ABSTRACT
Lehner et al. (2006) made an integrated European assessment of changes in flood risk due to climate change. They used climate data from the ECHAM4 and HadCM3 General Circulation Models (GCMs), based on a scenario that is largely consistent with the no-policy IPCC-IS92a scenario, in combination with the global integrated water model WaterGAP to define large critical regions of increases in flood and drought hazards. The monthly averaged GCM output was disaggregated in space and time to the temporal scale (daily) and (coarse) spatial scale (0.5 degrees) of WaterGAP. In the climate signal, only long-term trends and changes in seasonal climate were taken into account, while changes in short-range variability were neglected. These assumptions do not allow a proper evaluation of changes in climatic extremes, which may show a very different pattern compared to the average changes in climate, and constrain the reliability of the results with respect to changes in flood hazard. More recently, Dankers and Feyen (2008) evaluated changes in flood hazard in Europe using very high resolution climate data from the HIRHAM regional climate model driven by the SRES A2 greenhouse gas emission scenario. Their results confirm an increase in flood hazard for many European rivers by the end of this century, but in certain regions, notably in the northeast and parts of central and southern Europe, a considerable decrease in flood hazard was found.
