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1,200 | AR6_WGI | 976 | 6 | Carbon dioxide continues to contribute the largest part (56 ± 16%) of this GHG ERF | high | 2 | train |
1,201 | AR6_WGI | 976 | 7 | As discussed in Section 7.3.3, aerosols have in total contributed an ERF of –1.1 [–1.7 to –0.4] W m–2 over 1750–2019 | medium | 1 | train |
1,202 | AR6_WGI | 977 | 15 | The total human forced GSAT change from 1750 to 2019 is calculated to be 1.29 [1.00 to 1.65] °C | high | 2 | train |
1,203 | AR6_WGI | 978 | 4 | Nonetheless, simple physically basedof a WMGHG warming of 1.58 [1.17 to 2.17] °C (high confidence), a warming from ozone changes of 0.23 [0.11 to 0.39] °C (high confidence), and a cooling of –0.50 [–0.22 to –0.96] °C from aerosol effects | medium | 1 | train |
1,204 | AR6_WGI | 978 | 6 | There is also a –0.06 [–0.15 to +0.01] °C contribution from surface reflectance changes which is dominated by land-use change | medium | 1 | train |
1,205 | AR6_WGI | 978 | 7 | Changes in solar and volcanic activity are assessed to have together contributed a small change of –0.02 [–0.06 to +0.02] °C since 1750 | medium | 1 | train |
1,206 | AR6_WGI | 978 | 17 | However, since 1980 the aerosol cooling trend has stabilized and may have started to reverse, so that over the last few decades the long-term warming has been occurring at a faster rate than would be expected due to CO 2 alone | high | 2 | train |
1,207 | AR6_WGI | 992 | 15 | Since AR5, several studies have confirmed that a shift from tundra to boreal forests and the associated albedo change leads to increased warming in Northern Hemisphere high latitudes | high | 2 | train |
1,208 | AR6_WGI | 992 | 24 | Given the limited number of studies, we take the full range of estimates discussed above for the biogeophysical feedback parameter, and assess the very likely range to be from 0.0 to +0.3 W m–2 °C–1, with a central estimate of +0.15 W m–2 °C–1 | low | 0 | train |
1,209 | AR6_WGI | 993 | 25 | As such, overall, on multi- centennial time scales the feedback parameter associated with ice sheets is likely negative (medium confidence), but on multi-millennial time scales by the time the ice sheets reach equilibrium, the feedback parameter is very likely positive | high | 2 | train |
1,210 | AR6_WGI | 1,003 | 13 | For both the MPWP and EECO, models are more consistent with the temperature and CO 2 proxies than at the time of AR5 | high | 2 | train |
1,211 | AR6_WGI | 1,003 | 14 | For the LGM Northern Hemisphere, which is the region with the most data and the time period with the least uncertainty in model boundary conditions, polar amplification in the PMIP4 ensemble mean is in good agreement with the proxies, especially for SAT | medium | 1 | train |
1,212 | AR6_WGI | 1,003 | 18 | It is very likely that the warming in the Arctic will be more pronounced than the global average over the 21st century | high | 2 | train |
1,213 | AR6_WGI | 1,003 | 19 | This is supported by models’ improved ability to simulate polar amplification during past time periods, compared with at the time of AR5 | high | 2 | train |
1,214 | AR6_WGI | 1,008 | 7 | The value of α’ is larger if quantified based on the observed pattern of warming since 1980 (Figure 2.11b) which is more distinct from the equilibrium warming pattern expected under CO 2 forcing | high | 2 | train |
1,215 | AR6_WGI | 1,011 | 3 | In summary, the process-based estimate of TCR is assessed to have the central value of 2.0°C with the likely range from 1.6 to 2.7 °C and the very likely range from 1.3 to 3.1 °C | high | 2 | train |
1,216 | AR6_WGI | 1,014 | 33 | Regression-based feedbacks thus provide estimates of the radiative feedbacks that are associated with internal climate variability (e.g., Brown et al., 2014), and do not provide a direct estimate of ECS | high | 2 | train |
1,217 | AR6_WGI | 1,015 | 8 | Estimates based on the response to volcanic eruptions agree with other lines of evidence (Knutti et al., 2017), but they do not constitute a direct estimate of ECS | high | 2 | train |
1,218 | AR6_WGI | 1,015 | 11 | However, there is robust evidence and high agreement across the lines of evidence that ECS is extremely likely greater than 1.6°C | high | 2 | train |
1,219 | AR6_WGI | 1,015 | 12 | There is robust evidence and medium agreement across the lines of evidence that ECS is very likely greater than 1.8°C and likely greater than 2.2°C | high | 2 | train |
1,220 | AR6_WGI | 1,015 | 13 | These ranges of ECS correspond to estimates based on historical global energy budget constraints (Section 7.5.2.1) under the assumption of no feedback dependence on evolving SST patterns (i.e., α’ = 0) and thus represent an underestimate of the true ECS ranges that can be inferred from this line of evidence | high | 2 | train |
1,221 | AR6_WGI | 1,015 | 15 | Global energy budget constraints indicate a central estimate (median) TCR value of 1.9°C and that TCR is likely in the range 1.5 to 2.3 °C and very likely in the range 1.3 to 2.7 °C | high | 2 | train |
1,222 | AR6_WGI | 1,018 | 1 | As such, based solely on the paleoclimate record, it is assessed to be very likely that ECS is greater than 1.5°C | high | 2 | train |
1,223 | AR6_WGI | 1,019 | 2 | Despite the large variation in individual studies at the extreme upper end, all except two studies (both of which are from glacial–interglacial time periods associated with low confidence) have central estimates that are below 6°C; overall we assess that it is extremely likely that ECS is below 8°C | high | 2 | train |
1,224 | AR6_WGI | 1,025 | 3 | The high ECS and TCR values can in some CMIP6 models be traced to improved representation of extratropical cloud feedbacks | medium | 1 | train |
1,225 | AR6_WGI | 1,025 | 5 | Solely based on its ECS or TCR values an individual ESM cannot be ruled out as implausible, though some models with high (greater than 5°C) and low (less than 2°C) ECS are less consistent with past climate change | high | 2 | train |
1,226 | AR6_WGI | 1,027 | 30 | Global ocean heat uptake is a smaller source of uncertainty in long-term surface warming | high | 2 | train |
1,227 | AR6_WGI | 1,030 | 22 | In summary, GWPs and GTPs for methane and nitrous oxide are slightly lower than in AR5 | medium | 1 | train |
1,228 | AR6_WGI | 1,030 | 29 | Estimates of the yield are 61% (Boucher et al., 2009) and 88% (Shindell et al., 2017), so the assessed range is 50–100% with a central value of 75% | low | 0 | train |
1,229 | AR6_WGI | 1,030 | 34 | Methane from fossil fuel sources has therefore slightly higher emissions metric values than those from biogenic sources | high | 2 | train |
1,230 | AR6_WGI | 1,035 | 10 | Hence, net zero CO 2 and net zero GHG, quantified using these new approaches, would both lead to approximately stable contributions to temperature change after net zero emissions are achieved | high | 2 | train |
1,231 | AR6_WGI | 1,073 | 8 | The overall effect of anthropogenic aerosols is to reduce global precipitation and alter large-scale atmospheric circulation patterns through their well- understood surface radiative cooling effect | high | 2 | train |
1,232 | AR6_WGI | 1,073 | 9 | Land- use and land-cover changes also drive regional water cycle changes through their influence on surface water and energy budgets | high | 2 | train |
1,233 | AR6_WGI | 1,073 | 11 | An increase in near-surface atmospheric water holding capacity of about 7% per 1°C of warming explains a similar magnitude of intensification of heavy precipitation events (from sub-daily up to seasonal time scales) that increases the severity of flood hazards when these extremes occur | high | 2 | train |
1,234 | AR6_WGI | 1,073 | 12 | The severity of very wet and very dry events increases in a warming climate | high | 2 | train |
1,235 | AR6_WGI | 1,073 | 13 | A slowdown of tropical circulation with global warming partly offsets the warming- induced strengthening of precipitation in monsoon regions | high | 2 | train |
1,236 | AR6_WGI | 1,073 | 15 | Greater warming over land than over the ocean alters atmospheric circulation patterns and, on average, reduces continental near-surface relative humidity, which contributes to regional drying | high | 2 | train |
1,237 | AR6_WGI | 1,073 | 18 | Global warming has contributed to an overall increase in atmospheric moisture and precipitation intensity (high confidence), increased terrestrial evapotranspiration (medium confidence), influenced global patterns in aridity (very likely), and enhanced contrasts in surface salinity and precipitation minus evaporation patterns over the oceans | high | 2 | train |
1,238 | AR6_WGI | 1,073 | 21 | Earlier onset of spring snowmelt and increased melting of glaciers have already contributed to seasonal changes in streamflow in high-latitude and low-elevation mountain catchments | high | 2 | train |
1,239 | AR6_WGI | 1,073 | 23 | Shifts in the tropical rain belt are associated with the inter-hemispheric temperature response to the time-evolving radiative influence of anthropogenic aerosols and the ongoing warming influence of greenhouse gases | high | 2 | train |
1,240 | AR6_WGI | 1,073 | 24 | Cooling in the Northern Hemisphere by sulphate aerosols explained a southward shift in the tropical rain belt and contributed to the Sahel drought from the 1970s to the 1980s (high confidence), subsequent recovery from which has been linked with greenhouse gas warming | medium | 1 | train |
1,241 | AR6_WGI | 1,073 | 25 | Observed changes in regional monsoon precipitation, especially over South Asia, East Asia and West Africa, have been limited over much of the 20th century due to increases driven by warming from greenhouse gases being counteracted by decreases due to cooling from anthropogenic aerosols | high | 2 | train |
1,242 | AR6_WGI | 1,073 | 28 | Urbanization has increased local precipitation (medium confidence) and resulting runoff intensity | high | 2 | train |
1,243 | AR6_WGI | 1,073 | 29 | Increased precipitation intensities have enhanced groundwater recharge, most notably in tropical regions | medium | 1 | train |
1,244 | AR6_WGI | 1,074 | 8 | Projected increases in precipitation amount and intensity will be associated with increased runoff in the northern high latitudes | high | 2 | train |
1,245 | AR6_WGI | 1,074 | 10 | Runoff from small glaciers will typically decrease through loss of ice mass, while runoff from large glaciers is likely to increase with increasing global warming until glacier mass becomes depleted | high | 2 | train |
1,246 | AR6_WGI | 1,074 | 12 | In the Mediterranean, south-western South America, and western North America, future aridification will far exceed the magnitude of change seen in the last millennium | high | 2 | train |
1,247 | AR6_WGI | 1,074 | 13 | Some tropical regions are also projected to experience increased aridity, including the Amazon basin and Central America | high | 2 | train |
1,248 | AR6_WGI | 1,074 | 15 | In the tropics and in the extratropics of both hemispheres during summer/warm season, interannual variability of precipitation and runoff over land is projected to increase at a faster rate than changes in seasonal mean precipitation amount | medium | 1 | train |
1,249 | AR6_WGI | 1,074 | 17 | Sub-seasonal precipitation variability is also projected to increase, with fewer rainy days but increased daily mean precipitation intensity over many land regions | high | 2 | train |
1,250 | AR6_WGI | 1,074 | 18 | Precipitation extremes will increase in almost all regions (high confidence), even where seasonal mean precipitation is projected to decrease | medium | 1 | train |
1,251 | AR6_WGI | 1,074 | 21 | Summer monsoon precipitation is projected to increase for the South, South East and East Asian monsoon domains, while North American monsoon precipitation is projected to decrease | medium | 1 | train |
1,252 | AR6_WGI | 1,074 | 22 | West African monsoon precipitation is projected to increase over the Central Sahel and decrease over the far western Sahel | medium | 1 | train |
1,253 | AR6_WGI | 1,074 | 26 | A continued poleward shift of storm tracks in the Southern Hemisphere (likely) and the North Pacific | medium | 1 | train |
1,254 | AR6_WGI | 1,074 | 29 | The annual contrast between the wettest and driest month of the year is likely to increase by 3–5% per 1°C in most monsoon regions in terms of precipitation, precipitation minus evaporation, and runoff | medium | 1 | train |
1,255 | AR6_WGI | 1,075 | 1 | Increasing horizontal resolution in global climate models improves the representation of small-scale features and the statistics of daily precipitation | high | 2 | train |
1,256 | AR6_WGI | 1,075 | 2 | High-resolution climate and hydrological models provide a better representation of land surfaces, including topography, vegetation and land-use change, which improve the accuracy of simulations of regional changes in the water cycle | high | 2 | train |
1,257 | AR6_WGI | 1,075 | 6 | Water cycle changes that have already emerged from natural variability will become more pronounced in the near term, but the occurrence of volcanic eruptions (either single large events or clustered smaller ones) can alter the water cycle for several years, decreasing global mean land precipitation and altering monsoon circulation | high | 2 | train |
1,258 | AR6_WGI | 1,075 | 8 | Non-linear water cycle responses are explained by the interaction of multiple drivers, feedbacks and time scales | high | 2 | train |
1,259 | AR6_WGI | 1,075 | 9 | Non-linear responses of regional runoff, groundwater recharge and water scarcity highlight the limitations of simple pattern-scaling techniques | medium | 1 | test |
1,260 | AR6_WGI | 1,075 | 10 | Water resources fed by melting glaciers are particularly exposed to non-linear responses | high | 2 | train |
1,261 | AR6_WGI | 1,075 | 14 | Continued Amazon deforestation, combined with a warming climate, raises the probability that this ecosystem will cross a tipping point into a dry state during the 21st century | low | 0 | train |
1,262 | AR6_WGI | 1,075 | 15 | The paleoclimate records show that a collapse in the Atlantic Meridional Overturning Circulation (AMOC) causes abrupt shifts in the water cycle | high | 2 | train |
1,263 | AR6_WGI | 1,075 | 19 | The impact of SRM can affect different regions in potentially disruptive ways | low | 0 | test |
1,264 | AR6_WGI | 1,078 | 17 | Detectable human influ ence on changes to the water cycle were found in atmospheric moisture content (medium confidence), global-scale changes of precipitation over land (medium confidence), intensification of heavy precipitation events over land regions where sufficient data networks exist | medium | 1 | train |
1,265 | AR6_WGI | 1,079 | 8 | Further evidence that anthropogenic global warming has caused an increase in the frequency, intensity and/or amount of heavy precipitation events at the global scale (medium confidence), as well as in drought occurrence in the Mediterranean region | medium | 1 | train |
1,266 | AR6_WGI | 1,079 | 11 | A key finding is that ‘limiting global warming to 1.5°C compared to 2°C would approximately halve the proportion of the world population expected to suffer water scarcity, although there is considerable variability between regions | medium | 1 | train |
1,267 | AR6_WGI | 1,079 | 24 | This Report indicates that since 1850–1900, land surface temperature has risen nearly twice as much as global surface temperature (high confidence), with an increase in dry climates | high | 2 | train |
1,268 | AR6_WGI | 1,079 | 25 | Land surface processes modulate the likelihood, intensity and duration of many extreme events including droughts (medium confidence) and heavy precipitation | medium | 1 | train |
1,269 | AR6_WGI | 1,079 | 26 | The direction and magnitude of hydrological changes induced by land use change and land surface feedbacks vary with location and season | high | 2 | train |
1,270 | AR6_WGI | 1,079 | 27 | Desertification exacerbates climate change through feedbacks involving vegetation cover, greenhouse gases and mineral dust aerosol | high | 2 | train |
1,271 | AR6_WGI | 1,079 | 28 | Urbanization increases extreme rainfall events over or downwind of cities | medium | 1 | train |
1,272 | AR6_WGI | 1,083 | 25 | Global precipitation increases due to GHGs are offset by the well-understood overall surface radiative cooling effect by aerosols | high | 2 | train |
1,273 | AR6_WGI | 1,083 | 26 | Over land, the average warming-related increase in precipitation is expected to be smaller than over the ocean due to increasing land –ocean thermal contrast and surface feedbacks, but the overall precipitation increase over land is generally reinforced by fast atmospheric responses to GHGs that strengthens convergence of winds | medium | 1 | train |
1,274 | AR6_WGI | 1,083 | 27 | Global mean precipitation and evaporation increase at a lower rate than atmospheric moisture per 1°C of global warming | high | 2 | train |
1,275 | AR6_WGI | 1,085 | 2 | To summarize, increased moisture transport from evaporative oceans to high precipitation regions of the atmospheric circulation will drive amplified P–E and salinity patterns over the ocean | high | 2 | test |
1,276 | AR6_WGI | 1,085 | 3 | Greater warming over land than ocean alters atmospheric circulation patterns and on average reduces continental near-surface relative humidity which along with vegetation feedbacks can contribute to regional decreases in precipitation | high | 2 | train |
1,277 | AR6_WGI | 1,087 | 9 | Mean tropical circulation is expected to slow with global warming (high confidence) but temporary multi-decadal strengthening is possible due to internal variability | medium | 1 | train |
1,278 | AR6_WGI | 1,087 | 10 | Slowing of the tropical circulation reduces the meridional P–E gradient over the Pacific and can partly offset thermodynamic amplification of P–E patterns and strengthening of monsoons | high | 2 | train |
1,279 | AR6_WGI | 1,088 | 8 | Melting of snowpack or glaciers can increase streamflow in high-latitude and high-altitude catchments until frozen water reserves are depleted | high | 2 | train |
1,280 | AR6_WGI | 1,089 | 31 | On a global level, warmer temperatures increase evaporative demand in the atmosphere, and thus (assuming sufficient soil moisture is available) increase moisture loss from evapotranspiration | high | 2 | train |
1,281 | AR6_WGI | 1,091 | 16 | In snow-dominated regions, high temperatures increase the fraction of precipitation falling as rain instead of snow and advance the timing of spring snowmelt | high | 2 | train |
1,282 | AR6_WGI | 1,091 | 22 | While potentially buffering water resource capacity, in some cases these interventions may unexpectedly increase vulnerability | medium | 1 | train |
1,283 | AR6_WGI | 1,091 | 29 | Beyond a lack of precipitation, changes in evapotranspiration are critical components of drought, because these can lead to soil moisture declines | high | 2 | train |
1,284 | AR6_WGI | 1,091 | 30 | Under very dry soil conditions, evapotranspiration becomes restricted and plants experience water stress in response to increased atmospheric demand | medium | 1 | train |
1,285 | AR6_WGI | 1,091 | 31 | Human activities and decision-making have a critical impact on drought severity | high | 2 | train |
1,286 | AR6_WGI | 1,092 | 27 | Urbanization can increase local precipitation (medium confidence) and resulting runoff intensity | high | 2 | train |
1,287 | AR6_WGI | 1,092 | 28 | A warming climate combined with direct human demand for water is expected to deplete groundwater resources in dry regions | high | 2 | train |
1,288 | AR6_WGI | 1,093 | 5 | These processes partially explain | medium | 1 | train |
1,289 | AR6_WGI | 1,093 | 6 | These processes also explain | high | 2 | train |
1,290 | AR6_WGI | 1,094 | 1 | In particular, aerosols induce intense convection at the Himalaya foothills during the pre-monsoon season, which generates a regional convergence there | medium | 1 | train |
1,291 | AR6_WGI | 1,096 | 6 | It is likely that the global land P–E variations observed since the late 1970s were dominated by internal variability, mostly linked to ENSO teleconnections | medium | 1 | train |
1,292 | AR6_WGI | 1,097 | 8 | There is further evidence of a faster increase since the 1980s | medium | 1 | train |
1,293 | AR6_WGI | 1,100 | 1 | There is, however, a detectable increase in northern high-latitude annual precipitation over land which has been primarily driven by human-induced global warming | high | 2 | train |
1,294 | AR6_WGI | 1,100 | 2 | Human influence has strengthened the zonal mean precipitation contrast between the wet tropics and dry subtropics since the 1980s | medium | 1 | train |
1,295 | AR6_WGI | 1,100 | 15 | In contrast to AR5, there are now consistent trends in pan evaporation and evapotranspiration at the global scale, given the recent increase in both variables since the mid-1990s | medium | 1 | train |
1,296 | AR6_WGI | 1,100 | 26 | Plant water use efficiency (WUE) is expected to rise with CO 2 levels | high | 2 | train |
1,297 | AR6_WGI | 1,103 | 44 | Both central and north-eastern Africa have experienced a decline in rainfall since about 1980 | high | 2 | train |
1,298 | AR6_WGI | 1,105 | 23 | In some regions of western North America and the Mediterranean, paleoclimate evidence suggests that recent warming has resulted in droughts that are of similar or greater intensity than those reconstructed over the last millennium | medium | 1 | train |
1,299 | AR6_WGI | 1,106 | 7 | In summary, human-induced global warming has been the primary driver of a global glacier recession since the early 20th century | high | 2 | train |
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