Climate: Mediterranean hit by longest heat wave of last four decades

New climate alarm for the Mediterranean, which from May 2022 to May 2023 faced the longest heat wave^[1] ever recorded in the last 40 years, with a 4°C increase in sea temperatures and peaks above 23°C mainly occurring in the western basin, as shown by the CAREHeat^[2] project -funded by the European Space Agency (ESA) and comprising ENEA and Cnr (coordinator) for Italy. The outcomes were published in the prestigious journal “Environmental Research Letters”.

CAREHeat's research activities began with the study of the heat wave based on the satellite data that first detected the thermal anomaly, which rose to much higher values than the previous 2003 heat wave. The satellite information was then supplemented with data from in situ observations provided by the Lampedusa Climate Station, the only site in Europe capable of providing information on the interactions among vegetation, the atmosphere and the ocean both in terms of carbon exchange and the processes and energy exchanges that regulate regional climate.

Furthermore, thanks to cutting-edge modeling simulations and data processing systems, it was possible to characterize the thermal anomaly. In particular, detailed investigations on the role of the so-called 'atmospheric forcings' – for instance wind affecting the ocean - showed that the onset of sea surface temperature anomalies is closely related to the prevalence of anticyclonic conditions in the atmosphere; conditions which also caused severe droughts in the Mediterranean region over the same period. Analysis of these data indicates that vertical mixing of seawater induced by wind is primarily responsible for heat transport in seawater and that these subsurface anomalies lasted for several months.

Finally, the comparison between the evolution of the 2022/23 event with the 2003 event highlighted some facts related to climate change in the region: among these, temperatures well above the seasonal average since the beginning of May and in the first half of June, which was characterized by meteorological phenomena typical of midsummer.

“The CAREheat findings show us just some of the signs of climate change but we must be aware that the global climate is projected to continue to change and those are just glimpses of what will occur increasingly frequently”, said Gianmaria Sannino, head of the ENEA Division Models and Technologies for the Reduction of Anthropic Impacts and Natural Risks. “In this context, research is and will be key to inform and guide future environmental policies, as COP28 finally established: in fact, COP28’s outcomes will inform the next round of climate action plans due by 2025, for more ambitious climate action and targeted funding.

Among the main measures envisaged at COP28, is tripling the world's renewable energy capacity and doubling energy efficiency improvements; we reached a historic milestone setting up a fund of over $700 million to support the most vulnerable countries; we have committed to reducing greenhouse gas emissions by 43% by 2030 and have finally adopted a climate adaptation framework to protect and restore our natural ecosystems and stop deforestation by 2030. Studies like CareHeat will be an inestimable resource to guide the planning of adaptation strategies,” he said.

 “In light of the conclusions reached in the recent COP28, the results of the CAREHeat project are even more significant, becoming key elements to inform and guide future environmental policies, with a strong global commitment to combat climate change and its impacts”, pointed out Ernesto Napolitano at the ENEA Climate Modeling and Impacts Laboratory.

The CAREHeat project aims at developing new methods to predict and identify heat waves and understand their propagation and impacts on the environment, biodiversity and economic activities like fishing and aquaculture. In addition to ENEA and Cnr, the French research institutes CLS (Collect Locatisation Satellites) and IFREMER (Institut Français de Recherche pour l'Exploitation de la Mer), the non-profits Mercator Ocean International (France) and +ATLANTIC CoLAB (Portugal) also participate in the project funded by ESA as part of the "flagship actions" of the European Commission.