Atmospheric circulation compounds anthropogenic warming and its impacts in Europe

by Prof. Davide Faranda (LSCE IPSL)

Wednesday 19 Oct 2022, 15:00 → 16:00 Europe/Rome

SNS - Centro De Giorgi - Aula Seminari

The thermodynamic effects of the global-mean anthropogenic warming on the climate system are well documented. However, diagnosing dynamical changes such as those in atmospheric circulation patterns, remains challenging -- all the more when focusing on extreme events. Here, we study 1948--2020 trends in the frequency of occurrence of atmospheric circulation patterns over the North Atlantic. We identify a positive feedback of the circulation that favors extreme events in Europe under anthropogenic forcing. Only a small number of atmospheric circulation patterns display significant trends in frequency of occurrence in recent decades, yet they have major impacts on surface climate. Increasingly frequent patterns drive summertime dryness and heatwaves across Europe, and enhanced wintertime storminess in the northern half of the continent. Roughly 95% of recent heatwave-related deaths and 33% of high impact windstorms in Europe were concurrent with the atmospheric circulation patterns whose frequency of occurrence has been increasing. Atmospheric patterns which are becoming rarer correspond instead to wet, cool summer conditions across Europe and cold conditions over the northern parts of the continent. The combined effect of these circulation changes is that of a strong, dynamically-driven year-round warming over most of the continent and increased wintertime surface winds and precipitation in Northern Europe.