Dynamics and attribution of exceptional Mediterranean heatwave in August 2021

Extreme weather and climate events - such as intense heatwaves, prolonged droughts and extensive wildfires - are aspects of the evolution of the climate system that are becoming more frequent and stronger in many parts of the world. Extremes can have substantial environmental and socio-economic impacts depending on vulnerability of exposed population, as well as present infrastructure and assets. In August 2021 extreme heat affected the broader Mediterranean region: on 11 August, a weather station in Syracuse (the birthplace of Archimedes on Sicily), Italy, reached 48.8 °C, the European near-surface temperature record, while Kairouan, Tunisia, reached a record 50.3 °C on the same day. 47.4 °C in Montoro set the national record for Spain on 14 August, while on the same day Madrid had its hottest day on the record with 42.7 °C. This was caused by an extensive heat dome, a large area of high pressure in the upper atmosphere leading to strong downward motion that compresses and heats up air in addition to the contribution from radiative heating. Furthermore, this heating was accompanied by devastating wildfires in several Mediterranean countries. Our study utilises a set of observations and reanalysis products combined with large ensembles of CMIP5/6 simulations to examine the role of anthropogenic drivers in this extreme event. We also use large ensembles of specifically designed historical/factual and natural/counterfactual simulations of EC-Earth3.3 coupled climate model at the standard resolution (T255L91 ORCA1L75) to assesses to what extent anthropogenic forcing modified the probability and magnitude of this event involving conditional perspective of the atmospheric circulation. The preliminary results points to a substantial role of the global climate change in modifying likelihood of this extreme event.