Prolongation of Compound Dry-Hot Seasons Over Europe Under Climate Change Scenarios

Compound effects of drought and heat are regarded as one of the greatest hazards in relation to climate change. We study characteristics of dry-hot seasons in Europe in an ensemble of CORDEX regional climate models (RCMs). Evaluation against the E-OBS gridded data set for 1976-2005 showed that the RCMs were able to reproduce the spatial pattern of the dry-hot season length but the simulated seasons tended to start later and interannual variability of their length was underestimated. Bias was larger (smaller) in the case of maximum (minimum) length over the 30-year period compared to the median length. Changes in the dry-hot seasons were then analyzed for three time slices (2006-2035, 2036-2065, and 2066-2095) and low and high greenhouse gas concentration pathways. Distinct prolongation (compared to the 1976-2005 simulated climate) was projected for 2036-2065 in the Mediterranean and Western Europe (10-30 days), regardless of the concentration pathway. The dry-hot seasons length was similar in the 2036-2065 and 2066-2095 time slices under the low concentration pathway but major extensions were found under the high concentration scenario over large parts of Europe (20-50 days). The projected spatial patterns of changes in the dry-hot seasons length depend primarily on the driving global climate model. Although the extensions are predominantly driven by increasing temperature, simulated precipitation changes modulate the resulting pattern by amplifying (reducing) the dry-hot seasons length in Southern (Northern) Europe.