The end of the year celebrations were marked by very mild temperatures. A worrying sign of global warming.
The collusion of the two events would almost be a laughing matter if it weren't so tragically revealing. As the film Don’t Look Up, which criticizes widespread inaction on climate change under the guise of wacky comedy, hits the mark on Netflix, we are on the verge of barbecuing at the end of December. And no one is shocked. Exceptional and localized episode? Obvious manifestation of global warming? Could this heatstroke have long-term consequences? So many questions that deserve to be asked.
"The news is occupied by the health crisis"
The situation has enough to boil the chestnut trees. This year, no report on the Michut family, stranded on the road in Isère where they were to spend Christmas skiing, nor on Louis and Jeanne, two children who make a snowman in Colbert Square. This year, the coronavirus is taking all the space. "The news is occupied by the health crisis," said Nathalie Huret, director of the Observatory of Globe Physics in Clermont-Ferrand, interviewed by 20 Minutes.
Yes, but all the same. These abnormally mild temperatures should be of concern, right? In fact, this heat wave "does not represent an immediate risk for the citizen", which she says explains the lack of a strong reaction.
No landslide, precipitation that could overflow a river or, conversely, a dry water table, in short, nothing to move an executive in the midst of a "truce for confectioners". The event was, however, well noted by climatologists: 13 ° C in the middle of the night in Lille on Thursday, up to 29 ° C in the Pyrénées-Orientales, not to mention "rain above 1,800 m in altitude in some stations in the Alps ”, reports Nathalie Huret. An exceptionally high rain-snow limit in December, not reached "before March-April in normal times". "It is less impressive than a heat wave with two degrees more in summer, which is very serious in terms of health," confirms Robert Vautard, climatologist among the authors of the latest IPCC report, also interviewed by 20 Minutes.
Danger on agriculture
So, is this wave of gentleness just an inconsequential epiphenomenon? Not necessarily. To fully understand it, you have to explain how it came into being. "It is first of all an episode of meteorological origin," explains the one who is also director of research at the CNRS at the Pierre-Simon Laplace Institute. A mass of air from the tropical Atlantic that "did not mix", retaining its warmth. In doing so, he helped push back the “polar vortex”, abounds Nathalie Huret, blocked above the pole. "The whole weather system is blocked," she insists. A natural phenomenon, which already occurred in February 2020, but where climate change "contributes to an increase in temperatures", decrypts Robert Vautard. By boosting these temperature differences, climate change also contributes to their greater regularity, observable in statistics.
This mildness in France is not an isolated phenomenon, and it is in this that it is part of global warming, according to our two experts. But unlike a sudden flood, or even a heat wave that can lead to health actions, it is difficult to act to bring back the cold quickly. "There is a way to act, and that is to reduce greenhouse gas emissions", smiles Robert Vautard. But it's not when you let go of the pedal that the snow will fall. "It is a constant effort to stabilize the climate," he proclaims.
If it is "one more indicator" of global warming for Nathalie Huret, this wave of mildness will not be without consequences in the medium and long term. With temperatures jostled compared to normal, all biodiversity is affected. “The pollinating insects will no longer wake up in the right phase,” she explains, believing that spring has come too early, when food is scarce. Or on the contrary, it's the plants that can have the wrong timing. The flowering of certain species has already advanced by 15 days compared to the 20th century, suggests Robert Vautard. However, "plants in our latitudes need cold to develop well afterwards," he recalls, also pointing out that they expose themselves to frost by growing too early. Last year, a cold snap followed the mild March, causing losses of up to 30% of wine production. And for those who are still in T-shirts on the shores of the Mediterranean, sorry if the mood has cooled down.