The sea offers no respite. While heat waves rage on land, a silent battle is being waged beneath the surface against rising temperatures. The latest data from the Copernicus Climate Change Service confirms that July 2026 broke the record for average ocean temperature once again, reaching 20,96 degrees Celsius across the extrapolar ocean. This marks the second consecutive month with a record high, an unmistakable sign that marine warming is accelerating.
The Mediterranean, one of the most vulnerable seas, is experiencing a Category 4 (extreme) marine heatwave, according to NOAA, with temperatures reaching 33 degrees Celsius at the Sa Dragonera buoy in Mallorca. The waters surrounding the Iberian Peninsula and its islands are warming 67% faster than the global average, at a rate of 0,25 degrees Celsius per decade. In response, Greenpeace has called on governments to implement an urgent and ambitious plan to halt a phenomenon that is already disrupting the balance of marine ecosystems.
A record-breaking July in the oceans
The global data leaves no room for doubt: the average sea surface temperature in the extrapolar ocean reached 20,96°C, surpassing the previous record of 20,89°C recorded in July 2023. This increase occurs within a context of progressive ocean warming , as the oceans absorb more than 90% of the excess heat generated by greenhouse gas emissions. However, this regulatory role is reaching its limits, and the consequences are already being felt in the form of more extreme weather events.
The Atlantic and the western Mediterranean also recorded record temperatures, associated with intense marine heat waves. In the tropical Pacific, the El Niño phenomenon has contributed to maintaining exceptionally high temperatures, although experts point out that global warming is the dominant factor. The combination of these factors has led to July 2026 being the second warmest July on record globally, second only to 2023.
The Mediterranean, in critical condition
The Mediterranean is one of the fastest-warming seas in the world. According to Copernicus data, 100% of its waters have experienced marine heatwaves at some point during the year since 2022 , and temperatures have remained above average almost continuously since 2023. The current heatwave, classified as Category 4 (extreme) by NOAA, has caused the Sa Dragonera buoy in Mallorca to record an unprecedented 33°C.
This warming doesn't just affect surface temperatures. Background heat waves, although less visible, can be even more intense. Furthermore, these events alter phytoplankton dynamics, the base of the marine food web, with cascading effects on the entire ecosystem. In the Cantabrian Sea, the Bilbao-Vizcaya buoy has recorded record monthly temperatures since April, exceeding 25,2 °C in July, yet another indication that the problem is not exclusive to the Mediterranean.
Consequences for climate and biodiversity
Ocean warming has direct effects on the climate. Warmer water evaporates more moisture, fueling storms and more intense episodes of torrential rain . Furthermore, the disruption of ocean currents, responsible for distributing heat around the planet, contributes to greater climate instability. The reduction of oxygen in warmer waters increases stress on ecosystems, and artisanal fisheries, which depend on nearby fishing grounds, are particularly affected by ocean warming and the decline in fish biomass.
Marine biodiversity is also suffering. Species adapted to temperate waters are migrating to colder latitudes, while invasive species are colonizing new areas. Organisms such as corals and Posidonia oceanica seagrass meadows , essential for the habitat of many species, can exceed their thermal tolerance limits and suffer mass mortality events. Furthermore, rising water temperatures are accelerating sea level rise due to thermal expansion, exacerbating coastal erosion and the risk of flooding. Numerous Spanish beaches are already showing signs of retreat, a combination of the impacts of climate change and urban development.
The necessary answer
Faced with this series of records, Greenpeace has demanded an urgent and ambitious response from governments. The organization is calling for a drastic reduction in greenhouse gas emissions , an accelerated phase-out of fossil fuels, and strengthened protection and restoration of marine ecosystems. "Every tenth of a degree the sea warms means more energy available to fuel extreme weather events and a greater impact on ecosystems," said Elvira Jiménez, Greenpeace's Climate Change Adaptation Officer.
Experts agree that this trend will continue if decisive action is not taken. The creation of marine sanctuaries, limitations on industrial fishing, and a ban on deep-sea mining are some of the proposed measures. But above all, urgent action is needed to combat global warming at its source, by reducing emissions and investing in clean energy.
Ocean warming is no longer a future threat, but a reality transforming our oceans and coastlines. Record temperatures are being broken, the Mediterranean is burning underwater, and biodiversity is suffering. The science is clear: every tenth of a degree counts, and the window for action is narrowing. The response must be immediate, coordinated, and ambitious, because what happens beneath the surface affects everyone, from the climate to the economies of coastal communities.
