How might European Water Resources Change as a Result of a Two Degree Global Warming?

This study presents the potential changes to European water resources including mean river discharges, soil moisture stores and flood return levels, as a result of a +2 degree level of global warming. Changes were estimated using a multi-model ensemble made up of five pan-European hydrological models driven by eleven bias-corrected CORDEX climate change simulations representing three different RCPs (2.6, 4.5 and 8.5). This gave a total of 55 simulations, each centred on the time when the global temperature predicted by the GCM exceeds the preindustrial level by 2°C. Changes were compared to the 1971-2000 reference period. The five pan-European hydrological models are E-HYPE, Lisflood, LPJmL, VIC and WBM. River discharge is projected to increase in the majority of Europe in a +2 degree climate. The largest increases occur in the east and the far north while discharge decreases in parts of the Mediterranean. The spatial distribution of changes in discharge mainly followed the predicted changes in precipitation. Flood return periods were shown to ……Soil moisture is predicted to decrease for the southwestern Mediterranean regions, while other soil moisture changes were not consistent between models. Due to a large spread in model outcome the projected changes in discharge are only significant for about half of Europe’s area, where significant changes were defined as those where the absolute value of the median projected change across all ensemble members exceeds the standard deviation for any grid cell. It was found that uncertainty in discharge change was to a larger extent due to the climate models than to the hydrological models whereas uncertainty in soil moisture changes was mainly due to the hydrological models.