Editing IPCC:AR6/WGII/TS (section)

=== Water systems and water security ===

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'''TS.C.4 Water-related risks are projected to increase at all warming levels, with risks being proportionally lower at 1.5°C than at higher degrees of warming (''' '''''high confidence''''' ''')''' '''''.''''' '''Regions and populations with higher exposure and vulnerability are projected to face greater risks than others (''' '''''medium confidence''''' ''')''' '''''.''''' '''Projected changes in the water cycle, water quality, cryosphere changes, drought and flood will negatively impact natural and human systems (''' '''''high confidence''''' ''').''' { 2.5.1, 2.5.2, 2.5.3, 2.5.4, 2.6.3, 3.5.5, 4.4.1, 4.4.2, 4.4.3, 4.4.4, 4.4.5, 4.4.6, 4.5.1, 4.5.2, 4.5.3, 4.5.4, 4.5.5, 4.5.6, 4.5.8, 4.6.1, Box 4.1, Box 4.3, 5.4.3, 5.5.2, 5.8.1, 5.8.2, 5.8.3, 5.9.1, 5.9.3, 5.11.1, 5.11.3, 5.12.3, 5.13, 6.1, 6.2, 6.3, 6.4, 7.3.1, 8.3, 8.4.4, 9.5.8, 9.5.3, 9.5.4, 9.5.5, 9.5.6, 9.5.7, 9.7.1, 9.7.2, 10.4.6, 10.4.7, Box 10.2, Box 10.5, 11.2.2, 11.3.3, 11.3.4, Box 11.3, Box 11.4, 12.3, 13.2.1, 13.2.2, 13.6.2, 13.10.2, 13.10.3, Box 13.1, 14.5.3, 14.5.5, 14.5.9, 16.5.2, 16.6.1, [https://www.ipcc.ch/chapter/ts#CCP1.2.1 CCP1.2.1] , [https://www.ipcc.ch/chapter/ts#CCP1.2.3.2 CCP1.2.3.2] , [https://www.ipcc.ch/chapter/ts#CCP2.2 CCP2.2] , [https://www.ipcc.ch/chapter/ts#CCP4.2 CCP4.2] , [https://www.ipcc.ch/chapter/ts#CCP4.3 CCP4.3] , [https://www.ipcc.ch/chapter/ts#CCP5.3.2 CCP5.3.2] }

'''TS.C.4.1 Water-related risks are projected to increase with every increment in warming level, and the impacts will be felt disproportionately by vulnerable people in regions with high exposure and vulnerability (''' '''''high confidence''''' ''').''' About 800 million to 3 billion people at 2°C and about 4 billion at 4°C warming are projected to experience different levels of water scarcity ( ''medium confidence'' ), leading to increased water insecurity. At 4°C global warming by the end of the century, approximately 10% of the global land area is projected to face simultaneously increasing high extreme streamflow and decreasing low extreme streamflow, affecting over 2.1 billion people ( ''medium confidence'' ) ''.'' Globally, the greatest risks to attaining global sustainability goals come from risks to water security ( ''high confidence'' ). { 4.4.1, 4.4.3, 4.4.5, 4.5.4, 4.6.1, Box 4.2, 5.8.3, 5.9.3, 5.13, 8.3, 8.4.4., 9.7.2, 12.3, Table 12.3, 13.2.1, 13.2.2, 13.6.1, 13.10.2, 15.3.3, 16.6.1, CCB SLR }

'''TS.C.4.2 Projected cryosphere changes will negatively impact water security and livelihoods, with higher severity of risks at higher levels of global warming (''' '''''high confidence''''' ''').''' Glacier mass loss, permafrost thaw and decline in snow cover are projected to continue beyond the 21st century ( ''high confidence'' ). Many low-elevation and small glaciers around the world will lose most of their total mass at 1.5°C warming ( ''high confidence'' ). Glaciers are likely to disappear by nearly 50% in High Mountain Asia and about 70% in Central and Western Asia by the end of the 21st century under the medium warming scenario. Glacier lake outburst flood will threaten the security of local and downstream communities in High Mountain Asia ( ''high confidence'' ). By 2100, annual runoff in one-third of the 56 large-scale glacierised catchments are projected to decline by over 10%, with the most significant reductions in Central Asia and the Andes ( ''medium confidence'' ). Cryosphere related changes in floods, landslides and water availability have the potential to lead to severe consequences for people, infrastructure and the economy in most mountain regions ( ''high confidence'' ). { 4.4.2, 4.4.3, 4.5.8, 9.5.8, 10.4.4, Box 10.5, 11.2.2, Box 11.6, 14.2, 16.5.2, [https://www.ipcc.ch/chapter/ts#CCP1.2.3 CCP1.2.3] , [https://www.ipcc.ch/chapter/ts#CCP5.3.1 CCP5.3.1] , [https://www.ipcc.ch/chapter/ts#CCP5.3.2 CCP5.3.2] , SROCC }

'''TS.C.4.3 Projected changes in the water cycle will impact various ecosystem services (''' '''''medium confidence''''' ''').''' By 2050, environmentally critical streamflow is projected to be affected in 42% to 79% of the world’s watersheds, causing negative impacts on freshwater ecosystems ( ''medium confidence'' ). Increased wildfire, combined with soil erosion due to deforestation, could degrade water supplies ( ''medium confidence'' ) ''.'' Projected climate-driven water cycle changes, including increases in evapotranspiration, altered spatial patterns and amount of precipitation, and associated changes in groundwater recharge, runoff and streamflow, will impact terrestrial, freshwater, estuarine and coastal ecosystems and the transport of materials through the biogeochemical cycles, impacting humans and societal well-being ( ''medium confidence'' ). In Africa, 55–68% of commercially harvested inland fish species are vulnerable to extinction under 2.5°C global warming by 2071–2100. In Central and South America, disruption in water flows will significantly degrade ecosystems such as high-elevation wetlands ( ''high confidence'' ). { 2.5.1, 2.5.2, 2.5.3, 2.5.4, 2.6.3, 3.5.5, 3.5.5, 4.4.1, 4.4.3, 4.4.5 '','' 4.4.6, 4.5.4, 5.4.3, 9.8.5, 11.3.1, 12.3, 14.2.2, 14.5.3, 15.3.3, [https://www.ipcc.ch/chapter/ts#CCP1.2.1 CCP1.2.1] }

'''TS.C.4.4''' '''Drought risks and related societal damage are projected to increase with every degree of warming (''' '''''medium confidence''''' ''').''' Under RCP6.0 and SSP2, the population that is projected to be exposed to extreme to exceptional low total water storage will reach up to 7% over the 21st century ( ''medium confidence'' ) ''.'' Under RCP8.5, aridity zones could expand by one-quarter of the 1990 area by 2100. In southern Europe, more than a third of the population will be exposed to water scarcity at 2°C, and the risk doubles at 3°C, with significant economic losses ( ''medium confidence'' ). Over large areas of northern South America, the Mediterranean, western China and high latitudes in North America and Eurasia, the frequency of extreme agricultural droughts is projected to be 150% to 200% more likely at 2°C and over 200% more likely at 4°C ( ''medium confidence'' ). Above 2°C, the frequency and duration of meteorological drought are projected to double over North Africa, the western Sahel and southern Africa ( ''medium confidence'' ). More droughts and extreme fire weather are projected in southern and eastern Australia ( ''high confidence'' ) and over most of New Zealand ( ''medium confidence'' ). { 4.5.1, 4.6.1, Box 4.1, 4.4.1, 4.4.1.1, 4.4.4, 4.4.5, 4.5.1, 4.5.4, 4.5.5, 4.6.1, 6.2.2, 6.2.3, 7.3.1, 9.5.2, 9.5.3, 9.5.6, 9.9.4, 10.4.6; 11.2.2, Box 11.6, 14.5.3, 14.5.5, [https://www.ipcc.ch/chapter/ts#CCP3.3.1 CCP3.3.1] , [https://www.ipcc.ch/chapter/ts#CCP3.3.2 CCP3.3.2] , CWGB URBAN }

'''TS.C.4.5 Flood risks and societal damages are projected to increase with every increment of global warming (''' '''''medium confidence''''' ''').''' The projected increase in precipitation intensity ( ''high confidence'' ) will increase rain-generated local flooding ( ''medium confidence'' ). Direct flood damage is projected to increase by four to five times at 4°C compared to 1.5°C ( ''medium confidence'' ) ''.'' A higher sea level with storm surge further inland may create more severe coastal flooding ( ''high confidence'' ). Projected intensifications of the hydrological cycle pose increasing risks, including potential doubling of flood risk and 1.2- to 1.8-fold increase in GDP loss due to flooding between 1.5°C and 3°C ( ''medium confidence'' ). Projected increase in heavy rainfall events at all levels of warming in many regions in Africa will cause increasing exposure to pluvial and riverine flooding ( ''high confidence'' ), with expected human displacement increasing 200% for 1.6°C and 600% for 2.6°C. A 1.5°C increase would result in an increase of 100–200% in the population affected by floods in Colombia, Brazil and Argentina, 300% in Ecuador and 400% in Peru ( ''medium confidence'' ). In Europe, above 3°C global warming level, the costs of damage and people affected by precipitation and river flooding may double. { 4.4.1, 4.4.4, 4.5.4, 4.5.5, 6.2.2, 7.3.1, Box 4.1, Box 4.3, 9.5.3, 9.5.4, 9.5.5, 9.5.6, 9.5.7, 9.7.2, 9.9.4, 10.4.6, Box 10.2, Box 11.4, 12.3, 13.2.1, 13.2.2, 13.6.2, 13.10.2, Box 13.1, 14.2.2, 14.5.3, [https://www.ipcc.ch/chapter/ts#CCP2.2 CCP2.2] , CWGB URBAN }

'''TS.C.4.6 Projected water cycle changes will impact agriculture, energy production and urban water uses (''' '''''medium confidence''''' ''').''' Agricultural water use will increase globally as a consequence of population increase and dietary changes, as well as increased water requirements due to climate change ( ''high confidence'' ). Groundwater recharge in some semiarid regions are projected to increase, but worldwide depletion of non-renewable groundwater storage will continue due to increased groundwater demand ( ''medium'' to ''high confidence'' ). Increased floods and droughts, together with heat stress, will have an adverse impact on food availability and prices, resulting in increased undernourishment in South and Southeast Asia ( ''high confidence'' ). In the Mediterranean and parts of Europe, potential reductions of hydropower of up to 40% are projected under 3°C warming, while declines below 10% and 5% are projected under 2°C and 1.5°C warming levels respectively. An additional 350 and 410 million people living in urban areas will be exposed to water scarcity from severe droughts at 1.5°C and 2°C respectively. { 2.5.3, 4.4.1, 4.4.2, 4.5.6, 4.6.1, 5.4.3, 6.2.2, 6.2.4, Box 6.2, 6.3.5, 6.4, 9.7.2, 10.4.7, 12.3, 13.10.3, 4.5.2, 4.6.1, 11.3.3, 11.3.4, Box 11.3, 12.3, 14.5.3, 14.5.5, [https://www.ipcc.ch/chapter/ts#CCP4.2 CCP4.2] , [https://www.ipcc.ch/chapter/ts#CCP4.3 CCP4.3] , CWGB URBAN }

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