rlacombe/ClimateX huggingface dataset:
Recent estimates provide evidence of a WAfriM recovery from the mid-to-late 1990s, with more intense extreme events partly due to the combined effects of increasing GHG and decreasing anthropogenic aerosols over Europe and North America (IPCC AR6_WGI, confidence: high)
The NAmerM strengthened until the mid-Holocene period, in response to ice-emsheet retreat and rising summer insolation, but probably did not exceed the strength of the modern system (IPCC AR6_WGI, confidence: low)
The intensification recorded since about the 1970s has been partly driven by GHG emissions (IPCC AR6_WGI, confidence: medium)
Paleoclimate reconstructions and simulations suggest a weaker SAmerM during warmer epochs such as the Mid-Holocene or the 900–1100 period, and stronger monsoon during colder epochs such as the LGM or the 1400–1600 period (IPCC AR6_WGI, confidence: high)
In summary, no robust trend in atmospheric blocking has been detected in modern reanalyses and in CMIP6 historical simulations (IPCC AR6_WGI, confidence: medium)
The lack of trend is explained by strong internal variability and/or the competing effects of low-level Arctic amplification and upper-level tropical amplification of the equator- to-pole temperature gradient (IPCC AR6_WGI, confidence: medium)
Since the end of the 19th century, synchronous hydroclimate changes (IPCC AR6_WGI, confidence: medium)
Over equatorial East Africa the IOD affects the short rain season (IPCC AR6_WGI, confidence: medium)
The strength and frequency of the MJO have increased over the past century (IPCC AR6_WGI, confidence: medium)
In summary, multiple water cycle changes related to ENSO and IOD teleconnections have been observed across the 20th century (IPCC AR6_WGI, confidence: high)
The MJO amplitude has increased in the second half of the 20th century partly because of anthropogenic global warming (IPCC AR6_WGI, confidence: medium)
In summary, while the attribution of 20th century variations of the NAM/NAO is still unclear, there is a strong relationship with precipitation changes over Europe and in the Mediterranean region (IPCC AR6_WGI, confidence: high)
SAM teleconnections are associated with changes in moisture transport and extend to South America, Australia and Antarctica (IPCC AR6_WGI, confidence: high)
In this Report, Chapter 4 provides an updated assessment of global annual precipitation (Section 4.3.1), finding that it is very likely that annual precipitation averaged over all land regions continuously increases as global surface temperatures increase in the 21st century (IPCC AR6_WGI, confidence: high)
In general, there will be increases in moisture transport into storm systems, monsoons and high latitudes (IPCC AR6_WGI, confidence: medium)
The AR5 assessed that the contrast of mean precipitation amount between dry and wet regions and seasons is expected to increase over most of the globe as temperatures increase (IPCC AR6_WGI, confidence: high)
Beyond annual or seasonal mean precipitation amounts, an implication of the parallel intensification of the global water cycle and of the increased residence time of atmospheric water vapour (Section 8.2.1) is that the distribution of daily and sub-daily precipitation intensities will experience significant changes (Pendergrass and Hartmann, 2014b; Pendergrass et al., 2015; Bador et al., 2018; Douville and John, 2021), with fewer but potentially stronger events (IPCC AR6_WGI, confidence: high)
Daily mean precipitation intensities, including extremes, are projected to increase over most regions (IPCC AR6_WGI, confidence: high)
The number of dry days is projected to increase over the subtropics, Amazonia, and Central America (IPCC AR6_WGI, confidence: medium)
In summary, the annual range of precipitation, water availability and streamflow will increase with global warming over subtropical regions and the Amazon (medium confidence), especially around the Mediterranean and across southern Africa (IPCC AR6_WGI, confidence: high)
The contrast between the wettest and driest month of the year is likely to increase by 3–5% °C–1 with global warming in most monsoon regions, in terms of precipitation, water availability (P–E) and runoff (IPCC AR6_WGI, confidence: medium)
CMIP5 models also project an increase in evapotranspiration over most land areas (IPCC AR6_WGI, confidence: medium)
Evapotranspiration increases in most land regions, except in areas that are projected to become moisture-limited (due to reduced precipitation and increased evaporative demand), such as the Mediterranean, South Africa, and the Amazonian basin (IPCC AR6_WGI, confidence: medium)
The patterns of change increase in magnitude from low to high-emissions SSP scenarios (IPCC AR6_WGI, confidence: medium)
In summary, future projections indicate that anthropogenic forcings will drive an increase in global mean evaporation over most oceanic areas (high confidence) (Figure 8.17), an increase in global atmospheric demand (virtually certain) and an increase in evapotranspiration over most land areas, with the exception of moisture-limited regions (IPCC AR6_WGI, confidence: medium)
There is a likely increase in drought occurrence (IPCC AR6_WGI, confidence: medium)
Consistent with the coherent nature of warming in future projections, increases in vapour pressure deficit and evaporative demand are widespread and consistent across regions, seasons, and models, increasing in magnitude in accordance with the emissions scenario (IPCC AR6_WGI, confidence: high)
Even under a low-emissions scenario (SSP1-2.6), projections of soil moisture show significant decreases in the Mediterranean, southern Africa, and the Amazonian basin (IPCC AR6_WGI, confidence: high)
Under mid- and high-emissions scenarios (SSP2-4.5 and SSP5-8.5), coherent declines emerge across Europe, westernmost North Africa, south- western Australia, Central America, south-western North America, and south-western South America (IPCC AR6_WGI, confidence: high)
The percentage of land area experiencing drying is slightly lower when runoff is used as an aridity metric instead (20–30%); taking this into consideration, it is estimated that about a third of global land areas will experience at least moderate drying in response to anthropogenic emissions, even under SSP1-2.6 (IPCC AR6_WGI, confidence: medium)
The CORDEX South Asia multi-model ensemble projections indicate an increase in the frequency and severity of droughts over central and northern India during the 21st century, under the RCP4.5 and RCP8.5 scenarios (IPCC AR6_WGI, confidence: medium)
In general, these regions are expected to become drier both due to reduced precipitation (medium confidence) and increases in evaporative demand (IPCC AR6_WGI, confidence: high)
These same regions are likely to experience increases in drought duration and/or severity (IPCC AR6_WGI, confidence: high)
The magnitude of expected change scales with emissions scenarios (high confidence) but even under low-emissions trajectories, large changes in drought and aridity are expected to occur (IPCC AR6_WGI, confidence: high)
In the Mediterranean, Central Chile, and western North America, future aridification will far exceed the magnitude of change seen over the last millennium (IPCC AR6_WGI, confidence: high)
The SROCC noted that these declines are projected to continue almost everywhere over the 21st century (high confidence), with complete glacier loss expected in regions with only small glaciers (IPCC AR6_WGI, confidence: very high)
The SROCC concluded that cryosphere changes had already altered the seasonal timing and volume of runoff (very high confidence), which in turn had affected water resources and agriculture (IPCC AR6_WGI, confidence: medium)
Because of their lagged response to warming, glaciers will continue to lose mass for decades even if global temperature is stabilized (IPCC AR6_WGI, confidence: very high)
In summary, glaciers are projected to continue to lose mass under all emissions scenarios (IPCC AR6_WGI, confidence: very high)
Runoff from glaciers is projected to peak at different times in different places, with maximum rates of glacier mass loss in low latitude regions taking place in the next few decades in all scenarios (IPCC AR6_WGI, confidence: high)
While runoff from small glaciers will typically decrease because of glacier mass depletion, runoff from larger glaciers will increase with increasing global warming until glacier mass is similarly depleted, after which runoff peaks and then declines and which tends to occurs later in basins with larger glaciers and higher ice-cover fractions (IPCC AR6_WGI, confidence: high)
Glaciers in the Arctic and Antarctic will continue to lose mass through the latter half of the century and beyond (IPCC AR6_WGI, confidence: high)
It is likely that the zonal mean of the ITCZ will narrow and strengthen in the core region with projected surface warming (IPCC AR6_WGI, confidence: high)
Distinct regional shifts in the ITCZ will be associated with regional changes in precipitation amount and seasonality (IPCC AR6_WGI, confidence: medium)
The Hadley cells are projected to expand polewards with global warming, most notably in the SH (IPCC AR6_WGI, confidence: high)
Discrepancies between observed and simulated changes in SSTs in the tropics indicate that a temporary strengthening of the Walker Circulation can arise from internal variability (IPCC AR6_WGI, confidence: medium)
Since AR5, most studies have confirmed projected increases in South Asian monsoon precipitation (IPCC AR6_WGI, confidence: high)
Changes in seasonality (Box 8.2) are projected with a later monsoon onset (high confidence) over the Sahel and a late cessation (IPCC AR6_WGI, confidence: medium)
In summary, post-AR5 studies and newly available CMIP6 results indicate projected rainfall increases in the eastern-central WAfriM region but decreases in the west (high confidence), with a delayed wet season (IPCC AR6_WGI, confidence: medium)
Overall, WAfriM summer precipitation is projected to increase during the 21st century but with larger uncertainty noted under high-emissions scenarios (IPCC AR6_WGI, confidence: medium)
There is a projected increase in rainfall variability over northern Australia, with increased intensity of rainfall during the active or ‘burst’ phase (IPCC AR6_WGI, confidence: medium)
Section 11.7.1.5 assesses that the average tropical cyclone rain-rate is projected to increase with warming (high confidence), and peak rain rates are projected to increase at greater than the Clausius–Clapeyron scaling rate of 7% °C–1 warming in some regions due to increased low-level moisture convergence (IPCC AR6_WGI, confidence: medium)
This is projected to increase the intensity of heavy precipitation events on the west coast of the USA and in western Europe (IPCC AR6_WGI, confidence: high)
In summary, even though there is low confidence in how the tropical MoVs will change in the future (Sections 4.3.3.2 and 4.5.3.3), their regional hydrological consequences, in terms of precipitation, are projected to intensify (IPCC AR6_WGI, confidence: medium)
For example, the ENSO influence on precipitation over the Indo–Pacific sector is projected to strengthen and shift eastward (IPCC AR6_WGI, confidence: medium)
The MJO is projected to intensify in a warmer climate, with increased associated precipitation (IPCC AR6_WGI, confidence: medium)
In summary, projected changes in the intensity, frequency and phase of extratropical MoVs (see also Sections 4.3 and 4.5) may amplify regional changes in precipitation and contribute to an increase in their intra-seasonal and interannual variability (IPCC AR6_WGI, confidence: medium)
Regionally, there are potentially significant precipitation and atmospheric circulation changes associated with changes in extratropical dynamics (IPCC AR6_WGI, confidence: low)
For example, internal variability will continue to play an important role in the variability of river flows over France in coming decades (IPCC AR6_WGI, confidence: medium)
Major volcanic eruptions temporarily reduce total global and wet tropical region precipitation (high confidence) (Iles and Hegerl, 2014), can weaken or shift the ITCZ (Iles and Hegerl, 2014; Colose et al., 2016; Liu et al., 2016), and reduce summer monsoon rainfall (IPCC AR6_WGI, confidence: medium)
Monsoon precipitation in one hemisphere can be enhanced by the remote volcanic forcing occurring in the other hemisphere (IPCC AR6_WGI, confidence: medium)
The occurrence of volcanic eruptions in the coming century, either as single large events or clustered smaller ones, can alter the water cycle (see also Cross-Chapter Box 4.1), and regional drought events may be enhanced by co-occurring volcanic (Liu et al., 2016; Gao and Gao, 2017; Zambri et al., 2017) and GHG (e.g., Cook et al., 2018) forcing (IPCC AR6_WGI, confidence: low)
Volcanic eruptions may also lead to widespread precipitation anomalies up to several years following an eruption through their potential influence on the El Niño Southern Oscillation (IPCC AR6_WGI, confidence: low)
In summary, large volcanic eruptions reduce global mean precipitation, as well as precipitation in tropical wet regions (IPCC AR6_WGI, confidence: high)
In summary, there is both numerical and process-based evidence that terrestrial water cycle changes can be non-linear at the regional scale (IPCC AR6_WGI, confidence: high)
Non-linear regional responses of runoff, groundwater recharge and water scarcity have been documented based on both CMIP5 and CMIP6 models, and highlight the limitations of simple pattern-scaling techniques (IPCC AR6_WGI, confidence: medium)
Water resources fed by melting glaciers are particularly exposed to such non-linearities (IPCC AR6_WGI, confidence: high)
Observed transitions into and out of Green Sahara states are always faster than the underlying forcing, in agreement with theoretical considerations (IPCC AR6_WGI, confidence: high)
Both paleoclimate data and modelling experiments suggest that the timing and speed of the transition was spatially heterogeneous (IPCC AR6_WGI, confidence: high)
CMIP5 and CMIP6 models, some of which include dynamic vegetation schemes, cannot simulate the magnitude, nor the spatial extent, of greening and precipitation change associated with the last Green Sahara under standard mid-Holocene (6,000 years ago) boundary conditions (IPCC AR6_WGI, confidence: high)
In contrast, cirrus cloud thinning, a longwave radiation technique, results in increased global precipitation as it causes enhanced radiative cooling in the troposphere (IPCC AR6_WGI, confidence: medium)
The additional global warming caused by SRM termination may result in a rapid increase in global mean precipitation (IPCC AR6_WGI, confidence: medium)
Since the 1950s, the fastest surface warming has occurred in the Indian Ocean and in western boundary currents, while ocean circulation has caused slow warming or surface cooling in the Southern Ocean, equatorial Pacific, North Atlantic, and coastal upwelling systems (IPCC AR6_WGI, confidence: very high)
The long time scale also implies that the amount of deep-ocean warming is irreversible over centuries to millennia (IPCC AR6_WGI, confidence: very high)
On annual to decadal time scales, the redistribution of heat by the ocean circulation dominates spatial patterns of temperature change (IPCC AR6_WGI, confidence: high)
At longer time scales, the spatial patterns are dominated by additional heat, primarily stored in water masses formed in the Southern Ocean, and by weaker warming in the North Atlantic where heat redistribution caused by changing circulation counteracts the additional heat input through the surface (IPCC AR6_WGI, confidence: high)
Since the 1980s, they have approximately doubled in frequency (high confidence) and have become more intense and longer (IPCC AR6_WGI, confidence: medium)
The largest changes will occur in the tropical ocean and the Arctic (IPCC AR6_WGI, confidence: medium)
Based on recent refined analyses of the available observations, the global 0–200 m stratification is now assessed to have increased about twice as much as reported by SROCC, with a 4.9 ± 1.5% increase from 1970 to 2018 (IPCC AR6_WGI, confidence: high)
Western boundary currents have shifted poleward since 1993 (IPCC AR6_WGI, confidence: medium)
In the 21st century, consistent with projected changes in the surface winds, the East Australian Current Extension and Agulhas Current Extension will intensify, while the Gulf Stream and Indonesian Throughflow will weaken (IPCC AR6_WGI, confidence: medium)
Eastern boundary upwelling systems will change, with a dipole spatial pattern within each system of reduction at low latitude and enhancement at high latitude (IPCC AR6_WGI, confidence: high)
There is no tipping point for this loss of Arctic summer sea ice (IPCC AR6_WGI, confidence: high)
The practically ice-free state is projected to occur more often with higher greenhouse gas concentrations, and it will become the new normal for high-emissions scenarios by the end of this century (IPCC AR6_WGI, confidence: high)
Based on observational evidence, Coupled Model Intercomparison Project Phase 6 (CMIP6) models and conceptual understanding, the substantial satellite-observed decrease of Arctic sea ice area over the period 1979 –2019 is well described as a linear function of global mean surface temperature, and thus of cumulative anthropogenic carbon dioxide (CO 2) emissions, with superimposed internal variability (IPCC AR6_WGI, confidence: high)
The regionally opposing trends result primarily from changing regional wind forcing (IPCC AR6_WGI, confidence: medium)
This mass loss is driven by both discharge and surface melt, with the latter increasingly becoming the dominating component of mass loss with high interannual variability in the last decade (IPCC AR6_WGI, confidence: high)
The largest mass losses occurred in the north-west and the south-east of Greenland (IPCC AR6_WGI, confidence: high)
Mass losses from West Antarctic outlet glaciers outpaced mass gain from increased snow accumulation on the continent and dominated the ice-sheet mass losses since 1992 (IPCC AR6_WGI, confidence: very high)
These mass losses from the West Antarctic outlet glaciers were mainly induced by ice-shelf basal melt (high confidence) and locally by ice-shelf disintegration preceded by strong surface melt (IPCC AR6_WGI, confidence: high)
Parts of the East Antarctic Ice Sheet have lost mass in the last two decades (IPCC AR6_WGI, confidence: high)
The loss of ice from Greenland will become increasingly dominated by surface melt, as marine margins retreat and the ocean-forced dynamic response of ice-sheet margins diminishes (IPCC AR6_WGI, confidence: high)
In the Antarctic, dynamic losses driven by ocean warming and ice-shelf disintegration will likely continue to outpace increasing snowfall this century (IPCC AR6_WGI, confidence: medium)
Beyond 2100, total mass loss from both ice sheets will be greater under high-emissions scenarios than under low-emissions scenarios (IPCC AR6_WGI, confidence: high)
During the decade 2010–2019, glaciers lost more mass than in any other decade since the beginning of the observational record (IPCC AR6_WGI, confidence: very high)
For all regions with long-term observations, glacier mass in the decade 2010 –2019 is the smallest since at least the beginning of the 20th century (IPCC AR6_WGI, confidence: medium)
Because of their lagged response, glaciers will continue to lose mass at least for several decades even if global temperature is stabilized (IPCC AR6_WGI, confidence: very high)
Complete permafrost thaw in recent decades is a common phenomenon in discontinuous and sporadic permafrost regions (IPCC AR6_WGI, confidence: medium)
Permafrost warmed globally by 0.29 [0.17 to 0.41, likely range] °C between 2007 and 2016 (IPCC AR6_WGI, confidence: medium)
An increase in the active layer thickness is a pan-Arctic phenomenon (IPCC AR6_WGI, confidence: medium)
The volume of perennially frozen soil within the upper 3 m of the ground will decrease by about 25% per 1°C of global surface air temperature change (up to 4°C above pre-industrial temperature) (IPCC AR6_WGI, confidence: medium)
It is virtually certain that Northern Hemisphere snow cover extent will continue to decrease as global climate continues to warm, and process understanding strongly suggests that this also applies to Southern Hemisphere seasonal snow cover (IPCC AR6_WGI, confidence: high)
Northern Hemisphere spring snow cover extent will decrease by about 8% per 1°C of global surface air temperature change (up to 4°C above pre-industrial temperature) (IPCC AR6_WGI, confidence: medium)
GMSL rise has accelerated since the late 1960s, with an average rate of 2.3 [1.6 to 3.1] mm yr –1 over the period 1971–2018 increasing to 3.7 [3.2 to 4.2] mm yr –1 over the period 2006–2018 (IPCC AR6_WGI, confidence: high)
The contribution of Greenland and Antarctica to GMSL rise was four times larger during 2010–2019 than during 1992 –1999 (IPCC AR6_WGI, confidence: high)
Because of the increased ice-sheet mass loss, the total loss of land ice (glaciers and ice sheets) was the largest contributor to global mean sea level rise over the period 2006–2018 (IPCC AR6_WGI, confidence: high)
Temporal variability in ocean dynamics dominates regional patterns on annual to decadal time scales (IPCC AR6_WGI, confidence: high)
Observations show that high-tide flooding events that occurred five times per year during the period 1960–1980 occurred, on average, more than eight times per year during the period 1995–2014 (IPCC AR6_WGI, confidence: high)
Under the assumption that other contributors to extreme sea levels remain constant (e.g., stationary tides, storm-surge, and wave climate), extreme sea levels that occurred once per century in the recent past will occur annually or more frequently at about 19–31% of tide gauges by 2050 and at about 60% (SSP1-2.6) to 82% (SSP5-8.5) of tide gauges by 2100 (IPCC AR6_WGI, confidence: medium)
In total, such extreme sea levels will occur about 20 to 30 times more frequently by 2050 and 160 to 530 times more frequently by 2100 compared to the recent past, as inferred from the median amplification factors for SSP1-2.6, SSP2-4.5, and SSP5-8.5 (IPCC AR6_WGI, confidence: medium)
Over the 21st century, the majority of coastal locations will experience a median projected regional sea level rise within ±20% of the median projected GMSL change (IPCC AR6_WGI, confidence: medium)
By 2300, GMSL will rise between 0.3 m and 3.1 m under SSP1-2.6, between 1.7 m and 6.8 m under SSP5-8.5 in the absence of marine ice cliff instability, and by up to 16 m under SSP5-8.5 considering marine ice cliff instability (IPCC AR6_WGI, confidence: low)
Common regional biases in SST or historical SST trends are not exclusively linked to the representation of the ocean (IPCC AR6_WGI, confidence: high)
In summary, CMIP6 models show persistent regional biases in representing the climatological SST state (IPCC AR6_WGI, confidence: very high)
Warming is projected at varying rates in all regions by 2050, except the North Atlantic Subpolar Region, the equatorial Pacific, and the Southern Ocean where models disagree (IPCC AR6_WGI, confidence: high)
Similarly, the SST change pattern observed in the tropical Pacific Ocean will transition on centennial time scales to a mean pattern resembling the El Niño pattern (IPCC AR6_WGI, confidence: medium)
In summary, globally integrated and large-scale fluxes are more reliably inferred from heat content and salinity change, while regional trends are rarely robust in observations; where they are robust, they tend to be underestimated or in disagreement in models (IPCC AR6_WGI, confidence: very high)
The AR5 (Rhein et al., 2013) assessed with medium confidence that zonal wind stress over the Southern Ocean increased from the early 1980s to the 1990s (IPCC AR6_WGI, confidence: medium)
In summary, there is limited observational evidence that the mixed layer is globally deepening, while models show no emergence of a trend until later in the 21st century under strong emissions.The SROCC assessed that upper-ocean stratification will continue to increase in the 21st century under increased radiative forcing (IPCC AR6_WGI, confidence: high)