The 2025 Mediterranean marine heatwaves through sea surface temperature analogues

The Mediterranean Sea experienced an exceptional marine heatwave throughout June–July 2025. Here we analyse this event using an analogue framework that differs from the common atmospheric circulation-based analogue attribution approach. Instead of identifying atmospheric circulation analogues first, we search directly for historical analogues of the observed sea surface temperature (SST) anomaly pattern of the 20 to 30 June 2025 build-up and peak phase, and then compare the associated atmospheric and air-sea surface conditions in a past (1950 to 1986) and a present (1987 to 2024) period, using ERA5 daily fields over the Mediterranean between June and September. Our results suggest that the present period exhibits higher SST anomalies than the past one, with the strongest positive differences over the western Mediterranean and the Adriatic Sea. Warmer 2 m air temperatures over surrounding land areas and higher net shortwave radiation over large parts of the basin are also observed, while sea level pressure, wind speed, latent heat flux, sensible heat flux, and longwave radiation display smaller and more spatially heterogeneous changes. Thus, the 2025 event occurred in a warmer thermodynamic background than analogous SST patterns in earlier decades. Since the analogue framework cannot fully separate externally forced trends from internal variability and it does not explicitly resolve ocean dynamical processes, these results do not constitute a complete formal attribution on their own. Nevertheless, the analogue analysis supports the interpretation that long term warming contributed substantially to the intensity of the 2025 Mediterranean marine heatwave and shows how SST analogue comparisons can complement existing attribution approaches for marine extremes.