The Balearic Islands record the warmest sea temperatures in their history in 2025

In 2025, the Mediterranean Sea reached water temperatures up to 6.5 °C above the average recorded between 1982 and 2015 in some areas, with an average of 190 marine heatwave days across the entire Mediterranean. According to SOCIB’s 2025 Annual Report, the Balearic Islands experienced the warmest year on record in terms of sea surface temperature.

These findings are presented in the “Annual Report 2025: Global Warming Impacts in the Mediterranean Sea and Balearic Islands Region” by the Balearic Islands Coastal Observing and Forecasting System (SOCIB), and are based on data processed using its monitoring tools for ocean indicators and marine heatwaves in the Mediterranean. According to SOCIB scientist Mélanie Juza, “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 coastal buoys, underwater gliders and autonomous drifting profiling floats, confirming the continuity and intensification of ocean warming throughout the basin and the water column.

Globally, 2025 was classified as the third warmest year on record, while the period 2023–2025 marked the first three-year average exceeding 1.5 °C above 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.

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 basin-wide annual mean sea surface temperature reached 21.1 °C, making it the second warmest year on record, surpassed only by 2024.

The Balearic Islands were among the most affected regions. In 2025, the area recorded its warmest year ever in terms of sea surface temperature, following a sequence of exceptionally warm years since 2022.

During an extreme marine heatwave in June and early July, the regional mean sea surface temperature reached 28.4 °C on July 3, with temperatures nearly 5 °C above the 1982–2015 average. In situ observations from coastal buoys recorded local temperatures close to 31 °C, highlighting the scale of the event in coastal waters.

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.

As Juza explains, “unprecedented sea surface temperatures were associated with marine heatwaves worldwide, particularly in the Mediterranean Sea,” where these extreme events have become increasingly intense and persistent.

In 2025, the Mediterranean recorded 190 marine heatwave days, with basin-wide average peak intensities exceeding 4 °C above the historical mean (1982–2015). The western Mediterranean was especially affected in June and July, when all subregions experienced very intense and prolonged events. On July 2, 2025, sea surface temperatures in the Ligurian–Provençal area averaged 6.5 °C above normal, locally reaching nearly 8 °C in coastal areas of the Gulf of Lion.

The report also documents record ocean salinity levels in the eastern Mediterranean, linked to increased evaporation driven by warmer waters. At the same time, sea level rise continued to accelerate, with an average basin-wide trend of 3.4 cm per decade since 1993, and even higher rates in some subregions.

In the Balearic Islands, 2025 was a record year for sea level rise, surpassing previous records set in 2023 and 2024.

Rising ocean temperatures and extreme marine heatwaves 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 meadows, which are essential for biodiversity, carbon storage and coastal protection.

The report also highlights growing risks for 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.

The full 2025 Annual Report is available online and provides detailed analyses, figures and access to SOCIB’s monitoring tools.