Summer has only just begun, but intense heat waves are already hitting Europe. It stretches from Spain to Greece via Italy and Romania. The temperature peak is expected in the next few days and the European record of 48.8 degrees could even be broken. In a laconic tweet published Thursday, seen 1.7 million times, the Green MP for Paris Sandrine Rousseau was alarmed by the temperature in our Iberian neighbors: “It is 60 degrees in Spain. 60 degrees. »
Like her, many Internet users have disseminated this information, shocked. On social networks, the maddening satellite image of the European observatory Copernicus is widely relayed: we see Spain in all shades of red, even black, suggesting a suffocating climate.
On Tuesday, the temperature on the surface of the ground indeed exceeded 60 ° C in Extremadura, a region in the south-east of Spain, according to the European observatory Copernicus. And many temperature records (air) have been reached in Spain, but also in France, Switzerland or Germany. According to the European satellite, 13 of the 17 Spanish autonomous communities are currently classified as being at risk from high temperatures, some of which are at extreme risk.
However, the shock number of 60 degrees therefore refers to ground temperature, not air temperature. Which changes everything. “This corresponds to the temperature felt when touching the surface, it is different from the air temperature (up to 43 ° C on the same day)”, explains engineer Thibault Laconde on Twitter.
The surface temperature of the soil “can be 15-20°C higher than the air depending on the type of soil and its color. It has never been 60°C in Spain! notes the doctor in agroclimatology Serge Zaka.
This difference is also “fairly classic in summer”, observes François Gourand, forecaster at Météo France. “On a sunny day, the sun’s rays heat the ground tremendously, so it’s much warmer at ground level than a meter or two above. To say that it is 60 degrees is factually true, but it is not comparable to the temperatures that you and I feel outside, and on which we communicate. »
80.8°C on the ground in Iran and Mexico
Copernicus Sentinel-3 satellites accurately monitor the temperature of the Earth’s surface on a global scale. On its website, the European program emphasizes that ground temperature should not be confused with air temperature. In 2021, the world land temperature record was broken, with 80.8°C measured in Iran and Mexico.
Furthermore, satellites are less reliable than measurements taken with thermometers: “Being far from the surface of the Earth, the devices measure radiation with a resolution that is not necessarily very precise,” continues François Gourand. The calculations are much more complex. There is necessarily a margin of error, it rather gives an idea. »
For some environmental activists and meteorologists, Sandrine Rousseau’s tweet serves the cause. “Nothing better for ecologists to pass for idiots and people who exaggerate”, reacts Thomas Wagner, founder of the blog Bon Pote which deals with the ecological emergency.
Despite the torrent of reactions, Sandrine Rousseau persists: “It is therefore 60 degrees”, she wrote this Friday morning.
To date, the hottest temperature record ever recorded with a thermometer was 56.7°C in Death Valley, USA on July 10, 1913.
