The Mediterranean Sea in the Balearics reached an average surface temperature of 28.4ºC during the month of July 2025, which is almost 5ºC above the 1982-2015 average. These are some of the data collected in the 2025 annual report of the Balearic Islands Coastal Observation System (Socib), which shows that, in some areas, the Mediterranean reached temperatures up to 6.5°C above the usual average and an average of 190 days of marine heat waves.
These findings have been presented in the “Annual Report 2025: Global Warming Impacts in the Mediterranean Sea and Balearic Islands Region” --’Annual Report 2025: Impacts of Global Warming on the Mediterranean Sea and the Balearics’ by Socib, and are based on data processed using its tools for monitoring ocean indicators and marine heatwaves in the Mediterranean.
The Balearics were among the ‘most affected’ regions. In 2025, the area recorded its “warmest” year in terms of sea surface temperature, following a series of ‘exceptionally warm years since 2022’.
In fact, in situ observations from coastal buoys recorded local temperatures close to 31°C, highlighting the extent of the event in coastal waters. Socib scientist Mélanie Juza pointed out that climate change brought new records in 2025 in terms of ocean temperatures, salinity and sea level in the Mediterranean.
This assessment is based on long-term satellite observations from the Copernicus Marine Service, combined with in situ measurements collected through Socib’s ocean observation infrastructure, including these coastal buoys, underwater gliders and autonomous drifting profilers; confirming ‘the continuity and intensification of ocean warming throughout the basin and water column.’ Globally, 2025 was ranked as the third warmest year on record, while the period 2023-2025 marked the first three-year average above 1.5°C relative to pre-industrial levels.
‘Even without El Niño—a natural climate phenomenon that typically amplifies ocean warming by redistributing heat from the Pacific to the global ocean—sea surface temperatures remained exceptionally high throughout 2025, underscoring the strength of the underlying warming trend,’ they emphasised. In the Mediterranean Sea, satellite observations from the Copernicus programme, processed and analysed using Socib tools, confirm a long-term warming rate of approximately 0.4°C per decade since 1982, with strong regional variability.
In 2025, the average annual sea surface temperature at the basin level reached 21.1°C, making it the second warmest year on record, surpassed only by 2024. This sustained warming was accompanied by an ‘exceptional occurrence’ of marine heatwaves, defined as periods when sea surface temperatures exceed the 90th percentile of historical values for at least five consecutive days.
Juza described the sea surface temperatures as ‘unprecedented’ and explained that they were associated with marine heatwaves around the world, particularly in the Mediterranean Sea, where these extreme events ‘have become increasingly intense and persistent’. In 2025, the Mediterranean recorded 190 days of marine heatwaves, with average maximum intensities at the basin level exceeding 4°C above the historical average (1982-2015).
The western Mediterranean was particularly affected in June and July, when all subregions experienced very intense and prolonged events. On 2 July 2025, sea surface temperatures in the Ligurian-Provençal area were on average 6.5°C above the usual average, reaching locally around 8°C in coastal areas of the Gulf of Lion.
The report also documents record levels of ocean salinity in the eastern Mediterranean, linked to increased evaporation caused by warmer waters. At the same time, sea level rise accelerated, with an average trend in the basin of 3.4 cm per decade since 1993 and even higher rates in some subregions. In the Balearics, 2025 was a record year for sea level rise, surpassing previous records set in 2023 and 2024.
The Socib has explained that rising ocean temperatures and extreme marine heat waves have ‘far-reaching’ effects on ocean systems, marine ecosystems and coastal communities. These include increased stratification, reduced oxygen availability and serious threats to key habitats such as Posidonia oceanica seagrass beds, which are essential for biodiversity, carbon storage and coastal protection. The report also highlights the growing risks to coastal communities and economic sectors such as fisheries and tourism, as well as increased exposure to extreme weather events, coastal flooding and impacts on human health.