Summer 2026: record marine heat waves in Italian seas

After the record temperatures of summer, the extreme events of autumn. The first data relating to summer 2026 analyzed in 6 of the 14 marine areas involved in Greenpeace's Mare Caldo project which involves the Island of Elba and the Marine Protected Areas of Portofino, Miramare, Tremiti Islands, Plemmirio and Ustica, «selected to have a representative picture of the different sectors of the Italian seas», outline this scenario where sea warming and strong heat accumulation also play an important role.

«From May 2026 onwards, several marine heat waves occurred in all the areas considered, with peaks that in some cases exceeded the climatological average of the last 30 years by almost 5°C - underlines the research -. Last summer's sea surface temperatures were approximately 1°C higher than the previous summer, with more intense and persistent phenomena between June and August."

The highest peak was recorded on the Island of Elba, during a heat wave that lasted 68 days, which led surface temperatures to exceed the historical average by 4.95°C. High anomalies were also recorded in the Marine Protected Area of ​​Miramare in the Northern Adriatic, with +4.63°C, in the Marine Protected Area of ​​Portofino in the Ligurian Sea, with +4.36°C and in that of Ustica in the Strait of Sicily, with +4.54°C. The analysis, conducted with the scientific contribution of Riccardo Martellucci of the National Institute of Oceanography and Experimental Geophysics (OGS), integrated sea surface temperature (SST) data and model data (Med-Physics) of the Copernicus Marine Service, allowing us to describe both the evolution of surface temperatures and that along the water column.

For Antonello Pasini, climatologist physicist of the National Research Council «the summer we have just experienced was a "postcard from the future": we experienced in one season what we will be able to experience repeatedly in about twenty years». «The heat that the Mediterranean absorbs in ever-increasing quantities, unfortunately, does not remain in the sea - he underlines -. The water that evaporates fuels the formation of clouds and rain, while the energy transferred into the atmosphere contributes to making meteorological phenomena more violent, with the formation of superstorm cells, very strong winds, tornadoes or sea storms, real tornadoes, up to the so-called "Mediterranean hurricanes". These extreme phenomena will be more likely next autumn, when a still warm sea will amplify the contrast with the colder air and the disturbances arriving from higher latitudes."

And in this context there is no shortage of problems for biodiversity. «The consequences of the high temperatures recorded throughout the Mediterranean are already visible in the seabed, where the signs of thermal stress on gorgonians and corals and the presence of alien and thermophilic species are increasing - says Valentina Di Miccoli of the Greenpeace Italia sea campaign. The only solution to slow down this process is to protect marine ecosystems with protected areas and drastically reduce greenhouse gas emissions into the atmosphere that fuel the climate crisis."