \r\ninto account the independence of the estimates from these two time \r\nperiods, and accounting for state-dependence (Section  7.4.3) and \r\nother uncertainties discussed in Section 7.5.3, the paleoclimate record \r\non its own indicates that ECS is likely less than 4.5degC. Given the higher \r\nvalues from many glacial-interglacial studies, this value has only \r\nmedium confidence. Despite the large variation in individual studies \r\nat the extreme upper end, all except two studies (both of which are \r\nfrom glacial-interglacial time periods associated with low confidence) \r\nhave central estimates that are below 6degC; overall we assess that it is \r\nextremely likely that ECS is below 8degC (high confidence)."


id: c7084a65fbda21df4520a23c3762e1f1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32330
content:
"ESMs exhibit substantial spread in ECS and TCR (Section  7.5.7). \r\nNumerous studies have leveraged this spread in order to narrow \r\nestimates of Earth's climate sensitivity by employing methods known \r\nas 'emergent constraints' (Section  1.5.4). These methods establish \r\na relationship between an observable and either ECS or TCR based \r\non an ensemble of models, and combine this information with \r\nobservations to constrain the probability distribution of ECS or TCR. \r\nMost studies of this kind have clearly benefitted from the international \r\nefforts to coordinate the CMIP and other multi-model ensembles."


id: aad0d32c8e89cbe8c03fc32e2bff9126
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27279
content:
"Perhaps the simplest class of emergent constraints regress past \r\nequilibrium paleoclimate temperature change against modelled ECS \r\nto obtain a relationship that can be used to translate a past climate \r\nchange to ECS. The advantage is that these are constraints on "


id: e8f7c0d3ffa404b334373fbec0303abe
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38339
content:
"changed less over the 1970-2005 period, potentially leading to \r\nhigh-biased results (Jimenez-de-la-Cuesta and Mauritsen, 2019), \r\nwhereas during the later period 1975-2019 these anomalies roughly \r\ncancel (Nijsse et al., 2020). Pattern effects may have been substantial \r\nover these periods (Andrews et  al., 2018), however the extent to \r\nwhich TOA radiation anomalies influenced surface temperature may \r\nhave been dampened by the deep ocean (Hedemann et  al., 2017; \r\nNewsom et al., 2020). It is therefore deemed more likely than not that \r\nthese estimates based on post-1970s global warming are biased low \r\nby internal variability."


id: ef3efac23b76ebdaa354e298253d9984
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39463
content:
"a  range of models consistent with observations (those with ECS \r\nvalues between 2.0degC and 3.9degC; Dessler et al., 2018) or as a formal \r\nemergent constraint by deriving further model-based relationships \r\nto yield a median of 3.3 [2.4 to 4.5] degC (Dessler and Forster, 2018). \r\nThere are major challenges associated with short-term variability \r\nin the energy budget, in particular how it relates to the long-term \r\nforced response of clouds (Colman and Hanson, 2017; Lutsko and \r\nTakahashi, 2018). Variations in the surface temperature that are not \r\ndirectly affecting the radiation balance lead to an overestimated \r\nECS when using linear regression techniques where it appears as \r\nnoise in the independent variable (Proistosescu et al., 2018; Gregory \r\net  al., 2020). The latter issue is largely overcome when using the \r\ntropospheric mean or mid-tropospheric temperature (Trenberth et al., \r\n2015; Dessler et al., 2018)."


id: 2c7fd35d9f2ae878999640ab33c52558
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5095
content:
"A study that developed an emergent constraint based on the response \r\nto the Mount Pinatubo 1991 eruption yielded a  best estimate of \r\n2.4 [likely range 1.7 to 4.1] degC (Bender et al., 2010). When accounting \r\nfor ENSO variations they found a somewhat higher best estimate of \r\n2.7degC, which is in line with results of later studies that suggest ECS \r\ninferred from periods with substantial volcanic activity are low-biased \r\ndue to strong pattern effects (Gregory et  al., 2020) and that the \r\nshort-term nature of volcanic forcing could exacerbate possible \r\nunderestimates of modelled pattern effects."


id: 1137b1efc3bad443729a66be623b098c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 224
content:
"The fidelity of models in reproducing aspects of temperature variability \r\nor the radiation budget has also been proposed as emergent constraints \r\non ECS (Covey et al., 2000; Knutti et al., 2006; Huber et al., 2010; Bender \r\net al., 2012; Brown and Caldeira, 2017; Siler et al., 2018a). Here indices \r\nbased on spatial or seasonal variability are linked to modelled ECS, \r\nand overall the group of emergent constraints yields best estimates \r\nof 3.3degC-3.7degC. Nevertheless, the physical relevance of present-day \r\nbiases to the sum of long-term climate change feedbacks is unclear \r\nand therefore these constraints on ECS are not considered reliable."


id: 79e36c8f04e363fe90bcfdbf402203f5
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18648
content:
"present-day climate biases. The former class is arguably superior in \r\nrepresenting ECS, since it is a global surface temperature or energy \r\nbudget change, whereas the latter class is perhaps best thought of as \r\nproviding constraints on individual climate feedbacks, for example, the \r\ndetermination that low-level cloud feedbacks are positive. The latter \r\nresult is consistent with and confirms process-based estimates of \r\nlow-cloud feedbacks (Section 7.4.2.4), but are potentially biased as \r\na group by missing or biased feedbacks in ESMs and is accordingly \r\nnot taken into account here. A  limiting case here is Dessler and \r\nForster (2018) which is focused on monthly co-variability in the \r\nglobal TOA energy budget with mid-tropospheric temperature, at \r\nwhich time scale the surface-albedo feedback is unlikely to operate, \r\nthus implicitly assuming it is unbiased in the model ensemble."


id: bd4c5294cbea280d7e298dcd92e96c28
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30551
content:
"Substantial quantitative progress has been made in interpreting \r\nevidence of Earth's climate sensitivity since AR5, through innovation, \r\nscrutiny, theoretical advances and a rapidly evolving data base from \r\ncurrent, recent and paleo climates. It should be noted that, unlike AR5 \r\nand earlier reports, our assessment of ECS is not directly informed by \r\nESM simulations (Section 7.5.6). The assessments of ECS and TCR are \r\nfocussed on the following lines of evidence: process-understanding; \r\nthe instrumental record of warming; paleoclimate evidence; and \r\nemergent constraints. ESMs remain essential tools for establishing \r\nthese lines of evidence, for instance, in estimating part of the feedback \r\nparameters and radiative forcings, and emergent constraints rely on \r\nsubstantial model spread in ECS and TCR (Section 7.5.6)."


id: fbb798dc563fa9acdc2d6560f855f3f3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41656
content:
"Emergent constraints on TCR with a  focus on the instrumental \r\ntemperature record, though less abundant, have also been proposed. \r\nThese can be influenced by internal variability and pattern effects, as \r\ndiscussed in Section 7.5.4.1, although the influence is smaller because \r\nuncertainty in forced pattern effects correlates between transient \r\nhistorical warming and TCR. In the simplest form Gillett et al. (2012) \r\nregressed the response of one model to individual historical forcing \r\ncomponents to obtain a tight range of 1.3degC-1.8degC, but later when an \r\nensemble of models was used the range was widened to 0.9degC-2.3degC "


id: 65d9952391edc0dd50429cb14147a7a9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15180
content:
"A key advance over the AR5 assessment is the broad agreement across \r\nmultiple lines of evidence. These support a  central estimate of ECS \r\nclose to, or at least not inconsistent with, 3degC. This advance is foremost \r\nfollowing improvements in the understanding and quantification of \r\nEarth's energy imbalance, the instrumental record of global temperature \r\nchange, and the strength of anthropogenic radiative forcing. Further "


id: c0fc6587080ced5ed38e1b8f5c9df913
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31258
content:
"Table 7.12 | Emergent constraint studies used in the assessment of equilibrium climate sensitivity (ECS). These are studies that rely on global or near-global \r\ntemperature change as the observable."


id: 83dad824fd36c481f8589cf33479df4d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20341
content:
"advances include increased understanding of how the pattern effect \r\ninfluences ECS inferred from historical global warming (Sections 7.4.4 \r\nand 7.5.3), improved quantification of paleo climatechange from proxy \r\nevidence and a deepened understanding of how feedback mechanisms \r\nincrease ECS in warmer climate states (Sections 7.4.3, 7.4.4 and 7.5.4), \r\nand also an improved quantification of individual cloud feedbacks \r\n(Sections 7.4.2 and 7.5.4.2). The assessment findings for ECS and TCR \r\nare summarized in Table 7.13 and Table 7.14, respectively, and also \r\nvisualized in Figure 7.18."


id: 598d804b4fb0a40c11ddf238604d0f53
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12990
content:
"There has long been a consensus (Charney et al., 1979) supporting an \r\nECS estimate of 1.5degC-4.5degC. In this regard it is worth remembering \r\nthe many debates challenging an ECS of this magnitude. These started \r\nas early as Angstrom (1900) criticizing the results of Arrhenius (1896) "


id: 9a68ce62d1012cd86f7e8a0d94512e49
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 24409
content:
"The evidence for TCR is less abundant than for ECS, and focuses \r\non the instrumental temperature record (Sections 7.5.2 and 7.5.6), \r\nemergent constraints (Section  7.5.4.3) and process understanding \r\n(Section  7.5.1). The AR5 assessed a  likely range for TCR of 1.0  to \r\n2.5  degC. TCR and ECS are related, though, and in any case TCR is "


id: 3d5409fde2b55055755caa396436abd8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 7968
content:
"The primary consideration that led to excluding ECS and TCR \r\ndirectly derived from ESMs is that information from these models \r\nis incorporated in the lines of evidence used in the assessment: \r\nESMs are partly used to estimate historical and paleoclimate ERFs \r\n(Sections 7.5.2 and 7.5.3); to convert from local to global mean paleo \r\ntemperatures (Section 7.5.3); to estimate how feedbacks change with \r\nSST patterns (Section 7.4.4.3); and to establish emergent constraints \r\non ECS (Section 7.5.4). They are also used as important evidence in the \r\nprocess understanding estimates of the temperature, water vapour, \r\nalbedo, biogeophysical, and non-CO2 biogeochemical feedbacks, \r\nwhereas other evidence is primarily used for cloud feedbacks where \r\nthe climate model evidence is weak (Section 7.4.2). One perspective \r\non this is that the process understanding line of evidence builds on \r\nand replaces ESM estimates."


id: 74dd49d22824b00a9d56c7ee9529aa4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 17796
content:
"As a  result of the above considerations, in this Report projections \r\nof global surface temperature are produced using climate model \r\nemulators that are constrained by the assessments of ECS, TCR and \r\nERF. In reports up to and including AR5, ESM values of ECS did not fully \r\nencompass the assessed very likely range of ECS, raising the possibility \r\nthat past multi-model ensembles underestimated the  uncertainty in \r\nclimate change projections that existed at the times of those reports \r\n(e.g., Knutti, 2010). However, due to an increase in the modelled ECS "


id: edd4acb0b41cf3abb5b7beecdb39d205
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39202
content:
"spread and a decrease in the assessed ECS spread based on improved \r\nknowledge in multiple lines of evidence, the CMIP6 ensemble \r\nencompasses the very likely range of ECS [2 to 5]  degC assessed in \r\nSection 7.5.5. Models outside of this range are useful for establishing \r\nemergent constraints on ECS and TCR and provide useful examples of \r\n'tail risk' (Sutton, 2018), producing dynamically consistent realizations \r\nof future climate change to inform impact studies and risk assessments."


id: d450be3c35b5bfdc46811fe5aad4af23
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34678
content:
"both CMIP5 and that assessed based on multiple lines of evidence \r\n(Sections 4.3.1 and 4.3.4, and FAQ 7.3)."


id: 86d3041099f1c8219b7d01b353cc7dc8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20886
content:
"While the magnitude of global warming by the end of the 21st century \r\nis dominated by future GHG emissions, the uncertainty in warming for \r\na given ERF change is dominated by the uncertainty in ECS and TCR \r\n(Section  4.3.4). The proportion of variation explained by ECS and \r\nTCR varies with scenario and the time period considered, but within \r\nCMIP5 models around 60-90% of the globally averaged projected \r\nsurface warming range in 2100 can be explained by the model range \r\nof these metrics (Grose et  al., 2018). Uncertainty in the long-term \r\nglobal surface temperature change can further be understood in \r\nterms of the processes affecting the global TOA energy budget, \r\nnamely the ERF, the radiative feedbacks which govern the efficiency of \r\nradiative energy loss to space with surface warming, and the increase \r\nin the global energy inventory (dominated by ocean heat uptake) \r\nwhich reduces the transient surface warming. A  variety of studies "


id: e1734519de1d6d7883a00592f77ca099
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36934
content:
"In summary, the distribution of CMIP6 models have higher average \r\nECS and TCR values than the CMIP5 generation of models and \r\nthe assessed values of ECS and TCR in Section  7.5.5. The high \r\nECS and TCR values can in some CMIP6 models be traced to \r\nimproved representation of extratropical cloud feedbacks (medium \r\nconfidence). The ranges of ECS and TCR from the CMIP6 models are \r\nnot considered  robust samples of possible values and the models \r\nare not considered a  separate line of evidence for ECS and TCR. \r\nSolely based on its ECS or TCR values an individual ESM cannot be \r\nruled out as implausible, though some models with high (greater \r\nthan 5degC) and low (less than 2degC) ECS are less consistent with past \r\nclimate change (high confidence). High climate sensitivity in models \r\nleads to generally higher projected warming in CMIP6 compared to "


id: 2e17768bb372e20d6044b6c19f7fe4ae
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 5383
content:
"at depth away from the ocean surface.  Section  7.4.4.1 shows the \r\nwarming contributions from these factors at the regional scale."


id: c96a733f5b5a8a82f22240e919d69711
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32763
content:
"Differences in projected transient global warming across ESMs are \r\ndominated by differences in their radiative feedbacks, while differences \r\nin ocean heat uptake and radiative forcing play secondary roles \r\n(Figure 7.20b; Vial et al., 2013). The uncertainty in projected global \r\nsurface temperature change associated with inter-model differences \r\nin cloud feedbacks is the largest source of uncertainty in CMIP5 and \r\nCMIP6 models (Figure  7.20b), just as they were for CMIP3 models \r\n(Dufresne and Bony, 2008). Extending this energy budget analysis to \r\nequilibrium surface warming suggests that about 70% of the inter\u0002model differences in ECS arises from uncertainty in cloud feedbacks, \r\nwith the largest contribution to that spread coming from shortwave \r\nlow-cloud feedbacks (Vial et al., 2013; Zelinka et al., 2020)."


id: 69a4a7d498f3f323de6704b891b319f4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15854
content:
"vertical coordinate systems, among other differences); TCR and ECS \r\nchanged by 0.4degC and 1.4degC, respectively, when the atmospheric \r\nmodel component was changed, while TCR and ECS changed by \r\n0.3degC and less than 0.05degC, respectively, when the oceanic model \r\ncomponent was changed. By perturbing ocean vertical diffusivities \r\nover a wide range, Watanabe et al. (2020) found that TCR changed by \r\n0.16degC within the model MIROC5.2 while Krasting et al. (2018) found \r\nthat ECS changed by about 0.6degC within the model GFDL-ESM2G, \r\nwith this difference linked to different radiative feedbacks associated \r\nwith different spatial patterns of sea surface warming (Section 7.4.4.3). \r\nBy comparing simulations of CMIP6 models with and without the \r\neffects of CO2 on vegetation, Zarakas et al. (2020) find a physiological \r\ncontribution to TCR of 0.12degC (range 0.02degC-0.29degC across models) \r\nowing to physiological adjustments to the CO2 ERF (Section 7.3.2.1)."


id: c175f2ac72eb6916dce5e3954690c690
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31344
content:
"There is robust evidence and high agreement across a  diverse \r\nrange of modelling approaches and thus high confidence that \r\nradiative feedbacks are the largest source of uncertainty in projected \r\nglobal warming out to 2100 under increasing or stable emissions \r\nscenarios, and that cloud feedbacks in particular are the dominant \r\nsource of that uncertainty. Uncertainty in radiative forcing plays an \r\nimportant but generally secondary role. Uncertainty in global ocean \r\nheat uptake plays a lesser role in global warming uncertainty, but \r\nocean circulation could play an important role through its effect on \r\nsea surface warming patterns which in turn project onto radiative \r\nfeedbacks through the pattern effect (Section 7.4.4.3)."


id: 8fb6bfa04d2dea3ba302b7ba9ea7c606
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22493
content:
"The spread in historical surface warming across CMIP5 ESMs \r\nshows a weak correlation with inter-model differences in radiative \r\nfeedback or ocean heat uptake processes but a high correlation with \r\ninter-model differences in radiative forcing owing to large variations \r\nin aerosol forcing across models (Forster et al., 2013). Likewise, the \r\nspread in projected 21st-century warming across ESMs depends \r\nstrongly on which emissions scenario is employed (Section  4.3.1; \r\nHawkins and Sutton, 2012). Strong emissions reductions would \r\nremove aerosol forcing (Section 6.7.2) and this could dominate the \r\nuncertainty in near-term warming projections (Armour and Roe, 2011; \r\nMauritsen and Pincus, 2017; Schwartz, 2018; Smith et al., 2019). On \r\npost-2100 time scales carbon cycle uncertainty such as that related to \r\npermafrost thawing could become increasingly important, especially \r\nunder high-emissions scenarios (Figure 5.30)."


id: 491b722d6b50521f6ec6732a2b6682e9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10086
content:
"In summary, there is high confidence that cloud feedbacks are the \r\ndominant source of uncertainty for late 21st-century projections \r\nof transient global warming under increasing or stable emissions \r\nscenarios, whereas uncertainty is dominated by aerosol ERF in strong \r\nmitigation scenarios. Global ocean heat uptake is a smaller source of \r\nuncertainty in long-term surface warming (high confidence)."


id: 195dabcfa8074f9ed091c43a8bf2bf2e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1680
content:
"Emissions metrics are used to compare the relative effect of emissions \r\nof different gases over time in terms of radiative forcing, global surface \r\ntemperature or other climate effects. They are introduced in Chapter 1 \r\n(Box 1.3). Chapter 8 of AR5 (Myhre et al., 2013b) comprehensively \r\ndiscussed different emissions metrics so this section focuses on "


id: 62c69bd62d2110680567f0fab4e9966b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14676
content:
"updates since that report. Section  7.6.1 updates the physical \r\nassessment. Section 7.6.2 assesses developments in the comparison \r\nof emissions of short- and long-lived gases. Box 7.3 assesses physical \r\naspects of emissions metric use within climate policy."


id: c2e131eb488dd25a02106955c56a7820
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vector_id: 31561
content:
"The radiative properties and lifetimes of compounds are the \r\nfundamental component of all emissions metrics. Since AR5, there \r\nhave been advances in the understanding of the radiative properties \r\nof various compounds (see Sections 7.3.1, 7.3.2 and 7.3.3), and \r\nhence their effective radiative efficiencies (ERFs per unit change \r\nin concentration). For CO2, CH4 and N2O, better accounting of the \r\nspectral properties of these gases has led to re-evaluation of their \r\nstratospheric-temperature-adjusted radiative forcing (SARF) \r\nradiative efficiencies and their dependence on the background \r\ngas concentrations (Section  7.3.2). For CO2, CH4, N2O, CFC-11 and \r\nCFC-12 the tropospheric adjustments (Sections 7.3.1 and 7.3.2) are \r\nassessed to make a non-zero contribution to ERF. There is insufficient \r\nevidence to include tropospheric adjustments for other halogenated \r\ncompounds. The re-evaluated effective radiative efficiency for CO2\r\nwill affect all emissions metrics relative to CO2."


id: c72b0f859074824e0a3e4d4ea8b04184
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32360
content:
"This section discusses metrics that relate emissions to physical \r\nchanges in the climate system. Other metrics, for instance relating \r\nto economic costs or 'damage' are discussed in WGIII, Chapter  2. \r\nThe same Chapter also assesses literature examining the extent \r\nto which different physical metrics are linked to cost-benefit and \r\ncost-effectiveness metrics. One metric, the 100-year global warming \r\npotentials (GWP-100), has extensively been employed in climate \r\npolicy to report emissions of different GHGs on the same scale. Other \r\nphysical metrics exist, and these are discussed in this section."


id: 63abb4f1a725f8eb664d4b0f06b05d1e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14826
content:
"Emissions metrics can be quantified as the magnitude of the effect \r\na unit mass of emission of a species has on a key measure of climate \r\nchange. This section focuses on physical measures such as the radiative \r\nforcing, GSAT change, global average precipitation change, and global \r\nmean sea level rise (Myhre et al., 2013b; Sterner et al., 2014; Shine \r\net al., 2015). When used to represent a climate effect, the metrics are \r\nreferred to as absolute metrics and expressed in units of 'effect per kg' \r\n(e.g., absolute global warming potentials, AGWP or absolute global \r\ntemperature-change potentials, AGTP). More commonly, these are \r\ncompared with a reference species (almost always CO2 in kg (CO2)), to \r\ngive a dimensionless factor (written as e.g., global warming potentials \r\n(GWP) or global temperature-change potential (GTP)). The unit mass \r\nis usually taken as a 1 kg instantaneous 'pulse' (Myhre et al., 2013b), \r\nbut can also refer to a 'step' in emissions rate of 1 kg yr-1."


id: c18059e0721875b40f1dd85a3c1a1227
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31348
content:
"The effective radiative efficiencies (including adjustments from \r\nSection 7.3.2) for 2019 background concentrations for CO2, CH4 and N2O \r\nare assessed to be 1.33x10-5, 3.89x10-4 and 3.19x10-3 W m-2 ppb-1\r\nrespectively (see Table  7.15 for uncertainties), compared to AR5 \r\nassessments of 1.37x10-5, 3.63x10-4 and 3.00x10-3 W  m-2 ppb-1. \r\nFor CO2, increases due to the adjustments do not quite balance the \r\ndecreases due to the increasing background concentration. For CH4, \r\nincreases due to the re-evaluated radiative properties more than offset \r\nthe decreases due to the increasing background concentration. For \r\nN2O the addition of tropospheric adjustments increases the effective \r\nradiative efficiency. Radiative efficiencies of halogenated species have \r\nbeen revised slightly (Section 7.3.2.4) and for CFCs include tropospheric \r\nadjustments."


id: 391b53cc5781de0ce6bd8853f135537f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7254
content:
"The perturbation lifetimes of CH4 (Section 6.3.1). and N2O (Section 5.2.3.1) \r\nhave been slightly revised since AR5 to be 11.8  +-  1.8  years and \r\n109 +- 10 years, respectively (Table 7.15). The lifetimes of halogenated \r\ncompounds have also been slightly revised (Hodnebrog et al., 2020a)."


id: 3654c6f3e2ea83802cba305aee95e152
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6792
content:
"There is a cause-effect chain that links human activity to emissions, \r\nthen from emissions to radiative forcing, climate response and climate \r\nimpacts (Fuglestvedt et  al., 2003). Each step in the causal  chain \r\nrequires an inference or modelling framework that maps causes to \r\neffects. Emissions metrics map from emissions of some compound \r\nto somewhere further down the cause-and-effect chain, radiative \r\nforcing (e.g., GWP) or temperature (e.g., GTP) or other effects (such \r\nas sea level rise or socio-economic impacts). While variables later \r\nin the chain have greater policy or societal relevance, they are also \r\nsubject to greater uncertainty because each step in the chain includes \r\nmore modelling systems, each of which brings its own uncertainty \r\n(Figure 1.15; Balcombe et al., 2018)."


id: 941508ad3c7b46c52fcaec415113bfec
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 23257
content:
"Although there has been greater understanding since AR5 of the \r\ncarbon cycle responses to CO2 emissions (Sections 5.4 and 5.5), there \r\nhas been no new quantification of the response of the carbon cycle \r\nto an instantaneous pulse of CO2 emission since Joos et al. (2013)."


id: d374533349ccf157e6f22bb61f5447d9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34539
content:
"The basis of all the emissions metrics is the time profile of effective \r\nradiative forcing (ERF) following the emission of a  particular \r\ncompound. The emissions metrics are then built up by relating the \r\nforcing to the desired physical indicators. These forcing-response \r\nrelationships can either be generated from emulators (Cross-Chapter \r\nBox 7.1; Tanaka et al., 2013; Gasser et al., 2017b), or from analytical \r\nexpressions based on parametric equations (response functions) \r\nderived from more complex models (Myhre et al., 2013b)."


id: 34b8c578adf6882c1838b24d3da4b203
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6515
content:
"Since AR5, understanding of the radiative effects of emitted \r\ncompounds has continued to evolve and these changes are assessed \r\nin Section 7.6.1.1. Metrics relating to precipitation and sea level have \r\nalso been quantified (Section 7.6.1.2). Understanding of how emissions \r\nmetrics are affected by the carbon cycle response to temperature has \r\nimproved. This allows the carbon cycle response to temperature \r\nto be more fully included in the emissions metrics presented here \r\n(Section 7.6.1.3). There have also been developments in approaches \r\nfor comparing short-lived GHGs to CO2 in the context of mitigation and \r\nglobal surface temperature change (Section 7.6.1.4). Emissions metrics \r\nfor selected key compounds are presented in Section 7.6.1.5."


id: 64bf437b3adfa98e71c0ea8ac30ae712
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 15004
content:
"To illustrate the analytical approach, the ERF time evolution following \r\na  pulse of emission can be considered an absolute global forcing \r\npotential (AGFP; similar to the 'Instantaneous Climate Impact' of \r\nEdwards and Trancik, 2014). This can be transformed into an absolute "


id: b8c67baf7697d2443a926a451012f7ee
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 29714
content:
"derived by replacing the global surface temperature response \r\nfunction with a  regional response matrix relating forcing changes \r\nin one region to temperature changes in another (W.J. Collins et al., \r\n2013; Aamaas et al., 2017; Lund et al., 2017)."


id: d59dda1e882d390b44bd616df2d9b732
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34897
content:
"global temperature-change potential (AGTP) by combining the \r\nradiative forcing with a global surface temperature response function. \r\nThis temperature response is typically derived from a two-layer energy \r\nbalance emulator (Supplementary Material 7.SM.5; Myhre et  al., \r\n2013b). For further physical indicators further response functions are \r\nneeded based on the radiative forcing or temperature, for instance. \r\nSterner et  al. (2014) used an upwelling-diffusiveenergy balance \r\nmodel to derive the thermosteric component of sea level rise as \r\nresponse functions to radiative forcing or global surface temperature. \r\nA metric for precipitation combines both the radiative forcing (AGFP) \r\nand temperature (AGTP) responses to derive an absolute global \r\nprecipitation potential (AGPP; Shine et  al., 2015). The equations \r\nrelating these metrics are given in Supplementary Material 7.SM.5."


id: a5bc77290f385267c6205a261ed07f31
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26385
content:
"For the research discussed above, metrics for several physical \r\nvariables can be constructed that are linear functions of radiative \r\nforcing. Similar metrics could be devised for other climate variables \r\nprovided they can be related by response functions to radiative \r\nforcing or global surface temperature change. The radiative forcing \r\ndoes not increase linearly with emissions for any species, but the \r\nnon-linearities (for instance changes in CO2 radiative efficiency) are \r\nsmall compared to other uncertainties."


id: ee53ec88f6383eeeb92662425dc55775
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39303
content:
"The effect of a  compound on climate is not limited to its direct \r\nradiative forcing. Compounds can perturb the carbon cycle affecting \r\natmospheric CO2 concentrations. Chemical reactions from emitted \r\ncompounds can produce or destroy other GHGs or aerosols."


id: 356d93cb7e6476a3d10b3fce48cdfe8e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6647
content:
"Each step from radiative forcing to global surface temperature to \r\nsea level rise introduces longer time scales and therefore prolongs \r\nfurther the contributions to climate change of short-lived GHGs \r\n(Myhre et al., 2013b). Thus, short-lived GHGs become more important \r\n(relative to CO2) for sea level rise than for temperature or radiative \r\nforcing (Zickfeld et al., 2017). Integrated metrics include the effects \r\nof a pulse emission from the time of emission up to the time horizon, \r\nwhereas endpoint metrics only include the effects that persist out \r\nto the time horizon. Because the largest effects of short-lived GHGs \r\noccur shortly after their emission and decline towards the end of \r\nthe time period, short-lived GHGs have relatively higher integrated \r\nmetrics than their corresponding endpoint metrics (Peters et  al., \r\n2011; Levasseur et al., 2016)."


id: 43aaf3f3dec82cdb95e0c789f81e93c5
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 9131
content:
"For species perturbations that lead to a strong regional variation in \r\nforcing pattern, the regional temperature response can be different \r\nto that for CO2. Regional equivalents to the global metrics can be "


id: 5901d2085de4555e0a07a5bed03a731d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12899
content:
"Methane can also affect the oxidation pathways of aerosol formation \r\n(Shindell et  al., 2009) but the available literature is insufficient to \r\nmake a  robust assessment of this. Hydrocarbon and molecular \r\nhydrogen oxidation also leads to tropospheric ozone production \r\nand change in methane lifetime (Collins et  al., 2002; Hodnebrog \r\net al., 2018). For reactive species the emissions metrics can depend \r\non where the emissions occur, and the season of emission (Aamaas \r\net al., 2016; Lund et al., 2017; Persad and Caldeira, 2018). The AR5 \r\nincluded a contribution to the emissions metrics for ozone-depleting \r\nsubstances (ODSs) from the loss of stratospheric ozone. The \r\nassessment of ERFs from ODSs in Chapter 6 (Section 6.4.2) suggests \r\nthe quantification of these terms may be more uncertain than the \r\nformulation in AR5 so these are not included here."


id: 1c66ec857936a51545a489ef95a9f1cf
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2188
content:
"Emissions of non-CO2 species can affect the carbon cycle in other \r\nways: emissions of ozone precursors can reduce the carbon uptake \r\nby plants (W.J. Collins et al., 2013); emissions of reactive nitrogen \r\nspecies can fertilize plants and hence increase the carbon uptake \r\n(Zaehle et al., 2015); and emissions of aerosols or their precursors can \r\naffect the utilisation of light by plants (Cohan et al., 2002; Mercado \r\net  al., 2009; Mahowald et  al., 2017; see Section  6.4.4 for further \r\ndiscussion). There is robust evidence that these processes occur and \r\nare important, but insufficient evidence to determine the magnitude \r\nof their contributions to emissions metrics. Ideally, emissions metrics \r\nshould include all indirect effects to be consistent, but limits to our \r\nknowledge restrict how much can be included in practice."


id: 9dadf532016d3c2b6e4cdfb570062190
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 24973
content:
"a ratio AGTP S\r\nX /AGTPCO2 (Collins et al., 2020). This is referred to as \r\na  combined GTP (CGTP) in Collins et  al.  (2020), and has units of \r\nyears (the standard GTP is dimensionless). This CGTP shows less \r\nvariation with time than the standard GTP (comparing Figure 7.21c \r\nwith Figure 7.21d) and provides a scaling for comparing a change \r\nin emissions rate (in kg yr -1) of short-lived GHGs with a  pulse \r\nemission or change in cumulative CO2 emissions (in kg). Cumulative \r\nCO2 equivalent emissions are given by CGTP x emissions rate of \r\nshort-lived GHGs. The CGTP can be calculated for any species, but \r\nit is least dependent on the chosen time horizon for species with \r\nlifetimes less than half the time horizon of the metric (Collins \r\net al., 2020). Pulse-step metrics can therefore be useful where time \r\ndependence of pulse metrics, like GWP or GTP, complicates their use \r\n(see Box 7.3)."


id: 7001ed4527f19f145e6b0fc2534ddc4f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 16963
content:
"accounted for exactly with the CO2 forcing equivalent metric (Wigley, \r\n1998; Allen et al., 2018b; Jenkins et al., 2018) that produces a CO2\r\nemissions time profile such that the radiative forcing matches the \r\ntime evolution of that from the non-CO2 emissions. But other metric \r\napproaches can approximate this exact approach."


id: f4bef92b9c09f847921b5878c008abdc
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40429
content:
"For a  stable global warming from non-CO2 climate agents (gas or \r\naerosol) their effective radiative forcing needs to gradually decrease \r\n(Tanaka and O'Neill, 2018). Cain et al. (2019) find this decrease to \r\nbe around 0.3% yr-1 for the climate response function in AR5 \r\n(Myhre et  al., 2013b). To account for this, a  quantity referred to \r\nas GWP* has been defined that combines emissions (pulse) and \r\nchanges in emissions levels (step) approaches (Cain et  al., 2019; "


id: df1c3fb052cce0c869d77b77b6951db3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36505
content:
"Smith  et  al.,  2021).2 The emissions component accounts for the \r\nneed for emissions to decrease to deliver a stable warming. The step \r\n(sometimes referred to as flow or rate) term in GWP* accounts for \r\nthe change in global surface temperature that arises from a change \r\nin short-lived GHG emissions rate, as in CGTP, but here approximated \r\nby the change in emissions over the previous 20 years."


id: c2b8170f799cfc411f1b9247d0860112
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 31540
content:
"Cumulative CO2 emissions and GWP*-based cumulative CO2\r\nequivalent GHG emissions multiplied by TCRE closely approximate \r\nthe global warming associated with emissions time series (of CO2 and \r\nGHG, respectively) from the start of the time series (Lynch et al., 2020). \r\nBoth the CGTP and GWP* convert short-lived GHG emissions rate \r\nchanges into cumulative CO2 equivalent emissions, hence scaling \r\nthese by TCRE gives a  direct conversion from short-lived GHG \r\nemissions to global surface temperature change. By comparison \r\nexpressing methane emissions as CO2 equivalent emissions using \r\nGWP-100 overstates the effect of constant methane emissions on \r\nglobal surface temperature by a  factor of 3-4 (Lynch et  al., 2020, \r\ntheir Figure 5), while understating the effect of any new methane \r\nemission source by a factor of 4-5 over the 20 years following the \r\nintroduction of the new source (Lynch et al., 2020, their Figure 4)."


id: fe7825f313d5a654b902bb46fc2b1f68
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 42143
content:
"In summary, new emissions metric approaches such as GWP* and \r\nCGTP are designed to relate emissions changes in short-lived GHGs \r\nto emissions of CO2 as they better account for the different physical \r\nbehaviours of short- and long-lived gases. Through scaling the \r\ncorresponding cumulative CO2 equivalent emissions by the TCRE, \r\nthe GSAT response from emissions over time of an aggregated set of "


id: c47b9352d62a6f334f3016143012b486
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31870
content:
"Figure  7.22 explores how cumulative CO2 equivalent emissions \r\nestimated for methane vary under different emissions metric choices \r\nand how estimates of the global surface air temperature (GSAT) \r\nchange deduced from these cumulative emissions compare to the "


id: a45b8767fb76f0509356fb234467a28c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26119
content:
"gases can be estimated. Using either these new approaches, or treating \r\nshort- and long-lived GHG emissions pathways separately, can improve \r\nthe quantification of the contribution of emissions to global warming \r\nwithin a  cumulative emissions framework, compared to approaches \r\nthat aggregate emissions of GHGs using standard CO2 equivalent \r\nemissions metrics. As discussed in Box 7.3, there is high confidence \r\nthat multi-gas emissions pathways with the same time-dependence \r\nof aggregated CO2 equivalent emissions estimated from standard \r\napproaches, such as weighting emissions by their GWP-100 values, \r\nrarely lead to the same estimated temperature outcomes."


id: 349d7facb6adc580da208f9f9e9fa26c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6492
content:
"The lifetimes and radiative efficiencies for halogenated compounds \r\nare taken from Hodnebrog et al. (2020a). Combined metrics (CGTPs) \r\nare presented for compounds with lifetimes less than 20 years. Note \r\nthat CGTP has units of years and is applied to a change in emissions rate \r\nrather than a change in emissions amount. Changes since AR5 are due \r\nto changes in radiative properties and lifetimes (Section 7.6.1.1), and \r\nindirect contributions (Section 7.6.1.3). Table 7.15 also gives overall \r\nemissions uncertainties in the emissions metrics due to uncertainties \r\nin radiative efficiencies, lifetimes and the climate response function \r\n(Supplementary Material, Tables 7.SM.8 to 7.SM.13)."


id: bf6cb38ada066194b060528f19b705c8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30943
content:
"Following their introduction in AR5 the assessed metrics now routinely \r\ninclude the carbon cycle response for non-CO2 gases (Section 7.6.1.3). \r\nAs assessed in this earlier section, the carbon cycle contribution is \r\nlower than in AR5. Contributions to CO2 formation are included for \r\nmethane depending on whether or not the source originates from \r\nfossil carbon, thus methane from fossil fuel sources has slightly higher \r\nemissions metric values than that from non-fossil sources."


id: ccbf32713ab9dd93f791ecbaaa4d62c6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 33352
content:
"Emissions metrics for selected compounds are presented in Table 7.15, \r\nwith further compounds presented in the Supplementary Material, \r\nTable 7.SM.7. The evolution of the CO2 concentrations in response to \r\na pulse emission is as in AR5 (Joos et al., 2013; Myhre et al., 2013b), \r\nthe perturbation lifetimes for CH4 and N2O are from Section 7.6.1.1. "


id: 4ee04ef3fa25f5c865c4956fb6a3dc90
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 11156
content:
"Table 7.15 | Emissions metrics for selected species: global warming potential (GWP), global temperature-change potential (GTP). All values include carbon \r\ncycle responses as described in Section 7.6.1.3. Combined GTPs (CGTPs) are shown only for species with a lifetime less than 20 years (Section 7.6.1.4). Note CGTP has units of \r\nyears and is applied to a change in emissions rate rather than a change in emissions amount. The radiative efficiencies are as described in Section 7.3.2 and include tropospheric \r\nadjustments where assessed to be non-zero in Section 7.6.1.1. The climate response function is from Supplementary Material 7.SM.5.2. Uncertainty calculations are presented \r\nin Supplementary Tables 7.SM.8 to 7.SM.13. Chemical effects of CH4 and N2O are included (Section 7.6.1.3). Contributions from stratospheric ozone depletion to halogenated \r\nspecies metrics are not included. Supplementary Table 7.SM.7 presents the full table."


id: cf760f50bf3916d7cb329e78196c697a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 33851
content:
"Following AR5, this Report does not recommend an emissions metric because the appropriateness of the choice depends on the \r\npurposes for which gases or forcing agents are being compared. Emissions metrics can facilitate the comparison of effects of emissions \r\nin support of policy goals. They do not define policy goals or targets but can support the evaluation and implementation of choices within \r\nmulti-component policies (e.g., they can help prioritize which emissions to abate). The choice of metric will depend on which aspects of \r\nclimate change are most important to a particular application or stakeholder and over which time horizons. Different international and \r\nnational climate policy goals may lead to different conclusions about what is the most suitable emissions metric (Myhre et al., 2013b)."


id: e61989dcfb3722a1940116adbd5b3e5a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37779
content:
"Global warming potentials (GWP) and global temperature-change potentials (GTP) give the relative effect of pulse emissions, that is, how \r\nmuch more energy is trapped (GWP) or how much warmer (GTP) the climate would be when unit emissions of different compounds are \r\ncompared (Section 7.6.1.2). Consequently, these metrics provide information on how much energy accumulation (GWP) or how much \r\nglobal warming (GTP) could be avoided (over a given time period, or at a given future point in time) by avoiding the emission of a unit of \r\na short-lived greenhouse gas compared to avoiding a unit of CO2. By contrast, the new metric approaches of combined GTP (CGTP) and \r\nGWP* closely approximate the additional effect on climate from a time series of short-lived GHG emissions, and can be used to compare \r\nthis to the effect on temperature from the emission or removal of a unit of CO2 (Section 7.6.1.4; Allen et al., 2018b; Collins et al., 2020)."


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vector_id: 8507
content:
"If global surface temperature stabilization goals are considered, cumulative CO2 equivalent emissions computed with the GWP-100 \r\nemissions metric would continue to rise when short-lived GHG emissions are reduced but remain above zero (Figure 7.22b). Such \r\na  rise would not match the expected global surface temperature stabilization or potential decline in warming that comes from \r\na reduction in emissions of short-lived greenhouse gases (Pierrehumbert, 2014; Allen et al., 2018b; Cain et al., 2019; Collins et al., \r\n2020; Lynch et al., 2020, 2021). This is relevant to net zero GHG emissions goals (Section 7.6.2 and Box 1.4)."


id: 4d5f57bfc1c1dc3e1b0174e1e0a98cf
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10891
content:
"Although there is significant history of using single-basket approaches, supported by emissions metrics such as GWP-100, in climate \r\npolicies such as the Kyoto Protocol, multi-basket approaches also have many precedents in environmental management, including the \r\nMontreal Protocol (Daniel et al., 2012). Further assessment of the performance of physical and economics-based metrics in the context \r\nof climate change mitigation is provided in the contribution of Working Group III to AR6."


id: 8753ca1330df46dd107e06fa4aca9b39
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20970
content:
"The Earth's energy budget describes the flow of energy within the climate system. Since at least 1970 there \r\nhas been a  persistent imbalance in the energy flows that has led to excess energy being absorbed by the \r\nclimate system. By measuring and understanding these energy flows and the role that human activities play in \r\nchanging them, we are better able to understand the causes of climate change and project future climate change \r\nmore accurately."


id: 422095a6a3e72001fb18e74f17bcd8b6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8834
content:
"Our planet receives vast amounts of energy every day in the form of sunlight. Around a third of the sunlight is \r\nreflected back to space by clouds, by tiny particles called aerosols, and by bright surfaces such as snow and ice. \r\nThe rest is absorbed by the ocean, land, ice and atmosphere. The planet then emits energy back out to space in \r\nthe form of thermal radiation. In a world that was not warming or cooling, these energy flows would balance. \r\nHuman activity has caused an imbalance in these energy flows."


id: c38e18e3a6ab1ecdb39ffd9e92cb03f0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31683
content:
"Human activities have unbalanced these energy flows in two main ways. First, increases in greenhouse gas levels \r\nhave led to more of the emitted thermal radiation being absorbed by the atmosphere, instead of being released to \r\nspace. Second, increases in pollutants have increased the amount of aerosols such as sulphates in the atmosphere \r\n(see FAQ 6.1). This has led to more incoming sunlight being reflected away, by the aerosols themselves and \r\nthrough the formation of more cloud drops, which increases the reflectivity of clouds (see FAQ 7.2)."


id: 869c9948074581f71851702a499e3560
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20845
content:
"Altogether, the global energy flow imbalance since the 1970s has been just over half a watt per square metre \r\nof the Earth's surface. This sounds small, but because the imbalance is persistent and because Earth's surface is \r\nlarge, this adds up to about 25 times the total amount of primary energy consumed by human society, compared \r\nover 1971 to 2018. Compared to the IPCC Fifth Assessment Report (AR5), we are now better able to quantify \r\nand track these energy flows from multiple lines of evidence, including satellite data, direct measurements of \r\nocean temperatures, and a wide variety of other Earth system observations (see FAQ 1.1). We also have a better \r\nunderstanding of the processes contributing to this imbalance, including the complex interactions between \r\naerosols, clouds and radiation."


id: d1c50ba9668fd1fd74c9c7c490ba014e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34256
content:
"Research has shown that the excess energy since the 1970s has mainly gone into warming the ocean (91%), \r\nfollowed by the warming of land (5%) and the melting of ice sheets and glaciers (3%). The atmosphere has \r\nwarmed substantially since 1970, but because it is comprised of thin gases it has absorbed only 1% of the excess \r\nenergy (FAQ 7.1, Figure 1). As the ocean has absorbed the vast majority of the excess energy, especially within \r\nits top two kilometres, the deep ocean is expected to continue to warm and expand for centuries to millennia, \r\nleading to long-term sea level rise - even if atmospheric greenhouse gas levels were to decline (see FAQ 5.3). \r\nThis is in addition to the sea level rise expected from melting ice sheets and glaciers."


id: 6035f96b90e382edf7c10fbecf58606
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14229
content:
"Understanding the Earth's energy budget  al.o helps to narrow uncertainty in future projections of climate. \r\nBy testing climate models against what we know about the Earth's energy budget, we can make more confident \r\nprojections of surface temperature changes we might expect this century and beyond."


id: eb604db4a21bb6800b96e3547e7c855a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38765
content:
"Since at least 1970, there has been a persistent imbalance in the energy flows that has \r\nled to excess energy being absorbed by different components of the climate system."


id: 3b994a6d5d6af1524a1d2a83797c1119
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7672
content:
"FAQ 7.1, Figure 1 | The Earth's energy budget compares the flows of incoming and outgoing energy that are relevant for the climate \r\nsystem. Since at least the 1970s, less energy is flowing out than is flowing in, which leads to excess energy being absorbed by the ocean, land, ice and \r\natmosphere, with the ocean absorbing 91%."


id: a662e9a07a6bf3fcd0a8605ea5759b76
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26493
content:
"One of the biggest challenges in climate science has been to predict how clouds will change in a warming world \r\nand whether those changes will amplify or partially offset the warming caused by increasing concentrations of \r\ngreenhouse gases and other human activities. Scientists have made significant progress over the past decade and \r\nare now more confident that changes in clouds will amplify, rather than offset, global warming in the future."


id: c7fc7a8d51074b1cd750df380a0a38fe
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32490
content:
"The concentration of aerosols in the atmosphere has markedly increased since the pre-industrial era, and this \r\nhas had two important effects on clouds. First, clouds now reflect more incoming energy because cloud droplets \r\nhave become more numerous and smaller. Second, smaller droplets may delay rain formation, thereby making \r\nthe clouds last longer, although this effect remains uncertain. Hence, aerosols released by human activities have \r\nhad a cooling effect, counteracting a considerable portion of the warming caused by increases in greenhouse \r\ngases over the last century (see FAQ 3.1). Nevertheless, this cooling effect is expected to diminish in the future, as \r\nair pollution policies progress worldwide, reducing the amount of aerosols released into the atmosphere."


id: 931f1f0d04e0a0fa8cf3a413836d9f0a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 23090
content:
"Since the pre-industrial period, the Earth's surface and atmosphere have warmed, altering the properties of \r\nclouds, such as their altitude, amount and composition (water or ice), thereby affecting the Earth's energy budget \r\nand, in turn, changing temperature. This cascading effect of clouds, known as the cloud feedback, could either \r\namplify or offset some of the future warming and has long been the biggest source of uncertainty in climate \r\nprojections. The problem stems from the fact that clouds can change in many ways and that their processes occur \r\non much smaller scales than global climate models can explicitly represent. As a result, global climate models \r\nhave disagreed on how clouds, particularly over the subtropical ocean, will change in the future and whether the \r\nchange will amplify or suppress the global warming."


id: bac5851355bbd0972ce9716a9514f38c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30076
content:
"In summary, clouds will amplify rather than suppress the warming of the climate system in the future, as more \r\ngreenhouse gases and fewer aerosols are released to the atmosphere by human activities."


id: 6c5c28dede993e5b0c65bed72429f39
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 16357
content:
"FAQ 7.2, Figure 1 | Interactions between clouds and the climate, today and in a warmer future. Global warming is expected to alter the altitude \r\n(left) and the amount (centre) of clouds, which will amplify warming. On the other hand, cloud composition will change (right), offsetting some of the \r\nwarming. Overall, clouds are expected to amplify future warming."


id: b34b2c4758f5229dd2a6c89c8aebfd74
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28785
content:
"For a given future scenario, climate models project a range of changes in global surface temperature. This range \r\nis closely related to equilibrium climate sensitivity, or ECS, which measures how climate models respond to \r\na doubling of carbon dioxide in the atmosphere. Models with high climate sensitivity project stronger future \r\nwarming. Some climate models of the new generation are more sensitive than the range assessed in the IPCC \r\nSixth Assessment Report. This leads to end-of-century global warming in some simulations of up to 2degC-3degC \r\nabove the current IPCC best estimate. Although these higher warming levels are not expected to occur, high-ECS \r\nmodels are useful for exploring low-likelihood, high-impact futures."


id: d758857793a86348eb770bb71f6c0e5a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35190
content:
"The equilibrium climate sensitivity (ECS) is defined as the long-term global warming caused by a doubling of \r\ncarbon dioxide above its pre-industrial concentration. For a given emissions scenario, much of the uncertainty in \r\nprojections of future warming can be explained by the uncertainty in ECS (FAQ 7.3, Figure 1). The significance \r\nof equilibrium climate sensitivity has long been recognized, and the first estimate was presented by Swedish \r\nscientist Svante Arrhenius in 1896."


id: 5d27e1ce5e853be4bafbd190effe0ce0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 13665
content:
"This Sixth Assessment Report concludes that there is a 90% or more chance (very likely) that the ECS is between \r\n2degC and 5degC. This represents a significant reduction in uncertainty compared to the Fifth Assessment Report, \r\nwhich gave a 66% chance (likely) of ECS being between 1.5degC and 4.5degC. This reduction in uncertainty has been \r\npossible not through a single breakthrough or discovery but instead by combining evidence from many different \r\nsources and by better understanding their strengths and weaknesses."


id: b8931012a692dbcbf2cadfee0ef55bf
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29680
content:
"ce from ancient climates that had reached equilibrium with greenhouse gas concentrations, such as the \r\n period of the last ice age around 20,000 years ago, or warmer periods further back in time, provide \r\ndata on the ECS of the climate system (see FAQ 1.3)."


id: a73a14e78eb4e3f2a47aeb726b064d49
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26635
content:
"All four lines of evidence rely, to some extent, on climate models, and interpreting the evidence often benefits \r\nfrom model diversity and spread in modelled climate sensitivity. Furthermore, high-sensitivity models can provide \r\nimportant insights into futures that have a low likelihood of occurring but that could result in large impacts. \r\nBut, unlike in previous assessments, climate models are not considered a line of evidence in their own right in the \r\nIPCC Sixth Assessment Report."


id: c76f92f217d17d71a7a5435280d7bd0c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32400
content:
"The ECS of the latest climate models is, on average, higher than that of the previous generation of models \r\nand also higher than this Report's best estimate of 3.0degC. Furthermore, the ECS values in some of the new \r\nmodels are both above and below the 2degC to 5degC very likely range, and although such models cannot be ruled \r\nout as implausible solely based on their ECS, some simulations display climate change that is inconsistent with \r\nthe observed changes when tested with ancient climates. A slight mismatch between models and this Report's \r\nassessment is only natural because this Report's assessment is largely based on observations and an improved \r\nunderstanding of the climate system."


id: 49d8a161c4ba27dc4e67baa1b3b5def0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10231
content:
"FAQ 7.3, Figure 1 | Equilibrium climate sensitivity and future warming. (left) Equilibrium climate sensitivities for the current generation (Coupled \r\nModel Intercomparison Project Phase 6, CMIP6) climate models, and the previous (CMIP5) generation. The assessed range in this Report (AR6) is also shown. \r\n(right) Climate projections of CMIP5, CMIP6 and AR6 for the very high-emissions scenarios RCP8.5, and SSP5-8.5, respectively. The thick horizontal lines \r\nrepresent the multi-model average and the thin horizontal lines represent the results of individual models. The boxes represent the model ranges for CMIP5 \r\nand CMIP6 and the range assessed in AR6."


id: a7b0e77990a60057f2c271338c28a7b4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26715
content:
"Richard P. Allan (United Kingdom), Paola A. Arias (Colombia), Mathew Barlow (United States \r\nof America), Ruth Cerezo-Mota (Mexico), Annalisa Cherchi (Italy), ThianY. Gan (Canada/Malaysia), \r\nJoelle Gergis (Australia), Dabang Jiang (China), Asif Khan (Pakistan), Wilfried Pokam Mba \r\n(Cameroon), Daniel Rosenfeld (Israel), Jessica Tierney (United States of America), Olga Zolina \r\n(The Russian Federation/France, The Russian Federation)"


id: 387896e5b3d10c085fb1db31998edd9f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7146
content:
"Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, \r\nD.  Jiang, A.  Khan, W.  Pokam Mba, D.  Rosenfeld, J. Tierney, and O.  Zolina, 2021: Water Cycle Changes. In Climate \r\nChange 2021: The Physical Science Basis. Contribution of Working Group I  to the Sixth Assessment Report of the \r\nIntergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Pean, S. Berger, \r\nN. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, \r\nO. Yelekci, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, \r\npp. 1055-1210, doi:10.1017/9781009157896.010."


id: f4f67fdee37363cf79bdb6304d6e02f7
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40461
content:
"increase plant growth and water-use efficiency, but there is low \r\nconfidence in how these factors drive regional water cycle changes. \r\n{8.2.2, 8.2.3}"


id: 41773332e94ccba89afb9795c6734e59
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8710
content:
"This chapter assesses multiple lines of evidence to evaluate past, \r\npresent and future changes in the global water cycle. It complements \r\nmaterial in Chapters 2, 3 and 4 on observed and projected changes \r\nin the water cycle, and Chapters 10 and 11 on regional climate \r\nchange and extreme events. The assessment includes the physical \r\nbasis for water cycle changes, observed changes in the water cycle \r\nand attribution of their causes, future projections and related key \r\nuncertainties, and the potential for abrupt change. Paleoclimate \r\nevidence, observations, reanalyses and global and regional model \r\nsimulations are considered. The assessment shows widespread, non\u0002uniform human-caused alterations of the water cycle, which have \r\nbeen obscured by a competition between different drivers across the \r\n20th century and that will be increasingly dominated by greenhouse \r\ngas forcing at the global scale."


id: bb388c37ee2dfa43905ad36c53736c5e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30155
content:
"Human-caused climate change has driven detectable changes \r\nin the global water cycle since the mid-20th century (high \r\nconfidence). Global warming has contributed to an overall increase \r\nin atmospheric moisture and precipitation intensity (high confidence), \r\nincreased terrestrial evapotranspiration (medium confidence), \r\ninfluenced global patterns in aridity (very likely), and enhanced \r\ncontrasts in surface salinity and precipitation minus evaporation \r\npatterns over the oceans (high confidence). {3.4.2, 3.4.3, 3.5.2, \r\n8.3.1, 9.2.2}"


id: 1186dbe4c1723019c1ac528e354490a6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 283
content:
"Greenhouse gas forcing has driven increased contrasts \r\nin precipitation amounts between wet and dry seasons \r\nand weather regimes over tropical land areas (medium \r\nconfidence) and a  detectable precipitation increase in the \r\nnorthern high latitudes (high confidence). Greenhouse gas \r\nforcing has also contributed to drying in dry summer climates, \r\nincluding the Mediterranean, south-western Australia, south-western \r\nSouth America, South Africa, and western North America (medium \r\nto high confidence). Earlier onset of spring snowmelt and increased \r\nmelting of glaciers have already contributed to seasonal changes in \r\nstreamflow in high-latitude and low-elevation mountain catchments \r\n(high confidence). {Box 8.2, 8.2.2.1, 8.3.1, 3.3.2, 3.3.3, 3.5.2}"


id: 912475875a7237f4c7f32acdef52c819
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22739
content:
"A warmer climate increases moisture transport into weather \r\nsystems, which, on average, makes wet seasons and events \r\nwetter (high confidence). An increase in near-surface atmospheric \r\nwater holding capacity of about 7%  per  1degC of warming explains \r\na  similar magnitude of intensification of heavy precipitation events \r\n(from sub-daily up to seasonal time scales) that increases the severity \r\nof flood hazards when these extremes occur (high confidence). \r\nThe severity of very wet and very dry events increases in a warming \r\nclimate (high confidence), but changes in atmospheric circulation \r\npatterns alter where and how often these extremes occur, with \r\nsubstantial regional differences and seasonal contrasts. A slowdown \r\nof tropical circulation with global warming partly offsets the warming\u0002induced strengthening of precipitation in monsoon regions (high \r\nconfidence). {8.2.2, 8.2.3, 8.3.1.7, 8.4.1, 8.5.1}"


id: 8ecec104a9863fd535e6fb9bf144767
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22310
content:
"Land-use change and water extraction for irrigation have \r\ninfluenced local and regional responses in the water cycle \r\n(high confidence). Large-scale deforestation has likely decreased \r\nevapotranspiration and precipitation and increased runoff over the \r\ndeforested regions. Urbanization has increased local precipitation \r\n(medium confidence) and resulting runoff intensity (high confidence). \r\nIncreased precipitation intensities have enhanced groundwater \r\nrecharge, most notably in tropical regions (medium confidence). \r\nThere is high confidence that groundwater depletion has occurred \r\nsince at least the start of the 21st century as a  consequence of "


id: dfb6a0fc69bbed28b83bd6ca6667d71b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36603
content:
"Warming over land drives an increase in atmospheric \r\nevaporative demand and the severity of droughts (high \r\nconfidence). Greater warming over land than over the ocean alters \r\natmospheric circulation patterns and, on average, reduces continental \r\nnear-surface relative humidity, which contributes to regional drying \r\n(high confidence). Increasing atmospheric CO2 concentrations "


id: ae8ad8b9507c5d3e22b0b8c31bf814
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27942
content:
"groundwater withdrawals for irrigation in agricultural areas in \r\ndrylands (e.g., the southern High Plains and California Central Valley \r\nof the USA, North China Plain, and north-west India). {8.2.3.4, \r\n8.3.1.7, Box 10.3, FAQ 8.1}"


id: 41b7a493289b275a8d6cf08a8080c197
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8755
content:
"mean precipitation amount (medium confidence). It is very likely that \r\nrainfall variability related to the El Nino-Southern Oscillation will be \r\namplified by the end of the 21st century. Sub-seasonal precipitation \r\nvariability is also projected to increase, with fewer rainy days but \r\nincreased daily mean precipitation intensity over many land regions \r\n(high confidence). Precipitation extremes will increase in almost all \r\nregions (high confidence), even where seasonal mean precipitation is \r\nprojected to decrease (medium confidence). There is high confidence\r\nthat heavy precipitation events associated with both tropical and \r\nextratropical cyclones will intensify. {4.5.1.4, 4.5.3.2, 8.2.3.2, 8.4.1, \r\n8.4.2, 8.5.2, 11.7.1.5}"


id: d4c94644662c832f66bcbdf0722982d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34754
content:
"Southern Hemisphere storm tracks and associated precipitation \r\nhave shifted polewards since the 1970s, especially in the austral \r\nsummer and autumn (high confidence). It is very likely that these \r\nchanges are associated with a positive trend in the Southern Annular \r\nMode, related to both stratospheric ozone depletion and greenhouse \r\ngas increases. There is medium confidence that the recent observed \r\nexpansion of the Hadley circulation was caused by greenhouse gas \r\nforcing, especially in the Southern Hemisphere, but there is only low \r\nconfidence in how it influences the drying of subtropical land areas. \r\n{8.2.2, 8.3.2, 3.3.3}"


id: 7080c1276cc1b085f3765a623bb90231
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17050
content:
"There are contrasting projections in monsoon precipitation, \r\nwith increases in more regions than decreases (medium \r\nconfidence). Summer monsoon precipitation is projected to increase \r\nfor the South, South East and East Asian monsoon domains, while \r\nNorth American monsoon precipitation is projected to decrease \r\n(medium confidence). West African monsoon precipitation is \r\nprojected to increase over the Central Sahel and decrease over the \r\nfar western Sahel (medium confidence). There is low confidence in \r\nprojected precipitation changes in the South American and Australian \r\nmonsoons (for both magnitude and sign). There is high confidence\r\nthat the monsoon season will be delayed in North and South \r\nAmerica and medium confidence that it will be delayed in the Sahel. \r\n{8.2.2, 8.4.2.4}"


id: c7502871359638c4f900935a8b0c6883
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32385
content:
"Precipitation associated with extratropical storms and \r\natmospheric rivers will increase in the future in most regions \r\n(high confidence). A  continued poleward shift of storm tracks in \r\nthe Southern Hemisphere (likely) and the North Pacific (medium \r\nconfidence) will lead to similar shifts in annual or seasonal \r\nprecipitation. There is low confidence in projections of blocking and \r\nstationary waves and therefore their influence on precipitation for \r\nalmost all regions. {8.4.2}"


id: ca34705d958afab74b817a0d114729ed
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32914
content:
"The seasonality of precipitation, water availability and \r\nstreamflow will increase with global warming over the \r\nAmazon (medium confidence) and in the subtropics, especially \r\nin the Mediterranean and southern Africa (high confidence).\r\nThe annual contrast between the wettest and driest month of the \r\nyear is likely to increase by 3-5% per 1degC in most monsoon regions \r\nin terms of precipitation, precipitation minus evaporation, and runoff \r\n(medium confidence). There is high confidence in an earlier onset in \r\nspring snowmelt, with higher peak flows at the expense of summer \r\nflows in snow-dominated regions globally, but medium confidence\r\nthat reduced snow volume in lower-latitude regions will reduce \r\nrunoff from snowmelt. {8.2.2, Box 8.2, 8.4.1.7, 8.4.2.4}"


id: fac1e372b4b41ac4fd8cd0a9893721fa
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41492
content:
"Increased evapotranspiration due to growing atmospheric \r\nwater demand will decrease soil moisture over the \r\nMediterranean, south-western North America, southern Africa, \r\nsouth-western South America, and south-western Australia \r\n(high confidence). In the Mediterranean, south-western South \r\nAmerica, and western North America, future aridification will far \r\nexceed the magnitude of change seen in the last millennium (high \r\nconfidence). Some tropical regions are also projected to experience \r\nincreased aridity, including the Amazon basin and Central America \r\n(high confidence). {8.4.1}"


id: 1ef7dc57f6c33776a2401b842dd3422c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2652
content:
"Water cycle variability and extremes are projected to increase \r\nfaster than average changes in most regions of the world and \r\nunder all emissions scenarios (high confidence). In the tropics \r\nand in the extratropics of both hemispheres during summer/warm \r\nseason, interannual variability of precipitation and runoff over land \r\nis projected to increase at a  faster rate than changes in seasonal "


id: 1d30eee5442174c3b6fbdb4e3d6a9e22
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2311
content:
"Representation of key physical processes has improved in \r\nglobal climate models, but they are still limited in their ability \r\nto simulate all aspects of the present-day water cycle and to \r\nagree on future changes (high confidence). Climate change \r\nstudies benefit from sampling the full distribution of model "


id: 6ce79e64553ecf07e40e6fc08b03e374
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 16438
content:
"(SRM) techniques are implemented rapidly or terminated abruptly. \r\nThe impact of SRM is spatially heterogeneous (high confidence), will \r\nnot fully mitigate the greenhouse gas-forced water cycle changes \r\n(medium confidence), and can affect different regions in potentially \r\ndisruptive ways (low confidence). {8.6.3}"


id: 4e1396d32185ca078a954b19e627a42c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11001
content:
"outputs when considering future projections at regional \r\nscales. Increasing horizontal resolution in global climate models \r\nimproves the representation of small-scale features and the statistics \r\nof daily precipitation (high confidence). High-resolution climate and \r\nhydrological models provide a better representation of land surfaces, \r\nincluding topography, vegetation and land-use change, which \r\nimprove the accuracy of simulations of regional changes in the water \r\ncycle (high confidence). There is high confidence in the potential \r\nadded value of regional climate models but only medium confidence\r\nthat this potential is currently realized. {8.5.1}"


id: b8c08d508863e16fb692f0824316dd26
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29711
content:
"Natural climate variability will continue to be a major source of \r\nuncertainty in near-term (2021-2040) water cycle projections \r\n(high confidence). Decadal predictions of water cycle  changes \r\nshould be considered with low confidence in most land areas \r\nbecause the internal variability of precipitation is difficult to predict \r\nand can offset or amplify the forced water cycle response. Water \r\ncycle changes that have already emerged from natural variability \r\nwill become more pronounced in the near term, but the occurrence \r\nof volcanic eruptions (either single large events or clustered smaller \r\nones) can alter the water cycle for several years, decreasing global \r\nmean land precipitation and altering monsoon circulation (high \r\nconfidence). {8.5.2, Cross-Chapter Box 4.1}"


id: 14423f00bbc9e80e4d2d6307cf54df72
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 783
content:
"Continued global warming will further amplify greenhouse \r\ngas-induced changes in large-scale atmospheric circulation \r\nand precipitation patterns (high confidence), but in some \r\ncases regional water cycle changes are not linearly related to \r\nglobal warming. Non-linear water cycle responses are explained by \r\nthe interaction of multiple drivers, feedbacks and time scales (high \r\nconfidence). Non-linear responses of regional runoff, groundwater \r\nrecharge and water scarcity highlight the limitations of simple \r\npattern-scaling techniques (medium confidence). Water resources fed \r\nby melting glaciers are particularly exposed to non-linear responses \r\n(high confidence). {8.5.3}"


id: 538a7ca11259b995d6e370b70611e959
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11971
content:
"Solar radiation modification could drive abrupt changes in \r\nthe water cycle (high confidence). It is very likely that abrupt \r\nwater cycle changes will occur if solar radiation modification "


id: 502c204fcef96301027b16c682fb7c1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11391
content:
"and the extraction of unconventional fossil fuels (Schewe et al., 2014; \r\nD'Odorico et al., 2018; Djehdian et al., 2019). These dependencies \r\nhave resulted in increasing competition for water between the food \r\nand energy sectors. Pressures on this 'food-energy-water nexus' are \r\nfurther compounded by increasing globalization, which can transfer \r\nlarge-scale water demands to other regions of the world, raising \r\nserious concerns about local food and water security in regions that \r\nare highly dependent on agricultural exports or imports (D'Odorico \r\net al., 2018)."


id: 7367c9a2a235cc3d82331f00eb316677
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17559
content:
"Currently, around four billion people live under conditions of severe \r\nfreshwater scarcity for at least one month of the year, with half \r\na  billion people in the world facing severe water scarcity all year \r\nround (Mekonnen and Hoekstra, 2016). The AR5 WGII reported that \r\napproximately 80% of the world's population already suffers from \r\nhigh levels of threat to water security (Jimenez Cisneros et al., 2014). \r\nGiven the vulnerability of the planet's freshwater resources and the \r\nrole of climate change in intensifying adverse impacts on human \r\nsocieties and ecosystems (Hoegh-Guldberg et al., 2018; IPCC, 2018), \r\nthis chapter evaluates advances in the theoretical, observational and \r\nmodel based understanding of the global water cycle made since AR5 \r\n(IPCC, 2013) and AR6 Special Reports."


id: e71be16055a0d174fa64d452c836ca34
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37957
content:
"Water scarcity occurs when there are insufficient freshwater resources \r\nto meet water demands, although water problems may also arise \r\nfrom water quality issues or from economic and institutional barriers \r\n(AR6 WGII Chapter 4). This affects the preservation of environmental \r\nflows that ultimately influence ecosystem functioning and services \r\n(Schewe et al., 2014; Mekonnen and Hoekstra, 2016; Djehdian \r\net al., 2019). As such, water availability is a  major constraint on \r\nhuman society's ability to meet the future food and energy needs of \r\na growing population (D'Odorico et al., 2018). Water plays a key role \r\nin the production of energy, including hydro-electricity, bioenergy, "


id: bc205e922fcdcecfd61822d08eb86aed
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30338
content:
"As shown in Figure  8.1, the global water cycle is the continuous, \r\nnaturally occurring movement of water through the climate system \r\nfrom its liquid, solid and gaseous forms among reservoirs of the \r\nocean, atmosphere, cryosphere and land (Stocker et al., 2013). \r\nIn the atmosphere, water primarily occurs as a gas (water vapour), \r\nbut it is also present as ice and liquid water within clouds where \r\nit substantially affects Earth's energy balance (Sections  7.4.2.2 \r\nand 7.4.2.4). The water cycle primarily involves the evaporation1"


id: ba0a58ba47fc1588abee18f99c3b0629
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29953
content:
"and precipitation of moisture at the Earth's surface including \r\ntranspiration associated with biological processes. Water that falls on \r\nland as precipitation, supplying soil moisture, groundwater recharge, \r\nand river flows, was once evaporated from the ocean or sublimated \r\nfrom ice-covered regions before being transported through the \r\natmosphere as water vapour, or in some areas was generated over \r\nland through evapotranspiration (Gimeno et al., 2010; van der Ent \r\nand Savenije, 2013). In addition, the net flux of atmospheric and \r\ncontinental freshwater is a key driver of sea surface salinity, which in \r\nturn influences the density and circulation of the ocean (Chapter 9). "


id: b0365468fad890bf769f56596dcc477e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28237
content:
"This section summarizes observed and projected water cycle changes \r\nreported in AR5 (IPCC, 2013) and in the recent IPCC Special Reports \r\non Global Warming of 1.5degC (SR1.5), the Ocean and Cryosphere in \r\na Changing Climate (SROCC), and Climate Change and Land (SRCCL). "


id: 28b173f259cdd2c8db0ef16d850516c4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4374
content:
"This Report is the first IPCC assessment to include a chapter specifically \r\ndedicated to providing an integrated assessment of the global water \r\ncycle changes, by building on many chapters from previous reports. "


id: e024b91cc88d45c201db5b7bac35f81
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36684
content:
"medium confidence under the RCP8.5 scenario (Section 12.4.5.3). \r\nSoil moisture drying in the Mediterranean, south-west USA \r\nand southern African regions was considered likely, with high \r\nconfidence by the end of this century under the RCP8.5 scenario \r\n(Section  12.4.5.3). Projections for annual runoff included both \r\ndecreases and increases. Decreases in Northern Hemisphere snow \r\ncover were assessed as very likely with continued global warming \r\n(Section  12.4.6.2). As temperatures increase, snow accumulation \r\nwas projected to begin later in the year and melting to start earlier, \r\nwith related changes in snowmelt-driven river flows (FAQ 12.2 and \r\nSection 12.4.6.2 in AR5 WGI). In terms of the potential for abrupt \r\nchange in components of the water cycle, long-term droughts and \r\nmonsoonal circulation were identified as potentially undergoing \r\nrapid changes, but the assessment was reported with low \r\nconfidence (Sections 12.5.5.8.1 and 12.5.5.8.2, and Table 12.4)."


id: 2acbc816b68db6f567c93bbdef96151b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4758
content:
"low-elevation snow cover is also projected to decrease, regardless \r\nof emissions scenario. Widespread permafrost thaw is projected to \r\ncontinue through this century and beyond. River runoff in snow- or \r\nglacier-fed basins is projected to increase in winter and to decrease in \r\nsummer (and in the annual mean) by 2100. In the oceans, the Atlantic \r\nMeridional Overturning Circulation (AMOC) will very likely weaken \r\nover the 21st century under all emissions scenarios (SROCC), with \r\npotential effects on atmospheric circulation and the water cycle at \r\nthe regional scale (see also Section 8.6)."


id: 84350322b2ef807247b9dfa3d10a1be2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20414
content:
"The Special Report on the Ocean and Cryosphere in a  Changing \r\nClimate (SROCC) provides a comprehensive assessment of recent and \r\nprojected changes, specifically in snow and ice-covered areas that \r\nform a key component of the water cycle in high-elevation and high\u0002latitude areas. High mountain regions have experienced significant \r\nwarming since the early 20th century, resulting in reduced snowpack \r\non average (Marty et al., 2017), with glaciers retreating globally \r\nsince the mid-20th century (Marzeion et al., 2018; Zemp et al., 2019). \r\nGlacier shrinkage and snow cover changes have led to changes \r\n(both increases and decreases) in streamflow in many mountain \r\nregions in recent decades (Milner et al., 2017). Permafrost regions \r\nhave undergone degradation and ground-ice loss due to recent \r\nwarming (Lu et al., 2017). Glacier mass loss is projected to continue \r\nthrough the 21st century under all scenarios. In high mountain areas, "


id: 248523a04546ac471954ee68421ad56f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 3615
content:
"This chapter assesses water cycle changes and considers climate \r\nchange from the perspective of its effects on water availability \r\n(including streamflow and soil moisture, snow mass and glaciers, \r\ngroundwater, wetlands and lakes) rather than only precipitation. \r\nThe chapter highlights the sensitivity of the water cycle to multiple \r\ndrivers and the complexity of its responses, depending on regions, \r\nseasons and time scales. Anthropogenic drivers include not only \r\nemissions of GHGs but also different species of aerosols, land and \r\nwater management practices. Emphasis is placed on assessing the \r\nfull range of projections, including 'low likelihood, high impact' \r\nclimate trajectories such as the potential for abrupt changes in the \r\nwater cycle."


id: 85580c5ae677b1469daa0cd7827d310b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20597
content:
"high-impact scenarios are also assessed, especially the potential \r\nfor abrupt climate change (Section 8.6). Final remarks about future \r\nstudies on water cycle changes (Section 8.7) are also provided, and \r\nthe chapter addresses three frequently asked questions (FAQs) on the \r\nwater cycle's sensitivity to land use change (FAQ 8.1), the projected \r\noccurrence and severity of floods (FAQ 8.2) and droughts (FAQ 8.3) at \r\nthe global scale. This chapter outline is summarized with a schematic \r\n(Figure  8.2) which also provides a  quick guide to the main topics \r\naddressed across the different sections."


id: 7c23feef878114ed0888ac8c2bce5855
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19051
content:
"on regional water cycle changes can be found in Chapters 10 to 12 \r\nand in the Atlas. The reader is also referred to the interactive Atlas \r\nfor a  more detailed assessment of the range of model biases and \r\nresponses at the regional scale. Beyond WGI, water is also a major \r\ntopic for both adaptation and mitigation policies so has strong \r\nconnections with both WGII and WGIII. Assessment of hydrological \r\nimpacts at basin and catchment scales, including a broader discussion \r\non adaptation and vulnerability, potential threats to water security, \r\nsocietal responses, improving resilience in water systems and related \r\ncase studies is provided in WGII (Chapter 4)."


id: 1a0552451c2053907679a8a8206b6aa1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1775
content:
"as the climate warms (Pendergrass and Hartmann, 2014b; Doll et al., \r\n2018). Future water availability is also determined by changes in \r\nevaporation, which is driven by a general increase in the atmospheric \r\nevaporative demand (Scheff and Frierson, 2014) and modulated by \r\nvegetation controls on evaporative losses (Milly and Dunne, 2016; \r\nLemordant et al., 2018; Vicente-Serrano et al., 2020). At regional \r\nscales, water cycle changes result from the interplay between \r\nmultiple potential drivers (CO2, aerosols, land use change and human \r\nwater use; Section 8.2.3). This section assesses advances in physical \r\nunderstanding of global to regional drivers of water cycle changes."


id: c102464f45d836963fd9beb1ccbd32d3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31259
content:
"The Clausius-Clapeyron equation determines that low-altitude \r\nspecific humidity increases by about 7% degC-1 of warming, assuming \r\nthat relative humidity remains constant, which is approximately \r\ntrue at a  global scale but not necessarily valid regionally. It is \r\nvery likely that near surface specific humidity has increased since \r\nthe 1970s (Section  2.3.1) and total atmospheric water vapour \r\ncontent (precipitable water) is very likely to increase at close to \r\na thermodynamic rate on average globally with continued warming. \r\nDifferent radiative forcing mechanisms lead to some variation in \r\nthe global mean thermodynamic response by altering the relative "


id: bcba91a3efe12cc480f94cddd5433fce
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30451
content:
"It is well understood that global precipitation and evaporation \r\nchanges are determined by Earth's energy balance (Section 8.2.1). \r\nAt regional scales smaller than about 4000 km, water cycle changes \r\nbecome dominated by the transport of moisture (Dagan et al., \r\n2019a; Jakob et al., 2019; Dagan and Stier, 2020), which depend \r\non both thermodynamic and dynamical processes (Section  8.2.2). \r\nThe constraints of energy budgets at global scales and moisture \r\nbudgets at regional scales cause key water cycle characteristics \r\nsuch as precipitation intensity, duration and intermittence to alter "


id: e4f84b1379f1931a46e189e2e2900a25
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37578
content:
"humidity distribution: the rate of global precipitable water increase \r\nwith global surface temperature ranges2 from 6.4 +- 1.5% degC-1 for \r\nsulphate aerosol-induced changes to 9.8 +-  3.3%  degC-1 for black \r\ncarbon-induced changes based on idealized modelling (Hodnebrog \r\net al., 2019b). Specific humidity increases at a  lower rate over \r\nland due to decreasing relative humidity (Collins et al., 2013) \r\nas corroborated by observations and simple models (Byrne and \r\nO'Gorman, 2018). Prevalent increases in atmospheric water vapour \r\ndrive powerful amplifying feedbacks (Section  7.4.2.2), intensify \r\natmospheric moisture transport and heavy precipitation events \r\n(Section  8.2.3.2), and alter the surface and atmospheric energy \r\nbalance, thereby influencing global evaporation and precipitation \r\nchanges (Figure 8.3)."


id: ef67654542b4adbbdeed83a04af55567
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39488
content:
"controlled by thermal deepening of the troposphere (Jeevanjee and \r\nRomps, 2018) and limited by surface evaporation and consequent \r\natmospheric latent heat release and warming (Webb et al., 2018). \r\nClimate feedbacks (e.g., temperature lapse rate and clouds) that vary \r\nacross models (Sections 7.4 and 3.8.2) also modulate the magnitude \r\nof e (O'Gorman et al., 2012; Flaschner et al., 2016; T.B. Richardson \r\net al., 2018a). Uncertainty in e  across CMIP5 models relating to \r\ndeficiencies in representing low-altitude cloud feedbacks (Watanabe \r\net al., 2018) and absorption of shortwave radiation by atmospheric \r\nwater vapour (DeAngelis et al., 2015) do not apply well to CMIP6 \r\nsimulations, the latter improvement explained by more accurate \r\nradiative transfer modelling (Pendergrass, 2020b)."


id: f9e7fa750be4f336aa5d2fc1aa5943a2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41330
content:
"Hydrological sensitivity (e) is defined as the linear change in \r\nglobal mean precipitation with global surface air temperature \r\n(GSAT) once rapid adjustments of the hydrological cycle to radiative \r\nforcings have occurred (Figure 8.3a). There is robust understanding \r\nand high agreement across idealized CO2 forcing CMIP5 and CMIP6 \r\nexperiments (Flaschner et al., 2016; Samset et al., 2018b; Pendergrass, \r\n2020b) that e  = 2.1-3.1%  degC-1 (Figure  8.4). The magnitude of \r\ne depends primarily on atmospheric net radiative cooling which is "


id: 808d0e771a70e8017214cbc0e721aa7f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19744
content:
"The fast and slow precipitation responses over global land combine \r\non average during transient climate change (Figure  8.3d). This \r\nexplains a  consistent land and ocean mean precipitation increase \r\nin projections (Table 4.3) but this is determined by a complex and \r\nmodel-dependent evolution of continental water cycle changes over \r\nspace and time."


id: 538ee6fde32b17921e58a25a6a0d3033
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11974
content:
"Increases in global precipitation over time, as the climate warms, are \r\npartly offset by the overall cooling effects of anthropogenic aerosol \r\nand by rapid atmospheric adjustments to increases in GHGs and \r\nabsorbing aerosol. This explains why multi-decadal trends in global \r\nprecipitation responses in the satellite era (Adler et al., 2017; Allan \r\net al., 2020) are small and difficult to interpret given observational \r\nuncertainty, internal variability and volcanic forcings. The delayed \r\nwarming effect of rising CO2 concentration, combined with declining \r\naerosol cooling, are expected to increase the importance of the slow \r\ntemperature-related effects on the energy budget relative to the \r\nmore rapid direct radiative forcing effects as transient climate change \r\nprogresses (Shine et al., 2015; Salzmann, 2016; Myhre et al., 2018b). "


id: d2d057bf149fa4da3d9aed65eb27283e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34438
content:
"A warming climate drives increases in atmospheric moisture and \r\nhorizontal moisture transport from the divergent to the convergent \r\nportions of the atmospheric circulation (including storm systems, \r\nthe tropical rain belt and monsoons) that on average amplifies \r\nexisting precipitation minus evaporation (P-E) patterns (Held and \r\nSoden, 2006). Increased latent heat transports in high latitudes \r\nalso contribute to polar amplification of warming (Section 7.4.4.1). \r\nAlthough convergent parts of the atmospheric circulation are \r\nexpected to become wetter (in terms of increasing P-E) and net \r\nevaporative regions drier (increasing E-P) these regions are not \r\ngeographically and seasonally fixed and their location and timing "


id: b9a43a098c9e95e0cfdb51aa81a9fedf
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29871
content:
"layer adjustments and ocean heat uptake playing a  secondary \r\nrole, based on idealized modelling (Siler et al., 2019). Increased \r\nevaporation from warmer oceans and lakes is exacerbated by the \r\nloss of surface ice in some regions (Bintanja and Selten, 2014; Laine \r\net al., 2014; W. Wang et al., 2018; Sharma et al., 2019; Woolway \r\net al., 2020). This can generate a  more local moisture source for \r\nprecipitation, for example in north-west Greenland during non\u0002summer months since the 1980s (Nusbaumer et al., 2019), though \r\nmoisture transport changes can counteract this effect (Nygard \r\net al., 2020). Ocean stratification due to heating of the upper layers \r\nthrough radiative forcing has been identified as a mechanism that \r\nfurther amplifies surface salinity patterns beyond the responses \r\ndriven by water cycle changes alone (Zika et al., 2018). "


id: d9f914eef2fef16cc4e7743b0dceaeee
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 35648
content:
"are expected to alter (Section  8.2.2.2). Atmospheric and ocean \r\ncirculation changes overall decrease the amplification of P-E \r\nand salinity patterns. Paleoclimate evidence confirms that during \r\nthe LGM zonal mean changes were roughly in agreement with \r\nthermodynamic expectations (G. Li et al., 2013). However regional \r\nchanges can be dominated by dynamics, including responses to the \r\nlarge Northern Hemisphere (NH) ice sheets (DiNezio and Tierney, \r\n2013; T.  Bhattacharya et al., 2017; Scheff et al., 2017; D'Agostino \r\net al., 2019; Lowry and Morrill, 2019) such that altered P-E patterns \r\nare not well described by thermodynamic drivers (Oster et al., 2015; \r\nLora, 2018; Morrill et al., 2018)."


id: e04e118fb00ae6e333d06c84c83ec469
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36713
content:
"The strong physical basis for regionally and seasonally dependent \r\nresponses of P-E and the expectation for an increasing contrast \r\nbetween wet and dry seasons and weather regimes is supported \r\nby high agreement across multiple observational and CMIP5/CMIP6 \r\nmodelling studies (Liu and Allan, 2013; Kumar et al., 2015; Polson \r\nand Hegerl, 2017; Ficklin et al., 2019; Deng et al., 2020; Schurer \r\net al., 2020). Increased moisture transports into storm systems, \r\nmonsoons and high latitudes increase the intensity of wet events \r\n(Section  8.2.3.2), while stronger atmospheric evaporative demand \r\nwith warming (Scheff and Frierson, 2014; Vicente-Serrano et al., \r\n2018; Cook et al., 2019) is an important mechanism for intensifying \r\ndry events (Section  8.2.3.3) and decreasing soil moisture over "


id: 99380093d98aebe4b37f34841ee0cae4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 24170
content:
"There is robust evidence and high agreement across thermodynamics, \r\ndetailed modelling and observations that amplification of P-E \r\npatterns occurs over the oceans (Figure  8.5a) with an associated \r\n'fresh gets fresher, salty gets saltier' signature in ocean salinity \r\n(Sections  2.3.3.2 and 3.5.2). This amplification is moderated by \r\nproportionally larger increases in subtropical ocean evaporation \r\nand weakening of the tropical circulation (Section  8.2.2.2), an \r\nexpectation supported by observations (Skliris et al., 2016) and \r\nprocess understanding (Yang and Roderick, 2019). Thermodynamics \r\nexplain a smaller low latitude evaporation increase (1% degC-1) than in \r\nhigh latitudes (5% degC-1) with changes in surface radiation, boundary "


id: 484b31a7f9295eb085606b191d9c25b2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9931
content:
"many subtropical land regions. However, aridification is modulated \r\nregionally by poleward migration of the subtropical dry zones and \r\nan increasing land-ocean temperature contrast that drives declining \r\nrelative humidity (Section 8.2.2.2)."


id: 87449a0fe47f76eeed3ba8fadbc7fd50
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20958
content:
"To summarize, increased moisture transport from evaporative oceans \r\nto high precipitation regions of the atmospheric circulation will drive \r\namplified P-E and salinity patterns over the ocean (high confidence) \r\nwhile more complex regional changes are expected over land. \r\nGreater warming over land than ocean alters atmospheric circulation \r\npatterns and on average reduces continental near-surface relative \r\nhumidity which along with vegetation feedbacks can contribute to \r\nregional decreases in precipitation (high confidence). Based on an \r\nimproved understanding of thermodynamic drivers since AR5 and \r\nmultiple lines of evidence, there is high confidence that very wet or \r\ndry seasons and weather patterns will intensify in a warming climate \r\nsuch that wet spells become wetter and dry spells drier."


id: 625b20900064d20945280db2109a5df
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14585
content:
"Model simulations show a stronger Pacific Walker circulation during \r\nthe LGM in response to a cooler climate (consistent with an expected \r\nweakening in a warmer climate), but a weaker Indian Ocean east-\r\nwest circulation in response to the exposure of the Sunda and Sahul \r\nshelves due to lowered sea level (DiNezio et al., 2011). The latter \r\neffect is detectable in proxies for hydroclimate, as well as salinity and \r\nsea surface temperature (DiNezio and Tierney, 2013; DiNezio et al., \r\n2018). More relevant to future warming is the mid-Pliocene period \r\n(3 million years ago), the last time the Earth experienced CO2 levels \r\ncomparable to present (see Cross-Chapter Box  2.4). Sea surface \r\ntemperature (SST) reconstructions show a weakening of the Pacific \r\nzonal gradient and a  pattern of warmth consistent with a  weaker \r\nWalker cycle response (Corvec and Fletcher, 2017; Tierney et al., 2019; "


id: 2bfeaeb50d2bdaa0129c6fcf6c63343e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4991
content:
"Responses of the large-scale atmospheric circulation to a  warming \r\nclimate are not as well understood as thermodynamic drivers \r\n(Shepherd, 2014). The AR5 identified robust features including \r\na  weakening and broadening of tropical circulation with poleward \r\nmovement of tropical dry zones and mid-latitude jets (Collins et al., "


id: 764e915b6c44a12c78f7ba2ca14a1280
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18035
content:
"(Section 8.4.2.1) with limited evidence of distinct regional responses \r\nto GHG forcing including a northward shift over eastern Africa and the \r\nIndian Ocean and a southward shift in the eastern Pacific and Atlantic \r\noceans (Mamalakis et al., 2021). Paleoclimate evidence highlights the \r\ndistinct regional ITCZ responses to hemispheric asymmetry in volcanic \r\nand orbital forcing (McGee et al., 2014; Boos and Korty, 2016; Colose \r\net al., 2016; Denniston et al., 2016; PAGES Hydro2K Consortium, 2017; \r\nSingarayer et al., 2017; Atwood et al., 2020) and rapid (>1deg latitude \r\nover decades) shifts in the ITCZ and regional monsoons in response to \r\nAMOC collapse cannot be ruled out (Sections 8.6.1.1 and 5.1.3)."


id: 8627b967e1ffd4940c3da3f4a5a7e8da
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20754
content:
"McClymont et al., 2020). Although the Pliocene SST pattern and wet \r\nsubtropics contrast with present conditions (Burls and Fedorov, \r\n2017), the paleoclimate record strengthens evidence that a warmer \r\nclimate is associated with a weaker Walker circulation (Cross-Chapter \r\nBox 2.4; Section 3.3.3)."


id: ddf91f538dcbe50f9f5a3afe4a5b0527
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36316
content:
"Since AR5, weakening of the tropical circulation has been explained \r\nas a  rapid response to increasing CO2 concentrations and slower \r\nresponse to warming and evolving SST patterns (He and Soden, 2017; \r\nXia and Huang, 2017; Shaw and Tan, 2018; Chemke and Polvani, 2020). \r\nLarge-scale tropical circulation weakens by 3-4% in a rapid response \r\nto a quadrupling of CO2 concentrations (Plesca et al., 2018), which \r\nsuppresses tropospheric radiative cooling, particularly in subtropical \r\nocean subsidence regions (Bony et al., 2013; Merlis, 2015; Richardson \r\net al., 2016). The resulting increased atmospheric stability explains \r\nthe rapid weakening of the Walker circulation (Wills et al., 2017) \r\nand Northern Hemisphere Hadley Cell (Chemke and Polvani, 2020). \r\nSubsequent surface warming contributes up to a  12% slowing of \r\ncirculation for a uniform 4degC SST increase, driven by thermodynamic \r\ndecreases in temperature lapse rate (Plesca et al., 2018)."


id: 1da18d9c3459a80861ecd8945c7f6c85
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2397
content:
"surface and subsurface, including cryosphere and biosphere \r\ninteractions and the direct impacts of human activities."


id: 5515b1f7c492dcc2d41e3f608ae61661
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12243
content:
"weaker Northern Hemisphere expansion in response to GHG forcing \r\nis modulated by tropospheric ozone and aerosol forcing, particularly \r\nblack carbon (Davis et al., 2016; Grise et al., 2019; Watt-Meyer \r\net al., 2019; Zhao et al., 2020). However, internal variability is found \r\nto dominate observed responses in the NH, precluding attribution to \r\nradiative forcing (D'Agostino et al., 2020a). Paleoclimate evidence \r\nof poleward expansion and weakening of westerly winds in both \r\nhemispheres in the warmer Pliocene is linked to reduced equator-to\u0002pole thermal gradients and ice volume (Abell et al., 2021)."


id: 660796ab2b0f8ca96f80a9930d44a335
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15208
content:
"Reductions in snow, freshwater ice and permafrost affect terrestrial \r\nhydrology. Permafrost degradation reduces soil ice and alters the \r\nextent of thermokarst lake coverage (Section  9.5.2; M.  Meredith "


id: efc096da9bc0b6f70b0c0036911e0c4e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39566
content:
"Processes operating at local scales are capable of substantially \r\nmodifying the regional water cycle. This section assesses the \r\ndevelopment in understanding of processes affecting the atmosphere, "


id: 46457e6f2e31b7689521e94125b40bcb
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9582
content:
"et al., 2019). A lag between current climate change and permafrost \r\ndegradation is expected, given the slow response rates in frozen \r\nground and the fact that snow cover insulates soil from sensible heat \r\nexchanges with the air above (Hoegh-Guldberg et al., 2018; Garcia\u0002Garcia et al., 2019; Soong et al., 2020). Post-wildfire areas are also \r\nlinked with permafrost degradation in the Arctic based on satellite \r\nobservations (Yanagiya and Furuya, 2020). An increase in spring \r\nrainfall can increase heat advection by infiltration, exacerbating \r\npermafrost thaw and leading to increased methane emissions \r\n(Section  5.4.7; Neumann et al., 2019). Increased heat transport \r\nby Arctic rivers can also contribute to earlier sea ice melt (Park \r\net al., 2020)."


id: ff51f23059a03de87c31a45b38f62dc2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 42327
content:
"In summary, it is virtually certain that warming will cause a loss of \r\nfrozen water stores, except in areas where temperatures remain \r\nbelow 0degC for most of the year. There is high confidence that warming \r\nand reduced snow volume drives an earlier snowmelt, leading to \r\nseasonally dependent changes in streamflow. There is medium \r\nconfidence that weaker sunlight earlier in the season can reduce \r\nthe rate of snowmelt. Melting of snowpack or glaciers can increase \r\nstreamflow in high-latitude and high-altitude catchments until \r\nfrozen water reserves are depleted (high confidence). There is high \r\nconfidence that warm, moist airflows and associated precipitation \r\ndominate glacier mass balance in some regions (New Zealand, \r\nGreenland, Antarctica)."


id: aea8ba74db6d6428dc23454c35fc0426
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27963
content:
"Since AR5, advances in understanding the expected changes in \r\nintense rainfall at the sub-daily time scale (Section 11.4, Figure 8.4) \r\nare provided by idealized or high resolution model experiments and \r\nobservations (Westra et al., 2014; Fowler et al., 2021). There is robust "


id: 84c3ec490eccda6bcd93cc872c6e513c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20503
content:
"depends on the moisture-convergence regime (Welty et al., 2020). Only \r\nhigh-resolution convection-permitting models can capture the sub-grid \r\nscale mechanisms for convective initiation (C.M. Taylor et al., 2013; \r\nH. Moon et al., 2019). There is medium evidence that greater tropical \r\ncyclone rainfall totals can be caused by dynamical feedbacks (Chauvin \r\net al., 2017) and slower propagation speed as tropical circulation \r\nweakens (Kossin, 2018). These processes amplify the thermodynamic \r\nintensification of rainfall (Section 11.7.1.2), yet observational support \r\nis weak (Chan, 2019; Lanzante, 2019; I.J. Moon et al., 2019; Knutson \r\net al., 2020). Slower decay following landfall, explained by larger stores \r\nof heat and moisture at higher SSTs, can also amplify rainfall amount \r\nbased on observations and modelling (Li and Chakraborty, 2020). \r\nRainfall intensity from the outer rain bands of tropical cyclones is also \r\nincreased by aerosol-cloud interactions (Box 8.1)."


id: 71d7732bba98394fa7d765a8860ba319
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17270
content:
"et al., 2018). More intense but less frequent storms (Kendon et al., \r\n2019) favour focused groundwater recharge through leakage from \r\nsurface waters (R.G. Taylor et al., 2013a; Cuthbert et al., 2019a) and \r\nrunoff and flash flooding where the percolation capacity of the soil is \r\nexceeded (Yin et al., 2018). "


id: 956dc6136904b58f15625092c34fded3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 23493
content:
"Increased severity of flooding on larger, more slowly-responding rivers \r\nis expected as precipitation accumulations increase during persistent \r\nwet events over a season. This can occur where atmospheric blocking \r\npatterns repeatedly steer extratropical cyclones across large river \r\ncatchments, as identified for NH mid-latitudes and Asia (Takahashi \r\net al., 2015; Pfleiderer et al., 2018; Zhou et al., 2018; Bloschl et al., \r\n2019; Lenggenhager et al., 2019; Nikumbh et al., 2019; Zanardo et al., \r\n2019), although groundwater flooding and antecedent conditions \r\nincluding soil moisture and snowmelt also play a  role (Muchan \r\net al., 2015; Berghuijs et al., 2019). Increased atmospheric moisture \r\namplifies the severity of these events when they occur in a warmer \r\nclimate, yet drivers of change in the occurrence of blocking patterns, \r\nstationary waves and jet stream position are not well understood \r\n(Section 8.2.2.2 and Cross-Chapter Box 10.1). "


id: 7e948aa1dcf82e6ce4d715158d54a48
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19422
content:
"Vegetation is a crucial interface between subsurface water storage \r\n(in soil moisture and groundwater) and the atmosphere. Plants \r\nalter evapotranspiration and the surface energy balance, and \r\nthus can have a  large influence on regional aridity (Lemordant \r\net al., 2018). SRCCL concluded there is high confidence that higher \r\natmospheric CO2 increases the ratio of plant CO2 uptake to water \r\nloss (water-use efficiency; WUE) through the combined enhancement \r\nof photosynthesis and stomatal regulation (Section 5.4.1; De Kauwe \r\net al., 2013; C.D. Jones et al., 2013; Deryng et al., 2016; Swann et al., "


id: 8c49286f5e68fad9d5d71d9479bd6714
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 21857
content:
"2016; Cheng et al., 2017; Knauer et al., 2017; Peters et al., 2018; \r\nGuerrieri et al., 2019). Modelling studies suggest that increasing \r\nWUE can partly counteract water losses from increased evaporative \r\ndemand in a warmer atmosphere, potentially mitigating aridification \r\n(Milly and Dunne, 2016; Bonfils et al., 2017; Cook et al., 2018; Y. Yang \r\net al., 2018). However, observational studies suggest that this effect \r\nmay be counter-balanced by the increase in plant growth in response \r\nto elevated CO2, which results in increased water consumption \r\n(De Kauwe et al., 2013; Donohue et al., 2013; Ukkola et al., 2016b; "


id: 2d0652759a24e224e6d0192adcf0da94
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5193
content:
"Figure 8.6 | Climatic drivers of drought, effects on water availability, and impacts. Plus and minus signs denote the direction of change that drivers have on factors \r\nsuch as snowpack, evapotranspiration, soil moisture, and water storage. The three main types of drought are listed, along with some possible environmental and socio-economic \r\nimpacts of drought (bottom). "


id: e1c487a438fd36ab0441e747100e776
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36997
content:
"Yang et al., 2016; Guerrieri et al., 2019; Mankin et al., 2019; A. Singh \r\net al., 2020). In semi-arid regions, increased plant water consumption \r\ncan reduce streamflow and exacerbate aridification (Ukkola et al., \r\n2016b; Mankin et al., 2019; A.  Singh et al., 2020). Thus, there is \r\nlow confidence that increased WUE in plants can counterbalance \r\nincreased evaporative demand (Cross-Chapter Box 5.1)."


id: 78894d26c7444df591deabbe98938f9e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18406
content:
"In summary, there is high confidence that a warming climate drives \r\nan increase in atmospheric evaporative demand, decreasing available \r\nsoil moisture. There is high confidence  that higher atmospheric \r\nCO2 increases plant water-use efficiency, but low confidence that \r\nthis physiological effect can counterbalance water losses. Since \r\ndrought can be defined in a number of ways, there are potentially \r\ndifferent responses under a warming climate depending on drought \r\ntype. Beyond a lack of precipitation, changes in evapotranspiration \r\nare critical components of drought, because these can lead to soil \r\nmoisture declines (high confidence). Under very dry soil conditions, \r\nevapotranspiration becomes restricted and plants experience water \r\nstress in response to increased atmospheric demand (medium \r\nconfidence). Human activities and decision-making have a  critical \r\nimpact on drought severity (high confidence)."


id: d5ee432f4794ff83420cf7c007dd916f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34954
content:
"Drought severity also depends on human activities and decision\u0002making (AghaKouchak et al., 2015; Van Loon et al., 2016; Pendergrass "


id: e88d700014068b708b6cdad9381f38ab
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38251
content:
"In summary, there is high confidence that land-use change and \r\nwater extraction for irrigation drive local, regional and remote \r\nresponses in the water cycle. Large-scale deforestation is likely to \r\ndecrease precipitation over the deforested regions but there is low \r\nconfidence in the effects of limited deforestation. There is medium \r\nconfidence that deforestation drives increased streamflow relative to \r\nthe responses caused by climate change. Urbanization can increase \r\nlocal precipitation (medium confidence) and resulting runoff intensity \r\n(high confidence). A warming climate combined with direct human \r\ndemand for water is expected to deplete groundwater resources in \r\ndry regions (high confidence)."


id: 5b282b6f36769bc1de24b7290f4faaf9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 13288
content:
"Aerosols affect precipitation in two major pathways, by altering the shortwave and longwave radiation and influencing cloud \r\nmicrophysical properties."


id: 7224ae3be5acff06ea977fff759501f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17326
content:
"Aerosols scatter and absorb solar radiation which reduces the energy available for surface evaporation and subsequent precipitation. \r\nIn addition, cooling is incurred by the radiation that is reflected back to space directly by the aerosols and indirectly by the aerosol \r\neffect on cloud brightening. Northern Hemisphere (NH) station data indicate decreasing precipitation trends during the 1950s to the \r\n1980s, which have since partially recovered (Wild, 2012; Bonfils et al., 2020). These changes are attributable with high confidence\r\nto anthropogenic aerosol emissions from North America and Europe causing dimming through reduced surface solar radiation. "


id: 4c99fce119085e862abb3fe252ad9738
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10741
content:
"This peaked during the late-1970s and partially recovered thereafter following improved air quality regulations (Section  6.2.1; \r\nBox 8.1, Figure 1)."


id: e1d384865858eba95354127774430b56
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37009
content:
"Absorption of solar radiation by anthropogenic aerosols such as black carbon warms the lower troposphere and increases moist \r\nstatic energy, but also results in larger convection inhibition that suppresses light rainfall (Box 8.1, Figure 2; Y. Wang et al., 2013). \r\nRelease of aerosol-induced instability, often triggered by topographical barriers, produces intense rainfall, flooding (Fan et al., 2015; "


id: f53e5368bc43ad526cf6f1f6d625295c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40516
content:
"Lee et al., 2016) and severe convective storms (medium confidence) (Saide et al., 2015). In particular, aerosols induce intense convection \r\nat the Himalaya foothills during the pre-monsoon season, which generates a  regional convergence there (medium confidence).\r\nThis mechanism is termed the 'elevated heat pump hypothesis' (Lau and Kim, 2006; D'Errico et al., 2015)."


id: 7daab3310204c971dc5ebae75521526b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19281
content:
"(Abbott and Cronin, 2021). In addition, delaying rain initiation until greater altitudes are reached transports more cloud water above \r\nthe 0degC altitude and leads to additional release of latent heat of freezing and/or vapour deposition, which in combination with the \r\nadded latent heat of condensation enhances the cloud updrafts (Fan et al., 2018). The stronger updrafts invigorate mixed-phase \r\nprecipitation and the resultant hail and cloud electrification (Rosenfeld et al., 2008; Thornton et al., 2017). This includes the outer \r\nconvective rainbands of tropical cyclones. There is medium confidence that air pollution enhances flood hazard associated with the \r\nouter rain bands at the expense of the inner rain bands (Wang et al., 2014; C. Zhao et al., 2018; Souri et al., 2020)."


id: eb622fe0dc358193a715f886ab41991d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38766
content:
"The aerosol effect on invigoration and rainfall from deep convective clouds peaks at moderate levels (aerosol optical depth of 0.2 to 0.3), \r\nbut reverses into suppression with more aerosols (H. Liu et al., 2019). More generally, the microphysical aerosol-related processes \r\noften compensate or buffer each other (Stevens and Feingold, 2009). For example, suppressed rain by slowing drop coalescence \r\nenhances mixed-phase precipitation. Therefore, despite the potentially large aerosol influence on the precipitation forming processes, \r\nthe net outcome of aerosol microphysical effects on precipitation amount has generally low confidence, especially when evaluated \r\nwith respect to the background of high natural variability in precipitation (Tao et al., 2012)."


id: 6cb22675f888fe757d93a53dd686048c
created_at: 2023-04-19 13:21:37
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index: climate_gpt_v2
vector_id: 16408
content:
"The human influence on the global water cycle is often summarized \r\nas an intensification (Huntington, 2006; DeAngelis et al., 2015; \r\nW. Zhang et al., 2019b) or an overall strengthening which has been \r\nobserved since at least 1980 (high confidence) (see Chapter 2). There \r\nis, however, no unique definition of the global water cycle intensity \r\n(Trenberth, 2011; Ficklin et al., 2019; Sprenger et al., 2019). One \r\nsimple metric is the global and annual mean amount of precipitation. \r\nAlthough an increase in global precipitation is consistent with \r\nphysical expectations (Section 8.2.1), it has not yet been detected and \r\nattributed to human activities given large observational uncertainties \r\nand low signal-to-noise ratio (Section  3.3.2.2). Other metrics are \r\nmore suitable to detect and attribute changes in the global water \r\ncycle, including the likely increase in global land precipitation since \r\n1950 (Section  2.3.1.4) which is likely due to a  human influence \r\n(Section 3.3.2.3)."


id: 135645829aabf90ca5614a72da589217
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 613
content:
"The flux of freshwater between the ocean and atmosphere is \r\ndetermined by the difference between precipitation and evaporation \r\n(P-E). Evaporation is measured in very few locations across the \r\nglobal ocean, so that directly assessing P-E over the ocean is very \r\nchallenging and relies on indirect reanalysis estimates (Robertson \r\net al., 2020). The AR5 presented robust evidence of an amplified\r\noceanic pattern in P-E since the 1960s from both regional and \r\nglobal surface and subsurface salinity measurements and reanalyses. "


id: 5738dd81b43da4b44aff5c5b5b5ade40
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12599
content:
"This section provides a process-based evaluation and a comprehensive \r\nassessment of observed water cycle changes by integrating multiple \r\nlines of evidence including paleoclimate data, historical datasets, \r\ntheoretical understanding (Section 8.2) and model simulations."


id: e5c1d14da223d07d27bf206ce056472e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37728
content:
"This  pattern is consistent with our theoretical understanding of \r\nhuman-induced changes in the water cycle, leading to the conclusion \r\nthat these changes are very likely the result of anthropogenic forcings \r\n(Section 9.2.2.2). "


id: a2639d183a17f8298a3f4fcc5daab53d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 25790
content:
"In contrast, AR5 did not provide a  conclusive assessment of \r\nobserved changes in P-E over land. Continental P-E estimated \r\nfrom reanalyses and data-driven land surface models indicate that \r\ninterannual variations are linked to ENSO (Robertson et al., 2014, \r\n2020). Increasing trends in P-E since 1979 based on land models are \r\nnot statistically significant. Observations and models show evidence \r\nthat P-E increases in the wet parts and decreases in the dry parts \r\nof tropical circulation systems, which shift in location seasonally \r\nand from year to year, with increases in seasonality since 1979 (see \r\nBox 8.2; Chou et al., 2013; Liu and Allan, 2013; Fu and Feng, 2014)."


id: d08ae9803b6a007ec358388591a6ba70
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34038
content:
"In summary, a low signal-to-noise ratio, observational uncertainties \r\nand current data assimilation techniques limit the assessment of \r\nrecent global trends in P-E over both land and ocean. It is likely\r\nthat the global land P-E variations observed since the late 1970s \r\nwere dominated by internal variability, mostly linked to ENSO \r\nteleconnections (medium confidence). In contrast, the attribution of \r\nchanges in sea surface salinity (Section 3.5.2.2) suggests that it is \r\nextremely likely that human influence has contributed to the regional \r\nchanges in P-E observed over the global ocean since the mid\u000220th century."


id: 8645837f6cb8634c83c9268ca5097d6a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20778
content:
"The AR5 presented evidence of increases in global near-surface and \r\ntropospheric specific humidity since the 1970s but with medium \r\nconfidence of a  slowing of near-surface moistening trends over \r\nland associated with reduced relative humidity since the late 1990s. \r\nAccording to AR5, radiosonde, Global Positioning System (GPS) and \r\nsatellite observations of tropospheric water vapour indicate very likely\r\nincreases at near global scales since the 1970s occurring at a rate that \r\nis generally consistent with the Clausius-Clapeyron relation (about \r\n7%  degC-1 at low altitudes) and the observed atmospheric warming \r\n(Hartmann et al., 2013). "


id: 3d51cb6795ecc26d57a21d2132cb4830
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7966
content:
"precipitation over wet tropical land areas (Gimeno et al., 2020) and to \r\nmore extreme and persistent wet and dry weather events (Konapala \r\net al., 2020) in many regions worldwide. "


id: 22d49c106683409e4d6acfe90475d0aa
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 3336
content:
"activities, but are consistent with the heating effect of increasing CO2\r\nlevels on the distribution of daily precipitation rates (Section 8.2.3.2) \r\nand with a  distinct overall intensification of heavy precipitation \r\nevents found in both observations and CMIP5 models, though with \r\nan underestimated magnitude (Fischer and Knutti, 2014). Beyond \r\namplified precipitation extremes (Section  11.4.2), CMIP5 models \r\nalso indicate that anthropogenic forcings have increased temporal \r\nvariability of annual precipitation amount over land from 1950 to \r\n2005, which is most pronounced in annual mean daily precipitation \r\nintensity (Konapala et al., 2017). "


id: ddfc990b94111e6788f31e3de527b3dc
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36320
content:
"In summary, there is high confidence that human-caused global \r\nwarming has led to an overall increase in water vapour and moisture \r\ntransport throughout the troposphere, at least since the mid-1990s. \r\nIn particular, there is high confidence that moisture transport into the \r\nArctic has increased but only medium confidence in the attribution \r\nof such a trend to a human influence. There is medium confidence\r\nthat human influence has contributed to a decrease in near-surface \r\nrelative humidity over the Northern Hemisphere mid-latitude \r\ncontinents during summer (see also Sections 2.3.1.3 and 3.3.2.3)."


id: 6347c0dca57ca4a3ecbeeedeeba76353
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14761
content:
"Anthropogenic aerosols can alter precipitation intensities \r\nboth through radiative and microphysical effects (Box  8.1 and \r\nSection  8.5.1.1.2). Precipitation suppression through aerosol \r\nmicrophysical effects has been observed in shallow cloud regimes \r\nover South America and the south-eastern Atlantic, associated \r\nwith local biomass burning (Andreae et al., 2004; Costantino and \r\nBreon, 2010), and in industrial regions in Australia (Rosenfeld, \r\n2000; Hewson et al., 2013; Heinzeller et al., 2016). In contrast, \r\nprecipitation intensification through aerosol microphysical effects \r\nin deep convective clouds is seen in many regions such as the \r\nAmazon, southern USA, India, and Korea. This is associated with \r\nanthropogenic aerosols from cities (Hewson et al., 2013; Fan et al., \r\n2018; S.S. Lee et al., 2018; Sarangi et al., 2018)."


id: fe5e4256c5eb5c0aeff4d6ab10982a76
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 42126
content:
"This section assesses observed changes in precipitation at global \r\nand regional scales. Note that changes in precipitation seasonality \r\nare assessed in Box  8.2 and that changes in regional monsoons \r\nare assessed in section  8.3.2.4 where observed changes in both \r\ncirculation and rainfall are considered. Further assessment of regional \r\nchanges in precipitation is presented in Chapters 10, 12 and Atlas, \r\nwhile extreme precipitation is presented in Chapter 11."


id: b7b6cf5dcc4aa178fd2168b6e9f7ba4e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29539
content:
"Over the African continent, there are distinct precipitation trends \r\nobserved in multiple datasets since the 1980s (Figure 8.7; Maidment \r\net al., 2015; P. Nguyen et al., 2018). Increases in intense convective \r\nstorms affecting the Sahel have been attributed to increased \r\nland-ocean temperature gradients (Taylor et al., 2017), enhanced \r\nby intense heating of the Sahara (Dong and Sutton, 2015) rather \r\nthan thermodynamics (Section  8.2.2). Changes in Sahel rainfall, \r\nwith reduced precipitation amounts from the 1960s to the 1980s \r\nand a  subsequent recovery, are assessed in Sections  8.3.2.4.3 \r\nand 10.4.2.1. In eastern Africa, decreasing precipitation amount \r\n(-2 to -7 % per decade for 1983-2010) was reported for the March \r\nto May 'long rains' season (Lyon and Dewitt, 2012; Viste et al., 2013; \r\nLiebmann et al., 2014; Maidment et al., 2015; Rowell et al., 2015) \r\nand evidence of a  recovery since, with internal variability playing "


id: 54e64408acebe8f8f14ec6e89b15ad30
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12205
content:
"Global and regional changes in precipitation frequency and intensity \r\nhave been observed over recent decades. An analysis of 1875 rain \r\ngauge records worldwide over the period 1961-2018 indicates that \r\nthere has been a general increase in the probability of precipitation \r\nexceeding 50  mm  day-1, mostly due to an overall boost in rain \r\nintensity (Benestad et al., 2019). Such changes in precipitation \r\nintensity and frequency have not been formally attributed to human "


id: a34a49617af7d21449c2f108fb573f64
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 25937
content:
"a large role in these decadal changes (Wainwright et al., 2019). In \r\ncontrast, the second 'short rains' season in eastern Africa (October to \r\nDecember) does not exhibit significant precipitation trends (Rowell \r\net al., 2015). Increases in annual southern African rainfall of 6-7% \r\nper decade during 1983-2010 are linked with the Pacific Decadal \r\nOscillation (PDO; Maidment et al., 2015)."


id: 411f2e848ead36b527b27675ff8a19b1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8638
content:
"Section  8.3.1.6 assesses changes in precipitation over the \r\nMediterranean region and its connection with drought and aridity."


id: 19dda7e5456efb32117895a3ea5bd50
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1749
content:
"Rainfall increases have been observed over northern Australia since \r\nthe 1950s, with most of the increases occurring in the north-west \r\n(Dey et al., 2019a, b; Dai, 2021) and decreases observed in the north\u0002east (J. Li et al., 2012) since the 1970s. In contrast, there has been \r\na  decline in rainfall over southern Australia related to changes in \r\nthe intensification and position of the subtropical ridge (CSIRO and \r\nBoM, 2015) and anthropogenic effects (Knutson and Zeng, 2018). \r\nThe drying trend over south-west Australia is most pronounced \r\nduring May to July, where rainfall has declined by 20% below the \r\n1900-1969 average since 1970 and by about 28% since 2000 (BoM \r\nand CSIRO, 2020). "


id: e7cdd203417c05e4144571697cac8fac
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38089
content:
"Snowfall is an important component of precipitation in high-latitude \r\nand mountain watersheds. Reanalysis data indicate significant \r\nreductions in annual mean potential snowfall areas over NH land by \r\n0.52 million km2 per decade, with the largest decline over the Alps, \r\nwith snow water equivalent reductions of about 20 mm per decade \r\n(Tamang et al., 2020). In the Tibetan Plateau, region-wide winter \r\nsnowfall has increased but summer snowfall has decreased during \r\nthe 1960-2014 period (Deng et al., 2017). State-of-the-art model \r\nsimulations indicate reduced mean annual snowfall in the Arctic, \r\ndespite the strong precipitation increase, mainly in summer and \r\nautum, when temperatures are close to the melting point (Bintanja \r\nand Andry, 2017). "


id: dea1d5cc1ee39c49b3bb18ec6d6ac6ed
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36431
content:
"line with similar studies that focused on the 1981-2012 (Y. Zhang \r\net al., 2016) and 1982-2013 (K. Zhang et al., 2015) periods. Zeng \r\net al. (2018) determined that the 8% global increase in satellite\u0002observed leaf area index between the 1980s and the 2010s may \r\nexplain an increase in evapotranspiration of 12.0 +-  2.4  mm yr-1\r\n(about 55 +-  25% of the total observed increase). Forzieri et al. \r\n(2020) estimated that the recent increase in leaf area index led to \r\n3.66+-0.45 W m-2 in latent heat flux (about 51 +- 6 mm yr-1) and \r\nthat the sensitivity of energy fluxes to leaf area index increased by \r\nabout 20% over the 1982-2016 period. Overall, there is medium \r\nconfidence that greening has contributed to the global increase in \r\nevapotranspiration since the 1980s."


id: 537204f95a19e46466b4fc765a01e786
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11960
content:
"An increasing number of studies have identified signals of attribution \r\nin the recent observed trends in evapotranspiration. Douville \r\net al. (2013) found that the post-1960 rise in evapotranspiration in \r\nboth the mid-latitudes and northern high latitudes was related to \r\nanthropogenic radiative forcing. An analysis of CMIP5 simulations \r\nsuggests that anthropogenic forcing accounts for a  large fraction \r\nof the global mean evapotranspiration trend from 1982 to 2010 \r\n(Dong and Dai, 2017). Padron et al. (2020) determined that \r\nincreases in evapotranspiration were responsible for the majority \r\nof the anthropogenic pattern in dry-season water availability that \r\ndominates global trends since 1984. These findings are further \r\nsupported by CMIP6 model results (Figure  8.8) that show that \r\nthe recent summer increase in evapotranspiration in the northern \r\nmid- and high latitudes is due to GHG forcing and decreasing \r\nanthropogenic aerosol emissions over Europe. "


id: 90e5aad13ec0b09138e2f44eae67a488
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22702
content:
"In summary, there is high confidence that terrestrial evapotranspiration \r\nhas increased since the 1980s. There is medium confidence that \r\nthis trend is driven by both increasing atmospheric water demand \r\nand vegetation greening, and high confidence that it can be partly \r\nattributed to anthropogenic forcing. There is low confidence about \r\nthe extent to which increases in plant water use efficiency have \r\ninfluenced observed changes in evapotranspiration. "


id: d732627fda3233aaa3fcba35784a645d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35168
content:
"Since AR5, the predominant contribution of transpiration to the \r\nobserved trends in terrestrial evapotranspiration has been revisited \r\nand confirmed (Good et al., 2015; Wei et al., 2017). Using satellite \r\nand ecosystem models, Zhu et al. (2016) found a positive trend in \r\nleaf area index during 1982-2009, indicating that greening could \r\ncontribute to the observed positive trend of evapotranspiration, in "


id: 2e3d4bd047888fb945feb6d2df06b010
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5407
content:
"studies of changes in the timing of streamflow in snow-influenced \r\nbasins continue to support a  prominent influence from warming \r\n(Kang et al., 2016; Dudley et al., 2017; Kam et al., 2018). Global \r\nland runoff variations correlate significantly with ENSO variability \r\n(Miralles et al., 2014b; Schubert et al., 2016)."


id: 72ffead5395418438306ecb6a1658a8a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17482
content:
"Observed changes in flooding are assessed in Section  11.5.2 and \r\nare summarized as follows. For changes in the magnitude of peak \r\nflow, recent studies show strong spatial heterogeneity in the sign, \r\nsize and significance of trends. For changes in timing of peak flows, \r\nrecent studies further support observed changes in snowmelt-driven \r\nrivers. Observed changes in runoff and flood magnitude cannot be \r\nexplained by precipitation changes alone given the possible season\u0002and region-dependent decreases in antecedent soil moisture and \r\nsnowmelt, which can partly offset the increase in precipitation \r\nintensity (Sharma et al., 2018), or the expected effect of urbanization \r\nand deforestation which can, on the contrary, amplify the runoff \r\nresponse (Chen et al., 2017; Abbott et al., 2019; Cavalcante et al., \r\n2019). Simulations of mean and extreme river flows are consistent \r\nwith the observations only when anthropogenic radiative forcing is \r\nconsidered (Gudmundsson et al., 2021). "


id: 3842dc708905bf55411de85958151a5
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7104
content:
"In summary, the assessment of observed trends in the magnitude \r\nof runoff, streamflow, and flooding remains challenging, due to the \r\nspatial heterogeneity of the signal and to multiple drivers. There is, \r\nhowever, high confidence that the amount and seasonality of peak \r\nflows have changed in snowmelt-driven rivers due to warming. There \r\nis also high confidence that land-use change, water management \r\nand water withdrawals have altered the amount, seasonality, \r\nand variability of river discharge, especially in small and human\u0002dominated catchments. "


id: 29aa195706e9604d7818f7f0d44c4449
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4557
content:
"The AR5 reported low confidence that changes in drought since the \r\nmid-20th century could be attributed to human influence, owing to \r\nobservational uncertainties and difficulties in distinguishing decadal\u0002scale variability from long-term trends. Changes in soil moisture, \r\na metric of aridity, were not assessed thoroughly in AR5. Since AR5, \r\nnew satellite products, land surface reanalyses, and land surface \r\nmodels have been used to document recent changes in soil moisture \r\nat the global scale. The science of detection and attribution has also \r\nprogressed considerably (Trenberth et al., 2015; Easterling et al., \r\n2016; Stott et al., 2016). Attribution efforts have further benefited \r\nfrom the increased use of paleoclimate information, which provides \r\nan important constraint on natural variability that is insufficiently \r\nsampled by short observational record (Cook et al., 2018; Kageyama \r\net al., 2018)."


id: f88c21485cda8b1b48ec31447062a29f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41088
content:
"Several studies have identified a  persistent 'fingerprint' of \r\nanthropogenic forcing in global trends in aridity spanning the last \r\n120 years. Using a  combination of tree ring data, CMIP5 model \r\nsimulations, and reanalysis products, Marvel et al. (2019) determined \r\nthat the dominant trend in aridity since 1900, characterized by \r\ndrying in North and Central America and the Mediterranean, is \r\ndetectable and attributable to external forcing from 1900 to 1949. \r\nThis trend weakens from 1950 to 1975, possibly due to aerosol "


id: bbcc70e6b79c4a3f5231be87896f688
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30268
content:
"Some studies have suggested that dam construction and water \r\nwithdrawals can be the dominant drivers in observed trends in \r\nstreamflow amount (Wada et al., 2013). Regionally, land-use and \r\nland cover changes have been identified as important factors for \r\nstreamflow (H.  Chen et al., 2020). The impact of surface dimming \r\nfrom aerosol emissions on evaporation was identified as a discernible \r\ninfluence in NH streamflows (Gedney et al., 2014). While changes \r\nin annual mean streamflow present a  complicated picture, recent "


id: ef5ed7b16d2796888437032e1cadaad8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39483
content:
"accounted for 8-27% of these soil moisture deficits. Robeson (2015) \r\nestimated that the California drought was a 1-in-10,000 year event. \r\nTree ring reconstructions indicate that prolonged megadroughts \r\nhave occurred in the western USA throughout the last 1200 years \r\n(Cook et al., 2004, 2010; B.I. Cook et al., 2015), forced by internal \r\nvariability (Coats et al., 2016; Cook et al., 2016b). However, Williams \r\net al. (2020) determined that 2000-2018 drought across the south\u0002western USA was the second driest 19-year period since 800 CE, and \r\nattributed nearly half the magnitude of this event to anthropogenic \r\nforcing (see also Section  10.4.2.3). Evidence for human signals in \r\ndrought can also be found in western North American streamflow \r\nrecords, as noted above in Section 8.3.1.5. There is high confidence\r\nthat anthropogenic forcing has contributed to recent droughts and \r\ndrying trends in western North America."


id: 1332f957af45cda437eff3bf19f818c7
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 588
content:
"Large areas of east-central Asia experienced drying in the early 2000s \r\nas a result of warmer temperatures, lower humidity, and declining \r\nsoil moisture (Wei and Wang, 2013; Z. Li et al., 2017; Hessl et al., \r\n2018). Paleoclimate data from the Mongolian plateau suggest that \r\nthis recent central Asian drought exceeds the 900-year return interval, \r\nbut is not unprecedented in the last 2060 years (Hessl et al., 2018). \r\nThere is low confidence due to limited evidence that recent droughts \r\nin central Asia can be attributed to anthropogenic forcing."


id: f9ed3b7e064d001995062d72b21923f6
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41337
content:
"On a regional scale, the robustness of trend attribution for drought \r\nand aridity varies widely. Key trends and their attributions are \r\nsummarized here, while a complete regional assessment of observed \r\ntrends in drought and aridity is in Chapter 11 (Sections 11.6.2, 12.3.2 \r\nand 12.4)."


id: 458d7d7aa32a07183d515a00f6a08b1c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9460
content:
"In the western USA, anthropogenic warming is amplifying drought \r\nand aridity by increasing evaporative demand and water loss to the \r\natmosphere (Weiss et al., 2009; Overpeck, 2013; Cook et al., 2014; \r\nGriffin and Anchukaitis, 2014; Williams et al., 2020). For the California \r\ndrought between 2012-2014, Griffin and Anchukaitis (2014) \r\nused paleoclimate reconstructions to determine that while rainfall \r\ndeficits were not unprecedented, record-high temperatures drove an \r\nexceptional decline in soil moisture relative to the last millennium. \r\nWilliams et al. (2015) concluded that anthropogenic warming "


id: 84ea8ded67916ef17c493290763e727
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20522
content:
"Both central and north-eastern Africa have experienced a  decline \r\nin rainfall since about 1980 (high confidence) (Lyon and Dewitt, \r\n2012; Lyon, 2014; Hua et al., 2016; Nicholson, 2017). In Central \r\nAfrica, the decline has been attributed to atmospheric responses to \r\nIndo-Pacific sea surface temperature variability (Hua et al., 2018). \r\nIn north-eastern Africa, droughts have become longer and more "


id: c8a3e26eff26bf97251d9c838451b084
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32616
content:
"In summary, it is very likely that anthropogenic factors have \r\ninfluenced global trends in aridity, mainly through competing \r\nchanges in evapotranspiration and/or atmospheric evaporative \r\ndemand due to anthropogenic emissions of GHG and aerosols. There \r\nis high confidence that the frequency and the severity of droughts has \r\nincreased over the last decades in the Mediterranean, western North \r\nAmerica, and south-western Australia and that this can be attributed \r\nto anthropogenic warming. There is medium confidence that recent \r\ndrying and severe droughts in southern Africa and south-western \r\nSouth America can be attributed to human influence. In some regions \r\nof western North America and the Mediterranean, paleoclimate \r\nevidence suggests that recent warming has resulted in droughts that \r\nare of similar or greater intensity than those reconstructed over the \r\nlast millennium (medium confidence)."


id: f4748569547ee26df4f959ca92e7f8f4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40381
content:
"Several subtropical, semi-arid regions in the Southern Hemisphere \r\nhave experienced long-term drying trends in the late 20th century. \r\nSouth-western South America (central Chile) experienced a  multi\u0002decadal decline in precipitation and streamflow culminating in \r\na  post-2010 megadrought that has been partly attributed to \r\nanthropogenic GHG emissions and ozone depletion (Boisier et al., \r\n2016, 2018; Saurral et al., 2017; Knutson and Zeng, 2018; Seager \r\net al., 2019b; Garreaud et al., 2020). There is medium confidence that \r\ndrying in central Chile can be attributed to human influence. The tree\u0002ring paleoclimate record demonstrates that the mid-century increase \r\nin exteme drought events in southern South America is unusual in \r\nthe context of the last 600 years, suggesting an emerging influence \r\nof anthropogenic forcing (Morales et al., 2020). "


id: c092d577fc7b59f51a9eedcf11fe9dca
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31179
content:
"There has been a 20% decrease in winter (May to July) rainfall in \r\nsouth-western Australia since 1970, with the decline increasing to \r\naround 28% since 2000 (Delworth and Zeng, 2014; BoM and CSIRO, \r\n2020). There has also been a  significant increase in the average \r\nintensity of seasonal droughts in the region since 1911in response \r\nto both lower precipitation and increased atmospheric evaporative \r\ndemand (Gallant et al., 2013). Several studies attribute the \r\nprecipitation declines in south-western Australia to anthropogenic \r\nchanges in GHG and ozone (Delworth and Zeng, 2014; Knutson \r\nand Zeng, 2018; Seager et al., 2019b). There is high confidence that \r\nthe observed drying in south-western Australia can be attributed to \r\nanthropogenic forcing. "


id: 220a0c26083dedb5b33621c199fc7faa
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 3213
content:
"In south-eastern Australia, the average length of droughts have \r\nincreased significantly, lasting between 10 and 69% longer than \r\ndroughts during the first half of the 20th century (Gallant et al., \r\n2013). Paleoclimate reconstructions indicate a  97.1% probability \r\nthat the decadal rainfall anomaly recorded during the 1997-2009 "


id: 97e557f5035f3f633f312c9b54544940
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 23938
content:
"2000 and 2018 are -19.0 +- 2.5 Gt yr-1 (Shean et al., 2020). The most \r\nnegative changes were found in Nyainqentanglha with -4.0 +- 1.5 \r\nGt yr-1, while glaciers in Kunlun, northern Tibetan Plateau, slightly \r\ngained mass at 1.4 +- 0.8 Gt yr-1."


id: 37278edcaa3eec0b5f7cdc3d39073ab0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 6920
content:
"There is some evidence that an increase of precipitation over high \r\nmountains can offset glacier ablation (melt; Farinotti et al., 2020). \r\nHowever, this process has only been described from the Karakoram \r\nregion in the north-western Himalaya, where it is thought to be \r\npartly responsible to the advances of glacier changes in the last two \r\ndecades, referred to as the 'Karakoram Anomaly' (Farinotti et al., \r\n2020). In the Himalaya, Maurer et al. (2019) observed faster ice \r\nloss during 2000-2016 (7.5 +- 2.3 Gt yr-1) compared to 1975-2000 \r\n(-3.9  +-  2.2 Gt yr-1). In the Southern Hemisphere, the rate of \r\nglacier mass lost in South America is estimated at 19.4 +- 0.6 Gt \r\nyr-1 based on surface elevation changes over 2000-2011, which \r\ninclude the North and South Patagonian Icefields of South America \r\n(Braun et al., 2019), and at -22.9 +- 5.9 Gt yr-1 over 2000-2018 \r\n(Dussaillant et al., 2019)."


id: e8bed05e1e1549489ceb1043e8f40b9e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38294
content:
"In summary, human-induced global warming has been the primary \r\ndriver of a  global glacier recession since the early 20th century \r\n(high confidence). Most glaciers have lost mass more rapidly since \r\nthe 1960s and in an unprecedented way over the last decade, \r\nthereby contributing to increased glacier runoff, especially from \r\nlarger glaciers until a maximum is reached, which tends to occur \r\nlater in basins with larger glaciers and higher ice-cover fractions \r\n(high confidence)."


id: 2a43b799a78ad290cfc0b1d5df1a2ca9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4654
content:
"In summary, a  decline in the spring NH snow cover extent, snow \r\ndepth and duration has been observed since the late 1960s and has \r\nbeen attributed to human influence (high confidence). Depending \r\non the region and season, there is low-to-medium confidence in the \r\nmain drivers of snow cover changes, although various regions exhibit \r\na  shortening of the snow cover season which is consistent with \r\nglobal warming. A more detailed assessment of observed changes in \r\nseasonal snow cover is provided in Section 9.5.3."


id: 6711ca5b6cf3ba2bc2ec799dda4e3b0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15400
content:
"Wetlands and lakes affect the climate through their impact on carbon \r\nand methane budgets (Section 5.2.2; e.g., Saunois et al., 2016; Zhan \r\net al., 2019) and on surface heat fluxes, with coupled weather and \r\nclimate effects (e.g., Zhan et al., 2019). Although these features are \r\nalso affected by human activities and by climate change, AR5 did not \r\nspecifically report on wetlands and lakes."


id: a91dfca1e674cc207bd461bfbef1a0e3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26973
content:
"Inventories of surface water bodies are not systematically produced \r\nat national or regional levels. However, assessments are undertaken \r\nat the global scale (Ramsar Convention on Wetlands, 2018). Merging \r\nobservations from multiple satellite sensors makes it possible to \r\ndetect surface water even under vegetation and clouds over about \r\n25 years, but with low spatial resolution (Prigent et al., 2016). \r\nMost recent multi-satellite products from visible, infrared, and \r\nmicrowave measurements, estimate a surface water area of about \r\n12 to 14 million km2 (including permanent and transitory surfaces, \r\ne.g., Aires et al., 2018; Davidson et al., 2018), which is much higher \r\nthan those provided by optical imagery (about 3  million km2). \r\nInventories show a strong decrease in natural surface water of about \r\n0.8% yr-1 in total from 1970 to the present (Ramsar Convention \r\non Wetlands, 2018) but the sites are not evenly distributed. Multi-"


id: f185e25241220a077f6f8dada22e5f94
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39877
content:
"Observations show a  rapid recent decrease of spring SCE in NH, \r\nmostly in Eurasia and North America, closely linked to temperature \r\nchange, for example, March to April SCE is decreasing at 3.4% +- 1.1 \r\n% per decade (1979-2005; Brown and Robinson, 2011; Hernandez\u0002Henriquez et al., 2015). An overall increasing annual trend of the \r\nNH SCE since the late 1980s has been observed, in contrast to \r\ndecreasing trends over 1960s to 1980s that are dominated by the "


id: ef4af7cc3f2bdfc7e1a59e54767e529a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39469
content:
"satellite estimates show a  strong interannual variability in surface \r\nwater extent over the period 1992-2015 with no clear long-term \r\ntrend (Prigent et al., 2020). "


id: f33b7836272dddaa3d2310900aeea626
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40169
content:
"limited ability of global climate models to represent key controls \r\non regional rainfall variability like ENSO (Technical Annex VI and \r\nSection 3.7.3; R. Chen et al., 2020) may also underestimate observed \r\nrecharge from such events that are of particular importance in \r\ndrylands (R.G. Taylor et al., 2013b; Cuthbert et al., 2019b). Numerical \r\nrepresentations of the impact of precipitation intensification on \r\ngroundwater recharge in large-scale models remain constrained by \r\nthe challenges of including key recharge pathways that consider \r\npreferential flowpaths in soils (Beven, 2018) and focused recharge \r\nthrough leakage from surface waters (Doll et al., 2014)."


id: 13035da18a627c02a516d495775d3955
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 553
content:
"Human-made water bodies represent approximately 10% of the \r\ntotal continental water surfaces (Figure 8.1; Ramsar Convention on \r\nWetlands, 2018) and consist mainly of reservoirs and rice paddies. \r\nHigh resolution optical imagery over the period 1984-2015 \r\n(Donchyts et al., 2016; Pekel et al., 2016) shows a net increase of \r\nabout 0.1 million km2 in artifical water surfaces, mainly due to the \r\nconstruction of reservoirs. Surfaces of rice paddies are also increasing, \r\nespecially in South East Asia (Davidson et al., 2018). "


id: 1a74a9d06351c3eaacabf5fd58a4372d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1856
content:
"In summary, there is high confidence that the extent of human-made \r\nsurface water has increased over the 20th and early 21st centuries. \r\nIn contrast, due to low agreement in the observational records at the \r\nglobal scale, there is only low confidence in the observed decline of \r\nthe natural surface water extent in recent years (see also SRCCL)."


id: 4961f1295cf1c379d9790e2ada208179
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10130
content:
"As the world's most widespread store of freshwater (R.G.  Taylor \r\net al., 2013a), groundwater is estimated to supply between a quarter \r\nand a third of the world's annual freshwater withdrawals to meet \r\nagricultural, industrial and domestic demands (Doll et al., 2012; Wada \r\net al., 2014; Hanasaki et al., 2018)."


id: 9f2b2dbeb7f87afbd5d4f8e5bc98069c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 25225
content:
"Attribution of changes in groundwater storage, observed locally \r\nthrough piezometry (Figure  8.10; R.G.  Taylor et al., 2013a) or \r\nestimated from GRACE satellite measurements (Rodell et al., 2018) at \r\nregional scales (>100,000 km2), is often complicated by non-climate \r\ninfluences that include land-use change (Favreau et al., 2009) and \r\nhuman withdrawals (Bierkens and Wada, 2019). "


id: 180aa46aca8e81bac637bd5367806ffa
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1438
content:
"Quantification of changes in groundwater storage from GRACE is \r\ncurrently constrained by uncertainty in the estimation of changes \r\nin other terrestrial water stores using uncalibrated, global-scale \r\nLand Surface Models (Doll et al., 2014; Scanlon et al., 2018) and \r\nthe limited duration of the period of GRACE observations (2002 to \r\n2016). Centennial-scale piezometry in north-west India reveals that \r\nrecent groundwater depletion traced by GRACE (Rodell et al., 2009; \r\nChen et al., 2014), follows more than a  century of groundwater \r\naccumulation through canal leakage (MacDonald et al., 2016). \r\nFurther, groundwater depletion is often localized occurring below the \r\nfootprint (200,000 km2) of GRACE, as has been well demonstrated by \r\ndetailed modelling studies in the California Central Valley (Scanlon \r\net al., 2012) and North China Plain (Cao et al., 2016)."


id: d461e67cd5c5d46da10512eb85d6020
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34687
content:
"Climate variability and drought affect groundwater depletion \r\nmainly due to amplified groundwater withdrawals. For instance, the \r\ndepletion rate in Central Valley aquifer in the USA from 2006 to 2010 \r\nis estimated to range from 6 to 8 km3 yr-1 using GRACE data (Scanlon \r\net al., 2012). In India, Asoka et al. (2017) show contrasting trends in \r\ngroundwater storage in the north (declining at 2 cm yr-1) and south \r\n(increasing at 1-2 cm yr-1) that is explained by variations in human \r\nwithdrawals and precipitation linked to Indian Ocean sea surface \r\ntemperature variability."


id: db17b2699c19531e8b88c04aac6ddaf2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35821
content:
"The overall underestimation of precipitation intensities in global \r\nclimate models (Wehner et al., 2010, 2020; Goswami and Goswami, \r\n2017) and of their sensitivity to warming temperatures (Borodina \r\net al., 2017) may lead to underestimates of their recharging effect \r\non groundwater (Mileham et al., 2009; Cuthbert et al., 2019b). The "


id: b3b216095ea6885582b633fece7fdaf1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28858
content:
"et al. (2019) in the Ganges-Brahmaputra-Megna basin, may be more \r\nseverely and widely affected by changes in upstream river discharge. \r\nThey argue further that saltwater inundation from storm surges will \r\nhave the greatest localized effects."


id: efbcdc18017f514ff72509f9364e0fce
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39558
content:
"recharge (Tague and Grant, 2009). Aquifers in mountain valleys \r\nshow shifts in the timing and magnitude of: (i) peak groundwater \r\nlevels due to an earlier spring melt; and (ii) low groundwater levels \r\nassociated with lower baseflow periods (Allen et al., 2010; Dierauer \r\net al., 2018; Hayashi, 2020). The effects of receding alpine glaciers on \r\ngroundwater systems are not well understood but long-term loss of \r\nglacier storage is estimated to reduce summer baseflow (Gremaud \r\net al., 2009). In permafrost regions, coupling between surface water \r\nand groundwater systems may be particularly enhanced by warming \r\n(Lamontagne-Halle et al., 2018; Lemieux et al., 2020). In areas of \r\nseasonal or perennial ground frost, increased recharge is expected \r\ndespite a  decrease in absolute snow volume (Okkonen and Klove, \r\n2011; Walvoord and Kurylyk, 2016)."


id: ac89e855ee1df37f8e7f079ed6b02f05
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27594
content:
"In summary, there is medium confidence that increased precipitation \r\nintensities, partly due to human influence, have enhanced groundwater \r\nrecharge, most notably in the tropics. There is high confidence that \r\ngroundwater depletion has occurred since at least the start of the \r\n21st century as a  consequence of groundwater withdrawals for \r\nirrigation in some of the world's most productive agricultural areas \r\nin drylands (e.g., southern High Plains and California Central Valley in \r\nthe USA, the North China Plain, north-west India)."


id: da7900c5dde9036491bb1220db29c7ad
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35739
content:
"Coastal aquifers are the interface between the oceanic and terrestrial \r\nhydrological systems. Global sea level rise (SLR) causes interfaces \r\nbetween freshwater and saline-water to move inland. The extent \r\nof seawater intrusion into coastal aquifers depends on a variety of \r\nfactors including coastal topography, recharge, and groundwater \r\nabstraction from coastal aquifers (Comte et al., 2016). Modelling \r\nresults suggest that the impact of SLR on seawater intrusion is \r\nnegligible compared to that of groundwater abstraction (Ferguson \r\nand Gleeson, 2012; Yu and Michael, 2019). Coastal aquifers under \r\nvery low hydraulic gradients, such as the Asian mega-deltas, are \r\ntheoretically sensitive to SLR but, according to evidence from Akter "


id: ec7bd344dc30eb5eced9b55f4a8f76c8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38968
content:
"Observed changes in large-scale circulation indicators (Cross-Chapter \r\nBox 2.2) are assessed in Chapters 2 and 3 (Sections 2.3.1.4 and 3.3.3). \r\nIn this chaper we focus on the influence of regional scale teleconnection \r\nvariabililty on the water cycle and the attribution of these circulation \r\nchanges. While observed changes in modes of variability are assessed \r\nin Chapters 2 and 4 (Sections 2.4 and 4.3.3), here focus on hydrological \r\nteleconnections of relevance to the water cycle."


id: 693802339abaaefeef51ff4ad6902815
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15774
content:
"2014; Bronnimann et al., 2015). However, CMIP5 and CMIP6 models still \r\nexhibit strong biases in representing the ITCZ, such as the simulation \r\nof a double ITCZ (Oueslati and Bellon, 2015; Adam et al., 2018; Tian \r\nand Dong, 2020). The impacts of aerosols and volcanic activity on the \r\nposition of the ITCZ have been investigated but changes are difficult to \r\ncharacterize from observations (Section 6.3.3.2; Friedman et al., 2013; \r\nJ.M. Haywood et al., 2013; Iles and Hegerl, 2014; Colose et al., 2016; \r\nChung and Soden, 2017). Such systematic shifts of the ITCZ can have \r\nimportant regional impacts like changes in precipitation (Figure 8.9)."


id: ae1a3aef833f9df43038dc6dd20752b1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27873
content:
"In summary, there is medium confidence that the tropical rain belts \r\nover the oceans have been narrowing and strengthening in recent \r\ndecades, leading to increased precipitation in the ITCZ core region \r\n(Section 8.2.2.2). Decreasing precipitation trends in the NH during \r\nthe 1950s-1980s have been attributed to anthropogenic aerosol \r\nemissions from North America and Europe (high confidence)."


id: 4d41e55c1468fa6b264f280101fbf5ae
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 10874
content:
"The AR5 reported low confidence in trends in the strength of the \r\nHadley circulation (HC) due to uncertainties in reanalyses but high \r\nconfidence on the widening of the tropical belt since 1979. In AR6, \r\nChapter  2  (Section  2.3.1.4.1) states that the HC has very likely\r\nwidened and strengthened since at least the 1980s, mostly in the NH \r\n(medium confidence). "


id: 58c59deaed0dfd504435bf99e06086f2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12859
content:
"ITCZ trends seen in satellites, precipitation measurements and \r\nreanalysis data are further supported by ocean surface-salinity \r\nobservations. Long-term salinity observations show a  freshening in \r\nthe cores of the Atlantic and Pacific ITCZs and increased salinity on \r\nthe ITCZ margins (Durack and Wijffels, 2010; Durack et al., 2012; \r\nTerray et al., 2012; Skliris et al., 2014). By investigating simultaneous \r\nchanges in precipitation, temperature and continental aridity in CMIP5 \r\nhistorical simulations, Bonfils et al. (2020) found a secondary signal \r\n(Figure 8.9, right column) characterized by a robust inter-hemispheric \r\ntemperature contrast (Section 3.3.1.1), a latitudinal shift in the ITCZ \r\n(in accordance with the theory of cross-equatorial energy transport; \r\nSection 8.2.2.2), and changes in aridity in the Sahel (Section 8.3.1.6). \r\nThese forced changes are statistically detectable in reanalyses datasets \r\nover the 1950-2014 period at the 95% confidence level."


id: a983dcf325b430068f0ba719e4dd54ca
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27045
content:
"In the Southern Hemisphere (SH), the HC expansion has \r\nbeen  associated with both the intensification and poleward shift \r\nof the subtropical high pressure belt (Nguyen et al., 2015), with \r\nconsequences for precipitation amount over Africa, Australia, \r\nSouth  America, and subtropical Pacific islands (Cai et al., 2012; \r\nGrose et al., 2015; Nguyen et al., 2015; Sharmila and Walsh, 2018; \r\nMcGree et al., 2019). The subtropical ridge in Australia has intensified \r\nsignificantly since 1970, with marked declines observed in April to \r\nOctober rainfall across south-eastern and south-western Australia \r\n(Timbal and Drosdowsky, 2013). "


id: 6442bea67320ee010f61bd39af969c89
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14924
content:
"The causes of the observed strengthening of the WC during 1980-2014 \r\nare not well understood due to competing influences from individual \r\nexternal forcings and since this strengthening is outside the range \r\nof variability simulated in coupled models (medium confidence), as \r\nassessed in Chapter 3 (Section 3.3.3.1). Recent strengthening in the WC \r\nhas been linked with internal variability (Chung et al., 2019), although \r\none study argues that it could be a  response forced by GHG that \r\nmodels do not capture because of common sea surface temperature \r\n(SST) biases in the equatorial Pacific (Seager et al., 2019a). It could \r\nbe also related to an interbasin thermostat mechanism whereby \r\nthe human-induced Indian Ocean warming emerged earlier than in \r\nthe tropical Pacific (L.  Zhang et al., 2018) and induced a  transient \r\nstrengthening of the zonal sea level pressure gradient and easterly \r\ntrades in the tropical Pacific (L. Zhang et al., 2019)."


id: 7e6e0f7d69e090a2c09e34b5dcb8294d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19403
content:
"associated with hydroclimate variations than the subtropical ridge \r\n(Staten et al., 2019). Poleward expansion of the tropical belt strongly \r\ncontributes to precipitation decline in the poleward edge of the \r\nsubtropics (Cai et al., 2012; Scheff and Frierson, 2012; Timbal and \r\nDrosdowsky, 2013; He and Soden, 2017; H.  Nguyen et al., 2018; \r\nTang et al., 2018), although recent modelling evidence suggests \r\nthat subtropical precipitation declines are a response to direct CO2\r\nradiative forcing mainly over ocean, irrespective of the HC expansion \r\n(He and Soden, 2017). Both reanalyses datasets and climate model \r\nsimulations suggest that the HC expansion is not associated with \r\nwidespread, zonally symmetric subtropical drying over land (Schmidt \r\nand Grise, 2017). "


id: 984add541ea82cf55b8f0dc30a7ac6ae
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 24003
content:
"The weakening of the PWC observed during most of the 20th \r\ncentury is associated with reductions in land rainfall over the \r\nMaritime Continent during 1950-1999 (Tokinaga et al., 2012; \r\nYoden et al., 2017). In contrast, the recent strengthening of the WC \r\nhas been associated with an intensification of extreme flooding \r\n(Barichivich et al., 2018) and an increased frequency of wet days \r\n(J.C.  Espinoza et al., 2016, 2018) over the north-western Amazon, \r\nincreased precipitation in South America (Yim et al., 2017), reduced \r\nprecipitation over eastern Africa (Williams and Funk, 2011; Lyon and \r\nDewitt, 2012), and increased rainfall in southern Africa (Maidment \r\net al., 2015). Internal variability has been shown to have a dominant \r\nrole in the recent strengthening of the WC (Chung et al., 2019)."


id: 5e7acee97325ea9202feb9cffeffe1a1
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 13913
content:
"In summary, there is high confidence that changes in the WC are \r\nassociated with changes in the water cycle over regions like the \r\nMaritime Continent, South America and Africa. It is very likely\r\nthat the WC has strengthened in the Pacific since the 1980s, with \r\nmedium confidence that this strengthening is within the range of \r\ninternal variability. "


id: 7f1dfce29396224f2820059e5e11eb31
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 19514
content:
"In summary, it is very likely that the recent HC expansion was \r\nassociated with poleward shifts of tropical cyclone tracks over the \r\nwestern North Pacific Ocean since the 1940s, and of extratropical \r\nstorm tracks in the SH since the 1970s. Changes to the HC in the \r\nNH may have contributed to subtropical drying and a  poleward \r\nexpansion of aridity during the boreal summer, but there is \r\nlow confidence due to limited evidence. GHG increases and \r\nstratospheric ozone depletion have contributed to expansion of the \r\nzonal mean HC in the SH since around 1970, while the expansion \r\nof the NH  HC has not exceeded the range of internal variability \r\n(medium confidence)."


id: 162dc39f67eade7f8e84066a057ff1ec
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 1111
content:
"The AR5 reported low confidence in the attribution of changes in \r\nmonsoons to human influence, although a  detailed attribution \r\nassessment of the observed changes in the regional monsoons was \r\nnot presented. "


id: 28ad0504b3937b1bd0884f2ca61c5111
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4369
content:
"The AR5 concluded that the long-term weakening of the Pacific Walker \r\ncirculation (WC) from the late 19th century to the 1990s has been \r\nlargely offset by a  recent strengthening (high confidence), though \r\nwith low confidence in trends of the WC strength due to reanalysis \r\nuncertainties and large natural variability. The observed trends in the \r\nWC since 1980 are consistent with a very likely WC strengthening in \r\nthe Pacific, similar to a  La Nina pattern, with medium confidence\r\nin  the magnitude of these changes due to differences between \r\nsatellite observations and reanalyses. "


id: 1558f7fb5630099013c1f21f66039cdf
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 970
content:
"are discussed further in Section  10.4.2, from the perspective of \r\nclimate change attribution and in Section 10.6.3, from the viewpoint \r\nof constructing regional climate messages."


id: 635d94ada99253480bf03406cdc68e08
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14779
content:
"In summary, there is high confidence in observational evidence for \r\na weakening of the SAsiaM in the second half of the 20th century. \r\nResults from climate models indicate that anthropogenic aerosol \r\nforcing has dominated the recent decrease in summer monsoon \r\nprecipitation, as opposed to the expected intensification due to GHG \r\nforcing (high confidence). On paleoclimate time scales, the SAsiaM \r\nstrengthened in response to enhanced summer warming in the NH \r\nduring the early-to-mid Holocene, while it weakened during cold \r\nintervals (high confidence). These changes are tightly linked to orbital \r\nforcing and changes in high-latitude climate (medium confidence)."


id: 2778249abff975c3c844baae6217e11e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4123
content:
"The AR5 reported low confidence in the observed weakening of the \r\nEast Asian monsoon (EAsiaM) since the mid-20th century. Since \r\nAR5, there has been improved understanding of changes in the \r\nEAsiaM, based on paleoclimatic evidence, instrumental observations \r\nand climate modeling simulations. Rainfall reconstructions from \r\nthe Loess Plateau in China indicate that the northern extent of the \r\nmonsoon rain belts migrated at least 300 km to the north-west from \r\nthe LGM to the mid-Holocene (Yang et al., 2015). Similarly, Pliocene "


id: 22a38b4237d4a20f6b89915e50cd6762
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 3312
content:
"reconstructions indicate stronger intensity of the EAsiaM with a more \r\nnorthward penetration of the monsoon rain belt (S.  Yang et al., \r\n2018a). EAsiaM variability has been related to Atlantic Meridional \r\nOverturning Circulation (AMOC) dynamics, especially during the last \r\nglacial period, but whether the relationship is negative or positive \r\nremains uncertain (Sun et al., 2012; Cheung et al., 2018; Kang \r\net al., 2018)."


id: 8e51cd3031de330a84a25f1268d658d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22229
content:
"since the 1950s, but there is low confidence in the magnitude of the \r\nanthropogenic influence. The transition towards a positive PDV phase \r\nhas been one of the main drivers of the EAsiaM weakening since the \r\n1970s (high confidence)."


id: 2430ca58f261a4c208e71e651a1f4fc0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 3552
content:
"Since AR5, there has been improved understanding of the West \r\nAfrican monsoon (WAfriM) response to natural and anthropogenic \r\nforcing. On paleoclimate time scales, enhanced summer insolation in \r\nthe Northern Hemisphere (NH) intensified the WAfriM precipitation \r\nduring the early-to-mid Holocene (high confidence), as seen in rainfall \r\nproxy records and climate model simulations (Masson-Delmotte \r\net al., 2013; Mohtadi et al., 2016; Braconnot et al., 2019). Despite \r\nimprovements in model simulations of the present-day monsoons, \r\nCMIP5 and CMIP6 models underestimate mid-Holocene changes \r\nin the amount and spatial extent of the WAfriM precipitation \r\n(Section 3.3.3.2; Brierley et al., 2020). "


id: 8c2e7ff4f4b21a3c823267ec85fbadcc
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 21837
content:
"Long-term precipitation observations from China indicate a trend of \r\ndrying in the north and wetting in the central-eastern China along \r\nthe Yangtze river valley since the 1950s (Qian and Zhou, 2014; Zhou \r\net al., 2017b; Day et al., 2018), with a weakened EAsiaM low-level \r\ncirculation that penetrates less far into northern China, increased \r\nsurface pressure over north-east China and southward shift of the \r\njet stream (Song et al., 2014). The southward shift and enhancement \r\nof the jet stream explains the increase of rainfall especially from the \r\nMeiyu front (Day et al., 2018) at the expense of drying over north\u0002east China. "


id: 78e6d63a7b7130bf00e1a345e94eecb7
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18459
content:
"Anthropogenic factors such as GHGs and aerosols had an influence \r\non the EAsiaM changes (Figure 8.11; T. Wang et al., 2013; Song et al., \r\n2014; Xie et al., 2016; Chen and Sun, 2017; Ma et al., 2017; L. Zhang \r\net al., 2017; Day et al., 2018; Tian et al., 2018). Increased precipitation \r\nin the southern region has been linked to increased moisture flux \r\nconvergence driven by GHG forcing while changes in anthropogenic \r\naerosols have weakened the EAsiaM and reduced precipitation in \r\nthe northern regions (Tian et al., 2018). Aerosol-induced cooling, \r\nassociated atmospheric circulation changes and sea surface \r\ntemperature (SST) feedbacks weaken the EAsiaM and favour the \r\nobserved dry-north and wet-south pattern of rainfall anomalies \r\n(T. Wang et al., 2013; Song et al., 2014; L. Zhang et al., 2017; G. Chen \r\net al., 2018; X. Chen et al., 2018; Undorf et al., 2018b). "


id: 6583b8d9b5bea967e1886ca1f9f88af3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15126
content:
"Wetter conditions of the WAfriM prevailed later from the mid-to-late \r\n1990s, although the positive trend in precipitation started since the \r\nlate 1980s (see also Section 10.4.2.1) over the Sahel (high confidence) \r\nand in the Guinean coastal region (medium confidence), indicating \r\nthe geographical variation in the wetting recovery (Descroix et al., \r\n2015; Sanogo et al., 2015; Bodian et al., 2016; Nicholson et al., 2018). \r\nWhile the interannual and decadal variability of annual rainfall is not \r\nhomogeneous over the entire Sahel, the rainfall recovery was stronger \r\nin the east than in the west of the region (Section 10.4.2.1; Nicholson \r\net al., 2018). A  shift in the seasonality of the Sahelian rainfall, \r\nincluding delayed cessation has also been reported (Section 10.4.2.1; \r\nNicholson, 2013; Dunning et al., 2018). "


id: 11b9bdfee7d98f25cf9ca70bb8a60851
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 307
content:
"In the Sahel region, the emergence of this new rainfall regime is \r\nreflected in increased number of heavy and extreme events, compared \r\nto the 1970s-1980s, still not exceeding the values registered in the \r\n1950s to 1960s (Descroix et al., 2013, 2015; Panthou et al., 2014, \r\n2018; Sanogo et al., 2015), and in higher interannual variability \r\n(W. Zhang et al., 2017b; Akinsanola and Zhou, 2020) associated with "


id: d74d6e1d5b12e39d5ea9b32291383542
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35182
content:
"In summary, there is strong evidence of a  stronger EAsiaM and \r\nnorthward migration of the rainbelt during warmer climates based \r\non paleoclimate reconstructions. There is high confidence that \r\nanthropogenic forcing has been influencing historical EAsiaM \r\nchanges with drying in the north and wetting in the south observed "


id: 933a5865d8d4cc40210464cf8215a3b9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 23101
content:
"air associated with the Laurentide Ice Sheet (T. Bhattacharya et al., \r\n2017, 2018). The NAmerM strengthened until the mid-Holocene \r\nperiod, in response to ice-emsheet retreat and rising summer \r\ninsolation, but probably did not exceed the strength of the modern \r\nsystem (low confidence), as indicated by model simulations (Metcalfe \r\net al., 2015) and paleoclimatic reconstructions (Bhattacharya et al., \r\n2018). Paleoclimatic evidence from proxy datasets and mid-Pliocene \r\n(PlioMIP1) simulations suggest a wetter south-western USA during \r\nthat warmer period (A.M. Haywood et al., 2013; Pound et al., 2014; \r\nIbarra et al., 2018) but it is not clear whether this is due to increases \r\nof precipitation associated with the monsoon or occurring during the \r\nwinter season. "


id: 23f2f3aafdb45534756eb49db94c4f09
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 3507
content:
"During 1948-2010, trends of boreal summer precipitation amount \r\nwere significantly positive over New Mexico and the core NAmerM \r\nregion, but significantly negative over south-western Mexico (Hoell \r\net al., 2016). In addition, diverse datasets like CRU, CHIRPS and GPCP \r\nshow significant decreases of precipitation in parts of the south\u0002western USA and north-western Mexico, including the NAmerM \r\nregion (Cavazos et al., 2020; Ashfaq et al., 2021). Other studies \r\nsuggest a  strengthening of the NAmerM upper level anticyclone \r\nsince the mid-1970s, with a more frequent northward location (Diem \r\net al., 2013). Between 1910-2010, the number of precipitation \r\nevents increased across the northern Chihuahuan desert, within \r\nthe NAmerM domain, despite a  decrease in their magnitude, and \r\nthe length of extreme dry and wet periods also increased (Petrie \r\net al., 2014). "


id: 5c50d2c528666d4500066232dcbf0dba
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 13492
content:
"In summary, most regions of West Africa experienced a wet period \r\nin the mid-20th century followed by a very dry period in the 1970s \r\nand 1980s that is attributed to aerosol cooling of the NH (high \r\nconfidence). Recent estimates provide evidence of a WAfriM recovery \r\nfrom the mid-to-late 1990s, with more intense extreme events partly \r\ndue to the combined effects of increasing GHG and decreasing \r\nanthropogenic aerosols over Europe and North America (high \r\nconfidence). On paleoclimate time scales, there is high confidence\r\nthat the WAfriM strengthened during the early-to-mid Holocene \r\nin response to orbitally-forced enhancement of summer warming \r\nin the NH."


id: d1e4b4496feca617be1c384f7a33a09b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34276
content:
"Analyses from a 50-km resolution GCM indicate that the NAmerM \r\nresponse to CO2 is very sensitive to SST biases, showing reductions \r\nin summer NAmerM precipitation with increased CO2 when the SST \r\nbiases are small (Pascale et al., 2017) in contrast to CMIP5 models \r\n(Cook and Seager, 2013; Maloney et al., 2014; Torres-Alavez et al., \r\n2014; Hoell et al., 2016). The NAmerM has been shown to be also \r\nsensitive to sulphur dioxide (SO2) emissions (Garcia-Martinez \r\net al., 2020). "


id: ad444606a3300d3476c1640cfd1cc78d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27723
content:
"Since AR5, there have been updates on the observed long-term \r\nvariations and changes in the North American monsoon (NAmerM). \r\nDuring the Last Glacial Maximum (LGM; 21,000-19,000 years ago), \r\nthe NAmerM was substantially weaker due to cold, dry mid-latitude "


id: 7914bca303fd5e38eec8bf389d2ff967
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18489
content:
"In summary, both paleoclimate evidence and observations indicate \r\nan intensification of the NAmerM in a  warmer climate (medium \r\nconfidence). The intensification recorded since about the 1970s has \r\nbeen partly driven by GHG emissions (medium confidence). "


id: d428bb1bf740f42bb9172a3b5a7f4081
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34656
content:
"the domain considered for the SAmerM, confirming the occurrence \r\nof delayed onsets of the SAmerM since 1978 (Correa et al., 2021). \r\nCMIP5 simulations show trends toward delayed onsets of the \r\nSAmerM in association with anthropogenic forcing, although the \r\nsimulated trends underestimate the observed trends (Fu et al., 2013). \r\nTotal rainfall reductions are observed in the southern Amazon during \r\nSeptember-October-November after 1978 (Fu et al., 2013; Bonini \r\net al., 2014; Debortoli et al., 2015, 2016; Espinoza et al., 2019), \r\nconsistent with reductions in river discharge in the region (Molina\u0002Carpio et al., 2017; Espinoza et al., 2019; Heerspink et al., 2020)."


id: 75fa8f80b3c669966b678900c8ea431c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17980
content:
"In summary, there is high confidence that the SAmerM onset has \r\nbeen delayed since the late 1970s. This is reproduced by CMIP5 \r\nsimulations that consider anthropogenic forcing. There is also \r\nhigh confidence that precipitation during the dry-to-wet transition \r\nseason has been reduced over the southern Amazon. Paleoclimate \r\nreconstructions and simulations suggest a weaker SAmerM during \r\nwarmer epochs such as the Mid-Holocene or the 900-1100 period, \r\nand stronger monsoon during colder epochs such as the LGM or the \r\n1400-1600 period (high confidence). "


id: c50b0b027f3daf3adf5bb8f6cc99f019
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31977
content:
"Isotope records from caves in the central Peruvian Andes show \r\nthat the late Holocene (<3000 years ago) was characterized by \r\nmulti-decadal and centennial-scale periods of significant decline in \r\nintensity of the SAmerM (Bird et al., 2011a; Vuille et al., 2012). This \r\ncould be partly due to a reduction in the zonal SST gradient of the \r\nPacific Ocean, favouring El Nino-like conditions (Kanner et al., 2013). \r\nOther studies suggest increased SAmerM precipitation amount \r\nduring the Late Holocene, in association with the expansion of the \r\ntropical forest (Smith and Mayle, 2018). Well-dated equilibrium lines \r\nof glaciers during the deglaciation suggest that the AMOC enhances \r\nAtlantic moisture sources and precipitation amount increase over the \r\ntropical and southern Andes (Beniston et al., 2018). "


id: 90e31f4151d8c3ac501146324c2c250d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22699
content:
"Since AR5, several studies have examined observed variability \r\nand changes in the Australian and Maritime Continent monsoon \r\n(AusMCM) using paleoclimate records, instrumental observations \r\nand modeling studies (Denniston et al., 2016; Zhang and Moise, \r\n2016). Paleoclimate reconstructions and modelling indicate that \r\nthe Indo-Australian monsoon may vary in or out of phase with the \r\nEAsiaM, depending on whether there is a meridional displacement or \r\nexpansion of the tropical rainfall belt (Ayliffe et al., 2013; Denniston \r\net al., 2016). For instance, mid-Holocene simulations suggest that the \r\nAusMCM weakens and contracts due to a decreased net energy input \r\nand a weaker dynamic component (D'Agostino et al., 2020b). "


id: 2844fe3a852ec2152a6d18e301062167
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4281
content:
"Observations during 1979-2014 suggest that poleward shifts in the \r\nSouth Atlantic Convergence Zone (SACZ) noted in recent decades \r\n(Talento and Barreiro, 2018; Zilli et al., 2019), are associated with \r\nprecipitation amount decrease along the equatorward margin and \r\nincrease along the poleward margin of the convergenze zone (Zilli \r\net al., 2019). Several observational studies identified delayed onsets of \r\nthe SAmerM after 1978 related to longer dry seasons in the southern \r\nAmazon (Fu et al., 2013; Yin et al., 2014; Arias et al., 2015; Debortoli \r\net al., 2015; Arvor et al., 2017; Giraldez et al., 2020; Haghtalab et al., \r\n2020; Correa et al., 2021). In contrast, other studies indicate a trend \r\ntoward earlier onsets of the SAmerM (Jones and Carvalho, 2013). \r\nThese discrepancies are explained by the methodology used and "


id: fa007c69f47030259601ff8b841bd984
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41351
content:
"Rainfall increases have been observed over northern Australia since \r\nthe 1950s, with most of the increases occurring in the north-west \r\n(Dey et al., 2019a, b; Dai, 2021) and decreases observed in the north-"


id: b7b2b4e6bc07657b00fd51bef86554cb
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29535
content:
"east (J. Li et al., 2012) since the 1970s. There is also a trend towards \r\nmore intense convective rainfall from thunderstorms over northern \r\nAustralia (Dowdy, 2020). There is no consensus on the cause of the \r\nobserved Australian monsoon rainfall trends, with some studies \r\nsuggesting changes are due to altered circulation driving increased \r\nmoisture transport or increased frequency of the wettest synoptic \r\nregimes (Catto et al., 2012; Clark et al., 2018). Other studies find \r\nthat model simulations that include anthopogenic aerosols (Rotstayn \r\net al., 2012; Dey et al., 2019a) are better able to capture observed \r\nAustralian monsoon rainfall trends than simulations with natural or \r\nGHG forcing only (Knutson and Zeng, 2018). "


id: 7addb9339627e067d331733c568b4252
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 18817
content:
"is greater than what would be expected solely from changes in US \r\nlandfall frequency, suggesting the increasing role of TCs have in \r\ncausing heavy rainfall events (Kunkel et al., 2010). For example, there \r\nis evidence for an anthropogenic contribution to the extreme rainfall \r\nof Hurricane Harvey in 2017 (Emanuel, 2017; Risser and Wehner, \r\n2017; van Oldenborgh et al., 2017; Trenberth et al., 2018; S.-Y.S. Wang \r\net al., 2018). "


id: 2dec65e1e389bf6f16ca248ab352655
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5359
content:
"While TCs cause extreme local rainfall and flooding, they can be also \r\nan important contributor to annual precipitation and regional fresh \r\nwater resources (Hristova-Veleva et al., 2020). Transport of moisture \r\nby TCs is an important contributor for precipitation over the coastal \r\nareas of East Asia mostly from July through October, with the TC \r\nrainfall accounting for nearly 10% to 30% of the total rainfall in \r\nthe region (L. Guo et al., 2017). Local TC rainfall totals depend on \r\nrain-rate and translation speed (the speed of TC movement along \r\nthe storm track) with slow TCs such as Hurricane Harvey (2017), \r\nproviding a clear example of the effect of slow translation speed on \r\nlocal rainfall accumulation, with urbanization exacerbating the storm \r\ntotal rainfall and flooding (Section 11.7.1; W. Zhang et al., 2018). "


id: 951992a359ef6450528cc1195675e91f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 23437
content:
"The Maritime Continent (MC) experiences the influence of both the \r\nAsian and the Australian monsoons, with rainfall peaking during \r\nboreal winter/austral summer (Robertson et al., 2011). Reductions in \r\nland rainfall and marine cloudiness over the MC and weakening of \r\nsurface moisture flux convergence have been observed in the period \r\n1950-1999 (Tokinaga et al., 2012; Yoden et al., 2017). These trends \r\nare indicative of a slowdown of the Walker Circulation, with positive \r\nsea level pressure trends over the MC and negative trends over \r\nthe central equatorial Pacific (Tokinaga et al., 2012). More recently \r\n(1981-2014), a trend of increasing annual rainfall over large areas \r\nof the MC has been identified (Hassim and Timbal, 2019). Given the \r\nlarge variability in MC rainfall on interannual time scales, the choice \r\nof time period may influence the calculated rainfall trend (Hassim \r\nand Timbal, 2019)."


id: 3aef28088172f5a215f7d6f3ddd7cdf7
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7565
content:
"In addition to evidence that rain-rates have increased, there is \r\nevidence that TC translation speed has slowed globally (Kossin, \r\n2018) thus amplifying thermodynamic intensification of rainfall \r\nand may be linked to anthropogenic forcing (Gutmann et al., 2018). \r\nThis is limited evidence however, so there is medium confidence of \r\na detectable change in TC translation speed over the US. Since the \r\n1900s, and there is low confidence for a  global signal because of \r\nlimited agreement among models and due to data heterogeneity. \r\nHowever, the slowdown is consistent with theoretical and modelling \r\nstudies that indicate a general weakening of the tropical circulation \r\nwith warming that reduces the speed of the TC system (Chauvin \r\net al., 2017), though there is limited observational evidence\r\n(Sections 8.2.3.5 and 11.7.1). "


id: 310f28cf24fbd6b3dc87721473303431
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5881
content:
"During 1951-2007 daily rainfall extremes did not increase over \r\nthe MC, in contrast to the rest of South East Asia (Section 11.4.2; \r\nVillafuerte and Matsumoto, 2015). Rainfall extremes in Indonesia \r\nincreased in austral summer, as evidenced from station weather \r\nobservations for the period 1983-2012 (Supari et al., 2018). "


id: dacfc23735d4c3a7cf92daa8df9d0c3e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35792
content:
"In summary, notable rainfall increases have been observed in parts of \r\nnorthern Australia since the 1970s, although there is low confidence\r\nin the human contribution to these changes. Rainfall changes have \r\nbeen observed over the MC region but there is low confidence in \r\nthe identification of trends because of large variability at interannual \r\ntime scales."


id: b09a9fdb2c81303c9d1b372fd4f540d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28302
content:
"In summary, there is medium confidence of an observed increase in \r\nTC precipitation intensity in regions with sufficient data coverage \r\nRobust physical understanding (Section 8.2.3.2) and detailed singular \r\nevent attribution studies provide evidence that tropical cyclone \r\nrainfall has increased with a  warming climate (high confidence, \r\nSection 11.7.1.4)."


id: cecae82b638c6d11a04dcd98ed75a15e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 33719
content:
"The AR5 assessed low confidence in centennial changes in tropical \r\ncyclone (TC) activity globally, and in the attribution of observed \r\nchanges in TCs to anthropogenic forcing. Since AR5, there has been \r\nconsiderable progress in understanding the observed changes of TCs \r\nand an overall improved knowledge of the sensitivity of TCs to both \r\nGHG and aerosol forcing (Knutson et al., 2019; Sobel et al., 2019). "


id: 621bdc8537a330fa297487a252e90e90
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 14533
content:
"Stationary waves are planetary-scale waves that are approximately \r\nstable (stationary) in terms of geographic position, as opposed to \r\npropogating planetary waves, and are important both as part of the \r\nclimatological general circulation and seasonal and shorter-term \r\nanomalies. They are related to surface features including land-\r\nocean contrasts and major mountain ranges, as well as atmospheric \r\nfeatures including the jet stream, storm tracks, and blocking, which \r\nare considered separately in the following sections. While zonal mean \r\nchanges in P-E (precipitation minus evaporation) are dominated \r\nby thermodynamic effects (Section  8.2.2.1), changes in stationary \r\nwaves are of key importance in understanding zonal asymmetries \r\nin the water cycle response to global warming (Wills and Schneider, \r\n2015; Wills et al., 2019). The AR5 did not explicitly assess stationary "


id: 95587031f5ead984eb9c2e5964707816
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 23478
content:
"Although observational data limitations (Lau and Zhou, 2012) \r\ntend to limit detection of anthropogenic forced increases in TC \r\nprecipitation (Knutson et al., 2019), there is medium confidence that \r\nanthropogenic forcing has contributed to observed heavy rainfall \r\nevents over the USA associated with TCs (Kunkel et al., 2012) and \r\nother regions with sufficient data coverage (Section 11.7.1.2; Bindoff \r\net al., 2013). There has been increased frequency of TC heavy rainfall \r\nevents over several areas in the USA since the late 19th century that "


id: cca196cc659b3d93e3ac18d32bad7185
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 33325
content:
"Currently no consensus exists on observed trends in blocking during \r\n1979-2013. (Horton et al., 2015) identified increasing trends in \r\nanticyclonic circulation regimes based on geopotential height \r\nfields in the mid-troposphere, which may be partly related to the \r\ntropospheric warming itself and thus not represent real changes \r\nin the statistics of weather (Horton et al., 2015; Woollings et al., \r\n2018). Hanna et al. (2018) and (Davini and D'Andrea, 2020) reported \r\na  significant increase in the frequency of summer blocking over \r\nGreenland. A weakening of the zonal wind, eddy kinetic energy and \r\namplitude of Rossby waves in summer in the NH (Coumou et al., \r\n2015, Kornhuber et al., 2019) and an increased 'waviness' of the jet \r\nstream associated with Arctic warming (Francis and Vavrus, 2015; \r\nPfahl et al., 2015; Luo et al., 2019) have also been identified, which \r\nmay be linked to increased blocking. "


id: 59e13d95b0d25db98fbf9ad721649204
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 13054
content:
"waves, but noted changes in related circulation features such as \r\na likely poleward shift of the Northern Hemisphere (NH) storm tracks \r\nand an increase in frequency and eastward shift in North Atlantic \r\nblocking anticyclones, although there was low confidence in the \r\nglobal assessment of blocking."


id: a6322c74776fb16a6071affa970b2235
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26461
content:
"Since AR5, several studies have demonstrated a  link between \r\nstationary wave amplitude and wet and dry extremes in several \r\ndifferent regions of the NH (Liu et al., 2012; Coumou et al., 2014; \r\nScreen and Simmonds, 2014; Yuan et al., 2015) with changes in \r\nmoisture transport playing an important role (Yuan et al., 2015). \r\nA  'resonance mechanism' has been proposed for an increasing \r\namplitude of stationary waves (Petoukhov et al., 2013, 2016; Coumou \r\net al., 2014; Kornhuber et al., 2017) and several studies have linked \r\nincreasing amplitude of stationary waves to Arctic warming (Francis \r\nand Vavrus, 2012, 2015; Liu et al., 2012; Tang et al., 2014) as well \r\nas to global warming (Mann et al., 2017). However, other studies \r\nhave not identified an increase in stationary wave amplitude (Barnes, \r\n2013; Screen and Simmonds, 2013a, b). "


id: db6ac17a3a9e79912ebecd250662a7bb
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35877
content:
"There has been considerable work on linkages (teleconnections) \r\nbetween Arctic warming and the mid-latitude circulation (see also \r\nCross-Chapter Box 10.1). The limited amount of research on Southern \r\nHemisphere (SH) stationary waves suggests changes in high-latitude, \r\nmid-tropospheric stationary waves which influence Antarctic \r\nprecipitation (Turner et al., 2017) and changes in stratospheric \r\nstationary waves that are associated with ozone depletion rather than \r\nincreases in GHGs (L. Wang et al., 2013). The observed climatology \r\nof NH winter stationary waves is well-represented in the CMIP5 \r\nmulti-model mean (Wills et al., 2019) but individual models have \r\nimportant deficiencies in reproducing stationary wave variability (Lee \r\nand Black, 2013). In the SH, the observed climatology of stationary \r\nwaves in CMIP5 models has considerable bias in both phase and \r\namplitude (Garfinkel et al., 2020). A comprehensive assessment is not \r\nyet available for CMIP6 models."


id: 58cb84b67c07f317b52661d6e9213fe3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12865
content:
"In summary, no robust trend in atmospheric blocking has been \r\ndetected in modern reanalyses and in CMIP6 historical simulations \r\n(medium confidence). The lack of trend is explained by strong \r\ninternal variability and/or the competing effects of low-level Arctic \r\namplification and upper-level tropical amplification of the equator\u0002to-pole temperature gradient (medium confidence)."


id: 93917810edcef5af399c0ab49695b735
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 23168
content:
"In summary, there is low confidence in strengthened winter stationary \r\nwave activity over the North Atlantic, associated with increased \r\npoleward moisture fluxes east of North America There is medium \r\nconfidence in a recent amplification of the NH stationary waves in \r\nsummer, but no formal attribution to anthropogenic climate change."


id: ab370b45071f300df704e72d73063c9d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 27350
content:
"The AR5 indicated low confidence in long-term changes in the \r\nintensity of extratropical cyclones (ETC) over the 20th century derived \r\nfrom centennial reanalyses and storminess proxies based upon sea \r\nlevel pressure. This was confirmed by the SREX assessment that the \r\nmain Northern Hemisphere (NH) and Southern Hemisphere (SH) \r\nextratropical storm tracks likely experienced a poleward shift during \r\nthe last 50 years (Seneviratne et al., 2012) with low confidence, and \r\ninconsistencies within reanalysis datasets remain."


id: fb48e9026744a638dd9183aa2a681a52
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41585
content:
"Atmospheric blocking refers to persistent, semi-stationary weather \r\npatterns characterized by a high-pressure (anticyclonic) anomaly that \r\ninterrupts the westerly flow in the mid-latitudes of both hemispheres. \r\nBy redirecting the pathways of mid-latitude cyclones, blocking can \r\naffect the water cycle and lead to negative precipitation anomalies \r\nin the region of the blocking anticyclone and positive anomalies in \r\nthe surrounding areas (Sousa et al., 2017). In this way, blocking can \r\nalso be associated with extreme events such as heavy precipitation \r\n(Lenggenhager et al., 2019), drought (Schubert et al., 2014) and \r\nheatwaves (Miralles et al., 2014a). The AR5 reported low confidence in \r\nglobal-scale changes in blocking, due to methodological differences \r\nbetween studies."


id: 3c353c3df6b8ce6cc61fffc78a95cd3d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7784
content:
"Since AR5 there has been considerable progress in quantifying \r\nstorm track activity using multiple reanalysis products and different \r\nmethodologies (Hodges et al., 2011; Neu et al., 2013; Tilinina et al., \r\n2013; X.L. Wang et al., 2016). Over the NH increases in the total "


id: eb7b616cc414a25a5dab6030d7bebd04
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 38787
content:
"Figure 8.12 | Annual anomalies (with respect to the reference period 1979-2018) of the total number of extratropical cyclones (a, b) and of the number \r\nof deep cyclones (<980 hPa) (c, d) over the Northern (a, c) and the Southern (b, d) Hemispheres in different reanalyses (shown in colours in the legend).\r\nNote different vertical scales for panels (a, b) and (c, d). Thin lines indicate annual anomalies and bold lines indicate five-year running averages. (e, f) The number of reanalyses \r\n(out of five) simultaneously indicating statistically significant (90% level) linear trends of the same sign during 1979-2018 for JFM (January-February-March) over the Northern \r\nHemisphere (e) and over the Southern Hemisphere (f). Updated from Tilinina et al. (2013). Further details on data sources and processing are available in the chapter data table \r\n(Table 8.SM.1)."


id: b1d0b7f702e79d1267ac206394b8e440
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28504
content:
"Central and South European precipitation anomalies. Over centennial \r\ntime scales, Gan and Wu (2014) reported an intensification of storm \r\ntracks in the poleward and downstream regions of the North Pacific \r\nand North Atlantic upper troposphere using the NOAA-CIRES-DOE \r\nTwentieth Century Reanalysis. Poleward migration of the SH storm \r\ntracks (Grise et al., 2014; X.L. Wang et al., 2016; Dowdy et al., 2019) \r\nwas identified during the austral summer and is closely associated \r\nwith cyclone-associated frontal activity (Solman and Orlanski, 2014, \r\n2016) and cloud cover (Bender et al., 2012; Norris et al., 2016)."


id: 1eb07bbcbf824101107acbb964750a57
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2602
content:
"The representation of ETCs in both climate models and reanalyses \r\nis resolution-dependent, hence changes must be assessed with \r\ncaution (Section  3.3.3.3). In particular, CMIP5 models show \r\na  systematic underestimation of the intensity of ETCs (Zappa \r\net al., 2014), a  feature that is partially related to their relatively \r\ncoarse resolution or other possible deficiencies such as an excess \r\nof dissipation (Chang et al., 2013). The best representation of ETCs \r\nand their intensity in the  North Atlantic are provided by relatively \r\nhigh horizontal resolution CMIP5 models (Zappa et al., 2014). Using \r\na single high-resolution climate model, (Hawcroft et al., 2016) showed \r\nthat precipitation amount associated with ETCs was generally well \r\nsimulated, though with too much precipitation during the strongest \r\nECTs compared with observed estimations."


id: 56d1ea452804dbcb6e9dcd1946c22b69
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 12523
content:
"In summary, there is low confidence in recent changes in the total \r\nnumber of extratropical cyclones over both hemispheres. It is as likely \r\nas not that the number of deep cyclones over the NH has decreased \r\nafter 1979 and it is likely that the number of deep extratropical \r\ncyclones increased over the same period in the SH. It is likely that \r\nextratropical cyclone activity in the SH has intensified during austral \r\nsummer with no significant changes in austral winter. There is \r\nmedium confidence that boreal-winter storm tracks during the last \r\ndecades experienced poleward shifts over the NH and SH oceans. \r\nThere is low confidence of changes in extratropical cyclone activity \r\nprior 1979 due to inhomogeneities in the intrumental records and \r\nmodern reanalyses. "


id: d71ef64bb942ddef1661663b6ee1a8e4
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35157
content:
"Analysis of storm track activity over longer periods suffers from \r\nuncertainties associated with changing data assimilation and \r\nobservations before and during the satellite era, resulting in in \r\nhomogeneities and discontinuities in centennial reanalyses (Krueger \r\net al., 2013; X.L. Wang et al., 2013, 2016; Chang and Yau, 2016; \r\nVarino et al., 2019). Feser et al. (2015) reviewed multiple storm track \r\nrecords for the Atlantic-European sector and demonstrated growing \r\nstorm activity north of 55degN from the 1970s to the mid-1990s with \r\ndeclining trend thereafter, sugesting strong inter-decadal variability \r\nin storm track activity. This was also confirmed by Krueger et al. \r\n(2019) from the analysis of geostrophic winds derived from sea level \r\npressure gradients. "


id: 40ab68926f8a98f772d38fc88d62b09a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8561
content:
"Poleward deflection of mostly oceanic winter storm tracks since \r\n1979 was reported in both the North Atlantic and North Pacific \r\n(Tilinina et al., 2013; J. Wang et al., 2017). This large-scale tendency \r\nhas regional variations and may be seasonally dependent. Wise and \r\nDannenberg (2017) reported a  southward shift in the east Pacific \r\nstorm track from the 1950s to mid-1980s followed by northward \r\ndeflection in the later decades. (King et al., 2019) reported an \r\nassociation of Atlantic storm track migrations with SSW events with "


id: a8ab339704f50d7ad3238c259083844d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26880
content:
"Greenland and New Zealand (Bozkurt et al., 2018; Mattingly et al., \r\n2018; Little et al., 2019), contributing about 45-60% of total annual \r\nprecipitation in subtropical South America (Viale et al., 2018). They \r\nalso transport moisture from South America to the western and \r\ncentral South Atlantic, feeding the ARs that reach the west coast \r\nof South Africa (Ramos et al., 2019). However, the estimation of \r\nprecipitation rate from ARs can have large uncertainties, especially \r\nas ARs hit topographically complex coastal regions (Behrangi \r\net al., 2016), which can cause complexities in quantifying AR-related \r\nprecipitation."


id: 70c97f4ea4dc4ed30e3cfb0e4a585b4d
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 17104
content:
"Analysis of observed trends in the characteristics of ARs has been \r\nlimited. Gershunov et al. (2017) and Sharma and Dery (2019) have \r\nshown a rising trend in land-falling AR activity over the west coast \r\nof North American since 1948. (Gonzales et al., 2019) have also \r\ndocumented a  seasonally-asymmetric warming of ARs affecting \r\nthe West Coast of the USA since 1980, which has hydrological \r\nimplications for the timing and magnitude of regional runoff. Longer\u0002term paleoclimate analysis of ARs is even more limited, although \r\nLora et al. (2017) reported that in the last glacial maximum, AR \r\nlandfalls over the North American west coast were shifted southward \r\ncompared to the present conditions. "


id: 83327f3a774d1303caf6ed3fc18e7ec3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20208
content:
"In summary, it is likely that there was an increasing trend in the \r\nAR activity in the eastern North Pacific since the mid-20th century. \r\nHowever, there is low confidence in the magnitude of this trend \r\nand no formal attribution, although such an increase in activity is \r\nconsistent with the expected and observed increase in precipitable \r\nwater associated with human-induced global warming. "


id: 39857e118d89aa9454e55aadc5f24974
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 7331
content:
"Following on from the assessment in Chapters 2 and 3, this section \r\nconsiders changes in modes of variability at seasonal to interannual \r\ntime scales in terms of their implications on recent water cycle \r\nchanges. These modes are described in details in Technical Annex IV."


id: af63e643a886e3b5e6adc3870234381b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 28087
content:
"The amplitude of the El  Nino-Southern Oscillation (ENSO; Section \r\nAIV.2.3) variability has increased since 1950 (Section 2.4.2) but there \r\nis no clear evidence of human influence (Sections 2.4.2 and 3.7.3). "


id: db59b1639bf27db1e50b370dee0b79b9
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35862
content:
"ENSO influences precipitation and evaporation dynamics, river flow \r\nand flooding at a global scale (Figure 3.37; Ward et al., 2014, 2016; \r\nMartens et al., 2018). Reconstruction (1804-2005) of Thailand's \r\nChao Praya River peak season streamflow displays a  strong \r\ncorrelation with ENSO (Xu et al., 2019). Based on water storage \r\nestimates from 2002 to 2015, drought conditions over the Yangtze \r\nRiver basin followed La Nina events and flood conditions followed \r\nEl Nino events (Z. Zhang et al., 2015). Strong correlation between \r\nENSO and terrestrial water storage has been identified mostly in the \r\nsubtropics but with diverse intensities and time lags depending on \r\nthe region (Ni et al., 2018). The likelihood of increased/decreased \r\nflood hazard during ENSO events has a complex spatial pattern with \r\nlarge uncertainties (Emerton et al., 2017). "


id: c480e2c0d08c5e43b735752afedfe78c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 31876
content:
"Intraseasonal variability, like the Madden Julian Oscillation (MJO, \r\nSection AIV.2.8) and the Boreal Summer Intraseasonal Oscillation \r\n(BSISO), are highly relevant to the water cycle (Maloney and Hartmann, \r\n2000; Lee et al., 2013; Yoshida et al., 2014; Nakano et al., 2015). Since \r\nAR5, studies on MJO teleconnections within the tropics and from "


id: 1f2d455377286f756ba168521c2f716
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2693
content:
"have been developed since its discovery, a better understanding of \r\nits dynamics is still needed (Jiang et al., 2020; Zhang et al., 2020). \r\nFurthermore, metrics based on dynamical processes are needed to \r\nassess model simulations of these events (Stechmann and Hottovy, \r\n2017; B.  Wang et al., 2018) as well as related teleconnections \r\n(J. Wang et al., 2020)."


id: 8502116eee24cdbff77ea9aa60beb29c
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20542
content:
"the tropics to higher latitudes have continued (Guan et al., 2012; \r\nMundhenk et al., 2018; Tseng et al., 2019; Aberson and Kaplan, \r\n2020; Finney et al., 2020b; Fowler and Pritchard, 2020; Fromang and \r\nRiviere, 2020). "


id: bf39fda4cbbb313f57e94b22ec9d290e
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 30913
content:
"The strength and frequency of the MJO have increased over the past \r\ncentury (medium confidence) (Oliver and Thompson, 2012; Maloney \r\net al., 2019; Cui et al., 2020) because of global warming (Arnold \r\net al., 2015; Carlson and Caballero, 2016; Wolding et al., 2017; \r\nMaloney et al., 2019). A 20th century reconstruction suggests a 13% \r\nincrease of the MJO amplitude (Oliver and Thompson, 2012), with \r\ndifferences in seasonal variability (Tao et al., 2015; Z. Wang et al., \r\n2020). However, up to half of changes recorded during the second \r\nhalf of the 20th century could be due to internal variability (Schubert \r\net al., 2013). Other observed changes in MJO characteristics include \r\na  decrease (by three to four days) in the residence time over the \r\nIndian Ocean but an increase (by five to six days) over the Indo\u0002Pacific and Maritime Continent sectors (Roxy et al., 2019). "


id: 508372635db7ba6c22e81bde247d7ec0
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11438
content:
"In summary, multiple water cycle changes related to ENSO and IOD \r\nteleconnections have been observed across the 20th century (high \r\nconfidence), mostly dominated by interannual to multi-decadal \r\nvariations. The MJO amplitude has increased in the second half of \r\nthe 20th century partly because of anthropogenic global warming \r\n(medium confidence) altering regional precipitation signals."


id: 4f8b3e376c985e13695105e69053fe4b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11281
content:
"Consequences of these changes are increased rainfall over South \r\nEast Asia, northern Australia, south-west Africa and the Amazon, \r\nand drying over the west coast of the USA and Equador (Roxy et al., \r\n2019). During the austral summer, air-sea interactions and location \r\nof the MJO active phase are important to modulate the strength of \r\nthe rainfall response in the South Atlantic Convergence Zone (Shimizu \r\nand Ambrizzi, 2016; Alvarez et al., 2017), including its southward \r\nshift (Barreiro et al., 2019). In the austral winter, the intraseasonal \r\nvariability is mostly influential over regions of the Amazonian basin \r\n(Mayta et al., 2019). Some MJO phases are particularly effective in \r\nconjuction with tropical cyclones in enhancing westerly moisture \r\nfluxes towards East Africa (Finney et al., 2020b)."


id: 43cb490db642ebed23af75c0286e5b49
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9155
content:
"with other large-scale modes of climate variability, like ENSO (Fogt \r\net al., 2011) and the Indian Ocean Dipole (Hoell et al., 2017a), are \r\nresponsible for fluctuations in southern African rainfall (Nash, 2017) \r\nand southern South America (Gergis and Henley, 2017). In May, the \r\nSAM can trigger a southern Indian Ocean Dipole SSTA favoring more \r\nor less precipitation over the Indian sub-continent and adjacent \r\nareas (Dou et al., 2017), also affecting subsequent summer monsoon \r\nin the South China Sea (T.  Liu et al., 2018). Over South America, \r\na positive SAM is associated with dry conditions (Holz et al., 2017) \r\ndue to reduced frontal and orographic precipitation and weakening \r\nof moisture convergence. Regions particularly affected include Chile \r\n(Boisier et al., 2018) and the rivers of central Patagonia (Rivera \r\net al., 2018). "


id: 6841afe71b7892dd64f90827bc3b46ec
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 15612
content:
"As discussed in 8.3.1.1, the definition of global water cycle intensity \r\nvaries from the simple metric of increases in global mean precipitation \r\nto broader joint considerations of water vapour and its transport, \r\nprecipitation minus evaporation (P-E) rates and continental runoff \r\n(Figure 8.1). The AR5 determined that globally averaged precipitation \r\nis virtually certain to increase with temperature and that there is high \r\nconfidence that the contrast of annual mean precipitation between \r\ndry and wet regions and seasons will increase over most of the globe \r\nas temperatures and moisture transports increase (Collins et al., \r\n2013). The AR5 also highlighted that continued ocean warming for \r\na  few decades after GHG forcing stabilizes or begins to decrease \r\nwill also lead to further increases in global mean precipitation \r\nand evaporation."


id: 91e18937ace6dfe956bad0154a6593e3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 22883
content:
"In summary, while the attribution of 20th century variations of \r\nthe NAM/NAO is still unclear, there is a  strong relationship with \r\nprecipitation changes over Europe and in the Mediterranean region \r\n(high confidence). SAM teleconnections are associated with changes \r\nin moisture transport and extend to South America, Australia and \r\nAntarctica (high confidence) with documented drying occurring as \r\na result of the very likely human-induced SAM trend toward its positive \r\nphase observed from the 1970s until the 1990s (Section 3.7.2)."


id: 452b034c32ee13ba367f2eef211bcae2
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 9396
content:
"We consider global and regional climate projections of the \r\nwater  cycle, assessing projected changes in each component of \r\nthe water cycle  (Section  8.4.1) and the global-scale and regional \r\nphenomena that directly impact it (Section 8.4.2). "


id: dfda0d1e004a4d1d391922f956139856
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36626
content:
"CMIP6 climate models continue to project a  steady increase in \r\nglobal mean column-integrated water vapour by around 6-13% \r\nby 2041-2060 and 5-32% by 2081-2100, depending on scenario \r\n(Table  8.1). This is consistent with projected atmospheric warming \r\n(Section  4.5.1.2) and the Clausius-Clapeyron relationship \r\n(Section 8.2.1) where every degree Celsius of warming is associated \r\nwith an approximate 7% increase in atmospheric moisture in the lower \r\natmospheric layers where most of the water vapour is concentrated. \r\nThis increase sustains a positive feedback on anthropogenic global \r\nwarming (Section  7.4.2.2). In contrast, the response of clouds is "


id: 868a958a64514e2af287fed5bae8ef92
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 20839
content:
"much more spatially heterogeneous, microphysically complex, and \r\nmodel-dependent so that the projected cloud feedbacks remain a key \r\nuncertainty for constraining climate sensitivity (Section 7.4.2.4). "


id: 2036ec35aedc4ff7600bd6e357f8a7c3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2883
content:
"CMIP6 models project an overall decrease in near-surface relative \r\nhumidity over land, although with some regional and seasonal \r\nvariations in their response (Figure 4.26). Regional changes in near\u0002surface humidity over land are dominated by thermodynamic processes \r\nand are primarily controlled by moisture transport from the warming \r\nocean (Chadwick et al., 2016a). Increases in specific humidity lower "


id: d35c19cf646111a9e054a5feef9cdb80
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34528
content:
"than the thermodynamic rate are explained by greater warming over \r\nland than ocean and modulated by land-atmosphere feedbacks such \r\nas soil moisture and plant stomatal changes (Section 8.2.2.1; Berg \r\net al., 2017; Douville et al., 2020). This explains why climate models \r\ncontinue to project a  contrasting response of near-surface relative \r\nhumidity, with a  slight and possibly overestimated increase over \r\nthe oceans and a consistent but possibly underestimated decrease \r\nover land (Byrne and O'Gorman, 2016; Douville and Plazzotta, 2017; \r\nR. Zhang et al., 2018)."


id: ef665761c696440028b8d6516368ead3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 39487
content:
"over most of the globe as temperatures increase (high confidence), \r\nbut with large regional variations. Precipitation over the high \r\nlatitudes, equatorial Pacific Ocean, mid-latitude wet regions, and \r\nmonsoon regions were assessed as likely to increase under the \r\nRCP8.5 scenario, and in many mid-latitude and subtropical dry \r\nregions as likely to decrease (AR5 Chapters 7, 12, and 14). Extreme \r\nprecipitation over most mid-latitude land areas and wet tropical \r\nregions was assessed as very likely to become more intense and \r\nmore frequent."


id: 278d636da4aaa3fb41578f83012b18cc
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4137
content:
"In summary, there is high confidence in continued increases in global \r\nmean column integrated water vapour and near-surface specific \r\nhumidity over land. There is medium confidence in region and season\u0002dependent decreases in near-surface relative humidity over land, due \r\nto the complex physical processes involved. In general, there will be \r\nincreases in moisture transport into storm systems, monsoons and \r\nhigh latitudes (medium confidence)."


id: a79957e4ea4cfe98748f714984b9a3bb
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 26699
content:
"This section assesses projected changes in precipitation at regional \r\nscales. Note that changes in precipitation seasonality are assessed \r\nin Box 8.2 and that changes in regional monsoons are assessed in \r\nSection 8.4.2.4, where both circulation and rainfall are considered. \r\nFurther assessments of regional projections of precipitation are \r\npresented in Chapters 10, 12 and the Atlas, while a comprehensive \r\nassessment of changes in precipitation extremes is provided in \r\nChapter 11."


id: 879a4309b3f6aa4997bdf8f28bc35e68
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 21014
content:
"annual mean rainfall is likely to decrease include southern Africa, \r\ncoastal West Africa, Amazonia, south-western Australia, Central \r\nAmerica, south-western South America, and the Mediterranean."


id: d4ebea1c79a407bb7e4f025b0a9a076
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 34779
content:
"The AR5 identified that high-latitude precipitation increase may lead \r\nto an increase in snowfall in the coldest regions and a decrease of \r\nsnowfall in warmer regions due to a decreased number of freezing \r\ndays. The fraction of precipitation falling as snow and the duration \r\nof snow cover was projected to decrease. Heavy snowfall events \r\nglobally are not expected to decrease significantly with warming \r\nas they occur close to the water freezing point, which will migrate \r\npoleward and in altitude (O'Gorman, 2014; Turner et al., 2019). There \r\nare only a  small number of studies evaluating the implications of \r\nthis mechanism in specific regions. A study for the north-eastern USA \r\nindicates smaller reductions for major snowfall events against the \r\nbroader decline in snowfall expected from thermodynamic effects \r\n(Bintanja and Andry, 2017). Arctic snowfall is projected to decrease \r\nas rainfall makes up more of the precipitation (Zarzycki, 2018). "


id: ded6e40035f7ffca1c2b57384be358ee
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36470
content:
"Beyond annual or seasonal mean precipitation amounts, an implication \r\nof the parallel intensification of the global water cycle and of the \r\nincreased residence time of atmospheric water vapour (Section 8.2.1) \r\nis that the distribution of daily and sub-daily precipitation intensities \r\nwill experience significant changes (Pendergrass and Hartmann, \r\n2014b; Pendergrass et al., 2015; Bador et al., 2018; Douville and John, \r\n2021), with fewer but potentially stronger events (high confidence)"


id: 2af148fa81180d4c5c0ecf7abbf0e5a8
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 4792
content:
"(Section  4.3.3). CMIP6 projections show that in the long-term \r\nmore drier days but more intense single events of precipitation are \r\nexpected, regardless of scenario (Figure 8.15). Over almost all land \r\nregions, it is very likely that extreme precipitation will intensify at \r\na rate close to the 7% degC-1 of global warming, but with large spatial \r\ndifferences (Sections  11.4 and 8.2.3.2). The projected increase in \r\nprecipitable water is expected to lead to an increase in the highest "


id: e1ed18753f81ec883da4fe39ae39c94f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37032
content:
"Projected water cycle changes as a function of global warming\nin SSP5-8.5 and over 20-year overlapping periods, starting from [2021-2040], relative to 1850-1900\n\f"


id: 5188cff67efad03f856751c89fed7676
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 11623
content:
"possible precipitation intensities and an increase in the probability \r\nof occurrence of extreme precipitation events on the global scale \r\n(Neelin et al., 2017), regardless of how annual-mean precipitation \r\nchanges (O'Gorman and Schneider, 2009; O'Gorman, 2015). The \r\nprojected increase in heavy precipitation intensity is also found for "


id: b6eafe0194578ade8e4b222893edc0ab
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 29386
content:
"An increase in the number of dry days is also projected in several \r\nregions of the world (Polade et al., 2014; Berthou et al., 2019a), "


id: db81d5e548ab8be24e41f5a5f0023c5b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 35898
content:
"which can dominate the annual precipitation change at least \r\nin the subtropics (Polade et al., 2014; Douville and John, 2021). \r\nThese findings are supported by CMIP6 projections showing \r\na  widespread increase in daily mean precipitation intensity over \r\nland (Figure 8.15b,d,f) as well as an increase in the number of dry \r\ndays in the subtropics and over Amazonia and Central America \r\n(Figure 8.15a,b,c). Such changes in precipitation regimes, as well as \r\nthe general increase in the frequency and intensity of precipitation \r\nextremes (Section  11.4.5), contribute to an overall increase in \r\nprecipitation variability (Polade et al., 2014; Pendergrass et al., \r\n2017; Douville and John, 2021). This is also found in CMIP6 models, \r\nwhich show a stronger increase of interannual variability than in \r\nseasonal mean precipitation changes, apart from in the winter \r\nextratropics where both quantities increase at the same rate with \r\nincreasing global warming levels (Figure 8.16). "


id: e3915a95464e552f378c57c36ec3d693
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 37330
content:
"Large differences have been found across seven global precipitation datasets, with no region showing a  consistent, statistically \r\nsignificant, positive or negative trend over the last three decades (X. Tan et al., 2020). Regional studies suggest that observed changes \r\nin precipitation seasonality are neither uniform nor stable across the 20th century (X. Li et al., 2016; Mallakpour and Villarini, 2017; \r\nSahany et al., 2018; Deng et al., 2019). Since the 1980s, there is growing evidence that contrasts between wet and dry regimes, \r\nincluding seasonality, have increased (Liu and Allan, 2013; Polson et al., 2013; Murray-Tortarolo et al., 2016; Tapiador et al., 2016; \r\nGallego et al., 2017; Polson and Hegerl, 2017; Barkhordarian et al., 2018; Lan et al., 2019; Liang et al., 2020; Schurer et al., 2020). "


id: 306fc1c3c3ca8abad4b040dbe90d461a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5778
content:
"In northern high latitudes, a shorter snow season (X. Zeng et al., 2018) is mainly due to an earlier onset of spring snowmelt (Peng et al., \r\n2013) which has been attributed to anthropogenic climate change (Najafi et al., 2016). Changes in snow seasonality affect streamflow \r\nat the regional scale, with an earlier peak in spring and a possible decrease of low-level flow in summer (Berghuijs et al., 2014; Kang \r\net al., 2016; Dudley et al., 2017), while glacier shrinking can also alter the low-level flow in mountain catchments (Lutz et al., 2014; Milner "


id: feba1cd178b8dc6732dc18fa7c47eb46
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 42204
content:
"et al., 2017; Huss and Hock, 2018). This can be partly ameliorated by water management in regulated catchments (Arheimer et al., 2017), \r\nbut not in large river basins such as the Amazon which also shows an increased seasonality of discharge since 1979 (Liang et al., 2020)."


id: f87ee82c77de1f97439e36c4079baaa3
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 41077
content:
"Increasing aridity contrasts between wet and dry seasons over the late 20th century have been suggested (Kumar et al., 2015), with \r\na human-induced decrease of water availability during the dry season over Europe, western North America, northern Asia, southern \r\nSouth America, Australia and eastern Africa (Padron et al., 2020). Seasonal contrasts in microwave surface soil moisture measurements \r\nhave also increased over 1979-2016 (Pan et al., 2019). Terrestrial water storage variations derived from gravimetric measurements \r\nsince 2003 show a strong seasonality which is underestimated by global hydrological models (Scanlon et al., 2019) and whose multi\u0002decadal trends are difficult to interpret given the direct effect of enhanced water use (Rodell et al., 2018; Scanlon et al., 2018)."


id: f7777b8dde9aa457dbbf1d1e3dbab97b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 40911
content:
"In summary, there is medium confidence that the annual range of precipitation has increased since the 1980s, at least in subtropical \r\nregions and over the Amazon. There is low confidence that this increase is due to human influence and that GHG forcing has already \r\naltered the timing or duration of wet seasons. There is high confidence that the human-induced retreat of the springtime snow cover \r\nand melting of glaciers have already contributed to changes in streamflow seasonality in high-latitude and low-elevation mountain \r\ncatchments, and medium confidence that human activities have also contributed to an increased seasonality of water availability, \r\nincluding a drier dry season, in the extratropics."


id: 424d57fe88c2d979b1f8788449257982
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 8862
content:
"The AR5 reported with high confidence that the contrast between wet and dry seasons will generally increase with global warming \r\nand that monsoon onset dates will likely become earlier or show little change, while monsoon retreat dates will likely be delayed, \r\nresulting in a lengthening of the wet season in many regions. "


id: c7e9621eabab7bb75b04615026b9496b
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 32481
content:
"In summary, the annual range of precipitation, water availability and streamflow will increase with global warming over subtropical \r\nregions and the Amazon (medium confidence), especially around the Mediterranean and across southern Africa (high confidence). The \r\ncontrast between the wettest and driest month of the year is likely to increase by 3-5% degC-1 with global warming in most monsoon \r\nregions, in terms of precipitation, water availability (P-E) and runoff (medium confidence). There is medium confidence that the \r\nmonsoon season could be delayed in a warmer climate in the Sahel. There is high confidence of earlier snowmelt. "


id: dd50d8bd246007fffeb6a2f02833a97a
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 36199
content:
"Analysis of CMIP5 models suggests that atmospheric evaporative \r\ndemand will increase over most areas of the world in high-emissions \r\nscenarios (virtually certain), mostly as a consequence of an increase \r\nin vapour pressure deficit (Scheff and Frierson, 2014, 2015; Greve \r\nand Seneviratne, 2015; Vicente-Serrano et al., 2020). CMIP5 models \r\nalso project an increase in evapotranspiration over most land areas \r\n(medium confidence) (Laine et al., 2014). However, regional changes "


id: 1e176ddc8dce8030add8fc9fd4292443
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 2491
content:
"Since AR5, there is a  growing body of evidence suggesting that \r\nfuture projections in evapotranspiration are driven by changes in \r\ntemperature and relative humidity (Laine et al., 2014; Pan et al., \r\n2015; Ukkola et al., 2016a), as well as precipitation patterns, as \r\nfound in AR5."


id: 2f56586e925c78c5eb56db6c3be1c91f
created_at: 2023-04-19 13:21:37
updated_at: 2023-04-19 13:21:37
content_type: text
index: climate_gpt_v2
vector_id: 5593
content:
"Figure 8.17 | Projected long-term relative changes in seasonal mean evapotranspiration. Global maps of projected relative changes (%) in seasonal mean of \r\nsurface evapotranspiration for December-January-February (DJF; left panels) and June-July-August (JJA; right panels) averaged across available CMIP6 models (number \r\nprovided at the top right of each panel) for SSP1.2-6 (a, b) SSP2-4.5 (c, d) and SSP5-8.5 (e, f) scenario respectively. All changes are estimated in 2081-2100 relative to \r\n1995-2014. Uncertainty is represented using the simple approach. No overlay indicates regions with high model agreement, where >=80% of models agree on sign of change; \r\ndiagonal lines indicate regions with low model agreement, where <80% of models agree on sign of change. For more information on the simple approach, please refer to the \r\nCross-Chapter Box Atlas.1. Further details on data sources and processing are available in the chapter data table (Table 8.SM.1)."


id: 84cd1f8107dc2c402bd14ab74526a140
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 20508
content:
"confidence that warming of 2degC would increase the fraction of global \r\narea affected by flood hazard relative to warming of 1.5degC. Projected \r\nclimate-driven changes to runoff, streamflow, and flooding will occur \r\nin the context of potential human-caused land-use and land-cover \r\nchanges, which can have a large influence on surface water (Sterling \r\net al., 2013) but which have considerable uncertainty in projections \r\n(Prestele et al., 2016)."


id: 5a1dde14eb2aa4aec345cd4854b28744
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 13106
content:
"CMIP6 models project a  geographical pattern of changes in \r\nevapotranspiration similar to previous generation models \r\n(Figure  8.17), although the magnitude is generally larger than \r\nfound for CMIP5 projections (X. Liu et al., 2020). There is, however, \r\na strong seasonality in many regions, with a larger relative increase \r\nin the winter season of the Northern Hemisphere (NH) and smaller \r\nrelative changes in the summer (Figure  8.17). Evapotranspiration \r\nincreases in most land regions, except in areas that are projected to \r\nbecome moisture-limited (due to reduced precipitation and increased \r\nevaporative demand), such as the Mediterranean, South Africa, and \r\nthe Amazonian basin (medium confidence). The patterns of change \r\nincrease in magnitude from low to high-emissions SSP scenarios \r\n(medium confidence)."


id: bb049ce7b56ffff3f34207d7766f8691
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 30120
content:
"In summary, future projections indicate that anthropogenic \r\nforcings will drive an increase in global mean evaporation over \r\nmost oceanic areas (high confidence) (Figure  8.17), an increase \r\nin global atmospheric demand (virtually certain) and an increase \r\nin evapotranspiration over most land areas, with the exception of \r\nmoisture-limited regions (medium confidence). However, substantial \r\nuncertainties in projections of evapotranspiration, especially at \r\nseasonal and regional scales, remain (see also Section 8.2.3.3 and \r\nCross-Chapter Box 5.1)."


id: e4487429562574da4f0a312533a1d878
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 37461
content:
"Changes in streamflow vary regionally and increase in magnitude \r\nwith emissions scenarios, as with runoff (although the two are not \r\nequivalent, as runoff includes both surface runoff and streamflow). \r\nStreamflow projections additionally require the use of hydrologic \r\nmodels forced by the output from climate models and have not been \r\nas widely explored as they are not variables directly included in climate \r\nmodels. On an annual basis, streamflows have been projected to \r\nincrease in the northern high latitudes and tropical Asia and Africa, and \r\nto decrease in the Mediterranean, tropical South America, and South \r\nAfrica (Doll et al., 2018). For a 4degC global warming, half of the global \r\nland area is projected to be exposed to increased high flows (average \r\nincrease 25%), while about 60% may be exposed to decreased low \r\nflows (average decrease 50%) (Asadieh and Krakauer, 2017). "


id: b1d1cc5ca0455eb680d98989225baf01
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 28505
content:
"Changes in the seasonality of runoff and streamflow are assessed \r\nin Box  8.2. The seasonality of runoff and streamflow (calculated \r\nas the annual difference between the wettest and driest months \r\nof the year), is expected to increase with global warming in the \r\nsubtropics, especially in the Mediterranean and southern Africa with \r\nhigh confidence, and in the Amazon with medium confidence. For "


id: 889f3fe330bb8ce823fca6fd20b865a
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 21198
content:
"basins, projected runoff changes show an increase until a maximum \r\nis reached, beyond which runoff steadily declines because of limited \r\nice volumes (Huss and Hock, 2018)."


id: 5f42804b8d8c05505e53e5139e171044
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 14067
content:
"regions where snowmelt is an important contributor to streamflow, \r\nthere is high confidence that snowmelt occurring earlier in the \r\nyear will result in peak flows also occurring earlier in the year, and \r\nmedium confidence that reduced snow volume and the weaker solar \r\nradiation earlier in the year will reduce the most intense flows (see \r\nSection 8.2.3.1). In roughly half of 56 large-scale glacierized drainage "


id: b6f49d208d610765fe5424396eae3c7c
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 29396
content:
"As future changes in flood events are assessed in Chapters 9, 11 \r\nand 12, only a summary is presented here. There are a number of "


id: 18018578718e58410e1439db4647af2
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 1427
content:
"with the emissions scenario (high confidence) (Figure  8.19; Scheff \r\nand Frierson, 2014, 2015; Vicente-Serrano et al., 2020). Even under \r\na  low-emissions scenario (SSP1-2.6), projections of soil moisture \r\nshow significant decreases in the Mediterranean, southern Africa, \r\nand the Amazonian basin (high confidence) (Figure 8.19). Under mid\u0002and high-emissions scenarios (SSP2-4.5 and SSP5-8.5), coherent \r\ndeclines emerge across Europe, westernmost North Africa, south\u0002western Australia, Central America, south-western North America, \r\nand south-western South America (high confidence) (Figure  8.19; \r\nCook et al., 2020). Compared to CMIP5 results, CMIP6 models exhibit \r\nmore consistent drying in the Amazonian basin (Parsons, 2020), \r\nmore extensive declines in total soil moisture in Siberia (Cook et al., \r\n2020), and stronger declines in westernmost North Africa and south\u0002western Australia (Figure 8.19). "


id: fdade11673244ed8e65696ae9284d7de
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 41988
content:
"The AR5 concluded that regional to global-scale projections of \r\naridity and drought remained relatively uncertain compared to other \r\naspects of the water cycle. It reported that there is a likely increase in \r\ndrought occurrence (medium confidence) by 2100 in regions that are \r\ncurrently drought-prone under the RCP8.5 scenario due to projected \r\ndecreases in soil moisture. It stated that it is likely that the most \r\nprominent projected decreases in soil moisture would occur in the \r\nMediterranean, south-western USA, and southern Africa, consistent \r\nwith projected changes in the Hadley circulation and increased \r\nsurface temperatures. These AR5 conclusions are generally supported \r\nby more recent analyses of CMIP5 models (Feng and Fu, 2013; Berg \r\net al., 2017; Cook et al., 2018)."


id: e8eb3e504e97d74aeb0f720b4fef7ea6
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 38329
content:
"Although there are regions where multiple models predict consistent \r\nand significant changes in soil moisture, as with evapotranspiration \r\n(Section 8.4.1.4), there is still uncertainty in these projections related \r\nto the response of plants to elevated CO2. Most models project \r\nincreases in two variables that have opposite effects on surface \r\nwater availability: plant water use efficiency (WUE) and leaf area \r\nindex (LAI; see Section  8.4.1.4). As discussed in Sections  8.2.3.3, \r\n8.3.1.4 and 8.4.1.4, there is low confidence in how these changes in \r\nplant physiology will affect future projections of evapotranspiration, \r\nand likewise, drought and aridity."


id: 9f5e30a3e4d25a21e5e35208cfe304b9
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
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index: climate_gpt_v2
vector_id: 25260
content:
"Changes in meteorological (precipitation-based) drought duration \r\nand intensity in CMIP6 models are more robust than projected \r\nchanges in mean precipitation, more than found in CMIP5 projections \r\n(Ukkola et al., 2020). Significant increases in drought duration are \r\nexpected in Central America, the Amazonian basin, south-western \r\nSouth America, the Mediterranean, westernmost North Africa, "


id: bd88969b585bf52f16767986dd869f3b
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 30605
content:
"Results from the latest generation of models in CMIP6 are largely \r\ncongruent with CMIP5. Consistent with the coherent nature of \r\nwarming in future projections, increases in vapour pressure deficit \r\nand evaporative demand are widespread and consistent across \r\nregions, seasons, and models, increasing in magnitude in accordance "


id: a8f2086951298813a8b46bd8a4ed0c2
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 26933
content:
"Africa, south-western South America, south-western North America, \r\nsouth-western Australia, Central America and the Amazonian basin."


id: acc9cd7216bb2df4810d0b343da5b4f3
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 27642
content:
"Mediterranean, southern Africa, south-western North America, south\u0002western South America, and south-western Australia, as well as in \r\nCentral America and the Amazonian basin. In general, these regions \r\nare expected to become drier both due to reduced precipitation \r\n(medium confidence) and increases in evaporative demand (high \r\nconfidence). These same regions are likely to experience increases in \r\ndrought duration and/or severity (high confidence). The magnitude of \r\nexpected change scales with emissions scenarios (high confidence) \r\nbut even under low-emissions trajectories, large changes in \r\ndrought and aridity are expected to occur (high confidence) with \r\nconsequences for regional water availability. In the Mediterranean, \r\nCentral Chile, and western North America, future aridification will \r\nfar exceed the magnitude of change seen over the last millennium \r\n(high confidence)."


id: faa095ac31152c05e78fe4e5e674e9c5
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 41467
content:
"century in the high-emissions scenario. Globally, peak runoff of 2.5 to \r\n3 mm yr-1 sea level equivalent occurs around 2090 (Marzeion et al., \r\n2020). Regional projections are presented in detail in Section 9.5.1 \r\nand Figure 9.21, and briefly summarized below."


id: 1595fc19211916859da796849751f7e4
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 1011
content:
"Himalaya and Central Asia: Glaciers in the Himalayas feed ten of the \r\nworld's most important river systems and are critical water sources \r\nfor nearly two billion people (Wester et al., 2019). However, they are \r\nsome of the most vulnerable 'water towers' (Immerzeel et al., 2020) \r\nthat are projected to experience volume losses of approximately 30 \r\nto 100% by 2100 depending on global emissions scenarios (Marzeion \r\net al., 2020). Under mid-range emissions scenarios glaciers in this \r\nregion are projected to reach peak runoff during the period 2020 to \r\n2040 (Marzeion et al., 2020)."


id: d7972203d20a4216840363f7520c2d6e
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 35237
content:
"Alaska, Yukon, British Columbia: Post-AR5 but pre-SROCC \r\nprojections indicated a  potential 70 +-  10% reduced volume of \r\nglacier ice in western Canada relative to 2005 (Clarke et al., 2015), \r\nwith few glaciers remaining in the Interior and Rockies regions \r\nand maritime glaciers in north-western British Columbia surviving \r\nonly in a diminished state. Recent global projections support these \r\nearlier findings, showing that glacier mass in western Canada and \r\nthe USA may reduce by 50% under low-emissions scenarios and \r\nbe completely lost under the highest emissions and most sensitive \r\nglacier model combinations (Figure  9.21; Marzeion et al., 2020). \r\nArctic Canada and Alaskan glaciers are projected to experience more \r\nmodest mass loss (0-60% depending on region, scenario, and model;\r\nMarzeion et al., 2020)."


id: cc1faf290895da9557029ff09fbe78ff
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 33229
content:
"Previous assessments have concluded that recent warming has led to \r\na reduction in low-elevation snow cover (high confidence) (SROCC), \r\npermafrost (high confidence) (SROCC), and glacier mass (high to \r\nvery high confidence) (AR5; SROCC). The SROCC noted that these \r\ndeclines are projected to continue almost everywhere over the 21st \r\ncentury (high confidence), with complete glacier loss expected in \r\nregions with only small glaciers (very high confidence). The SROCC \r\nsupported the AR5 finding that glacier recession would continue \r\neven without further changes in climate. The SROCC concluded that \r\ncryosphere changes had already altered the seasonal timing and \r\nvolume of runoff (very high confidence), which in turn had affected \r\nwater resources and agriculture (medium confidence), and projected \r\npeak water runoff had already been reached before 2019 in some of \r\nthe glacier regions considered. "


id: 71d5e468b8f96502837680c162bd32b5
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 17269
content:
"Andes: Huss and Hock (2018) concluded that peak glacier mass was \r\nreached prior to 2019 for 82-95% of the glacier area in the tropical \r\nAndes. This is consistent with more recent global model simulations \r\nthat show mass loss rates from low latitude glaciers that universally \r\ndecline from the start of simulations in 2015, regardless of emissions \r\nscenario (Marzeion et al., 2020). Peak runoff in low-latitude Andean \r\nglacier-fed rivers has therefore already passed (Frans et al., 2015; Polk \r\net al., 2017) but in the Southern Andes may occur in the latter half of \r\nthe century under high-emissions scenarios (Marzeion et al., 2020)."


id: f4fa9cbc2b792f4525a0477f6fc66825
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 40463
content:
"Chapter  9  provides detailed assessment of glacier observations \r\nand projections (Figures  9.20 and 9.21, and Section  9.5.1). Here, \r\na  summary of their key findings is presented. Since SROCC, the \r\ncoordinated Glacier Model Intercomparison Project (GlacierMIP; \r\nBox  9.3; Marzeion et al., 2020) has advanced modelling efforts. \r\nGlobal glacier volumes will substantially decline in coming decades \r\nregardless of emissions scenario; under a  high-emissions scenario \r\nsome areas will lose nearly all of their glacier mass (Section 9.5.1.3). \r\nThe projected global glacier mass loss over 2015-2100 is 29,000 \r\n+-  20,000 Gt for SSP1-2.6 to 58,000 +-  30,000 Gt for SSP5-8.5 \r\n(Section 9.5.1). Because of their lagged response to warming, glaciers \r\nwill continue to lose mass for decades even if global temperature is \r\nstabilized (very high confidence) (Section 9.5.1)."


id: 8f13728ba86d85faff0e7af4bc84d5e4
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 22373
content:
"In summary, glaciers are projected to continue to lose mass under all \r\nemissions scenarios (very high confidence). Runoff from glaciers is \r\nprojected to peak at different times in different places, with maximum \r\nrates of glacier mass loss in low latitude regions taking place in the \r\nnext few decades in all scenarios (high confidence). While runoff from \r\nsmall glaciers will typically decrease because of glacier mass depletion, \r\nrunoff from larger glaciers will increase with increasing global warming \r\nuntil glacier mass is similarly depleted, after which runoff peaks and \r\nthen declines and which tends to occurs later in basins with larger \r\nglaciers and higher ice-cover fractions (high confidence). Glaciers in \r\nthe Arctic and Antarctic will continue to lose mass through the latter \r\nhalf of the century and beyond (high confidence)."


id: 7ff8b7a3347e72cd581719441f2cacb
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 19651
content:
"Global glacier mass loss projections show a  scenario-dependent \r\ngeographic partitioning of when peak in runoff occurs (Marzeion \r\net al., 2020), consistent with previous studies (Radic et al., 2014; Huss \r\nand Hock, 2018; Hock et al., 2019b). Under a low-emissions scenario \r\n(Marzeion et al., 2020) all regions exhibit runoff in the decades \r\nprior to 2050. Under a high-emissions scenario however, low- and \r\nmid-latitude regions show peak runoff before approximately 2060, \r\nwhereas Arctic regions peak in later decades around 2070-2090. \r\nAntarctic glacier losses will not have peaked by the end of the "


id: 29590b40ec716535c96e159c681d0da2
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 4491
content:
"et al., 2017; Magnin et al., 2020) no clear projections are currently \r\navailable (see discussion in Chapter 9). Projections of lake level means \r\nand variability show substantial changes for individual lakes (Bucak \r\net al., 2017; Li et al., 2021) but can be sensitive to methodology, due \r\nto the competing processes involved (Notaro et al., 2015). Projected \r\nchanges to wetlands and lakes due to climate change will occur in \r\nthe context of widespread and continuing human-caused conversion \r\nand degradation of wetlands (e.g, Davidson, 2014), and where water \r\nwithdrawals have a large impact on lake levels (e.g., Micklin, 2016)."


id: 5509ac8b7a47e26c1d861b123dc1ed49
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 12233
content:
"The AR5 assessed as very likely that the amount and seasonal \r\nduration of Northern Hemisphere (NH) snow cover will reduce under \r\nglobal warming (AR5 Sections 11.3.4.2 and 12.4.6.2). Changes in the \r\ntotal amount of water in the snow cover (snow water equivalent) \r\nare less certain because of the competing influences of temperature \r\nand precipitation."


id: c30381a983b1394bc0fd54518e98f089
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 31583
content:
"As snow cover is assessed in Chapter  9  (Section  9.5.3.3), only an \r\noverview of that assessment is provided here. Changes in seasonality \r\nof snow cover are assessed in Box  8.2. The continued consistency \r\nof reported results across all generations of model projections, \r\nalong with improvements in process understanding, has increased \r\nconfidence in snow cover projections since AR5. "


id: 902f1eee02be5894ef22d4972d0cc73d
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
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index: climate_gpt_v2
vector_id: 22573
content:
"In summary, there is medium confidence that inland wetland extent \r\nwill decrease in regions of projected precipitation decrease and \r\nevaporation increase, and high confidence that sea level rise will \r\nincrease saltwater intrusion into coastal wetlands. However, there \r\nis low agreement on the influence of sea level rise on the extent \r\nof coastal wetlands. Regarding lakes, there is high confidence for \r\ntemperature increases and ice decreases, based on both projections \r\nand physical expectations, and low confidence for non-homogeneous \r\ndecreases in mixing, given there is currently limited evidence."


id: d190562b775f5890f8452b1fdb891c16
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 34219
content:
"In summary, based on the results of Chapter  9, it is now virtually \r\ncertain that future NH snow cover extent and duration will continue \r\nto decrease with global warming. While most studies have focused \r\non the NH, process understanding suggests with high confidence that \r\nthese results apply to the Southern Hemisphere (SH) as well. There is \r\nhigh confidence in snowmelt occurring earlier in the year. Changes \r\nto the timing and amount of snowmelt will have a strong influence \r\non all the other aspects of the water cycle in regions with seasonal \r\nsnow, including run-off, soil moisture, and evapotranspiration."


id: 6116c1851dbf445fb65956127db9e716
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 14373
content:
"The AR5 did not include specific projections for wetlands and lakes. \r\nThe SRCCL and SROCC provided some discussion of wetlands \r\nprojections. For coastal wetlands, SRCCL noted the importance of sea \r\nlevel rise for increased saltwater intrusion, although projections of \r\ncoastal wetland area with sea level rise are inconclusive. Some studies \r\nproject substantial decreases (Spencer et al., 2016) while others \r\nindicate possible increases (Schuerch et al., 2018). SRCCL also noted \r\nthe general expectation for decreases in water resources, including \r\nwetlands, in areas of decreased rainfall due to increased evaporation."


id: e07ada7f33910424b48f1f8b4c5074a9
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 36747
content:
"Local studies of inland wetlands project decreases in a  range of \r\nenvironments including mountain (Lee et al., 2015), mid- to high \r\nlatitude (D. Zhao et al., 2018), and prairie (Sofaer et al., 2016) regions. \r\nIn addition to affecting wetland extent and density, changes in \r\nflooding can also affect the connectivity between wetlands and rivers \r\n(Karim et al., 2016). Despite a number of uncertainties underlying the \r\ngeneral response of wetlands to climate change, there are multiple \r\nways climate change may cause considerable stress on both inland \r\nand coastal wetlands (Junk et al., 2013; Moomaw et al., 2018)."


id: ace502a45b1d6f1a973d4f3285bea577
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 27662
content:
"Globally, two modelling studies have shown substantial decreases in \r\ngroundwater in regions including the Mediterranean, north-eastern \r\nBrazil and south-western Africa, with less clarity for other regions \r\n(Doll, 2009; Portmann et al., 2013). Recent regional-scale analyses \r\nof the impact of water cycle changes on groundwater recharge \r\n(e.g., Meixner et al., 2016; Tillman et al., 2017; Shrestha et al., 2018) \r\nsuggest changes in both seasonality and spatial distribution, which are \r\namplified under a higher greenhouse-gas emissions scenario (i.e., RCP \r\n8.5 compared to RCP4.5). Seasonality changes are linked to increases \r\nduring wet winter periods and declines during dry summer periods. "


id: fbf6eb501f3574c23143a0df8e44deff
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 41690
content:
"Widespread changes are also projected for lakes (Woolway et al., \r\n2020), including changes in lake temperature (Fang and Stefan, 1999; \r\nSahoo et al., 2016), ice (Sharma et al., 2019), evaporation (W. Wang \r\net al., 2018), and stability and mixing (Woolway and Merchant, \r\n2019). Note that lake ice is also considered in Chapter  12 of this \r\nReport. To date, CO2-induced lake acidification, analogous to ocean \r\nacidification, has not been the focus of many studies but may occur \r\nwith continued emissions (Phillips et al., 2015). While glacier lakes in \r\ngeneral increase with melting glaciers (Linsbauer et al., 2016; Colonia "


id: 139c84438b7c8eb34528748a4dc0223c
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 666
content:
"2010), the direct CO2 effect (Biasutti, 2013) and land-atmosphere \r\ninteractions (Chadwick et al., 2017; Kooperman et al., 2018) influence \r\nprojections. CMIP6 models project a clear northward ITCZ shift over \r\neastern Africa and the Indian Ocean as well as a  southward shift \r\nover the eastern Pacific and Atlantic oceans, as a result of regionally\u0002contrasting inter-hemispheric energy flows (Mamalakis et al., 2021). \r\nThe northward movement of the ITCZ over Africa has been linked to an \r\nintensification of the Saharan heat low associated with greenhouse \r\ngas (GHG) warming (Dong and Sutton, 2015), causing the tropical \r\nrain belt to seasonally migrate farther northward and reside there \r\nlonger (Cook and Vizy, 2012; Dunning et al., 2018). In southern Africa, \r\nthe projected delay in the wet season onset (Dunning et al., 2018)\r\nis also associated with a  circulation-based northward shift in the \r\ntropical rain band (Lazenby et al., 2018). "


id: c85cea4269fefb054de3900b65c188c4
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 32556
content:
"Changes in spatial distribution are linked with increases in more humid \r\nregions and declines in more arid locations. Uncertainty in projections \r\nof groundwater were found to be substantially influenced by the \r\nconceptual and numerical models employed to estimate groundwater \r\nrecharge (Meixner et al., 2016; Hartmann et al., 2017). Accordingly, \r\ncurrent research on estimating water cycles change on groundwater \r\nincludes a  focus on improving the numerical representation of \r\ngroundwater systems (Bierkens et al., 2015; Doll et al., 2016). "


id: 2d50b32b343fd5f441c311675795042d
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 5257
content:
"In summary, based on known limitations in current modelling, no \r\nconfident assessment of groundwater projections is made here, \r\nalthough important climate-related changes in groundwater \r\nrecharge are expected. In many environments, such climate-related \r\nimpacts are expected to occur in the context of substantial human \r\ngroundwater withdrawals depleting groundwater storage."


id: e26a3d65ea7ca14f302ec4a80b27c587
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 37128
content:
"In summary, consistent with the AR5, the overall weakening of the \r\ntropical circulation is projected in CMIP5 and CMIP6 simulations \r\nwith high confidence. It is likely that the zonal mean of the ITCZ \r\nwill narrow and strengthen in the core region with projected surface \r\nwarming (high confidence). Distinct regional shifts in the ITCZ will \r\nbe associated with regional changes in precipitation amount and \r\nseasonality (medium confidence)."


id: f3a319047e1a8b2f875ce31504b7abd4
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 40237
content:
"A weakening of the tropical circulation represents a balance between \r\nthermodynamic increases in low level water vapour (about 7% degC-1) \r\nand smaller increases in global precipitation (1-3% degC-1) that are \r\ninfluenced by rapid adjustments to radiative forcings as well as slow \r\nresponses to warming (Section 8.2.2.2; Bony et al., 2013; Chadwick \r\net al., 2013; Ma et al., 2018). Since AR5, additional drivers of tropical \r\ncirculation weakening have been identified, including mean SST \r\nwarming and changes in spatial patterns of SST (He and Soden, \r\n2015), and the direct CO2 radiative effect (Bony et al., 2013; He and \r\nSoden, 2015; Merlis, 2015). "


id: 8f63e250e79f27ecbd0e83e566f7dc60
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 22438
content:
"The AR5 found that the Hadley cells are likely to slow down and \r\nexpand in response to radiative forcing, but with considerable \r\ninternal variability. Given the complexities in forcing mechanisms, \r\nAR5 assigned low confidence to near-term changes in the structure \r\nof the Hadley circulation. The widening Hadley cells were expected to \r\nresult in a poleward expansion of subtropical dry zones."


id: 5b90056f6dff7263fa3c4eda9ac80a10
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updated_at: 2023-04-19 13:21:38
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vector_id: 13354
content:
"Model simulations since AR5 project a more noticeable and consistent \r\nweakening of the Northern Hemisphere (NH) winter Hadley cell than \r\nthe Southern Hemisphere (SH) winter cell (Seo et al., 2014; Zhou \r\net al., 2016), related to changes in meridional temperature gradient, \r\nstatic stability, and tropopause height (Seo et al., 2014; D'Agostino \r\net al., 2017). Changes in SST patterns reduces the magnitude of \r\nHadley cell weakening (Gastineau et al., 2009; Ma et al., 2012). There \r\nis considerable structure in Hadley circulation strength changes \r\nwith longitude, associated with cloud-circulation interactions \r\n(Su et al., 2014). Subtropical anticyclones are projected to intensify \r\nover the north Atlantic and south Pacific but to weaken elsewhere \r\n(He et al., 2017)."


id: dcc3c6510b26c29a56ccf8c898de17f
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 36104
content:
"A consistent poleward expansion of the edges of the Hadley cells is \r\nprojected (Nguyen et al., 2015; Grise and Davis, 2020), particularly in the \r\nSH, consistent with observed trends (Figure 8.21 and Section 8.3.2.2; \r\nNguyen et al., 2015). The main driver of future expansion appears to \r\nbe greenhouse gas forcing (Grise et al., 2019), with uncertainty in \r\nmagnitude due to internal variability (Kang et al., 2013). Proposed \r\nmechanisms for poleward expansion include increased dry static \r\nstability (Frierson et al., 2007; Lu et al., 2007), increased tropopause \r\nheight (Chen and Held, 2007; Chen et al., 2008), stratospheric \r\ninfluences (Kidston et al., 2015) and radiative effects of clouds and \r\nwater vapour (Shaw and Voigt, 2016; see also Section 4.5.1.5). Hadley \r\ncell expansion is thought to be associated with the precipitation "


id: 505d538a58d70abe63a037d3dc671d78
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 11419
content:
"Regional shifts in tropical convergence zones are much larger than \r\ntheir zonal mean, and associated regional changes in precipitation \r\n(Chadwick et al., 2013; Mamalakis et al., 2021) are characterized by \r\nconsiderable uncertainties across models (Kent et al., 2015; Oueslati \r\net al., 2016). Over the tropical oceans, shifts in rain bands are strongly \r\ncoupled with changes in SSTs (Xie et al., 2010; Huang et al., 2013). \r\nOver tropical land, factors including remote SST increases (Giannini, "


id: 4696ae68271818a6b43b5bbbf8e81cbe
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 9624
content:
"declines projected in many subtropical regions (Shaw and Voigt, \r\n2016), but more recent work suggests that these reductions are \r\nmainly due to the direct radiative effect of CO2 forcing  (He and \r\nSoden, 2015), land-sea contrasts in the response to forcing \r\n(Shaw and Voigt, 2016; Brogli et al., 2019) and SST changes (Sniderman \r\net al., 2019). In semi-arid, winter rainfall-dominated regions (such \r\nas the Mediterranean), thermodynamic processes associated with \r\nthe land-sea thermal contrast and lapse rate changes dominate the \r\nprojected precipitation decline in summer, whereas circulation \r\nchanges are of greater importance in winter (Brogli et al., 2019). \r\nThe hydroclimates in these regions are projected to evolve with time \r\ndue to changing contributions from rapid atmospheric circulation \r\nchanges and their associated SST responses, as well as slower SST \r\nresponses to anthropogenic forcing (Zappa et al., 2020). "


id: 6e86489c3b4eccd28f96ed9908bb2b75
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 16709
content:
"responses to global warming have been highlighted by numerical \r\nexperiments with both comprehensive and simplified models. Results \r\nsuggest a transient strengthening of the Walker circulation related to \r\nIndian Ocean warming (L. Zhang et al., 2018), followed by a slower \r\nweakening linked to a  strengthened eastern Pacific cold tongue \r\nwarming emerging after 50-100 years (Section  7.4.4.2.1; Heede \r\net al., 2020)."


id: 530f32ac778405b99e87863dc384169c
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 11881
content:
"CMIP6 projections provide further evidence of a  significant long\u0002term weakening of the Walker circulation (Figure 8.21). For instance, \r\na  pronounced weakening of the upper-level tropical easterly jet is \r\nprojected both over the Indian Ocean and tropical eastern Pacific, \r\nwhere declines are projected to exceed 70% by 2100 in the high\u0002emissions SSP5-8.5 scenario (S. Huang et al., 2020). CMIP6 models \r\nagree on a  future decrease of the equatorial zonal temperature \r\ngradient (Fredriksen et al., 2020), which can lead to weaker trade \r\nwinds over the tropical Pacific. However, CMIP6 models show \r\na  diversity of SST warming patterns in the tropical Pacific (Freund \r\net al., 2020), which contributes to uncertainties in the response of \r\nboth Walker circulation and ENSO to continued warming. "


id: e5ffec11c7d1c92e9f40acedc515a427
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 37759
content:
"In summary, CMIP5 and CMIP6 models project a weakening of the \r\nHadley cells, with high confidence for the NH in boreal winter and \r\nlow confidence for the SH in austral winter. The Hadley cells are \r\nprojected to expand polewards with global warming, most notably \r\nin the SH (high confidence). There is currently low confidence in the \r\nimpacts on regional precipitation in subtropical regions. "


id: bae2d261e45ee09715052b23276867a3
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 30096
content:
"In summary, there is high confidence that the Pacific Walker circulation \r\nwill weaken by the end of the 21st century, and will be associated \r\nwith decreased precipitation over the western tropical Pacific \r\nand increases farther east. Discrepancies between observed and \r\nsimulated changes in SSTs in the tropics indicate that a temporary \r\nstrengthening of the Walker Circulation can arise from a  transient \r\nresponse to GHG radiative forcing (low confidence) and from internal \r\nvariability (medium confidence)."


id: c6213bb3c333bc4958b20356a975e77b
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 32167
content:
"The AR5 determined that the Pacific Walker circulation was likely to \r\nslow down over the 21st century, which would lead to decreased \r\nprecipitation over the western tropical Pacific and increases over the \r\ncentral and eastern Pacific. Recent studies show consistency with \r\nAR5 conclusions but also show an eastward shift over the Pacific, \r\nmostly due to a shift towards more 'El Nino-like' conditions under \r\nglobal warming (Bayr et al., 2014). Other studies suggest that the \r\nweakening of the Walker circulation is related to the response \r\nof the western North Pacific monsoon and to changing land-sea \r\ntemperature contrasts, while a positive ocean-atmosphere feedback \r\namplifies the weakening of both east-west SST gradient and trade \r\nwinds in the tropical Pacific (Zhang and Li, 2017)."


id: df5a175ae1fb69b11c9de7459e23ce91
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 36540
content:
"Regions: Regional storm tracks \r\nmoving polewards at different rates in \r\ndifferent basins. Southern \r\nhemisphere storm tracks have moved \r\npolewards more clearly, partly driven \r\nby ozone depletion. Poleward \r\nmovement likely to weaken as ozone \r\nhole recovers."


id: 5aa446bd09981dff81a5748c9619e07
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 13204
content:
"Figure 8.21 | Schematic depicting large-scale circulation changes and impacts on the regional water cycle. The central figures show precipitation minus \r\nevaporation (P-E) changes at 3degC or global warming relative to an 1850-1900 base period (mean of 23 CMIP6 SSP5-8.5 simulations). Annual mean changes (large map) \r\ninclude contours (ocean only) depicting control climate P-E = 0 mm day-1 lines with the solid contour enclosing the tropical rain belt region and dashed lines representing the \r\nedges of subtropical regions. Confidence levels assess understanding of how large-scale circulation change affect the regional water."


id: 25cb74b74dbe2fdb328ed9d7a993d7bc
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 3831
content:
"In AR5, monsoon precipitation over land was projected to intensify \r\nby the end of the 21st century, due to thermodynamic increases in \r\nmoisture convergence despite weakening of the tropical circulation \r\n(see Section 8.2.1.3). Following the definition of regional monsoons \r\nin Annex V  and Figure  8.11, and the assessment of the observed \r\nchanges (Section  8.3.2.4), here we provide an assessment of \r\nprojected changes in regional monsoons. Assessment is provided \r\neither in terms of SSP and RCP scenarios and global warming levels \r\navailable since AR5, or from the newly available CMIP6 projections \r\n(Figure  8.22 and Table  8.2). Table  8.2 provides projected changes \r\nacross the five SSPs used in this Report for precipitation (mm day-1), \r\nP-E (mm day-1) and runoff (mm day-1) over the regional monsoons \r\nfor the mid (2041-2060) and long term (2081-2100). "


id: d63eb13758b12db76f829fe41fbbbb75
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 35009
content:
"In AR5, South and South East Asian monsoon (SAsiaM) precipitation \r\nwas projected to increase by the end of the 21st century but with \r\na  weakening of the circulation, with high agreement across the \r\nCMIP5 models (Kitoh et al., 2013; Menon et al., 2013; Sharmila et al., \r\n2015; Sooraj et al., 2015; Kitoh, 2017; Kulkarni et al., 2020). Since \r\nAR5, most studies have confirmed projected increases in South Asian \r\nmonsoon precipitation (high confidence), while one high-resolution \r\nmodel (35 km in latitude/longitude) projects monsoon precipitation \r\ndecreases during the 21st century following the RCP4.5 scenario \r\n(Krishnan et al., 2016)."


id: 296caf2e4f5e51c4400a8386a8d681e3
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 4508
content:
"Future monsoon projections from CMIP6 models show an increase \r\nof SAsiaM precipitation across all the scenarios and across all the \r\ntime frames (Figure 8.22) with the maximum increase at the end of \r\nthe 21st century in SSP5-8.5 (Almazroui et al., 2020c; Z. Chen et al., \r\n2020b; Ha et al., 2020; Wang et al., 2021). Table 8.2 confirms that \r\nchanges in runoff and P-E over SAsiaM region are positive and largest \r\nin the higher emissions scenarios considered, as in precipitation. On \r\nthe other hand, changes in the ensemble mean for all the variables \r\nconsidered in the SSP1-1.9 scenario are negative for both mid and \r\nlong-term periods (Table  8.2). This is also consistently reflected \r\nin the spatial map of future precipitation changes (Figure  8.15). \r\nDifferent near-term projections of the SAsiaM may result given the "


id: ec03c1875bf37306c0f3aeea8f482b1c
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 38891
content:
"Figure 8.22 | Projected regional monsoons precipitation changes. Percentage change in projected seasonal mean precipitation over regional monsoon domains (as \r\ndefined in Figure 8.11, Section 8.3.2.4 and Annex V) for near term (2021-2040), mid-term (2041-2060), and long term (2081-2100) periods based on 24 CMIP6 models and \r\nthree SSP scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5). Further details on data sources and processing are available in the chapter data table (Table 8.SM.1)."


id: b46546ce78a2ae17faf6d20dc849027f
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 28973
content:
"diversity in the future aerosol emissions pathways and policies for \r\nregulating air pollution (Wilcox et al., 2020). Additionally, near-term \r\nprojections of SAsiaM precipitation are expected to be constrained \r\nby internal variability associated with the PDV (X.  Huang et al., \r\n2020a). CMIP6 models also indicate a lengthening of the summer \r\nmonsoon over India by the end of the 21st century, at least in \r\nSSP2-4.5, with considerable inter-model spread in the projected late \r\nretreat (Ha et al., 2020)."


id: 661c312799567dd402c39c65b7dcadff
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 15227
content:
"intensify the EAsiaM circulation during the 21st century. However, \r\nthere are large uncertainties in projected water cycle changes over \r\nthe region (Endo et al., 2018), mostly in the near-term because of \r\nuncertainties in future aerosol emissions scenarios (Wilcox et al., \r\n2020), as well as due to the interplay between internal variability \r\nand anthropogenic external forcing (Wang et al., 2021)."


id: 2669e961593f2d467c34712761dce8a7
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 3928
content:
"In summary, consistent with AR5, there is high confidence that \r\nSAsiaM precipitation is projected to increase during the 21st century \r\nin response to continued global warming across the CMIP6 higher \r\nemissions scenarios, mostly in the mid- and long terms. "


id: 4f227e8e86738976c60977647647f9be
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 11208
content:
"In AR5, the East Asian monsoon (EAsiaM) was projected to intensify \r\nin terms of precipitation, with an earlier onset and longer duration \r\nof the summer season. Since AR5, there has been improved \r\nunderstanding of future projected changes in the EAsiaM. "


id: 1863e38d036cdbfffaf3bd1cf747944c
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 1502
content:
"In summary, despite the uncertainties in the monsoon circulation \r\nresponse in CMIP5 and CMIP6 models, there is high confidence that \r\nsummer monsoon precipitation over East Asia will increase in the \r\n21st century and medium confidence that the monsoon season will \r\nbe longer."


id: 7fac8e032bf957fdd80ac5933af713ca
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 19598
content:
"The AR5 concluded that projections of West African monsoon \r\n(WAfriM) rainfall are highly uncertain in CMIP3 and CMIP5 models, \r\nbut still suggest a small delay and intensification in late wet season \r\nrains. Studies published since AR5 are broadly consistent with this \r\nassessment. CMIP6 models agree on statistically significant projected "


id: 1fe47cdcafe449c29d4b7a3f1bc05415
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 2822
content:
"Changes in seasonality (Box 8.2) are projected with a later monsoon \r\nonset (high confidence) over the Sahel and a late cessation (medium \r\nconfidence), suggesting a  delayed wet season as a  regional \r\nresponse to global GHG forcing (Biasutti, 2013; Dunning et al., 2018; \r\nAkinsanola and Zhou, 2019). Rainfall distribution is projected to be \r\nhighly variable with a decrease in the number of rainy days in the \r\nwestern Sahel, consistent with an increase in consecutive dry days \r\nand a reduction in the number of growing season days (Cook and \r\nVizy, 2012; Diallo et al., 2016). A decrease in the frequency but an \r\nincrease in the intensity of very wet events is projected to be more \r\npronounced over the Sahel than over Guinean coast, and also under \r\nhigher emissions scenarios (i.e., RCP8.5; Sylla et al., 2015; Akinsanola \r\net al., 2018)."


id: 43592129a28834601eee8a626d72b3e7
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 9064
content:
"In summary, there is low agreement on a  projected decrease of \r\nNAmerM precipitation, however there is high confidence in delayed \r\nonsets and demises of the summer monsoon."


id: 51c98ce285f339945c66c2302a5209ac
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 11675
content:
"The AR5 reported medium confidence that the South American \r\nmonsoon (SAmerM) overall precipitation will remain unchanged, and \r\nmedium confidence in projections of extreme precipitation. The AR5 \r\nalso stated high confidence in the spatial expansion of the SAmerM, \r\nresulting from increased temperature and humidity."


id: f412c1a4ef9f0c9d1f10be7894006b75
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 40313
content:
"In summary, post-AR5 studies and newly available CMIP6 results \r\nindicate projected rainfall increases in the eastern-central WAfriM \r\nregion but decreases in the west (high confidence), with a delayed \r\nwet season (medium confidence). Overall, WAfriM summer \r\nprecipitation is projected to increase during the 21st century but \r\nwith larger uncertainty noted under high-emissions scenarios \r\n(medium confidence)."


id: 8e371494e86be7c04faa7151cd40c7a1
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 22212
content:
"The AR5 concluded that the North American monsoon (NAmerM) \r\nwill likely intensify in the future, even though there is low agreement\r\namong models. The AR5 reported medium confidence that \r\nprecipitation associated with the NAmerM will arrive later in the \r\nannual cycle and persist longer."


id: 757c9f2d5b5d2281bc1d0606d820800f
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 17897
content:
"Since AR5, analyses of CMIP5 projections suggest little change in the \r\noverall amount of NAmerM precipitation in response to rising global \r\nsurface temperature. However, significant declines are projected in \r\nthe early monsoon season and increases in the late monsoon season, \r\nsuggesting a shift in seasonality toward a delayed monsoon onset "


id: 941e5a387510d91f7af7ead16eb90d48
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 23266
content:
"warming in the NH than SH, favouring a  northward shift of the \r\ntropical rain belt (e.g., Rotstayn et al., 2015). "


id: 8ba21216100a11525d04f128b4ff9ce1
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 21736
content:
"There are some clear projected changes in the rainfall variability \r\nand extremes of the Australian monsoon. Rainfall variability in the \r\nAustralian monsoon domain increases on time scales from daily to \r\ndecadal in CMIP5 models (Brown et al., 2017), indicating either more \r\nintense wet days or more dry days or both. There is also a projected \r\nincrease in the intensity of extreme rainfall but a reduction in the \r\nfrequency of heavy rainfall days for the Australian monsoon (Dey \r\net al., 2019a). This is consistent with Moise et al. (2020), who found \r\nan increase in Australian monsoon active phase or 'burst' rainfall \r\nintensity but a reduction in the number of burst days and events."


id: 7e976253dd273e25102266613f9922bc
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 19425
content:
"H.  Zhang et al. (2013) examined changes in Australian monsoon \r\nonset and duration in CMIP3 models and found model agreement \r\non a delay in onset and shortened duration to the north of Australia, \r\nbut less agreement over the interior of the continent. An updated \r\nstudy of CMIP5 models found similar mean changes with delayed \r\nonset and shortened duration, but substantial model disagreement \r\n(H. Zhang et al., 2016). "


id: 5384851c814bb9bd4607bddf02b2d2f0
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 11968
content:
"In summary, there is high confidence that the SAmerM will experience \r\ndelayed onsets in association with increases in GHG.  However, \r\nthere is low agreement on the projected changes in terms of total \r\nprecipitation of the South American summer monsoon season. "


id: cbf6a4b679adf8442428d5382c7ddd37
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 33211
content:
"In summary, CMIP6 projections show an increase of AusMCM \r\nprecipitation across all emissions scenarios. There is strong model \r\nagreement on an increase in monsoon precipitation over the \r\nMaritime Continent while there is low agreement on the direction \r\nof change over northern Australia. There is a projected increase in \r\nrainfall variability over northern Australia, with increased intensity of \r\nrainfall during the active or 'burst' phase (medium confidence). "


id: ee4f74ac6024f0a46c9a882dee0b5a83
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 39298
content:
"The AR5 concluded that projected changes in Australian and Maritime \r\nContinent monsoon (AusMCM) rainfall and seasonality are uncertain \r\nin the CMIP5 models, with some projecting increases and others \r\nprojecting decreases for the range of emissions scenarios. Models \r\nthat perform better at simulating present day regional climate project \r\nlittle change or an increase in Australian monsoon rainfall (Jourdain \r\net al., 2013; CSIRO and BoM, 2015; Brown et al., 2016b). CMIP6 \r\nmodels project increased AusMCM precipitation in the 21st century \r\nbut with a more robust signal in SSP2-4.5 and SSP5-8.5 rather than \r\nin lower emissions scenarios (Figure 8.22). A reduced range of CMIP6 \r\nrainfall projections but continued disagreement on the sign of change \r\nis reported over Australia (Narsey et al., 2020)."


id: d7ba8e14276eb9893fd1868e16ddc38b
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 35262
content:
"Tropical cyclones (TCs) projections are primarily assessed in \r\nSection  11.7.1.5. Here, we extend this analysis by assessing the \r\nimplications of projected changes in tropical cyclones on the water cycle."


id: edc248b71e572a8e8ada63a572f4cd0e
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 39186
content:
"The AR5 concluded that TC rainfall rate was likely to increase \r\nthrough the 21st century. Section 11.7.1.5 assesses that the average \r\ntropical cyclone rain-rate is projected to increase with warming (high \r\nconfidence), and peak rain rates are projected to increase at greater \r\nthan the Clausius-Clapeyron scaling rate of 7% degC-1 warming in \r\nsome regions due to increased low-level moisture convergence \r\n(medium confidence). The increase in TC rainfall rate is explained by \r\nincreased TC intensity resulting from increasing SSTs, and increased \r\nenvironmental water vapour (Chauvin et al., 2017; M. Liu et al., 2019)."


id: 5a851f08c275726a12ccf8807ddf2504
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 13180
content:
"The northern and eastern parts of the Maritime Continent have \r\nprojected increases in rainfall in CMIP5 models (Siew et al., 2014), \r\nwhile there are projected decreases over Java, Sulawesi and southern \r\nparts of Borneo and Sumatra. Rainfall changes are correlated with \r\nthe extent of warming in the western tropical Pacific in CMIP5 \r\nmodels (Brown et al., 2016b) but inter-model differences are also \r\nrelated to modelled large-scale zonal mean precipitation response \r\nin both CMIP5 and CMIP6 model ensembles (Narsey et al., 2020). \r\nDecomposition of projected rainfall changes indicates that the\r\nlargest source of model uncertainty is associated with shifts in \r\nthe spatial pattern of convection (Chadwick et al., 2013; Brown et al., \r\n2016b). Uncertainties in capturing the spatial and temporal features \r\nof the Maritime Continent monsoon depend also on the horizontal \r\nresolution of coupled climate models (e.g., Jourdain et al., 2013)."


id: b962b2584b8a5b90c54c8013a0b82109
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 29830
content:
"Consistent with the observed poleward migration of tropical cyclone \r\nactivity (Kossin et al., 2014), in the SH a larger proportion of storms \r\nare projected to decay south of 25degS at the end of the 21st century \r\nbut with negligible changes in genesis latitude and storm duration \r\nfor the Australian region (CSIRO and BoM, 2015; Sharmila and Walsh, \r\n2018). An analysis of projections for North Pacific islands indicate \r\nthat the maximum intensity of storms will increase but the number \r\nof tropical cyclones will decrease in some places, such as Guam and \r\nKwajalein Atoll in the tropical north-western Pacific, or remain the \r\nsame in other regions like near Okinawa (Japan) or Oahu (Hawaii) \r\n(Widlansky et al., 2019). TC-induced storm tides affecting landfall in "


id: 63af17f182529ffe13c6962f61917f86
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 14828
content:
"The role of anthropogenic aerosol forcing in future projections of the \r\nAustralian monsoon has been investigated for CMIP5 models (Dey \r\net al., 2019a); decreases in anthropogenic aerosol concentrations \r\nover the 21st century are expected to produce relatively greater "


id: 7916fd658888af6e43fbefe8c01c9ba7
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 18493
content:
"the Pearl River delta over South China are projected to increase by \r\nthe end of the 21st century (J. Chen et al., 2020b)"


id: 3928c7ee7d6d5b8517ff933aa65c3eab
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 7265
content:
"In AR5, the increased ability of models to simulate blocking and \r\nhigher agreement on projections led to an assessment with medium \r\nconfidence that the frequency of NH and SH blocking will not \r\nincrease, but future changes in blocking intensity and persistence \r\nwere deemed uncertain (AR5 Chapter  14, ES and Box  14.2). \r\nBlocking influences precipitation (e.g., Trigo et al., 2004), flooding \r\n(e.g.,  Yamada et al., 2016), drought (e.g.,  Dong et al., 2018b), \r\nsnow (e.g., Garcia-Herrera and Barriopedro, 2006), and glacier melt \r\n(e.g., Hanna et al., 2013), and so is of broad importance to the water \r\ncycle in areas of blocking activity."


id: 150d7d7f6f192b1226e0a2c4716e191e
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 918
content:
"In summary, there is high confidence that heavy precipitation \r\nassociated with tropical cyclones is projected to increase, in response \r\nto well-understood processes related to increased low-level moisture \r\nconvergence and environmental water vapour. "


id: 19fcdb604c9abf45b8a86f876b764ebc
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 1771
content:
"The AR5 did not provide an assessment of stationary wave \r\nprojections as distinct from other related aspects of circulation, such \r\nas blocking, modes of variability, and storm tracks. Here we provide \r\na  brief assessment of stationary wave projections from the water \r\ncycle perspective, with the related circulation aspects considered \r\nseparately in the following sections. "


id: 9dc0327c491c93d6c89c09057789c375
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 24988
content:
"Several studies based on CMIP5 projections show changes in \r\nNH winter stationary waves that increase precipitation over the \r\nwest coast of North America and decrease it over the eastern \r\nMediterranean and parts of south-western North America (Neelin \r\net al., 2013; Seager et al., 2014a, b, 2019b; Simpson et al., 2016; \r\nWills et al., 2019), although the underlying dynamics are not yet fully \r\nunderstood (Seager et al., 2019b; Wills et al., 2019). For the NH winter \r\nglobal teleconnection pattern, the majority of the models analyzed in \r\n(Sandler and Harnik, 2020) project the development of a preferred \r\nlongitudinal phasing for the pattern, but with strong disagreement \r\namong models over the details of the phasing and therefore the \r\nassociated regional hydrologic impacts."


id: d66d0a2b987cd123f8f5ff9019f5739c
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 35028
content:
"In summary, and despite recent improvements in the simulation of \r\nblocking, there is limited evidence in model projections of future \r\nchanges, except for boreal winter over Greenland and the North \r\nPacific where there is high confidence that blocking events are not \r\nexpected to increase in the SSP3-7.0 and SSP5-8.5 scenarios. As with \r\nstationary waves, this adds uncertainty to mid-latitude water cycle \r\nprojections at the regional scale."


id: 2d5978e7ac602ec2d85dccb2b590904e
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 5265
content:
"The AR5 found that extratropical storms were expected to decrease in \r\nthe Northern Hemisphere (NH), but only by a few percent. Meanwhile, \r\nprecipitation associated with extratropical storms was projected to \r\nincrease due to thermodynamic increases in moisture but potentially \r\nalso due to intensification from increased latent heat release. Latent \r\nheating is a strong influence on extratropical storms, so it is plausible \r\nthat changes in precipitation and associated latent heating could \r\naffect extratropical storm intensity and thus precipitation (Z. Zhang \r\net al., 2019)."


id: aafb9a091d9f2ab9f6df64522963e799
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 27306
content:
"In summary, future changes in stationary waves may have an \r\nimportant influence on both the mean state and variability of the water \r\ncycle. Limitations in model representation, dynamical understanding, \r\nand the number of targeted studies on the topic currently constrain \r\nthe assessment of future changes in stationary waves. Based on \r\ncurrent knowledge, there is low confidence that projected changes in \r\nstationary wave activity will contribute to decreases of cold season \r\nprecipitation over the eastern Mediterranean and increases over the \r\nwest coast of North America."


id: 987f1378ad6f9a345f19ac8b935e233a
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 24040
content:
"There is increased evidence that precipitation associated with \r\nindividual extratropical storms is projected to increase, following \r\nthermodynamic drivers with negligible dynamic change (Yettella and \r\nKay, 2017). Comparisons with reanalyses also support the projected \r\nincrease in thermodynamic precipitation with little dynamic response "


id: f653c1e3f34e3714db3956a1463dca49
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 40705
content:
"through the greenhouse gas influence on SSTs. The importance of the \r\nstratospheric polar vortex in storm track changes has received more \r\nattention (Zappa and Shepherd, 2017; Mindlin et al., 2020) and the \r\nanticipated recovery of the ozone layer further complicates the role of \r\nthe stratosphere (Shaw et al., 2016; Bracegirdle et al., 2020b)."


id: b8ec1a509590358e886fcd345d493071
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 29742
content:
"for precipitation associated with extratropical storms (Li et al., 2014). \r\nThere is high confidence that projected increases in precipitation \r\nassociated with extratropical storms in the NH (Marciano et al., 2015; \r\nPepler et al., 2016; Michaelis et al., 2017; Yettella and Kay, 2017; \r\nZhang and Colle, 2017; Hawcroft et al., 2018; Kodama et al., 2019). \r\nA projected decrease in the number of extratropical cyclones over \r\nthe NH during the boreal summer in CMIP5 models was reported \r\nby Chang et al. (2016) who related this decrease with a decrease in \r\ncloudiness and thus accentuating increased maximum temperatures. \r\nHowever, model spread was quite large, especially over North \r\nAmerica, thus there is only low confidence in this seasonal signal."


id: 1a9237cd71150c27126b4b78add9943b
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 1876
content:
"In AR5, the Southern Hemisphere (SH) storm track was deemed likely\r\nto shift poleward, the North Pacific storm track more likely than not to \r\nshift poleward, while the North Atlantic storm track was unlikely\r\nto display any discernible changes. There was low confidence in \r\nregional storm track changes and the associated surface climate \r\nimpacts, although a  weakening of the Mediterranean storm track \r\nwas a robust response of the models. Since AR5, the SH mid-latitude \r\nstorm track is projected to shift poleward and the westerlies are \r\nprojected to strengthen over Australia (CSIRO and BoM, 2015). \r\nAlthough thermodynamic effects were considered to be the most \r\nimportant factor in overall projections of increased mid-latitude \r\nprecipitation, the general poleward shift in cyclogenesis and an \r\nenhanced latitudinal displacement of individual cyclones may play \r\na role (Tamarin-Brodsky and Kaspi, 2017)."


id: 5dca429b5fbf07391d47de7b060d26c1
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 13793
content:
"The projected changes in storm tracks and the associated mechanisms \r\nhave several important implications for water cycle projections. P-E \r\nchanges in the Mediterranean, California and Chile are directly \r\nlinked to storm track changes (Zappa et al., 2020). Where the storm \r\ntracks are robustly projected to shift (SH, North Pacific) or weaken \r\n(Mediterranean), understanding the physical causes of the related \r\nchanges in precipitation helps increase confidence in the projections. \r\nUnderstanding the competing influences provides context for why \r\nother regions do not exhibit a consistent signal and cautions against \r\nregional projections based on individual models. However, model \r\nbias and the need for relatively high resolution to reproduce the \r\nrelevant dynamics is an important overall limit on confidence in \r\ncurrent CMIP6 projections."


id: dc3ec268a9574ebff26e8e28189ff236
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 36020
content:
"In summary, there is the high confidence that precipitation associated \r\nwith extratropical storms will increase with global warming in most \r\nregions. The SH storm track will likely shift poleward, the North Pacific \r\nstorm track more likely than not will shift poleward, and the North \r\nAtlantic storm track is unlikely to have a  simple poleward shift/ \r\ndisplay any discernible changes. There is low confidence in regional \r\nstorm track changes, although a  weakening of the Mediterranean \r\nstorm track is a robust response of the models."


id: 89a86d191156151218580fede3ef1e57
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 21395
content:
"The role of temperature trends in influencing storm tracks has \r\nbeen  further investigated, both in terms of upper tropospheric \r\ntropical warming (Zappa and Shepherd, 2017) and lower \r\ntropospheric  Arctic  amplification (J.  Wang et al., 2017), including \r\nthe direct role of  Arctic sea ice loss (Zappa et al., 2018), and the \r\ncompetition between their influences (Shaw et al., 2016). Physical \r\nlinkages between Arctic amplification and changes in the mid-latitudes \r\nare uncertain, as discussed in Chapter 10 (Cross-Chapter Box 10.1). The \r\nremote and local SST influence has been further examined by Ciasto \r\net al. (2016), who confirmed sensitivity of the storm tracks to the \r\nSST trends generated by the models and suggested that the primary \r\ngreenhouse gas influence on storm track changes was indirect, acting "


id: 1b8188a9d8467f3818c7b22021524dd3
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 2026
content:
"Atmospheric rivers were not assessed in AR5 but are important in \r\nthe water cycle as they are linked to extreme rainfall, flooding, and \r\nchanges in terrestrial water storage including melt and ablation of \r\nglaciers and snowpack (Sections 8.2.3). In a warming world, there \r\nis high confidence that thermodynamical increases in atmospheric "


id: c9b77dbf6737c368360c623ba6362ac2
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 32814
content:
"water vapour ensure that atmospheric rivers will become wetter, \r\nhence stronger, and longer-lasting (Payne et al., 2020). This is \r\nclearly observed in several regional (Ralph and Dettinger, 2011; \r\nLavers et al., 2013; Gao et al., 2015; Payne and Magnusdottir, 2015; \r\nWarner et al., 2015; Hagos et al., 2016; Gershunov et al., 2019) and \r\nin one global study (V.  Espinoza et al., 2018) of atmospheric river \r\nactivity in CMIP5 model projections. Lavers et al. (2015) indicate that \r\nintegrated vapour transport under RCP 8.5 and 4.5 could increase, \r\nand consequently this thermodynamic response (O'Gorman, 2015) \r\ncould affect mid-latitude regions where orographic precipitation is \r\nimportant (Gershunov et al., 2019). "


id: 70ba6b24205a5b8c7b0bf4ffd70d73c9
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 17093
content:
"Following on from the assessment of projected changes in \r\nmodes of climate variability (MoVs) and regional teleconnections \r\n(Section  4.5.3), here we assess their consequences for projected \r\nwater cycle changes."


id: d82d8505d502eb68015399b6988d35ca
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 35333
content:
"Even over regions with statistically significant simulated rainfall \r\nteleconnections during the historical period, CMIP5 models do not \r\nproject clear changes (Perry et al., 2020). Nonetheless, CMIP5 models \r\nthat realistically reproduce Indian summer monsoon rainfall indicate \r\na strengthening of its relationship with ENSO in RCP8.5 projections, \r\nthough the response is not consistent for different varieties of ENSO \r\nevents (Roy et al., 2019). Inconsistent changes in the ENSO-Indian \r\nsummer monsoon relationship in response to global warming \r\nin CMIP5 and CMIP6 models may be related to statistical issues \r\nrather than dynamical changes (Bodai et al., 2020; Haszpra et al., \r\n2020). Over East Africa during the boreal spring and summer, ENSO \r\nteleconnections are projected to become stronger in the future \r\n(Endris et al., 2019). Meteorological drought consequences of each \r\nstrong El Nino are projected to become more severe in the region \r\n(Rifai et al., 2019)."


id: f36a42364e5c0b65fb758b10486b9df0
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 40199
content:
"In semi-arid regions where atmospheric rivers have historically been \r\nimportant and precipitation is mainly confined to the cold season, the \r\ncontribution of atmospheric rivers to annual total precipitation may \r\nbe expected to grow disproportionately. For example, in California \r\ndecreases in precipitation frequency are projected as a  result of \r\nfewer non-atmospheric river storms, while the projected increase \r\nin heavy and extreme precipitation events are almost entirely \r\na  result of increased atmospheric river activity (Gershunov et al., \r\n2019). Interannual variability in precipitation amounts is projected \r\nto increase because of the overall decrease in the frequency of \r\nstorms but a stronger dependence on extremes (Polade et al., 2014), \r\nparticularly due to atmospheric rivers (Gershunov et al., 2019), \r\nespecially where interaction with topography are important (Polade \r\net al., 2014; Gershunov et al., 2019). "


id: 9e885803d96054a7d16d6658603f36fa
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 25116
content:
"Indian Ocean Dipole (IOD, Annex IV.2.4) and Indian Ocean Basin (IOB, \r\nAnnex IV.2.4) interactions with ENSO are expected to persist in the \r\nfuture (Section 4.5.3.3) but projected changes in the frequency and \r\nintensity of events remain uncertain (Hui and Zheng, 2018; Endris \r\net al., 2019; McKenna et al., 2020). Climate extremes such as those \r\nassociated with the extreme positive IOD event of 2019 are expected \r\nto occur more frequently under continued global warming (Cai et al., \r\n2021). Projected changes in IOD teleconnections are linked to model \r\nperformance in representing the IOD and its remote influence in the \r\npresent climate, apparently dominated by a positive IOD event-like \r\nmean state (G. Wang et al., 2017; Huang et al., 2019). Interactions \r\nbetween the IOD and the Indian Ocean mean state, via atmosphere-\r\nocean feedbacks, can affect the behaviour of the IOD (Ng et al., 2018). \r\nIn the eastern Horn of Africa, OND rainfall is projected to increase "


id: 723aee4cb1f65bca6bb2648e5b6f18b6
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 17338
content:
"In summary, there is high confidence that the magnitude and \r\nduration of atmospheric rivers are projected to increase in future, \r\nleading to increased precipitation. This is projected to increase the \r\nintensity of heavy precipitation events on the west coast of the USA \r\nand in western Europe (high confidence)."


id: 6ab1c21111e5492fd6684f2d3c57e901
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 16053
content:
"because of IOD-ENSO related SST changes in the Indo-Pacific region \r\nand associated Walker circulation changes (Endris et al., 2019). "


id: 72a66c1e55e68d581486e8a21756571a
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 17412
content:
"In the SH, the positive trend projected for the SAM in the CMIP5 \r\nRCP8.5 scenario appears to mitigate the wetting in the mid- to high \r\nlatitudes and the drying over the subtropics, but with strong seasonal \r\ndependence (Lim et al., 2016). Regional precipitation changes in \r\nSouth America, South Africa, Southern Australia and New Zealand are \r\nnot well explained by changes in the SAM, but are related to broad\u0002scale changes in north-south temperature gradients associated \r\nwith enhanced warming of the tropical upper troposphere and \r\nstrengthening of the stratospheric polar vortex (Mindlin et al., 2020)."


id: a96b0012bda1b52f599ddb97f8db6ffe
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 27028
content:
"In summary, projected changes in the intensity, frequency and \r\nphase of extratropical MoVs (see also Sections  4.3 and 4.5) may \r\namplify regional changes in precipitation and contribute to an \r\nincrease in their intra-seasonal and interannual variability (medium \r\nconfidence). Regionally, there are potentially significant precipitation \r\nand atmospheric circulation changes associated with changes in \r\nextratropical dynamics (low confidence). "


id: 24270f8aa1cfa5c4fda1a8c5c27dcd54
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 3542
content:
"In summary, even though there is low confidence in how the tropical \r\nMoVs will change in the future (Sections 4.3.3.2 and 4.5.3.3), their \r\nregional hydrological consequences, in terms of precipitation, are \r\nprojected to intensify (medium confidence). For example, the ENSO \r\ninfluence on precipitation over the Indo-Pacific sector is projected \r\nto strengthen and shift eastward (medium confidence). The MJO is \r\nprojected to intensify in a warmer climate, with increased associated \r\nprecipitation (medium confidence)."


id: 4c247773045c162e33185adf7a9f2adb
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 10656
content:
"CMIP6 projections indicate that the Northern Annular Mode (NAM; \r\nAnnex IV.2.1) is expected to become more positive in winter \r\nthroughout the 21st century in the SSP3-7.0 and SSP5-8.5 scenarios \r\n(Section 4.5.1). In the near term, the Southern Annular Mode (SAM, \r\nAnnex IV.2.2) is projected to become less positive than observed \r\nduring the end of the 20th century during the austral summer in all \r\nSSPs scenarios (Section 4.3.3.1). "


id: e2588ab237261a2ea64921ad209843f8
created_at: 2023-04-19 13:21:38
updated_at: 2023-04-19 13:21:38
content_type: text
index: climate_gpt_v2
vector_id: 37112
content:
"In the CMIP5 RCP8.5 scenario, increased amplitude and frequency \r\nof the North Atlantic Oscillation (NAO, Annex IV.2) during boreal \r\nwinter (December-January-February, DJF) is associated with higher \r\nprecipitation in northern Europe and lower precipitation in southern \r\nEurope (Tsanis and Tapoglou, 2019). However, large-ensemble \r\nanalyses show how the NAO leads to significant uncertainty in future \r\nchanges of regional climate (Section 8.5.2). For example, more than \r\na 85% increase in precipitation is projected over northern Europe, \r\nwestern Russia and much of eastern North America, with similar \r\ndecreasing resulting in drying over north-western Africa and regions \r\nadjacent to the Mediterranean Sea (Deser et al., 2017). "


