Anthropogenic climate change detected in European renewable freshwater resources

Although there is overwhelming evidence showing that human emissions are affecting a wide range of atmospheric variables(1), it is not clear whether anthropogenic climate change is detectable in continental-scale freshwater resources. Owing to the complexity of terrestrial hydro-systems there is to date only limited evidence suggesting that climate change has altered river discharge in specific regions(2-5). Here we show that it is likely(6) that anthropogenic emissions have left a detectable fingerprint in renewable freshwater resources in Europe. We use the detection and attribution approach(1,7)to compare river-flowobservations8 with state-of-the-art climate model simulations(9). The analysis shows that the previously observed amplification of the south (dry)-north (wet) contrast in pan-European river flow(10) is captured by climate models only if human emissions are accounted for, although the models significantly underestimate the response. A regional analysis highlights that a strong and significant decrease is observed in the Mediterranean, generally along with a weak increase in northern Europe, whereas there is little change in transitional central Europe. As river and streamflow are indicators for renewable freshwater resources(11-13), the results highlight the necessity of raising awarenessonclimatechange projections(5,14) that indicate increasing water scarcity in southern Europe.