Due to global warming, both the frequency and intensity of extreme heatwaves are projected to increase across Europe. While the thermodynamic contributions to heatwave changes in a warmer climate are fairly well understood, the dynamical contributions are more uncertain. Specific large-scale dynamic setups are a necessary prerequisite for the occurrence of heatwaves in Central Europe, namely persistent ridges or omega blockings which are linked to slow-moving or stationary, high-amplitude Rossby wave trains.

The project has two partners, KIT and Hereon. The KIT contribution focuses on the relationship between atmospheric dynamics and heatwaves, and whether this relationship may change in a future climate. For a robust statistical evaluation of rare heat wave events, large model ensembles (LAERTES-EU, MPI-GE) are used, which encompass both the past and future scenarios. Of particular interest is the question whether subtropical ridges, which play only a minor role for heat waves in recent climate, may play a greater role in future decades. The most extreme heat wave events from the large model ensembles are used to identify the dynamical factors which may uplift such events from “normal” heat waves. In Phase II, focus is given to the new high-resolution climate model data (12km-3km) from the projects EURO-CORDEX and NUKLEUS. Such simulations may allow to further assess to which extent convective systems or precipitation upstream of large-scale blocking weather systems influence the development and duration of heatwaves in a warming climate.

The Hereon contribution deals with the question of attribution of climate change. With this aim, the strongest recently observed heat waves and droughts are simulated with global storyline simulations in order to explicitly work out the influence of anthropogenic global warming. Three climate stages are considered: Pre-industrial, present time and +2 °C warming. These simulations are then downscaled to higher resolutions using a regional climate model. As this approach focuses on thermodynamic changes, it is a perfect complement to the dynamics-focused studies mentioned above.

Website: DesAttHeat

Institution: Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), Helmholtz-Zentrum Hereon (Hereon)

Contact: Prof. Joaquim G. Pinto, Prof. Andreas H. Fink, Dr. Frauke Feser