Javier Lillo Ramos
Honorary collaborator of the consolidated research group on Terrestrial Global Change and Environmental Geology at Rey Juan Carlos University.
This work, developed by researchers from Switzerland, Sweden, the United States, Ireland, and the United Kingdom, contributes to the understanding of the effects of the 2026 heatwaves on European marine waters. Record sea surface temperatures (SSTs) were recorded in the Atlantic and the western Mediterranean in July of this year.
Marine heatwaves (MHWs), defined as sustained periods of abnormally high ocean temperatures, have become much more likely, intense, and prolonged as a consequence of global warming. In addition to the climatic impacts they cause (warmer air and more water vapor in the atmosphere, and therefore a greater likelihood of extreme precipitation events such as cut-off lows), these phenomena have severe and persistent effects on marine ecosystems, amplifying those already caused by the overall climate trend.
Using interpolated optimum sea surface temperature (OISST) time series data (the NOAA—U.S. National Oceanic and Atmospheric Administration—OISST database is a long-term climate data record incorporating observations from various instruments such as satellites, ships, buoys, and floats), the effects of heat waves have been studied in four European maritime zones (two Atlantic and two Mediterranean):
• Celtic Region: Irish Sea, St. George's Channel, Celtic Sea, English Channel, Bristol Channel, inland seas off the west coast of Scotland, and an oceanic extension to the west.
• Bay of Biscay and Iberian Peninsula (BIP).
• Western Mediterranean: includes the Alboran Sea, Balearic Sea, Ligurian Sea, and Tyrrhenian Sea.
• Eastern Mediterranean: includes the Adriatic, Ionian, and Aegean Seas.
The magnitude of the recorded annual warming varies between 1.2°C in the Celtic region, 1.5°C in the BIP region, 2.6°C in the Eastern Mediterranean, and 3.1°C in the Western Mediterranean. Thus, the thermal evolution in these four regions differs, with the warming of the sea surface being more pronounced in the Mediterranean area (where there is an increase well above the average global warming), and even more so in the Western Mediterranean. One of the most relevant conclusions is that, except in the Celtic region, the observed warming is greater than that simulated by climate models. Even using conservative estimates, the warming attributable to human activity is around 2°C in both Mediterranean sectors. Moreover, future projections for these heat waves, in line with the estimated global trend, indicate that they will be warmer.