Ocean Heat Threatens to Supercharge Storm Season in Europe

Rising temperatures in the ocean now have the potential to cause intense storms in Europe later this year, according to new research.

The Mediterranean sea is heating up twice as fast as the average for oceans in the rest of the world, according to World Weather Attribution, a group of scientists that use peer reviewed methods to perform rapid studies of how climate change feeds into weather patterns. Its analysis shows that parts of the Mediterranean sea and the European Atlantic coast recorded surface temperatures that were more than 6C hotter than would be considered normal in June.

“When we have very warm sea surface temperatures, it provides added energy to storms so it can keep going for a lot longer,” said Catherine Gregory, a researcher at the University of Bern in Switzerland and a co-author of the report.

“It’s a bit of a newer area of research, but it’s probably one of the most important impacts when we talk about how marine heat waves affect humans,” she said.

Man-made global warming was the main driver of record-high sea temperatures registered around the Iberian Peninsula, as well as the Western and Eastern Mediterranean in July, researchers found. Europe, the world’s fastest-warming continent, is struggling to adapt to relentless heat waves that have already resulted in an estimated 25,000 deaths this summer. That’s as rising temperatures hit the economy with commodity supplies, critical infrastructure and energy security all in the crosshairs.

“The heat dome that has been sitting over most of Western Europe for a really long part of the summer has been causing the heat waves over land and the ocean,” said Friederike Otto, a scientist at the Centre for Environmental Policy in London’s Imperial College and a co-author of the report. “They are definitely connected.”

Hot seas are also contributing to heat on land, creating a feedback loop, Otto said. Sea water holds temperatures for longer periods of time, making marine heat waves last longer, increasing humidity in coastal areas and preventing cooling, especially at night.

“During land heat waves, the humidity that comes from the ocean can be incredibly deadly,” said Gregory. “We’ve seen that in Southeast Asia, or in India in the monsoonal seasons, but we’re also seeing that in Southern Europe.”

Researchers analyzed sea temperatures during the last two weeks of July and compared it to past marine heat waves and to historical averages. They found that temperatures in the Bay of Biscay and the western Iberian Peninsula have increased by 1.5C, while the Eastern Mediterranean has warmed by 2.6C and the Western Mediterranean by 3.1C. At the current pace of warming, marine heat waves are set to be 1.3C to 1.9C hotter by the end of the century than those observed this summer.

Hotter oceans are impacting larger areas than would be the case without global warming, the report found. This year, 90% of the Bay of Biscay and the Iberian coast region experienced marine heat wave conditions. That area would be just 40% without man-made climate change. In the Eastern Mediterranean, the current level of 70% would drop to 9%.

European summers are now associated with more extreme marine heat waves, but rapid warming is also starting earlier and lasting longer, the report found.

Photograph: Lightning striking over Nice, France, on Aug. 14, 2024; photo credit: Valery Hache/AFP/Getty Images

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