Storyline Attribution of the 2025 Mediterranean Summer Fire Weather

The Mediterranean is a climate change hotspot where increasing temperatures and changing hydroclimate are intensifying wildfire risk. In the summer of 2025, the fire season was extremely destructive, with human casualties, homes destroyed, and large areas of forest and agricultural land burned. While previous studies have primarily relied on probabilistic or trend-based approaches to understand how climate change affects fire weather conducive to such fire seasons, process-based conditional attribution remains limited. Here, we apply a spectrally nudged storyline approach to conditionally attribute the thermodynamic contribution of climate change to the Fire Weather Index (FWI) in the Mediterranean during July–August 2025.

We find a robust increase in fire weather across the Mediterranean under climate change, with higher FWI values in all regions when comparing present-day to pre-industrial conditions. This increase becomes even more pronounced under +3 and +4 °C warming levels, although with greater regional variability in robustness. The strongest and most spatially coherent signal is driven by temperature increases, while reductions in relative humidity and precipitation further amplify fire-conducive conditions in specific regions. The magnitude and robustness of the signal vary spatially, with clearer responses in western Mediterranean countries and more variability in regions with low precipitation.

These results demonstrate that climate change has intensified the atmospheric conditions conducive to wildfires during the Mediterranean summer of 2025. More broadly, this study highlights the value of conditional storyline attribution for providing an event-based understanding of extreme events. As an intermediate metric, the Fire Weather Index offers a bridge between atmospheric conditions and wildfire impacts, suggesting a pathway to extend attribution frameworks towards impact-based assessments.