1Predicting Global Warming Impacts on Regional Water Availability

As climate warms during the 21st century, resultant changes in water availability are an extremely important issue for society, perhaps even more important than the magnitude of warming itself. In this paper, we use the results from different climate model simulations to calculate changes in regional water availability. We examine the possibilities and problems associated with these calculations, focused on seven regions and a subset of five Atmosphere-Ocean General Circulation Models (AOGCMs) whose results were used in the 2007 IPCC report. We use two different measures of water availability changes: the modeled soil moisture and a drought index. Our results show that in some regions (Southwestern United States, Southern Europe), the models and drought measures agree on a prospective drying, while in other areas (Uruguay, Colombia, Australia) the drought index indicates drying in all three locations but there is little soil moisture change. In Eastern China, in contrast to current tendencies of flooding in the southeast and drought in the northeast, both measures show the opposite tendencies in the late 21st century. In Eastern Siberia, the drought index shows wetter conditions in winter, while the soil moisture response is mixed. Multivariate analysis demonstrates tha