Mediterranean Sea warming and marine heatwaves in 2024

This study offers an assessment of Mediterranean Sea surface temperature (SST) trends (1982–2024) and marine heatwaves (MHWs) for the period 2002 to 2024, with a special focus on the last year, using three MHW detection approaches: a fixed baseline (1982–2011), a 20-year moving baseline, and detrended SST data. Our trend analysis reveals a significant warming signal across the basin, with an average rate of 0.032 ± 0.001 °C yr ⁻¹ and mean anomalies of 1.23 °C in 2024 relative to the 1982–2024 period. When evaluating MHW characteristics, 2024 stands out as the most extreme year of the past two decades in terms of total MHW days, regardless of the detection method. The Eastern Mediterranean (EMed) experienced record MHWs in 2024 across all three detection approaches. It recorded the highest number of MHW days and the longest mean event durations over the study period and also showed the highest mean intensities under the fixed baseline. In the Western Mediterranean (WMed), 2024 featured an exceptional number of MHW days; however, both the duration and intensity of events remained below those of 2003, 2022, and 2023, particularly when using the moving baseline and detrended methods, which reduce the influence of long-term warming. These results underscore the importance of MHWs in 2024 in the Mediterranean Sea, particularly in the EMed. In addition, this study highlights how methodological choices in MHW detection significantly shape the characterisation of extreme marine heat events in a warming climate.