Implications of Extreme Global Warming Scenarios for Water ... · Implications of Extreme Global...

Implications of Extreme Global Warming Scenarios forWater Availability

Jens Heinke, Dieter Gerten and Katja Frieler

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Figure 1. Change in fresh water availability for different levels of increase in global mean temperature (above pre-industrial value).

Abstract: The world’s freshwater system is among themost vulnerable systems towards climatic changes, andchanges therein will have consequences for bothecosystems and human societies. Here we used the LPJmLDynamic Global Vegetation Model for the biosphere andagrosphere to quantify changes in freshwater availabilityunder different degrees of increas in global meantemperature (2K to 8K), globally and spatially explicitly.The model intrinsically couples the terrestrial caron andwater cycle and therefore captures the influence of CO2and vegetation cover changes on water fluxes. LPJmL was

forced for the period up to 2200 by pattern-scaled climatederived from the ensemble median of 24 GeneralCirculation Models. The trajectories of global meantemperature and CO2 concentration were taken from theMAGICC6 Model for the Assessment of Greenhouse-Gas Induced Climate Change. This model capturesthermal inertia of the earth system, carbon cycle feedbacksand radiative forcing of a wide range of greenhouse gasesand aerosols to emulate the response of global meantemperature to emissions of CO2 and other greenhousegases.

Potsdam Institute for Climate Impact researchResearch Domaine II: Climate Impacts and Vulnerabilities

Figure 2: Impact of climate change on per capita fresh water availabilty for four different population scenarios: Today's (year 2000) population, and population in the SRES A2, B1and B2 scenarios in 2100. Left: Per capita fresh water availability assuming contemporary (19971 - 2000) water availability..Middle: Global population numbers and number ofpeople living in different availability classes assuming contemporary water availability. Right: Fraction of people in each availabilty class affected by certain level of change in freshwater resource for different degrees of global warming. Colours and impact classes are the same as in figure 1.

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Population in 2000:Total population : 5624 Mio< 500 m³ : 1005 Mio (18%)500 - 1000 m³ : 1392 Mio (25%)1000 - 1700 m³ : 1246 Mio (22%)>1700 m³ : 1981 Mio (35%)

Population in 2100 of SRES A2:Total population : 11681 Mio< 500 m³ : 4445 Mio (38%)500 - 1000 m³ : 3591 Mio (31%)1000 - 1700 m³ : 1328 Mio (11%)>1700 m³ : 2317 Mio (20%)

Population in 2100 of SRES B1:Total population : 6611 Mio< 500 m³ : 1693 Mio (26%)500 - 1000 m³ : 985 Mio (15%)1000 - 1700 m³ : 1440 Mio (22%)>1700 m³ : 2493 Mio (37%)

Population in 2100 of SRES B2:Total population : 9819 Mio< 500 m³ : 3303 Mio (34%)500 - 1000 m³ : 3197 Mio (33%)1000 - 1700 m³ : 1163 Mio (12%)>1700 m³ : 2156 Mio (22%)