One more alarming element against climate change. The surface of the oceans has just experienced its hottest month of May ever recorded, the European service Copernicus said on Wednesday June 7, after a record month of April. A more worrying trend than ever as World Oceans Day takes place this Thursday, June 8.
"Ocean surface temperatures are already at record highs and our data indicates that the average temperature for all ice-free seas in May 2023 was warmer than any other May," said Samantha Burgess, Director deputy of the European service Copernicus on climate change (C3S).
The latter is based on computer analyzes generated from billions of measurements from satellites but also from ships, planes or weather stations around the world. The data used by Copernicus goes back for some until 1950 but for the majority to 1979.
The average temperature at the surface of the oceans (still excluding areas covered by ice) in May "was approximately 19.7°C, or 0.26°C above the 1991-2020 average", specified to Agence France-Presse a spokesperson for Copernicus. The ocean, like a sponge, has absorbed about 90% of the increase in heat caused by human activities.
Its warming is causing "unprecedented cascading effects", the UN points out, such as melting ice, rising sea levels, ocean heat waves and ocean acidification. The capacity to absorb CO2 is also decreasing, whereas today the ocean absorbs 25% of all carbon dioxide emissions.
For temperatures across the globe, May was the second hottest month on record. "May 2023 was the second warmest globally as we see the El Niño signal continuing to emerge in the equatorial Pacific," added Samantha Burgess. El Niño is a natural weather phenomenon generally associated with increased temperatures, increased drought in some parts of the world and heavy rains in others.
It last occurred in 2018-2019 and gave way to a particularly long episode of almost three years of La Niña, which causes opposite effects and in particular a drop in temperatures.
In early May, the World Meteorological Organization (WMO) estimated that there was a 60% chance of El Niño developing by the end of July and 80% by the end of September. The surface of the seas (excluding polar waters) broke its annual temperature record in April, according to data from the American observatory NOAA published in early May.