Europe’s oceans reach record temperatures as marine heatwaves intensify. Europe experienced its highest sea surface temperatures on record in 2025, marking the fourth consecutive year of unprecedented ocean warming, according to the latest European State of the Climate report from Copernicus. The findings highlight the accelerating impacts of climate change on European seas, with far-reaching consequences for marine ecosystems, biodiversity, fisheries, and coastal economies.
The annual average sea surface temperature across the European region reached 10.94°C in 2025, which was 0.65°C above the long-term average. Record-high temperatures were observed across 23% of European waters, including large areas of the north eastern North Atlantic, the North Sea, the Norwegian Sea, and the western Mediterranean Sea.
One of the most significant developments was the widespread occurrence of marine heatwaves—extended periods of unusually high ocean temperatures. A record 86% of Europe’s marine region experienced strong marine heatwave conditions during the year, while 36% of the region faced severe or extreme conditions. In the Mediterranean Sea, marine heatwaves have evolved from occasional events into recurring annual phenomena affecting the entire basin. Scientists have linked these prolonged warming events to mass mortality episodes in coastal ecosystems and growing disruptions to marine biodiversity.
The report also revealed that the amount of heat stored in the ocean, known as ocean heat content, reached a record high in 2025. Globally, the ocean has absorbed approximately 90% of the excess heat generated by human-induced greenhouse gas emissions, making it a critical buffer against climate change. However, several European seas are warming faster than the global ocean average, with Arctic waters experiencing the most rapid increases in temperature.
Rising ocean temperatures are also contributing to accelerating sea-level rise. Since 1999, global mean sea level has increased by 9.4 centimetres, with the rate of rise accelerating from 2.9 millimetres per year between 1999 and 2009 to 3.8 millimetres per year between 2015 and 2025. Approximately 30% of this rise is attributed to the thermal expansion of warming ocean water, while 60% results from melting glaciers and the Greenland and Antarctic ice sheets. The remaining 10% is linked to changes in land and water storage.
Together, these findings underscore the growing influence of climate change on Europe’s oceans and coastlines. As marine heatwaves become more frequent and severe, and sea levels continue to rise, the environmental, economic, and social challenges facing coastal communities are expected to intensify in the years ahead.
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