1Max Planck Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany
2Centre for Ecology and Hydrology, Wallingford, UK
3School of Geography, University of Nottingham, Nottingham, UK
4Norwegian Water Resources and Energy Directorate, Oslo, Norway
5National Institute for Environmental Studies, Tsukuba, Japan
6Potsdam Institute for Climate Impact Research, Potsdam, Germany
7Wageningen University and Research Centre, Wageningen, the Netherlands
8Center for Environmental Systems Research, University of Kassel, Kassel, Germany
9Met Office Hadley Centre, Exeter, UK
Received: 12 Nov 2012 – Discussion started: 04 Dec 2012
Abstract. Climate change is expected to alter the hydrological cycle resulting in large-scale impacts on water availability. However, future climate change impact assessments are highly uncertain. For the first time, multiple global climate (three) and hydrological models (eight) were used to systematically assess the hydrological response to climate change and project the future state of global water resources. This multi-model ensemble allows us to investigate how the hydrology models contribute to the uncertainty in projected hydrological changes compared to the climate models. Due to their systematic biases, GCM outputs cannot be used directly in hydrological impact studies, so a statistical bias correction has been applied. The results show a large spread in projected changes in water resources within the climate–hydrology modelling chain for some regions. They clearly demonstrate that climate models are not the only source of uncertainty for hydrological change, and that the spread resulting from the choice of the hydrology model is larger than the spread originating from the climate models over many areas. But there are also areas showing a robust change signal, such as at high latitudes and in some midlatitude regions, where the models agree on the sign of projected hydrological changes, indicative of higher confidence in this ensemble mean signal. In many catchments an increase of available water resources is expected but there are some severe decreases in Central and Southern Europe, the Middle East, the Mississippi River basin, southern Africa, southern China and south-eastern Australia.
Revised: 28 Mar 2013 – Accepted: 05 Apr 2013 – Published: 07 May 2013
Hagemann, S., Chen, C., Clark, D. B., Folwell, S., Gosling, S. N., Haddeland, I., Hanasaki, N., Heinke, J., Ludwig, F., Voss, F., and Wiltshire, A. J.: Climate change impact on available water resources obtained using multiple global climate and hydrology models, Earth Syst. Dynam., 4, 129-144, doi:10.5194/esd-4-129-2013, 2013.