Storylines simulations suggest intensification of recent European droughts in warmer climates.

According to the latest IPCC report, under the ongoing climate change, extreme weather events in Western Continental Europe, including heatwaves and droughts, are becoming more prolonged, intense, and frequent, and are set to strengthen in a progressively warmer climate. Total changes observed in these extreme events can be discriminated between the relative contributions of dynamical changes – change in likelihood of weather patterns  – and of thermodynamic changes. While the former remains uncertain in future climate projections, the latter is more certain, with a robust and ubiquitous rise in future land-surface temperatures.

To separate and analyze both contributions, we employ the nudged storyline approach, in which our CMIP6 coupled climate model (AWI-CM1) is nudged towards the observed large-scale free-troposphere dynamics using different climate background conditions and initial states. As a result, the same weather conditions, including jet stream and blockings, are simulated in different climates (pre-industrial, present and future 2, 3 and 4 ºC warmer climates). This methodology provides a very efficient manner of making the consequences of climate change more comprehensible to non-experts and experts alike, as extreme events fresh in people's memory are simulated in different climates with just moderate computational resources.

This configuration reproduces recent extreme events, like the 2019 or 2022 European heatwaves and the ongoing European drought. Our simulations reveal an intensification of these hot and dry extreme events both from preindustrial to present (attribution) and from present to warmer (projection) climates. Moreover, taking advantage of our methodology, observed and projected changes can mainly be attributed to thermodynamic changes, with dynamical changes playing a minor role.