Europe's Seas Reached Heat 'Virtually Impossible' Before Warming, Study Finds
Sea surface temperatures in three of four European sea regions this summer reached a level that "would have been virtually impossible in a pre-industrial climate," World Weather Attribution said in a rapid analysis published Aug. 19.
The analysis, run by researchers based in Switzerland, Sweden, the United States, Ireland and the United Kingdom, covered the Celtic region around Britain and Ireland, the Bay of Biscay and Iberian region, the western Mediterranean and the eastern Mediterranean. For each the group compared observations with climate model simulations, using two definitions of the event: the warmest 14-day stretch of the year, and the warmest 14 days within July.
Over the warmest fortnight, warming raised sea surface temperature by 1.2 degrees Celsius in the Celtic region, 1.5 C in the Bay of Biscay and Iberian region, 3.1 C in the western Mediterranean and 2.6 C in the eastern Mediterranean compared with a pre-industrial climate, WWA reports. Its "virtually impossible" conclusion applies to the last three. For the Celtic region the group puts the probability ratio at about 30, which it says makes this year's heat "a roughly 1-in-100-year event in a climate 1.4°C cooler."
In today's climate, WWA estimates heat of that size recurs about once a year in the eastern Mediterranean and about once in five years in the western Mediterranean.
The area under marine heatwave conditions was also far larger than in the cooler pre-industrial climate, the group reports: 80% against 30% in the Celtic region, 90% against 40% in the Bay of Biscay and Iberian region, 80% against 40% in the western Mediterranean, and about 70% against 9% in the eastern Mediterranean.
In a climate 2.8 C warmer than pre-industrial, events like this year's would run a further 1.3 C to 1.9 C hotter. The report lists mass mortality of corals, sponges and macroalgae, shifts in where species live, changes in food webs, more jellyfish and a higher risk of vibriosis, an infection caused by marine Vibrio bacteria, among the consequences. The full study is deposited at Imperial College London under DOI 10.25560/132103.
