title: Multimodel assessment of water scarcity under climate change.
abstract: Water scarcity severely impairs food security and economic prosperity in many countries today. Expected future population changes will, in many countries as well as globally, increase the pressure on available water resources. On the supply side, renewable water resources will be affected by projected changes in precipitation patterns, temperature, and other climate variables. Here we use a large ensemble of global hydrological models (GHMs) forced by five global climate models and the latest greenhouse-gas concentration scenarios (Representative Concentration Pathways) to synthesize the current knowledge about climate change impacts on water resources. We show that climate change is likely to exacerbate regional and global water scarcity considerably. In particular, the ensemble average projects that a global warming of 2 °C above present (approximately 2.7 °C above preindustrial) will confront an additional approximate 15% of the global population with a severe decrease in water resources and will increase the number of people living under absolute water scarcity (<500 m(3) per capita per year) by another 40% (according to some models, more than 100%) compared with the effect of population growth alone. For some indicators of moderate impacts, the steepest increase is seen between the present day and 2 °C, whereas indicators of very severe impacts increase unabated beyond 2 °C. At the same time, the study highlights large uncertainties associated with these estimates, with both global climate models and GHMs contributing to the spread. GHM uncertainty is particularly dominant in many regions affected by declining water resources, suggesting a high potential for improved water resource projections through hydrological model development.
authors.affiliation: Potsdam Institute for Climate Impact Research, 14412 Potsdam, Germany.
authors.forename: Jacob
authors.initials: J
authors.lastname: Schewe
authors.forename: Jens
authors.initials: J
authors.lastname: Heinke
authors.forename: Dieter
authors.initials: D
authors.lastname: Gerten
authors.forename: Ingjerd
authors.initials: I
authors.lastname: Haddeland
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Arnell
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Clark
authors.forename: Rutger
authors.initials: R
authors.lastname: Dankers
authors.forename: Stephanie
authors.initials: S
authors.lastname: Eisner
authors.forename: Balázs M
authors.initials: BM
authors.lastname: Fekete
authors.forename: Felipe J
authors.initials: FJ
authors.lastname: Colón-González
authors.forename: Simon N
authors.initials: SN
authors.lastname: Gosling
authors.forename: Hyungjun
authors.initials: H
authors.lastname: Kim
authors.forename: Xingcai
authors.initials: X
authors.lastname: Liu
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Masaki
authors.forename: Felix T
authors.initials: FT
authors.lastname: Portmann
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Satoh
authors.forename: Tobias
authors.initials: T
authors.lastname: Stacke
authors.forename: Qiuhong
authors.initials: Q
authors.lastname: Tang
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Wada
authors.forename: Dominik
authors.initials: D
authors.lastname: Wisser
authors.forename: Torsten
authors.initials: T
authors.lastname: Albrecht
authors.forename: Katja
authors.initials: K
authors.lastname: Frieler
authors.forename: Franziska
authors.initials: F
authors.lastname: Piontek
authors.forename: Lila
authors.initials: L
authors.lastname: Warszawski
authors.forename: Pavel
authors.initials: P
authors.lastname: Kabat
mesh_terms: D057231:Climate Change; D055864:Droughts / Q000706:statistics & numerical data*; D005544:Forecasting; D008962:Models, Theoretical; D011158:Population Growth; D013696:Temperature; D014881:Water Supply / Q000706:statistics & numerical data*
keywords: Inter-Sectoral Impact Model Intercomparison Project; climate impacts; hydrological modeling