How climate models reproduce the observed increase in extreme precipitation over Europe

The last years extreme precipitation and flooding events demonstrate the necessity to investigate how climate models represent the response of extreme precipitation to a warming climate to better prepare for flooding hazards. In this study we investigate heavy to extreme precipitation that has been observed over Europe since the 1950s, and how this increase is represented in climate models, with a particular focus on the frequency vs. intensity increase of heavy precipitation events. We compare observations and reanalysis against global and regional downscaled climate models which include one or multiple ensemble members. We find that some of the climate models manage to reproduce the observed increase in extreme precipitation with around a 20% increase for the 99th percentile from 1955-1984 to 1985–2014, with a large diversity between the models. The inter-model diversity for increase in extreme precipitation is found to show a larger spread compared to the intra-model spread represented by the variability between the different ensemble members. Model results show, similarly to observations, that frequency increases more than intensity, with around 20% vs. 5% increase, respectively, for the 99th percentile. This pattern strengthens with rareness of extreme events, however, the diversity between the models also increases with extremeness of the events. Results presented here show the need to account for the change in the very extreme events (> 99.9th percentile), as excluding these rare events may conceal how extreme future events will be. Over the land grid points, the frequency increase of extreme precipitation per intensity increase shows little variability for the global models, while the regional downscaled models, show a large variability in this frequency- intensity ratio, also larger than found for observations and reanalysis. The reasons why the models respond differently to climate change and how they respond to future global warming need to be investigated further.