The impact of climate change on global river flow in HadGEM1 simulations

Climate change could have significant impacts on the availability of freshwater and the frequency and severity of flooding, with major implications for society. The latest version of the Hadley Centre General Circulation Model, HadGEM1, includes the TRIP (total runoff including pathways) global river routing scheme. We have analysed the predicted changes in global river flow under the IPCC SRES A1B and A2 scenarios from HadGEM1-TRIP simulations. Global total river flow was predicted to increase by 4–8% during the 2071–2100 period relative to 1961–1990, although there were large regional differences—for example, large increases in river flow in boreal regions and western Africa, and large decreases in river flow in southern Europe and North Africa. Significant changes in the seasonality of river flow could also occur, such as earlier peaks in spring runoff in boreal rivers due to earlier snow melt. In our simulations, large increases in monthly maximum flow and decreases in monthly minimum flow were found, although the increases in monthly maximum flow were generally larger. Thus, climate change is likely to increase the occurrence of both high and low flows, although the increased high flows could be dominant. © Crown Copyright 2006. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd.