It’s time to do your raclette on the balcony. This Friday, up to 22 degrees are expected in Montpellier, and even 24 in Perpignan. Temperatures already observed on Wednesday and Thursday, for an episode which has nothing to do with winter on the shores of the Mediterranean. And if the heat is abnormally high there, the rest of France is not left out. In Paris, temperatures jumped from 0 to 15 degrees in a few days, and “monthly records for nighttime mildness were broken in Nantes (12.8°C), Tours (12.7°C) and Niort (13°C). .1 °C),” indicates Météo-France.
But why is it suddenly so hot in the middle of winter? Can this type of episode last and multiply with global warming? What could be the consequences? 20 minutes takes stock with Christine Berne, climatologist at Météo-France.
Why is it suddenly so hot in the middle of winter?
A week ago, mittens and hats were the norm across a large part of the country. And now, today, some are going out in t-shirts. A sudden recovery of the thermometer which can be explained by a clear change in air flow. “We have a southerly flow, air coming from the Sahara, and no longer from the North Pole or the countries of Eastern Europe,” explains Christine Berne. If the establishment of this anticyclone above the Mediterranean is nothing exceptional, the temperatures that go with it “are part of a groundswell”: global warming.
“The Sahara is much warmer than a few decades ago, and it is this air that is rising towards us and warming Spain,” explains the climatologist. On the other side of the Pyrenees, temperatures even came close to 30 degrees near Valencia and in Andalusia. In France, “we reached 25 degrees locally, it is very remarkable,” notes Christine Berne. And the heat doesn’t just hit in the afternoon. “Record minimum temperatures were broken in the North-West,” she underlines. In other words, the thermometer has never dropped so little at night. “We realize it less, but it is a clear signal of global warming. »
Can this phenomenon last and multiply?
As the records show, current temperatures are “not unprecedented”. But the previous records only date from recent years. And what characterizes the current wave of “gentleness” is its duration. “We are reaching a series of days beyond the threshold of 20 degrees which is unprecedented,” points out Christine Berne. And this phenomenon could still last “around ten days”.
“These off-season episodes are becoming more and more frequent,” she adds. The month of January had already started gently. In the end, “despite a marked winter episode lasting around ten days, the month of January will still be well above normal on average,” warns the climatologist. And again, regarding the week of cold which affected France, “in an equivalent meteorological situation twenty or thirty years ago, we would have had much colder”.
What consequences can this heat wave have?
The main danger of spring temperatures setting in is that we end up really believing in it. And as trees and flowers do not keep their eyes glued to the calendar, the buds come out too early. On agroclimatologist Serge Zaka is thus worried about an “early opening of the buds of the almond tree and the apricot”, which could be crushed by the return of seasonal cold. “Nature is disoriented,” summarizes Christine Berne. The climatologist also paints a worrying picture of the state of the soil. “The Pyrénées-Orientales will still have a rainfall deficit of 80% compared to normal, which will be added to the deficit of recent months, it’s dramatic. »