The Mediterranean is warming: impact, causes, and effects of an increasingly warm sea

  • Mediterranean Sea temperatures are up to 4-5°C above normal in many areas, especially around the Balearic Islands and the eastern coast of Spain.
  • The warming of the Mediterranean is linked to phenomena such as more violent storms, tropical nights, and increased evaporation.
  • This phenomenon has multiple causes: absence of cold winds, persistent anticyclones, and anomalies inherited from winter.
  • The environmental and social consequences range from coastal climate change to decreased phytoplankton production, affecting biodiversity and local economies.

Mediterranean Sea with warm temperatures

El unusual increase in temperature The Mediterranean Sea is attracting the attention of the scientific community and society in general. Just a few days before the start of summer, measurements show that many areas of the Mediterranean basin are experiencing thermal values ​​typical of mid-August, just as June has begun. This phenomenon, far from being a one-off, highlights a worrying trend that has been growing for years.

The causes of this thermal increase are not reduced to a single variableOn the one hand, the absence of cold winds, especially the Tramontana, has prevented the upwelling of cooler, deeper waters. On the other hand, the persistence of subtropical anticyclones has favored clear skies and warm air masses, increasing sunshine over the sea. Furthermore, we are coming off a winter and spring with higher than usual temperatures, so the sea was already starting from high values before the summer season even begins.

Record temperatures and anomalies across the basin

Warmest regions of the Mediterranean

According to the latest data from coastal observatories and official buoys, The surface temperature of the western Mediterranean exceeds normal values ​​by 3-4 °C and even reaches anomalies of up to 5 °C in some areas of southern France and the Italian coast. On the Iberian Peninsula, the figures recorded on the Valencian coast, the Balearic Sea and the Balearic Islands are notable, where they have reached 28 ºC in Pollença, 26,99 ºC in Mahón and more than 25 ºC near Valencia.

Along the rest of the coast, the waters remain equally warm: between 24 and 26°C in Tarragona and the Valencian Community; 22-24°C on the Catalan coast, Almería, and Granada. Even in traditionally cooler areas such as the Gulf of Lion and the Alboran Sea, temperatures are well above normal for this time of year.

Immediate effects on climate and weather

Intense storms linked to ocean warming

The consequences of The warming of the Mediterranean is already noticeable in everyday life. Increased evaporation and water vapor in the atmosphere are favoring the proliferation of tropical nights, those early mornings when the thermometer never drops below 20°C. Furthermore, the presence of a superheated sea provides additional energy to weather systems, fueling more intense storms and torrential rains, often accompanied by sizable hail.

An example of this situation has been seen in recent storms in parts of Aragon and Catalonia, with unseasonable rain and hail causing damage and rescues. It is expected that, if atmospheric conditions are right—with cold air dropping to altitude at the end of summer—the impact of this heat retained at sea will translate into extreme weather events.

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A global phenomenon, but with special impact on the Mare Nostrum

Global marine warming trend

The Mediterranean is not alone in this trend. Globally, average ocean temperatures (excluding the poles) have set records in recent years, reaching significantly above the average of recent decadesHowever, due to its particular configuration, the Mediterranean basin is especially vulnerable: it is a small and closed sea, where the Atmospheric changes quickly translate into water, intensifying the speed and magnitude of warming episodes.

Specifically, The maritime area of ​​the Balearic Islands is the one that has suffered the most from the warming, with an increase of 1,3°C, double that recorded in other maritime areas of Spain. In fact, in recent years, the highest sea surface temperatures have occurred in 2022, 2023, and so far in 2025.

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Ecological and social impacts: phytoplankton, biodiversity and economy

Impact on marine ecosystems

The marine thermal rise not only affects the climate, but also is having direct consequences on ecosystems and human activitiesA recent study has highlighted that In the last two decades, phytoplankton production in the northwestern Mediterranean has fallen by around 40%., mainly due to changes in wind patterns and the weakening of nutrient-rich deep-water upwellings. These organisms are crucial because they capture CO2 and form the basis of the marine food chain, so their decline also impacts fisheries and oxygen production.

Furthermore, the alteration of rainfall patterns, the increase in heat waves, pressure on water resources, and the emergence of new species and the loss of biodiversity are collateral effects that are already beginning to be seen in both the natural environment and the economy of many coastal areas.

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