Climate change is driving record heat in Europe's seas, scientists say

Mediterranean warms nearly 2 degrees Celsius due to human activity, with peak temperatures otherwise 'impossible'

Human-caused climate change was the main driver of recent record-breaking sea temperatures around Europe, scientists said on Wednesday, warning of severe consequences for marine ecosystems and coastal communities.

Europe's seas have not escaped the extreme heat that many countries have endured this summer. Last month, the average temperature in the Mediterranean was 27 degrees Celsius (81 degrees Fahrenheit), the highest for any July on record, while an offshore buoy near Mallorca recorded 33 degrees Celsius in early August.

Human-caused climate change has added about 2 degrees Celsius of warming to the Mediterranean and around 1.4 degrees Celsius to Western European seas, according to an analysis by the World Weather Attribution (WWA) group, which uses peer-reviewed methods to assess global warming's role in extreme weather events.

"This has the potential to completely reshape ecosystems that coastal communities rely on for food and income, and drive damaging extreme weather on land too," said Claire Bergin, a climate scientist at Ireland's Maynooth University and a co-author of the study.

Read: Global temperatures to reach near-record highs in next five years, report finds

The analysis found that peak sea temperatures recorded this year in the eastern and western Mediterranean and along the Bay of Biscay and Iberian coast would have been "virtually impossible" without human-caused climate change.

In the Celtic Sea, off Britain and Ireland, the most extreme temperatures recorded would have been expected only about once a century in a world without human-caused climate change, it found.

Hotter seas increase humidity and overnight temperatures in coastal areas and can help fuel intense storms later in the year.

Greenhouse gas emissions, mainly from ​burning fossil fuels, have raised the planet's average temperature to around 1.4 degrees Celsius above pre-industrial levels, according to the World Meteorological Organisation. This hotter baseline means the high-pressure atmospheric systems that cause heatwaves can reach higher temperatures.

Read More: Europe's heatwave 'virtually impossible' without climate change, scientists say

Sea temperature spikes can cause mass die-offs of species such as corals and disrupt food supplies for birds and mammals, with knock-on effects through food chains.

John Bruno, a marine ecologist at the University of North Carolina, said some species were moving north to seek cooler waters, but not all could adapt. "We are rapidly approaching the absolute biological limits of adaptation for many species," he said.

According to the WWA analysis, about 90% of the Bay of Biscay and 80% of the western Mediterranean have experienced marine heatwave conditions this year. Without global warming, that figure would have been closer to 40%.