Record-breaking sea temperatures across Europe were driven primarily by human-caused climate change, scientists said, warning that the extraordinary heat is putting marine ecosystems and coastal communities under growing pressure.
The seas surrounding Europe have been swept into the same extreme heat that has gripped much of the continent this summer.
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In July, the Mediterranean’s average temperature reached 27C — the highest recorded for the month — while an offshore buoy near Mallorca measured 33C in early August.
An analysis by the World Weather Attribution (WWA) group found that human-caused climate change had added roughly two degrees of warming to the Mediterranean and about 1.4C to the seas around Western Europe. The group uses peer-reviewed methods to examine how global warming influences extreme weather events.
According to the analysis, the highest temperatures recorded this year in the eastern and western Mediterranean, as well as along the Bay of Biscay and the Iberian coast, would have been “virtually impossible” without human-caused climate change.
In the Celtic Sea, off Ireland and Britain, temperatures at the most extreme end would occur only about once a century under climate conditions unaffected by human activity, the researchers found.
Warmer seas raise humidity and nighttime temperatures in coastal areas. They can also supply additional energy for intense storms later in the year.
A woman uses an umbrella to protect herself from the sun during a heatwave in Milan, Italy this summer
Greenhouse gas emissions, largely produced by burning fossil fuels, have pushed the planet’s average temperature to about 1.4C above pre-industrial levels, according to the World Meteorological Organization.
That warmer starting point allows the high-pressure atmospheric systems behind heatwaves to produce even higher temperatures.
Sudden rises in sea temperatures can trigger mass die-offs among species including corals, while disrupting food supplies for birds and mammals and sending effects through entire food chains.
John Bruno, a marine ecologist at the University of North Carolina, said some species were shifting northward in search of cooler waters, although others lacked the ability to adapt quickly enough.
“We are rapidly approaching the absolute biological limits of adaptation for many species,” he said.
The WWA analysis estimated that marine heatwave conditions had affected about 90% of the Bay of Biscay and 80% of the western Mediterranean this year.
In a world without global warming, the researchers said, the figure would have been closer to 40%.
