Global flood risk under climate change

A warmer climate would increase the risk of floods(1). So far, only a few studies(2,3) have projected changes in floods on a global scale. None of these studies relied on multiple climate models. A few global studies(4,5) have started to estimate the exposure to flooding (population in potential inundation areas) as a proxy of risk, but none of them has estimated it in a warmer future climate. Here we present global flood risk for the end of this century based on the outputs of 11 climate models. A state-of-the-art global river routing model with an inundation scheme(6) was employed to compute river discharge and inundation area. An ensemble of projections under a new high-concentration scenario(7) demonstrates a large increase in flood frequency in Southeast Asia, Peninsular India, eastern Africa and the northern half of the Andes, with small uncertainty in the direction of change. In certain areas of the world, however, flood frequency is projected to decrease. Another larger ensemble of projections under four new concentration scenarios(7) reveals that the global exposure to floods would increase depending on the degree of warming, but interannual variability of the exposure may imply the necessity of adaptation before significant warming.