# document

id: 50eaf2c052c4104e689a9374b471f607
created_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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"Instrument simulators provide estimates of what a  satellite would \r\nsee if looking down on the model-simulated planet, and improve the \r\ndirect comparison of modelled variables such as clouds, precipitation \r\nand upper tropospheric humidity with observations from satellites \r\n(e.g., Kay et al., 2011; Klein et al., 2013; Cesana and Waliser, 2016; \r\nKonsta et al., 2016; Jin et al., 2017; Chepfer et al., 2018; Swales \r\net al., 2018; Zhang et al., 2018). Within the framework of the Cloud \r\nFeedback Model Intercomparison Project (CFMIP) contribution to \r\nCMIP6 (Webb et al., 2017), a  new version of the Cloud Feedback "


id: 6e96443acff5bf5e4cbac0f8d2923b1
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"variation in the real world can be converted, via the model-based \r\nrelationship, into an 'emergent constraint' on the sensitivity. This is \r\nshown schematically in Figure 1.23 (see Glossary; Eyring et al., 2019)."


id: e9e7f69bf961aaf32d5cca4bbcc938ea
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"et al., 2017; Lorenz et al., 2018; Liang et al., 2020). However, models \r\nmay share representations of processes, parameterization schemes, \r\nor even parts of code, leading to common biases. The models may \r\ntherefore not be fully independent, calling into question inferences \r\nderived from multi-model ensembles (Abramowitz et al., 2019). \r\nEmergent constraints (Section  1.5.4.5) also represent an implicit \r\nweighting technique that explicitly links present performance to future \r\nprojections (Bracegirdle and Stephenson, 2013)."


id: d6c3f72244ea5630fbfb3fc3cbb88f92
created_at: 2023-04-19 13:21:32
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"Several recent studies have attempted to quantify the effect of various \r\nstrategies for selection or weighting of ensemble members based \r\non some set of criteria (Haughton et al., 2015; Olonscheck and Notz, \r\n2017; Sanderson et al., 2017). Model weighting strategies have been \r\nfurther employed since AR5 to reduce the spread in climate projections \r\nfor a given scenario by using weights based on one or more model \r\nperformance metrics (Wenzel et al., 2016; Knutti et al., 2017; Sanderson "


id: e141f79657b062ca495d55473017ab8c
created_at: 2023-04-19 13:21:32
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"This section is structured as follows: first, the scenarios used in AR6 \r\nare introduced and discussed in relation to scenarios used in earlier \r\nIPCC assessments (Section 1.6.1). Cross-Chapter Box 1.4 provides an \r\noverview of the new set of illustrative scenarios and how they are \r\nused in this report. Next, the two additional dimensions of integration \r\nare introduced: global warming levels (Section 1.6.2) and cumulative \r\nCO2 emissions (Section 1.6.3). Net zero emissions are discussed in \r\nBox 1.4. The relation between global warming levels and scenarios is \r\nfurther assessed in Cross-Chapter Box 11.1 in Chapter 11."


id: e4598e588c98e7357bd6fb43eea4fc00
created_at: 2023-04-19 13:21:32
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"A scenario is a description of how the future may develop, based on \r\na coherent and internally consistent set of assumptions about key \r\ndrivers including demography, economic processes, technological \r\ninnovation, governance, lifestyles, and relationships among these \r\ndriving forces (Section 1.6.1.1; IPCC, 2000; Rounsevell and Metzger, \r\n2010; O'Neill et al., 2014). Scenarios can also be defined by \r\ngeophysical driving forces only, such as emissions or abundances of \r\nGHGs, aerosols, and aerosol precursors or land-use patterns. Scenarios \r\nare not predictions; instead, they provide a 'what-if' investigation of \r\nthe implications of various developments and actions (Moss et al., \r\n2010). WGI investigates potential future climate change principally \r\nby assessing climate model simulations using emissions scenarios "


id: 9def0da8feb516628b9f949a292c65a3
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"Figure 1.24 | The dimensions of integration across chapters and Working Groups in the IPCC AR6 Assessment. This Report adopts three explicit dimensions of \r\nintegration to integrate knowledge across chapters and Working Groups. The first dimension is scenarios; the second dimension is global mean warming levels relative to pre\u0002industrial levels; and the third dimension is cumulative CO2 emissions. For the scenarios, illustrative 2100 end-points are also indicated (white circles). Further details on data \r\nsources and processing are available in the chapter data table (Table 1.SM.1)."


id: 88a45a043d46ea9f3c47053e7ff84a4f
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"originating from the WGIII community (Section 1.6.1.2). The scenarios \r\nused in this WGI Report cover various hypothetical 'baseline \r\nscenarios' or 'reference futures' that could unfold in the absence of \r\nany - or any additional - climate policies (Glossary). These 'reference \r\nscenarios' originate from a comprehensive analysis of a wide array \r\nof socio-economic drivers, such as population growth, technological \r\ndevelopment, and economic development, and their broad spectrum \r\nof associated energy, land use and emissions implications (Riahi et al., \r\n2017). With direct policy relevance to the Paris Agreement's 1.5degC \r\nand 'well below' 2degC goals, this Report also assesses climate futures \r\nwhere the effects of additional climate change mitigation action are \r\nexplored, i.e., so-called mitigation scenarios (for a broader discussion \r\nof scenarios and futures analysis, see Cross-Chapter Box 1, Table 1 in \r\nSRCCL, IPCC, 2019a)."


id: e86cca4d2f5785556f10ae9db6c05f10
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"economic development only (O'Neill et al., 2014). However, at least in \r\nthe WGI community, the term 'SSP scenario' is now more widely used \r\nto refer directly to future emissions and concentration scenarios that \r\nresult from combining these socio-economic development pathways \r\nwith climate change mitigation assumptions. These are assessed in \r\ndetail in WGIII (AR6 WGIII Chapter 3) and in Cross-Chapter Box 1.4, \r\nTable 1 in this chapter."


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"This Report uses a  core set of five illustrative SSP scenarios \r\nto assist  cross-Chapter integration and cross-Working Group \r\napplications: SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5 \r\n(Cross-Chapter Box  1.4, Table  1). These scenarios span a  wide \r\nrange of plausible societal and climatic futures from potentially \r\nbelow 1.5degC best-estimate warming to over 4degC warming by 2100 \r\n(Figure  1.25). The  set of five SSP scenarios includes those in 'Tier \r\n1' simulations of the CMIP6 ScenarioMIP intercomparison project \r\n(Section  1.5.4; O'Neill et al., 2016) that participating climate \r\nmodelling groups were asked to prioritize (SSP1-2.6, SSP2-4.5, \r\nSSP3-7.0 and SSP5-8.5), plus the low emissions scenario SSP1-1.9. \r\nSSP1-1.9 is used in combination with SSP1-2.6 to explore differential "


id: 32b9f08de7f02381b0da350992c95533
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"For this Report, the main emissions, concentration and land-use \r\nscenarios considered are a  subset of scenarios recently developed \r\nusing the Shared Socio-economic Pathways framework (SSPs; \r\nSection  1.6.1.1 and Cross-Chapter Box  1.4; Riahi et al., 2017). \r\nInitially, the term 'SSP' described five broad narratives of future socio\u0002"


id: 2253fa4afca4457887d8582e05797c35
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"Pathways (RCPs) is also used in this Report when assessing future \r\nclimate change (Section 1.6.1.3 and Cross-Chapter Box 1.4, Table 1)."


id: bb351eaa60bad2f93746a6f3a29cbf8c
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"outcomes of approximately 1.5degC and 2.0degC warming relative to \r\npre-industrial levels, relevant to the Paris Agreement goals. Further \r\nSSP scenarios are used in this report to assess specific aspects of, for \r\nexample, air pollution policies in Chapter 6 (Cross-Chapter Box 1.4). \r\nIn addition, the previous generation of Representative Concentration "


id: 8c16ed9995b917d693af64b85b09a65f
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"models, conditional on the various SSP scenarios. The projected future \r\nchanges can then be put into the context of longer-term paleoclimate \r\ndata and historical observations, showing how the higher emissions \r\nand higher concentration scenarios diverge further from the range of \r\nclimate conditions that ecosystems and human societies experienced \r\nin the past 2000  years in terms of global mean temperature and \r\nother key climate variables (Figures 1.26 and 1.5)."


id: 7b65bc1309e57a7d764c90fb30e056f1
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"(GDP) and urbanization (Dellink et al., 2017; Jiang and O'Neill, 2017; \r\nSamir and Lutz, 2017). By design, the SSPs differ in terms of the socio\u0002economic challenges they present for climate change mitigation and \r\nadaptation (Rothman et al., 2014; Schweizer and O'Neill, 2014) and \r\nthe evolution of these drivers within each SSP reflects this design. \r\nBroadly, the five SSPs represent 'sustainability' (SSP1), a 'middle-of\u0002the-road' path (SSP2), 'regional rivalry' (SSP3), 'inequality' (SSP4), \r\nand 'fossil fuel-intensive' development (SSP5; Cross-Chapter Box 1.4, \r\nFigure 1; O'Neill et al., 2017a). More specific information on the SSP \r\nframework and the assumptions underlying the SSPs will be provided \r\nin the IPCC WGIII report (WGIII Chapter  3; see also Box SPM.1 in \r\nSRCCL (IPCC, 2019d))."


id: ebfb9ef2b24e5fbad8bc2f93edf0d130
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"While scenarios are a key tool for integration across IPCC Working \r\nGroups, they also allow the integration of knowledge among \r\nscientific communities and across time scales. For example, \r\nagricultural yield, infrastructure and human health impacts of \r\nincreased drought frequency, extreme rainfall events and hurricanes \r\nare often examined in isolation. New insights on climate impacts in \r\nWGII can be gained if compound effects of multiple cross-sectoral \r\nimpacts are considered across multiple research communities under \r\nconsistent scenario frameworks (Section 11.8; Leonard et al., 2014; \r\nWarszawski et al., 2014). Similarly, a synthesis of WGI knowledge \r\non sea level rise contributions is enabled by a consistent application \r\nof future scenarios across all specialized research communities, \r\nsuch as ice-sheet mass balance analyses, glacier loss projections \r\nand thermosteric change from ocean heat uptake (Chapter  9; \r\ne.g. Kopp et al., 2014)."


id: 994b6f59dab2d8959ddc91f69f05db7d
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"The SSP narratives and drivers were used to develop scenarios of \r\nenergy use, air pollution control, land use, and GHG emissions \r\ndevelopments using integrated assessment models (IAMs; Riahi et al., \r\n2017; Rogelj et al., 2018a). An IAM can derive multiple emissions \r\nfutures for each socio-economic development pathway, assuming \r\nno new mitigation policies or various levels of additional mitigation \r\naction (in the case of reference scenarios and mitigation scenarios, \r\nrespectively; Riahi et al., 2017). By design, the evolution of drivers \r\nand emissions within the SSP scenarios do not take into account the \r\neffects of climate change."


id: 74838c09021e15ac8535c56bc98af39a
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"In addition to the comprehensive SSP scenario set and the RCPs, \r\nmultiple idealized scenarios and time-slice experiments using \r\nclimate models are assessed in this Report. Idealized scenarios refer \r\nto experiments where, for example, CO2 concentrations are increased \r\nby 1% per year, or instantly quadrupled. Such idealized experiments \r\nhave been extensively used in previous model intercomparison \r\nprojects and constitute the core 'DECK' set of model experiments of \r\nCMIP6 (Section 1.5.4). They are, for example, used to diagnose the \r\npatterns of climate feedbacks across the suite of models assessed in \r\nthis Report (Chapter 7)."


id: fde1b8d7a29c4d0d88df3a7cf6749ef2
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"The SSPX-Y scenarios and the RCP scenarios are categorized similarly, \r\nby reference to the approximate radiative forcing levels each one \r\nentails at the end of the 21st century. For example, the '1.9' in the \r\nSSP1-1.9 scenario stands for an approximate radiative forcing level of \r\n1.9 W m-2 in 2100. The first number (X) in the 'SSPX-Y' acronym refers \r\nto one of the five shared socio-economic development pathways \r\n(Cross-Chapter Box 1.4, Figure 1 and Table 1.4)."


id: c84ef16429725729e1a63c2bfef0af03
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"This SSP scenario categorization, focused on end-of-century radiative \r\nforcing levels, reflects how scenarios were conceptualized until \r\nrecently, namely, to reach a particular climate target in 2100 at the \r\nlowest cost and irrespective of whether the target was exceeded over \r\nthe century. More recently, and in particular since IPCC SR1.5 report \r\nfocused attention on peak warming scenarios (Rogelj et al., 2018b), \r\nscenario development started to explicitly consider peak warming, \r\ncumulative emissions and the amount of net negative emissions \r\n(Rogelj et al., 2018b; Fujimori et al., 2019)."


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"In the following section, we further introduce the SSP scenarios and \r\nhow they relate to the Shared Socio-economic Pathways framework \r\n(Section  1.6.1.1); describe the scenario generation process \r\n(Section 1.6.1.2); and provide a historical review of scenarios used in \r\nIPCC assessment reports (Section 1.6.1.3); before briefly discussing \r\nquestions of scenario likelihood, scenario uncertainty and the use of \r\nscenario storylines (Section 1.6.1.4)."


id: df6c9d8f326ce0097faf360c4c72c21b
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"The Shared Socio-economic Pathways SSP1 to SSP5 describe a range \r\nof plausible trends in the evolution of society over the 21st century. \r\nThey were developed in order to connect a wide range of research \r\ncommunities (Nakicenovic et al., 2014) and consist of two main \r\nelements: a set of qualitative, narrative storylines describing societal \r\nfutures (O'Neill et al., 2017a) and a  set of quantified measures \r\nof development at aggregated and/or spatially resolved scales. \r\nEach pathway is an internally consistent, plausible and integrated \r\ndescription of a  socio-economic future, but these socio-economic \r\nfutures do not account for the effects of climate change, and no new \r\nclimate policies are assumed. The SSPs' quantitative projections of \r\nsocio-economic drivers include population, gross domestic product "


id: 36dcf0a93187b5ec46a786ab3eca44d0
created_at: 2023-04-19 13:21:32
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"may differ, and tends to be higher for the SSPs compared to RCPs \r\nthat share the same nominal stratospheric-temperature-adjusted \r\nradiative forcing label. The stratospheric-temperature-adjusted \r\nradiative forcings of the SSPs and RCPs, however, remain relatively \r\nclose, at least by 2100 (Tebaldi et al., 2021). In summary, differences \r\nin, for example, CMIP5 RCP8.5 and CMIP6 SSP5-8.5 ESM outputs, are \r\npartially due to different scenario characteristics rather than different \r\nESM characteristics only (Section 4.6.2)."


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"A key advance of the SSP scenarios relative to the RCPs is a wider \r\nspan of assumptions on future air-quality mitigation measures, and \r\nhence emissions of short-lived climate forcers (SLCFs; Rao et al., \r\n2017; Lund et al., 2020). This allows for a more detailed investigation \r\ninto the relative roles of GHG and SLCF emissions in future global \r\nand regional climate change, and hence the implications of policy \r\nchoices. For instance, SSP1-2.6 builds on an assumption of stringent \r\nair-quality mitigation policy, leading to rapid reductions in particle \r\nemissions, while SSP3-7.0 assumes slow improvements, with \r\npollutant emissions over the 21st  century comparable to current \r\nlevels (Figure 6.19 and Cross-Chapter Box 1.4, Figure 2)."


id: 3bd0ba9c3c1133f9ecdf0ec657c373d2
created_at: 2023-04-19 13:21:32
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"When investigating various mitigation futures, WGIII goes beyond \r\nthe core set of SSP scenarios assessed in WGI (SSP1-1.9, SSP1-2.6, \r\netc.) to consider the characteristics of more than 1000 scenarios \r\n(Cross-Chapter Box  7.1). In addition, while staying within the \r\nframework of socio-economic development pathways (SSP1 to \r\nSSP5), WGIII also considers various mitigation possibilities through \r\nso-called illustrative pathways (IPs). These illustrative pathways \r\nhelp to highlight key narratives in the literature concerning various \r\ntechnological, social and behavioural options for mitigation, various \r\ntimings for implementation, or varying emphasis on different GHG \r\nand land-use options. Just as with the SSPX-Y scenarios considered \r\nin this Report, these illustrative pathways can be placed in relation to \r\nthe matrix of SSP families and approximate radiative forcing levels in \r\n2100 (Cross-Chapter Box 1.4, Figure 1; IPCC WGIII, Chapter 3)."


id: 5240cf4d630840dde10887b4f45db701
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"One limitation of the SSP scenarios used for CMIP6 and in this Report \r\nis that they reduce emissions from all the major ozone-depleting \r\nsubstances controlled under the Montreal Protocol (CFCs, halons, \r\nand hydrochlorofluorocarbons (HCFCs)) uniformly, rather than \r\nrepresenting a  fuller range of possible high- and low-emissions \r\nfutures (UNEP, 2016). Hydrofluorocarbon (HFC) emissions, on the \r\nother hand, span a wider range within the SSPs than in the RCPs \r\n(Cross-Chapter Box 1.4, Figure 2)."


id: 2bfedc928b05bf86e62bd8f6a254fdd1
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"No likelihood is attached to the scenarios assessed in this report, \r\nand the feasibility of specific scenarios in relation to current trends \r\nis best informed by the WGIII contribution to AR6. In the scenario \r\nliterature, the plausibility of the high emissions levels underlying \r\nscenarios such as RCP8.5 or SSP5-8.5 has been debated in light of \r\nrecent developments in the energy sector (Section 1.6.1.4)."


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"The SSP scenarios and previous RCP scenarios are not directly \r\ncomparable. First, the gas-to-gas compositions differ; for example, \r\nthe SSP5-8.5 scenario has higher CO2 concentrations but lower CH4\r\nconcentrations compared to RCP8.5. Second, the projected 21st\u0002century trajectories may differ, even if they result in the same radiative \r\nforcing by 2100. Third, the overall effective radiative forcing (Chapter 7) "


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"Contributing Authors: Jan S. Fuglestvedt (Norway), Celine Guivarch (France), Christopher Jones (United Kingdom), Malte \r\nMeinshausen (Australia/Germany), Zebedee R. J. Nicholls (Australia), Gian-Kasper Plattner (Switzerland), Keywan Riahi (Austria), Joeri \r\nRogelj (United Kingdom/Belgium), Sophie Szopa (France), Claudia Tebaldi (United States of America), Anne-Marie Treguier (France), \r\nand Detlef van Vuuren (The Netherlands)"


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"The nine new SSP emissions and concentrations scenarios (SSP1-1.9 to SSP5-8.5; Cross-Chapter Box 1.4, Table 1) offer unprecedented \r\ndetail of input data for climate model simulations. They allow for a more comprehensive assessment of climate drivers and responses \r\nthan has previously been available, in particular because some of the scenarios' time series, (e.g., pollutants, emissions or changes \r\nin land use and land cover), are more diverse in the SSP scenarios than in the RCPs used in AR5 (Cross-Chapter Box 1.4, Figure 2; \r\ne.g., Chuwah et al., 2013)."


id: 32e100b607a7d4e819251c06f7abc933
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"a\r\n The AerChemMIP variant of SSP3-7.0-lowNTCF (Collins et al., 2017) only reduced aerosol and ozone precursors compared to SSP3-7.0, not methane. \r\nThe SSP3-7.0-lowNTCF variant by the integrated assessment models also reduced methane emissions (Gidden et al., 2019), which creates differences between \r\nSSP3-7.0-lowNTCF and SSP3-7.0 also in terms of methane concentrations and some fluorinated gas concentrations that have OH related sinks (Meinshausen et al., 2020)."


id: 9b172ce8b829137b953e337cc64ca376
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"Cross-Chapter Box 1.4, Table 2 | Overview of key climate forcer datasets used as input by ESMs for historical and future SSP scenario experiments.\r\nThe data is available from the Earth System Grid Federation (ESGF, 2021) described in Eyring et al. (2016)."


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"In contrast to stylized assumptions about the future evolution of emissions (e.g., a linear phase-out from year A to year B), these \r\nSSP scenarios are the result of a detailed scenario generation process (Sections 1.6.1.1 and 1.6.1.2). While IAMs produce internally \r\nconsistent future-emissions time series for CO2, CH4, N2O, and aerosols for the SSP scenarios (Riahi et al., 2017; Rogelj et al., 2018a), \r\nthese emissions scenarios are subject to several processing steps for harmonization (Gidden et al., 2018) and in-filling (Lamboll et al., \r\n2020), before also being complemented by several datasets so that ESMs can run these SSPs (Durack et al., 2018; Tebaldi et al., 2021). \r\nAlthough five scenarios are the primary focus of WGI, a total of nine SSP scenarios have been prepared with all the necessary detail \r\nto drive the ESMs as part of the CMIP6 (Cross-Chapter Box 1.4, Figure 1 and Table 2)."


id: 835aaa109d92c905b72e5c18bfac9eeb
created_at: 2023-04-19 13:21:32
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content:
"The so-called 'emissions-driven' experiments (Jones et al., 2016) use the same input datasets as concentration-driven ESM experiments, \r\nexcept that they use CO2 emissions rather than concentrations (Chapter 5 and Section 4.3.1). In these experiments, atmospheric CO2\r\nconcentrations are calculated internally using the ESM interactive carbon cycle module and thus differ from the prescribed default CO2\r\nconcentrations used in the concentration-driven runs. In the particular case of SSP5-8.5, the emissions-driven runs are assessed to add \r\nno significant additional uncertainty to future global surface air temperature (GSAT) projections (Section 4.3.1). However, generally, \r\nwhen assessing uncertainties in future climate projections, it is important to consider which elements of the cause-effect chain, \r\nfrom emissions to the resulting climate change, are interactively included as part of the model projections, and which are externally \r\nprescribed using default settings."


id: 9abc2f977326b22e81878b7da58745b8
created_at: 2023-04-19 13:21:32
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content:
"ss-Chapter Box  1.4, Figure  2 | Comparison between the Shared Socio-economic Pathways (SSP) scenarios and the Representative \r\ncentration Pathway (RCP) scenarios in terms of their CO2, CH4 and N2O atmospheric concentrations (a-c), and their global emissions of CO2, \r\n N2O, black carbon (BC), organic carbon (OC), sulphur dioxide (SO2), ammonia (NH3), nitrogen oxides (NOx), volatile organic compounds \r\nC), sulphur hexafluoride (SF6), perfluorocarbons (PFCs), and hydrofluorocarbons (HFCs) (d-o). "


id: ca36f13bf559d8fa963466e380673a11
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content:
"Cross-Chapter Box 1.4, Figure 2 (continued): Also shown are gridded emissions differences for SO2 (p) and black carbon (q) for the year 2000 between the \r\ninput emissions datasets that underpinned the CMIP5 and CMIP6 model intercomparisons. Historical emissions estimates are provided in black in panels (d-o). The \r\nrange of concentrations and emissions investigated under the RCP pathways is shaded grey. Panels (p) and (q) adapted from Figure 7 in Hoesly et al. (2018). Further \r\ndetails on data sources and processing are available in the chapter data table (Table 1.SM.1)."


id: 61826b33d56e55735e04a081ab016da9
created_at: 2023-04-19 13:21:32
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vector_id: 14451
content:
"series (documented for CMIP6 through input4mips; Cross-Chapter \r\nBox 1.4, Table 2; Durack et al., 2018)."


id: a526a30d2869f564c53592d9b2fd8d8d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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content:
"The scenario generation process involves research communities \r\nlinked to all three IPCC Working Groups (Figure 1.27). It generally \r\nstarts in the scientific communities associated with WGII and WGIII \r\nwith the definition of new socio-economic scenario storylines (IPCC, \r\n2000; O'Neill et al., 2014) that are quantified in terms of their \r\ndrivers  - i.e.,  GDP, population, technology, energy and land use  - \r\nand their resulting emissions (Riahi et al., 2017). Then, numerous \r\ncomplementation and harmonization steps are necessary for datasets \r\nwithin the WGI and WGIII science communities, including gridding \r\nemissions of anthropogenic short-lived forcers, providing open \r\nbiomass-burning emissions estimates, preparing land-use patterns, \r\naerosol fields, stratospheric and tropospheric ozone, nitrogen \r\ndeposition datasets, solar irradiance and aerosol optical property \r\nestimates, and observed and projected GHG concentration time "


id: d1ab6b76be096af8dc4101ba66ddd6ce
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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content:
"Once these datasets are completed, ESMs are run in coordinated \r\nmodel intercomparison projects in the WGI science community, \r\nusing standardized simulation protocols and scenario data. The most \r\nrecent example of such a coordinated effort is the CMIP6 exercise \r\n(Section  1.5.4; Eyring et al., 2016) with, in particular, ScenarioMIP \r\n(O'Neill et al., 2016). The WGI science community feeds back climate \r\ninformation to WGIII via climate emulators (Cross-Chapter Box 7.1) \r\nthat are updated and calibrated with the ESMs' temperature \r\nresponses and other lines of evidence. Next, this climate information \r\nis used to compute several high-level global climate indicators \r\n(e.g., atmospheric concentrations, global temperatures) for a much \r\nwider set of hundreds of scenarios that are assessed as part of the \r\nIPCC WGIII Assessment (WGIII Annex C). The outcomes from climate \r\nmodels run under the different scenarios are then used to calculate "


id: 1a527f4af6c896522b196f17086718d2
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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content:
"Figure  1.28 |  Comparison of the range of fossil fuel and industrial CO\r\n2\r\nemissions from scenarios used in previous assessments up to AR6. Previous \r\nassessments are the IS92 scenarios from 1992 (top), the Special Report on Emissions \r\nScenarios (SRES) scenarios from the year 2000 (second panel), the Representative \r\nConcentration Pathway (RCP) scenarios designed around 2010 (third panel) and \r\nthe Shared Socio-economic Pathways (SSP) scenarios (fourth panel). In addition, \r\nhistorical emissions are shown (black line; Figure  5.5); a  more complete set of \r\nscenarios is assessed in SR1.5 (bottom); (Huppmann et al., 2018). Further details on \r\ndata sources and processing are available in the chapter data table (Table 1.SM.1)."


id: ee41eb9efa22e92d8ff77aed4d736eef
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
vector_id: 39289
content:
"the evolution of climatic impact-drivers (Chapter  12), and utilized \r\nby impact researchers together with exposure and vulnerability \r\ninformation, in order to characterize risk to human and natural \r\nsystems from future climate change. The climate impacts associated \r\nwith these scenarios or different warming levels are then assessed as \r\npart of WGII reports (Figure 1.27)."


id: 1d3869e0b2e8794420ba0f26f993d93c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
vector_id: 2319
content:
"Scenario modelling experiments have been a  core element of \r\nphysical climate science since the first transient simulations with \r\na general circulation model in 1988 (Section 1.3; Hansen et al., 1988). \r\nScenarios and modelling experiments assessed in IPCC reports have \r\nevolved over time, which provides a 'history of how the future was \r\nseen'. The starting time for the scenarios moves as actual emissions \r\nsupersede earlier emissions assumptions, while new scientific insights \r\ninto the range of plausible population trends, behavioural changes \r\nand technology options and other key socio-economic drivers of \r\nemissions also emerge (see WGIII; Leggett et al., 1992; IPCC, 2000; \r\nMoss et al., 2010; Riahi et al., 2017). Many different sets of climate \r\nprojections have been produced over the past several decades, using \r\ndifferent sets of scenarios. Here, we compare those earlier scenarios \r\nagainst the most recent ones."


id: 23b94b3c806aa6309915735408b864b8
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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content:
"Climate science research involving scenarios necessarily follows \r\na  series of consecutive steps (Figure  1.27). As each step waits for \r\ninput from the preceding one, delays often occur that result in the \r\nimpact literature basing its analyses on earlier scenarios than those \r\nmost current in the climate change mitigation and climate system \r\nliterature. It is therefore important to provide an approximate \r\ncomparison across the various scenario generations (Chapter  4, \r\nFigure 1.28, and Cross-Chapter Box 1.4, Table 1)."


id: f51e240822bbbfd0fc213a35e7178424
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"The first widely used set of IPCC emissions scenarios was the \r\nIS92 scenarios in 1992 (Leggett et al., 1992). Apart from reference \r\nscenarios, IS92 also included a  set of stabilization scenarios, the \r\nso-called 'S' scenarios. Those 'S' pathways were designed to lead \r\nto CO\r\n2 stabilization levels such as 350 ppm or 450 ppm. By 1996, \r\nthose latter stabilization levels were complemented in the scientific \r\nliterature by alternative trajectories that assumed a delayed onset of \r\nclimate change mitigation action (Figure 1.28; Wigley et al., 1996)."


id: 1306cbee069d0b5c1c52fe35434135ab
created_at: 2023-04-19 13:21:32
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content:
"By 2000, the IPCC Special Report on Emissions Scenarios (SRES) \r\nproduced the SRES scenarios (IPCC, 2000), albeit without assuming \r\nany climate policy-induced mitigation. The four broad groups of \r\nSRES scenarios (scenario 'families') - A1, A2, B1 and B2 - were the \r\nfirst scenarios to emphasize socio-economic scenario storylines, and \r\nalso first to emphasize other GHGs, land-use change and aerosols. "


id: b3170c26781430df7af185f536a1ea09
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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content:
"Represented by three scenarios for the high-growth A1 scenario \r\nfamily, those 6 SRES scenarios (A1FI, A1B, A1T, A2, B1, and B2) can \r\nstill sometimes be found in today's climate impact literature. The void \r\nof missing climate change mitigation scenarios was filled by a range \r\nof community exercises, including the so-called 'post-SRES scenarios' \r\n(Swart et al., 2002)."


id: 5e148dafaf1f576c0c4f7d3e31763b14
created_at: 2023-04-19 13:21:32
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content:
"low aerosol trajectories across all scenarios (Cross-Chapter Box 1.4, \r\nFigure 2). More generally, the SSP scenarios feature a later peak of \r\nglobal emissions for the lower scenarios, simply as a consequence of \r\nhistorical emissions not having followed the trajectory projected by \r\nprevious low scenarios (Figure 1.28)."


id: 157e90822a64ae3a057c46413826f853
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
vector_id: 995
content:
"Over the last decades, discussions around scenarios have often \r\nfocussed on whether recent trends make certain future scenarios \r\nmore or less probable or whether all scenarios are too high or too \r\nlow. When the SRES scenarios first appeared, the debate was often \r\nwhether the scenarios were overestimating actual world emissions \r\ndevelopments (e.g., Castles and Henderson, 2003). With the strong \r\nemissions increase throughout the 2000s, that debate then shifted \r\ntowards the question of whether the lower future climate change \r\nmitigation scenarios were rendered unfeasible (Pielke et al., 2008; \r\nvan Vuuren and Riahi, 2008). Historical emissions between 2000 and \r\n2010 approximately track the upper half of SRES and RCP projections \r\n(Figure 1.28). More generally, the global fossil fuel and industrial CO2\r\nemissions of recent decades tracked approximately the middle of \r\nthe projected scenario ranges (Figure 1.28), although with regional \r\ndifferences (Pedersen et al., 2020)."


id: 39bf46785d60adb4b6285fb125b71fe4
created_at: 2023-04-19 13:21:32
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content:
"By design, the RCP emissions and concentrations pathways were \r\noriginally developed using particular socio-economic development \r\npathways, but those are no longer considered (Moss et al., 2010). \r\nThe different levels of emissions and climate change represented in \r\nthe RCPs can hence be explored against the backdrop of different \r\nsocio-economic development pathways (SSP1 to SSP5; Section 1.6.1.1 \r\nand Cross-Chapter Box  1.4). This integrative SSP-RCP framework \r\n('SSPX-RCPY' in Table 1.4) is now widely used in the climate impact \r\nand policy analysis literature (e.g., ICONICS, 2021; Green et al., 2020; \r\nO'Neill et al., 2020), where climate projections obtained under the \r\nRCP scenarios are analysed against the backdrop of various SSPs. \r\nConsidering various levels of future emissions and climate change for \r\neach socio-economic development pathway was an evolution from \r\nthe previous SRES framework (IPCC, 2000), in which socio-economic \r\nand emissions futures were closely aligned."


id: 185075bfb0aeddd9dfc623f654ce5773
created_at: 2023-04-19 13:21:32
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content:
"The new set of scenarios (SSP1-1.9 to SSP5-8.5) now features \r\na higher top level of CO2 emissions (SSP5-8.5 compared to RCP8.5), \r\nalthough the most significant change is again the addition of a very \r\nlow climate change mitigation scenario (SSP1-1.9, compared to the \r\nprevious low scenario, RCP2.6). Also, historically, none of the previous \r\nscenario sets featured a  scenario that involves a  very pronounced \r\npeak-and-decline emissions trajectory, but SSP1-1.9 does so now. \r\nThe full set of nine SSP scenarios now includes a  high-aerosol\u0002emissions scenario (SSP3-7.0). The RCPs featured more uniformly "


id: 7d27fe7da09b0bc574bdf7b88023f530
created_at: 2023-04-19 13:21:32
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content:
"In this Report, the term 'global warming level' refers to the \r\ncategorization of global and regional climate change, associated \r\nimpacts, emissions and concentrations scenarios by GMST relative \r\nto 1850-1900, which is the period used as a proxy for pre-industrial \r\nlevels (Cross-Chapter Box 11.1). By default, GWLs are expressed in \r\nterms of global surface air temperature (GSAT; Section  1.4.1 and \r\nCross-Chapter Box 2.3)."


id: 32894926d9ff9dc3d4383b7779328d68
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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content:
"As SR1.5 concluded, even half-degree global mean temperature \r\nsteps carry robust differences in climate impacts (Chapter 11; SR1.5, \r\nIPCC, 2018; Schleussner et al., 2016a; Wartenburger et al., 2017). This \r\nReport adopts half-degree warming levels, which allows integration \r\nfor climate projections, impacts, adaptation challenges and mitigation \r\nchallenges within and across the three WGs. The core set of GWLs - \r\n1.5degC, 2.0degC, 3.0degC and 4.0degC - are highlighted (Chapters 4, 8, 11, \r\n12 and Atlas). Given that much impact analysis is based on previous \r\nscenarios, (i.e., RCPs or SRES), and climate change mitigation analysis \r\nis based on new emissions scenarios in addition to the main SSP \r\nscenarios, these GWLs assist in the comparison of climate states \r\nacross scenarios and in the synthesis across the broader literature."


id: b3e27bb95301acd721c617c04668850b
created_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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content:
"The transient and equilibrium states of certain global warming levels \r\ncan differ in their climate impacts (IPCC, 2018; King et al., 2020). \r\nClimate impacts in a 'transient' world relate to a scenario in which \r\nthe world is continuing to warm. On the other hand, climate impacts \r\nat the same warming levels can also be estimated from equilibrium \r\nstates after a  (relatively) short-term stabilization by the end of \r\nthe 21st  century or at a  (near-)equilibrium state after a  long-term \r\n(multi-decadal to multi-millennial) stabilization. Different methods to \r\nestimate these climate states come with challenges and limitations \r\n(Section  4.6.1 and Cross-Chapter Box  11.1). First,  information \r\ncan be drawn from GCM or ESM simulations that 'pass through' \r\nthe respective warming levels (as used and demonstrated in the \r\nInteractive Atlas), also called 'epoch' or 'time-shift' approaches \r\n(Sections  4.2.4 and 4.6.1; Herger et al., 2015; James et al., 2017; "


id: 454107f4cf0c0d266a3b3cd9b6f06a34
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index: climate_gpt_v2
vector_id: 9411
content:
"Tebaldi and Knutti, 2018). Information from transient simulations can \r\nalso be used through an empirical scaling relationship (Seneviratne \r\net al., 2016, 2018; Wartenburger et al., 2017) or using 'time sampling' \r\napproaches, as described in James et al. (2017). Second, information \r\ncan be drawn from large ESM ensembles with prescribed SST at \r\nparticular global warming levels (Mitchell et al., 2017), although an \r\nunderrepresentation of variability can arise when using prescribed \r\nSST temperatures (E.M. Fischer et al., 2018)."


id: f8a5bca32040c564452767ec1857425c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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content:
"The AR5 WGI (IPCC, 2013a) and SR1.5 (IPCC, 2018) highlighted \r\nthe near-linear relationship between cumulative carbon emissions \r\nand global mean warming (Sections 1.3 and 5.5). This implies that \r\ncontinued CO2 emissions will cause further warming and changes \r\nin all components of the climate system, independent of any \r\nspecific scenario or pathway. This is captured in the TCRE concept, \r\nwhich relates CO2-induced global mean warming to cumulative \r\ncarbon emissions (Chapter 5). This Report thus uses cumulative CO2\r\nemissions to compare the climate response across scenarios, and \r\nto categorize emissions scenarios (Figure  1.29). The advantage of \r\nusing cumulative CO2 emissions is that it is an inherent emissions \r\nscenario characteristic rather than an outcome of the scenario\u0002based projections, where uncertainties in the cause-effect chain - \r\nfrom emissions to atmospheric concentrations to temperature \r\nchange - are important."


id: 189b885b36639109a6525a9b6b5a780c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
vector_id: 1544
content:
"Also, forcing or response patterns that vary in time can create \r\ndifferences in regional climates for the same global mean warming \r\nlevel, or can create non-linearities when scaling patterns from one \r\nwarming level to another (King et al., 2018), depending on whether \r\nnear-term transient climate, end of the century, equilibrium climate \r\nor climate states after an initial overshoot are considered."


id: 6da699c6b5b142cd131539268cdac730
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
vector_id: 16547
content:
"In spite of these challenges, and thanks to recent methodological \r\nadvances in quantifying or overcoming them, global warming \r\nlevels provide a  robust and useful integration mechanism. They \r\nallow knowledge from various domains within WGI and across \r\nthe three WGs to be integrated and communicated (Cross-Chapter \r\nBox 11.1). In this report, Chapters 4, 8, 11, 12 and the Atlas provide \r\ninformation specific to certain warming levels, highlighting the \r\nregional differences, but also the approximate scalability of regional \r\nclimate change, that can arise from even a 0.5degC shift in global mean \r\ntemperatures. Furthermore, building on WGI insights into physical \r\nclimate system responses (Cross-Chapter Box  7.1), WGIII will use \r\npeak and end-of-century global warming levels to classify a broad \r\nset of scenarios."


id: ec6ed4ee6159f147c7394dbc5a281a88
created_at: 2023-04-19 13:21:32
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index: climate_gpt_v2
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content:
"Box 1.4 | The Relationships Between 'Net Zero' Emissions, Temperature Outcomes \r\nand Carbon Dioxide Removal"


id: 768a911b3437c666e070f43ec3aaac7a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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"Article 4 of the Paris Agreement sets an objective to 'achieve a balance between anthropogenic emissions by sources and removals by \r\nsinks of greenhouse gases' (Section 1.2). This box addresses the relationship between such a balance and the corresponding evolution \r\nof global surface temperature, with or without the deployment of large-scale carbon dioxide removal (CDR), using the definitions of \r\n'net zero CO2 emissions' and 'net zero greenhouse gas (GHG) emissions' of the AR6 Glossary (Annex VII)."


id: 599220293f5ae5e81bf948074c5b82b0
created_at: 2023-04-19 13:21:32
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content:
"'Net zero CO2 emissions' is defined in AR6 as the condition in which anthropogenic CO2 emissions are balanced by anthropogenic CO2\r\nremovals over a specified period. Similarly, 'net zero GHG emissions' is the condition in which metric-weighted anthropogenic GHG\r\nemissions are balanced by metric-weighted anthropogenic GHG removals over a  specified period. The quantification of net zero \r\nGHG emissions thus depends on the GHG emissions metric chosen to compare emissions of different gases, as well as the time horizon \r\nchosen for that metric. (For a broader discussion of metrics, see Box 1.3 and Section 7.6, and WGIII Cross-Chapter Box 2.)"


id: c00f0028eccbc7d86c7bf529ff11bc3e
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content:
"Technical notes expanding on these definitions can be found as part of their respective entries in the Glossary. The notes clarify the \r\nrelation between 'net zero' CO2 and GHG emissions and the concept of carbon and GHG neutrality, and the metric usage set out in \r\nthe Paris Rulebook [Decision 18/CMA.1, annex, paragraph 37]."


id: 17a86f9a593a8ca46b740ed23bf63ad4
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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content:
"A global net zero level of CO2, or GHG, emissions will be achieved when the sum of anthropogenic emissions and removals across all \r\ncountries, sectors, sources and sinks reaches zero. Achieving net zero CO2 or GHG emissions globally, at a given time, does not imply \r\nthat individual entities (i.e., countries, sectors) have to reach net zero emissions at that same point in time, or even at all (see WGIII, \r\nTS Box 4 and Chapter 3)."


id: e8836d33ae97a3d21cbbc29d1822ffc0
created_at: 2023-04-19 13:21:32
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content_type: text
index: climate_gpt_v2
vector_id: 38246
content:
"Net zero CO2 and net zero GHG emissions differ in their implications for the subsequent evolution of global surface temperature. Net \r\nzero CO2 emissions result in approximately stable CO2-induced warming, but overall warming will depend on any further warming \r\ncontribution of non-CO2 GHGs. The effect of net zero GHG emissions on global surface temperature depends on the GHG emissions \r\nmetric chosen to aggregate emissions and removals of different gases. For GWP100 (the metric in which Parties to the Paris Agreement \r\nhave decided to report their aggregated emissions and removals), net zero GHG emissions would generally imply a peak in global \r\nsurface temperature, followed by a gradual decline (Section 7.6.2; see also Section 4.7.1 regarding the zero emissions commitment). \r\nHowever, other anthropogenic factors, such as aerosol emissions or land use-induced changes in albedo, may still affect the climate."


id: 13e2478b0633acddebe25d01e4474c57
created_at: 2023-04-19 13:21:32
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vector_id: 716
content:
"The definitions of net zero CO2 and GHG should also be seen in relation to the various CDR methods discussed in the context of \r\nclimate change mitigation (see Section 5.6, which also includes an assessment of the response of natural sinks to CDR), and how it is \r\nemployed in scenarios used throughout the WGI and WGIII reports (Section 1.6.1; see also WGIII Chapters 3, 7 and 12.)"


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vector_id: 19882
content:
"For virtually all scenarios assessed by the IPCC, CDR is necessary to reach both global net zero CO2 and net zero GHG emissions, to \r\ncompensate for residual anthropogenic emissions. This is in part because for some sources of CO2 and non-CO2 emissions, abatement \r\noptions to eliminate them have not yet been identified. For a given scenario, the choice of GHG metric determines how much net CDR \r\nis necessary to compensate for residual non-CO2 emissions, in order to reach net zero GHG emissions (Section 7.6.2)."


id: 29f9925d2d0acd1ef6fd4b57465af5f5
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
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vector_id: 4606
content:
"If CDR is further used to go beyond net zero, to a situation with net-negative CO2 emissions (i.e., where anthropogenic removals \r\nexceed anthropogenic emissions), anthropogenic CO2-induced warming will decline. A further increase of CDR, until a situation with \r\nnet zero or even net-negative GHG emissions is reached, would increase the pace at which historical human-induced warming is \r\nreversed after its peak (SR1.5, IPCC, 2018). Net negative anthropogenic GHG emissions may become necessary to stabilize the global \r\nsurface temperature in the long term, should climate feedbacks further affect natural GHG sinks and sources (Chapter 5)."


id: f8e4d4e3fa960b4365f368ac6b691394
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 41154
content:
"the 21st century (as in the case of sea level rise), are nevertheless \r\nrelevant for decision-making."


id: a3e923bc26421bb229d9c53fda94b657
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 26029
content:
"The assessment in this Report is based on a rapidly growing body \r\nof new evidence from the peer-reviewed literature. Recently, \r\nscientific climate change research has doubled in output every \r\n5-6 years; the majority of publications deal with issues related to \r\nthe physical climate system (Burkett et al., 2014; Haunschild et al., \r\n2016). The sheer volume of published, peer-reviewed literature on \r\nclimate change presents a challenge to comprehensive, robust and \r\ntransparent assessment."


id: 96cc29d04bbf88b8de8e5b055f85721e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 23727
content:
"At the time of publication, the consequences of the COVID-19 \r\npandemic on emissions, atmospheric abundances, radiative forcing \r\nand the climate (Cross-Chapter Box  6.1), and on observations \r\n(Section  1.5.1), are not yet fully evident. Their assessment in this \r\nReport is thus limited."


id: ac1f6d2294ee3f12aca412a813094466
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 27526
content:
"The enhanced focus on regional climate in AR6 WGI further \r\nexpands the volume of literature relative to AR5, including non\u0002English language publications sometimes presented as reports \r\n('grey' literature), particularly on topics such as regional observing \r\nnetworks and climate services. These factors enhance the challenge \r\nof discovering, accessing and assessing the relevant literature. \r\nThe international, multilingual author teams of IPCC AR6, combined \r\nwith the open expert-review process, help to minimize these concerns, \r\nbut they remain a challenge."


id: 20c64f2a61fb0d63352b5dd400f91aa1
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 2986
content:
"Despite the key role of CMIP6 in this Report (Section 1.5), the number \r\nof studies evaluating its results and modelling systems remains \r\nrelatively limited. At the time of publication, additional model \r\nresults are still becoming available. This reflects the need for close \r\ntemporal alignment of the CMIP cycle with the IPCC assessment \r\nprocess, and the growing complexity of coordinated international \r\nmodelling efforts."


id: d9562cd3bc505f28b69f301c764e2160
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 35538
content:
"Indigenous and local knowledge includes information about past \r\nand present climate states. However, assessing this knowledge, and \r\nintegrating it with the scientific literature, remains a challenge to be \r\nmet. This lack of assessment capability and integration leads to most \r\nWGI chapters still not including indigenous and local knowledge in \r\ntheir assessment findings."


id: d24736e92c656086562e25e20e9290c0
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 34349
content:
"Spatial and temporal gaps in both historical and current observing \r\nnetworks, and the limited extent of paleoclimatic archives, have \r\nalways posed a challenge for IPCC assessments. A relative paucity of \r\nlong-term observations is particularly evident in Antarctica and in the \r\ndepths of the ocean. Knowledge of previous cryospheric and oceanic \r\nprocesses is therefore incomplete. Sparse instrumental temperature \r\nobservations prior to the industrial revolution make it difficult to \r\nuniquely characterize a 'pre-industrial' baseline, although this Report \r\nextends the assessment of anthropogenic temperature change \r\nfurther back in time than previous assessment cycles (Chapter 7 and \r\nCross-Chapter Box 1.2)."


id: 5c5308bdf7090081038032407500a6d1
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 13493
content:
"Common, integrating scenarios can never encompass all possible \r\nevents that might induce radiative forcing in the future (Section 1.4). \r\nThese may include large volcanic eruptions (Cross-Chapter Box 4.1), \r\nthe consequences of a  major meteorite, smoke plumes following \r\na conflict involving nuclear weapons, extensive geoengineering, or \r\na major pandemic (Cross-Chapter Box 1.6). Scenario-related research \r\nalso often focuses on the 21st century. Post-2100 climate changes \r\nare not covered as comprehensively, and their assessment is limited. \r\nThose long-term climate changes, potentially induced by forcing over "


id: c24b058e03c57135e7f337ff202437bc
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 31467
content:
"Yes, much better. The first IPCC report, released in 1990, concluded that human-caused climate change would \r\nsoon become evident, but could not yet confirm that it was already happening. Today, evidence is overwhelming \r\nthat the climate has indeed changed since the pre-industrial era and that human activities are the principal cause \r\nof that change. With much more data and better models, we also understand more about how the atmosphere \r\ninteracts with the ocean, ice, snow, ecosystems and land surfaces of the Earth. Computer climate simulations \r\nhave also improved dramatically, incorporating many more natural processes and providing projections at much \r\nhigher resolutions."


id: 4d1eeb06c75a374464f0cd80d519022a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10842
content:
"Since the first IPCC report in 1990, large numbers of new instruments have been deployed to collect data in the \r\nair, on land, at sea and from outer space. These instruments measure temperature, clouds, winds, ice, snow, \r\nocean currents, sea level, soot and dust in the air, and many other aspects of the climate system. New satellite \r\ninstruments have also provided a wealth of increasingly fine-grained data. Additional data from older observing \r\nsystems and even hand-written historical records are still being incorporated into observational datasets, and \r\nthese datasets are now better integrated and adjusted for historical changes in instruments and measurement \r\ntechniques. Ice cores, sediments, fossils, and other new evidence from the distant past have taught us much \r\nabout how Earth's climate has changed throughout its history."


id: 3292be0a009e73effe25de7dcb561c11
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 6156
content:
"Understanding of climate system processes has also improved. For example, in 1990 very little was known about \r\nhow the deep ocean responds to climate change. Today, reconstructions of deep-ocean temperatures extend as \r\nfar back as 1871. We now know that the oceans absorb most of the excess energy trapped by greenhouse gases \r\nand that even the deep ocean is warming up. As another example, in 1990, relatively little was known about \r\nexactly how or when the gigantic ice sheets of Greenland and Antarctica would respond to warming. Today, \r\nmuch more data and better models of ice-sheet behaviour reveal unexpectedly high melt rates that will lead to \r\nmajor changes within this century, including substantial sea level rise (FAQ 9.2)."


id: 83d4dbdbb2e97b96b3276949611a961c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 20337
content:
"The major natural factors contributing to climate change on time scales of decades to centuries are volcanic \r\neruptions and variations in the sun's energy output. Today, data show that changes in incoming solar energy \r\nsince 1900 have contributed only slightly to global warming, and they exhibit a slight downward trend since the \r\n1970s. Data also show that major volcanic eruptions have sometimes cooled the entire planet for relatively short \r\nperiods of time (typically several years) by erupting aerosols (tiny airborne particles) high into the atmosphere."


id: 191e48e346a1552c1a0a24bf998f5136
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 1635
content:
"The main human causes of climate change are the heat-absorbing greenhouse gases released by fossil fuel \r\ncombustion, deforestation, and agriculture, which warm the planet; and aerosols such as sulphate from burning \r\ncoal, which have a short-term cooling effect that partially counteracts human-caused warming. Since 1990, we \r\nhave more and better observations of these human factors as well as improved historical records, resulting in \r\nmore precise estimates of human influence on the climate system (FAQ 3.1)."


id: 56c1a165a3b16a856965401e7157c720
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 12513
content:
"While most climate models in 1990 focused on the atmosphere, using highly simplified representations of oceans \r\nand land surfaces, today's Earth system simulations include detailed models of oceans, ice, snow, vegetation and \r\nmany other variables. An important test of models is their ability to simulate Earth's climate over the period \r\nof instrumental records (since about 1850). Several rounds of such testing have taken place since 1990, and \r\nthe testing itself has become much more rigorous and extensive. As a group and at large scales, models have \r\npredicted the observed changes well in these tests (FAQ 3.3). Since there is no way to do a controlled laboratory \r\nexperiment on the actual Earth, climate model simulations can also provide a kind of 'alternate Earth' to test \r\nwhat would have happened without human influence. Such experiments show that the observed warming \r\nwould not have occurred without human influence."


id: 6ba2cd1940d3014db4c716672ca63017
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 16241
content:
"Finally, physical theory predicts that human influence on the climate system should produce specific patterns \r\nof change, and we see those patterns in both observations and climate simulations. For example, nights are \r\nwarming faster than days, less heat is escaping to space, and the lower atmosphere (troposphere) is warming but \r\nthe upper atmosphere (stratosphere) has cooled. These confirmed predictions are all evidence of changes driven \r\nprimarily by increases in GHG concentrations rather than natural causes."


id: 4e3cd058191b6b62df6ccc093467690a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 11034
content:
"Yes. Between 1990 and 2021, observations, models and climate understanding improved, while the dominant \r\nrole of human influence in global warming was confirmed.\r\nFAQ 1.1: Do we understand climate change better than when the IPCC started?"


id: c1c07e3600729c3654e3f633044d5c36
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 31390
content:
"FAQ 1.1, Figure 1 | Sample elements of climate understanding, observations and models as assessed in the IPCC First Assessment Report \r\n(1990) and Sixth Assessment Report (2021). Many other advances since 1990, such as key aspects of theoretical understanding, geological records and \r\nattribution of change to human influence, are not included in this figure because they are not readily represented in this simple format. Fuller explanations of \r\nthe history of climate knowledge are available in the introductory chapters of the IPCC Fourth and Sixth assessment reports."


id: 57158d3c5da1fd5df17a8e12e0919f55
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 12576
content:
"The signs of climate change are unequivocal at the global scale and are increasingly apparent on smaller spatial \r\nscales. The high northern latitudes show the largest temperature increase, with clear effects on sea ice and \r\nglaciers. The warming in the tropical regions is also apparent because the natural year-to-year variations in \r\ntemperature there are small. Long-term changes in other variables such as rainfall and some weather and climate \r\nextremes have also now become apparent in many regions."


id: 9dfa0332596b45025a7d70b86a1cfe0e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 25029
content:
"It was first noticed that the planet's land areas were warming in the 1930s. Although increasing atmospheric \r\ncarbon dioxide (CO2) concentrations were suggested as part of the explanation, it was not certain at the time \r\nwhether the observed warming was part of a long-term trend or a natural fluctuation: global warming had not \r\nyet become apparent. But the planet continued to warm, and by the 1980s the changes in temperature had \r\nbecome obvious or, in other words, the signal had emerged."


id: 97047aaf5a29560400e2057f3c1d1dd8
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 23760
content:
"Imagine you had been monitoring temperatures at the same location for the past 150 years. What would you \r\nhave experienced? When would the warming have become noticeable in your data? The answers to these \r\nquestions depend on where on the planet you are."


id: 6dfc43cc1fece97c6f2b2b584a9fb60c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 16614
content:
"Observations and climate model simulations both demonstrate that the largest long-term warming trends are in \r\nthe high northern latitudes and the smallest warming trends over land are in tropical regions. However, the year\u0002to-year variations in temperature are smallest in the tropics, meaning that the changes there are also apparent, \r\nrelative to the range of past experiences (FAQ 1.2, Figure 1)."


id: 16b632d48d38f06b390b08bcf3ff356
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 1206
content:
"Changes in temperature also tend to be more apparent over land areas than over the open ocean and are often \r\nmost apparent in regions which are more vulnerable to climate change. It is expected that future changes will \r\ncontinue to show the largest signals at high northern latitudes, but with the most apparent warming in the \r\ntropics. The tropics also stand to benefit the most from climate change mitigation in this context, as limiting \r\nglobal warming will also limit how far the climate shifts relative to past experience."


id: e8fdb58d7f3f24220128302ec65885ab
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 38342
content:
"Changes in other climate variables have also become apparent at smaller spatial scales. For example, changes \r\nin average rainfall are becoming clear in some regions, but not in others, mainly because natural year-to-year \r\nvariations in precipitation tend to be large relative to the magnitude of the long-term trends. However, extreme \r\nrainfall is becoming more intense in many regions, potentially increasing the impacts from inland flooding (FAQ \r\n8.2). Sea levels are also clearly rising on many coastlines, increasing the impacts of inundation from coastal storm \r\nsurges, even without any increase in the number of storms reaching land. A decline in the amount of Arctic sea \r\nice is apparent, both in the area covered and in its thickness, with implications for polar ecosystems."


id: 4a3f0aa2fb2858d640ee830cc5630816
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10303
content:
"When considering climate-related impacts, it is not necessarily the size of the change that is most important. \r\nInstead, it can be the rate of change or it can also be the size of the change relative to the natural variations \r\nof the climate to which ecosystems and society are adapted. As the climate is pushed further away from past \r\nexperiences and enters an unprecedented state, the impacts can become larger, along with the challenge of \r\nadapting to them."


id: 66333f2b477d76771af275f8fa1a6457
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 15247
content:
"How and when a long-term trend becomes distinguishable from shorter-term natural variations depends on the \r\naspect of climate being considered (e.g., temperature, rainfall, sea ice or sea level), the region being considered, \r\nthe rate of change, and the magnitude and timing of natural variations. When assessing the local impacts from \r\nclimate change, both the size of the change and the amplitude of natural variations matter."


id: 88420ded3d09f54a910a24fe94210870
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21127
content:
"FAQ 1.2, Figure 1 | Observed variations in regional temperatures since 1850 (data from Berkeley Earth). Regions in high latitudes, such as \r\nmid-North America (40degN-64degN, 140degW-60degW, left), have warmed by a larger amount than regions at lower latitudes, such as tropical South America \r\n(10degS-10degN, 84degW-16degW, right), but the natural variations are also much larger at high latitudes (darker and lighter shading represents 1 and 2 standard \r\ndeviations, respectively, of natural year-to-year variations). The signal of observed temperature change emerged earlier in tropical South America than mid\u0002North America even though the changes were of a smaller magnitude. (Note that those regions were chosen because of the longer length of their observational \r\nrecord; see Figure 1.14 for more regions)."


id: a76f8664836b45a5f7555c1f67ca9022
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 26671
content:
"In the past, the Earth has experienced prolonged periods of elevated greenhouse gas concentrations that caused \r\nglobal temperatures and sea levels to rise. Studying these past warm periods informs us about the potential long\u0002term consequences of increasing greenhouse gases in the atmosphere."


id: 472734ce7b8b6695dc8188b6509e832
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 9720
content:
"Rising greenhouse gas concentrations are driving profound changes to the Earth system, including global \r\nwarming, sea level rise, increases in climate and weather extremes, ocean acidification, and ecological shifts \r\n(FAQ 2.2 and FAQ 7.1). The vast majority of instrumental observations of climate began during the 20th century, \r\nwhen greenhouse gas emissions from human activities became the dominant driver of changes in Earth's \r\nclimate (FAQ 3.1)."


id: ce2e3aff7a9ec922c1e0be1bb658e818
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 33609
content:
"While present-day warming is unusual in the context of the recent geologic past in several different ways \r\n(FAQ 2.1), past warm climate states present a  stark reminder that the long-term adjustment to present-day \r\natmospheric carbon dioxide concentrations has only just begun. That adjustment will continue over the coming \r\ncenturies to millennia."


id: adb4deea8ae082d6c05e59350a9c4d35
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 27805
content:
"FAQ 1.3, Figure 1 | Comparison of past, present and future. Schematic of atmospheric carbon dioxide concentrations, global temperature, and global \r\nsea level during previous warm periods as compared to 1850-1900, present-day (2011-2020), and future (2100) climate change scenarios corresponding to \r\nlow-emissions scenarios (SSP1-2.6; lighter colour bars) and very high-emissions scenarios (SSP5-8.5; darker colour bars)."


id: 4a84940462a9e1162ac679c72aeb32c9
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10350
content:
"nt Report (AR5\r\nessment Repor\r\n3b), and the I\r\nstat\r\nde, \r\nve \r\n of \r\nnd \r\nres \r\nare \r\n \r\nose \r\nare \r\nTotal rais positito an upby the cThe largto total is causein the aconcentsince 17\r\n \r\nThe totaradiativ2011 re2.29 [1.and it hrapidly during ptotal anestimathigher tin AR4 fThe totasolar irrand straaerosols contriburadiativthe last brief pevolcanic"


id: dacb4ae985ef46fa2017e263505096b8
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 35787
content:
"Jinho Ahn (Republic of Korea), Frank J. Dentener (EU/The Netherlands), Catia M. Domingues \r\n(Australia, United Kingdom/Brazil), Sebastian Gerland (Norway/Germany), Daoyi Gong (China), \r\nDarrell S. Kaufman (United States of America), Hyacinth C. Nnamchi (Nigeria, Germany/Nigeria), \r\nJohannes Quaas (Germany), Juan A. Rivera (Argentina), Shubha Sathyendranath (United Kingdom/\r\nCanada, Overseas citizen of India, United Kingdom), Sharon L. Smith (Canada), Blair Trewin \r\n(Australia), Karina von Schuckmann (France/Germany), Russell S. Vose (United States of America)"


id: 4ff1b1b7b91bcac8137920cc2ce7a2c2
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 11356
content:
"Katherine J. Dooley (Ireland), Therese A. Myslinski (Ireland), David N. Smyth (Ireland/United \r\nKingdom, Ireland)"


id: e9bc72c6acccf57522a9bbc65cde4af9
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 38476
content:
"Gulev, S.K., P.W. Thorne, J. Ahn, F.J. Dentener, C.M. Domingues, S. Gerland, D. Gong, D.S. Kaufman, H.C. Nnamchi, \r\nJ.  Quaas, J.A. Rivera, S. Sathyendranath, S.L. Smith, B. Trewin, K. von Schuckmann, and R.S. Vose, 2021: Changing \r\nState of the Climate System. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group \r\nI to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, \r\nA. Pirani, S.L. Connors, C. Pean, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, \r\nJ.B.R.  Matthews, T.K. Maycock, T. Waterfield, O. Yelekci, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, \r\nCambridge, United Kingdom and New York, NY, USA, pp. 287-422, doi:10.1017/9781009157896.004. "


id: 87b0a891ca047a84666e646c5834ac64
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21031
content:
"Tropospheric aerosol concentrations across the Northern \r\nHemisphere mid-latitudes increased from 1700 to the last \r\nquarter of the 20th century, but have subsequently declined \r\n(high confidence). Aerosol optical depth (AOD) has decreased \r\nsince 2000 over Northern Hemisphere mid-latitudes and Southern \r\nHemisphere mid-latitude continents, but increased over South \r\nAsia and East Africa (high confidence). These trends are even more \r\npronounced in AOD from sub-micrometre aerosols for which the \r\nanthropogenic contribution is particularly large. The best-estimate of \r\naerosol ERF in 2019 relative to 1750 is -1.1 W m-2. {2.2.6, 7.3.3}"


id: 175b00efae2608971600a3fe1a6d5448
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 1331
content:
"Chapter 2 assesses observed large-scale changes in climate system \r\ndrivers, key climate indicators and principal modes of variability. \r\nChapter 3 considers model performance and detection/attribution, \r\nand Chapter 4 covers projections for a subset of these same indicators \r\nand modes of variability. Collectively, these chapters provide the basis \r\nfor later chapters, which focus upon processes and regional changes. \r\nWithin Chapter 2, changes are assessed from in situ and remotely \r\nsensed data and products and from indirect evidence of longer-term \r\nchanges based upon a diverse range of climate proxies. The time\u0002evolving availability of observations and proxy information dictate \r\nthe periods that can be assessed. Wherever possible, recent changes \r\nare assessed for their significance in a longer-term context, including \r\ntarget proxy periods, both in terms of mean state and rates of change."


id: 61cff051c17def10ed51bd013b0f323e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 14494
content:
"Changes in other short-lived gases are associated with an \r\noverall positive ERF (medium confidence). Stratospheric ozone \r\nhas declined between 60degS and 60degN by 2.2% from the 1980s to \r\n2014-2017 (high confidence). Since the mid-20th century, tropospheric \r\nozone has increased by 30-70% across the Northern Hemisphere \r\n(medium confidence). Since the mid-1990s, free tropospheric ozone \r\nincreases were 2-7% per decade in the northern mid-latitudes (high \r\nconfidence), 2-12% per decade in the tropics (high confidence) and \r\n<5% per decade in southern mid-latitudes (medium confidence). The \r\nbest estimate of ozone column ERF (0.5 W m-2 relative to 1750) is \r\ndominated by changes in tropospheric ozone. Due to discrepancies \r\nin satellite and in situ records, there is low confidence in estimates of \r\nstratospheric water vapour change. {2.2.5, 7.3.2}"


id: bc4b739322fc004d8d028a3f497b6145
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 30373
content:
"Climate system drivers lead to climate change by altering the Earth's \r\nenergy balance. The influence of a climate driver is described in terms \r\nof its effective radiative forcing (ERF), measured in W m-2. Positive \r\nERF values exert a warming influence and negative ERF values exert \r\na cooling influence (Chapter 7)."


id: 1d15ac565ca4432a611fc656fd96104b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 2296
content:
"Present-day global concentrations of atmospheric carbon \r\ndioxide (CO2) are at higher levels than at any time in at least \r\nthe past two million years (high confidence). Changes in ERF \r\nsince the late 19th century are dominated by increases in \r\nconcentrations of greenhouse gases and trends in aerosols; \r\nthe net ERF is positive and changing at an increasing rate since \r\nthe 1970s (medium confidence). {2.2, 7.2, 7.3}"


id: b58547387858feb53f2e223b363a38cd
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 29158
content:
"Biophysical effects from historical changes in land use have \r\nan overall negative ERF (medium confidence). The best-estimate \r\nERF from the increase in global albedo is -0.15 W m-2 since 1700 and \r\n-0.12 W m-2 since 1850 (medium confidence). {2.2.7, 7.3.4}"


id: 4e568ae71a64074f2460904e1e549722
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 11056
content:
"Observed changes in the atmosphere, oceans, cryosphere and \r\nbiosphere provide unequivocal evidence of a world that has \r\nwarmed. Over the past several decades, key indicators of the \r\nclimate system are increasingly at levels unseen in centuries \r\nto millennia, and are changing at rates unprecedented in at \r\nleast the last 2000 years (high confidence). Temperatures as high \r\nas during the most recent decade (2011-2020) exceed the warmest \r\ncentennial-scale range reconstructed for the present interglacial, \r\naround 6,500 years ago [0.2degC-1degC relative to 1850-1900] (medium \r\nconfidence). The next older warm period is the last interglacial \r\nwhen the multi-centennial temperature range about 125,000 years \r\nago [0.5degC-1.5degC relative to 1850-1900] encompassed the recent \r\ndecade values (medium confidence). {2.3}"


id: 9ab1d285833d88857e2f69eca562da15
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24458
content:
"Change in ERF from natural factors since 1750 is negligible in \r\ncomparison to anthropogenic drivers (very high confidence). \r\nSolar activity since 1900 was high but not exceptional compared \r\nto the past 9000 years (high confidence). The average magnitude \r\nand variability of volcanic aerosol forcing since 1900 have not been \r\nunusual compared to the past 2500 years (medium confidence). \r\n{2.2.1, 2.2.2}"


id: 11574d76eafdbaa2d1a24d7e4a71dca
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 249
content:
"In 2019, concentrations of CO2, methane (CH4) and nitrous \r\noxide (N2O) reached levels of 409.9 (+-0.4) parts per million \r\n(ppm), 1866.3 (+-3.3) parts per billion (ppb) and 332.1 (+-0.4) \r\nppb, respectively. Since 1850, these well-mixed greenhouse \r\ngases (GHGs) have increased at rates that have no precedent \r\non centennial time scales in at least the past 800,000 years.\r\nConcentrations of CO2, CH4, and N2O increased from 1750 to 2019 by \r\n131.6 +- 2.9 ppm (47.3%), 1137 +- 10 ppb (156%), and 62 +- 6 ppb \r\n(23.0%) respectively. These changes are larger than those between \r\nglacial and interglacial periods over the last 800,000 years for CO2\r\nand CH4 and of comparable magnitude for N2O (very high confidence). \r\nThe best estimate of the total ERF from CO2, CH4 and N2O in 2019 \r\nrelative to 1750 is 2.9 W m-2, an increase of 12.5% from 2011. ERF \r\nfrom halogenated components in 2019 was 0.4 W m-2, an increase of \r\n3.5% since 2011. {2.2.3, 2.2.4, 7.3.2}"


id: f297d077d9c2971f4fd6d3a54d51f2cf
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 40082
content:
"GMST increased by 0.85 [0.69 to 0.95] degC between 1850-1900 \r\nand 1995-2014 and by 1.09 [0.95 to 1.20] degC between \r\n1850-1900 and 2011-2020. From 1850-1900 to 2011-2020, \r\nthe temperature increase over land (1.59 [1.34 to 1.83] degC) \r\nhas been faster than over the oceans (0.88 [0.68 to 1.01] degC).\r\nGMST in the first two decades of the 21st century (2001-2020) was \r\n0.99 [0.84-1.10] degC higher than 1850-1900. Each of the last four \r\ndecades has successively been warmer than all preceding decades \r\nsince 1850. Over the last 50 years, observed GMST has increased at \r\na rate unprecedented in at least the last 2000 years (high confidence). "


id: ee8ee45360c4bdeeb503f23dc4cd2dfd
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 39349
content:
"minor differences between sea ice area decadal means for 1979-1988 \r\n(2.04 million km2 for February, 15.39 million km2 for September) and \r\n2010-2019 (2.17 million km2 for February, 15.75  million km2 for \r\nSeptember). {2.3.2.1}"


id: 54a975d7b6dedaad7d25b9fb834d1220
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 12169
content:
"The increase in GMST since the mid-19th century was preceded by \r\na slow decrease that began in the mid-Holocene (around 6500 years \r\nago) (medium confidence). {2.3.1.1, Cross-Chapter Box 2.1}"


id: 9ec6f0c331a9a5346530a00f32937299
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 25153
content:
"Changes in GMST and global surface air temperature (GSAT) \r\nover time differ by at most 10% in either direction  (high \r\nconfidence), and the long-term changes in GMST and GSAT are \r\npresently assessed to be identical. There is expanded uncertainty \r\nin GSAT estimates, with the assessed change from 1850-1900 to \r\n1995-2014 being 0.85 [0.67 to 0.98] degC. {Cross-Chapter Box 2.3}"


id: 85d673e0a91d6ce4b3c9bfc32468bb6
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 20690
content:
"The troposphere has warmed since at least the 1950s, and it is \r\nvirtually certain that the stratosphere has cooled. In the Tropics, \r\nthe upper troposphere has warmed faster than the near-surface since \r\nat least 2001, the period over which new observational techniques \r\npermit more robust quantification (medium confidence). It is virtually \r\ncertain that the tropopause height has risen globally over 1980-2018, \r\nbut there is low confidence in the magnitude. {2.3.1.2}"


id: f2d673ad9a148146b12138a8e698027b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 40122
content:
"Changes in several components of the global hydrological \r\ncycle provide evidence for overall strengthening since at least \r\n1980 (high confidence). However, there is low confidence\r\nin comparing recent changes with past variations due to \r\nlimitations in paleoclimate records at continental and global \r\nscales. Global land precipitation has likely increased since 1950, \r\nwith a faster increase since the 1980s (medium confidence). Near\u0002surface specific humidity has increased over both land (very likely) \r\nand the oceans (likely) since at least the 1970s. Relative humidity has \r\nvery likely decreased over land areas since 2000. Global total column \r\nwater vapour content has very likely increased during the satellite \r\nera. Observational uncertainty leads to low confidence in global \r\ntrends in precipitation minus evaporation and river runoff. {2.3.1.3}"


id: 1f96ac053eda6c9060c2761facc0fc47
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 2768
content:
"Global mean sea level (GMSL) is rising, and the rate of GMSL \r\nrise since the 20th century is faster than over any preceding \r\ncentury in at least the last three millennia (high confidence). \r\nSince 1901, GMSL has risen by 0.20 [0.15 to 0.25] m, and the \r\nrate of rise is accelerating. The average rate of sea level rise \r\nwas 1.3 [0.6 to 2.1] mm yr -1 between 1901 and 1971, increasing \r\nto 1.9 [0.8 to 2.9] mm yr -1 between 1971 and 2006, and further \r\nincreasing to 3.7 [3.2 to 4.2] mm yr -1 between 2006 and 2018 \r\n(high confidence). Further back in time, there is medium confidence\r\nthat GMSL was within -3.5 to +0.5 m (very likely) of present during \r\nthe mid-Holocene (6000 years ago), 5 to 10 m (likely) higher during \r\nthe Last Interglacial (125,000 years ago), and 5 to 25 m (very likely) \r\nhigher during the mid-Pliocene Warm Period (MPWP) (3.3 million \r\nyears ago). {2.3.3.3}"


id: fdb5a3dc9d862504e25983ff231bb234
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 41998
content:
"Several aspects of the large-scale atmospheric circulation have \r\nlikely changed since the mid-20th century, but limited proxy \r\nevidence yields low confidence in how these changes compare \r\nto longer-term climate. The Hadley circulation has likely widened \r\nsince at least the 1980s, and extratropical storm tracks have likely\r\nshifted poleward in both hemispheres. Global monsoon precipitation \r\nhas likely increased since the 1980s, mainly in the Northern Hemisphere \r\n(medium confidence). Since the 1970s, near-surface winds have \r\nlikely weakened over land. Over the oceans, near-surface winds likely\r\nstrengthened over 1980-2000, but divergent estimates lead to low \r\nconfidence in the sign (direction) of change thereafter. It is likely that \r\nthe northern stratospheric polar vortex has weakened since the 1980s \r\nand experienced more frequent excursions toward Eurasia. {2.3.1.4}"


id: df1ed7ff68a384a7f4af75b429ebdbc6
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 36507
content:
"Current Arctic sea ice coverage levels are the lowest since at \r\nleast 1850 for both annual mean and late-summer values (high \r\nconfidence) and for the past 1000 years for late-summer values \r\n(medium confidence). Between 1979 and 2019, Arctic sea ice area \r\nhas decreased in both summer and winter, with sea ice becoming \r\nyounger, thinner and more dynamic (very high confidence). Decadal \r\nmeans for Arctic sea ice area decreased from 6.23 million  km2 in \r\n1979-1988 to 3.76 million km2 in 2010-2019 for September and \r\nfrom 14.52 to 13.42 million km2 for March. Antarctic sea ice area has \r\nexperienced little net change since 1979 (high confidence), with only "


id: 5918f2c801d85b15df8c4b316bab1902
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 12917
content:
"most open ocean regions during the mid 20th to early 21st centuries \r\n(high confidence), with decadal variability (medium confidence). \r\nOxygen minimum zones are expanding at many locations (high \r\nconfidence). {2.3.3}"


id: e7da438591de50625daabdeb6f2f6859
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 38100
content:
"the 23rd century [1.0degC to 2.2degC]. During the mid-Pliocene Warm \r\nPeriod, the GMST estimate [2.5degC to 4.0degC] is similar to the range \r\nprojected under SSP2-4.5 for the end of the 23rd century [2.3degC to \r\n4.6degC]. GMST estimates for the Miocene Climatic Optimum [5degC to \r\n10degC] and Early Eocene Climatic Optimum [10degC to 18degC], about \r\n15 and 50 million years ago, respectively, overlap with the range \r\nprojected for the end of the 23rd century under SSP5-8.5 [6.6degC to \r\n14.1degC]. {Cross-Chapter Box 2.1, 2.3.1, 4.3.1.1, 4.7.1.1}"


id: e096237655db0c6c1884942841e37efc
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 36766
content:
"Changes in key global aspects of the terrestrial biosphere \r\nare consistent with large-scale warming (high confidence).\r\nOver the last century, there have been poleward and upslope shifts \r\nin the distributions of many land species (very high confidence) as \r\nwell as increases in species turnover within many ecosystems (high \r\nconfidence). Over the past half century, climate zones have shifted \r\npoleward, accompanied by an increase in the length of the growing \r\nseason in the Northern Hemisphere extratropics and an increase in \r\nthe amplitude of the seasonal cycle of atmospheric CO2 above 45degN \r\n(high confidence). Since the early 1980s, there has been a global-scale \r\nincrease in the greenness of the terrestrial surface (high confidence). \r\n{2.3.4.1, 2.3.4.3}"


id: 6b680ce7d31b1d91e407596dca72fa13
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 16196
content:
"During the mid-Pliocene warm period (MPWP, 3.3 to 3.0 million \r\nyears ago) slowly changing large-scale indicators reflect \r\na  world that was warmer than present, with CO2 similar to \r\ncurrent levels. CO2 levels during the MPWP were similar to present \r\nfor a sustained period, within a range of 360-420 ppm (medium \r\nconfidence). Relative to the present, GMST, GMSL and precipitation \r\nrate were all higher, the Northern Hemisphere latitudinal temperature \r\ngradient was lower, and major terrestrial biomes were shifted \r\nnorthward (very high confidence). There is high confidence that \r\ncryospheric indicators were diminished and medium confidence\r\nthat the Pacific longitudinal temperature gradient weakened and \r\nmonsoon systems strengthened. {2.3, Cross-Chapter Box 2.4, 9.6.2}"


id: 88f4b13f0daeb902088e8ed69d9ecb38
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21259
content:
"Inferences from past climate states based on proxy records can \r\nbe compared with climate projections over coming centuries \r\nto place the range of possible futures into a longer-term \r\ncontext. There is medium confidence in the following mappings \r\nbetween selected paleo periods and future projections: during the \r\nLast Interglacial, GMST is estimated to have been 0.5degC-1.5degC \r\nwarmer than the 1850-1900 reference for a sustained period, which \r\noverlaps the low end of the range of warming projected under \r\nSSP1-2.6, including its negative-emissions extension to the end of "


id: 593592cd6c8c44f647b7a9c815cee12
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 12936
content:
"the recent past is applied to the extent permitted by available data \r\n(Section 1.4.1 and Cross-Chapter Box 2.1). In all cases, the narrative \r\nproceeds from as far in the past as the data permit through to the \r\npresent. Each sub-section starts by highlighting the key findings \r\nfrom AR5 and any relevant AR6-cycle Special Reports (SROCC, \r\nSR1.5, SRCCL), and then outlines the new evidence-basis arising \r\nfrom a combination of: (i) new findings reported in the literature, \r\nincluding new datasets and new versions of existing datasets; \r\nand (ii) recently observed changes, before closing with a  new \r\nsummary assessment. "


id: 15fb40f2dc2acf9c67610231504d8bfb
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 1084
content:
"Trends, when calculated as part of this assessment, have wherever \r\npossible been calculated using a common approach following \r\nthat adopted in Box 2.2 of Chapter 2 of AR5 (Hartmann et  al., \r\n2013). In addition to trends, consideration is also made of \r\nchanges between various time slices/periods in performing the \r\nassessment (Section 1.4.1 and Cross-Chapter Box 2.1). Statistical \r\nsignificance of trends and changes are assessed at the two-tailed \r\n90% confidence (very likely) level unless otherwise stated. Limited \r\nuse is also made of published analyses that have employed a range \r\nof methodological choices. In each such case the method/metric \r\nis stated."


id: 5f1f30b6189060c73636cf5635b23668
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 14038
content:
"Use is made of paleoclimate, in situ, ground- and satellite-based \r\nremote sensing, and reanalysis data products where applicable \r\n(Section 1.5). All observational products used in the chapter are \r\ndetailed in Annex I, and information on data sources and processing \r\nfor each figure and table can be found in the associated chapter Table \r\n2.SM.1 available as an electronic supplement to the chapter.  Use \r\nof common periods ranging from 56 million years ago through to "


id: b6b20b5ef20bab34d109ab9fc23a2fed
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 29344
content:
"There exist a variety of inevitable and, in some cases, irreducible \r\nuncertainties in performing an assessment of the observational \r\nevidence for climate change. In some instances, a combination of \r\nsources of uncertainty is important. For example, the assessment \r\nof global surface temperature over the instrumental record in "


id: 2e9e20027f13d82c23d823585cf30756
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 5479
content:
"Section  2.3.1.1.3 considers a combination of observational-dataset \r\nand trend-estimate uncertainties. Furthermore, estimates of parametric \r\nuncertainty are often not comprehensive in their consideration of \r\nall possible factors and, when such estimates are constructed in \r\ndistinct manners, there are often significant limitations to their direct \r\ncomparability (Hartmann et al., 2013, their Box 2.1)."


id: b0f236df526181f574af221808071d1a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 28360
content:
"Contributing Authors: Darrell S. Kaufman (United States of America), Kevin D. Burke (United States of America), Samuel Jaccard \r\n(Switzerland), Christopher Jones (United Kingdom), Wolfgang Kiessling (Germany), Daniel J. Lunt (United Kingdom), Olaf Morgenstern \r\n(New Zealand/Germany), John W. Williams (United States of America)"


id: 4ef5af88781a8f1441560b529a9f4b9d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 11176
content:
"Over the long evolution of the Earth's climate system, several periods have been extensively studied as examples of distinct \r\nclimate states. This Cross-Chapter Box places multiple paleoclimate reference periods into the unifying context of Earth's long-term \r\nclimate history, and points to sections in the report with additional information about each period. Other reference periods, including \r\nthose of the industrialized era, are described in Section 1.4.1."


id: fce8ae8749c7b9ff589b322481b577df
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 41858
content:
"The reference periods represent times that were both colder and warmer than present, and periods of rapid climate change, many \r\nwith informative parallels to projected climate (Cross-Chapter Box 2.1, Table 1). They are used to address a wide variety of questions \r\nrelated to natural climate variations in the past (FAQ 1.3). Most of them are used as targets to evaluate the performance of climate \r\nmodels under different climate forcings (Section 3.8.2), while also providing insight into the ocean-atmospheric circulation changes \r\nassociated with various radiative forcings and geographical changes. "


id: db967df6647f2208603cdfc93a4a630
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 35922
content:
"radiative forcing (ERF) performed in Section 7.3. For some SLCFs \r\nwith insufficient spatial or temporal observational coverage, ERFs are \r\nbased on model estimates, but also reported here for completeness \r\nand context. Tabulated global mixing ratios of all well-mixed GHGs \r\nand ERFs from 1750-2019 are provided in Annex III."


id: ab538a1cd0ceb489b93084ea85cd4740
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 27370
content:
"The AR5 assessed solar variability over multiple time scales, concluding \r\nthat total solar irradiance (TSI) multi-millennial fluctuations over the \r\npast 9 kyr were <1 W m-2, but with no assessment of confidence \r\nprovided. For multi-decadal to centennial variability over the last \r\nmillennium, AR5 emphasized reconstructions of TSI that show \r\nlittle change (<0.1%) since the Maunder Minimum (1645-1715) \r\nwhen solar activity was particularly low, again without providing \r\na confidence level. The AR5 further concluded that the best estimate \r\nof radiative forcing due to TSI changes for the period 1750-2011 "


id: 21ee2db8090993eaac68cb7847df950b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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vector_id: 3197
content:
"Recent estimates of TSI and spectral solar irradiance (SSI) for \r\nthe past millennium are based upon updated irradiance models \r\n(e.g., Egorova et al., 2018; C.-J. Wu et al., 2018) and employ updated \r\nand revised direct sunspot observations over the last three centuries \r\n(Clette et al., 2014; Chatzistergos et al., 2017) as well as records of \r\nsunspot numbers reconstructed from cosmogenic isotope data prior \r\nto this (Usoskin et  al., 2016). These reconstructed TSI time series \r\n(Figure  2.2a) feature little variation in TSI averaged over the past \r\nmillennium. The TSI between the Maunder Minimum (1645-1715) \r\nand second half of the 20th century increased by 0.7-2.7 W m-2\r\n(Jungclaus et al., 2017; Egorova et al., 2018; Lean, 2018; C.-J. Wu et al., \r\n2018; Lockwood and Ball, 2020; Yeo et al., 2020). This TSI increase \r\nimplies a change in ERF of 0.09-0.35 W m-2 (Section 7.3.4.4)."


id: a51a20f4fc78935c9f99509452602f3e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 26275
content:
"was 0.05-0.10 W m-2 (medium confidence), and that TSI very likely \r\nchanged by -0.04 [-0.08 to 0.00] W m-2 between 1986 and 2008. \r\nPotential solar influences on climate due to feedbacks arising from \r\ninteractions with galactic cosmic rays are assessed in Section 7.3.4.5. "


id: dd74569dcd6dadc378ef8d93c6761f18
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 36228
content:
"Slow periodic changes in the Earth's orbit around the Sun mainly \r\ncause variations in seasonal and latitudinal receipt of incoming solar \r\nradiation. Precise calculations of orbital variations are available for \r\ntens of millions of years (Berger and Loutre, 1991; Laskar et al., 2011). \r\nThe range of insolation averaged over boreal summer at 65degN was \r\nabout 83 W m-2 during the past million years, and 3.2 W m-2 during \r\nthe past millennium, but there was no substantial effect upon global \r\naverage radiative forcing (0.02 W m-2 during the past millennium)."


id: 9983179f6e9a3298a440be0080baa63a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24236
content:
"Estimation of TSI changes since 1900 (Figure 2.2b) has further \r\nstrengthened, and confirms a small (less than about 0.1  W  m-2) \r\ncontribution to global climate forcing (Section 7.3.4.4). New \r\nreconstructions of TSI over the 20th century (Lean, 2018; C.-J. Wu \r\net  al., 2018) support previous results that the TSI averaged over \r\nthe solar cycle very likely increased during the first seven decades \r\nof the 20th century and decreased thereafter (Figure 2.2b). TSI did \r\nnot change significantly between 1986 and 2019. Improved insights \r\n(Krivova et al., 2006; Yeo et al., 2015, 2017; Coddington et al., 2016) \r\nshow that variability in the 200-400 nm UV range was greater than \r\npreviously assumed. Building on these results, the forcing proposed \r\nby Matthes et  al. (2017) has a 16% stronger contribution to TSI "


id: 8b74ce16495c1b191e579b2213faf02a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21698
content:
"A new reconstruction of solar irradiance extends back 9 kyr based \r\nupon updated cosmogenic isotope datasets and improved models \r\nfor production and deposition of cosmogenic nuclides (Poluianov \r\net al., 2016), and shows that solar activity during the second half of \r\nthe 20th century was in the upper decile of the range. TSI features \r\nmillennial-scale changes with typical magnitudes of 1.5 [1.4 to 2.1] \r\nW m-2 (C.-J. Wu et  al., 2018). Although stronger variations in the \r\ndeeper past cannot be ruled out completely (Egorova et al., 2018; \r\nReinhold et al., 2019), there is no indication of such changes having \r\nhappened over the last 9 kyr."


id: 933f4c99786fbc9ce44fd27e61dd7236
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 23106
content:
"variability in this wavelength range compared to the forcing used in \r\nthe 5th Phase of the Coupled Model Intercomparison Project (CMIP5)."


id: 4352d2a57989b017456a124a9925a419
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 9058
content:
"the previous 24 centuries (back to 2.5 ka), and well within the range \r\nof centennial-scale variability (Toohey and Sigl, 2017)."


id: c8bc670db73faa15d121e4a8d58e7747
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 32635
content:
"To conclude, solar activity since the late 19th century was relatively \r\nhigh but not exceptional in the context of the past 9 kyr (high \r\nconfidence). The associated global mean ERF is in the range of -0.06 \r\nto +0.08 W m-2 (Section 7.3.4.4)."


id: 5ec1c06eb071e3d6c9f5847875294397
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 13961
content:
"To conclude, strong individual volcanic eruptions cause multi-annual \r\nvariations in radiative forcing. However, the average magnitude \r\nand variability of SAOD and its associated volcanic aerosol forcing \r\nsince 1900 are not unusual in the context of at least the past 2.5 kyr \r\n(medium confidence)."


id: a55ae783e4c9c1e155cdb6880af84177
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 26320
content:
"SAOD averaged over the period 950-1250 CE (0.012) was lower \r\nthan for the period 1450-1850 CE (0.017) and similar to the \r\nperiod  1850-1900 (0.011). Uncertainties associated with these \r\ninter-period differences are not well quantified but have little effect \r\nbecause the uncertainties are mainly systematic throughout the record. \r\nOver the past 100 years, SAOD averaged 14% lower than the mean of "


id: 84ec256d93bdc70cc614937f5d80297d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 20524
content:
"Isotopes from continental and marine sediments using improved \r\nanalytical techniques and sampling resolution have reinforced the \r\nunderstanding of long-term changes in atmospheric CO2 during the \r\npast 450 Myr (Table 2.1 and Figure 2.3). In particular, for the last \r\n60 Myr, sampling resolution and accuracy of the boron isotope proxy "


id: 3b976d5d5165491b319f9f9cb505200a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 7669
content:
"of the terrestrial proxies, preference here is given to the marine based \r\nproxies (and boron in particular) where possible. "


id: adcebc046e272c776d5b2e94052a0ba
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 27822
content:
"a\r\n Centennial rate of change estimated by extrapolation of data from a shorter time period. The values (x to y) represent very likely ranges (90% CIs).\r\nb\r\n Data uncertainty is not estimated. "


id: 9694260deb92aee00502706a733dda47
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 23695
content:
"Following the MPWP, the atmospheric CO2 mixing ratio generally \r\ndecreased at a rate of about 30 ppm Myr -1. It is very likely that CO2\r\nlevels as high as the present were not experienced in the last 2 Myr \r\n(Honisch et al., 2009; Bartoli et al., 2011; Martinez-Boti et al., 2015a; \r\nChalk et al., 2017; Dyez et al., 2018; Da et al., 2019; Stoll et al., 2019). \r\nRelated to the shift of glacial-interglacial cycle frequency from 40 to \r\n100 kyr at 0.8-1.2 Ma, there was a decrease of glacial-period CO2\r\n(Chalk et  al., 2017; Dyez et  al., 2018). These boron isotope-based \r\nCO2  results agree with available records based on ancient ice \r\nexposed near the surface of the AIS (Yan et  al., 2019), however, \r\ndirect comparison is limited due to a lack of ancient ice cores with \r\nsufficiently continuous stratigraphy (Higgins et al., 2015; Brook and \r\nBuizert, 2018)."


id: c161e50d686b110bb3a3f900c7c46add
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 31327
content:
"To conclude, there is high confidence that average EECO and MPWP \r\n(KM5c) CO2 concentrations were higher than those preceding \r\nindustrialization at 1150-2500 ppm and 360-420 ppm, respectively. \r\nAlthough there is some uncertainty due to the non-continuous nature \r\nof marine sediment records, the last time atmospheric CO2 mixing \r\nratio was as high as present was very likely more than 2 Ma."


id: e4a6de52864c577a2656ac1048c99a04
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 37510
content:
"Since AR5, the number of ice cores for the last 800 kyr has increased \r\nand their temporal resolution has improved (Figure 2.4), especially for \r\nthe last 60 kyr and when combined with analyses of firn air, leading \r\nto improved quantification of greenhouse gas concentrations prior to \r\nthe mid-20th century."


id: 2f79b7116e3e3342efd0d61e3a24a019
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 5614
content:
"In this section and for calculation of ERF, surface global averages are \r\ndetermined from measurements representative of the well-mixed lower \r\ntroposphere. Global averages that include sites subject to significant \r\nanthropogenic activities or influenced by strong regional biospheric \r\nemissions are typically larger than those from remote sites, and require \r\nweighting accordingly (Table 2.2). This section focusses on global mean \r\nmixing ratios estimated from networks with global spatial coverage, \r\nand updated from the CMIP6 historical dataset (Meinshausen et al., \r\n2017) for periods prior to the existence of global networks."


id: cffcbf6eff2e112e03dd1c6965462a1
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 33944
content:
"The globally averaged surface mixing ratio of CH4 in 2019 was \r\n1866.3 +- 3.3 ppb, which is 3.5% higher than 2011, while observed \r\nincreases from various networks range from 3.3-3.9% (Table 2.2 \r\nand Figure 2.5b). There are marked growth rate changes over the \r\nperiod of direct observations, with a decreasing rate from the late\u00021970s through the late-1990s, very little change in concentrations \r\nfrom 1999-2006, and resumed increases since 2006. Atmospheric \r\nCH4 fluctuations result from complex variations of sources and sinks. \r\nA detailed discussion of recent methane trends and our understanding \r\nof their causes is presented in Cross-Chapter Box 5.2."


id: c779829db361eca0f28283f90f20d2c5
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 32406
content:
"The AR5 reported 324.2 +- 0.1 ppb for global surface annual mean \r\nN2O in 2011; since then, it has increased by 2.4% to 332.1 +- 0.4 ppb \r\nin 2019. Independent measurement networks agree well for both \r\nthe global mean mixing ratio and relative change since 2011 \r\n(Table 2.2). Over 1995-2011, N2O increased at an average rate of \r\n0.79 +- 0.05 ppb yr -1. The growth rate has been higher in recent years, \r\namounting to 0.96 +- 0.05 ppb yr -1 from 2012 to 2019 (Figure 2.5c \r\nand Section 5.2.3.5)."


id: 761d191c5776174e626236c4ee40c332
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 18008
content:
"In summary, CO2 has fluctuated by at least 2000 ppm over the last \r\n450 Myr (medium confidence). The last time CO2 concentrations were \r\nsimilar to the present-day was over 2 Ma (high confidence). Further, \r\nit is certain that WMGHG mixing ratios prior to industrialization were \r\nlower than present-day levels and the growth rates of the WMGHGs \r\nfrom 1850 are unprecedented on centennial timescales in at least \r\nthe last 800 kyr. During the glacial-interglacial climate cycles over \r\nthe last 800 kyr, the concentration variations of the WMGHG were \r\n50-100 ppm for CO2, 210-430 ppb for CH4 and 60-90 ppb for N2O. \r\nBetween 1750-2019 mixing ratios increased by 131.6 +- 2.9 ppm \r\n(47%), 1137 +- 10 ppb (156%), and 62 +- 6 ppb (23%), for CO2, \r\nCH4, and N2O, respectively (very high confidence). Since 2011 (AR5) \r\nmixing ratios of CO2, CH4, and N2O have further increased by 19 ppm, "


id: 7e075e8a21c61b0a96a5c91599003cec
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 19350
content:
"63 ppb, and 7.7 ppb, reaching in 2019 levels of 409.9 (+- 0.4) ppm, \r\n1866.3 (+-  3.3)  ppb, and 332.1 (+- 0.4) ppb, respectively. By 2019, \r\nthe combined ERF (relative to 1750) of CO2, CH4 and N2O was \r\n2.9 +- 0.5 W m-2 (Table 2.2; Section 7.3.2)."


id: 76b7f4e0aaf777c2cd6a72e5afa32ea1
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 18100
content:
"This category includes ozone depleting substances (ODS), their \r\nreplacements, and gases used industrially or produced as by-products. \r\nSome have natural sources (Section 6.2.2.4). The AR5 reported \r\nthat atmospheric abundances of chlorofluorocarbons (CFCs) were \r\ndecreasing in response to controls on production and consumption \r\nmandated by the Montreal Protocol on Substances that Deplete \r\nthe Ozone Layer and its amendments. In contrast, abundances of \r\nboth hydrochlorofluorocarbons (HCFCs, replacements for CFCs) and \r\nhydrofluorocarbons (HFCs, replacements for HCFCs) were increasing. \r\nAtmospheric abundances of perfluorocarbons (PFCs), SF6, and NF3\r\nwere also increasing."


id: 758262c47459b7879778fe97e9feb5ae
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 17901
content:
"Further details on ODS and other minor greenhouse gases can be found \r\nin the Scientific Assessment of Ozone Depletion: 2018 (Engel et al., 2018; \r\nMontzka et al., 2018b). Updated mixing ratios of the most radiatively \r\nimportant gases (ERF >0.001 W m-2) are reported in Table  2.2, and \r\nadditional gases (ERF <0.001 W m-2) are shown in Annex III."


id: 5af9db4eab78cfb6385771cd45ff5575
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 13258
content:
"Atmospheric abundances of most CFCs have continued to decline since \r\n2011 (AR5). The globally-averaged abundance of CFC-12 decreased \r\nby 25 ppt (4.8%) from 2011 to 2019, while CFC-11 decreased by \r\nabout 11 ppt (4.7%) over the same period (Table 2.2 and Figure 2.6). \r\nAtmospheric abundances of some minor CFCs (CFC-13, CFC-115, \r\nCFC-113a) have increased since 2011 (Annex III), possibly related to \r\nuse of HFCs (Laube et al., 2014). Overall, as of 2019 the ERF from CFCs \r\nhas declined by 9 +- 0.5% from its maximum in 2000, and 4.7 +- 0.6% \r\nsince 2011 (Table 7.5)."


id: 3443751dc600b10e39f9526f212d5eba
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 6433
content:
"and AGAGE networks. Reasons for the discrepancy are presently \r\nunverified, but could be related to differences in sampling locations \r\nin the networks (Simpson et al., 2012). Emissions of HCFC-22, derived \r\nfrom atmospheric data, have remained relatively stable since 2012, \r\nwhile those of HCFC-141b and HCFC-142b have declined (Engel \r\net  al., 2018). Minor HCFCs, HCFC-133a and HCFC-31, have been \r\ndetected in the atmosphere (currently less than 1 ppt) and may be \r\nunintentional by-products of HFC production (Engel et al., 2018)."


id: 499c163156f94ca208a5938680bbdc0c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10178
content:
"While global reporting indicated that CFC-11 production had \r\nessentially ceased by 2010, and the atmospheric abundance of CFC-11 \r\nis still decreasing, emissions inferred from atmospheric observations \r\nbegan increasing in 2013-2014 and remained elevated for 5-6 years, \r\nsuggesting renewed and unreported production (Montzka et  al., \r\n2018a, 2021; Rigby et al., 2019; Park et al., 2021). The global lifetimes \r\nof several ozone-depleting substances have been updated (SPARC, \r\n2013), in particular for CFC-11 from 45 to 52 years. "


id: e64cfa893b122c50c307ee03cb28950f
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 37822
content:
"The atmospheric abundances of the major HCFCs (HCFC-22, \r\nHCFC-141b, HCFC-142b), primarily used in refrigeration and foam \r\nblowing, are increasing, but rates of increase have slowed in recent \r\nyears (Figure 2.6). Global mean mixing ratios (Table 2.2) showed \r\ngood concordance at the time of AR5 for the period 2005-2011. For \r\nthe period 2011-2019, the UCI network detected larger increases \r\nin HCFC-22, HCFC-141b, and HCFC-142b compared to the NOAA "


id: 47000a0e78d11d4429fd14245bf83665
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 9693
content:
"Hydrofluorocarbons (HFCs) are replacements for CFCs and HCFCs. \r\nThe atmospheric abundances of many HFCs increased between 2011 \r\nand 2019. HFC-134a (mobile air conditioning, foam blowing, and \r\ndomestic refrigerators) increased by 71 % from 63 ppt in 2011 to \r\n107.6 ppt in 2019 (Table 2.2). The UCI network detected a slightly \r\nsmaller relative increase (53%). HFC-23, which is emitted as a by\u0002product of HCFC-22 production, increased by 8.4 ppt (35%) over "


id: 65b400b88b39ab6b9ffa3130c9389784
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 15157
content:
"2011-2019. HFC-32 used as a substitute for HCFC-22, increased at \r\nleast by 300%, and HFC-143a and HFC-125 showed increases \r\nof 100% and 187%, respectively. While the ERF of HFC-245fa is \r\ncurrently <0.001 W m-2, its atmospheric abundance doubled since \r\n2011 to 3.1 ppt in 2019 (Annex III). In contrast, HFC-152a is showing \r\nsigns of stable (steady-state) abundance. "


id: c089f7077de71050634a563edebf39c4
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 31170
content:
"The AR5 assessed low confidence in stratospheric water vapour (SWV) \r\ntrends based on substantial seasonal and interannual variability in \r\nsatellite data from 1992 to 2011. The 1980-2010 record of balloon\u0002borne frost point hygrometer measurements over Boulder, Colorado \r\n(40degN), showed an average net increase of 1.0 +- 0.2 ppm (27 +- 6%) \r\nin the 16-26 km layer."


id: 11f0975e78a9c3fd2b45bfdc5fe28f64
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 344
content:
"Since AR5, bias-adjusted spatially comprehensive SWV measurements \r\nby different satellite sensors were merged to form continuous records \r\n(Hegglin et al., 2014; Froidevaux et al., 2015; Davis et al., 2016). These \r\nindicate no net global increase of SWV in the lower stratosphere since \r\nthe late 1980s. Hegglin et al. (2014) reported a latitudinal dependence \r\nof SWV trends and suggested that the upward trend over Boulder \r\nshould not be considered representative of the global stratosphere, \r\nwhile Lossow et al. (2018) showed insignificant differences between \r\nSWV trends at Boulder and those for the 35-45degN zonal mean from \r\n1980 to 2010 using model simulations and satellite observations. "


id: 24a9f92ffe37d971fb3171ef031fccc1
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 3645
content:
"The global abundance of CCl4 continues to decline, down about \r\n9.6% since 2011. Following a revision of the global lifetime from \r\n26 to 32  years, and discovery of previously unknown sources \r\n(e.g.,  biproducts of industrial emissions), knowledge of the CCl4\r\nbudget has improved. There is now better agreement between top\u0002down emissions estimates (based on atmospheric measurements) \r\nand industry-based estimates (Engel et al., 2018). Halon-1211, mainly \r\nused for fire suppression, is also declining, and its ERF dropped below \r\n0.001 W m-2 in 2019. While CH2Cl2 has a short atmospheric lifetime \r\n(6 months), and is not well-mixed, its abundance is increasing and its \r\nERF is approaching 0.001 W m-2."


id: 79c566fb7fc6de0cda24ae7b736582f
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 18630
content:
"Perfluorocarbons CF4 and C2F6, which have exceedingly long global \r\nlifetimes, showed modest increases from 2011 to 2019. CF4, which \r\nhas both natural and anthropogenic sources, increased 8.2% to \r\n85.5 ppt, and C2F6 increased 16.3% to 4.85 ppt. c-C4F8, which is used \r\nin the electronics industry and may also be generated during the \r\nproduction of polytetrafluoroethylene (PTFE, also known as 'Teflon') \r\nand other fluoropolymers (Muhle et al., 2019), has increased 34% \r\nsince 2011 to 1.75 ppt, although its ERF remains below 0.001 W m-2. \r\nOther PFCs, present at mixing ratios <1 ppt, have also been quantified \r\n(Droste et al., 2020; see Annex III)."


id: 6d27864e750066799fe49480e12fad86
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 16483
content:
"In summary, in situ measurements at a single mid-latitude location \r\nindicate about a 25% net increase in stratospheric water vapour \r\nsince 1980, while merged satellite data records since the late 1980s \r\nsuggest little net change. Recent studies of dynamical influences \r\non SWV have highlighted their substantial roles in driving large \r\ninterannual variability that complicates trend detection. There \r\nthus continues to be low confidence in trends of SWV over the \r\ninstrumental period. Disregarding dynamic influences on SWV, an \r\nERF of 0.05 +-  0.05 W m-2 is estimated for SWV produced by CH4\r\noxidation (Section 7.3.2.6), unchanged from AR5."


id: ffecfa53575554133ae3eb073cc03db1
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 42421
content:
"In summary, by 2019 the ERF of halogenated GHGs had increased \r\nby 3.5% since 2011, reflecting predominantly a decrease in \r\nthe atmospheric mixing ratios of CFCs and an increase in their \r\nreplacements. However, average annual ERF growth rates associated \r\nwith halogenated gases since 2011 are a factor of seven lower than \r\nin the 1970s and 1980s. Direct radiative forcings from CFCs, HCFCs, \r\nHFCs, and other halogenated greenhouse gases were 0.28, 0.06, \r\n0.04, and 0.03 W  m-2 respectively, totalling 0.41 +- 0.07 W m-2 in \r\n2019 (see Table 7.5). "


id: d2666c0d028bdab9c4f623e46b4ef08
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 34371
content:
"that as much as 40% of the long-term ozone loss occurred between \r\n1960 and 1980 (Shepherd et  al., 2014), lowering the 1964-1980 \r\nbaseline values by about 1% (outside the polar regions), a value \r\nclose to observational uncertainties. The world's longest record of \r\ntotal ozone measurements from Arosa, Switzerland, initiated in 1926, \r\ndoes not show any substantial long-term changes before about 1980 \r\n(Staehelin et al., 2018). "


id: 9c65a714075dc9723d1ea79168444f5f
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24767
content:
"The AR5 assessed that it was certain that global stratospheric ozone \r\nfrom the mid-1990s to 2011 was nearly constant and about 3.5% \r\nlower than in the reference period 1964-1980. Most of the declines \r\noccurred prior to the mid-1990s. "


id: 5a53c3a7478bdcdf97bbd31360d0cc19
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 13143
content:
"Global annual mean total ozone (Figure 2.7) significantly declined \r\nby about 3.5% during the 1980s and the early 1990s and by 2.5% \r\nover 60degS-60degN (near-global). Then, during 2000-2017, both \r\nglobal and near-global concentrations increased slightly, but not \r\nsignificantly, all in line with production and consumption limits of \r\nODS regulated under the Montreal Protocol and its amendments. \r\nNear-global 2014-2017 mean total ozone is about 2.2% below the \r\npre-ozone depletion 1964-1980 average (Braesicke et  al., 2018). \r\nAt  southern and northern mid-latitudes, declines are 5.5% and \r\n3.0% compared to the 1964-1980 average respectively. Total ozone \r\nremained practically unchanged in the tropics (Braesicke et al., 2018). \r\nEmission of ODS started before 1980 and some estimates suggest "


id: d0c224b0d06cf22fbe190c9cef24e685
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 34079
content:
"ERF depends strongly on the altitude of ozone changes. Two \r\nstratospheric regions are mainly responsible for long-term changes \r\noutside the polar regions. In the upper stratosphere (35-45 km), \r\nthere was a strong decline (about 10%) from the start of observations \r\nin 1979 up to the mid-1990s and a subsequent increase by about \r\n4% to present (SPARC/IO3C/GAW, 2019). In the lower stratosphere \r\n(20-25 km), there also was a statistically significant decline (7-8%) \r\nup to the mid-1990s, followed by stabilization or a small further \r\ndecline (Ball et al., 2018, 2019), although the natural variability is \r\ntoo strong to make a conclusive statement (Chipperfield et al., 2018)."


id: 9d85a3b260560f72c48cdcfcb059718a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24953
content:
"the SH tropics and mid-latitudes since the mid-20th century, with \r\ntropospheric ozone exhibiting little change across Antarctica (Tarasick \r\net  al., 2019; Cooper et  al., 2020). Based on reliable UV absorption \r\nmeasurements at remote locations (surface and lower troposphere), \r\nozone trends since the mid-1990s varied spatially at northern mid\u0002latitudes, but increased in the northern tropics (2-17%; 1-6 ppbv \r\nper decade; (Cooper et al., 2020; Gaudel et al., 2020). Across the SH \r\nthese more recent observations are too limited to determine zonal \r\ntrends (e.g., tropics, mid-latitudes, high latitudes)."


id: 61071394d5cf7f6d100aad33d133221a
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 14364
content:
"The strongest ozone loss in the stratosphere continues to occur in \r\naustral spring over Antarctica (ozone hole) with emergent signs of \r\nrecovery after 2000 (Langematz et al., 2018). Interannual variability \r\nin polar stratospheric ozone is driven by large scale winds and \r\ntemperatures, and, to a lesser extent, by the stratospheric aerosol \r\nloading and the solar cycle. This variability is particularly large in the \r\nArctic, where the largest depletion events, comparable to a typical \r\nevent in the Antarctic, occurred in 2011 (Manney et  al., 2011; \r\nLangematz et  al., 2018) and again in 2020 (Manney et  al., 2020; \r\nGrooss and Muller, 2021). Further details on trends and ERF can be \r\nfound in Sections 6.3.2 and 7.3.2.5. "


id: 894f94142fe26f34e1103e7197b1a013
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21331
content:
"In summary, compared to the 1964-1980 average, stratospheric ozone \r\ncolumns outside polar regions (60degS-60degN) declined by about 2.5% \r\nover 1980-1995, and stabilized after 2000, with 2.2% lower values in \r\n2014-2017. Large ozone depletions continue to appear in spring in \r\nthe Antarctic and, in particularly cold years, also in the Arctic. Model\u0002based estimates disagree on the sign of the ERF due to stratospheric \r\nozone changes, but agree that it is much smaller in magnitude than \r\nthat due to tropospheric ozone changes (Section 7.3.2.5)."


id: 1b50d4f04519dbe967aecb6a7ed0c782
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 1984
content:
"The AR5 assessed medium confidence in large-scale increases of \r\ntropospheric ozone at rural surface sites across the NH (1970-2010), \r\nand in a doubling of European surface ozone during the 20th \r\ncentury, with the increases of surface ozone in the SH being of \r\nlow confidence. Surface ozone likely increased in East Asia, but \r\nlevelled off or decreased in the eastern USA and western Europe. \r\nFree tropospheric trends (1971-2010) from ozonesondes and aircraft \r\nshowed positive trends in most, but not all, assessed regions, and \r\nfor most seasons and altitudes. This section focuses on large scale \r\nozone changes; chemical and physical processes and regional \r\nchanges in tropospheric ozone are assessed in Section 6.3.2.1 and \r\nSection 7.3.2.5 assesses radiative forcing."


id: c4f4520bff78950466a49674e238a65
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 31958
content:
"In summary, limited available isotopic evidence constrains the \r\nglobal tropospheric ozone increase to less than 40% between 1850 \r\nand 2005 (low confidence). Based on sparse historical surface/low \r\naltitude data tropospheric ozone has increased since the mid-20th \r\ncentury by 30-70% across the NH (medium confidence). Surface/low \r\naltitude ozone trends since the mid-1990s are variable at northern \r\nmid-latitudes, but positive in the tropics [2 to 17% per decade] \r\n(high confidence). Since the mid-1990s, free tropospheric ozone \r\nhas increased by 2-7% per decade in most regions of the northern \r\nmid-latitudes, and 2-12% per decade in the sampled regions of the \r\nnorthern and southern tropics (high confidence). Limited coverage \r\nby surface observations precludes identification of zonal trends in \r\nthe SH, while observations of tropospheric column ozone indicate \r\nincreases of less than 5% per decade at southern mid-latitudes \r\n(medium confidence)."


id: e4cb5af2531036f966f2acbb0d7fb52
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 37534
content:
"loadings for mid- and high-latitude ocean of both hemispheres \r\n(Lamy et al., 2014; Martinez-Garcia et al., 2014; Serno et al., 2015). \r\nImproved quantification of changes in dust deposition from North \r\nAfrica and North Atlantic sediment records confirms dust deposition \r\nrates lower by a factor 2-5 during the African Humid Period (10-5 ka) \r\ncompared to the late Holocene (McGee et  al., 2013; Albani et  al., \r\n2015; Middleton et al., 2018; Palchan and Torfstein, 2019). During the \r\nHolocene, biogenic emissions and volcanic activity drove significant \r\nvariability (up to one order of magnitude) in sulphate concentrations \r\n(Schupbach et al., 2018). "


id: 12e8d52b17dd458c7823f8ae880262fb
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 531
content:
"The AR5 assessed large-scale aerosol optical depth (AOD) trends \r\nover 2000-2009, concluding that there was low confidence in \r\na  global trend, but that AOD very likely decreased from 1990 \r\nonwards over Europe and the eastern USA, and increased since 2000 \r\nover eastern and southern Asia. The ERF associated with aerosol-\r\nradiation interactions for 2011 (relative to 1750) was estimated to \r\nbe -0.45  +-  0.5 W m-2 and of aerosol-cloud interaction estimated \r\nas -0.45 [-1.2 to 0.0] W m-2. Aerosol ERF uncertainty was assessed \r\nas the largest contributor to the overall ERF uncertainty since 1750. "


id: 8b4d03808f4ceeb9579efed7fac226ab
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21669
content:
"Ice cores allow for estimation of multi-centennial trends in mid- and \r\nhigh-latitude aerosol deposition, including those for sulphate \r\nand black carbon (Figure 2.9a,b). Sulphate in ice cores increased \r\nby a factor of 8 from the end of the 19th century to the 1970s in \r\ncontinental Europe, by a factor of 4 from the 1940s to the 1970s \r\nin Russia, and by a factor of 3 from the end of the 19th century to \r\n1950 in the Arctic (Svalbard). In all regions studied, concentrations \r\nhave declined by about a factor of 2 following their peak (around \r\n1970 in Europe and Russia, and 1950 in the Arctic). Strong increases \r\nof black carbon (BC) were observed in the 20th century over Europe, \r\nRussia, Greenland (primarily originating from emissions from North \r\nAmerica), and in the Arctic (Svalbard). South America exhibits a small \r\npositive trend (Figure 2.9). BC concentrations in various Antarctic ice \r\ncores were below 1 ng g-1 without a clear trend. "


id: e4f3700463520031bfe201dd49e6d28d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 37574
content:
"This section assesses the observed large-scale temporal evolution \r\nof tropospheric aerosols. Aerosol-related processes, chemical and \r\nphysical properties, and links to air quality, are assessed in Chapter 6. \r\nAn in-depth assessment of aerosol interactions with radiation and \r\nclouds is provided in Section 7.3.3."


id: 9edc2a66520543cd3288fa7777743b3d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 25175
content:
"Aerosol proxy records of improved temporal resolution and quality \r\nare now available (Kylander et al., 2016; Stevens et al., 2016, 2018; \r\nJacobel et al., 2017; Dornelas et al., 2018; Middleton et al., 2018), \r\nwhich further advance synthesis of new global compilations of \r\naerosol loadings (Lambert et al., 2015; Albani et al., 2016). Estimates \r\nof the glacial/interglacial ratio in global dust deposition are within \r\nthe range of 2-4 (Albani et  al., 2015; Lambert et  al., 2015). New \r\nreconstructions indicate a ratio of 3-5 for the glacial/interglacial "


id: 4051ce8b3240f64b7f4879ad4f3fb40e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 8509
content:
"Satellite-derived trends are further supported by in situ regional surface \r\nconcentration measurements, operational since the 1980s (sulphate) \r\nand 1990s (PM2.5) from a global compilation (Collaud Coen et al., \r\n2020) of networks over Europe (Stjern et al., 2011), North America \r\n(Jongeward et  al., 2016), and China (Zheng et  al., 2018). Collaud \r\nCoen et al. (2020) report from surface observations across the NH \r\nmid-latitudes that aerosol absorption coefficients decreased since \r\nthe first decade of the 21st century."


id: 98da0aab6fd058d91adfad056fadebba
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24109
content:
"Anthropogenic aerosol is predominantly found in the fraction of \r\nparticles with radii <1 um that comprise the fine-mode AOD (AODf; \r\nFigure 2.9d; Kinne, 2019). A significant decline in AODf of more than \r\n1.5% per year from 2000 to 2019 has occurred over Europe and \r\nNorth America, while there have been positive trends of up to 1.5% \r\nper year over Southern Asia and East Africa. The global-scale trend in \r\nAODf of -0.03% per year (Figure 2.9) is significant. The results are \r\nconsistent with trend estimates from an aerosol reanalysis (Bellouin \r\net al., 2020), and the trends in satellite-derived cloud droplet number \r\nconcentrations are consistent with the aerosol trends (Cherian and \r\nQuaas, 2020). Cloudiness and cloud radiative properties trends \r\nare, however, less conclusive possibly due to their large variability \r\n(Norris  et  al., 2016; Cherian and Quaas, 2020). Further details on \r\naerosol-cloud interactions are assessed in Section 7.3.3.2."


id: 738078cef4bc8d97b30b160a56a36a76
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 17572
content:
"To conclude, atmospheric aerosols sampled by ice cores, influenced \r\nby northern mid-latitude emissions, show positive trends from 1700 \r\nuntil the last quarter of the 20th century and decreases thereafter \r\n(high confidence), but there is low confidence in observations of \r\nsystematic changes in other parts of the world in these periods. \r\nSatellite data and ground-based records indicate that AOD exhibits \r\npredominantly negative trends since 2000 over NH mid-latitudes and \r\nSH continents, but increased over South Asia and East Africa (high \r\nconfidence). A globally deceasing aerosol abundance is thus assessed \r\nwith medium confidence. This implies increasing net positive ERF, \r\nsince the overall negative aerosol ERF has become smaller."


id: dda91c1b8fcc59a24db2641c8081e64c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 36260
content:
"The AR5 assessed that land use change very likely increased the \r\nEarth's albedo with a radiative forcing of -0.15 (+- 0.10) W m-2. \r\nAR5 also assessed that a net cooling of the surface, accounting for \r\nprocesses that are not limited to the albedo, was about as likely as not. \r\nThe SRCCL concluded with medium confidence that the biophysical \r\neffects of land cover change (mainly increased albedo) had a cooling \r\neffect on surface temperatures. The SRCCL also concluded with very \r\nhigh confidence that the biogeochemical effects of land cover change \r\n(i.e., GHG emissions) resulted in a mean annual surface warming."


id: 219125d0ef75585f0fadccaca1fd4164
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 3114
content:
"In summary, biophysical effects from historical changes in land use \r\nhave an overall negative ERF (medium confidence). The best-estimate \r\nERF from the increase in global albedo is -0.15 W m-2 since 1700 \r\nand -0.12 W m-2 since 1850 (medium confidence) (Section 7.3.4.1). \r\nBiophysical effects of land-use change likely resulted in a net \r\nglobal cooling of about 0.1degC since 1750 (medium confidence) \r\n(Section 7.3.5.3)."


id: 42059bda32158dff8ee67753fd20ebb1
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 8816
content:
"The AR5 concluded that changes in climate drivers over the industrial \r\nperiod corresponded to a positive ERF which increased more rapidly \r\nafter 1970 than before. There was very high confidence in the positive \r\nERF due to WMGHG, with CO2 the single largest contributor. The AR5 \r\nconcluded that there was high confidence that aerosols have offset \r\na substantial portion of the WMGHG forcing. "


id: fc69a75cfd9c7978051868c091e86cf4
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 41775
content:
"This section reports the evolution in ERF with respect to 1750 \r\nas assessed in Section 7.3 and relies on the observed changes in \r\nclimate drivers as assessed in Section 2.2 wherever possible, and \r\nmodels otherwise. The ERF is assessed using the methods and details \r\ndescribed in Section 7.3.1 and includes, in addition to the radiative \r\nforcing, the rapid adjustments, especially implied by clouds. The time \r\nseries are shown in Figure 2.10."


id: 491658c5d75a40717b5f66299411d80
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10080
content:
"The impact of historical land-cover change on global climate is \r\nassessed with model simulations that consider multiple climate and \r\nbiophysical processes (e.g.,  changes in albedo, evapotranspiration, \r\nand roughness) and/or biogeochemical processes (e.g.,  changes in \r\natmospheric composition such as carbon release from deforestation). \r\nThe dominant biophysical response to land cover changes is albedo, \r\nwhich is estimated (using a MODIS albedo product and a historical \r\nland-use harmonization product) to have increased gradually prior to \r\nthe mid-19th century and then strongly through the mid-20th century, "


id: 5ab46da664eca6f8666ab0e07653cbb
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 13210
content:
"Increasing TSI (Section 2.2.1) implies a small ERF of less than \r\n0.1 W m-2 between 1900 and 1980. TSI varies over the 11-year solar \r\ncycle with ERF of order +- 0.1 W m-2 in the assessed period. Strong "


id: 96f5be8aa0fa19a23ff981e08ac8f096
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 23752
content:
"volcanic eruptions (Section 2.2.2) with periods of strong negative \r\nERF lasting 2-5 years in duration occurred in the late 19th and early \r\n20th centuries. There followed a relatively quiescent period between \r\nabout 1920 and 1960, and then three strong eruptions in 1963, \r\n1982 and 1991, and only small-to-moderate eruptions thereafter \r\n(Schmidt et al., 2018). "


id: 7e97ed31eb2aa6d62019956e5ea68a06
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 19427
content:
"Among the gaseous short-lived climate forcers (Chapter 6 and \r\nSections 2.2.5 and 7.3; excluding CH4 here), ozone (O3) is the \r\ncomponent with the largest (positive) ERF. Concentrations from \r\ndirect observations have increased since the mid-20th century and, \r\nmostly based on models, this extends to since 1750. Other gaseous \r\nshort-lived climate forcers have small contributions to total ERF."


id: 1e95141dbd37e56f70df0fefee9939f4
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 2586
content:
"The atmospheric concentrations of WMGHGs (Section 2.2.3) have \r\ncontinuously increased since the early 19th century, with CO2\r\ncontributing the largest share of the positive ERF. Compared to \r\nthe last two decades of the 20th century, the growth rate of CO2 in the \r\natmosphere increased in the 21st century, showed strong fluctuations \r\nfor CH4, and was about constant for N2O. Mixing ratios of the most \r\nabundant CFCs declined (Section 2.2.4). Mixing  ratios of HCFCs \r\nincreased, but growth rates are starting to decelerate. Mixing ratios \r\nof HFCs and some other human-made components are increasing \r\n(Section 2.2.4). The ERF for CO2 alone is stronger than for all the other \r\nanthropogenic WMGHGs taken together throughout the industrial "


id: 3beb0ac27e6b2eb41ded1a1d721fc295
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 7736
content:
"The net effect of aerosols (Sections 2.2.6 and 6.4) on the radiation \r\nbudget, including their effect on clouds, and cloud adjustments, as \r\nwell as the deposition of black carbon on snow (Section 7.3.4.3), \r\nwas negative throughout the industrial period (high confidence). \r\nThe net effect strengthened (becoming more negative) over most \r\nof the 20th  century, but more likely than not weakened (becoming \r\nless negative) since the late 20th century. These trends are reflected \r\nin measurements of surface solar radiation (Section 7.2.2.3) and the "


id: 44379f2d39d06864f4ea27e8f4a229cc
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 9239
content:
"Earth's energy imbalance (Section 7.2.2.1). The relative importance \r\nof aerosol forcing compared to other forcing agents has decreased \r\nglobally in the most recent 30 years (medium confidence) and the \r\nreduction of the negative forcing in the 21st century enhances \r\nthe overall positive ERF."


id: 9b6a45312fbd62dcb5e9d076bb456114
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24597
content:
"rapid adjustments and thus there is low confidence in its magnitude. \r\nBiogeochemical feedbacks can be substantial (Section 5.4) and are \r\nnot included in ERF."


id: d850836fa1c365539c2cd9ff471ad58c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 35361
content:
"In conclusion, the net ERF due to all observed changes in climate drivers \r\nis positive, except for short periods (up to a few years in duration) \r\nfollowing moderate to large volcanic eruptions, and has grown in \r\nmagnitude since the late 19th century. The rate of change likely has \r\nincreased in the last 30 years, since CO2 concentrations increased at an \r\nincreasing rate due to growing CO2 emissions (very likely), and since \r\nthe aerosol forcing became less negative (more likely than not). "


id: e189b2a8c327a5c5eeaf7a33a47d459b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 36952
content:
"Land use and land cover changes (Section 2.2.7) over the industrial \r\nperiod introduce a negative radiative forcing by increasing the surface \r\nalbedo. This effect increased since 1750, reaching current values of \r\nabout -0.20 W m-2 (medium confidence). This ERF value is taken from \r\nSection 7.3.4.1 and is different from the assessment in Section 2.2.7 \r\nin that it also includes the effect of irrigation. It also includes uncertain "


id: 724596725fe49cd7fb14df2e33c64d3f
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 17348
content:
"Contributing Authors: Veronika Eyring (Germany), Nathan P. Gillett (Canada), Sergey K. Gulev (Russian Federation), Jochem Marotzke \r\n(Germany), June-Yi Lee (Republic of Korea), Peter W. Thorne (Ireland/United Kingdom)"


id: 8ba825383a522f1b21510aef9621ea0e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21746
content:
"Chapters 2, 3 and 4 assess the current evidence basis for climatic changes, their causes, and their potential future under different \r\npossible emissions pathways using a combination of observations and state-of-the-art Earth system models (ESMs). The assessment in \r\nthese chapters focuses on selected large-scale indicators and modes as defined in this Box. These indicators and modes of variability \r\ntaken together characterize overall changes to the climate system as a whole. "


id: 2e251282f5672471caad26cff801beaa
created_at: 2023-04-19 13:21:32
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"Understanding of large-scale climate variability and change requires knowledge of both the response to forcings and the role of \r\ninternal variability. Many forcings have substantial hemispheric or continental scale variations. Modes of climate variability are \r\ngenerally driven by ocean basin scale processes. The climate system involves process interactions from the micro- to the global-scale \r\nand as such, any threshold for defining 'large-scale' is arbitrary, but, within these chapters on the basis of these considerations \r\nlarge-scale is defined to include ocean basin and continental scales as well as hemispheric and global scales. "


id: 9710c3439373fcf88d0341ff8159867b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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"Key climate indicators should constitute a finite set of distinct variables and/or metrics that may collectively point to important overall \r\nchanges in the climate system that provide a synthesis of climate system evolution and are of broad societal relevance. Key indicators \r\nhave been selected across the atmospheric, oceanic, cryospheric and biospheric domains, with land as a cross-cutting component. These \r\nindicators, and their use across Chapters 2, 3 and 4, as well as the broader report, are summarized in Cross-Chapter Box 2.2, Table 1. \r\nAll selected indicators are Essential Climate Variables as defined by the Global Climate Observing System (Bojinski et al., 2014)."


id: bf9e399808f3987309d93866544a7589
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content:
"Cross-Chapter Box 2.2, Table 1 | Summary of the large-scale indicators used across Chapters 2 through 4 and their principal applications in \r\nremaining chapters. Indicators are sub-divided by Earth-system domain and their inclusion in individual chapters is indicated by a blue dot. The list of additional \r\nchapters is limited to those where the variable is a principal consideration. "


id: 14548cbeed0839cf5c36de75a1083d9f
created_at: 2023-04-19 13:21:32
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content:
"Changes in ice sheets are indicators of the longest-term impacts of climate change and associated with changes in global and \r\nregional sea level. Seasonal snow cover has many implications for mid- to high-latitude regions (albedo, hydrological cycle, etc.) with \r\nimpacts on biospheric components of the system. Changes in sea ice extent, seasonality and thickness have potential impacts for \r\nhemispheric-scale circulation (Cross-Chapter Box 10.1). Changes in glacier mass balance contribute to changes in sea level but also \r\nhave substantial implications for water supply for a substantial proportion of the global population. Finally, changes in permafrost and \r\nthe seasonally thawed active layer have substantial implications in mid- to high-latitudes and have been hypothesized to be important \r\nin potential feedbacks through degassing of WMGHGs as the permafrost thaws."


id: 899d91f3a1630b97ffc070cc84858092
created_at: 2023-04-19 13:21:32
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content:
"Most of the energy imbalance (Box 7.2) in the climate system is taken up by the ocean, resulting in changes in ocean temperature and \r\nheat content. Salinity changes indicate broad-scale hydrological cycle and circulation changes. Global-mean sea-level change is a key \r\nindicator of the impacts of both global warming and changes in global ice volume. Furthermore, it is integral to assessing the global \r\nenergy budget (Cross-Chapter Box 9.1). The oceanic overturning circulation redistributes heat, carbon, oxygen and salinity within the \r\nocean. Declines in ocean pH result from air-sea exchange of carbon dioxide and loss of ocean oxygen results from ocean warming; \r\nboth lead to changes in marine ecosystems."


id: 183a46ad5fd274d010de22150c5d9552
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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content:
"The seasonal cycle of CO2 is an integrated measure of the biogeochemical activity across the global biosphere. Changes in marine \r\nand terrestrial ecosystems can also be observed directly at large scales. For small, free-floating organisms such as phytoplankton, the \r\ndynamics can be rapid in nature, whereas on land slower changes in plant assemblages may occur, with commensurate changes in \r\naltitude and latitude of the tree-line. Lengthening of the growing season and the associated changes in phenology, distribution and \r\nabundance of species would be expected in most of the extratropics. Biospheric indicators and their impacts are assessed in much \r\ngreater detail in WGII Chapters 2 and 3."


id: acfb5d5126b8c67fe10ffd9cc0424b26
created_at: 2023-04-19 13:21:32
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content:
"Defining a selection of modes of variability\r\nMany modes of climate variability affect global, hemispheric or regional climate across a range of timescales. Conversely, their \r\nbehaviour may be influenced by global climate change. Modes were selected for inclusion that: (i) have effects at large spatial scales; \r\nand (ii) have substantial potential to modify interannual to multi-decadal climate. The selected modes are considered in multiple \r\nchapters (Cross-Chapter Box 2.2, Table 2) and are defined in Annex IV."


id: 1478c08693bdc114eb9d9bb17f366cfe
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content:
"Cross-Chapter Box 2.2, Table 2 | Summary of the modes of variability used across Chapters 2 through 4 and their principal applications in \r\nremaining chapters. Inclusion in each of Chapters 2 through 4 is indicated by a blue dot of the relevant table cell. The list of remaining chapters is limited to those \r\nwhere the mode of variability is a principal consideration of that chapter and is not intended to be exhaustive."


id: 9ae4b0d0eecebb393e75a934a31c1b8e
created_at: 2023-04-19 13:21:32
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content:
"For the EECO, new GMST reconstructions fall at the high end of the range \r\nassessed by AR5. These include estimates of 7degC-18degC (90% range; \r\nInglis et al., 2020) and 12degC-18degC (95% range; Zhu et al., 2019) warmer \r\nthan 1850-1900, and 10degC-16degC warmer than 1995-2014 'recent \r\npast' conditions (2 standard error range; Caballero and Huber, 2013). "


id: cc327d227d206924eff4dc67bd11f726
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
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vector_id: 33246
content:
"Together, they indicate that GMST was 10degC-18degC warmer during the \r\nEECO compared with 1850-1900 (medium confidence). "


id: de5fcd6b3a1a4b0efde80915eb2ae054
created_at: 2023-04-19 13:21:32
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content:
"The AR5 did not assess the GMST for the MCO. Reconstructions \r\nbased on data from multiple study sites include estimates of about \r\n4degC (uncertainty range not specified; You et al., 2009) and 5degC-10degC \r\n(2 standard error range; Goldner et al., 2014) warmer than 1850-1900. \r\nTogether, these studies indicate that GMST was 4degC-10degC warmer \r\nduring the MCO (medium confidence)."


id: 9fc9677c34b493600666b2f7deaaceb2
created_at: 2023-04-19 13:21:32
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content:
"For the MPWP, new proxy-based estimates of global sea surface \r\ntemperatures (SST) are about 2.0degC-3.5degC warmer than 1850-1900, \r\ndepending on which proxy types are included in the analysis (Foley \r\nand Dowsett, 2019; McClymont et al., 2020). On the basis of model\u0002derived relationships between land versus sea surface temperatures \r\nunder different climate states (Figure 3.2b), the increase in GMST is \r\nestimated to have been roughly 15% greater than the increase in \r\nglobal SST. Therefore, GMST during the MPWP is estimated to have \r\nbeen 2.5degC-4.0degC warmer than 1850-1900 (medium confidence)."


id: e4e7916ef1165701fd0027190238dc59
created_at: 2023-04-19 13:21:32
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content:
"For the LDT (Cross-Chapter Box 2.1, Figure 1), no new large-scale \r\nstudies have been published since AR5 (Shakun et  al., 2012) to \r\nfurther assess the rate of GMST change during this period of rapid \r\nglobal warming (estimated at 1degC-1.5degC per kyr). The reconstruction \r\nof Shakun et  al. (2012) was based primarily on SST records and \r\ntherefore underrepresents the change in GMST during the LDT. \r\nTemperature over Greenland increased by about ten times that rate \r\nduring the centuries of most rapid warming (Jansen et al., 2020)."


id: a789bbc0b025eb62cdeefad65621bf2e
created_at: 2023-04-19 13:21:32
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content:
"The AR5 did not include an assessment of large-scale temperature \r\nestimates for the MH, although it assigned high confidence to the \r\nlong-term cooling trend over mid- to high-latitudes of the Northern \r\nHemisphere (NH) during the 5 kyr that preceded recent warming. For \r\naverage annual NH temperatures, the period 1983-2012 was assessed \r\nas very likely the warmest 30-year period of the past 800 years (high \r\nconfidence) and likely the warmest 30-year period of the past 1.4 kyr \r\n(medium confidence); the warm multi-decadal periods prior to the \r\n20th century were unsynchronized across regions, in contrast to \r\nthe warming since the mid-20th century (high confidence), although \r\nonly sparse information was available from the SH. "


id: 89e83cfb86f5a6ade08b19ba2d77b30a
created_at: 2023-04-19 13:21:32
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content:
"New GMST reconstructions for the LGM fall near the middle \r\nof AR5's very likely range, which was based on a combination of \r\nproxy reconstructions and model simulations. Two of these new \r\nreconstructions use marine proxies to reconstruct global SST that \r\nwere scaled to GMST based on different assumptions. One indicates \r\nthat GMST was 6.2 [4.5 to 8.1] degC cooler than the late Holocene \r\naverage (Snyder, 2016), and the other, 5.7degC +- 0.8degC (2 SD) cooler \r\nthan the average of the first part of the Holocene (10-5 ka) (Friedrich \r\nand Timmermann, 2020). A third new estimate (Tierney et al., 2020) \r\nuses a much larger compilation of marine proxies along with a data\u0002assimilation procedure, rather than scaling, to reconstruct a GMST of "


id: d770c19b18d859b0c22bbcffa4c4ad69
created_at: 2023-04-19 13:21:32
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content:
"Taking all lines of evidence into account, the GMST averaged over \r\nthe warmest centuries of the current interglacial period (sometime \r\nbetween around 6 and 7 ka) is estimated to have been 0.2degC-1.0degC \r\nhigher than 1850-1900 (medium confidence). It is therefore more \r\nlikely than not that no multi-centennial interval during the post\u0002glacial period was warmer globally than the most recent decade \r\n(which was 1.1degC warmer than 1850-1900; Section 2.3.1.1.3); the LIG \r\n(129-116 ka) is the next most recent candidate for a period of higher \r\nglobal temperature. Zonally averaged mean annual temperature \r\nreconstructions (Routson et al., 2019) indicate that MH warmth was \r\nmost pronounced north of 30degN latitude, and that GMST subsequently \r\ndecreased in general, albeit with multi-century variability, with greater \r\ncooling in the NH than in the SH (Kaufman et al., 2020a)."


id: 6edb0c0b6c66a0f770b11775b9c5c850
created_at: 2023-04-19 13:21:32
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content:
"The temperature history of the last millennium and the methods \r\nused to reconstruct it have been studied extensively, both prior \r\nto and following AR5, as summarized recently by Smerdon and \r\nPollack (2016) and Christiansen and Ljungqvist (2017). New regional \r\n(e.g., Shi et al., 2015; Stenni et al., 2017; Werner et al., 2018), global \r\nocean (McGregor et  al., 2015), quasi-hemispheric (Neukom et  al., \r\n2014; Schneider et  al., 2015; Anchukaitis et  al., 2017), and global \r\n(Tardif et al., 2019) temperature reconstructions, and new regional "


id: ecb11c99ef73b313417cffd0ea77b232
created_at: 2023-04-19 13:21:32
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content:
"To conclude, following approximately 6 ka, GMST generally decreased, \r\nculminating in the coldest multi-century interval of the post-glacial \r\nperiod (since 8 ka), which occurred between around 1450 and 1850 \r\n(high confidence). This multi-millennial cooling trend was reversed in \r\nthe mid-19th century. Since around 1950, GMST has increased at an \r\nobserved rate unprecedented for any 50-year period in at least the \r\nlast 2000 years (high confidence)."


id: 4d722196e0f8553a298c192617a6a98
created_at: 2023-04-19 13:21:32
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content:
"Contributing Authors:  Peter W. Thorne (Ireland/United Kingdom), Blair Trewin (Australia), Richard P. Allan (United Kingdom), \r\nRichard Betts (United Kingdom), Lea Beusch (Switzerland), Chris Fairall (United States of America), Piers Forster (United Kingdom), \r\nBaylor Fox-Kemper (United States of America), Jan S. Fuglestvedt (Norway), John C. Fyfe (Canada), Nathan P. Gillett (Canada), \r\nEd Hawkins (United Kingdom), Christopher Jones (United Kingdom), Elizabeth Kent (United Kingdom), Svitlana Krakovska (Ukraine), \r\nElmar Kriegler (Germany), Jochem Marotzke (Germany), H. Damon Matthews (Canada), Thorsten Mauritsen (Germany/Denmark), Anna \r\nPirani (Italy), Joeri Rogelj (United Kingdom, Austria/Belgium), Steven K. Rose (United States of America), Bjorn H. Samset (Norway), \r\nSonia I. Seneviratne (Switzerland), Claudia Tebaldi (United States of America), Andrew Turner (United Kingdom), Russell S. Vose (United \r\nStates of America), Rachel Warren (United Kingdom) "


id: 5547524fa553b470d74b718f02c93a68
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content:
"This Cross-Chapter Box presents the AR6 WGI assessment of observed global warming and describes improvements and updates since \r\nAR5 and subsequent Special Reports. The revised estimates result from: the availability of new and revised observational datasets; the \r\noccurrence of recent record warm years; and the evaluation of the two primary metrics used to estimate global warming in past IPCC \r\nreports: 'Global mean surface temperature' (GMST) and 'Global surface air temperature' (GSAT). Implications for threshold crossing \r\ntimes, remaining carbon budgets and impacts assessments across AR6 WGs are discussed. "


id: 4547359a341a395db4fef7b11f7182e2
created_at: 2023-04-19 13:21:32
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"Since AR5, all major datasets used for assessing observed temperature change based upon GMST have been updated and improved \r\n(Section 2.3.1.1.3). A number of new products have also become available, including new datasets (e.g., Berkeley Earth, Rohde and \r\nHausfather, 2020) and new interpolations based on existing datasets (e.g., Cowtan and Way, 2014 and Kadow et al., 2020). These \r\nvarious estimates are not fully independent. "


id: 244b0d9fcc408f18d0fc06e85775fd25
created_at: 2023-04-19 13:21:32
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content:
"Overall, dataset innovations and the availability of new datasets have led to an assessment of increased GMST change relative to the \r\ndirectly equivalent estimates reported in AR5 (Cross-Chapter Box 2.3, Table 1 and Figure 1)."


id: 4418535e02d6dfaa7db79b56ac995605
created_at: 2023-04-19 13:21:32
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content:
"Observed changes in global mean temperature since the pre-industrial era\r\nAR5 used 1850-1900 as an approximate pre-industrial baseline for global temperature change, whilst using an earlier pre-industrial \r\nbaseline of 1750 for radiative forcings. Cross-Chapter Box 1.2 assesses that there was an observed GMST change from the period \r\naround 1750 to 1850-1900 of around 0.1degC (likely range -0.1 to +0.3degC, medium confidence). This additional global temperature \r\nchange before 1850-1900 is not included when making AR6 assessments on global warming to date, global temperature threshold \r\ncrossing times, or remaining carbon budgets to ensure consistency with previous ARs."


id: e090ea2dbc6522e502f388b31701557d
created_at: 2023-04-19 13:21:32
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"A well-understood physical constraint on the vertical gradient between the air and sea surface temperature is that it is approximately \r\nproportional to the turbulent sensible heat flux in the atmospheric surface layer (Chor et al., 2020). Similarly, the latent heat flux scales \r\nwith the vertical humidity gradient and, in the global mean and in most oceanic regions, the latent heat flux is substantially larger than \r\nthe sensible heat flux (Sections 7.2.1 and 9.2.1.3). If GSAT were to warm faster than GMST, the sensible surface heat flux would respond \r\nso as to reduce this difference. However, it is the sum of the sensible, latent, and radiative heat fluxes that controls GMST, so the sensible"


id: a3a9dd7c749dec6a2a66e9f7de0ce15a
created_at: 2023-04-19 13:21:32
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"Overall, with medium evidence and low agreement, available observational products suggest that NMAT is warming less than SST \r\nby up to 15%. Given that these ocean observations cover roughly two thirds of the globe, this implies that GMST is warming up to at \r\nmost 10% faster than GSAT. Substantial uncertainty remains and the effect is highly sensitive to the choice of both time period and \r\nchoice of NMAT and SST observational products to compare. Observed NMAT warming faster than observed SST cannot be precluded."


id: ca3df30b3c1dff736b919fcc9016912a
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content:
"Marine boundary layer behaviour and parameterizations in all CMIP models are based upon Monin-Obukhov similarity theory \r\n(e.g.,  Businger et  al., 1971), which informs assumptions around gradients in the near-surface boundary layer dependent upon \r\ntemperature, wind speed and humidity. This leaves open the possibility of a common model bias, while Druzhinin et al. (2019) also \r\npoint to departures of temperature profiles from theoretical predictions under certain conditions. There remain inadequacies in \r\nunderstanding and modelling of key processes (Edwards et al., 2020), and biases in the representation of the absolute SST-MAT \r\ndifference have been identified in climate models and reanalyses (Gainusa-Bogdan et al., 2015; Zhou et al., 2020)."


id: 21211db73e85d52761255dbf8fb904fe
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"Simmons et al. (2017) found that in JRA-55 and ERA-Interim (following an adjustment to account for an apparent discontinuity), GSAT \r\nincreased 2-4% faster than GMST over the period 1979-2016. In atmospheric reanalyses, SST is given as a lower boundary condition \r\nfrom an observed globally interpolated product (such as HadISST; Rayner et al., 2003) whereas the air temperature is reliant upon \r\nmodel parameterizations and assimilated observations that do not include MAT observations (Simmons et al., 2017), thereby limiting \r\ntheir capability to constrain differences in GMST and GSAT trends. Furthermore, it is unclear what the lack of dynamic coupling at the \r\nocean-atmosphere interface might imply for the representativeness of reanalysis-based estimates. "


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content:
"Cross Chapter Box 2.3, Table 1 | Summary of key observationally based global warming estimates (in degC) to various reference periods in the \r\npresent report and selected prior reports (AR5 WGI and SR1.5) and their principal applications (see Section 1.4.1 for further information on \r\nreference periods). Further details on data sources and processing are available in the chapter data table (Table 2.SM.1)."


id: de56b73ef165b7431ce5f882f8ef410
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"a\r\n As the uncertainty in the relationship between GMST and GSAT changes is independent of the uncertainty in the assessed change in GMST, these uncertainties are \r\ncombined in quadrature."


id: 298d63d1b2f6bb665be2e6adf69f5cbc
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"b\r\n The SR1.5 derived a GSAT estimate by taking the CMIP5 ensemble mean GSAT change of 0.99degC, sub-sampling to HadCRUTv4.6, noting the offset in trends \r\n(0.84degC HadCRUT4 observed GMST vs. 0.86degC modelled GMST) and adjusting by this to arrive at an estimate of 0.97degC change in GSAT. The likely uncertainty range \r\nof +-0.12degC was not further adjusted."


id: 386eb9291e7eab3e3a649a73dc7e3f3
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"c\r\n Note that the AR5 approach for the change from 1850-1900 to both 1986-2005 and 2003-2012 was based upon one dataset (HadCRUT4) and its parametric \r\nuncertainty estimates are known to underestimate the true uncertainty."


id: 2d94a2d389e7c4b4fd6da652d367f243
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"GMST and GSAT are physically distinct. There is high confidence that long-term changes in GMST and GSAT differ by at most 10% in \r\neither direction. However, conflicting lines of evidence from models and direct observations combined with limitations in theoretical \r\nunderstanding lead to low confidence in the sign of any difference in long-term trends. The very likely range of estimated historical \r\nGMST warming is combined with the assessed +- 10% uncertainty in the relationship between GMST and GSAT changes to infer \r\na GSAT equivalent, accounting for any possible real-world physical difference. Improvements in understanding may yield a robust \r\nbasis to apply a scaling-factor to account for the difference in future assessments."


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content:
"climate response to cumulative emissions of CO2 (TCRE) translates into remaining carbon budgets about 70 [40-140] GtCO2 larger \r\ncompared to SR1.5 on a like-for-like basis. Meanwhile, on the same like-for-like basis, updates to historical observational products \r\nwould reduce remaining carbon budgets reported in AR5 SYR based on WGIII scenario projections by about 180 [120 to 370] GtCO2. \r\nBox 5.2 provides a further overview of updates to estimates of the remaining carbon budget since AR5. "


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content:
"There is therefore high confidence that assessment of the magnitude and timing of impacts-related climate quantities at 1.5degC is \r\nnot substantially affected by the revised estimate of historical global warming. The assessment of the implications of limiting global \r\nwarming to 1.5degC compared to 2degC will also remain broadly unchanged by the updated estimate of historical warming, as this depends \r\non the relative impacts rather than the absolute impacts at any specific definition of global temperature anomaly (high confidence). "


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content:
"comprising more than 35,000 station records. These advances, both \r\nof which have substantially improved spatial coverage, have reduced \r\nuncertainties in assessments of both land and marine data. "


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created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 28383
content:
"The AR5 concluded that it was certain that GMST had increased \r\nsince the late 19th century. Total warming in GMST was assessed \r\nas 0.85 [0.65 to 1.06] degC over 1880-2012, while the change from \r\n1850-1900 to 2003-2012 was assessed at 0.78 [0.72 to 0.85] degC, \r\nand from 1850-1900 to 1986-2005 at 0.61 [0.55 to 0.67] degC. The \r\nSR1.5 reported warming of GMST from 1850-1900 to 2006-2015 \r\nof 0.87degC, with an 1880-2012 trend of 0.86degC and an 1880-2015 \r\ntrend of 0.92degC. The SRCCL concluded that since the pre-industrial \r\nperiod, surface air temperature over land areas has risen nearly twice \r\nas much as the global mean surface temperature (high confidence). "


id: 6e27239d594657b90861e6bc8f30d5d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 16641
content:
"Since AR5, there have been substantial improvements in the \r\navailability of instrumental archive data both over the ocean and \r\non land. A new version of the International Comprehensive Ocean\u0002Atmosphere Dataset (ICOADS Release 3.0, Freeman et  al., 2017) \r\ncomprises over 450 million in situ marine reports and incorporates \r\nnewly digitized data, increasing coverage in data sparse regions and \r\ntimes (e.g., polar oceans and World War I). The International Surface \r\nTemperature Initiative released a much improved collection of \r\nfundamental land surface air temperature records (Rennie et al., 2014) "


id: 1e1139d4704a27bf7e5a20f1ea08583
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 2485
content:
"independently-derived analyses and the assessed uncertainties \r\n(Kennedy, 2014; Kent et al., 2017) show unambiguously that global \r\nmean SST increased since the start of the 20th century, a conclusion \r\nthat is insensitive to the method used to treat gaps in data coverage \r\n(Kennedy, 2014). "


id: bea8ecbb22458e3cd86106d5b0dd06ba
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 30804
content:
"dataset (Xu et al., 2018) has higher network density in some regions \r\n(particularly Asia) than previously existing datasets. Global trends \r\nderived from CLSAT are generally consistent with those derived from \r\nother land datasets through 2014 (Xu et al., 2018)."


id: f23b564b91b8d9219948d1ff862c64a4
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 40011
content:
"The AR5 identified diurnal temperature range (DTR) as a substantial \r\nknowledge gap. The most recent analysis of Thorne et al. (2016a, b) \r\ncompared a broad range of gridded estimates of change in DTR, \r\nincluding a new estimate derived from the ISTI databank release \r\nusing the pairwise homogenization algorithm used to create \r\nGHCNMv4, and estimates derived from Vose et al. (2005), HadEX2 \r\n(Donat et al., 2013a), HadGHCND (Donat et al., 2013b), GHCNDEX \r\n(Donat et al., 2013b), Berkeley Earth (Rohde et al., 2013), and CRU TS \r\n(Harris et al., 2014). The analysis highlighted substantial ambiguity \r\nin pre-1950 estimates arising from sparse data availability. After \r\n1950 estimates agreed that DTR had decreased globally with most \r\nof that decrease occurring over the period 1960-1980. A subsequent \r\nDTR analysis using CLSAT further confirmed this behaviour (X. Sun \r\net al., 2018). "


id: e4d3ef4d17758acd0ee2803df19092ba
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 37541
content:
"No recent literature has emerged to alter the AR5 finding that it is \r\nunlikely that any uncorrected effects from urbanization (Box 10.3), or \r\nfrom changes in land use or land cover (Section 2.2.7), have raised \r\nglobal Land Surface Air Temperature (LSAT) trends by more than \r\n10%, although larger signals have been identified in some specific \r\nregions, especially rapidly urbanizing areas such as eastern China \r\n(Y. Li et al., 2013; Liao et al., 2017; Z. Shi et al., 2019). There is also no \r\nclear indication that site-specific data homogeneity issues have had \r\nany significant impact on global trends since the early 20th century; \r\nthere is more uncertainty in the 19th century, mainly arising from \r\na lack of standardization of instrument shelters, which has been \r\nlargely accounted for in data from central Europe (Jones et al., 2012), \r\nbut less so elsewhere. "


id: 654051f4646e6e91540ae378c2079e02
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 15089
content:
"The GHCNMv4 dataset (Menne et al., 2018) includes many more land \r\nstations than GHCNMv3, arising from the databank efforts of Rennie \r\net al. (2014), and calculates a 100-member parametric uncertainty \r\nensemble drawing upon the benchmarking analysis of Williams et al. \r\n(2012), as well as accounting for sampling effects. A new version of \r\nthe CRUTEM dataset (CRUTEMv5, Osborn et al., 2021) has increased \r\ndata completeness and additional quality control measures. A new \r\nglobal land dataset, the China Land Surface Air Temperature (CLSAT) "


id: 60c698b1b1c38e264799db9c661ad04d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 14324
content:
"the polar regions. GSAT trends from ERA5 reanalysis (Hersbach \r\net  al., 2020) are also broadly consistent with GMST trends from \r\nconventional surface datasets. However, the MERRA-2 reanalysis \r\n(Gelaro et  al., 2017) GSAT spuriously cooled sharply relative to \r\nERA-Interim and JRA-55 in about 2007 (Funk et al., 2019). Since the \r\nearly 2000s, analyses of surface temperature, from which near-surface \r\ntemperature may be derived, have also been available from various \r\nsatellites (Famiglietti et  al., 2018; Prakash et  al., 2018; Susskind \r\net  al., 2019), which have the potential to improve assessments of \r\ntemperature changes over data-sparse regions. "


id: 8b94014fd9096c153bbac0474b2c71f2
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 21727
content:
"variations and the verification of the methods, it is extremely likely\r\nthat interpolation results in a less-biased estimate of the actual \r\nglobal temperature change than ignoring regions with limited or no \r\ndata."


id: e77b44032ce0c3ea8088cfebb60d9fa5
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 38027
content:
"In total there are five conventional datasets which meet spatial \r\ncoverage requirements and draw from the most recent generation \r\nof SST analyses, four of which have sufficient data in the 1850-1900 \r\nperiod to allow an assessment of changes from that baseline \r\n(Table 2.3). A fifth dataset is added to the assessment for changes \r\nover land areas. Datasets share SST and LSAT data products and \r\nin several cases differ solely in the post-processing interpolation \r\napplied meaning that there are far fewer methodological degrees \r\nof freedom than implied by a straight count of the number of \r\navailable estimates."


id: 50e40f81585a011939534c5e8e83f6ac
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 11505
content:
"Most land areas in the extratropical Northern Hemisphere (NH) have \r\nwarmed faster than the GMST average over both the 1900-2020 \r\nand 1980-2020 periods (Figure 2.11b), although at more regional \r\nscales, particularly in data sparse regions, considerable uncertainty \r\nis introduced by sometimes large differences in trends between \r\ndifferent LSAT datasets (Rao et  al., 2018). Temperatures averaged \r\nover land areas globally have warmed by 1.59 [1.34 to 1.83] degC \r\nfrom 1850-1900 to 2011-2020, substantially higher than the SST \r\nwarming of 0.88 [0.68 to 1.01] degC. The four conventional surface \r\ntemperature products which meet all criteria to be included in the \r\nfinal assessment (Table 2.4) agree that each of the last four decades \r\nhas consecutively been the warmest globally since the beginning of \r\ntheir respective records (Figure 2.11c and Table 2.4). Each of the six \r\nyears 2015 to 2020 has very likely been at least 0.9degC warmer than \r\nthe 1850-1900 average."


id: 91f3bd55a248db2d2ed422e3b2d53eb0
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 22898
content:
"Estimates of GMST have also benefitted from improved estimation \r\nof parametric uncertainties. New versions of three long-standing \r\nproducts from NASA GISTEMP v4 (Lenssen et  al., 2019), NOAA \r\nGlobalTempv5 (B. Huang et  al., 2019b) and HadCRUT5 (Morice \r\net  al.,  2021) are all now available as ensemble estimates. These \r\nensembles each account for a variety of systematic and random \r\nuncertainty effects in slightly different ways, giving broadly similar \r\nresults, which are incorporated into the present assessment, with the \r\ntotal uncertainty generally declining up until the mid-20th century as \r\ndata coverage improves."


id: d4a64dde3d8bc872d1fbd9ce27160d3c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 34731
content:
"To conclude, from 1850-1900 to 1995-2014, GMST increased by \r\n0.85 [0.69 to 0.95] degC, to the first two decades of the 21st century \r\n(2001-2020) by 0.99 [0.84 to 1.10] degC, and to the most recent \r\ndecade (2011-2020) by 1.09 [0.95 to 1.20] degC. Each of the last four \r\ndecades has in turn been warmer than any decade that preceded it \r\nsince 1850. Temperatures have increased faster over land than over \r\nthe oceans since 1850-1900, with warming to 2011-2020 of 1.59 \r\n[1.34 to 1.83] degC versus 0.88 [0.68 to 1.01] degC, respectively."


id: dd9d8bd73a0b21592ebf7f003838b2bc
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 36254
content:
"Another significant development has been the incorporation of \r\nreanalysis products (Section 1.5.2) into operational monitoring \r\nof GSAT. It was reported in AR5 that various reanalyses were broadly \r\nconsistent with conventional surface datasets in the representation \r\nof trends since the mid-20th century. Since that time, Simmons et al. \r\n(2017) found that the ERA-Interim (Dee et  al., 2011) and JRA-55 \r\n(Kobayashi et al., 2015) reanalyses continued to be consistent, over \r\nthe last 20 years, with those surface datasets which fully represented "


id: 905fd97c4fe5e3e210130cf5bfd4217b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 22600
content:
"The AR5 reported that it was virtually certain that tropospheric \r\ntemperatures have risen, and stratospheric temperatures fallen, since \r\nthe mid-20th century, but that assessments of the rate of change \r\nand its vertical structure had only medium confidence in the NH \r\nextratropics and low confidence elsewhere. In particular there was \r\nlow confidence in the vertical structure of temperature trends in the \r\nupper tropical troposphere."


id: 2a00f523b2e6cb38bad5c64339f9971d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 4610
content:
"Temperatures averaged through the full lower stratosphere (roughly \r\n10-25 km) have decreased over 1980-2019 in all data products, \r\nwith the bulk of the decrease prior to 2000. The decrease holds \r\neven if the influence of the El Chichon (1982) and Pinatubo (1991) \r\nvolcanic eruptions on the trend, found by Steiner et al. (2020a) to \r\nhave increased the 1979-2018 cooling trend by 0.06degC per decade, \r\nis removed. Most datasets show no significant or only marginally \r\nsignificant trends over 2000-2019, and the results of Philipona et al. \r\n(2018) show weak increases over 2000-2015 in the very lowermost \r\nstratosphere sampled by radiosondes."


id: 7f57991c0a972849445434d88efaec01
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 19558
content:
"The STAR dataset shows cooling in the middle and upper stratosphere \r\nwith a trend of -0.56degC +- 0.16degC per decade for the mid-stratosphere \r\nand -0.62degC +- 0.29degC per decade for the upper stratosphere over \r\n1980-2019, although both cooling rates have slowed substantially \r\nsince the mid-1990s. The overall post-1980 trend is reduced in \r\nmagnitude by about 0.10degC per decade at both levels if the influences \r\nof the El Chichon and Pinatubo eruptions, and the solar cycle, are "


id: f0de5c4f0b664b16c258f0a183babba7
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 39744
content:
"removed (Zou and Qian, 2016). The results obtained by McLandress \r\net al. (2015) for 1980-2012, Randel et al. (2016) for 1979-2015, and \r\nMaycock et al. (2018) for 1979-2016 are broadly consistent with this."


id: 3dc053a92866d6782eb9f5a86bbd8163
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 8029
content:
"in  tropopause height has experienced a similar recent slowdown \r\nto that of the cooling of the lower stratosphere, as short-period \r\ntrends are typically inconclusive due to significant natural variability \r\n(Scherllin-Pirscher et al., 2021). RO data (Gao et al., 2015) indicate \r\nlittle change in tropopause height over the short period from 2006 \r\nto 2014, but a warming below the tropopause is observed over 2002 \r\nto 2019 (Figure 2.12). "


id: 3879ab0226f0652eebc9a6f86e328d68
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 7149
content:
"A rise in the tropopause height of 40 to 120 m per decade between \r\n1981 and 2015 was determined from both radiosonde and reanalysis \r\ndatasets (Xian and Homeyer, 2019). Local studies (e.g., Tang et al., 2017; \r\nX. Chen et al., 2019) found stronger trends in some regions near the \r\nsubtropical jet linked to tropical expansion (Section 2.3.1.4.1). Whilst \r\nSeidel and Randel (2006) found that the tropopause height was more \r\nclosely coupled with temperatures in the  stratosphere than those \r\nin the troposphere, it is not yet clear whether the rate of increase "


id: 373c108702c788310ad51135ce60e086
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 6934
content:
"In summary, the troposphere has warmed since the mid-20th century. \r\nThere is medium confidence that temperatures in the tropical upper \r\ntroposphere have warmed faster than those at the surface since 2001, \r\nbut low confidence in changes prior to 2001. It is virtually certain"


id: 46b3e17555366279f4370e0aa359c776
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 9643
content:
"that the lower stratosphere has cooled since the mid-20th century. \r\nHowever, most datasets show that lower stratospheric temperatures \r\nhave stabilized since the mid-1990s with no significant change over \r\nthe last 20 years. It is likely that middle and upper stratospheric \r\ntemperatures have decreased since 1980, but there is low confidence\r\nin the magnitude. It is virtually certain that the tropopause height has \r\nrisen over 1980-2019 but there is low confidence in the magnitude \r\nof this rise, or whether the rate of change has reduced commensurate \r\nwith stabilized lower stratospheric temperatures."


id: ed12ebf8adc53f9d95a2a3c6d4095779
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 39081
content:
"The AR5 assessed large-scale indicators of terrestrial paleo \r\nhydroclimate, including as part of its assessment of paleo floods and \r\ndroughts, but did not assess proxy evidence for paleo hydroclimate \r\nindicators over continental and larger scales. The paleoclimate \r\nevidence assessed in AR5 was broadly consistent with global \r\nhydroclimate scaling with temperature: warmer periods were wetter \r\n(e.g., the Pliocene; increased precipitation) with colder periods being \r\ndrier (e.g., the LGM; decreased precipitation). "


id: b70c2e24597fcc25a7c57fe5d50d496f
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 29414
content:
"Table 2.5 | Observed change (degC) in free atmospheric temperatures in various \r\ndatasets, for the lower tropospheric and lower stratospheric layers. Numbers \r\nin square brackets indicate 5-95% confidence ranges. Trend values are calculated \r\nwith ordinary least squares following (Santer et al., 2008) and are expressed as a total \r\nchange over the stated period. Further details on data sources and processing are \r\navailable in the chapter data table (Table 2.SM.1)."


id: 20b7721a2c90081da941a274f02123eb
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 2976
content:
"New analyses suggest that during the Holocene, the NH mid\u0002latitudes became increasingly wet, in phase with the strength of \r\nthe latitudinal temperature and insolation gradients (Shuman and \r\nMarsicek, 2016; Routson et al., 2019). Nevertheless, there was also \r\nconsiderable spatial heterogeneity and variability on centennial to \r\nmillennial timescales (Newby et  al., 2014; Shuman and Marsicek, \r\n2016; H. Zhang et  al., 2018; Liefert and Shuman, 2020). The NH \r\ntropics and many regions of the SH deep tropics experienced \r\nwetting up until the early to mid-Holocene but drying thereafter "


id: 852bd3c7eec76c789b0a51060bc8ef4b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 20570
content:
"This section focuses on large-scale changes in a subset of components \r\nof the hydrological cycle (Cross-Chapter Box 2.2). Chapter 8 undertakes \r\na holistic assessment of changes in the hydrological cycle integrating \r\nobservations, modelling and theoretical understanding, while Chapter 11 \r\nassesses hydrological cycle extremes such as droughts and floods. "


id: 4a74de4ec2d029e6ac2c4ba9bb0d963d
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10340
content:
"(Shanahan et al., 2015; Nash et al., 2016; Munoz et al., 2017; Quade \r\net al., 2018). Evidence for the SH is limited, with a wetting trend \r\nduring the Holocene in low latitudes of South America (Kanner et al., \r\n2013; Mollier-Vogel et  al., 2013) and parts of the African tropics \r\n(Schefuss et  al., 2011; Chevalier and Chase, 2015) but a drying \r\ntendency over southern Australia and New Zealand (van den Bos \r\net al., 2018; Barr et al., 2019) and South America (Quade and Kaplan, \r\n2017; Moreno et al., 2018)."


id: 9aa6367f32116f6034d802036b1b0f9
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24446
content:
"and ocean has remained well above the 1973-2019 average and \r\nreached record or near-record values (Figure 2.13b), with the strong \r\n2015-2016 El  Nino event boosting surface moisture levels (Byrne \r\nand O'Gorman, 2018). The abatement from around 2000 to 2012 \r\nreported in AR5 has not persisted. This is consistent with increases \r\nin total column water vapour (Section 2.3.1.3.3) and a resumption of \r\nrapid warming in surface temperatures (Section 2.3.1.1.3). The global \r\naveraged relative humidity however has remained depressed since \r\n2000 (Figure 2.13d; Simmons et al., 2010; Willett et al., 2014, 2020; \r\nDunn et al., 2017; Vicente-Serrano et al., 2018). "


id: 20cab9760de2cd582b2ab0e0e8f6c704
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 2989
content:
"To summarize, since AR5 there has been considerable progress in \r\ndetecting the variations of the global hydrological cycle prior to the \r\ninstrumental period. There are indications from multiple sources of \r\na wetting trend during the Holocene, particularly for the NH and parts \r\nof the SH tropics (medium confidence). Hydroclimate during the CE \r\nis dominated by regional variability, generally precluding definitive \r\nstatements on changes at continental and larger scales, with a general \r\nreduction of mega-drought occurrences over the last about 500 years \r\n(medium confidence). Availability of proxy data for assessing Holocene \r\nhydroclimate variability is biased towards the NH, with medium \r\nevidence but low agreement for the assessment of SH changes. "


id: 149442f6046645b59de477e27009929b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 847
content:
"In summary, observations since the 1970s show a very likely increase \r\nin near surface specific humidity over both land and oceans. A very \r\nlikely decrease in relative humidity has occurred over much of the \r\nglobal land area since 2000, particularly over mid-latitude regions of \r\nthe NH, with increases at northern high latitudes. "


id: e9247b2249845747d2ba750beabc2e67
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 38367
content:
"The AR5 concluded that total column water vapour (TCWV) very likely\r\nincreased since the 1970s, at a rate that was overall consistent with \r\nthe Clausius-Clapeyron relationship (about 7% per degC) given the \r\nobserved increase in atmospheric temperature."


id: 7094cebafc55bff2ebff638a14e0e56e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 17064
content:
"The AR5 reported very likely widespread increases in near-surface air \r\nspecific humidity since the 1970s, abating from around 2000 to 2012 \r\n(medium confidence). This abatement resulted in a recent decline in \r\nrelative humidity over the land."


id: 62da9859f920cce377c44d81cf3bab57
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 14688
content:
"Records prior to the instigation of quasi-global coverage by radiosondes \r\nrequire the use of statistical relationships to infer TCWV from historical \r\nSST observations or the evaluation of centennial-scale reanalysis \r\nproducts (Smith and Arkin, 2015). These approaches reveal two \r\nperiods of positive trends, one from 1910 to 1940 and the other from \r\n1975 onwards (Zhang et al., 2013; Mieruch et al., 2014; Shi et al., \r\n2018), concurrent with periods of positive SST trends (Figure 2.11). \r\nPotential sources of errors in the SST-based estimation of TCWV \r\ninclude both uncertainties in historical SST and uncertainties in the \r\nparameters that define the relationship between the variables (Smith \r\nand Arkin, 2015). Trends based on 20CRv2c, ERA-20C and ERA-20CM \r\nindicate an increase in TCWV over much of the global ocean since \r\nthe beginning of the 20th century, particularly over the tropics (Bordi \r\net al., 2015; Smith and Arkin, 2015; Poli et al., 2016). TCWV trends "


id: bf8c76c95a69a66bf7175d12ddf924bd
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 30963
content:
"Near surface humidity has been monitored using in-situ data \r\n(e.g., NOCSv2.0; Berry and Kent, 2011), satellite-derived estimations \r\n(e.g.,  HOAPS3, Liman et  al., 2018; J-OFURO3, Tomita et  al., 2019), \r\nglobal gridded products such as HadISDH (Willett et al., 2014, 2020), \r\nand reanalyses (e.g.,  ERA5, JRA-55 and 20CRv3). In-situ based \r\nhumidity products suffer from uncertainties over poorly sampled \r\nregions particularly in the SH (Berry and Kent, 2011; Kent et  al., \r\n2014; Willett et al., 2014). There is general consensus in the inter\u0002annual variability and sign of trends implying high confidence in \r\nincreasing specific humidity since the 1970s and decreasing relative \r\nhumidity since 2000, particularly over land (Simmons et  al., 2010; \r\nWillett et al., 2014, 2020). Since 2012, specific humidity over land "


id: cfb855f3945a8ca76daf6070716671ec
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 33904
content:
"estimated since the middle of the 20th century from radiosonde \r\nobservations show significant increases over North America and \r\nlarge portions of Eurasia, while decreases are restricted to Australia, \r\neastern Asia and the Mediterranean region (Y. Zhang et al., 2018). \r\nOverall, there is a significant increase in TCWV over global land areas \r\nsince 1979 (Chen and Liu, 2016)."


id: 37d9274931d66eb5c26b4f366d8a36c0
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 7034
content:
"account for the observed TCWV-temperature scaling. Substantial \r\npotential inhomogeneities affect trend estimates based on satellite, \r\nreanalysis and merged products in particular over Central Africa, the \r\nSahara and central South America (Schroder et al., 2016, 2019; J. Wang \r\net al., 2016). Moreover, data gaps in observations from ground-based \r\nGNSS receivers and radiosondes lead to low confidence in TCWV \r\nestimation in these regions. "


id: d5e7888faa2d1661af8c0138004e693
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 34947
content:
"In summary, positive trends in global total column water vapour \r\nare very likely since 1979 when globally representative direct \r\nobservations began, although uncertainties associated with changes \r\nin the observing system imply medium confidence in estimation of the \r\ntrend magnitudes. Low confidence in longer-term trends arises from \r\nuncertainties in the SST-TCWV relationship and current centennial \r\nscale reanalyses, particularly during the first half of the 20th century."


id: 2461cdd12f48152c22697609c4518c82
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 3593
content:
"The AR5 concluded that there was low confidence in precipitation \r\nchange averaged over global land areas prior to 1950, and medium \r\nconfidence thereafter with no significant global trends. There was \r\na likely overall increase in precipitation in the well-sampled NH \r\nmid-latitudes, with high confidence after 1951."


id: 49f07998e1c733fb5c0d429e088a9bb3
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10249
content:
"In summary, globally averaged land precipitation has likely increased \r\nsince the middle of the 20th century (medium confidence), with low \r\nconfidence in trends prior to 1950. A faster increase in global land \r\nprecipitation was observed since the 1980s (medium confidence), \r\nwith large interannual variability and regional heterogeneity. \r\nOver the global ocean there is low confidence in the estimates of \r\nprecipitation trends, linked to uncertainties in satellite retrievals, \r\nmerging procedures and limited in situ observations."


id: afcd41c828378746dcd8243b0eb2ab8e
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 28165
content:
"Table 2.6 | Globally averaged trend estimates over land and 90% confidence \r\nintervals for annual precipitation for each time series in Figure 2.15c over \r\nthree periods all ending in 2019. Trends are calculated using OLS regression with \r\nsignificance assessed after Santer et al. (2008). Further details on data sources and \r\nprocessing are available in the chapter data table (Table 2.SM.1)."


id: bfacb1e3e304c8ee9e19a7bdf7773e08
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 31003
content:
"Estimating global-scale trends in P-E using direct observations \r\nalone is challenging due to limited evaporation measurements and \r\ninhomogeneities in satellite-derived precipitation and evaporation \r\ndatasets (Hegerl et al., 2015; Lopez et al., 2017). Hence, the assessment \r\nof global P-E trends is generally performed using reanalyses, although \r\nchanges in the observing system imply considerable uncertainty \r\n(Skliris et al., 2014). Since the second half of the 20th century, several \r\nreanalyses and observational datasets have shown increases in P-E \r\nover global land, although 75% of land areas exhibit no significant "


id: 20f94a62c761456f4c4c883efda651de
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 3022
content:
"The AR5 concluded that the pattern of precipitation minus evaporation \r\n(P-E) over the ocean had been enhanced since the 1950s (medium \r\nconfidence). Saline surface waters had become saltier, while the \r\nrelatively fresh surface waters had become fresher. The inferred \r\nchanges in P-E were consistent with the observed increased TCWV, \r\nalthough uncertainties in the available products prevented identifying \r\nrobust trends."


id: a5f8126a7b82d5e6a80b55eba3276d77
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 26421
content:
"changes and both internal variability and observational uncertainty \r\nare substantial (Greve et al., 2014; Robertson et al., 2016). The recently \r\nreleased ERA5 (Hersbach et  al., 2020) showed improvements in the \r\nrepresentation of tropical precipitation, although it overestimates \r\nglobal precipitation trends in comparison to ERA-Interim and GPCP \r\n(Nogueira, 2020), and suffers from temporal changes in the annual \r\nbalance between precipitation and evaporation (Hersbach et al., 2020). \r\nThe spatial pattern of P-E trends over 1980-2019 (Figure 2.16a) are \r\nlargely consistent with the trends in the GPCP v2.3 precipitation dataset \r\n(Figure 2.15f and Section 2.3.1.3.4) and agrees in sign with the trends \r\nfrom other reanalyses such as JRA-55 and MERRA-2 (L. Yu et al., 2020). "


id: 9ba7c9953689e0f90e0c9c6ccee1023c
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 24639
content:
"A variety of reanalysis products exhibit diverse temporal evolutions \r\nof P-E (Figure 2.16b-d). Globally MERRA-2, ERA20C and ERA20CM \r\nexhibit little change whereas JRA-55, ERA5 and 20CRv3 all \r\nimply long-term changes (Figure 2.16d). A potential limitation in \r\nestimating P-E from some reanalysis products is readily apparent \r\nwhen considering the temporal evolution of global P-E from CFSR \r\nand MERRA (Figure 2.16d) which both exhibit strong discontinuities \r\nover the global ocean in the late 1990s. Over global land as a whole, "


id: 49b0393c33d2f9654140680266e8b3e5
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 10198
content:
"Figure 2.16 | Changes in precipitation minus evaporation. (a) Trends in precipitation minus evaporation (P-E) between 1980 and 2019. Trends are calculated using OLS \r\nregression with significance assessed following AR(1) adjustment after Santer et al. (2008) ('x' marks denote non-significant trends). Time series of (b) global, (c) land-only and \r\n(d) ocean-only average annual P-E (mm day-1). Further details on data sources and processing are available in the chapter data table (Table 2.SM.1)."


id: 26fede781a7ec36e728f1d837420438b
created_at: 2023-04-19 13:21:32
updated_at: 2023-04-19 13:21:32
content_type: text
index: climate_gpt_v2
vector_id: 4023
content:
"2.2). Chapter 8 assesses large-scale as well as regional aspects of \r\ncirculation components and their impact on the hydrological cycle, \r\nwhile Chapter 11 assesses the association of circulation changes and \r\nvariability with extreme events."


id: 5e8a537390df0254a21fc1403cea07cb
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13922
content:
"In conclusion, observational uncertainty yields low confidence  in \r\nglobally averaged trends in P-E over the 20th century, with a spatial \r\npattern dominated by precipitation changes over land and by \r\nevaporation increases over the ocean. Different reanalyses disagree \r\non the sign of long-term changes in the global mean P-E."


id: 75003a7ad50049cb6a02403c7b35ac47
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17820
content:
"The AR5 reported low confidence in trends in the strength of the \r\nHadley circulation (HC) and the Walker circulation (WC) due \r\nto uncertainties in available reanalysis datasets and the large \r\ninterannual-to-decadal variability of associated circulation patterns. \r\nHowever, AR5 indicated a likely widening of the tropical belt since the \r\n1970s, albeit with large uncertainty in the magnitude of this change. \r\nThere was high confidence that the post-1990s strengthening of \r\nthe Pacific WC reversed its weakening observed from the mid-19th \r\ncentury to the 1990s."


id: 8320e6e207fbb0a11e1e1ab73c27e027
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20194
content:
"The AR5 concluded that there was low confidence in a positive trend \r\nin global river discharge during the 20th century. It noted that many \r\nof the largest rivers with long term streamflow records have been \r\nimpacted by non-climatic human influences such as dam construction \r\nor land-use change."


id: 51ab06a3cf154568cc99fdfdccbaf1d4
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11651
content:
"River discharge is monitored widely, although gaps remain at \r\na subcontinental scale over central Asia and Africa (Wei et al., 2020). \r\nSubstantial recent efforts have been made to generate new global \r\nstreamflow datasets, consolidating observations from many stream \r\ngauges to create streamflow indices (Do et al., 2018; Gudmundsson \r\net al., 2018) and gridded products using neural networks (Barbarossa \r\net al., 2018) or combinations between observations and reanalyses \r\n(Suzuki et al., 2018; Ghiggi et al., 2019). "


id: 702782473d06a13cf246ef199dd0f638
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16985
content:
"From centennial-scale reanalyses, Liu et  al. (2012) and D'Agostino \r\nand Lionello (2017) found divergent results on HC extent over the \r\nlast 150 years, although with unanimity upon an intensification of \r\nthe SH HC. A substantial discrepancy between HC characteristics \r\nin centennial-scale reanalyses and in ERA-Interim (D'Agostino and \r\nLionello, 2017) since 1979 yields significant questions regarding \r\ntheir ability to capture changes in HC behaviour. Taken together \r\nwith the existence of apparent non-climatic artefacts in the datasets \r\n(Nguyen et al., 2015), this implies low confidence in changes in the \r\nextent and intensity of HC derived from centennial-scale reanalyses. \r\nHowever, using multiple observational datasets and centennial-scale \r\nreanalyses, Bronnimann et  al. (2015) identified a  southward shift \r\nin the NH HC edge from 1945 to 1980 of about 0.25deg latitude per \r\ndecade, consistent with observed changes in global land monsoon \r\nprecipitation (Section 2.3.1.4.2)."


id: aa75e7b4ffcb935933cdc6ee5f2523ee
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 27214
content:
"In summary, the sign of global streamflow trends remains uncertain, \r\nwith slightly more globally gauged rivers experiencing significantly \r\ndecreasing flows than significantly increasing flows since the 1950s \r\n(low confidence)."


id: 5e8343bbfbe6b4ea4ea0c7f543040ec4
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13921
content:
"Trends in the HC intensity since 1979 differ between reanalyses, \r\nalthough there is a tendency toward HC intensification (Figure 2.17b; \r\nNguyen et al., 2013; Chen et al., 2014; D'Agostino and Lionello, 2017; \r\nR. Huang et al., 2019), which is more marked in the NH than the SH \r\n(Studholme and Gulev, 2018). However, the ability of reanalyses to \r\nrepresent the HC strength has been questioned due to inaccurate \r\nrepresentation of latent heating distribution, which is directly related \r\nto tropical convection and influences the HC dynamics (Chemke and \r\nPolvani, 2019; Mathew and Kumar, 2019)."


id: f9ca4507ade8a6a6ea84ed5064366c36
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41305
content:
"Paleo evidence during the LGM indicates a weaker WC over the Indian \r\nOcean (DiNezio et  al., 2018; Windler et  al., 2019) with a  stronger \r\nPacific WC (DiNezio and Tierney, 2013). During the Holocene, \r\na  transition from a strong WC located more westward during the \r\nEarly-to-Mid Holocene towards a weak and eastward shifted WC \r\nduring the late Holocene was inferred from proxy records from the \r\nPacific Warm Pool and South East Asia (Barr et al., 2019; Dang et al., \r\n2020; Griffiths et al., 2020), in concurrence with changes in ENSO \r\nactivity (Section 2.4.2). Reconstructions for the CE showed weakened \r\nWC during 1000-1250 and since 1850, with an intensified circulation \r\nduring 1500-1850 CE (Xu et al., 2016; Deng et al., 2017). "


id: 75c827554ab31ae5c20630c988b142a2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17954
content:
"Considering instrumental records, there is considerable interdecadal \r\nvariability in the strength of the WC, resulting in time-period dependent \r\nmagnitude and even sign of trends (Carilli et al., 2015; Bordbar et al., \r\n2017; Hou et al., 2018), with some studies reporting weakening over \r\nthe 20th century (e.g.,  Power and Kociuba, 2011; Liu et  al., 2019), \r\nwhile others reported strengthening (Z. Li et  al., 2020), particularly "


id: 506c7b988543c374bb00bea71ae404a7
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11428
content:
"on  millennial time scales. The intensity of the monsoon systems \r\nis generally out of phase between hemispheres, being associated \r\nwith the precession cycle (about 21-23 kyr) (An et al., 2015; P.X. \r\nWang et al., 2017; Seth et al., 2019), with intensified NH monsoon \r\nsystems during precession minima (Toucanne et al., 2015; Wagner \r\net  al., 2019). The eccentricity forcing (about 100 kyr cycle) shows \r\nstronger GM during interglacial periods (P.X. Wang et  al., 2014, \r\n2017; An et al., 2015; Mohtadi et al., 2016). Changes in obliquity \r\n(about 41 kyr cycle) modify the strength of monsoon systems, with \r\nincreased summer monsoon rainfall when obliquity is maximal (Y. \r\nLiu et al., 2015b; Mohtadi et al., 2016). Millennial scale variability in \r\nGM during the LDT was also linked to the occurrences of Heinrich \r\nstadials, resulting in weakened NH monsoons and intensified SH \r\nmonsoons (An et al., 2015; P.X. Wang et al., 2017; Margari et al., \r\n2020). "


id: f8bedd975d95892eaf3a1670541d595e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41122
content:
"In summary, there has been a likely widening of the Hadley circulation \r\nsince the 1980s, mostly due to its extension in the NH, although \r\nthere is only medium confidence in the extent of the changes. This \r\nhas been accompanied by a strengthening of the Hadley circulation, \r\nparticularly in the NH (medium confidence). There is low confidence\r\nin the estimation of long-term trends in the strength of the Walker \r\ncirculation, which are time period dependent and subject to dataset \r\nuncertainties. Trends since 1980 are better characterized and consistent \r\nwith a very likely strengthening that resembles a La Nina-like Walker \r\ncirculation and a westward shift of the Walker circulation, although \r\nwith medium confidence in the magnitude of the changes, arising from \r\nthe differences between satellite observations and reanalysis products."


id: f9bee920dc426fe0fe0dfa9e9991e433
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41300
content:
"The AR5 reported a weakening of the global monsoon (GM) circulation \r\nas well as a decrease of global land monsoon rainfall over the second \r\nhalf of the 20th century. Nevertheless, there was low confidence in the \r\nobserved circulation trends due to uncertainties in reanalysis products \r\nand in the definition of the monsoon area. From a paleo perspective, \r\nAR5 only assessed regional monsoon changes."


id: 7d1b6b5b792033480f27df30a866386f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 19197
content:
"In summary, observed trends during the last century indicate that the \r\nGM precipitation decline reported in AR5 has reversed since the 1980s, \r\nwith a likely increase mainly due to a significant positive trend in the NH \r\nsummer monsoon precipitation (medium confidence). However, GM "


id: 350243c6e90380e2d2ecf2b352556009
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6570
content:
"precipitation has exhibited large multi-decadal variability over the last \r\ncentury, creating low confidence in the existence of centennial-length \r\ntrends in the instrumental record. Proxy reconstructions show a likely\r\nNH monsoons weakening since the mid-Holocene, with opposite \r\nbehaviour for the SH monsoons. "


id: e4c23f6ac7cbde78cc2c0048413c9330
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 37529
content:
"Cattiaux  et  al., 2016; Vavrus, 2018). Hypothesized links to Arctic \r\nwarming are assessed in Cross-Chapter Box 10.1. "


id: 49af2bb7c9bca8757ea50b7861feebe7
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 10195
content:
"The AR5 reported a likely poleward shift of storm tracks and jet \r\nstreams since the 1970s from different datasets, variables and \r\napproaches. These trends were consistent with the HC widening and \r\nthe poleward shifting of the circulation features since the 1970s. \r\nThere was low confidence in any large-scale change in blocking. "


id: ddd5215afb2724bc349e2ffd0f32c03c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 36288
content:
"During 950-1400 CE, hydroclimate indicators suggest a northward \r\nshift of Pacific storm tracks over North America (McCabe-Glynn et al., \r\n2013; Steinman et al., 2014) which was comparable in magnitude \r\nto that over 1979-2015 (J. Wang et al., 2017a). Storm tracks over \r\nthe North Atlantic-European sector shifted northward as indicated \r\nby multi-proxy indicators over the North Atlantic (Wirth  et  al., \r\n2013; Orme et al., 2017) and Mediterranean (Roberts et al., 2012). \r\nReconstructed westerly winds in the SH suggest a poleward shift \r\n(Lamy et al., 2010; Schimpf et al., 2011; Goodwin et al., 2014; Koffman \r\net al., 2014; Moreno et al., 2018), with latitudinal change comparable \r\nto that during recent decades (Swart and Fyfe, 2012; Manney and \r\nHegglin, 2018). "


id: 8b7ce2e92dfb817753810411e988c319
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 21707
content:
"Multiple reanalyses show that since 1979 the subtropical jet \r\nwind speeds have generally increased in winter and decreased \r\nin summer in both hemispheres, but the trends are regionally \r\ndependent (Pena-Ortiz et al., 2013; Manney and Hegglin, 2018; S.H. \r\nLee et  al., 2019). Over NH mid-latitudes, the summer zonal wind \r\nspeeds have weakened in the mid-troposphere (Francis and Vavrus, \r\n2012; Coumou et  al., 2014, 2015; Haimberger and Mayer, 2017). \r\nMeanwhile there are indications of enhanced jetstream meandering \r\nin boreal autumn at the hemispheric scale (Francis and Vavrus, 2015; \r\nDi Capua and Coumou, 2016), whereas the regional arrangement of \r\nmeandering depends on the background atmospheric state (Cohen \r\net al., 2020). These meandering trends, however, are sensitive to the \r\nmetrics used (Screen and Simmonds, 2013; Hassanzadeh et al., 2014; "


id: 31e699ddd0f97b95a173ca1d926cce2c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
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index: climate_gpt_v2
vector_id: 6033
content:
"Robust trends in blocking have only been found in certain regions \r\nand specific seasons during recent decades. Increases in blocking \r\nfrequency have occurred over low-latitude regions in the North \r\nAtlantic in boreal winter (Davini et al., 2012), the South Atlantic in \r\naustral summer (Dennison et al., 2016) and the southern Indian Ocean \r\nin austral spring (Schemm, 2018). Over the subpolar North Atlantic \r\nsustained periods of positive Greenland blocking were identified \r\nduring 1870-1900 and from the late 1990s to 2015 (Hanna et al., \r\n2015). Further analysis of association of Greenland blocking with the \r\nNAM is provided in Section 2.4.1.1. Meanwhile, a reduced blocking \r\nfrequency has been found over winter in Siberia (Davini et al., 2012) "


id: 21fa7b21b5577699f8d63b19a4bea6e8
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 3205
content:
"and the south-western Pacific in austral spring (Schemm, 2018). \r\nOver eastern European Russia and western Siberia (40degE-100degE) a \r\ntendency towards longer blocking events was reported by Luo et al. \r\n(2016) for 2000-2013 and by Tyrlis et  al. (2020) for 1979-2017. \r\nInter-annual variance in the number of blocking events over the SH \r\n(Oliveira et  al., 2014) and North Atlantic (Kim and Ha, 2015) has \r\nenhanced. Blocking events and their trends are sensitive to choice \r\nof datasets, calculation periods and methods (Cheung et al., 2013; \r\nBarnes et al., 2014; Pepler et al., 2018; Rohrer et al., 2018; Woollings \r\net  al., 2018b; Kononova and Lupo, 2020). As a result, hemispheric \r\nand global trends in blocking frequency have overall low confidence."


id: 76450053bd2fc39ab8a9a7f9904a6eaf
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 18028
content:
"shifting of extratropical jets in the NH during the mid-Holocene and \r\nover 950-1400 CE to latitudes that likely were similar to those since \r\n1979. There is low confidence in observed global-scale changes in the \r\noccurrence of blocking events."


id: fe39298d488fb8f54aba5d25daf7b774
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 42092
content:
"The AR5 concluded that surface winds over land had generally \r\nweakened. The confidence for both land and ocean surface wind \r\ntrends was low owing to uncertainties in datasets and measures \r\nused. Sea level pressure (SLP) was assessed to have likely decreased \r\nfrom 1979-2012 over the tropical Atlantic and increased over large \r\nregions of the Pacific and South Atlantic, but trends were sensitive to \r\nthe period analysed. "


id: 759e28c259688ef0f770a04d4d99d108
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
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vector_id: 17923
content:
"In summary, the total number of extratropical cyclones has likely\r\nincreased since the 1980s in the NH (low confidence), but with \r\nfewer deep cyclones particularly in summer. The number of strong \r\nextratropical cyclones has likely increased in the SH (medium \r\nconfidence). The extratropical jets and cyclone tracks have likely been \r\nshifting poleward in both hemispheres since the 1980s with marked \r\nseasonality in trends (medium confidence). There is low confidence in "


id: a51412f9ba966852da68a3f14c1b9a8e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 26271
content:
"Terrestrial in situ wind datasets have been updated and the quality\u0002control procedures have been improved, with particular attention to \r\nhomogeneity and to better retaining true extreme values (Dunn et al., \r\n2012, 2014, 2016). Global mean land wind speed (excluding Australia) "


id: 9032359dc2ee3e9ca8f68dcb7e949814
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 22575
content:
"from HadISD for 1979-2018 shows a reduction (stilling) of 0.063 m s-1\r\nper decade (Azorin-Molina et al., 2019). Trends are broadly insensitive \r\nto the subsets of stations used. Although the meteorological \r\nstations are unevenly distributed worldwide and sparse in South \r\nAmerica and Africa, the majority exhibit stilling particularly in the \r\nNH (Figure 2.19). Regionally, strong decreasing trends are reported \r\nin central Asia and North America (-0.106 and -0.084 m s-1 per \r\ndecade respectively) during 1979-2018 (McVicar et al., 2012; Vautard \r\net al., 2012; J. Wu et al., 2018; Azorin-Molina et al., 2019). This stilling \r\ntendency has reversed after 2010 and the global mean surface winds \r\nhave strengthened (Zeng et al., 2019b; Azorin-Molina et al., 2020), \r\nalthough the robustness of this reversal is unclear given the short \r\nperiod and interannual variability (Kousari et al., 2013; Kim and Paik, \r\n2015; Azorin-Molina et al., 2019)."


id: 5c621f96a16dd6bccf8fe4186baba1bf
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13507
content:
"Over the ocean, datasets demonstrate considerable disagreement in \r\nsurface wind speed trends and spatial features (Kent et  al., 2013). \r\nGlobal ocean surface winds from NOCv2.0 demonstrate upward \r\ntrends of about 0.11 m s-1 per decade (1979-2015) with somewhat \r\nsmaller trends from WASwind for 1979-2011 (Azorin-Molina et al., \r\n2017, 2019). The trends are consistent until 1998, but diverge \r\nthereafter. Both ERA5 and JRA-55 reanalyses show consistently "


id: 6e75ed443c6190f24f4e2faa089de2c8
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16698
content:
"The modern era reanalyses exhibit SLP increases over the SH \r\nsubtropics with stronger increases in austral winter over 1979-2018. \r\nOver the NH, SLP increased over the mid-latitude Pacific in boreal \r\nwinter and decreased over the eastern subtropical and mid-latitude \r\nNorth Atlantic in boreal summer. Discrepancies in the low-frequency \r\nvariations during the first half of the 20th century exist in the "


id: e3e968412bd204bd7ef77e24192211dc
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 37384
content:
"centennial-scale reanalysis products (Befort et  al., 2016). Overall, \r\nmodern reanalysis datasets support the AR5 conclusion that \r\nthere is no clear signal for trends in the strength and position of \r\nthe  permanent and quasi-permanent pressure centres of action \r\nsince the 1950s. Instead, they highlight multi-decadal variations. \r\nLarge-scale SLP is strongly associated with the changes in modes of \r\nvariability (Section 2.4 and Annex IV)."


id: e86344e01774efa8fbf8adae19c36dd2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 38216
content:
"In summary, since the 1970s a worldwide weakening of surface wind \r\nhas likely occurred over land, particularly marked in the NH, with low \r\nconfidence in a recent partial recovery since around 2010. Differences \r\nbetween available wind speed estimates lead to low confidence in \r\ntrends over the global ocean as a whole but with most estimates \r\nshowing strengthening globally over 1980-2000 and over the last \r\nfour decades in the Southern Ocean, western North Atlantic and the \r\ntropical eastern Pacific. "


id: 5b6993bbb1379bc0950595596211fa69
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13328
content:
"The AR5 assessed changes in the polar vortices and reported a likely\r\ndecrease in the lower-stratospheric geopotential heights over Antarctica \r\nin spring and summer at least since 1979. "


id: 32d6f4ffa024dbd4a053d226dead4aed
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6211
content:
"In summary, it is likely that the northern lower stratospheric polar \r\nvortex has weakened since the 1980s in midwinter, and its location \r\nhas shifted more frequently toward the Eurasian continent. The short \r\nrecord and substantial decadal variability yields low confidence in \r\nany trends in the occurrence of SSW events in the NH winter and such \r\nevents in the SH are rare."


id: bb71580545fdfef311cf54d202fc3966
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30198
content:
"Multiple definitions for the polar vortex strength and sudden \r\nstratospheric warming (SSW) events have been proposed and \r\ncompared (Butler et al., 2015; Palmeiro et al., 2015; Waugh et al., 2017; \r\nButler and Gerber, 2018), and new techniques identifying daily vortex \r\npatterns and SSWs have been developed (D.M. Mitchell et al., 2013; \r\nKretschmer et al., 2018). Errors in reanalysis stratospheric winds were \r\nassessed and discrepancies in stratospheric atmospheric circulation \r\nand temperatures between reanalyses, satellites and radiosondes have \r\nbeen reported (D.M. Mitchell et al., 2013; Duruisseau et al., 2017). "


id: 919408aa337bebeb9290699d8f43bbb5
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 22837
content:
"This section focuses on large-scale changes in a subset of components \r\nof the cryosphere (Cross-Chapter Box 2.2). Chapter 9 undertakes \r\na holistic assessment of past and possible future changes and \r\nunderstanding of key processes in the cryosphere, including those at \r\nregional scales, integrating observations, modelling and theoretical \r\nunderstanding, while, here in chapter 2, the focus is on past large\u0002scale, observation-based cryospheric changes. "


id: daaffbb004a6d57fafd3a0def003b60a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 35769
content:
"The AR5 reported that the annual mean Arctic sea-ice extent (SIE) \r\nvery likely decreased by 3.5-4.1% per decade between 1979 and \r\n2012 with the summer sea-ice minimum (perennial sea ice) very \r\nlikely decreasing by 9.4-13.6% per decade. This was confirmed by \r\nSROCC reporting the strongest reductions in September (12.8 +- 2.3% \r\nper decade; 1979-2018) and stating that these changes were likely\r\nunprecedented in at least 1 kyr (medium confidence). The spatial \r\nextent had decreased in all seasons, with the largest decrease for \r\nSeptember (high confidence). The AR5 reported also that the average \r\nwinter sea ice thickness within the Arctic Basin had likely decreased \r\nby between 1.3 m and 2.3 m from 1980 to 2008 (high confidence), \r\nconsistent with the decline in multi-year and perennial ice extent. "


id: b3b2ea34053a8e12ab9a5eb0808fd9f6
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 28859
content:
"The SROCC stated further that it was virtually certain that Arctic sea \r\nice had thinned, concurrent with a shift to younger ice. Lower sea ice \r\nvolume in 2010-2012 compared to 2003-2008 was documented in \r\nAR5 (medium confidence). There was high confidence that, where the \r\nsea ice thickness had decreased, the sea-ice drift speed had increased. "


id: 2ba3cf34c7ec9b53c3a30a80456373fe
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 4933
content:
"Proxy records are used in combination with modelling to assess Arctic \r\npaleo sea ice conditions to the extent possible. For the Pliocene, \r\nlimited proxy evidence of a reduced sea ice cover compared to \r\n'modern' winter conditions (Knies et al., 2014; Clotten et al., 2018) \r\nand model simulations of a largely ice-free Arctic Ocean during \r\nsummer (Howell et al., 2016; Feng et al., 2019; F. Li et al., 2020) imply \r\nmedium confidence that the Arctic Ocean was seasonally ice covered. \r\nOver the LIG, sparse proxy reconstructions (Stein et al., 2017; Kremer \r\net al., 2018) and proxy evidence from marine sediments (Kageyama \r\net al., 2021b) provide medium confidence of perennial sea ice cover. "


id: 8f4c0e98bad0d33039a28510006deea3
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 22421
content:
"Over the past 13 kyr proxy records suggest extensive sea-ice \r\ncoverage during the Younger Dryas (at the end of the LDT), followed \r\nby a decrease in sea ice coverage during the Early Holocene, and \r\nincreasing sea-ice coverage from the MH to the mid-15th century \r\n(De Vernal et al., 2013; Belt et al., 2015; Cabedo-Sanz et al., 2016; \r\nArmand et al., 2017; Belt, 2018). There is limited evidence that the \r\nCanadian Arctic had less multiyear sea ice during the Early Holocene \r\nthan today (Spolaor et al., 2016). For more regional details on paleo \r\narctic sea ice see Section 9.3.1.1. "


id: cc1dfcc58f6f16abeab0c63c49d6e63e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 33228
content:
"Pan-Arctic SIE conditions (annual means and late summer) during the \r\nlast decade were unprecedented since at least 1850 (Figure 2.20a; \r\nWalsh et al., 2017, 2019; Brennan et al., 2020), while, as reported \r\nin SROCC, there remains medium confidence that the September \r\n(late  summer) Arctic sea ice loss during the last decade was \r\nunprecedented during the past 1 kyr. Sea-ice charts since 1850 \r\n(Walsh et al., 2017, 2019) suggest that there was no significant trend \r\nbefore the 1990s, but the uncertainty of these estimates is large and \r\ncould mask a trend, a possibility illustrated by Brennan et al. (2020), \r\nwho found a loss of Arctic sea ice between 1910 and 1940 in an \r\nestimate based on a data assimilation approach."


id: 3b1f4fe13beb4ad424d344868bd84ff
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 7587
content:
"Over the past two decades, first-year sea ice has become more \r\ndominant and the oldest multiyear ice (older than 4 years) which \r\nin March 1985 made up 33% of the Arctic sea-ice cover, has nearly \r\ndisappeared, making up 1.2% in March 2019 (Perovich et  al., \r\n2020). The loss of older ice is indicative of a thinning overall of ice \r\ncover (Tschudi et  al., 2016), but also the remaining older ice has \r\nbecome thinner (E. Hansen et al., 2013). Since in situ ice thickness \r\nmeasurements are sparse, information about ice thickness is mainly \r\nbased on airborne and satellite surveys. Records from a combination "


id: 81915ba2f0500738e4751aafdb86a83
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 19922
content:
"The SROCC noted the lack of continuous records of snow on sea \r\nice. Nevertheless in recent decades, more snow on sea ice has been \r\nobserved in the Atlantic sector in the Arctic than in the western Arctic \r\nOcean (Webster et al., 2018). Previously, Warren et al. (1999) showed \r\nthat over 1954-1991 there were weak trends towards declining snow \r\ndepth on sea ice in the Pacific sector. Recent observations indicate \r\na substantial thinning of the spring snowpack in the western Arctic \r\n(Cavalieri et al., 2012; Brucker and Markus, 2013; Kurtz et al., 2013; \r\nLaxon et al., 2013; Webster et al., 2018). In contrast, thick snow over \r\nArctic sea ice in the Atlantic sector north of Svalbard (snow thickness \r\naround 0.4 m or more) has been observed in the 1970s and since the \r\n1990s (Rosel et al., 2018), but data are too sparse to detect trends. "


id: c0e24d0427cdab7bf4231dfbfddac1aa
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 31232
content:
"In summary, over 1979-2019 Arctic SIA has decreased for all months, \r\nwith the strongest decrease in summer (very high confidence). \r\nDecadal means for SIA decreased from the first to the last decade \r\nin that period from 6.23 to 3.76 million km2 for September, and from \r\n14.52 to 13.42 million km2 for March. Arctic sea ice has become \r\nyounger, thinner and faster moving (very high confidence). Snow \r\nthickness on sea ice has decreased in the western Arctic Ocean \r\n(medium confidence). Since the Younger Dryas at the end of the LDT, \r\nproxy indicators show that Arctic sea ice has fluctuated on multiple \r\ntime scales with a decrease in sea ice coverage during the Early \r\nHolocene and an increase from the MH to the mid-15th century. \r\nCurrent pan-Arctic sea ice coverage levels (annual mean and late \r\nsummer) are unprecedentedly low since 1850 (high confidence), and \r\nwith medium confidence for late summer for at least the past 1 kyr. "


id: 5dc38997bf8d6ce6dd70be57829cb55d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13787
content:
"The AR5 reported a small but significant increase in the total annual \r\nmean Antarctic SIE that was very likely in the range of 1.2-1.8% per \r\ndecade between 1979 and 2012 (0.13-0.20 million km2 per decade) \r\n(very high confidence), while SROCC reported that total Antarctic sea \r\nice coverage exhibited no significant trend over the period of satellite \r\nobservations (1979-2018) (high confidence). The SROCC noted that \r\na significant positive trend in mean annual sea ice cover between \r\n1979 and 2015 had not persisted, due to three consecutive years of \r\nbelow-average sea ice cover (2016-2018). The SROCC stated also \r\nthat historical Antarctic sea ice data from different sources indicated a \r\ndecrease in overall Antarctic sea ice cover since the early 1960s, but was \r\ntoo small to be separated from natural variability (high confidence)."


id: c725defa300876f6222d358b71b9b046
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 32357
content:
"There is only limited evidence from predominantly regional paleo \r\nproxies for the evolution of Southern Ocean sea ice before the \r\ninstrumental record and estimates are not available for all proxy \r\ntarget periods (Section 9.3.2). Proxies from marine sediments for \r\nintervals preceding and following the MPWP indicate open water \r\nconditions with less sea ice than modern conditions (Taylor-Silva and \r\nRiesselman, 2018; Ishino and Suto, 2020). During the LGM, proxies \r\nindicate that austral winter sea ice coverage reached the polar ocean \r\nfront (e.g., Nair et al., 2019). More recently, sea ice coverage appears \r\nto have fluctuated substantially throughout the Holocene (e.g., for the \r\nwestern Amundsen Sea, Lamping et al., 2020). At the beginning of the \r\nCE, regional summer sea ice coverage in the north-western Ross Sea \r\nwas lower than today (Tesi et al., 2020). Crosta et al. (2021) suggest, \r\nbased on different proxies, four different phases with 7-10 months "


id: 9d125f829375c3425e0acddf22c71e5c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 24873
content:
"periods of sea ice occurrence per year in the Antarctic region off Adelie \r\nLand during the CE, where each phase was several hundred years long. "


id: 29bc0b925189e780a10cc71c5ba172db
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 4567
content:
"In summary, Antarctic sea ice has experienced both increases and \r\ndecreases in SIA over 1979-2019, and substantively lower levels \r\nsince 2016, with only minor differences between decadal means \r\nof SIA for the first (for February 2.04 million km2, for September \r\n15.39 million km2) and last decades (for February 2.17 million km2, \r\nfor September 15.75 million km2) of satellite observations (high \r\nconfidence). There remains low confidence in all aspects of Antarctic \r\nsea ice prior to the satellite era owing to a paucity of records that are \r\nhighly regional in nature and often seemingly contradictory."


id: c247a14c3f746845bddaa83347a9e796
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 31465
content:
"The AR5 concluded that snow cover extent (SCE) had decreased in the \r\nNH, especially in spring (very high confidence). For 1967-2012, the \r\nlargest change was in June and March-April SCE very likely declined. \r\nNo trends were identified for the SH due to limited records and large \r\nvariability. The SROCC concluded with high confidence that Arctic \r\nJune SCE declined between 1967 and 2018 and in nearly all mountain \r\nregions, snow cover declined in recent decades."


id: 5b1e6bf1fe6657086660bbef644b9889
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13281
content:
"mass, although there were considerable inter-annual and regional \r\nvariations. Between 2006 and 2015 the global glacier mass change \r\nassessed by SROCC was -278 +- 113 Gt yr-1. "


id: f97c9875bf1e314fe95f77b75931208b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41260
content:
"There has been a commensurate decrease in the snow-cover duration \r\nand persistence, particularly in higher latitudes due to earlier \r\nspring melt and, in some cases, later autumn onset of snow cover \r\n(Chen et al., 2015; Derksen et al., 2015; Hori et al., 2017; Hammond \r\net al., 2018). Arctic snow-cover duration has decreased by 2-4 days \r\nper decade since the 1970s (Brown et al., 2017). Significant decreases \r\nin snow-cover duration have been documented over western Eurasia \r\nsince 1978 (Hori et al., 2017). "


id: b44d47d9194a6001bd6806328ea20d3b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 28955
content:
"For the NH, maximum snow depth has generally decreased since \r\nthe 1960s, with more robust trends for North America and greater \r\nuncertainty for Eurasia (Kunkel et al., 2016). Several satellite-based \r\npassive microwave and other products indicate general declines in \r\npre-melt snow water equivalent since 1981 although there is regional \r\nand inter-dataset variability (Brown et al., 2017; Jeong et al., 2017; \r\nMarty et  al., 2017; Mortimer et  al., 2020; Mudryk et  al., 2020; \r\nPulliainen et al., 2020, Section 9.5.3). "


id: 56e9541074b26971f59b9263de496b2f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12540
content:
"In summary, substantial reductions in spring snow cover extent have \r\noccurred in the NH since 1978 (very high confidence) with limited \r\nevidence that this decline extends back to the early 20th century. \r\nSince 1981 there has been a general decline in NH spring snow water \r\nequivalent (high confidence)."


id: be47b48c1a054cdecde393ac1843ed46
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30743
content:
"The AR5 concluded with high confidence that, during the Holocene, \r\nglaciers were at times smaller than at the end of the 20th century. \r\nThe AR5 stated further with very high confidence that most glaciers \r\nhad been shrinking since the mid-1800s, and the mass loss from \r\nall glaciers worldwide very likely increased from 1970 to 2009. The \r\nSROCC reported a globally coherent picture of continued glacier \r\nrecession in recent decades (very high confidence) based on in situ \r\nand satellite observations of changes in glacier area, length and "


id: 39f1abaa11a1553905198429f81d9b9c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 7405
content:
"Figure 2.23 | Mountain glacier advance and annual mass change. (a) Number of a finite selection of surveyed glaciers that advanced during the past 2000 years. \r\n(b) Annual and decadal global glacier mass change (Gt yr-1) from 1961 until 2018. In addition, mass change mean estimates are shown. Ranges show the 90% confidence \r\ninterval. Further details on data sources and processing are available in the chapter data table (Table 2.SM.1)."


id: 95c7e3562a0f6773f25361b1a361b3bc
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 23543
content:
"In summary, there is very high confidence that, with few \r\nexceptions, glaciers worldwide have retreated since the second \r\nhalf of the 19th century, and continue to retreat. The current global \r\ncharacter of glacier mass loss is highly unusual (almost all glaciers \r\nsimultaneously receding) in the context of at least the last 2 kyr \r\n(medium confidence). Glacier mass loss rates have increased since \r\nthe 1970s (high confidence). Although many surveyed glaciers are \r\ncurrently more extensive than during the MH (high confidence), \r\nthey generally are in disequilibrium with respect to current climate \r\nconditions and hence are committed to further ice loss. "


id: 6d362de2ee2ab5f9fddee3b2eb7c023a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16491
content:
"Recent studies of marine and lake sediments, glacier ice, and \r\ngeomorphic features show that the GrIS retreated rapidly during the \r\nearly Holocene but halted periodically, with a complex ice-margin \r\nchronology (Carlson et al., 2014; Larsen et al., 2014, 2015; Young and \r\nBriner, 2015; Briner et al., 2016; Young et al., 2020). It is probable that \r\nits total volume during 8-3 ka was smaller than today (Larsen et al., \r\n2015; Young and Briner, 2015; Briner et al., 2016), but uncertainties \r\nexist regarding precisely when the minimum MH extent and volume \r\nwas reached, due to uncertainties in reconstructions. The GrIS then \r\nre-advanced reaching its maximum extent in most places during \r\n1450-1850 CE, although the timing and extent of this maximum \r\ndiffered by sector (Larsen et al., 2015; Briner et al., 2016)."


id: 858fcd8d31947825e33babd269d33570
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20638
content:
"During glacial periods, ice sheets were more extensive and the state \r\nof knowledge on their paleo-reconstruction can be found in recent \r\npublications (e.g.,  Stokes et  al., 2015; Batchelor et  al., 2019). This \r\nsection focuses only on the large-scale aspects of those ice sheets, \r\nGreenland and Antarctic, that still exist today. "


id: 8cde4841334e73cbace1a77a87bbbc03
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 21970
content:
"Greenland-wide estimates of mass change based on direct observations \r\nwere limited prior to 1992 at the time of AR5 (Kjeldsen et al., 2015). \r\nCombined records based on airborne observations, model-based \r\nestimates and geodetic approaches indicate an average mass loss of \r\n75 +- 29.4 Gt yr-1 for 1900-1983 (Kjeldsen et al., 2015). Integration \r\nof proxies and modelling indicates that the last time the rate of mass \r\nloss of the GrIS was plausibly similar to 20th century rates was during \r\nthe early Holocene (Buizert et al., 2018; Briner et al., 2020)."


id: 4e42880439b003cbad4174b837d8e21f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
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index: climate_gpt_v2
vector_id: 11039
content:
"The AR5 concluded the volume of the Greenland Ice Sheet (GrIS) was \r\nreduced compared to present during periods of the past few million \r\nyears that were globally warmer than present (high confidence). \r\nIt reported that the GrIS had lost ice during the prior two decades \r\n(very high confidence), that the ice loss had occurred in several sectors, \r\nand that high rates of mass loss had both expanded to higher elevations \r\n(high confidence) and very likely accelerated since 1992. The SROCC \r\nconcluded that it was extremely likely that ice loss increased through \r\nthe early 21st century. The SROCC also found that summer melting \r\nrate had increased since the 1990s to a rate unprecedented over the \r\nlast 350 years (very high confidence), being two to five times greater \r\nthan the pre-industrial rates (medium confidence)."


id: 5206462a7a98490fc21dfd9b0c5d4747
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11706
content:
"Since AR5, a combination of remote sensing, in situ observations and \r\nmodelling has provided new insights regarding surface processes and \r\ntheir contribution to recent GrIS mass changes (AMAP, 2017; van den \r\nBroeke et al., 2017; Bamber et al., 2018; Mouginot et al., 2019; IMBIE \r\nConsortium, 2020; Khan et al., 2020). Estimates of total ice loss during \r\nthe post-1850 period (Kjeldsen et al., 2015) and recent observations \r\nshow that the rate of loss has increased since the beginning of the \r\n21st century (IMBIE Consortium, 2020; Sasgen et al., 2020; Velicogna \r\net al., 2020) (Section 9.4.1.1 and Figures 2.24 and 9.17)."


id: 78a67bc6cb70a9939d25bcb1cab2fc6b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 18420
content:
"Details of the history of the GrIS fluctuations during warm \r\ninterglacials continue to be elucidated. Oscillations over the past \r\n7.5 Myr, including the Pliocene and through the glacial - interglacial \r\ncycles of the Pleistocene are not well-constrained, but most studies \r\nindicate that Greenland was at least partially glaciated over this "


id: fe81752e121c3450d79599e66e4d4e34
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 42149
content:
"The GrIS lost 4890 [4140 to 5640] Gt (SLE 13.5 [11.4 to 15.6] mm) \r\nof ice between 1992 and 2020 (Section 9.4.1 and Figure 2.24; IMBIE \r\nConsortium, 2020). The ice sheet was close to mass balance in the 1990s, "


id: 799ec9af4a67c033ff15f0d3ac7ff3cc
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 18602
content:
"de Boer et al., 2015; DeConto and Pollard, 2016; Levy et al., 2016). \r\nResults from sediment studies suggest a smaller AIS during the \r\nMPWP compared with current levels, with main differences in the \r\nWAIS (Section 9.6.2; SROCC, IPCC, 2019; Bertram et  al., 2018; \r\nShakun et  al., 2018). Marine sediments indicate that during the \r\nPleistocene repeated ungrounding and loss of large marine-based \r\nparts of the AIS occurred during interglacial periods, with at least \r\nseven transitions between floating and grounded ice in the Ross \r\nSea during the last 780 kyr (McKay et al., 2012) and at least three \r\nreductions in ice volume in the Wilkes Basin during the last 500 kyr \r\n(Wilson et al., 2018). Proxies, modelling and process understanding \r\n(Rohling et  al.,  2019; Clark et  al., 2020) indicate that the AIS was \r\nsmaller during the LIG than present. "


id: 79521e944cc6e38610870e362cd3b022
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 18540
content:
"but increases in mass loss have occurred since (Bamber et al., 2018; \r\nWCRP Global Sea Level Budget Group, 2018; Mouginot et al., 2019; \r\nIMBIE Consortium, 2020). The rate of ice-sheet (including peripheral \r\nglaciers) mass loss rose from 120 [70  to  170]  Gt  yr-1 (SLE  0.33 \r\n[0.18  to  0.47] mm yr-1) in 1901-1990 to 330 [290 to 370] Gt  yr-1\r\n(SLE  0.91 [0.79 to 1.02] mm yr-1) for 2006-2018 (Section  9.4.1, \r\nTable 9.5)."


id: e11504e66e03c497c6c30959b73eff03
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 36865
content:
"In summary, the GrIS was smaller than present during the MPWP \r\n(medium confidence), LIG (high confidence) and the MH (high \r\nconfidence). GrIS mass loss began following a peak volume attained \r\nduring the 1450-1850 period and the rate of loss has increased \r\nsubstantially since the turn of the 21st century (high confidence)."


id: f7acb51a4491d3b76861e6d2774c2c7c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 40946
content:
"The AR5 reported that there was high confidence that the Antarctic \r\nIce Sheet (AIS) was losing mass. The average ice mass loss from \r\nAntarctica was 97 [58 to 135] Gt yr-1 (GMSL equivalent of 0.27 \r\n[0.16 to 0.37] mm yr-1) over 1993-2010, and 147 [74 to 221] Gt yr-1\r\n(0.41 [0.20 to 0.61] mm yr-1) over 2005-2010. These assessments \r\nincluded the Antarctic peripheral glaciers. The AR5 reported with high \r\nconfidence that the volume of the West Antarctic Ice Sheet (WAIS) \r\nwas reduced during warm periods of the past few million years. The \r\nSROCC concluded that over 2006-2015, the AIS lost mass at an \r\naverage rate of 155 +- 19 Gt yr-1 (very high confidence). The SROCC \r\nalso stated that it is virtually certain that the Antarctic Peninsula \r\nand WAIS combined have cumulatively lost mass since widespread \r\nmeasurements began in 1992, and that the rate of loss has increased \r\nsince around 2006."


id: f36fae955a3729b8cd23c19806300ed2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 40204
content:
"Process understanding and, to some extent, paleoclimate records \r\nshow that changes in parts of the AIS can occur over multi-century \r\ntime scales (<2kyr; Sections 9.4.2.3 and 9.6.2; e.g.,  Dowdeswell \r\net al., 2020). Based on physical understanding, paleo evidence and \r\nnumerical simulations, it is very likely that the AIS has been smaller \r\nthan today during at least some past warm climates (such as MCO \r\nand LIG), in particular the WAIS (Figure 9.18; Golledge et al., 2014; "


id: 258032f3035e21b03b9e448f4b21fb7b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 3783
content:
"balance is not significantly different from zero (Bamber et al., 2018; \r\nIMBIE Consortium, 2018; Mohajerani et al., 2018; Rignot et al., 2019)."


id: 65f2d2614b12ae93152493315de794c6
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 15197
content:
"In summary, the AIS has lost mass between 1992 and 2020 (very high \r\nconfidence), and there is medium confidence that this mass loss has \r\nincreased. During the MPWP and LIG, the ice sheet was smaller than \r\npresent (medium confidence). There is low confidence as to whether \r\nthe total mass of the ice sheet was larger or smaller around 6 ka \r\ncompared to now."


id: 8d818973096a830fb1261fa258ab128e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 22084
content:
"The AR5 concluded that in most regions and at most monitoring \r\nsites permafrost temperatures since the 1980s had increased (high \r\nconfidence). Negligible change was observed at a few sites, mainly \r\nwhere permafrost temperatures were close to 0degC, with slight cooling \r\nat a limited number of sites. The AR5 also noted positive trends in \r\nactive layer thickness (ALT; the seasonally thawed layer above the \r\npermafrost) since the 1990s for many high latitude sites (medium \r\nconfidence). The SROCC concluded permafrost temperatures have \r\nincreased to record high levels since the 1980s (very high confidence) \r\nwith a recent increase by 0.29degC +- 0.12degC from 2007 to 2016 \r\naveraged across polar and high mountain regions globally."


id: 994eac45e4644c1d4bcd5b2722c05f52
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 24193
content:
"is minimal) were the highest ever directly observed at most sites \r\n(Romanovsky et al., 2020), with temperatures in colder permafrost \r\nof northern North America being more than 1degC higher than they \r\nwere in 1978. Increases in temperature of colder Arctic permafrost \r\nare larger (average 0.4degC-0.6degC per decade) than for warmer \r\n(temperature >-2degC) permafrost (average 0.17degC per decade) of \r\nsub-Arctic regions (Figures 2.25, 9.22). "


id: 590ac873abc1f22c3d313bdae13c3f7
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12907
content:
"Increases in permafrost temperature over the last 10-30 years of \r\nup to 0.3degC per decade have been documented at depths of about \r\n20 m in high elevation regions in the NH (European Alps, the Tibetan \r\nPlateau and some other high elevation areas in Asia; G. Liu et al., \r\n2017; Cao et al., 2018; Biskaborn et al., 2019; Noetzli et al., 2020; \r\nZhao et al., 2020). In Antarctica, where records are limited and short \r\n(most <10 years) trends are less evident (Noetzli et al., 2019)."


id: ad08333867241de7604e9167d126bf9a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 27681
content:
"Records of permafrost temperature measured in several boreholes \r\nlocated throughout the northern polar regions indicate general \r\nwarming of permafrost over the last 3-4 decades (Figure 2.25), \r\nwith marked regional variations (Romanovsky et al., 2017a, b, 2020; \r\nBiskaborn et al., 2019). Recent (2018-2019) permafrost temperatures \r\nin the upper 20-30 m layer (at depths where seasonal variation "


id: 7328b13b08017f96d689467fe1c0a8e1
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17509
content:
"Observations of ground subsidence and other landscape change \r\n(e.g.,  thermokarst, slope instability) since the middle of the \r\n20th  century in the Arctic associated with ground ice melting \r\nhave been documented in several studies and provide additional \r\nindications of thawing permafrost (Sejourne et  al., 2015; Liljedahl \r\net al., 2016; Borge et al., 2017; Kokelj et al., 2017; Nitze et al., 2017; \r\nStreletskiy et al., 2017; Derksen et al., 2019; Farquharson et al., 2019; \r\nLewkowicz and Way, 2019; O'Neill et al., 2019; see Section 9.5.2.1). \r\nIn mountain areas, destabilization and acceleration of rock glacier \r\ncomplexes that may be associated with warming permafrost have \r\nalso been observed (Eriksen et al., 2018; Marcer et al., 2019)."


id: a89df69c4666191c0709eafa740858d4
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 26874
content:
"In summary, increases in permafrost temperatures in the upper 30 m \r\nhave been observed since the start of observational programs over \r\nthe past three to four decades throughout the permafrost regions \r\n(high confidence). Limited evidence suggests that permafrost was \r\nless extensive during the MPWP (low confidence). Permafrost that \r\nformed after 3ka still persists in areas of the NH, but there are \r\nindications of thaw after the mid-1800s (medium confidence)."


id: b31492b1b143a10575d2ac0c4200e263
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 28749
content:
"This section focuses on large-scale changes in a subset of physical \r\ncomponents of the ocean (Cross-Chapter Box 2.2). Chapter 7 assesses \r\nthe role of the ocean in Earth system heating and evaluates the Earth's \r\nenergy budget. Chapter 9 undertakes a holistic assessment of changes \r\nin the ocean integrating observations, modelling and theoretical \r\nunderstanding. Chapter 11 assesses extremes such as marine heat \r\nwaves and storm surges. SSTs are assessed in Section 2.3.1.1 as they \r\nconstitute a critical component of GMST estimation. "


id: be701c78238aef0931ec458d63678c88
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30768
content:
"AR5 assessed that since 1971, global ocean warming was virtually \r\ncertain for the upper 700 m and likely for the 700-2000 m layer. \r\nThe SROCC reported linear warming trends for the 0-700 m and \r\n700-2000 m layers of the ocean, respectively, of 4.35 +- 0.8 and 2.25 \r\n+- 0.64 ZJ yr-1 over 1970-2017; 6.28 +- 0.48 and 3.86 +- 2.09 ZJ yr-1\r\nover 1993-2017; and 5.31 +- 0.48 and 4.02 +- 0.97 ZJ yr-1 over 2005-\r\n2017. Both AR5 and SROCC assessed that the ocean below 2000 \r\nm had likely warmed since 1992. The SROCC reported global mean \r\nthermosteric sea level (ThSL) rise, associated with thermal expansion \r\nof the ocean, with a trend of 0.89 +- 0.05 mm yr-1 for 1970-2015; \r\n1.36 +- 0.40 mm yr-1 for 1993-2015; and 1.40 +- 0.40 mm yr-1 for \r\n2006-2015, and also reported that the rate of ocean warming over \r\n1993-2017 had likely more than doubled since 1969-1992."


id: 9babbf0e585bb9bed3480fef53e94293
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 24641
content:
"New ocean heat content (OHC) reconstructions derived from paleo \r\nproxies (Bereiter et  al., 2018; Baggenstos et  al., 2019; Shackleton \r\net al., 2019; Gebbie, 2021) indicate that the global ocean warmed by \r\n2.57degC +- 0.24degC, at an average rate of about 0.3degC ka-1 (equivalent \r\nto an OHC change rate of 1.3 ZJ yr -1) from the LGM (about 20 ka) to \r\nthe early Holocene (about 10 ka; Section 9.2.2.1 and Figure 9.9). Over \r\nthe LDT, ocean warming occurred in two stages, offset by some heat \r\nloss during the Antarctic Cold Reversal (14.58-12.75 ka). Only during "


id: ff6e4491d1b995be912ae638d8e4f356
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 42344
content:
"Collectively, the new and updated analyses strengthen AR5 and \r\nSROCC findings of a sustained increase in global OHC (Figure 2.26 \r\nand Table 2.7) and associated ThSL rise. Larger warming rates are \r\nobserved in the upper 700 m compared to deeper layers, with \r\nmore areas exhibiting significant warming than significant cooling \r\n(Johnson and Lyman, 2020). There is an improved consistency among "


id: c27cb1e5190c35bbab19da2e4fb0ba18
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 31502
content:
"available estimates of OHC rates in the upper 2000 m since 2006. \r\nCheng et al. (2020), von Schuckmann et al. (2020) and Johnson et al. \r\n(2020) have further confirmed that the central estimates of rates of \r\nOHC change in the upper 2000 m depths have increased after 1993 \r\nand particularly since 2010 (Section 3.5.1.3 and Figures 2.26 and \r\n3.26), although uncertainties are large (Table 2.7). Ocean reanalyses \r\nsupport findings of continued upper ocean warming (Balmaseda \r\net al., 2013; von Schuckmann et al., 2018; Meyssignac et al., 2019), \r\nalbeit with higher spread than solely observational estimates, \r\nparticularly in the poorly sampled deep ocean below 2000 m (Storto \r\net al., 2017; Palmer et al., 2018). "


id: 2f8739295094cdc95b8082b0dfbcb58b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 5624
content:
"In summary, current multi-decadal to centennial rates of OHC \r\ngain are greater than at any point since the last deglaciation \r\n(medium confidence). At multi-centennial timescales, changes in OHC \r\nbased upon proxy indicators demonstrate a tight link with surface \r\ntemperature changes during the last deglaciation (high confidence), \r\nas well as during the Holocene and CE (low confidence). It is likely the \r\nglobal ocean has warmed since 1871, consistent with the observed \r\nincrease in sea surface temperature. It is virtually certain that OHC \r\nincreased between 1971 and 2018 in the upper 700 m and very \r\nlikely in the 700-2000 m layer, with high confidence since 2006. It is \r\nlikely the OHC below 2000 m has increased since 1992. Confidence in \r\nthe assessment of multi-decadal OHC increase is further strengthened \r\nby consistent closure of both global sea level and energy budgets \r\n(Section 7.2.2.2, Box 7.2, Cross-Chapter Box 9.1)."


id: c4bba97d04af03eb6f6ae538d198b661
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 31929
content:
"had very likely become fresher since the 1950s, both at the near\u0002surface, and in the ocean interior along ventilation pathways. From \r\n1950 to 2008, the mean surface contrast between high- and low\u0002salinity regions increased by 0.13 [0.08 to 0.17] (PSS-78, UNESCO/\r\nICES/SCOR/IAPSO, 1981). Across basins, the Atlantic Ocean had "


id: 441e07c0909f4ec715a0a35a26203f13
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 9223
content:
"average, with freshening in subpolar regions and salinification in the \r\nsubtropical gyres (Durack and Wijffels, 2010; Good et al., 2013; Skliris \r\net  al., 2014; Durack, 2015; Aretxabaleta et  al., 2017; Cheng et  al., \r\n2020). Regional changes in salinity are assessed in Section 9.2.2.2."


id: 87503082523675b2e4e32f1884cedf98
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20968
content:
"In summary, it is virtually certain that since 1950 near-surface high \r\nsalinity regions have become more saline, while low salinity regions \r\nhave become fresher, and it is very likely that this extends to the ocean \r\ninterior along ventilation pathways. Across basins, it is very likely that \r\nthe Atlantic has become saltier and the Pacific and Southern oceans \r\nhave freshened. The differences between high-salinity and low\u0002salinity regions are linked to an intensification of the hydrological \r\ncycle (medium confidence). "


id: d068359e281cd29cc7cbc0bf4503e3cb
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 34019
content:
"Since AR5, new and extended multi-decadal analyses have \r\nstrengthened the observational support for increased contrast \r\nbetween high and low near-surface salinity regions and inter-basin \r\ncontrast since the mid-20th century (Section 9.2.2.2; Durack and \r\nWijffels, 2010; Good et  al., 2013; Skliris et  al., 2014; Aretxabaleta \r\net  al., 2017; Cheng et  al., 2020). These analyses employ different \r\nstatistical algorithms for interpolation, and only Cheng et al. (2020) \r\nuse CMIP5 model simulations to constrain observation-based signals \r\nin data-sparse regions."


id: 3ba0f381eb678640a05043ff8cecd12a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 7675
content:
"Changes in the global patterns of near-surface salinity contrast \r\nare transferred to the ocean interior via ventilation pathways \r\n(Figure 2.27b). Large scale similarities in subsurface salinity changes \r\nacross observational estimates point to decreasing (increasing) \r\nsalinity in regions where salinity is lower (higher) than the global "


id: 53e302d5593618110773b509ea4d4a0e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12031
content:
"Few sites globally have well-preserved MIS 11 sea-level indicators \r\n(Dutton et al., 2015). As reported in AR5, Raymo and Mitrovica (2012) \r\nused glacial isostatic adjustment models to correct the elevation of \r\nMIS 11 sea-level proxies from Bermuda and Bahamas to estimate \r\na peak MIS 11 GMSL between 6 and 13 m above present-day. This \r\nagrees with the elevation of 13 +- 2 m for the MIS 11 subtidal-intertidal \r\ntransition in South Africa (Roberts et  al., 2012). A  revised glacial \r\nisostatic adjustment at this location resulted in a peak GMSL estimate \r\nof 8-11.5 m (Chen et al., 2014). In light of these data, and the review \r\nby Dutton et al. (2015), the AR5 estimate of 6-13 m for MIS 11 remains \r\nthe best available (medium confidence)."


id: 6ae638ce920b4947785faf75c270b22c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16092
content:
"The Earth was largely ice free during the EECO (Cramer et al., 2011; \r\nMiller et al., 2020, Section 9.6.2), and complete loss of current land \r\nice reservoirs would raise GMSL by 65.6 +- 1.8 m (Morlighem et al., \r\n2017, 2020; Farinotti et al., 2019). Given that GMSL change must be \r\ndue to some combination of transient land ice growth and changes \r\nin terrestrial water storage, additional global mean thermosteric \r\nsea-level increase of 7 +- 2 m (Fischer et al., 2018) implies a peak \r\nEECO GMSL of 70-76 m (low confidence). Changes in ocean basin \r\nsize driven by plate tectonics contributed a comparable amount to \r\nglobal mean geocentric sea level in the Eocene, but are definitionally \r\nexcluded from GMSL assessment (Wright et al., 2020)."


id: 94f82668e44f40bb8929f4718f823c1d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 23414
content:
"New geological proxies and glacial isostatic adjustment (GIA) \r\nmodelling studies confirm that, at the LGM, GMSL was 125-134 m \r\nbelow present (Lambeck et al., 2014; Yokoyama et al., 2018). During \r\nthe LDT, GMSL rose from approximately -120 m to -50 m, implying an \r\naverage rate of about 10 mm yr-1 (Lambeck et al., 2014). The fastest \r\nrise occurred during Meltwater Pulse 1A, at about 14.6-14.3  ka \r\n(Deschamps et al., 2012; Sanborn et al., 2017), when GMSL rose by \r\nbetween 8 m and 15 m (medium confidence) (J. Liu et al., 2016) at an \r\naverage rate of 24-44 mm yr-1. "


id: 4dd780bc1e7cc81afdd31fe91a1b3fba
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 10963
content:
"For the MPWP, several studies of coastal features have provided \r\nadditional quantitative sea-level estimates of: 5.6-19.2 m from \r\nSpain (Dumitru et al., 2019), approximately 14 m from South Africa \r\n(Hearty et  al., 2020), 15 m from the United States (Moucha and \r\nRuetenik, 2017), and 25 m from New Zealand (Grant et al., 2019). \r\nThus, consistent with SROCC, GMSL during the MPWP was higher \r\nthan present by 5-25 m (medium confidence)."


id: 93049e93190af6105863d9642e666ae4
created_at: 2023-04-19 13:21:33
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index: climate_gpt_v2
vector_id: 23075
content:
"Reconstructions of GMSL from marine oxygen isotopes in foraminifera \r\nshells show variations of more than 100 m over intervals of 10-100 kyr \r\nduring glacial-interglacial cycles of the Quaternary (Shackleton, 1987; \r\nMcManus et  al., 1999; Waelbroeck et  al., 2002; Miller et  al., 2020). \r\nCorrection for past temperatures and a calibration for ice-volume \r\nchanges implies uncertainty estimates of +- 10-13 m (1 SD) (Grant \r\net al., 2014; Shakun et al., 2015; Spratt and Lisiecki, 2016). A recent \r\nmarine oxygen-isotope-based GMSL reconstruction (Spratt and Lisiecki, \r\n2016) agrees with previous reconstructions, while focusing on the past \r\n800 kyr (Figure 2.28). It shows that GMSL during the Holocene was \r\namong the highest over this entire interval, and was surpassed only \r\nduring the LIG (Marine Isotope Stage (MIS 5e)) and MIS 11 (medium \r\nconfidence); however, relatively brief (about 2 kyr) highstands during \r\nother interglacial periods might be obscured by dating limitations."


id: 2b3b20184263e98dc7f7aede51a4dd4a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 4850
content:
"Recent GIA modelling studies tuned to both near- and far-field relative \r\nsea level (RSL) data yield MH GMSL estimates of -3.8 to -1.0  m \r\n(Lambeck et al., 2014; Peltier et al., 2015; Bradley et al., 2016; Roy \r\nand Peltier, 2017). Estimates from relatively stable locations where \r\nthe effects of GIA are small and relatively insensitive to parameters \r\ndefining Earth rheology, and where RSL is expected to approximate \r\nGMSL to within about 1 m (e.g., Milne and Mitrovica, 2008), suggest \r\nthat RSL was between about -6 to +1.5 m at around 6 ka at multiple \r\nlocations (Camoin et al., 1997; Braithwaite et al., 2000; Frank et al., \r\n2006; Montaggioni and Faure, 2008; Vacchi et al., 2016; Khan et al., \r\n2017; Hibbert et al., 2018). The assessment of GMSL change at 6 kyr \r\nis challenging considering the proportionately large GIA effect (Kopp \r\net al., 2016), insufficient resolution of marine geochemical proxies "


id: 3efb7df97217d11a5a460d8fa742abd2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 8270
content:
"(d18O, Mg/Ca) and uncertainties in the contribution of the Antarctic \r\nIce Sheet during the MH (Section 2.3.2.4). The possibility that GMSL \r\nwas at least somewhat higher than present cannot be excluded."


id: 31cd17b61e03d54dc9337659ab799e20
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6008
content:
"salt-marsh records with decimetre scale vertical resolution and sub\u0002centennial temporal resolution (Kopp et al., 2016; Kemp et al., 2018). \r\nOver the last about 1.5 kyr, the most prominent century-scale GMSL \r\ntrends include average maximum rates of lowering and rising of \r\n-0.7 +- 0.5 mm yr-1 (2 SD) over 1020-1120 CE, and 0.3 +- 0.5 (2 SD) \r\nover 1460-1560, respectively. Between 1000 and 1750 CE, GMSL is "


id: 9024b08117063217ff81b4d28fa5650f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 22569
content:
"Figure 2.28 | Changes in global mean sea level. (a) Reconstruction of sea-level from ice core oxygen isotope analysis for the last 800 kyr. For target paleo periods (CCB2.1) \r\nand MIS11 the estimates based upon a broader range of sources are given as box whiskers. Note the much broader axis range (200 m) than for later panels (tenths of metres). \r\n(b) Reconstructions for the last 2500 years based upon a range of proxy sources with direct instrumental records superposed since the late 19th century. (c) Tide-gauge and, more \r\nlatterly, altimeter-based estimates since 1850. The consensus estimate used in various calculations in Chapters 7 and 9 is shown in black. (d) The most recent period of record from \r\ntide-gauge and altimeter-based records. Further details on data sources and processing are available in the chapter data table (Table 2.SM.1)."


id: 6c28f50e3276e0d486d8e8a3dd5bbf63
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16326
content:
"emerging evidence in sustained observations, both in situ (2004-2017) \r\nand revealed from SST-based reconstructions, that the AMOC had \r\nweakened during the instrumental era relative to 1850-1900 (medium \r\nconfidence), although there were insufficient data to quantify the \r\nmagnitude of the weakening. SROCC also concluded with low \r\nconfidence an increase of the Southern Ocean upper cell overturning \r\ncirculation. SROCC also reported with medium confidence that the \r\nproduction of Antarctic Bottom Water had decreased since the 1950s \r\nconsistent with a decreased lower cell overturning circulation, and \r\npotentially modulating the strength of the AMOC."


id: eb84d642726682a191aa792d80927429
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 38795
content:
"estimated to have been within the range of about -0.11 to +0.09 m \r\nrelative to 1900 (Kemp et al., 2018). This was followed by a sustained \r\nincrease of GMSL that began between 1820 and 1860 and has \r\ncontinued to the present day. New analyses demonstrate that it is very \r\nlikely that GMSL rise over the 20th century was faster than over any \r\npreceding century in at least 3 kyr (Kopp et al., 2016; Kemp et al., 2018) \r\n(Figure 2.28). "


id: ca3a2467970ef571a93fd34e4fda2812
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 32919
content:
"Numerous proxy records collectively imply that AMOC is currently at \r\nits weakest point in the past 1.6 ka (Rahmstorf et al., 2015; Caesar \r\net al., 2018, 2021; Thibodeau et al., 2018; Thornalley et al., 2018). \r\nCaesar et al. (2021) analyse a compilation of various available indirect \r\nAMOC proxies from marine sediments, in situ-based reconstructions \r\nand terrestrial proxies, which show a decline beginning in the late \r\n19th century and over the 20th century superimposed by large \r\ndecadal variability in the second half of the 20th century. Indirect \r\nreconstructions of AMOC components based on coastal sea level \r\nrecords in the western North Atlantic (Ezer, 2013; McCarthy et al., \r\n2015; Piecuch, 2020) show an AMOC decline since the late 1950s, \r\nwith only a short period of recovery during the 1990s."


id: b1af60e1471e83d12b9a55edb92e8b7d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 28478
content:
"In summary, GMSL is rising, and the rate of GMSL rise since the \r\n20th century is faster than over any preceding century in at least the \r\nlast three millennia (high confidence). Since 1901, GMSL has risen by \r\n0.20 [0.15 to 0.25] m at an accelerating rate. Further back in time, there \r\nis medium confidence that GMSL was within -3.5 to +0.5 m (very likely \r\nrange) of present during the MH, 5-10 m higher (likely range) during \r\nthe LIG, and 5-25 m higher (very likely range) during the MPWP."


id: 4750da91b2edabb1924c4777e03077eb
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 9754
content:
"The AR5 concluded that there was no evidence of a trend in the \r\nAMOC during the period of instrumental observations. However, AR5 \r\nalso stressed insufficient evidence to support a finding of change \r\nin the heat transport of the AMOC. SROCC assessed that there was "


id: 755cb6519a41017f3ae0c60c26daeffe
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17874
content:
"However, other studies highlight that proxy records do not show such \r\nclear signals (Moffa-Sanchez et  al., 2019), and the use of SST- and \r\ncoastal sea level-based proxies of AMOC places uncertainties on these \r\nresults (Little et al., 2019; Jackson and Wood, 2020; Menary et al., 2020). "


id: 25e615f839ae9ad08f9d3eb633bbb1b2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 3847
content:
"(high confidence) cannot be distinguished between decadal-scale \r\nvariability or a long-term trend (high confidence)."


id: 9e423abe4701b69ade2c850f68d40582
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 25072
content:
"For instance, SSTs are additionally influenced by atmospheric and \r\nnon-AMOC related ocean variability (Josey et al., 2018; Keil et al., 2020; \r\nMenary et al., 2020), while sea level responds to a variety of factors \r\n(e.g., atmospheric pressure and local winds) independent of the AMOC \r\n(Woodworth et al., 2014; Piecuch and Ponte, 2015; Piecuch et al., 2016). \r\nFinally, large decadal variability is present in many reconstructions and \r\nobscures estimation of the long-term trend over the 20th century (Ezer, \r\n2013; McCarthy et al., 2015; Yashayaev and Loder, 2016; Thornalley \r\net al., 2018; Caesar et al., 2021). It is also noted that the proxy reported \r\nAMOC decline, beginning in the late 19th century, is not supported by \r\nmodel-based evidence (Sections 3.5.4.1 and 9.2.3.1)."


id: 265146b3b2f9e6dae92b9ad0070f3490
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 3910
content:
"Both AR5 and SROCC reported that western boundary currents \r\n(WBCs) have undergone an intensification, warming and poleward \r\nexpansion, except for the Gulf Stream and the Kuroshio, but did \r\nnot provide confidence statements. The AR5 reported with medium\r\nto high confidence intensification of the North Pacific subpolar \r\ngyre, the South Pacific subtropical gyre, and the subtropical cells, \r\nalong with an expansion of the North Pacific subtropical gyre \r\nsince the 1990s. It  was pointed out that these changes are likely\r\npredominantly due to interannual-to-decadal variability, and in the \r\ncase of the subtropical cells represent a reversal of earlier multi\u0002decadal changes. SROCC concluded that it was unlikely that there \r\nhas been a statistically significant net southward movement of the \r\nmean Antarctic Circumpolar Current (ACC) position over the past \r\n20 years, in contrast to AR5, where this change had been assessed \r\nwith medium confidence. "


id: 1267d247ff1dd4fa3a3f47e7790ebddc
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 440
content:
"Repeated full depth in situ measurements report that deep \r\nconvection - a major driver for AMOC - has recently returned to the \r\nLabrador Sea, particularly in 2015 (Yashayaev and Loder, 2016; Rhein \r\net al., 2017), and to the Irminger Sea (de Jong and de Steur, 2016; \r\nGladyshev et al., 2016; de Jong et al., 2018) following an extended \r\nperiod with weak convection since 2000. An associated strengthening \r\nof the outflow from the Labrador Sea has not been observed (Zantopp \r\net al., 2017; Lozier et al., 2019), while strengthening of the AMOC is \r\ntentative (Desbruyeres et al., 2019; Moat et al., 2020). A long-term \r\nincrease of the upper overturning cell in the Southern Ocean since \r\nthe 1990s can be assessed with low confidence, and there is medium \r\nconfidence of a decrease in Antarctic bottom water (AABW) volume \r\nand circulation, which has potential implications for the strength of \r\nthe AMOC (Section 9.2.3.2)."


id: 5348d563e0f6dd6befe5b566f9a2f16
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11924
content:
"A latitudinal shift of subtropical/subpolar gyres on the order of \r\n0.1 +- 0.04deg per decade is derived by an indirect method using remote \r\nsensing data during 1993-2018 (Yang et al., 2020). Direct observations \r\nshow a systematic poleward migration of WBCs (Wu  et  al., 2012; \r\nYang et al., 2016, 2020; Bisagni et al., 2017). However, they do not \r\nsupport an intensification of WBCs, with a weakening, broadening, \r\nor little change reported for the Kuroshio (Y.-L. Wang et  al., 2016; "


id: d7631259a8aa388e0c79f1aeb7923a7d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 35195
content:
"In summary, proxy-based reconstructions suggest that the AMOC \r\nwas relatively stable during the past 8 kyr (medium confidence), \r\nwith a weakening beginning since the late 19th century (medium \r\nconfidence), but due to a lack of direct observations, confidence in \r\nan overall decline of AMOC during the 20th century is low. From the \r\nmid-2000s to mid-2010s, the directly observed weakening in AMOC "


id: 346d5e2fcb1a52db6e397ca0a4bacd9
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6460
content:
"Wang and Wu, 2018; Collins et  al., 2019), Gulf Stream (McCarthy \r\net  al., 2018; Collins et  al., 2019; Dong et  al., 2019; Andres et  al., \r\n2020), Agulhas (Beal and Elipot, 2016; Elipot and Beal, 2018) and \r\nEast Australian (Sloyan and O'Kane, 2015) currents. The Gulf Stream \r\nhas recently reversed a long-term poleward migration (Bisagni \r\net al., 2017). Multidecadal variability of the strength and position of \r\nWBCs (Hsin, 2015; Bisagni et al., 2017; McCarthy et al., 2018) and \r\nshort records from direct observations obscure the detection of any \r\nlong-term trends (Yang et al., 2020)."


id: 599772a37306d8b17d29d11a4c132c9d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13000
content:
"The AR5 assessed with high confidence that the pH of the ocean \r\nsurface had decreased since preindustrial times, primarily as a \r\nresult of ocean uptake of CO2. SROCC concluded that the global \r\nocean absorbed 20-30% of total CO2 emissions since the 1980s, \r\nwith virtually certain ocean surface pH decline. The SROCC assessed \r\na rate of surface pH decline of 0.017-0.027 pH units per decade \r\nacross a range of time series of pH observations longer than 15 \r\nyears. The decline in surface open ocean pH was assessed by SROCC \r\nas having very likely already emerged from background natural \r\nvariability for more than 95% of the global surface open ocean."


id: 491f1fba077f54146b27f1140d7868a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 10090
content:
"The Pacific to Arctic exchange at the Bering Strait plays a minor role in \r\nthe total Arctic exchange with the global ocean, which has increased \r\nfrom 0.8 Sv to 1.0 Sv over 1990-2015 (Woodgate, 2018). For Atlantic\u0002Arctic exchange, major branches of Atlantic Water inflow from the \r\nNorth Atlantic into the Arctic across the Greenland-Scotland Ridge \r\nhave remained stable since the mid-1990s (Berx et al., 2013; Hansen \r\net  al., 2015; Jochumsen et  al., 2017; Osterhus et  al., 2019), with \r\nonly the smaller pathway of Atlantic Water north of Iceland showing \r\na strengthening trend during 1993-2018 (Casanova-Masjoan et al., \r\n2020), but with associated heat transport strengthening through \r\nthe 1990s (Rossby et al., 2020; Tsubouchi et al., 2021). The Arctic \r\noutflow remained broadly stable from the mid-1990s to the mid \r\n2010s (Osterhus et al., 2019). "


id: ba89ca91efe32355d65b4f764b094701
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30032
content:
"The heat and mass transport of the Indonesian throughflow  (ITF) \r\nshows substantial variability at seasonal to decadal time scales \r\n(Zhuang et al., 2013; Q.-Y. Liu et al., 2015; Susanto and Song, 2015; \r\nFeng et al., 2017, 2018; M. Li et al., 2018; Sprintall et al., 2019; Xie \r\net al., 2019). Q.-Y. Liu et al. (2015) reported an increasing trend in \r\nthe ITF geostrophic transport of 1 Sv per decade over 1984-2013, \r\nconsistent with direct estimates (Sprintall et al., 2014), and results \r\nfrom reanalyses (M. Li et al., 2018), and this appears to be linked to \r\nmulti-decadal scale variability rather than a long-term trend (Kosaka \r\nand Xie, 2013; England et al., 2014; Lee et al., 2015). "


id: 4fcda453f15af8ba7124464e45643407
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11336
content:
"Southern Ocean circulation changes are assessed in SROCC (Meredith \r\net al., 2019), and are confirmed and synthesized in Section 9.2.3.2 \r\nwhich shows that there is no indication of ACC transport change, \r\nand that it is unlikely that the mean meridional position of the ACC \r\nhas moved southward in recent decades."


id: a1dbd29d997c431edb4e495decac2284
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 25698
content:
"In summary, over the past 3-4 decades, the WBC strength is highly \r\nvariable (high confidence), and WBCs and subtropical gyres have \r\nshifted poleward since 1993 (medium confidence). Net Arctic Ocean \r\nvolume exchanges with the other ocean basins remained stable over \r\nthe mid-1990s to the mid-2010s (high confidence). There is high \r\nconfidence that the ITF shows strong multi-decadal scale variability \r\nsince the 1980s."


id: 4a74c8a12c5117b7cb8796a5cd861175
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 10339
content:
"For subsurface pH changes, estimates arise from direct ship \r\nmeasurements from repeated hydrography programs (Carter et  al., \r\n2019), indirect estimates of pH through calcite and aragonite saturation \r\nhorizons (Osborne et al., 2020; Ross et al., 2020), and the very recent \r\nbiogeochemical Argo floats equipped with pH sensors (Claustre \r\net  al.,  2020). Global subsurface pH has decreased over the past 20 \r\nto 30 years, with signals observed to at least 1000 m depths (Lauvset \r\net al., 2020). Global findings are supplemented by regional findings \r\nfrom the Pacific Ocean (Carter et al., 2019; Ross et al., 2020); the South \r\nAtlantic (Salt et  al., 2015) and Southern Ocean (Jones et  al., 2017); \r\nthe North Atlantic Ocean and along the AMOC (Woosley et al., 2016; \r\nPerez et al., 2018), the Arctic Ocean (Qi et al., 2017) and marginal seas \r\n(C.-T.A. Chen et al., 2017). Further details are given in Section 5.3.3.1."


id: cdb3cea3fb7481c5e15a84098f24b30f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 33519
content:
"To conclude, it is virtually certain that surface open ocean pH has \r\ndeclined globally over the last 40 years by 0.003-0.026 pH per \r\ndecade, and a decline in the ocean interior has been observed in \r\nall ocean basins over the past 2-3 decades (high confidence). \r\nA  long-term increase in surface open ocean pH occurred over the \r\npast 50 Myr (high confidence), and surface open ocean pH as low \r\nas recent times is uncommon in the last 2 Myr (medium confidence). \r\nThere is very high confidence that open ocean surface pH is now the \r\nlowest it has been for at least 26 kyr and current rates of pH change \r\nare unprecedented since at least that time. "


id: eb78795c8665116ae5f191aaa231d72
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 38785
content:
"SROCC concluded that there has very likely been a net loss of \r\noxygen over all ocean depths since the 1960s linked to global ocean \r\ndeoxygenation at a range of 0.3-2.0%, and that the oxygen levels in the \r\nglobal upper 1000 m of the ocean had decreased by 0.5-3.3% during \r\n1970-2010 (medium confidence), alongside an expansion of oxygen \r\nminimum zones (OMZ) by 3-8%. For the surface ocean (0-100 m) \r\nand the thermocline at 100-600 m, the very likely range of oxygen \r\ndecline was assessed to be 0.2-2.1% and 0.7-3.5%, respectively. \r\nMultidecadal rates of deoxygenation showed variability throughout \r\nthe water column and across ocean basins (high confidence)."


id: 53912fd00f0b4d873d8008d0f8dd4e07
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11976
content:
"Findings since SROCC provide further support that the volume of \r\nseverely oxygen-depleted water has expanded in some locations \r\nof the global ocean (Section 5.3.3.2). For example, vertical expansion \r\nof low oxygen zones is reported in the North Pacific at a rate of \r\n3.1 +- 0.5 m yr-1 (Ross et al., 2020), and suboxic waters have increased \r\nby 20% at a rate of about 19 m per decade from 1982-2010 in the \r\nArabian Sea (Al-Said et al., 2018; Lachkar et al., 2019), and expanded \r\noff the coast of Mexico (Sanchez-Velasco et al., 2019)."


id: 347d8eb70efd7be35f99edfb33f5112f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6471
content:
"In summary, episodes of widespread and long-lasting (100 ka scales) \r\nopen-ocean deoxygenation were related to warm climate intervals of \r\nthe Permian-Cretaceous, with conditions becoming generally better \r\noxygenated as the climate cooled over the course of the Cenozoic (high \r\nconfidence). The largest expansions of oxygen depleted waters over \r\nthe past 25 ka were strongly linked to rapid warming rates (medium \r\nconfidence). Open-ocean deoxygenation has occurred in most regions \r\nof the open ocean during the mid-20th to early 21st centuries (high \r\nconfidence), and shows decadal variability (medium confidence). \r\nEvidence further confirms SROCC that OMZs are expanding at many \r\nlocations (high confidence)."


id: f9d13cd3e8f9085fe33a1058863334c0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41311
content:
"This section is limited to a few biological indicators to demonstrate the \r\nclose links between the biosphere and physical forcing. In selecting \r\nthe indicators, we focussed on (i) those that are observable at large \r\n(global) spatial scales and over long (two decades or more) temporal \r\nscales, using standardized and consistent procedures; and (ii) those \r\nthat are illustrative of the influence of the physical system on the \r\nbiological realm. Chapters 2 and 3 of AR6 WGII undertake a more \r\nholistic assessment of biospheric impacts."


id: 6ba2f081a5d08c78438c41bdb6783041
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16242
content:
"New findings for ocean oxygen content since SROCC are limited \r\nto regional scale assessments. The magnitude of change is difficult \r\nto compare across regions to arrive at a global assessment due to \r\ndifferences in depth range, time period, baseline climatology, \r\nmethodology, and particularly the use of different units. To facilitate \r\ncomparisons, data are presented as change per decade, and \r\nconversions of the SROCC global mean percentage of oxygen decline \r\nestimates are provided as a loss of 3.2 mmol kg-1 in the upper 1000 m \r\nof the global ocean (1.93%), 2.0 mmol kg-1 (0.8 mmol kg-1 per decade) \r\nin the upper 1000 m of the global ocean (1.93%), and 2.0  mmol \r\nkg-1 (0.5 mmol kg-1 per decade) in the entire water column (1.15%) \r\nbetween 1970 and 2010 (Bindoff et al., 2019). Oxygen change also \r\nshows decadal variability (Ito et al., 2016; Stramma et al., 2020) that \r\ncan influence estimates of trends. "


id: e9b6918f49da8cacf764b33352413646
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 38472
content:
"The AR5 noted that because CO2 uptake by photosynthesis occurs \r\nonly during the growing season, the greater land mass in the NH \r\nimparts a characteristic 'sawtooth' seasonal cycle in atmospheric \r\nCO2. The SRCCL similarly stated that due to strong seasonal patterns \r\nof growth, NH terrestrial ecosystems are largely responsible for \r\nthe seasonal variations in global atmospheric CO2 concentrations. \r\nNeither AR5 nor SRCCL made a confidence statement about observed \r\nchanges in the amplitude of the seasonal cycle of CO2. "


id: bbcf154a99b35b98db344a1b97feece8
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30270
content:
"In situ observations of CO2 generally depict a rising amplitude of the \r\nseasonal cycle over the past half century, especially north of about \r\n45degN (Figure 2.30). For example, an amplitude increase of 6 +- 2.6% \r\nper decade has been observed at the Barrow surface observatory in \r\nAlaska over 1961-2011 (Graven et  al., 2013), with slightly slower \r\nincreases thereafter. Aircraft data north of 45degN exhibit an amplitude \r\nincrease of 57 +- 7% at 500 mb versus an increase of 26 +- 18% for \r\n35degN-45degN between field campaigns in 1958-1961 and 2009-2011 \r\n(Graven et  al., 2013). Increases in amplitude for the period \r\n1980-2012 are apparent at eight surface observatories north of 50degN \r\n(Piao et al., 2018), related primarily to a larger drawdown in June \r\nand July. Trends in seasonal cycle amplitude at lower latitudes are \r\nsmaller (if present at all); for instance, the increase at the Mauna Loa "


id: 8f386484ce59c3e79a3b0253f01b0833
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 22399
content:
"observatory in Hawaii since the early 1960s is only about half as \r\nlarge as at Barrow (Graven et al., 2013), and only one other low\u0002latitude observatory has a significant increase from 1980-2012 (Piao \r\net al., 2018). There is a weak signal of an increase in amplitude at the \r\nSinhagad observatory in western India in recent years (Chakraborty \r\net al., 2020). Generally speaking, larger increases in the Arctic and \r\nboreal regions are indicative of changes in vegetation and carbon \r\ncycle dynamics in northern ecosystems (Forkel et al., 2016), though \r\nincreased carbon uptake can also result from other factors such as \r\nwarmer- and wetter-than-normal conditions. "


id: 2a422ef16e2ade35f95b57436b5b6a49
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 4651
content:
"Recent satellite-based, global-scale estimates of seasonal variations \r\nin atmospheric CO2 for the period 2003-2018 show that the seasonal \r\nvariations in the SH are out of phase with those in the NH (Reuter \r\net  al., 2020), which is consistent with the phenological shifts in \r\nprimary productivity between hemispheres. The net effect of the \r\nphase shift between the two hemispheres is to dampen the amplitude \r\nof the global average seasonal cycle. These integrated results also \r\nshow that the amplitude of the oscillations has been increasing in \r\nthe SH, from about 2009, but comparison with data from Baring head \r\nsuggests that periods of high seasonal oscillation had occurred at \r\nthat location in the SH prior to 1995."


id: 1127fa9fe8dd69a2447c94b5ada1427a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 212
content:
"In summary, there is very high confidence that the amplitude of the \r\nseasonal cycle of atmospheric CO2 has increased at mid-to-high NH \r\nlatitudes since the early 1960s. The observed increase is generally \r\nconsistent with greater greening during the growing season and an \r\nincrease in the length of the growing season over the high northern \r\nlatitudes. Similarly, globally-integrated results from the SH also show \r\nan increase in seasonal amplitude of atmospheric CO2 signal, from \r\naround 2009 to 2018 (low confidence)."


id: 3785651644f7aea12192563cca659822
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6981
content:
"SROCC pointed out that long-term global observations of many \r\nkey ocean variables, including phytoplankton, have not reached the \r\ndensity and accuracy necessary for detecting change. But SROCC \r\nnoted the good comparability between short time-scale single-sensor \r\nocean-colour products and a longer time-scale, climate-quality \r\ntime series of multi-sensor, inter-sensor-bias-corrected, and error\u0002characterized, global data on chlorophyll-a concentration in the \r\nsurface layers of the ocean. With respect to oligotrophic gyres, \r\nAR5 WGII concluded that the oligotrophic subtropical gyres of the \r\nAtlantic and Pacific Oceans are expanding and that they indicate \r\ndeclining phytoplankton stocks in these waters (limited evidence, \r\nlow agreement). With respect to distributions of marine organisms, \r\nAR5 WGII reported range shifts of benthic, pelagic, and demersal \r\nspecies and communities (high confidence), though the shifts were \r\nnot uniform. "


id: 2cac401e9206588078a67408067744a4
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 5122
content:
"Phytoplankton are responsible for marine primary production \r\nthrough photosynthesis; they are a major player in the ocean carbon \r\ncycle. They have a high metabolic rate and respond fast to changes in \r\nenvironmental conditions (light, temperature, nutrients, mixing), and \r\nas such, serve as a key indicator for change in marine ecosystems. "


id: d688e7f8494164b7132fd65a9088bff6
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 35054
content:
"data in many regions is strongly tied to indices of climate variability \r\n(Section 2.4 and Annex IV) and changes in total concentration are \r\ntypically associated with changes in phytoplankton community \r\nstructure (e.g., Brewin et al., 2012; Racault et al., 2017b). Variability \r\nin community structure related to El Nino has, in turn, been linked to \r\nvariability in fisheries, for example in the catch of anchovy (Engraulis \r\nringens) in the Humboldt current ecosystem (Jackson et al., 2011)."


id: 3748c3a09cb468181aaf3184d54d0cfb
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6942
content:
"Concentration of chlorophyll-a, the major photosynthetic pigment \r\nin all phytoplankton, is often used as a measure of phytoplankton \r\nbiomass. As primary producers, they are also food for organisms at \r\nhigher trophic levels. The multi-sensor time series of chlorophyll-a \r\nconcentration has now been updated (Sathyendranath et  al., \r\n2019) to cover 1998-2018. Figure 2.31 shows that global trends in \r\nchlorophyll-a for the last two decades are insignificant over large \r\nareas of the global ocean (von Schuckmann et al., 2019), but some \r\nregions exhibit significant trends, with positive trends in parts of the \r\nArctic and the Antarctic waters (>3% yr-1), and both negative and \r\npositive trends (within +- 3% yr-1) in parts of the tropics, subtropics \r\nand temperate waters. The interannual variability in chlorophyll-a "


id: 86f5aeed5ff4a4c469e751f8ae69c72a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20908
content:
"In summary, there is high confidence that the latitudinal and depth \r\nlimits of the distribution of various organisms in the marine biome \r\nare changing. There is medium confidence that there are differences \r\nin the responses of individual species relative to each other, such that \r\nthe species compositions of ecosystems are changing. There is medium \r\nconfidence that chlorophyll concentration in the surface shows weak \r\nnegative and positive trends in parts of low and mid latitudes, and \r\nweak positive trends in some high-latitude areas. There is medium \r\nconfidence that the large-scale distribution of the oligotrophic \r\ngyre provinces is subject to significant inter-annual variations, but "


id: d42f4a56cadbed742595a3e5dc1cd4a5
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 34661
content:
"low confidence in the long-term trends in the areal extent of these \r\nprovinces because of insufficient length of direct observations."


id: fc19abc86178bc2559d28c483517eb38
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41715
content:
"when subjected to the same environmental changes (Edwards \r\nand Richardson, 2004). Furthermore, different factors could be \r\nresponsible for triggering phenological responses in different stages \r\nin the life cycle of a single organism (Koeller et al., 2009). The shift \r\nin the distribution of many benthic invertebrates on the North-west \r\nAtlantic shelf, including some commercially important shellfish, \r\ncould be explained by phenology and larval transport, and the \r\nshift and contraction of species range have been associated with \r\nhigher mortality (Fuchs et  al., 2020). Changes in phytoplankton \r\nphenological indicators globally (Racault et al., 2012; Sapiano et al., \r\n2012) have been linked to indicators of climate variability, such as \r\nthe multivariate ENSO Index (Racault et al., 2017a), with responses \r\nvarying across ecological provinces of the ocean (Longhurst, 2007). "


id: cfd03341d6dc6476c4448105a2d4a991
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 33919
content:
"SROCC expressed low confidence in satellite-based estimates of \r\ntrends in marine primary production, citing insufficient length of the \r\ntime series and lack of corroborating in situ measurements and \r\nindependent validation time series. The report also cites significant \r\nmismatches in absolute values and decadal trends in primary \r\nproduction when different satellite-based products are compared."


id: e7139c44a29f85f2808667c983e8ee9e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 37950
content:
"In conclusion, there is low confidence because of the small number of \r\nrecent studies and the insufficient length of the time series analysed \r\nthat marine primary production is 47 (+- 7.8) PgC yr-1. A small decrease \r\nin productivity is evident globally for the period 1998-2015, but \r\nregional changes are larger and of opposing signs (low confidence). "


id: 98eb17da1ff0f6b99bfd2a16e0925e19
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 24117
content:
"In summary, new in situ data as well as satellite observations \r\nstrengthen AR5 and SROCC findings that various phenological metrics \r\nfor many species of marine organisms have changed in the last half \r\ncentury (high confidence), though many regions and many species \r\nof marine organisms remain under-sampled or even unsampled. The \r\nchanges vary with location and with species (high confidence). There \r\nis a strong dependence of survival in higher trophic-level organisms \r\n(fish, exploited invertebrates, birds) on the availability of food at \r\nvarious stages in their life cycle, which in turn depends on phenologies \r\nof both (high confidence). There is a gap in our understanding of how \r\nthe varied responses of marine organisms to climate change, from \r\na phenological perspective, might threaten the stability and integrity \r\nof entire ecosystems. "


id: 37bb1f8ee37c670cf2ee68d18879aec1
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 7014
content:
"Phenology is the study of the timing of important events in the \r\nannual life cycle of organisms (plants or animals; see also Annex VII: \r\nGlossary). The AR5 WGII noted that the timing of various seasonal \r\nbiological events in the ocean had advanced by more than four days \r\nper decade over the previous 50-year period and concluded that there \r\nwas high confidence in observed changes in the phenological metrics \r\nof marine organisms. The AR5 WGII further reported that, of those \r\nobservations that showed a response, 81% of changes in phenology, \r\ndistribution and abundance were consistent with anticipated \r\nresponses to climate warming according to theoretical expectations, \r\ncorroborated by updates in SROCC. The consequent current and future \r\nimpacts on interactions between species, including competition and \r\npredator-prey dynamics, were noted with high confidence."


id: 29794882e6fe03c16cc23b393fb9eaab
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 4513
content:
"There are additional indications that phenological metrics related to \r\ndifferent species are changing, but not always in a similar manner. \r\nFor example, many seabirds are breeding earlier, while others are \r\nbreeding later (Sydeman et  al., 2015). Planktonic organisms in \r\nthe North Atlantic are also responding differently to each other "


id: 12479a640297609c1ef08a4dc63fa8d7
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 413
content:
"The AR5 WGII briefly discussed large-scale changes in the length of the \r\ngrowing season but made no confidence statement about observed \r\ntrends. However, AR5 did conclude with high confidence that warming \r\ncontributed to an overall spring advancement in the NH."


id: 47ef8d9c89278421813f14ea8522fd4f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 9871
content:
"increased by at least 1.0 days per decade since 1960 (Xia et  al., \r\n2018) and by several days per decade in South Korea since 1970 \r\n(Jung et al., 2015). In general, changes in phenological indicators are \r\nconsistent with the increase in growing season length documented by \r\ninstrumental data (Parmesan and Hanley, 2015). Several long-term, \r\nsite-specific records illustrate the unusualness of recent phenological \r\nchanges relative to interannual variability; for example, peak bloom \r\ndates for cherry blossoms in Kyoto, Japan have occurred progressively \r\nearlier in the growing season in recent decades, as have grape harvest \r\ndates in Beaune, France (Figure 2.32)."


id: 74fd8e13db0a919c37c36a48cf40e843
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17817
content:
"Recent in situ analyses document increases in the length of the thermal \r\ngrowing season (i.e., the period of the year when temperatures are \r\nwarm enough to support growth) over much of the extratropical land \r\nsurface since at least the mid-20th century. Over the NH as a whole, \r\nan increase of about 2.0 days per decade is evident for 1951-2018 \r\n(Dunn et  al., 2020), with slightly larger increases north of 45degN \r\n(Barichivich et al., 2013). Over North America, a rise of about 1.3 days \r\nper decade is apparent in the United States for 1900-2014 (Kukal \r\nand Irmak, 2018), with larger increases after 1980 (McCabe et  al., \r\n2015); likewise, all ecozones in Canada experienced increases from \r\n1950-2010 (Pedlar et  al., 2015). Growing season length in China "


id: fc50ac4955787e4d0a9cca4416679284
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41758
content:
"The general consistency between in situ and satellite estimates \r\nover the NH is noteworthy given that many factors independently \r\ncontribute to uncertainty in observed changes. For example, there \r\nis no universally accepted definition of growing season length \r\nacross in situ analyses; some define the growing season as the \r\nperiod based on a temperature threshold (e.g.,  5degC) whereas \r\nothers use the frost-free period. Spatial and temporal coverage \r\ncan also affect conclusions based upon in situ studies (Donat et al., \r\n2013b). For satellite analyses, uncertainties can be related to the \r\nsatellite datasets themselves (e.g., satellite drift, sensor differences, \r\ncalibration uncertainties, atmospheric effects); and to the methods \r\nfor determining phenological metrics (e.g., start, end, and length of \r\nseason; S. Wang et al., 2016). "


id: acd3b1d240c10448cbf6b7cb57b16998
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 27651
content:
"In summary, based on multiple independent analyses of in situ, \r\nsatellite, and phenological data, there is high confidence that \r\nthe length of the growing season has increased over much of the \r\nextratropical NH since at least the mid-20th century."


id: bda8418e217ba107429e006584f3bfe0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30626
content:
"The AR5 WGII concluded that many terrestrial species have shifted \r\ntheir geographic ranges in recent decades (high confidence). Similarly, \r\nSRCCL assessed that many land species have experienced range size \r\nand location changes as well as altered abundances over recent \r\ndecades (high confidence). SROCC noted that species composition \r\nand abundance have markedly changed in high mountain ecosystems \r\nin recent decades (very high confidence)."


id: 5ca9ecf79dd274d2bab380e896663210
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13566
content:
"Paleoclimate reconstructions document large-scale biome shifts from \r\nthe deep past through the Holocene (e.g., Hoogakker et al., 2016). \r\nThe northernmost location of the treeline is a representative indicator \r\nin this regard (Figure 2.34). During the MPWP, boreal forest extended \r\nto the Arctic coast, with the northernmost treeline being about 4deg \r\nto 10deg latitude further north than at present; temperate forests and \r\ngrasslands were also shifted poleward (with reduced tundra extent), \r\nwhile savannahs and woodlands were more expansive in Africa \r\nand Australia at the expense of deserts (Cross-Chapter Box  2.4, \r\nFigure  1b; Salzmann et  al., 2008, 2013; Sniderman et  al., 2016; \r\nAndrae et al., 2018). During the LGM, tundra and steppe expanded \r\nwhereas forests were globally reduced in extent (Prentice et al., 2000; "


id: 17a634c438f69aada9466345c15763ff
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 1368
content:
"There are exceptions to the general pattern of poleward/upslope \r\nmigration. For some species, various biotic and abiotic factors (such \r\nas precipitation and land use) supersede the physiological effects of \r\ntemperature (Vanderwal et  al., 2013; Gibson-Reinemer and Rahel, \r\n2015; Ordonez et al., 2016; Scheffers et al., 2016; Lenoir et al., 2020). \r\nFor other species, poleward migration is slower than expectations \r\nfrom the observed temperature increases. Trees are one such example \r\nbecause of their long lifespan and gradual maturity (Renwick and \r\nRocca, 2015); in fact, poleward advance is only evident at about \r\nhalf of the sites in a large global dataset of treeline dynamics for "


id: 23ea35cb659c406bd2da21bcc5df3d22
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 3505
content:
"1900-present (Harsch et  al., 2009). Furthermore, the northernmost \r\nextent of treeline at present (roughly 73degN) is actually somewhat \r\nsouth of its location in the MH (MacDonald et al., 2008) despite an \r\nexpanding growing season in the extratropical NH since the mid-20th \r\ncentury (Section 2.3.4.3.1)."


id: 608819119645068d807abc19f14132d0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 14287
content:
"In summary, there is very high confidence that many terrestrial species \r\nhave shifted their geographic ranges poleward and/or upslope over \r\nthe past century, with increased rates of species turnover. There is \r\nhigh confidence that the geographical distribution of climate zones \r\nhas shifted in many parts of the world. "


id: 1f2543c2d2ba25f1eecfeb0af1b67a37
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 2687
content:
"The AR5 WGII briefly discussed changes in global vegetation \r\ngreenness derived from satellite proxies for photosynthetic activity. \r\nObserved trends varied in their strength and consistency, and AR5 \r\nthus made no confidence statement on observed changes. The SRCCL \r\nsubsequently concluded that greening had increased globally over \r\nthe past 2-3 decades (high confidence)."


id: de4fcde14f8946973738d9811e4d27c8
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 36372
content:
"Figure 2.33 | Satellite-based trends in fraction of absorbed photosynthetically \r\nactive radiation (per decade) for 1998-2019. Trends are calculated using OLS \r\nregression with significance assessed following AR(1) adjustment after Santer et al. \r\n(2008); 'x' marks denote non-significant trend). Unvegetated areas such as barren \r\ndeserts (grey) and ice sheets (white) have no trend in FAPAR. Further details on data \r\nsources and processing are available in the chapter data table (Table 2.SM.1)."


id: 4ee9d8188727bd33b552b45e281da3f0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11165
content:
"phenological metrics from satellite data as well as a variety of statistical \r\ntechniques for analysing historical changes (S. Wang et al., 2016)."


id: c7d586429406600f7b676ad351e3d0b6
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 32463
content:
"coming up to the present day. This synthesis serves as an assessment \r\nof the evidence for change across the climate system as represented \r\nby the instrumental record and its unusualness in the longer-term \r\ncontext. Building upon previous sections assessing the observational \r\nevidence for each key indicator individually, this section integrates \r\nthe evidence across multiple indicators to arrive at a holistic and \r\nrobust final assessment."


id: d22ce86591b0275f3e3198ee3c3a0d75
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 34331
content:
"In summary, there is high confidence that vegetation greenness \r\n(i.e., green leaf area and/or mass) has increased globally since the \r\nearly 1980s. However, there is low confidence in the magnitude of \r\nthis increase owing to the large range in available estimates."


id: 86ae0ccfc6f9818c7cfa9e2994e11397
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20863
content:
"Climate has varied across a broad range of timescales (Figure 2.34). \r\nDuring the Cenozoic Era temperatures generally decreased over tens \r\nof millions of years, leading to the development of ice sheets. During \r\nthe last two million years, climate has fluctuated between glacials \r\nand interglacials. Within the current Holocene interglacial and, with \r\nincreasing detail in the CE, it is possible to reconstruct a history both "


id: 6167bdfe9053e6888f1974a67334ed7d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 14437
content:
"Section 2.3 has assessed the observational evidence for changes in key \r\nindicators across the atmosphere, cryosphere, ocean and biosphere \r\nstarting, where applicable, from paleoclimate proxy  records and "


id: bcd0ff028dd5040aa9217d754ee3f78f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30460
content:
"Figure 2.34 | Selected large-scale climate indicators during paleoclimate and recent reference periods of the Cenozoic Era. Values are based upon \r\nassessments carried out in this chapter, with confidence levels ranging from low to very high. Refer to Cross-Chapter Box 2.1 for description of paleoclimate reference periods \r\nand Section 1.4.1 for recent reference periods. Values are reported as either the very likely range (x to y), or best estimates from beginning to end of the reference period with \r\nno stated uncertainty (x - y), or lowest and highest values with no stated uncertainty (x ~ y). Temperature is global mean surface temperature. Glacier extent is relative and \r\ncolour scale is inverted so that more extensive glacier extent is intuitively blue."


id: bfdc9f30683d0da05522060e021a7c0f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
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index: climate_gpt_v2
vector_id: 31043
content:
"it has been on a centennially-averaged basis in the CE and more likely \r\nthan not since the peak of the LIG. Many more integrative components \r\nof the climate system (e.g., glaciers, GMSL) are experiencing conditions \r\nunseen in millennia, whereas the most slowly responding components \r\n(e.g.,  ice-sheet extent, permafrost, tree line) are at levels unseen in \r\ncenturies (high confidence). The rate at which several assessed climate \r\nindicators (e.g., GMSL, OHC, GSAT) have changed over recent decades \r\nis highly unusual in the context of preceding slower changes during the \r\ncurrent post-glacial period (high confidence)."


id: 194d160cf487e8f24b737922d664a7c8
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 1662
content:
"of more indicators of the climate system and, with increasing fidelity, \r\nthe rates of change. Solely for the last 150 years or so are instrumental \r\nobservations of globally distributed climate indicators available. \r\nHowever, only since the late 20th century have observational \r\nsystems attained essentially global monitoring capabilities. The \r\ndirect observations point unequivocally to rapid change across many \r\nindicators of the climate system since the mid-19th century. These are \r\nall consistent in indicating a world that has warmed rapidly. "


id: 2cd6726a012ca62a67ca3818ee0bf198
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 5156
content:
"Assessing the long-term context of recent changes is key to \r\nunderstanding their potential importance and implications. The climate \r\nsystem consists of many observable aspects that vary over a very \r\nbroad range of timescales. Some biogeochemical indicators of change \r\nsuch as atmospheric CO2 concentrations and ocean pH have shifted \r\nrapidly and CO2 concentrationsare currently at levels unseen in at least \r\n800 kyr (the period of continuous polar ice-core records) and very likely\r\nfor millions of years. The GMST in the past decade is likely warmer than "


id: 5f6ce93c8d95570d65ce322de5cd9562
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 14097
content:
"In summary, directly observed changes in the atmosphere, ocean, \r\ncryosphere and biosphere represent unequivocal evidence of \r\na warming world. Key climate indicators are now at levels not \r\nexperienced for centuries to millennia. Since the late 19th century \r\nmany indicators of the global climate system have changed at a rate \r\nunprecedented over at least the last two thousand years."


id: 31d315d97a88238b51ab69f6467718b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 6015
content:
"Cross-Chapter Box 2.4 | The Climate of the Pliocene (Around 3 Million Years Ago), When CO2\r\nConcentrations Were Last Similar to Those of the Present Day"


id: 3e315a7c8ff395592eada8193c8788d1
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 8118
content:
"Contributing Authors: Alan M. Haywood (United Kingdom), Darrell S. Kaufman (United States of America), Nicholas R. Golledge \r\n(New Zealand/United Kingdom), Dabang Jiang (China), Daniel J. Lunt (United Kingdom), Erin L. McClymont (United Kingdom), \r\nUlrich Salzmann (United Kingdom/Germany, United Kingdom), Jessica Tierney (United States of America)"


id: 707e604806a928e5a167eed6f6101089
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17048
content:
"Throughout this Report, information about past climate states is presented in the context of specific climate variables, processes or \r\nregions. This Cross-Chapter Box focuses on a single paleoclimate reference period as an example of how proxy data, models and \r\nprocess understanding come together to form a more complete representation of a warm climate state that occurred during the \r\nrelatively recent geologic past."


id: 5af59a67cac802bab121d7c5f1bac42d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13253
content:
"During the MPWP (3.3-3.0 Ma) the atmospheric CO2 concentration was similar to present, and the slow-response, large-scale \r\nindicators reflect a world that was warmer than present. With very high confidence, relative to present, global surface temperature, \r\nsea level, and precipitation rate were higher, NH latitudinal temperature gradient was lower, and major terrestrial biomes expanded \r\npoleward. With medium confidence from proxy-based evidence alone (Section 2.3.2), combined with numerical modelling, analysis \r\nof the sea-level budget, and process understanding (Section 9.6.2), there is high confidence that cryospheric indicators were \r\ndiminished. There is medium confidence that the Pacific longitudinal temperature gradient was weaker and monsoon systems \r\nwere stronger."


id: 7c131d24ab7bd91e2e9deab0ed9f1374
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 19038
content:
"Modes of climate variability that are important for large-scale climate \r\non interannual and longer timescales (Cross-Chapter Box 2.2) are \r\nassessed herein and defined and summarized in Annex IV. Though \r\nthe modes of variability discussed here are assessed and classified on \r\nthe basis of physical variables, it is important to recognize that the \r\ndistribution and function of various components of the terrestrial and \r\nmarine biospheres are modified in response to them. "


id: 66d141ce8ed924b5c51c23a15b898ecb
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 15356
content:
"The AR5 reported that the shift towards a positive NAO, a mode \r\nof variability in the North Atlantic that is closely related to the \r\nhemispheric-scale NAM, from the 1950s to the 1990s was largely \r\nreversed by more recent changes (high confidence). Moreover, \r\nperiods of persistent negative or positive NAO states observed during \r\nthe latter part of the 20th century were not unusual, based on NAO \r\nreconstructions spanning the last half millennium (high confidence)."


id: 52a67bd380ab815b142d2cd259066f73
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11823
content:
"In summary, positive trends for the NAM/NAO winter indices \r\nwere observed between the 1960s and the early 1990s, but these \r\nindices have become less positive or even negative thereafter (high \r\nconfidence). The NAO variability in the instrumental record was very \r\nlikely not unusual in the millennial and multi-centennial context."


id: 8e7577af411e3226c5de20c74cdb5164
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 22252
content:
"The AR5 concluded that it was likely that the SAM had become more \r\npositive since the 1950s and that this increase was unusual in the \r\ncontext of the prior 400 years (medium confidence). Both AR5 and \r\nSROCC reported statistically significant trends in the SAM during the \r\ninstrumental period for the austral summer and autumn. "


id: d7d859940e7b664a26e568195855fdc0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 35281
content:
"Prolonged periods of negative SAM values were identified during the \r\nperiod 1400-1700 CE in several reconstructions (Figure 2.35, Villalba \r\net al., 2012; Abram et al., 2014; Datwyler et al., 2018), with a minimum \r\nidentified during the 15th century (Hernandez et al., 2020), although "


id: 606b57b86c1766da84b7210d5e6ddb6
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 14270
content:
"least the past millennium, although medium confidence arises due to \r\nthe differences between proxy records before 1800 CE."


id: c303a93a3ffce8da427017170374469f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 31584
content:
"some disagreements exist between proxy records before 1800 CE \r\n(Hessl et  al., 2017). Abram et  al. (2014) concluded that the mean \r\nSAM index during recent decades is at its highest levels for at least \r\nthe last 1 kyr. Similarly, the summer SAM reconstruction by Datwyler \r\net al. (2018) indicates a strengthening over the last 60 years that is \r\noutside the very likely range of the last millennium natural variability. \r\nThe largest 30- and 50-year trends in the annual SAM index occurred \r\nat the end of the 20th century (after 1969 and 1950 respectively), \r\nindicating that the recent increase in the SAM is unprecedented in \r\nthe context of at least the past three centuries (Yang and Xiao, 2018). "


id: 15cffe0360123e4b280bb5a3fe09e855
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 1056
content:
"The AR5 reported with medium confidence that ENSO-like variability \r\nexisted, at least sporadically, during the warm background state of the \r\nPliocene. It was also found (high confidence) that ENSO has remained \r\nhighly variable during the last 7 kyr with no discernible orbital \r\nmodulation. The AR5 concluded that large variability on interannual \r\nto decadal timescales, and differences between datasets, precluded \r\nrobust conclusions on any changes in ENSO during the instrumental \r\nperiod. The SROCC reported epochs of strong ENSO variability \r\nthroughout the Holocene, with no indications of a systematic trend in \r\nENSO amplitude, but with some indication that the ENSO amplitude \r\nover 1979-2009 was greater than at any point in the period from \r\n1590-1880 CE. It was also reported that the frequency and intensity \r\nof El Nino events in the period from 1951-2000 was high relative to \r\n1901-1950. "


id: ac6f9f4869c28b27b05965b2eeddec
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 27577
content:
"In summary, historical station-based reconstructions of the SAM \r\nshow that there has been a robust positive trend in the SAM index, \r\nparticularly since 1950 and for the austral summer (high confidence). \r\nThe recent positive trend in the SAM is likely unprecedented in at "


id: f6adde9c1f4c4edc9c2d671028e6946
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 40771
content:
"Numerous studies (J. Li et al., 2013; S. McGregor et al., 2013; Rustic et al., \r\n2015; Hope et al., 2017; Y. Liu et al., 2017) find substantial variability \r\nin ENSO activity on multi-decadal to centennial timescales over the \r\nlast 500 to 1 kyr (Figure 2.36). Different proxies show a wide spread \r\nin the specific timing and magnitude of events in the pre-instrumental \r\nperiod (e.g., Datwyler et al., 2019). Most investigators find that ENSO "


id: 5bf12c87b38630cf181568a8d72bbdf3
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 13437
content:
"activity in recent decades was higher than the most recent centuries \r\nprior to the instrumental period. Grothe et al. (2019) also found that \r\nENSO variance of the last 50 years was 25% higher than the average \r\nof the last millennium, and was substantially higher  than the \r\naverage of the mid- to late-Holocene. S. McGregor et al., (2010, 2013) \r\nlooked for common variance changes in pre-existing ENSO proxies, \r\nfinding stronger ENSO variance for the 30-year period 1979-2009 \r\ncompared to any 30-year period within the timespan 1590-1880 CE. \r\nThis finding also holds when adding more recently developed ENSO \r\nproxies (Figure 2.36). Koutavas and Joanides (2012), Ledru et  al. \r\n(2013) and Thompson et al. (2017) identify various periods within the \r\nrange 1000 BCE to 1300 CE when ENSO activity was greater than \r\nin the following centuries, and more closely comparable to the mid\u000220th century onwards behaviour."


id: 98681edd098d1a53c3116147be8e64b0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 24024
content:
"Since AR5, updates to datasets used widely in prior ENSO assessments \r\nresulted in substantial and important revisions to observed tropical \r\nPacific SST data (Section 2.3.1.1). In particular, ERSSTv4, and then "


id: 70adc07d91ddce7594d968576845bcfe
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17083
content:
"There is a distinction (Annex IV.2.3.1) between El Nino events \r\ncentred in the eastern Pacific ('Eastern Pacific' (EP) or 'classical' \r\nevents) and those centred in the Central Pacific ('Central Pacific' (CP) \r\nor 'Modoki' events), which have different typical teleconnections \r\n(e.g., Ashok et al., 2007; Ratnam et al., 2014; Capotondi et al., 2015; "


id: 1b88994f3b964f1bc572e1b80db9f76a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 2033
content:
"teleconnections associated with these, being beyond the range of \r\nvariability on decadal to millennial timescales. A high proportion of \r\nEl Nino events in the last 20-30 years have been based in the central, \r\nrather than eastern Pacific, but there is low confidence that this \r\nrepresents a long-term change. "


id: 41385bb46a17a0f812efc357db48a747
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 8654
content:
"Timmermann et  al., 2018). A number of studies, using a range of \r\nindicators, have found an increase in recent decades of the fraction \r\nof  CP El Nino events, particularly after 2000 (Yu and Kim, 2013; \r\nLubbecke and McPhaden, 2014; Pascolini-Campbell et  al., 2015; \r\nJiang and Zhu, 2018). Johnson (2013) found that the frequency of \r\nCP El Nino events had increased (although not significantly) over the \r\n1950-2011 period, being accompanied by a significant increase in \r\nthe frequency of La Nina events with a warm (as opposed to cool) \r\nwestern Pacific warm pool. A coral-based reconstruction starting \r\nin 1600 CE (Freund et  al., 2019) found that the ratio of CP to EP \r\nevents in the last 30 years was substantially higher than at any other \r\ntime over the last 400 years. Variations in the proportion of CP and \r\nEP events have also been found in earlier periods, with Carre et al. \r\n(2014) finding a period of high CP activity around 7 ka."


id: 8cbe60eafca09ef8998b182fbbdee88c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 21947
content:
"The AR5 did not provide an assessment of the Indian Ocean Dipole \r\n(IOD) records based on paleo reconstructions. For the instrumental \r\nera, AR5 reported that there were no trends in the IOD behaviour. \r\nHowever, the strength of the Indian Ocean Basin-wide (IOB) mode, \r\nquantified by the basin-scale averaged SST index, increased in all \r\nassessed periods except 1979-2012, but the AR5 neither quantified \r\ntrends nor provided a confidence statement. "


id: 52ba3cc81c381faf393634ecf3f211ca
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11831
content:
"From the coral d18O record from the Seychelles over 1854-1994, \r\nDu  et  al. (2014) showed a 3-7 year dominant period associated \r\nwith the IOB in response to ENSO forcing. They identified multi\u0002decadal variability in the IOB, with more active IOB phases during \r\n1870-1890, 1930-1955, and 1975-1992, while decadal variability in \r\nthe IOB dominated during 1940-1975 (Du et al., 2014). Evidence for \r\nchanges in IOB characteristics during earlier periods (e.g., MH, LGM) \r\nis limited. "


id: 4d63b7064713d19a29a42ee24ea93b3f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 10894
content:
"In summary, there is medium confidence that both ENSO amplitude \r\nand the frequency of high-magnitude events since 1950 are higher \r\nthan over the period from 1850 and possibly as far back as 1400, \r\nbut low confidence that they are outside the range of variability over \r\nperiods prior to 1400, or higher than the average of the Holocene \r\nas a whole. Overall, there is no indication of a recent sustained shift \r\nin ENSO or associated features such as the Walker Circulation, or in "


id: 3e6dbb14bfff7aafbdd01dcbdeecf96d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 8164
content:
"the seasonal evolution and the type of ENSO (Section 2.4.2) may \r\ninfluence the character of the IOD (Guo et al., 2015; Zhang et al., \r\n2015; Fan et al., 2016), the occurrence of some IOD events may be \r\nindependent of ENSO (Sun et al., 2015). "


id: 71550aaf89c122251304dc8f34f2e23c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17198
content:
"The role of decadal to multi-decadal variability has recently emerged \r\nas an important aspect of the IOD with many indications of the effects \r\nof Pacific Ocean processes on IOD variability through atmospheric \r\nand oceanic mechanisms (Dong et  al., 2016; Krishnamurthy and \r\nKrishnamurthy, 2016; Zhou et  al., 2017; Jin et  al., 2018). Positive \r\nevents in the 1960s and 1990s were linked to a relatively shallow \r\neastern Indian Ocean thermocline, and a primarily negative IOD \r\nstate in the 1970s and 1980s was related to a deeper thermocline \r\n(Ummenhofer et al., 2016). Positive IOD events may have increased \r\nin frequency during the second half of the 20th century (Abram et al., \r\n2020a, b). Earlier observations of apparent changes in the frequency \r\nand/or magnitude of the IOD events are considered unreliable, \r\nparticularly prior to the 1960s (Hernandez et  al., 2020). Although "


id: 584636610c150888604ab384de8f765d
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12788
content:
"To summarize, there is low confidence in any multi-decadal IOD \r\nvariability trend in the instrumental period due to data uncertainties \r\nespecially before the 1960s. In addition to data uncertainties, \r\nunderstanding of the IOB variability during the instrumental period is \r\nalso limited by large-scale warming of the Indian Ocean. Neither the \r\nIOD nor the IOB have exhibited behaviour outside the range implied \r\nby proxy records (low confidence)."


id: 4093d0d49118a0765e07bb0d4fb3bebf
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 8551
content:
"with a  predominantly positive phase until the end of the 1990s, \r\nbeing mainly negative afterwards. There was no significant change \r\nassessed in the PDO during the instrumental period as a whole, and \r\nno confidence level was assigned. Changes in the pre-instrumental \r\nera PDO were not assessed in AR5. "


id: fbd13a8d3c2d769ee6f2f7c49ba39c40
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 41670
content:
"The AR5 reported no changes in the Atlantic Meridional Mode \r\n(AMM) during the 20th century or shorter periods thereof. For the \r\nAtlantic Zonal Mode (AZM), also referred as the Atlantic Nino, \r\nthe AR5 reported increases during the 1950-2012 period but neither \r\nassessed trends nor provided a confidence statement. The AR5 did \r\nnot assess paleo evidence for the AZM and AMM."


id: 116a1bb7337c51fd1a3fd20709d0fb70
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 260
content:
"Paleo-reconstructions of these two modes remain rather limited. \r\nNonetheless, the interhemispheric cross-equatorial SST gradients linked \r\nto changes in ITCZ locations characteristic of the AMM has been found \r\nduring the LGM, Heinrich Stadial 1, and the MH, with the largest shift \r\noccurring during HS1 (McGee et al., 2014). Similarly, the dipole-like SST \r\npattern in the South Atlantic subtropics, which is related to the AZM \r\n(Venegas et al., 1996; Morioka et al., 2011; Nnamchi et al., 2016, 2017; \r\nLubbecke et al., 2018; Rouault et al., 2018; Foltz et al., 2019), has been \r\nreconstructed using SST proxies from marine sediment cores during \r\nthe past 12 kyr (Wainer et al., 2014). The reconstructed index captures \r\ntwo significant cold events that occurred during the 12.9-11.6 ka and \r\n8.6-8.0 ka periods in the South Atlantic (Wainer et al., 2014). "


id: 2adadb24dade506f9a3400283576c385
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 4771
content:
"The PDO and IPO indices are significantly correlated during the \r\ninstrumental period, showing regime shifts in the 1920s, 1940s, 1970s \r\nand around 1999. Positive PDV phases were observed from the 1920s \r\nto the mid-1940s and from the late 1970s to the late 1990s, while \r\nnegative phases occurred from mid-1940s until the late 1970s, and \r\nsince 1999 (Figure 2.38; Han et al., 2014; Chen and Wallace, 2015; \r\nM. Newman et al., 2016). The associated spatial patterns are quite \r\nsimilar, but the PDO pattern exhibits stronger SST anomalies in the \r\nextra-tropical North Pacific than the IPO (Chen and Wallace, 2015). \r\nThe strength and structure of the SST patterns also differ among the \r\nperiods (M. Newman et al., 2016)."


id: 82524c610b17df70260387f998e8cc78
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20055
content:
"In summary, confidence is low in any sustained changes to the AZM \r\nand AMM variability in instrumental observations. There is very low \r\nconfidence in changes of the paleo AZM and AMM due to extremely \r\nlimited availability of paleo reconstructions."


id: d8d28e2fc6990b3847b72d3613ea0489
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 35438
content:
"Instrumental observations are sparse prior to 1950, and thus \r\nthe fidelity of any PDV index derived for the second part of the \r\n19th  century and early decades of the 20th century is relatively \r\nlow (Figure 2.38; Deng et  al., 2013; Wen et  al., 2014). This results \r\nin low agreement in the classification of the PDO/IPO phase among \r\nseveral indices, even during recent years with the availability of high\u0002quality data. Nevertheless, the teleconnection patterns are robust \r\nregardless of the index used to characterize the PDO (McAfee, 2017). \r\nAnalysis of time series of PDO and IPO highlights the (multi-) decadal \r\nnature  of this mode of variability with no significant trends, but \r\nhighlights a recent switch from a positive to a negative phase since \r\n1999/2000 across all indicators (England et al., 2014; Henley, 2017). "


id: ea9926603bbec6ca292c47efad906b92
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 38635
content:
"Pacific Decadal Variability (PDV) refers to the ocean-atmosphere \r\nclimate variability over the Pacific Ocean at decadal-to-interdecadal \r\ntime scales and is usually described by the Pacific Decadal Oscillation \r\n(PDO) or the Inter-decadal Pacific Oscillation (IPO) indices. The AR5 \r\nand SROCC reported a large shift of the PDO in the late 1970s, "


id: 545c8ae2ddf1f5ae622ce3318a2e4c9a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12120
content:
"Instrumental observations show that AMV is characterized by \r\nbasin-wide warm and cool periods with an average variation in \r\nSST of about 0.4degC, but with larger variations in the North Atlantic \r\nsubpolar gyre. Despite small differences in indices used to define the \r\nAMV (Annex IV), they all show warm periods occurring approximately \r\nbetween 1880-1900, 1940-1960, and from the mid-1990s to \r\npresent, with cool periods in between (Figure 2.38) but no overall \r\nsustained change during the instrumental period (Booth et al., 2012; \r\nGulev et al., 2013; Bellomo et al., 2018)."


id: 3b0ce944b2c52c5cd9e1310a5d354c52
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
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vector_id: 7579
content:
"The oceanic changes are seen in salinity and temperature variations \r\nover the upper 3000 m of the North Atlantic (Polyakov et al., 2005; \r\nKeenlyside et al., 2015), and in sea level variations in the western \r\nNorth Atlantic along the Gulf Stream passage (McCarthy et  al., \r\n2015). The pattern and strength of the AMV differs among the \r\nperiods (e.g.,  Svendsen et  al., 2014b; Reynolds et  al., 2018) and \r\nthere are indications that there may have been a shift since 2005 \r\ntoward a negative phase of the AMV (Robson et al., 2016)."


id: 5027995ea733eb8fe9ff21111144c792
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11386
content:
"In summary, no sustained change in AMV indices has been \r\nobserved over the instrumental period (high confidence). However, \r\ninstrumental records may not be long enough to distinguish any \r\noscillatory behaviour from trends in the AMV. There is low confidence\r\nin the paleo AMV reconstructions due to a paucity of high-resolution \r\nrecords. "


id: 299513264c69f32aacb6e229db27e07
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 4543
content:
"In summary, the PDV in the instrumental record is dominated by \r\n(multi-)decadal-scale shifts between positive and negative phases \r\nover the last 150 years with no overall trend (high confidence). There \r\nis low confidence in paleo-PDV reconstructions due to discrepancies \r\namong the various available time series in terms of phasing and \r\ntiming. However, there is high confidence in the occurrence of a shift \r\nfrom predominantly negative to positive PDO conditions from the \r\nmiddle to the late Holocene. "


id: 84f23b7bea488feaed877f1de7086186
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20531
content:
"The assessment in this chapter is based upon an ever-expanding \r\nvolume of available proxy and observational records and a growing \r\nbody of literature. Since AR5, improvements have been made in all \r\naspects of data collection, data curation, data provision and data \r\nanalysis permitting improved scientific insights. The chapter has \r\nalso benefitted from the availability of new products from a range \r\nof emerging, mainly space-based, observing capabilities and new \r\ngenerations of reanalysis products. However, a number of key \r\nchallenges still remain which, if addressed, would serve to strengthen \r\nfuture reports."


id: 842bafddf73a6c75973746df420c7ac5
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20411
content:
"The AR5 reported no robust changes in Atlantic Multi-decadal Variability \r\n(AMV) reconstructions based on paleo records due to low consistency \r\nbetween different AMV reconstructions prior to 1900. AR5 concluded \r\nthat there have been no significant trends in the AMV index during the \r\ninstrumental period and there was difficulty in interpreting the AMV \r\nsignal because of the long-term underlying SST warming trend. "


id: 6da6b7d64fdb40da78d96d15fe8759b2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16548
content:
"The AR5 conclusions about large uncertainties in AMV paleo \r\nreconstructions (Hernandez et  al., 2020) have been reinforced by \r\nrecent studies of tree rings (J. Wang et  al., 2017b), Greenland ice \r\n(Chylek et  al., 2012), and corals (Kilbourne et  al., 2014; Svendsen \r\net al., 2014b; J. Wang et al., 2017b). The AMV exhibited a generally \r\npositive state over the first millennium of the CE (Mann et al., 2009; \r\nSingh et  al., 2018). Paleo reconstructions over the last millennium \r\nconsistently show a negative AMV phase during 1400-1850 CE and \r\na positive phase during 900-1200 CE (Mann et al., 2009; J. Wang \r\net  al., 2017b; Singh et  al., 2018), consistent with warmer surface \r\ntemperatures from tropical Atlantic records (Kilbourne et al., 2014). "


id: ae313cb4eea9b8c8c0e583c4d2e2544e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 27884
content:
"forcers, especially for components of the climate system where \r\nthe dominant response is on multi-decadal and longer time \r\nscales. Targeted rescue of early marine data records, especially \r\nfrom waters of the tropical oceans and the Southern Ocean, could \r\nhelp constrain modes of variability and important teleconnection \r\nchanges in, for example, the hydrological cycle and patterns of \r\nglobal temperature change. {2.2, 2.3, 2.4}"


id: d8ea00f00d9b1d2cff467908b9af4b92
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 35456
content:
"The authors of Chapter 2 would like to extend their gratitude to \r\nSara Veasey, Deborah Riddle, Deborah Misch (all NOAA NCEI, USA) \r\nand Robert Fawcett (BoM, Australia) for providing substantial \r\nsupport in the production and finalization of all figures. We wish \r\nto acknowledge Raphael Neukom (University of Bern, Switzerland) \r\nand Michael Bosilovich (NASA/GFSC, USA) for their assistance in the \r\nprovision of data."


id: 750ca09d21b9145b8b4a5d3f7278da9
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 17828
content:
"Earth's climate has always changed naturally, but both the global extent and rate of recent warming are unusual. \r\nThe recent warming has reversed a slow, long-term cooling trend, and research indicates that global surface \r\ntemperature is higher now than it has been for millennia."


id: 95e7df0f1ffb1f5732d741754127acb3
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 23571
content:
"While climate can be characterized by many variables, temperature is a key indicator of the overall climate state, and \r\nglobal surface temperature is fundamental to characterizing and understanding global climate change, including \r\nEarth's energy budget. A rich variety of geological evidence shows that temperature has changed throughout \r\nEarth's history. A variety of natural archives from around the planet, such as ocean and lake sediments, glacier \r\nice and tree rings, shows that there were times in the past when the planet was cooler, and times when it was \r\nwarmer. While our confidence in quantifying large-scale temperature changes generally decreases the farther \r\nback in time we look, scientists can still identify at least four major differences between the recent warming and \r\nthose of the past."


id: 6ae70411d97091da64ab55e3efe52e27
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16094
content:
"It's warming almost everywhere. During decades and centuries of the past 2000 years, some regions warmed \r\nmore than the global average while, at the same time, other regions cooled. For example, between the 10th \r\nand 13th centuries, the North Atlantic region warmed more than many other regions. In contrast, the pattern of \r\nrecent surface warming is globally more uniform than for other decadal to centennial climate fluctuations over \r\nat least the past two millennia."


id: dc323c3a3ffb39c1f458aa90883808a6
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 36014
content:
"Recent warming reversed a long-term global cooling trend. Following the last major glacial period, global \r\nsurface temperature peaked by around 6500 years ago, then slowly cooled. The long-term cooling trend was \r\npunctuated by warmer decades and centuries. These fluctuations were minor compared with the persistent and \r\nprominent warming that began in the mid-19th century when the millennial-scale cooling trend was reversed. "


id: f42f833819dd1fb62e3032384bd519ec
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 40332
content:
"It's been a long time since it's been this warm. Averaged over the globe, surface temperatures of the past decade \r\nwere probably warmer than when the long cooling trend began around 6500 years ago. If so, we need to look \r\nback to at least the previous interglacial period, around 125,000 years ago, to find evidence for multi-centennial \r\nglobal surface temperatures that were warmer than now. "


id: 5f17ce229b4a04e6b74f4d50692231ef
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 14031
content:
"Previous temperature fluctuations were caused by large-scale natural processes, while the current warming is \r\nlargely due to human causes (see, for example, FAQ 1.3, FAQ 3.1). But understanding how and why temperatures \r\nhave changed in the past is critical for understanding the current warming and how human and natural \r\ninfluences will interact to determine what happens in the future. Studying past climate changes also makes it \r\nclear that, unlike previous climate changes, the effects of recent warming are occurring on top of stresses that \r\nmake humans and nature vulnerable to changes in ways that they have never before experienced (for example, \r\nsee FAQ 11.2, FAQ12.3). "


id: c88a22a1a02eda4aec34e6b99ec17d72
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 32588
content:
"Climate has always changed, but warming like that of recent \r\ndecades has not been seen for millennia or longer."


id: 21edacaac7aa8fe3cc9fe3bfed0885f
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 3194
content:
"The evidence for climate change rests on more than just increasing surface temperatures. A broad range of \r\nindicators collectively leads to the inescapable conclusion that we are witnessing rapid changes to many aspects \r\nof our global climate. We are seeing changes in the atmosphere, ocean, cryosphere, and biosphere. Our scientific \r\nunderstanding depicts a coherent picture of a warming world."


id: 975debd573abec028ce63edf39fc29d4
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 23837
content:
"We have long observed our changing climate. From the earliest scientists taking meteorological observations \r\nin the 16th and 17th centuries to the present, we have seen a revolution in our ability to observe and diagnose \r\nour changing climate. Today we can observe diverse aspects of our climate system from space, from aircraft \r\nand weather balloons, using a range of ground-based observing technologies, and using instruments that can \r\nmeasure to great depths in the ocean. "


id: 84fd73e351c57b6fadd7c8f094c67529
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20538
content:
"Observed changes in key indicators point to warming over land areas. Global surface temperature over land has \r\nincreased since the late 19th century, and changes are apparent in a variety of societally relevant temperature \r\nextremes. Since the mid-1950s the troposphere (i.e., the lowest few km of the atmosphere) has warmed, and \r\nprecipitation over land has increased. Near-surface specific humidity (i.e., water vapour) over land has increased \r\nsince at least the 1970s. Aspects of atmospheric circulation have also evolved since the mid-20th century, including \r\na poleward shift of mid-latitude storm tracks."


id: f0924d2112eb01c3e3f9a6a09efd9c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 39699
content:
"Changes in the global ocean point to warming as well. Global average sea surface temperature has increased \r\nsince the late 19th century. The heat content of the global ocean has increased since the 19th century, with more \r\nthan 90% of the excess energy accumulated in the climate system being stored in the ocean. This ocean warming \r\nhas caused ocean waters to expand, which has contributed to the increase in global sea level in the past century. \r\nThe relative acidity of the ocean has also increased since the early 20th century, caused by the uptake of carbon \r\ndioxide from the atmosphere, and oxygen loss is evident in the upper ocean since the 1970s."


id: 78b5e8ccbc3908e6d216c79e09999eae
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 18430
content:
"Significant changes are also evident over the cryosphere - the portion of the Earth where water is seasonally or \r\ncontinuously frozen as snow or ice. There have been decreases in Arctic sea ice area and thickness and changes \r\nin Antarctic sea ice extent since the mid-1970s. Spring snow cover in the Northern Hemisphere has decreased \r\nsince the late-1970s, along with an observed warming and thawing of permafrost (perennially frozen ground). \r\nThe Greenland and Antarctic ice sheets are shrinking, as are the vast majority of glaciers worldwide, contributing \r\nstrongly to the observed sea level rise. "


id: a7784275ea374c00157596aef1223982
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 26677
content:
"Many aspects of the biosphere are also changing. Over the last century, long-term ecological surveys show that \r\nmany land species have generally moved poleward and to higher elevations. There have been increases in green \r\nleaf area and/or mass (i.e., global greenness) since the early 1980s, and the length of the growing season has \r\nincreased over much of the extratropical Northern Hemisphere since at least the mid-20th century. There is also \r\nstrong evidence that various phenological metrics (such as the timing of fish migrations) for many marine species \r\nhave changed in the last half century."


id: 5119b95761a160650913f13a02724d63
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11550
content:
"Change is apparent across many components of the climate system. It has been observed using a very broad range \r\nof techniques and analysed independently by numerous groups around the world. The changes are consistent in \r\npointing to a climate system that has undergone rapid warming since the industrial revolution."


id: 7f43ab85da1d730e331aa007726146f3
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 19546
content:
"Krishna M.Achuta Rao (India), Rondrotiana Barimalala (South Africa/Madagascar), Marcelo Barreiro \r\nParrillo (Uruguay), Nicolas Bellouin (United Kingdom/France), Christophe  Cassou (France), \r\nPaul J. Durack (United States of America/Australia), Yu Kosaka (Japan), Shayne McGregor (Australia), \r\nSeung-Ki Min (Republic of Korea), Olaf Morgenstern (New Zealand/Germany), Ying Sun (China)"


id: eb4797ee22f25f59a1bd1293ab14aa5a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 38748
content:
"Tomas Halenka (Czech Republic), Jose A. Marengo Orsini (Brazil/Peru), Daniel Mitchell \r\n(United Kingdom)"


id: 9e3ac7f31dd73947c46370838b886d30
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 25066
content:
"Eyring, V., N.P. Gillett, K.M. Achuta Rao, R. Barimalala, M. Barreiro Parrillo, N. Bellouin, C. Cassou, P.J. Durack, \r\nY. Kosaka, S.  McGregor, S. Min, O. Morgenstern, and Y. Sun, 2021: Human Influence on the Climate System. In \r\nClimate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment \r\nReport of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. \r\nConnors, C. Pean, S. Berger, N. Caud, Y. Chen, L.  Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. \r\nMatthews, T.K. Maycock, T. Waterfield, O. Yelekci, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, \r\nCambridge, United Kingdom and New York, NY, USA, pp. 423-552, doi:10.1017/9781009157896.005."


id: 570948e456ff143d3173a3fe4998c08
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12566
content:
"It is unequivocal that human influence has warmed the \r\natmosphere, ocean and land since pre-industrial times. Combining \r\nthe evidence from across the climate system increases the level of \r\nconfidence in the attribution of observed climate change to human \r\ninfluence and reduces the uncertainties associated with assessments \r\nbased on single variables. Large-scale indicators of climate change in \r\nthe atmosphere, ocean, cryosphere and at the land surface show clear \r\nresponses to human influence consistent with those expected based \r\non model simulations and physical understanding. {3.8.1}"


id: a26b7f580bf862c1874121b6c0540078
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 25797
content:
"The slower rate of GMST increase observed over 1998-2012 \r\ncompared to 1951-2012 was a temporary event followed \r\nby a strong GMST increase (very high confidence). Improved \r\nobservational datasets since AR5 show a larger GMST trend over \r\n1998-2012 than earlier estimates. All the observed estimates of \r\nthe 1998-2012 GMST trend lie within the 10th-90th percentile \r\nrange of CMIP6 simulated trends (high confidence). Internal \r\nvariability, particularly Pacific Decadal Variability, and variations in \r\nsolar and volcanic forcings partly offset the anthropogenic surface \r\nwarming trend over the 1998-2012 period (high confidence). Global \r\nocean heat content continued to increase throughout this period, \r\nindicating continuous warming of the entire climate system (very "


id: ede64f6a86df80298aeb3c72b79e9e4e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 39221
content:
"chapter the phrase 'human influence has contributed to' an observed change means that the response to human influence is non-zero and consistent in sign with the observed change."


id: d25a95dfc8a98c8e2984343b52a89453
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 34360
content:
"high confidence). Since 2012, GMST has warmed strongly, with the \r\npast five years (2016-2020) being the warmest five-year period \r\nin the instrumental record since at least 1850 (high confidence). \r\n{Cross-Chapter Box 3.1, 3.3.1; 3.5.1}"


id: 68bfeb1198eb8f6b49fd9394a30ef697
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 15697
content:
"It is very likely that anthropogenic forcing, mainly due to \r\ngreenhouse gas increases, was the main driver of Arctic sea \r\nice loss since the late 1970s. There is new evidence that increases \r\nin anthropogenic aerosols have offset part of the greenhouse \r\ngas-induced Arctic sea ice loss since the 1950s (medium confidence). \r\nIn the Arctic, despite large differences in the mean sea ice state, loss \r\nof sea ice extent and thickness during recent decades is reproduced \r\nin all CMIP5 and CMIP6 models (high confidence). By contrast, global \r\nclimate models do not generally capture the small observed increase \r\nin Antarctic sea ice extent during the satellite era, and there is low \r\nconfidence in attributing the causes of this change. {3.4.1}"


id: b1fa1d5977cba9781a0069f3ba59411a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 28533
content:
"It is likely that human influence has contributed to3 moistening \r\nin the upper troposphere since 1979. Also, there is medium \r\nconfidence that human influence contributed to a global increase \r\nin annual surface specific humidity, and medium confidence that it \r\ncontributed to a decrease in surface relative humidity over mid-latitude \r\nNorthern Hemisphere continents during summertime. {3.3.2}"


id: 3dc8ac4b12806f4c494cb75ddf8013f3
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 8036
content:
"It is very likely that human influence contributed to the \r\nobserved reductions in Northern Hemisphere spring snow cover \r\nsince 1950. The seasonal cycle in Northern Hemisphere snow cover is \r\nbetter reproduced by CMIP6 than by CMIP5 models (high confidence). \r\nHuman influence was very likely the main driver of the recent global, \r\nnear-universal retreat of glaciers. It is very likely that human influence \r\nhas contributed to the observed surface melting of the Greenland \r\nIce Sheet over the past two decades, and there is medium confidence\r\nin an anthropogenic contribution to recent overall mass loss from the \r\nGreenland Ice Sheet. However, there is only limited evidence, with \r\nmedium agreement, of human influence on Antarctic Ice Sheet mass \r\nbalance through changes in ice discharge. {3.4.2, 3.4.3}"


id: 83f772b246266fec1ca6f1678760d647
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 20370
content:
"Human-induced greenhouse gas forcing is the main driver of \r\nthe observed changes in hot and cold extremes on the global \r\nscale (virtually certain) and on most continents (very likely).\r\nIt is likely that human influence, in particular due to greenhouse \r\ngas forcing, is the main driver of the observed intensification of \r\nheavy precipitation in global land regions during recent decades. \r\nThere is high confidence in the ability of models to capture the \r\nlarge-scale spatial distribution of precipitation extremes over land. \r\nThe magnitude and frequency of extreme precipitation simulated \r\nby CMIP6 models are similar to those simulated by CMIP5 models \r\n(high confidence). {Cross-Chapter Box 3.2}"


id: 179e600258bf26796f09bbd1f86445f8
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 1361
content:
"It is extremely likely that human influence was the main driver \r\nof the ocean heat content increase observed since the 1970s, \r\nwhich extends into the deeper ocean (very high confidence).\r\nSince AR5, there is improved consistency between recent observed \r\nestimates and model simulations of changes in upper (<700 m) ocean \r\nheat content, when accounting for both natural and anthropogenic \r\nforcings. Updated observations and model simulations show \r\nthat warming extends throughout the entire water column (high \r\nconfidence), with CMIP6 models simulating 58% of industrial-era \r\nheat uptake (1850-2014) in the upper layer (0-700 m), 21% in \r\nthe intermediate layer (700-2000 m) and 22% in the deep layer \r\n(>2000 m). The structure and magnitude of multi-model mean ocean \r\ntemperature biases have not changed substantially between CMIP5 \r\nand CMIP6 (medium confidence). {3.5.1}"


id: da02a20046504b9eafd877558717bc6c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 35660
content:
"It is likely that human influence has contributed to the poleward \r\nexpansion of the zonal mean Hadley cell in the Southern\r\nHemisphere since the 1980s. There is medium confidence that \r\nthe observed poleward expansion of the zonal mean Hadley cell in \r\nthe Northern Hemisphere is within the range of internal variability. \r\nThe causes of the observed strengthening of the Pacific Walker \r\ncirculation since the 1980s are not well understood, and the observed \r\nstrengthening trend is outside the range of trends simulated in the \r\ncoupled models (medium confidence). While CMIP6 models capture \r\nthe general characteristics of the tropospheric large-scale circulation \r\n(high confidence), systematic biases exist in the mean frequency of \r\natmospheric blocking events, especially in the Euro-Atlantic sector, \r\nsome of which reduce with increasing model resolution (medium \r\nconfidence). {3.3.3}"


id: c78a4f3ef1dcbb28e2d70d05d5ea8d17
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updated_at: 2023-04-19 13:21:33
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index: climate_gpt_v2
vector_id: 32415
content:
"It is extremely likely that human influence has contributed \r\nto observed near-surface and subsurface ocean salinity \r\nchanges since the mid-20th century. The associated pattern of \r\nchange corresponds to fresh regions becoming fresher and salty \r\nregions becoming saltier (high confidence). Changes to the coincident \r\natmospheric water cycle and ocean-atmosphere fluxes (evaporation \r\nand precipitation) are the primary drivers of the observed basin-scale \r\nsalinity changes (high confidence). The observed depth-integrated \r\nbasin-scale salinity changes have been attributed to human influence, \r\nwith CMIP5 and CMIP6 models able to reproduce these patterns "


id: 64ede94eeb49c8295cc4030f4aa05bf5
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 15030
content:
"influence. There is high confidence that Earth system models simulate \r\na realistic time evolution of the global mean ocean carbon sink. {3.6.2}"


id: e79647b8a694e6bc45d7e3976212cefb
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 38052
content:
"only in simulations that include greenhouse gas increases (medium \r\nconfidence). The basin-scale changes are consistent across models and \r\nintensify through the historical period (high confidence). The structure \r\nof the biases in the multi-model mean has not changed substantially \r\nbetween CMIP5 and CMIP6 (medium confidence). {3.5.2}"


id: 54b178f0578eded9a42e6e1ee36f846c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12174
content:
"It is very likely that human influence has contributed to the \r\nobserved trend towards the positive phase of the Southern \r\nAnnular Mode (SAM) since the 1970s and to the associated \r\nstrengthening and southward shift of the Southern \r\nHemispheric extratropical jet in austral summer. The influence of \r\nozone forcing on the SAM trend has been small since the early 2000s \r\ncompared to earlier decades, contributing to a weaker SAM trend \r\nobserved over 2000-2019 (medium confidence). Climate models \r\nreproduce the summertime SAM trend well, with CMIP6 models \r\noutperforming CMIP5 models (medium confidence). By  contrast, \r\nthe cause of the Northern Annular Mode (NAM) trend towards its \r\npositive phase since the 1960s and associated northward shifts of \r\nthe Northern Hemispheric extratropical jet and storm track in boreal \r\nwinter is not well understood. Models reproduce the observed \r\nspatial features and variance of the SAM and NAM very well (high \r\nconfidence). {3.3.3, 3.7.1, 3.7.2}"


id: 3e5d7237f7be0e08e47e64d1d49fd1a4
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 8149
content:
"Combining the attributable contributions from glaciers, \r\nice-sheet surface mass balance and thermal expansion, it is \r\nvery likely that human influence was the main driver of the \r\nobserved global mean sea level rise since at least 1971. Since \r\nAR5, studies have shown that simulations that exclude anthropogenic \r\ngreenhouse gases are unable to capture the sea level rise due to \r\nthermal expansion (thermosteric) during the historical period \r\nand that model simulations that include all forcings (anthropogenic \r\nand natural) most closely match observed estimates. It is very likely\r\nthat human influence was the main driver of the observed global \r\nmean thermosteric sea level increase since 1970. {3.5.3, 3.5.1, 3.4.3}"


id: ae56b00e42e7d7891ff762d2262abefe
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 27904
content:
"While observations show that the Atlantic Meridional \r\nOverturning Circulation (AMOC) has weakened from the mid\u00022000s to the mid-2010s (high confidence) and the Southern \r\nOcean upper overturning cell has strengthened since the \r\n1990s (low confidence), observational records are too short \r\nto determine the relative contributions of internal variability, \r\nnatural forcing, and anthropogenic forcing to these changes \r\n(high confidence). No changes in Antarctic Circumpolar Current \r\ntransport or meridional position have been observed. The mean zonal \r\nand overturning circulations of the Southern Ocean and the mean \r\noverturning circulation of the North Atlantic (the Atlantic Meridional \r\nOverturning Circulation, AMOC) are broadly reproduced by CMIP5 \r\nand CMIP6 models. However, biases are apparent in the modelled \r\ncirculation strengths (high confidence) and their variability (medium \r\nconfidence). {3.5.4}"


id: b89a505a0c9754764db2e1296e4ea7a7
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 29685
content:
"Human influence has not affected the principal tropical modes \r\nof interannual climate variability or their associated regional \r\nteleconnections beyond the range of internal variability (high \r\nconfidence). Further assessment since AR5 confirms that climate and \r\nEarth system models are able to reproduce most aspects of the spatial \r\nstructure and variance of the El Nino-Southern Oscillation and Indian \r\nOcean Basin and Dipole modes (medium confidence). However, despite \r\na slight improvement in CMIP6, some underlying processes are still \r\npoorly represented. In the Tropical Atlantic basin, which contains the \r\nAtlantic Zonal and Meridional modes, major biases in modelled mean \r\nstate and variability remain. {3.7.3 to 3.7.5}"


id: bf24b6632f172c79a5fc2203a1e3076a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 30905
content:
"There is medium confidence that anthropogenic and volcanic \r\naerosols contributed to observed changes in the Atlantic \r\nMulti-decadal Variability (AMV) index and associated regional \r\nteleconnections since the 1960s, but there is low confidence\r\nin the magnitude of this influence. There is high confidence that \r\ninternal variability is the main driver of Pacific Decadal Variability \r\n(PDV) observed since pre-industrial times, despite some modelling \r\nevidence for potential human influence. Uncertainties remain in \r\nquantification of the human influence on AMV and PDV due to \r\nbrevity of the observational records, limited model performance in \r\nreproducing related sea surface temperature (SST) anomalies despite \r\nimprovements from CMIP5 to CMIP6 (medium confidence), and \r\nlimited process understanding of their key drivers. {3.7.6, 3.7.7}"


id: f72abbaa452a1f49c3fe025f12a6525c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 40859
content:
"The main driver of the observed increase in the amplitude of \r\nthe seasonal cycle of atmospheric CO2 is enhanced fertilization \r\nof plant growth by the increasing concentration of atmospheric \r\nCO2 (medium confidence). However, there is only low confidence\r\nthat this CO2 fertilization has also been the main driver of observed \r\ngreening because land management is the dominating factor in \r\nsome regions. Earth system models simulate globally averaged \r\nland carbon sinks within the range of observation-based estimates \r\n(high confidence), but global-scale agreement masks large regional \r\ndisagreements. {3.6.1}"


id: 2f53f2b7c023836d35f7bf5c83bdedf2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 5591
content:
"It is virtually certain that the uptake of anthropogenic CO2\r\nwas the main driver of the observed acidification of the global \r\nsurface open ocean. The observed increase in CO2 concentration \r\nin the subtropical and equatorial North Atlantic since 2000 is likely\r\nassociated in part with an increase in ocean temperature, a response \r\nthat is consistent with the expected weakening of the ocean carbon \r\nsink with warming. Consistent with AR5 there is medium confidence\r\nthat deoxygenation in the upper ocean is due in part to human "


id: a272a1c292348affb288f24764ea6cf9
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 25802
content:
"the IPCC Special Report on the Ocean and Cryosphere in a Changing \r\nClimate (SROCC; IPCC, 2019b), and assessments of attribution of \r\nchanges in the terrestrial carbon cycle in the IPCC Special Report on \r\nClimate Change and Land (SRCCL, IPCC, 2019a)."


id: 13bcb53adadb29229113d2ab34c8366e
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 685
content:
"This chapter assesses the extent to which the climate system has \r\nbeen affected by human influence and to what extent climate models \r\nare able to simulate observed mean climate, changes and variability. \r\nThis assessment is the basis for understanding what impacts of \r\nanthropogenic climate change may already be occurring and informs \r\nour confidence in climate projections. Moreover, an understanding \r\nof the amount of human-induced global warming to date is key to \r\nassessing our status with respect to the Paris Agreement goals of \r\nholding the increase in global average temperature to well below \r\n2degC above pre-industrial levels and pursuing efforts to limit the \r\ntemperature increase to 1.5degC (UNFCCC, 2016)."


id: 6630df63ba46f7292d9eab94f24a76d9
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 15243
content:
"process-based evaluation of climate and Earth system models against \r\nobservations that have rapidly advanced since the publication of AR5 \r\n(Eyring et al., 2019) as well as newly developed CMIP evaluation \r\ntools that allow a more rapid and comprehensive evaluation of the \r\nmodels with observations (Eyring et al., 2016a, b)."


id: b4985b3610b3dc71520223d9a18cda31
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 29022
content:
"(Eyring et al., 2016a; Gillett et al., 2016). In addition to the assessment \r\nof model performance and human influence on the climate system \r\nduring the instrumental era up to the present-day, this chapter also \r\nincludes evidence from paleo-observations and simulations over past \r\nmillennia (Kageyama et al., 2018)."


id: 6de6b0215ecf4bcbf3f7c10eb2717c7b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16597
content:
"An introduction to recent developments in detection and attribution \r\nmethods in the context of this Report is provided in the Cross\u0002Working Group Box on Attribution in Chapter 1. Here we discuss new \r\nmethods and improvements applicable to the attribution of changes in \r\nlarge-scale indicators of climate change which are used in this chapter."


id: d5fd17e89033b013c9b62b7aa76c2ea0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 34964
content:
"In order to improve the signal-to-noise ratio, observations and \r\nmodel-simulated responses are usually normalized by an estimate \r\nof internal variability derived from climate model simulations. This "


id: 4f210f24be2feaff1fd06fa1b895024a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 11206
content:
"New methods for model evaluation that are used in this chapter \r\nare described in Section 1.5.4. These include new techniques for "


id: 76535dde27e50575356381c8e6928c1a
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 18039
content:
"Climate change signals can vary with time and discriminant analysis \r\nhas been used to obtain more accurate estimates of time-varying \r\nsignals, and has been applied to different variables such as seasonal \r\ntemperatures (Jia and DelSole, 2012) and the South Asian monsoon \r\n(Srivastava and DelSole, 2014). The same approach was applied \r\nto separate aerosol forcing responses from other forcings (X. Yan \r\net al., 2016) and results using climate model output indicated \r\nthat detectability of the aerosol response is maximized by using \r\na  combination of temperature and precipitation data. Paeth et al. \r\n(2017) introduced a detection and attribution method applicable for \r\nmultiple variables based on a discriminant analysis and a Bayesian \r\nclassification method. Finally, a systematic approach has been \r\nproposed to translating quantitative analysis into a description of \r\nconfidence in the detection and attribution of a climate response \r\nto anthropogenic drivers (Stone and Hansen, 2016)."


id: 9a87f7b7186d29f29009a82aa16d2521
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 24430
content:
"Overall, these new fingerprinting and other probabilistic methods for \r\ndetection and attribution as well as efforts to better incorporate the \r\nassociated uncertainties have addressed a number of shortcomings in \r\npreviously applied detection and attribution techniques. They further \r\nstrengthen the confidence in attribution of observed large-scale \r\nchanges to a combination of external forcings as assessed in the \r\nfollowing sections."


id: 8c0bf5c735efa3a4e3a491a9cd3035d4
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 21808
content:
"Surface temperature change is the aspect of climate in which the \r\nclimate research community has had most confidence over past IPCC \r\nassessment reports. This confidence comes from the availability of longer \r\nobservational records compared to other indicators, a large response to \r\nanthropogenic forcing compared to variability in the global mean, and \r\na strong theoretical understanding of the key thermodynamics driving \r\nits changes (Collins et al., 2010; Shepherd, 2014). The AR5 assessed \r\nthat it was extremely likely that human activities had caused more than "


id: 22756543026d915f2d4c6804623fee4c
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 3283
content:
"Considering the difficulty in accounting for climate modelling \r\nuncertainties in the regression-based approaches, Ribes et al. (2017) \r\nintroduced a new statistical inference framework based on an "


id: 1e15550c02739071aa1491b7402cd0b1
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 2488
content:
"half of the observed increase in global mean surface temperature from \r\n1951 to 2010, and virtually certain that internal variability alone could \r\nnot account for the observed global warming since 1951 (Bindoff et al., \r\n2013). The AR5 also assessed with very high confidence that climate \r\nmodels reproduce the general features of the global-scale annual \r\nmean surface temperature increase over 1850-2011 and with high \r\nconfidence that models reproduce global and Northern Hemisphere \r\ntemperature variability on a wide range of time scales (Flato et al., \r\n2013). This section assesses the performance of the new generation \r\nCMIP6 models (see Table AII.5) in simulating the patterns, trends, and \r\nvariability of surface temperature, and the evidence from detection \r\nand attribution studies of human influence on large-scale changes in \r\nsurface temperature."


id: 1291d208a7c6a11f514b3a047bed7cbb
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 468
content:
"To be fit for detecting and attributing human influence on globally\u0002averaged surface temperatures, climate models need to represent, based \r\non physical principles, both the response of surface temperature  to \r\nexternal forcings and the internal variability in surface temperature \r\nover various time scales. This section assesses the performance of \r\nthose aspects in the latest generation CMIP6 climate models. See \r\nSection 3.8 for evaluation at continental scales, Chapter 10 for model \r\nevaluation in the context of regional climate information, and the Atlas \r\nfor region-by-region assessments of model performance."


id: 6bcc6e52a355c4874caaa374a1f6127b
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 16266
content:
"When interpreting model simulations of historical temperature change, \r\nit is important to keep in mind that some models are tuned towards \r\nrepresenting the observed trend in global mean surface temperature \r\nover the historical period (Hourdin et al., 2017). In Figure  3.4 the \r\nCMIP6 models that are documented to have been tuned to reproduce \r\nobserved warming, typically by tuning aerosol forcing or factors \r\nthat influence the model's ECS, are marked with an asterisk. Such \r\ntuning of a model can strongly impact its temperature projections \r\n(Mauritsen and Roeckner, 2020). However, Bock et al. (2020) reported "


id: f33eb03955990b1d143f0141c7ad51b2
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 40173
content:
"based attribution studies are based (Bock et al., 2020). Therefore, we \r\nassess with high confidence that the tuning of a small number of \r\nCMIP6 models to observed warming has not substantially influenced \r\nattribution results assessed in this chapter."


id: 4e05ce9cc077f62cd8fda4300d1ffcd9
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 10987
content:
"that there is no statistically significant difference in multi-model \r\nmean GSAT between the models that had been tuned based on \r\nobserved warming compared to those which had not. Moreover, \r\nonly two of thirteen models used for the Detection and Attribution \r\nModel Intercomparison Project (DAMIP) simulations on which CMIP6 \r\nattribution studies are based were tuned towards historical warming \r\n(Bock et al., 2020; Gillett et al., 2021). Further, tuning is done on \r\nglobally averaged quantities, so does not substantially change the \r\nspatio-temporal pattern of response on which many regression\u0002"


id: 3a446a26c4f3d4c9850cb3e7d6667620
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 7457
content:
"The reliance of detection and attribution studies on climate models \r\n(see  Section 3.2) requires that those models simulate realistic \r\nstatistics of internal variability on multi-decadal time scales. An \r\nincorrect estimate of variability in models would affect confidence "


id: dfbada721a4a0de69c38eff323d762d6
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 36611
content:
"Friedman et al. (2020) found biases in interhemispheric SST contrast \r\nin some models that may be consistent with underestimated cooling \r\nafter early-20th century eruptions or underestimated Pacific Decadal \r\nVariability, but could also be due to an imperfect separation between \r\ninternal variability and forced signal in the observations. Figure 3.2c, \r\nupdated from PAGES 2k Consortium (2019), compares modelled \r\ntemperatures to reconstructions over the last millennium. It indicates \r\nthat models reproduce the observed variability well, at least for the \r\ntime scales between 20 and 50 years that paleo reconstructions \r\ntypically resolve and that the figure represents. In summary, decadal "


id: 955e5640cf32f570cb0681dd479362d0
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 23479
content:
"is also higher than that from proxy reconstructions. CMIP6 models \r\nmay not share the underestimation by CMIP5 models of variability \r\nin decadal to multi-decadal modes of variability, such as Pacific \r\nDecadal Variability (Section 3.7.6; England et al., 2014; Thompson \r\net al., 2014; Schurer et al., 2015) and Atlantic Multi-decadal \r\nVariability (AMV), which may be partly forced, (see Section 3.7.7) \r\nbut this assessment is limited by the small number of available \r\nstudies. For the Southern Hemisphere, Hegerl et al. (2018) found an \r\ninstance of internal variability in the early 20th century larger than \r\nthat modelled, but indicated that could be an observational issue. "


id: 624eeaffb324470b95b81d56de446a29
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 14571
content:
"GMST variability simulated in CMIP6 models spans the range of \r\nresidual decadal variability in large-scale reconstructions (medium \r\nevidence, low agreement)."


id: 309d9b393485240c9cbccb4b62761036
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 5804
content:
"In summary, there is high confidence that CMIP6 models reproduce \r\nobserved large-scale mean surface temperature patterns and internal \r\nvariability as well as their CMIP5 predecessors, but with little evidence \r\nfor reduced biases. CMIP6 models also reproduce historical GSAT \r\nchanges similarly to their CMIP5 counterparts (medium confidence). \r\nHowever, in spite of model imperfections, there is very high confidence\r\nthat biases in surface temperature trends and variability simulated \r\nby the CMIP5 and CMIP6 ensembles are small enough to support \r\ndetection and attribution of human-induced warming."


id: 57a6eee9585101f281de92bb555b4a72
created_at: 2023-04-19 13:21:33
updated_at: 2023-04-19 13:21:33
content_type: text
index: climate_gpt_v2
vector_id: 12690
content:
"In addition, new literature suggests that anthropogenic forcing \r\nitself may locally increase or decrease variability in surface \r\ntemperatures (Screen et al., 2014; Qian and Zhang, 2015; Brown \r\net al., 2017; Park et al., 2018; Santer et al., 2018; Weller et al., \r\n2020). These studies imply limitations in the use of pre-industrial \r\ncontrol simulations to quantify the role of unforced variability over \r\nthe historical period. Some recent attribution studies (Gillett et al., \r\n2021; Ribes et al., 2021) have estimated variability from ensembles \r\nof forced simulations instead, which would be expected to resolve \r\nany such changes in variability."


id: 1f2ca30619b7a888fb8154e86faa7301
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 2691
content:
"Figure  3.5 shows the standard deviation of zonal-mean surface \r\ntemperature in CMIP6 pre-industrial control simulations and observed \r\ntemperature datasets. Results are consistent with those based \r\non CMIP5 models, which showed the largest model spread where \r\nvariability is also large, in the tropics and mid- to high latitudes (Flato \r\net al., 2013). Modelled variability is within a factor two of observed \r\nvariability over most of the globe. The apparent overestimation of \r\nhigh latitude variability in models compared to observations may \r\nbe due to interpolation and infilling over data sparse high latitude \r\nregions in the observational products shown here (Jones, 2016)."


id: 36470bf69a334319a517c4cf3b2eeb95
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 6789
content:
"here treated together in deriving assessed warming ranges. Studies \r\nalso increasingly validate their multi-model approaches using imperfect \r\nmodel tests (Schurer et al., 2018; Gillett et al., 2021; Ribes et al., 2021). \r\nAlternative techniques, based purely on statistical or econometric \r\napproaches, without the need for climate modelling, have also been \r\napplied (Estrada et al., 2013; Stern and Kaufmann, 2014; Dergiades \r\net al., 2016) and match the results of physically-based methods. The \r\nlarger range of attribution techniques and improvements to those \r\ntechniques increase confidence in the results compared to AR5."


id: a4627a6db24dcf477930ba25f88f8bfd
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 26125
content:
"In contrast, studies published since AR5 indicate that closely \r\nconstraining the separate contributions of greenhouse gas changes \r\nand aerosol changes to observed temperature changes remains \r\nchallenging. Nonetheless, attribution of warming to greenhouse gas \r\nforcing has been found as early as the end of the 19th century (Schurer \r\net al., 2014; Owens et al., 2017; PAGES 2k Consortium, 2019). Hegerl \r\net al. (2019) found that volcanism cooled global temperatures by \r\nabout 0.1degC between 1870 and 1910, then a lack of volcanic activity \r\nwarmed temperatures by about 0.1degC between 1910 and 1950, "


id: c9caf92eb1d6d7064b7796a515787611
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 32833
content:
"attributable to greenhouse gases and aerosols separately based on \r\nindividual models are not all consistent, and detection of the aerosol \r\ninfluence fails more often than that of greenhouse gases. Hence, \r\nresults of recent studies emphasize the need to use multi-model \r\nmeans to better constrain estimates of GSAT changes attributable to \r\ngreenhouse gas and aerosol forcing (Schurer et al., 2018; Gillett et al., \r\n2021; Ribes et al., 2021)."


id: 1176eccc670b22e81f7d7ca7ae2b2cc2
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 272
content:
"Figure 3.8 compares attributable changes in globally complete GSAT \r\nfor the period 2010-2019 relative to 1850-1900 from three detection \r\nand attribution studies, two of which use CMIP6 multi-model means \r\n(Gillett et al., 2021; Ribes et al., 2021), and an estimate based on \r\nassessed effective radiative forcing and transient and equilibrium \r\nclimate sensitivity (see Section 7.3.5.3). The reference period \r\n1850-1900 is used to assess attributable temperature changes \r\nbecause this is when the earliest gridded surface temperature \r\nrecords start, this is when the CMIP6 historical simulations start, "


id: 4ffa5d425dd8ba0ee2bd1a1f652c77b8
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
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index: climate_gpt_v2
vector_id: 11366
content:
"detected an anthropogenically forced response of inter-hemispheric \r\ncontrast in surface temperature change, which has a complex time \r\nevolution but shows the Northern Hemisphere cooling relative \r\nto the Southern Hemisphere until around 1975 but then warming \r\nafter that. Bonfils et al. (2020) attribute the Northern Hemisphere \r\nreversal to a combination of reduced aerosol forcing and greenhouse \r\ngas induced warming of Northern Hemisphere land masses. \r\nFriedman et al. (2020) found that CMIP5 models simulate the "


id: e69a70688dc4e8ce64fa1f1be1f7a49e
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 37867
content:
"of a different approach. This agreement enhances confidence in the \r\nmagnitude and causes of attributable surface temperature warming."


id: 65639388b454e2fe21b9bff6960e57e6
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 15107
content:
"The AR5 found high confidence for a major role for anthropogenic \r\nforcing in driving warming over each of the inhabited continents, \r\nexcept for Africa where they found only medium confidence\r\nbecause of limited data availability (Bindoff et al., 2013). At the \r\nhemispheric scale, Friedman et al. (2020) and Bonfils et al. (2020) "


id: b5a7656fd28e33becb429a397fdf21df
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 29186
content:
"aerosol forcing, and inter-model differences in the historical global \r\nmean temperature evolution and in diagnosed cooling attributable to \r\naerosols (Figure 3.8). Moreover, like previous generations of coupled \r\nmodel simulations, historical and single forcing CMIP6 simulations \r\nfollow a common experimental design (Eyring et al., 2016a; Gillett \r\net al., 2016) and are thus all driven by the same common set of \r\nforcings, even though these forcings are uncertain. Hence, forcing \r\nuncertainty is not directly accounted for in most of the attribution and \r\nmodel evaluation studies assessed here, although this limitation can \r\nto some extent be addressed by comparing with previous generation \r\nmulti-model ensembles or individual model studies using different \r\nsets of forcings."


id: d6de1a184d252c6651ce3f482d2c7391
created_at: 2023-04-19 13:21:34
updated_at: 2023-04-19 13:21:34
content_type: text
index: climate_gpt_v2
vector_id: 35111
content:
"Table  3.1 | Estimates of warming in GSAT attributable to human influence for different periods in degC, all relative to the 1850-1900 base period.\r\nUncertainty ranges are 5-95% ranges for individual studies and likely ranges for the assessment. The results shown in the table use the methods described in the three studies \r\nindicated, but applied to additional periods and the warming trend. Ribes et al. (2021) results were updated using a corrected natural forcing time series, and Haustein et al. \r\n(2017) results were updated to use HadCRUT5."


