摘要：Population growth will in many regions increase the pressure on water resources andlikely increase the number of people affected by water scarcity. In parallel, globalwarming causes hydrological changes which will affect freshwater supply for human use inmany regions. This study estimates the exposure of future population to severehydrological changes relevant from a freshwater resource perspective at different levelsof global mean temperature rise above pre-industrial level (ΔTglob).The analysis is complemented by an assessment of water scarcity that would occur withoutadditional climate change due to population change alone; this is done to identify thepopulation groups that are faced with particularly high adaptation challenges. Theresults are analysed in the context of success and failure of implementing the ParisAgreement to evaluate how climate mitigation can reduce the future number of peopleexposed to severe hydrological change. The results show that without climate mitigationefforts, in the year 2100 about 4.9 billion people in the SSP2 population scenario wouldmore likely than not be exposed to severe hydrological change, and about2.1 billion of them would be faced with particularly high adaptation challenges due toalready prevailing water scarcity. Limiting warming to 2∘C by a successfulimplementation of the Paris Agreement would strongly reduce these numbers to 615 millionand 290 million, respectively. At the regional scale, substantial water-related risksremain at 2∘C, with more than 12% of the population exposed to severehydrological change and high adaptation challenges in Latin America and the Middle Eastand north Africa region. Constraining ΔTglob to 1.5∘C wouldlimit this share to about 5% in these regions.
