An investigation by the “World Weather Attribution” initiative-which involved scientists from Switzerland, Sweden, the United States, Ireland, and the United Kingdom-demonstrates that the high sea surface temperatures recorded in July along the Spanish north coast, the French west coast, and across the western and eastern Mediterranean would have been “practically impossible” without human-caused global warming. According to the study, elevated temperatures in the Celtic Sea and other marine areas around Great Britain and Northern Ireland would typically only be observed once in a hundred years in a climate without climate change.
In today’s climate, which is 1.4 degrees Celsius warmer, such extreme sea surface temperatures are becoming far from rare. In the western Mediterranean basin, periods where sea surface temperatures reach levels seen this past July are expected to occur, on average, every five years over a two-week duration. In the eastern Mediterranean, these occurrences are anticipated annually. During this July period, the Mediterranean recorded sea surface temperatures that were up to six degrees Celsius warmer than normal.
These extremely high marine temperatures pose severe threats to marine ecosystems, potentially leading to mass die-offs among corals, sponges, and macroalgae. The loss of these foundational species would fundamentally alter the structure and function of the entire ecosystem. Consequently, there is a risk of mass mortality extending down the food chain to include invertebrates, fish, seabirds, and marine mammals.
The rising sea temperatures also influence human health. The European Centre for Disease Prevention and Control (ECDC) has warned that prolonged heat periods increase the risk of waterborne illnesses such as vibriosis. Furthermore, warmer waters in coastal regions lead to hotter air and higher humidity, exacerbating heat stress for residents. Increased evaporation from the warm seas adds moisture to the atmosphere, which can eventually lead to intense precipitation events later in the season.
While adapting to rising sea temperatures can partially increase resilience, scientists warn that this adaptation cannot fully offset the ecological consequences of sustained oceanic warming. They urge global action to reduce the added pressure on marine ecosystems, protect habitats, and improve early warning systems. The researchers conclude that the current climate is already producing “temperatures that exceed what many species living in our oceans today can tolerate.” Therefore, an immediate transition away from fossil fuels is indispensable to save vital ecosystems, the fishing industry, food production, and tourism along European coasts.
