These preliminary readings come from satellite data from the European Copernicus Observatory dating back to 1982.
For two successive summers, the Mediterranean Sea will have been warmer than during the extraordinary heatwave of the summer of 2003, when the daily median was measured at 28.25°C on August 23, a previous record that stood for for twenty years.
The long period
Today, “what is remarkable is not so much reaching a maximum on a given day as observing a long period of such high temperatures, even without breaking a record,” commented Justino Martinez. “Since 2022, surface temperatures have been anomalously high for a long time, even when considering the context of climate change.”
The record level of 2023 is, however, reached this year “more than two weeks later and surface temperatures usually decrease from the end of August”, tempers the scientist.
Copernicus provides water temperature forecasts
Copernicus
Locally, waters above 30°C have been recorded since early August, notably at one buoy off the coast of Monaco, another in Corsica and just off Valencia in Spain. “The hot sea in Campania”, the region of Naples, headlines the daily newspaper La Repubblica on Tuesday.
The Mediterranean region, hit in July, as in 2023, by several heat waves and violent forest fires in Greece, has long been classified as “very hot” of climate change by the Intergovernmental Panel on Climate Change (IPCC) of the US Nations .
Blue crabs and fire worms
“Since the 1980s, there has been a drastic change in Mediterranean marine ecosystems, with both a decline in biodiversity and the emergence of invasive species,” the IPCC indicates.
During marine heat waves between 2015 and 2019 in the Mediterranean, about fifty species (corals, gorgonians, sea urchins, molluscs, bivalves, posidonia, etc.) experienced massive mortalities between the surface and 45 meters deep, according to a study published in July. 2022 in the journal Global Change Biology.
Exotic tropical species are taking advantage of rising temperatures, such as the blue crab that is devastating shellfish farms in the Po Delta in northern Italy.
In Sicily or Calabria, fishermen notice in their nets an increase in fish devoured by fireworms, voracious predators favored by the heat of the water.
+1.2 degrees in 40 years
The average temperature of the Mediterranean has risen by about 1.2 degrees over the past 40 years, according to Federico Betti, an invasive species expert at the University of Genoa.
In the scenario of global warming greater than 1.5°C from the pre-industrial era, more than 20% of fish and invertebrates exploited in the eastern Mediterranean could disappear locally by 2060, and fishing income could decrease by up to 30% by 2050, warns the IPCC. experts. On average, the world is already considered to be about 1.2 °C warmer.
Hot air and Mediterranean episodes
In Nice, the water has been 3 or 4 degrees above normal since July 15, which prevents the air from cooling at night and leaves the population without respite between two often scorching days.