The Mediterranean Sea reached water temperatures up to 6.5 degrees Celsius above the 1982-2015 average in some areas in 2025 and recorded an average of 190 days of marine heatwaves across the entire basin, according to the 2025 Annual Report of the Coastal Observation System of the Balearic Islands (SOCIB).
The report, published this Monday, confirms that the Spanish Balearic archipelago experienced the warmest sea surface temperature year in its history in 2025, in a context of continued and intensified oceanic warming throughout the Mediterranean.
The data is included in the 'Annual Report 2025: Global Warming Impacts in the Mediterranean Sea and Balearic Islands Region' report, developed using SOCIB's oceanic indicators and marine heatwave monitoring tools, which combine long-term satellite observations from the Copernicus Marine Service with in situ measurements obtained through coastal buoys, underwater gliders, and autonomous profiling floats.
According to SOCIB scientist Mélanie Juza, climate change brought new records in 2025 in terms of oceanic temperatures, salinity, and sea level in the Mediterranean, which confirms the continuity and intensification of oceanic warming throughout the basin and in the water column.
On a global scale, 2025 is classified as the third warmest year on record, while the 2023-2025 period marked the first three-year average above 1.5 degrees Celsius compared to pre-industrial levels.
Even in the absence of the El Niño phenomenon, sea surface temperatures remained exceptionally high.
In the Mediterranean, satellite observations from the Copernicus program confirm a long-term warming rate of approximately 0.4 degrees per decade since 1982, with marked regional variability.
In 2025, the annual average sea surface temperature for the entire basin reached 21.1 degrees, making it the second warmest year on record, only behind 2024.
This sustained warming was accompanied by an exceptional occurrence of marine heatwaves, defined as periods when the sea surface temperature exceeds the 90th percentile of historical values for at least five consecutive days.
In 2025, the Mediterranean accumulated 190 days under these conditions, with average intensities exceeding four degrees above the 1982-2015 average.
The western Mediterranean was one of the most affected areas in June and July.
On July 2, 2025, sea surface temperatures in the Liguro-Provençal area were on average 6.5 degrees above usual values, reaching locally nearly eight degrees in coastal areas of the Gulf of León.
The report also documents record salinity levels in the eastern Mediterranean, associated with increased evaporation caused by warmer waters, as well as an acceleration in the rise of sea level.
Since 1993, the average trend in the basin has been 3.4 centimeters per decade, with higher rates in some subregions.
SOCIB warns that the increase in oceanic temperatures and the intensification of marine heatwaves have far-reaching impacts on marine ecosystems and coastal communities, with effects such as increased stratification, lower oxygen availability, and threats to key habitats like Posidonia oceanica meadows.
The report also warns of growing risks for economic sectors such as fishing and tourism, as well as greater exposure to extreme weather events, coastal flooding, and impacts on human health.
