Record European sea heat ‘virtually impossible’ without climate change, study finds

Human-caused climate change was the main driver of record-breaking sea temperatures around Europe this summer, with peak temperatures in the Mediterranean and along the Bay of Biscay deemed "virtually impossible" without global warming, according to an analysis published Wednesday by the World Weather Attribution group.

Unprecedented Heat Beneath the Waves

The Mediterranean recorded an average temperature of 27°C last month, the highest for any July on record, while an offshore buoy near Mallorca registered 33°C in early August, according to Reuters. Some Mediterranean areas saw sea surface temperatures more than 6°C above normal during the hottest two weeks of the month.reuters+1

The WWA analysis, conducted by researchers from Switzerland, Sweden, the United States, Ireland, and the United Kingdom, found that climate change has added about 2°C of warming to the Mediterranean and around 1.3 to 1.4°C to Western European seas. In the Celtic Sea, off Britain and Ireland, the most extreme temperatures recorded would have been expected only about once a century without human-caused warming.worldweatherattribution+2

"From the Atlantic waters off Ireland to the Mediterranean Sea, Europe's seas are experiencing an alarming surge in temperatures," said co-author Thomas Frolicher, an environmental physicist at the University of Bern.yahoo

Marine Ecosystems Under Threat

The study warned that extremely high sea surface temperatures are already causing severe ecological damage. Marine heatwave conditions now cover about 90% of the Bay of Biscay and Iberian coast and 80% of the western Mediterranean — figures that would have been closer to 40% without global warming.worldweatherattribution+1

The WWA report documented species shifting northward to cooler waters, disrupting food chains and coastal fisheries. In the UK, fishermen have reported a surge in octopuses, while dolphins have reportedly turned to feeding on jellyfish as their usual prey declines.worldweatherattribution

"We are rapidly approaching the absolute biological limits of adaptation for many species," said John Bruno, a marine ecologist at the University of North Carolina.reuters+1

Claire Bergin, a climate scientist at Maynooth University and a co-author of the study, noted that "warmer waters for swimming may sound appealing to beachgoers," but "the impacts on marine life beneath the surface are more serious".yahoo

Risks Beyond the Ocean

The consequences extend well beyond marine life. Hotter seas increase humidity and overnight temperatures in coastal areas, worsening heat stress for communities, and can help fuel intense storms later in the year. The WWA noted that high Mediterranean temperatures have previously been linked to extreme rainfall events, including the Valencia floods in 2024.bloomberg+2

The study projected that with an additional 1.4°C of future warming, events like those observed this summer would become another 1.3 to 1.9°C hotter, pushing temperatures beyond what many marine species can tolerate. The researchers concluded that "a rapid transition away from fossil fuels is essential to save crucial ecosystems, fisheries, food production and tourism along the European coasts".worldweatherattribution