Droughts, fires, violent storms… In Brittany, the summer of 2022 was marked by exceptional weather events. Warning signs of inexorable climate change? Response elements with Anne-Marie Treguier and Vincent Dubreuil, co-chairs of the Breton High Council for Climate.
More and more hot days, even very hot, in summer, fewer and fewer frosty days in winter, milder springs, warmer autumns are parameters that make it possible to observe climate change in Brittany.
A slow progression marked by extreme episodes such as the drought in the summer of 2022. “In hot weather, explains Anne-Marie Treguier, co-chair of the Breton High Council for Climate, extremes, rare in the past, will become more and more frequent”.
Cette oceanographer, also directrice de recherche CNRS à Brest et co-auteur du 6e rapport du GIEC (Groupe d’experts intergouvernemental sur l’évolution du climat), rappelle que l’observation des changes ne s’opère pas en comparant une année à the previous one, “but from a perspective of decades“. An important precision if we want to take the true measure of what is happening on a planetary scale.
Who could have said that Brittany would one day experience a rainfall deficit? However, it is a reality. The phreatic levels show a low level according to a bulletin published by the Bureau of Geological and Mining Investigation (BRGM) in late August 2022. This resource decline is partly explained by a 2021-2022 winter with very little rainfall.
Take, for example, the following animated map that compares the emergency levels of the drought decrees still in force in Brittany at the end of September 2021 and 2022. It shows that the restrictive measures taken by the Breton departments have nothing to do with those from last year
Thus, as of September 20, 2022, the entire Brittany region remains on alert for “drought crisis”, while in 2021, only two departments, Morbihan and Ille-et-Vilaine, remained on alert and at the lowest threshold. , that of “surveillance”.
It should also be noted that the restrictions on water use imposed by these decrees were taken at the beginning of May when Morbihan was placed on “vigilance” alert.
This flagrant comparison over a year can only be considered as one of the indicators of the future multiplication of periods of drought announced by climatologists.
Fires devastated many forests this summer of 2022, mainly in the Gironde. By the end of August, more than 62,000 hectares had been burned across France.
And Brittany, in the midst of a drought, was not spared from the fires. In particular, Finistère, where this summer 2,588 hectares were destroyed in Monts-d’Arrée. To which are added several fires in Morbihan, in particular in the Brocéliande forest.
“For 20 years, the burned area in Brittany is quite exceptional, says Anne-Marie Treguier. The region is no longer sheltered from these phenomena that, in the past, affected the south of France more”.
According to Vincent Dubreuil, geographer and climatologist, we are witnessing what he calls “mediterraneanization” of the weather in Brittany. Like Anne-Marie Tréguier, she co-chairs the Breton High Council for Climate. This independent body, created last May, has the mission of contributing its scientific experience to public policies in the fight against climate change.
Deregulation, a term Vincent Dubreuil rarely uses. He prefers to talk about change. “of which we have a concrete manifestation in Brittany he said. For example, the number of hot days in Brest, that is, over 25 degrees, has increased on average from 6 days a year after the Second World War to 12 days a year during the last thirty years. In Rennes we go from 28 days to 45 days a year.”
Rennes is La Rochelle or Bordeaux fifty years ago in terms of temperatureVincent Dubreuil
Climatologist and co-chair of the Breton High Council for the Climate
Frost days decreased in both cities during the same period. in Brest, after the war, it froze an average of 18 days a year, compared to 14 days in the last thirty years. In Rennes, the same scenario: the number of frost days fell from 43 to 30 per year. “Rennes is La Rochelle or Bordeaux fifty years ago in terms of temperature” analyzes Vincent Dubreuil.
A planet that is warming as a result of greenhouse gas emissions produced by human activity, more intense and prolonged periods of drought, more violent and sudden rains… and a rise in sea level, slowly but surely, which causes, on the Breton coast, a retreat of the coastline and the risk of submersion.
“This is a problem identified as important in Brittany, notes Anne-Marie Treguier. Obviously, the rise in the level of the ocean is not perceptible like this. What we are going to see, for example, is a dock, flooded once every 3 or 4 years at high tide, which will be systematically flooded from now on. It’s these kinds of notable episodes that set the trend.”.
To limit and stabilize global warming by 2100, “We must move from rhetoric to action” says Vincent Dubreuil. According to the climatologist, “All the lost years will require even more effort to make up for. The sooner we act, the less abrupt the transition will be.”.