Improvements in the representation of heat extremes in Western Europe in the new EURO-CORDEX generation

The anthropogenic climate change causes some regions to warm faster than others. The poles experience a higher degree of warming than the equator but there are also regions showing different trends than their surroundings. One of these regions warming at an unexpected rate is Western Europe. The observed trends there, especially in single-day heat extremes but also in long, enduring heat waves are significantly higher than those projected in global (CMIP) or regional climate models (EURO-CORDEX) based on the 5th CMIP generation. The significant differences between models and reality were assumed to be caused by the fixed aerosol levels used in RCP-scenarios.
As the storyline approach developed further, this issue was also investigated, e.g. by Singh et al. (2023), and led to a different conclusion: Global climate models fail to represent the present atmospheric dynamic changes which has led to underestimated warming rates. Nevertheless, it remains unclear whether these dynamic changes are caused by anthropogenic effects or not.
The new generation of EURO-CORDEX based on CMIP6 is about to be published in 2026 (as of January 2026). The presented study investigates the differences between the regional model generations based on CMIP5 and CMIP6, especially in representing heat extremes in Western Europe. Although a possible explanation for the significant differences between climate models and recent observations was shown using storylines, it is still necessary to investigate how the differences in the model setups improve the statistical representation of heat extremes. In order to be able to rate the quality of the climate models for heat extremes, a comparison to gridded observational data like E-OBS is performed. This way, it can be seen which regions are well represented in regional climate models of one or both generations and in which regions the models are failing to capture the observed trends and therefore are unsuitable for standard probabilistic attribution studies.
The research of this project is part of the ClimXtreme Network, funded by the German Federal Ministry of Research, Technology and Space (BMFTR). Focus of this project are extreme weather events and impacts caused by anthropogenic climate change.

Literature: Singh, J., Sippel, S. & Fischer, E.M. Circulation dampened heat extremes intensification over the Midwest USA and amplified over Western Europe. Commun Earth Environ 4, 432 (2023). https://doi.org/10.1038/s43247-023-01096-7