Editing IPCC:AR6/WGII/SPM (section)

=== Mid to Long-term Risks (2041–2100) ===

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'''B.4 Beyond 2040 and depending on the level of global warming, climate change will lead to numerous risks to natural and human systems ( '''''high confidence''''' ). For 127 identified key risks, assessed mid- and long-term impacts are up to multiple times higher than currently observed ( '''''high confidence''''' ). The magnitude and rate of climate change and associated risks depend strongly on near-term mitigation and adaptation actions, and projected adverse impacts and related losses and damages escalate with every increment of global warming ( '''''very high confidence''''' ).   Expand [[#figure-spm-3|Figure SPM.3]] Links to chapters 2.5, 3.4, 4.4, 5.2, 6.2, 7.3, 8.4, 9.2, 10.2, 11.6, 12.4, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 14.6, 15.3, 16.5, 16.6, CCP2.2, CCP3.3, CCP4.3, CCP5.3, CCP6.4, CCP7.3'''
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'''B.4.1''' Biodiversity loss and degradation, damages to and transformation of ecosystems are already key risks for every region due to past global warming and will continue to escalate with every increment of global warming ( ''very high confidence'' ). In terrestrial ecosystems, 3 to 14% of species assessed [[#footnote-017|33]] will ''likely'' face very high risk of extinction [[#footnote-016|34]] at global warming levels of 1.5°C, increasing up to 3 to 18% at 2°C, 3 to 29% at 3°C, 3 to 39% at 4°C, and 3 to 48% at 5°C. In ocean and coastal ecosystems, risk of biodiversity loss ranges between moderate and very high by 1.5°C global warming level and is moderate to very high by 2°C but with more ecosystems at high and very high risk ( ''high confidence'' ), and increases to high to very high across most ocean and coastal ecosystems by 3°C ( ''medium'' to ''high confidence'' , depending on ecosystem). Very high extinction risk for endemic species in biodiversity hotspots is projected to at least double from 2% between 1.5°C and 2°C global warming levels and to increase at least tenfold if warming rises from 1.5°C to 3°C ( ''medium confidence'' ). (Figure SPM.3c, d, f) { 2.4, 2.5, 3.4, 3.5, 12.3, 12.5, Table 12.6, 13.4, 13.10, 16.4, 16.6, [https://www.ipcc.ch/chapter/spm#CCP1.2 CCP1.2] , Figure CCP1.6, Figure CCP1.7, [https://www.ipcc.ch/chapter/spm#CCP5.3 CCP5.3] , [https://www.ipcc.ch/chapter/spm#CCP6.3 CCP6.3] , CCB PALEO }

'''B.4.2''' Risks in physical water availability and water-related hazards will continue to increase by the mid- to long-term in all assessed regions, with greater risk at higher global warming levels ( ''high confidence'' ). At approximately 2°C global warming, snowmelt water availability for irrigation is projected to decline in some snowmelt dependent river basins by up to 20%, and global glacier mass loss of 18 ± 13% is projected to diminish water availability for agriculture, hydropower, and human settlements in the mid- to long-term, with these changes projected to double with 4°C global warming ( ''medium confidence'' ). In Small Islands, groundwater availability is threatened by climate change ( ''high confidence'' ). Changes to streamflow magnitude, timing and associated extremes are projected to adversely impact freshwater ecosystems in many watersheds by the mid- to long-term across all assessed scenarios ( ''medium confidence'' ). Projected increases in direct flood damages are higher by 1.4 to 2 times at 2°C and 2.5 to 3.9 times at 3°C compared to 1.5°C global warming without adaptation ( ''medium confidence'' ). At global warming of 4°C, approximately 10% of the global land area is projected to face increases in both extreme high and low river flows in the same location, with implications for planning for all water use sectors ( ''medium confidence'' ). Challenges for water management will be exacerbated in the near, mid and long term, depending on the magnitude, rate and regional details of future climate change and will be particularly challenging for regions with constrained resources for water management ( ''high confidence'' ). { 2.3, 4.4, 4.5, Box 4.2, Figure 4.20, 15.3, [https://www.ipcc.ch/chapter/spm#CCP5.3 CCP5.3] , CCB DISASTER, SROCC 2.3 }

'''B.4.3''' Climate change will increasingly put pressure on food production and access, especially in vulnerable regions, undermining food security and nutrition ( ''high confidence'' ). Increases in frequency, intensity and severity of droughts, floods and heatwaves, and continued sea level rise will increase risks to food security ( ''high confidence'' ) in vulnerable regions from moderate to high between 1.5°C and 2°C global warming level, with no or low levels of adaptation ( ''medium confidence'' ). At 2°C or higher global warming level in the mid-term, food security risks due to climate change will be more severe, leading to malnutrition and micro-nutrient deficiencies, concentrated in Sub-Saharan Africa, South Asia, Central and South America and Small Islands ( ''high confidence).'' Global warming will progressively weaken soil health and ecosystem services such as pollination, increase pressure from pests and diseases, and reduce marine animal biomass, undermining food productivity in many regions on land and in the ocean ( ''medium confidence'' ). At 3°C or higher global warming level in the long term, areas exposed to climate-related hazards will expand substantially compared with 2°C or lower global warming level ( ''high confidence'' ), exacerbating regional disparity in food security risks ( ''high confidence'' ). (Figure SPM.3) { 1.1, 3.3, 4.5, 5.2, 5.4, 5.5, 5.8, 5.9, 5.12, 7.3, 8.3, 9.11, 13.5, 15.3, 16.5, 16.6, CCB MOVING PLATE, CCB SLR }

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[[File:508f10da72747d8cd70350ceb58158e0 IPCC_AR6_WGII_Figure_SPM_003a.png]]

'''Figure SPM.3 |''' '''Synthetic diagrams of global and sectoral''' '''assessments and examples of regional key risks.''' Diagrams show the change in the levels of impacts and risks assessed for global warming of 0–5°C global surface temperature change relative to pre-industrial period (1850–1900) over the range.

'''(a)''' Global surface temperature changes in °C relative to 1850–1900. These changes were obtained by combining CMIP6 model simulations with observational constraints based on past simulated warming, as well as an updated assessment of equilibrium climate sensitivity (Box SPM.1). Changes relative to 1850–1900 based on 20-year averaging periods are calculated by adding 0.85°C (the observed global surface temperature increase from 1850–1900 to 1995–2014) to simulated changes relative to 1995–2014. ''Very likely'' ranges are shown for SSP1-2.6 and SSP3-7.0 (WGI AR6 Figure SPM.8). Assessments were carried out at the global scale for (b), (c), (d) and (e).

'''(b)''' The Reasons for Concern (RFC) framework communicates scientific understanding about accrual of risk for five broad categories. Diagrams are shown for each RFC, assuming low to no adaptation (i.e., adaptation is fragmented, localized and comprises incremental adjustments to existing practices). However, the transition to a very high risk level has an emphasis on irreversibility and adaptation limits. Undetectable risk level (white) indicates no associated impacts are detectable and attributable to climate change; moderate risk (yellow) indicates associated impacts are both detectable and attributable to climate change with at least ''medium confidence'' , also accounting for the other specific criteria for key risks; high risk (red) indicates severe and widespread impacts that are judged to be high on one or more criteria for assessing key risks; and very high risk level (purple) indicates very high risk of severe impacts and the presence of significant irreversibility or the persistence of climate-related hazards, combined with limited ability to adapt due to the nature of the hazard or impacts/risks. The horizontal line denotes the present global warming of 1.09°C which is used to separate the observed, past impacts below the line from the future projected risks above it. RFC1: Unique and threatened systems: ecological and human systems that have restricted geographic ranges constrained by climate-related conditions and have high endemism or other distinctive properties. Examples include coral reefs, the Arctic and its Indigenous Peoples, mountain glaciers and biodiversity hotspots. RFC2: Extreme weather events: risks/impacts to human health, livelihoods, assets and ecosystems from extreme weather events such as heatwaves, heavy rain, drought and associated wildfires, and coastal flooding. RFC3: Distribution of impacts: risks/impacts that disproportionately affect particular groups due to uneven distribution of physical climate change hazards, exposure or vulnerability. RFC4: Global aggregate impacts: impacts to socio-ecological systems that can be aggregated globally into a single metric, such as monetary damages, lives affected, species lost or ecosystem degradation at a global scale. RFC5: Large-scale singular events: relatively large, abrupt and sometimes irreversible changes in systems caused by global warming, such as ice sheet disintegration or thermohaline circulation slowing. Assessment methods are described in SM16.6 and are identical to AR5, but are enhanced by a structured approach to improve robustness and facilitate comparison between AR5 and AR6.

Risks for '''(c)''' terrestrial and freshwater ecosystems and '''(d)''' ocean ecosystems. For c) and d), diagrams shown for each risk assume low to no adaptation. The transition to a very high risk level has an emphasis on irreversibility and adaptation limits.

'''(e)''' Climate-sensitive human health outcomes under three scenarios of adaptation effectiveness. The assessed projections were based on a range of scenarios, including SRES, CMIP5, and ISIMIP, and, in some cases, demographic trends. The diagrams are truncated at the nearest whole ºC within the range of temperature change in 2100 under three SSP scenarios in panel (a).

'''(f)''' Examples of regional key risks. Risks identified are of at least ''medium confidence'' level. Key risks are identified based on the magnitude of adverse consequences (pervasiveness of the consequences, degree of change, irreversibility of consequences, potential for impact thresholds or tipping points, potential for cascading effects beyond system boundaries); likelihood of adverse consequences; temporal characteristics of the risk; and ability to respond to the risk, e.g., by adaptation. The full set of 127 assessed global and regional key risks is given in SM16.7. Diagrams are provided for some risks. The development of synthetic diagrams for Small Islands, Asia and Central and South America were limited by the availability of adequately downscaled climate projections, with uncertainty in the direction of change, the diversity of climatologies and socioeconomic contexts across countries within a region, and the resulting low number of impact and risk projections for different warming levels. Absence of risks diagrams does not imply absence of risks within a region. (Box SPM.1) { Figure TS.4, Figure 2.11, Figure SM3.1, Figure 7.9, Figure 9.6, Figure 11.6, Figure 13.28, 16.5, 16.6, Figure 16.15, SM16.3, SM16.4, SM16.5, SM16.6 (methodologies), SM16.7, Figure CCP4.8, Figure [https://www.ipcc.ch/chapter/spm#CCP4.1 CCP4.1] 0, Figure [https://www.ipcc.ch/chapter/spm#CCP6.5 CCP6.5] , WGI AR6 2, WGI AR6 SPM A.1.2, WGI AR6 Figure SPM.8 }

'''B.4.4''' Climate change and related extreme events will significantly increase ill health and premature deaths from the near- to long-term ( ''high confidence'' ). Globally, population exposure to heatwaves will continue to increase with additional warming, with strong geographical differences in heat-related mortality without additional adaptation ( ''very high confidence'' ) ''.'' Climate-sensitive food-borne, water-borne, and vector-borne disease risks are projected to increase under all levels of warming without additional adaptation ( ''high confidence'' ). In particular, dengue risk will increase with longer seasons and a wider geographic distribution in Asia, Europe, Central and South America and sub-Saharan Africa, potentially putting additional billions of people at risk by the end of the century ( ''high confidence'' ) ''.'' Mental health challenges, including anxiety and stress, are expected to increase under further global warming in all assessed regions, particularly for children, adolescents, elderly, and those with underlying health conditions ( ''very high confidence'' ). { 4.5, 5.12, Box 5.10, 7.3, Figure 7.9, 8.4, 9.10, Figure 9.32, Figure 9.35, 10.4, Figure 10.11, 11.3, 12.3, Figure 12.5, Figure 12.6, 13.7, Figure 13.23, Figure 13.24, 14.5, 15.3, [https://www.ipcc.ch/chapter/spm#CCP6.2 CCP6.2] }

'''B.4.5''' Climate change risks to cities, settlements and key infrastructure will rise rapidly in the mid- and long-term with further global warming, especially in places already exposed to high temperatures, along coastlines, or with high vulnerabilities ( ''high confidence'' ). Globally, population change in low-lying cities and settlements will lead to approximately a billion people projected to be at risk from coastal-specific climate hazards in the mid-term under all scenarios, including in Small Islands ( ''high confidence'' ). The population potentially exposed to a 100-year coastal flood is projected to increase by about 20% if global mean sea level rises by 0.15 m relative to 2020 levels; this exposed population doubles at a 0.75 m rise in mean sea level and triples at 1.4 m without population change and additional adaptation ( ''medium confidence'' ). Sea level rise poses an existential threat for some Small Islands and some low-lying coasts ( ''medium confidence'' ). By 2100 the value of global assets within the future 1-in-100 year coastal floodplains is projected to be between US$7.9 and US$12.7 trillion (2011 value) under RCP4.5, rising to between US$8.8 and US$14.2 trillion under RCP8.5 ( ''medium confidence'' ). Costs for maintenance and reconstruction of urban infrastructure, including building, transportation, and energy will increase with global warming level ( ''medium confidence'' ), the associated functional disruptions are projected to be substantial particularly for cities, settlements and infrastructure located on permafrost in cold regions and on coasts ( ''high confidence'' ). { 6.2, 9.9, 10.4, 13.6, 13.10, 15.3, 16.5, [https://www.ipcc.ch/chapter/spm#CCP2.1 CCP2.1] , [https://www.ipcc.ch/chapter/spm#CCP2.2 CCP2.2] , [https://www.ipcc.ch/chapter/spm#CCP5.3 CCP5.3] , [https://www.ipcc.ch/chapter/spm#CCP6.2 CCP6.2] , CCB SLR, SROCC 2.3, SROCC CCB9 }

'''B.4.6''' Projected estimates of global aggregate net economic damages generally increase non-linearly with global warming levels ( ''high confidence'' ). [[#footnote-015|35]] The wide range of global estimates, and the lack of comparability between methodologies, does not allow for identification of a robust range of estimates ( ''high confidence'' ). The existence of higher estimates than assessed in AR5 indicates that global aggregate economic impacts could be higher than previous estimates ( ''low confidence'' ). [[#footnote-014|36]] Significant regional variation in aggregate economic damages from climate change is projected ( ''high confidence'' ) with estimated economic damages per capita for developing countries often higher as a fraction of income ( ''high confidence'' ). Economic damages, including both those represented and those not represented in economic markets, are projected to be lower at 1.5°C than at 3°C or higher global warming levels ( ''high confidence'' ). { 4.4, 9.11, 11.5, 13.10, Box 14.6, 16.5, CWGB ECONOMIC }

'''B.4.7''' In the mid- to long-term, displacement will increase with intensification of heavy precipitation and associated flooding, tropical cyclones, drought and, increasingly, sea level rise ( ''high confidence'' ). At progressive levels of warming, involuntary migration from regions with high exposure and low adaptive capacity would occur ( ''medium confidence'' ). Compared to other socioeconomic factors the influence of climate on conflict is assessed as relatively weak ( ''high confidence'' ). Along long-term socioeconomic pathways that reduce non-climatic drivers, risk of violent conflict would decline ( ''medium confidence'' ). At higher global warming levels, impacts of weather and climate extremes, particularly drought, by increasing vulnerability will increasingly affect violent intrastate conflict ( ''medium confidence'' ). { TS B.7.4, 7.3, 16.5, CCB MIGRATE }

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