rlacombe/ClimateX huggingface dataset:
Over the 21st century and beyond, abrupt human-caused changes to the water cycle cannot be excluded (IPCC AR6_WGI, confidence: medium)
The overall effect of anthropogenic aerosols is to reduce global precipitation through surface radiative cooling effects (IPCC AR6_WGI, confidence: high)
Over much of the 20th century, opposing effects of GHGs and aerosols on precipitation have been observed for some regional monsoons (IPCC AR6_WGI, confidence: high)
Inter-model differences and internal variability contribute to a substantial range in projections of large-scale and regional water cycle changes (IPCC AR6_WGI, confidence: high)
The occurrence of volcanic eruptions can alter the water cycle for several years (IPCC AR6_WGI, confidence: high)
Near-surface specific humidity has increased over the ocean (likely) and land (very likely) since at least the 1970s, with a detectable human influence (IPCC AR6_WGI, confidence: medium)
In response to cryosphere changes (Section TS.2.5), there have been changes in streamflow seasonality, including an earlier occurrence of peak streamflow in high-latitude and mountain catchments (IPCC AR6_WGI, confidence: high)
Projected runoff (Box TS.6, Figure 1c) is typically decreased by contributions from small glaciers because of glacier mass loss, while runoff from larger glaciers will generally increase with increasing global warming levels until their mass becomes depleted (IPCC AR6_WGI, confidence: high)
Greater warming over land than over the ocean alters atmospheric circulation patterns and reduces continental near-surface relative humidity, which contributes to regional drying (IPCC AR6_WGI, confidence: high)
Projected increases in evapotranspiration due to growing atmospheric water demand will decrease soil moisture over the Mediterranean region, south-western North America, South Africa, South-Western South America and south-western Australia (IPCC AR6_WGI, confidence: high)
Some tropical regions are also projected to experience enhanced aridity, including the Amazon basin and Central America (IPCC AR6_WGI, confidence: high)
The total land area subject to increasing drought frequency and severity will expand (high confidence), and 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 (IPCC AR6_WGI, confidence: high)
Large-scale deforestation likely decreases evapotranspiration and precipitation and increases runoff over the deforested regions relative to the regional effects of climate change (IPCC AR6_WGI, confidence: medium)
Urbanization increases local precipitation (medium confidence) and runoff intensity (IPCC AR6_WGI, confidence: high)
Increased precipitation intensities have enhanced groundwater recharge, most notably in tropical regions (IPCC AR6_WGI, confidence: medium)
A warmer climate increases moisture transport into weather systems, which intensifies wet seasons and events (IPCC AR6_WGI, confidence: high)
The magnitudes of projected precipitation increases and related extreme events depend on model resolution and the representation of convective processes (IPCC AR6_WGI, confidence: high)
Increases in near-surface atmospheric moisture capacity of about 7% per 1ºC of warming lead to a similar response in the intensification of heavy precipitation from sub-daily up to seasonal time scales, increasing the severity of flood hazards (IPCC AR6_WGI, confidence: high)
The average and maximum rain-rates associated with tropical and extratropical cyclones, atmospheric rivers and severe convective storms will therefore also increase with future warming (IPCC AR6_WGI, confidence: high)
In the tropics year-round and in the summer season elsewhere, interannual variability of precipitation and runoff over land is projected to increase at a faster rate than changes in seasonal mean precipitation (Figure TS.12e,f) (IPCC AR6_WGI, confidence: medium)
Sub-seasonal precipitation variability is also projected to increase, with fewer rainy days but increased daily mean precipitation intensity over many land regions (IPCC AR6_WGI, confidence: high)
Improved quantifications of ERF, the climate system radiative response, and the observed energy increase in the Earth system for the period 1971–2018 demonstrate improved closure of the global energy budget (i.e., the extent to which the sum of the integrated forcing and the integrated radiative response equals the energy gain of the Earth system) compared to AR5 (IPCC AR6_WGI, confidence: high)
Changes in sulphur dioxide (SO 2) emissions make the dominant contribution to the ERF from aerosol– cloud interactions (IPCC AR6_WGI, confidence: high)
Over the 1750–2019 period, the contributions from the emitted compounds to global surface temperature changes broadly match their contributions to the ERF (IPCC AR6_WGI, confidence: high)
The ERF due to aerosol– cloud interactions (ERFaci) contributes most to the magnitude of the total aerosol ERF (high confidence) and is assessed to be –1.0 [–1.7 to –0.3] W m–2 (medium confidence), with the remainder due to aerosol–radiation interactions (ERFari), assessed to be –0.3 [–0.6 to 0.0] W m–2 (IPCC AR6_WGI, confidence: medium)
Feedback processes are expected to become more positive overall (more amplifying of global surface temperature changes) on multi-decadal time scales as the spatial pattern of surface warming evolves and global surface temperature increases, leading to an ECS that is higher than was inferred in AR5 based on warming over the instrumental record (IPCC AR6_WGI, confidence: high)
Based on process understanding, climate modelling, and paleoclimate reconstructions of past warm periods, it is expected that future warming will become enhanced over the eastern Pacific Ocean (medium confidence) and Southern Ocean (IPCC AR6_WGI, confidence: high)
There is a high level of agreement among the different lines of evidence (Figure TS.16c) (IPCC AR6_WGI, confidence: high)
Because the total biogeophysical and non-CO 2 biogeochemical feedback is assessed to have a central value that is near zero (IPCC AR6_WGI, confidence: low)
The CMIP5 and CMIP6 ranges of cloud feedback are similar to this assessed range, with CMIP6 having a slightly more positive median cloud feedback (IPCC AR6_WGI, confidence: high)
This near-linear relationship further implies that mitigation requirements for limiting warming to specific levels can be quantified in terms of a carbon budget (IPCC AR6_WGI, confidence: high)
Several factors, including estimates of historical warming, future emissions from thawing permafrost, variations in projected non-CO 2 warming, and the global surface temperature change after cessation of CO 2 emissions, affect the exact value of carbon budgets (IPCC AR6_WGI, confidence: high)
In the same way that part of current anthropogenic net CO 2 emissions are taken up by land and ocean carbon stores, net CO 2 removal will be partially counteracted by CO 2 release from these stores (IPCC AR6_WGI, confidence: very high)
Asymmetry in the carbon cycle response to simultaneous CO 2 emissions and removals implies that a larger amount of CO 2 would need to be removed to compensate for an emission of a given magnitude to attain the same change in atmospheric CO 2 (IPCC AR6_WGI, confidence: medium)
CDR methods have wide-ranging side- effects that can either weaken or strengthen the carbon sequestration and cooling potential of these methods and affect the achievement of sustainable development goals (IPCC AR6_WGI, confidence: high)
In the same way part of current anthropogenic net CO 2 emissions are taken up by land and ocean carbon stores, net CO 2 removal will be partially counteracted by CO 2 release from these stores, such that the amount of CO 2 sequestered by CDR will not result in an equivalent drop in atmospheric CO 2 (IPCC AR6_WGI, confidence: very high)
The fraction of CO 2 removed from the atmosphere that is not replaced by CO 2 released from carbon stores – a measure of CDR effectiveness – decreases slightly with increasing amounts of removal (medium confidence) and decreases strongly if CDR is applied at lower atmospheric CO 2 concentrations (IPCC AR6_WGI, confidence: medium)
The reduction in global surface temperature is approximately linearly related to cumulative CO 2 removal (IPCC AR6_WGI, confidence: high)
Because of this near-linear relationship, the amount of cooling per unit CO 2 removed is approximately independent of the rate and amount of removal (IPCC AR6_WGI, confidence: medium)
For instance, sea level rise due to ocean thermal expansion would not reverse for several centuries to millennia (IPCC AR6_WGI, confidence: high)
Biophysical and biogeochemical side-effects of CDR methods are associated with changes in surface albedo, the water cycle, emissions of CH 4 and N 2O, ocean acidification and marine ecosystem productivity (IPCC AR6_WGI, confidence: high)
These side-effects and associated Earth system feedbacks can decrease carbon uptake and/or change local and regional climate and in turn limit the CO 2 sequestration and cooling potential of specific CDR methods (IPCC AR6_WGI, confidence: medium)
Deployment of CDR, particularly on land, can also affect water quality and quantity, food production and biodiversity (IPCC AR6_WGI, confidence: high)
These effects are often highly dependent on local context, management regime, prior land use, and scale (IPCC AR6_WGI, confidence: high)
The largest co-benefits are obtained with methods that seek to restore natural ecosystems or improve soil carbon sequestration (IPCC AR6_WGI, confidence: medium)
The climate and biogeochemical effects of terminating CDR are expected to be small for most CDR methods (IPCC AR6_WGI, confidence: medium)
Carbon-cycle responses are more robustly accounted for in emissions metrics compared to AR5 (IPCC AR6_WGI, confidence: high)
The methodology for doing this has been placed on a more robust scientific footing compared to AR5 (IPCC AR6_WGI, confidence: high)
Methane from fossil fuel sources has slightly higher emissions metric values than those from biogenic sources since it leads to additional fossil CO 2 in the atmosphere (IPCC AR6_WGI, confidence: high)
Updates to the chemical adjustments for CH 4 and N2O emissions (Section TS.3.1) and revisions in their lifetimes result in emissions metrics for GWP and GTP that are slightly lower than in AR5 (IPCC AR6_WGI, confidence: medium)
When GHGs are aggregated using standard metrics such as GWP or GTP, cumulative CO 2-e emissions are not necessarily proportional to future global surface temperature outcomes (IPCC AR6_WGI, confidence: high)
The warming evolution resulting from net zero GHG emissions defined in this way corresponds approximately to reaching net zero CO 2 emissions, and would thus not lead to declining temperatures after net zero GHG emissions are achieved but to an approximate temperature stabilization (IPCC AR6_WGI, confidence: high)
The choice of emissions metric hence affects the quantification of net zero GHG emissions, and therefore the resulting temperature outcome of reaching and sustaining net zero GHG emissions levels (IPCC AR6_WGI, confidence: high)
Fossil fuel combustion for energy, industry and land transportation are the largest contributing sectors on a 100-year time scale (IPCC AR6_WGI, confidence: high)
Current emissions of CO 2, N2O and SLCFs from East Asia and North America are the largest regional contributors to additional net future warming on both short (medium confidence) and long time scales (10 and 100 years, respectively) (IPCC AR6_WGI, confidence: high)
However, these reductions were lower than what would be expected from sustained implementation of policies addressing air quality and climate change (IPCC AR6_WGI, confidence: medium)
Consistent with this small net radiative forcing, and against a large component of internal variability, Earth system models show no detectable effect on global or regional surface temperature or precipitation (IPCC AR6_WGI, confidence: high)
This additional warming is stable after 2040 in SSPs associated with lower global air pollution as long as CH 4 emissions are also mitigated, but the overall warming induced by SLCF changes is higher in scenarios in which air quality continues to deteriorate (induced by growing fossil fuel use and limited air pollution control) (IPCC AR6_WGI, confidence: high)
Sustained CH 4 mitigation reduces global surface ozone, contributing to air quality improvements, and also reduces surface temperature in the longer term, but only sustained CO 2 emissions reductions allow long-term climate stabilization (IPCC AR6_WGI, confidence: high)
Future changes in air quality (near-surface ozone and particulate matter, or PM) at global and local scales are predominantly driven by changes in ozone and aerosol precursor emissions rather than climate (IPCC AR6_WGI, confidence: high)
Air quality improvements driven by rapid decarbonization strategies, as in SSP1-1.9 and SSP1-2.6, are not sufficient in the near term to achieve air quality guidelines set by the World Health Organization in some highly polluted regions (IPCC AR6_WGI, confidence: high)
Under the SSP3-7.0 scenario, PM levels are projected to increase until 2050 over large parts of Asia, and surface ozone pollution is projected to worsen over all continental areas through 2100 (IPCC AR6_WGI, confidence: high)
In SSP5-8.5, a scenario without climate change mitigation but with stringent air pollution control, PM levels decline through 2100, but high CH 4 levels hamper the decline in global surface ozone at least until 2080 (IPCC AR6_WGI, confidence: high)
These investigations have consistently shown that SRM could offset some of the effects of increasing greenhouse gases on global and regional climate, including the carbon and water cycles (IPCC AR6_WGI, confidence: high)
However, there would be substantial residual or overcompensating climate change at the regional scales and seasonal time scales (IPCC AR6_WGI, confidence: high)
The cooling caused by SRM would increase the global land and ocean CO 2 sinks (medium confidence), but this would not stop CO 2 from increasing in the atmosphere or affect the resulting ocean acidification under continued anthropogenic emissions (IPCC AR6_WGI, confidence: high)
A sudden and sustained termination of SRM in a high CO 2 emissions scenario would cause rapid climate change (IPCC AR6_WGI, confidence: high)
However, a gradual phase-out of SRM combined with emissions reduction and carbon dioxide removal (CDR) would avoid these termination effects (IPCC AR6_WGI, confidence: medium)
Since AR5, more modelling work has been conducted with more sophisticated treatment of aerosol-based SRM approaches, but the uncertainties in cloud–aerosol–radiation interactions are still large (IPCC AR6_WGI, confidence: high)
Modelling studies suggest that it is possible to stabilize multiple large-scale temperature indicators simultaneously by tailoring the deployment strategy of SRM options (IPCC AR6_WGI, confidence: medium)
In contrast, cirrus cloud thinning, targeting longwave radiation, is expected to cause an increase in global mean precipitation (IPCC AR6_WGI, confidence: medium)
If shortwave approaches are used to offset global mean warming, the magnitude of reduction in regional precipitation minus evapotranspiration (P–E) (Box TS.5), which is more relevant to freshwater availability, is smaller than precipitation decrease because of simultaneous reductions in both precipitation and evapotranspiration (IPCC AR6_WGI, confidence: medium)
If SRM is used to cool the planet, it would cause a reduction in plant and soil respiration and slow the reduction of ocean carbon uptake due to warming (IPCC AR6_WGI, confidence: medium)
The result would be an enhancement of the global land and ocean CO 2 sinks (IPCC AR6_WGI, confidence: medium)
However, SRM would not stop CO 2 from increasing in the atmosphere or affect the resulting ocean acidification under continued anthropogenic emissions (IPCC AR6_WGI, confidence: high)
A sudden and sustained termination of SRM in a high GHG emissions scenario would cause rapid climate change and a reversal of the SRM effects on the carbon sinks (IPCC AR6_WGI, confidence: high)
However, a gradual phase-out of SRM combined with emissions reductions and CDR would avoid larger rates of changes (IPCC AR6_WGI, confidence: medium)
For global climate indicators, evidence for abrupt change is limited, but deep ocean warming, acidification and sea level rise are committed to ongoing change for millennia after global surface temperatures initially stabilize and are irreversible on human time scales (IPCC AR6_WGI, confidence: very high)
At the regional scale, abrupt responses, tipping points and even reversals in the direction of change cannot be excluded (IPCC AR6_WGI, confidence: high)
Some processes suspected of having tipping points, such as the Atlantic Meridional Overturning Circulation (AMOC), have been found to often undergo recovery after temperature stabilization with a time delay (IPCC AR6_WGI, confidence: low)
It is likely that under stabilization of global warming at 1.5°C, 2.0°C or 3.0°C relative to 1850–1900, the AMOC will continue to weaken for several decades by about 15%, 20% and 30% of its strength and then recover to pre-decline values over several centuries (IPCC AR6_WGI, confidence: medium)
At sustained warming levels between 2°C and 3°C, there is limited evidence that the Greenland and West Antarctic ice sheets will be lost almost completely and irreversibly over multiple millennia; both the probability of their complete loss and the rate of mass loss increases with higher surface temperatures (IPCC AR6_WGI, confidence: high)
At sustained warming levels between 3°C and 5°C, near-complete loss of the Greenland Ice Sheet and complete loss of the West Antarctic Ice Sheet is projected to occur irreversibly over multiple millennia (medium confidence); with substantial parts or all of Wilkes Subglacial Basin in East Antarctica lost over multiple millennia (IPCC AR6_WGI, confidence: low)
For other hazards (e.g., ice-sheet behaviour, glacier mass loss and global mean sea level change, coastal floods, coastal erosion, air pollution, and ocean acidification) the time and/or scenario dimensions remain critical, and a simple and robust relationship with global warming level cannot be established (IPCC AR6_WGI, confidence: high)
For global warming up to 2°C above 1850–1900 levels, paleoclimate records do not indicate abrupt changes in the carbon cycle (IPCC AR6_WGI, confidence: low)
Despite the wide range of model responses, uncertainty in atmospheric CO 2 by 2100 is dominated by future anthropogenic emissions rather than uncertainties related to carbon–climate feedbacks (IPCC AR6_WGI, confidence: high)
The increase in global ocean heat content (Section TS.2.4) will likely continue until at least 2300 even for low emissions scenarios, and global mean sea level will continue to rise for centuries to millennia following cessation of emissions (Box TS.4) due to continuing deep ocean heat uptake and mass loss of the Greenland and Antarctic ice sheets (IPCC AR6_WGI, confidence: high)
Possible abrupt changes and tipping points in biogeochemical cycles lead to additional uncertainty in 21st century atmospheric GHG concentrations, but future anthropogenic emissions remain the dominant uncertainty (IPCC AR6_WGI, confidence: high)
A key methodology is distillation – combining lines of evidence and accounting for stakeholder context and values – which helps ensure the information is relevant, useful and trusted for decision-making (see Core Concepts Box) (IPCC AR6_WGI, confidence: high)
Since AR5, climate change information produced for climate services has increased significantly due to scientific and technological advancements and growing user awareness, requirements, and demand (IPCC AR6_WGI, confidence: very high)
Discarding models that fundamentally misrepresent relevant processes improves the credibility of regional climate information generated from these ensembles (IPCC AR6_WGI, confidence: high)
However, multi-model mean and ensemble spread are not a full measure of the range of projection uncertainty and are not sufficient to characterize low-likelihood, high-impact changes (Box TS.3) or situations where different models simulate substantially different or even opposite changes (IPCC AR6_WGI, confidence: high)
Large single-model ensembles are now available and provide a more comprehensive spectrum of possible changes associated with internal variability (IPCC AR6_WGI, confidence: high)
No-till farming, irrigation and crop expansion have similarly attenuated increases in summer hot extremes in some regions, such as central North America (IPCC AR6_WGI, confidence: medium)
In some cases, even the sign of a projected change in regional climate cannot be trusted if relevant regional processes are not represented, for example, for variables such as precipitation and wind speed (IPCC AR6_WGI, confidence: medium)
However, the performance of these techniques depends on that of the driving climate model: in particular, bias adjustment cannot overcome all consequences of unresolved or strongly misrepresented physical processes, such as large-scale circulation biases or local feedbacks (IPCC AR6_WGI, confidence: medium)
Distilling regional climate information from multiple lines of evidence and taking the user context into account increases fitness, usefulness, relevance and trust in that information for use in climate services (Box TS.11) and decision-making (IPCC AR6_WGI, confidence: high)
Since AR5, there has been a significant increase in the range and diversity of climate service activities (IPCC AR6_WGI, confidence: very high)
Since AR5, climate change information produced in climate service contexts has increased significantly due to scientific and technological advancements and growing user awareness, requirements and demand (IPCC AR6_WGI, confidence: very high)
They require different types of user–producer engagement depending on what the service aims to deliver (IPCC AR6_WGI, confidence: high)
Realization of the full potential of climate services is often hindered by limited resources for the co-design and co-production process, including sustained engagement between scientists, service providers and users (IPCC AR6_WGI, confidence: high)
An exception is the Southern Annular Mode (SAM), which has become systematically more positive (high confidence) and is projected to be more positive in all seasons, except for December–January–February (DJF), in high CO 2 emissions scenarios (IPCC AR6_WGI, confidence: high)
The influence of stratospheric ozone forcing on the SAM trend has been reduced since the early 2000s compared to earlier decades, contributing to the weakening of its positive trend as observed over 2000– 2019 (IPCC AR6_WGI, confidence: medium)
Along latitudes, it is more uniform, with strong amplification of the temperature response towards the Arctic (IPCC AR6_WGI, confidence: medium)
The decrease of SO 2 emissions since the 1980s reduces the damping effect of aerosols, leading to a faster increase in surface air temperature that is most pronounced at mid- and high latitudes of the Northern Hemisphere, where the largest emissions reductions have taken place (IPCC AR6_WGI, confidence: medium)
Multi-decadal variation in anthropogenic aerosol emissions are thought to be a major contributor (IPCC AR6_WGI, confidence: medium)
Future urbanization will amplify the projected air temperature under different background climates, with a strong effect on minimum temperatures that could be as large as the global warming signal (IPCC AR6_WGI, confidence: very high)
Irrigation and crop expansion have attenuated increases in summer hot extremes in some regions, such as central North America (IPCC AR6_WGI, confidence: medium)
The influence of stratospheric ozone forcing on the SAM trend has been reduced since the early 2000s compared to earlier decades, contributing to the weakening of its positive trend observed over 2000–2019 (IPCC AR6_WGI, confidence: medium)
This is because of the opposing influence in the near to mid-term from stratospheric ozone recovery and increases in other greenhouse gases on the Southern Hemisphere summertime mid-latitude circulation (IPCC AR6_WGI, confidence: high)