Co-occurrence of marine and atmospheric heatwaves with drought conditions and fire activity in the Mediterranean region.

Climate change has become a major concern in the twenty-first century, leading to the amplification of extreme events and, consequently, to severe impacts on society, economy and ecosystems. Heatwave conditions in particular, often coupled with extended periods of dryness, have an important contribution in exacerbating rural fires. Here, we propose to analyse the co-occurring interplay between atmospheric heatwaves and droughts in southern Europe, and marine heatwaves in the East Atlantic and the Mediterranean Sea, between 2001 and 2022, highlighting their linkage to wildfires, on both an individual and compound approach. Positive correlations between air and sea temperatures and negative correlations between air temperature and precipitation values were found. Our analysis reveals that severe wildfires are mostly associated with reduced precipitation and/or elevated air temperatures during the summer season, alongside heightened sea surface temperatures. Marine hot (drier) conditions are prevalent for months in which burned areas remain below (above) the 80th percentile. Months marked by higher fire activity are predominantly associated with extreme climatic conditions, showcasing a substantial occurrence of compound events. This study highlights the potential of considering both land-based atmospheric and marine conditions when exploring compound extremes, crucial for mitigating climatic disasters. Moreover, it highlights the role played by compound extreme events in fire management strategies, particularly considering the present context of climate change and the increasing frequency and severity of extreme events threatening ecosystem stability.