Recent hot and dry summers in Germany in comparison to climate projections

Abstract

This study investigates whether the recent extremely hot and dry summers (2003, 2015, 2018 and 2019) in Germany will be normal summer conditions under future climate change scenarios. Abnormally persistent high-pressure systems during these recent German summers maintained clear skies and dry conditions on the ground, resulting in record-breaking heat and drought conditions. Here, climate indices are calculated from the German Meteorological Service's (DWD) climate model reference-ensembles for periods 2031–2060 and 2071–2100 under greenhouse gas emission scenarios RCP 2.6 (11 ensemble members) and RCP 8.5 (21 ensemble members) and are compared with climate indices calculated from three DWD observational datasets (station data and gridded datasets: HYRAS and DWD Climate Monitoring Grids). The climate projections show increasing summer heat conditions for Germany throughout this century and a slight shift to dryer conditions, especially for the RCP 8.5 scenario. These recent extreme summers are often in the 15 % hottest summers for RCP 2.6 in 2031–2060, 2071–2100 and the RCP 8.5 2031–2060 scenarios, but would be considered normal or even cool summers under the RCP 8.5 scenario in 2071–2100. Due to the combination of extreme heat and strong precipitation deficits, the climatic water balance and derived meteorological drought indicator values of these recent summers are often within the top 15 % of projected extreme summer drought indices and are sometimes only matched by the most anomalous hot and dry summers in the DWD reference-ensembles, even for the high-emission RCP 8.5 scenario in 2071–2100.

Keywords

• climate change
• climate indices
• extreme events
• drought
• heatwaves