Climate. Summer 2022, a marker of global warming? “We are witnessing a Mediterraneanization of Brittany”

Drought, fires, violent storms… In Brittany, the summer of 2022 was marked by exceptional weather phenomena. Signals that warn of inexorable climate change? Elements of response with Anne-Marie Treguier and Vincent Dubreuil, co-presidents of the Breton High Council for the climate.

More and more hot days, even very hot, in summer, fewer and fewer days of frost in winter, milder springs, warmer autumns are all 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 a warming climate, explains Anne-Marie Treguier, co-president of the Breton High Council for the Climate, extremes, rare in the past, will become more and more frequent”.

This oceanographer, also CNRS research director in Brest and co-author of the 6th report of the IPCC (Intergovernmental Panel on Climate Change), reminds us that the observation of changes does not take place by comparing one year to the previous, “but from a decades-long perspective“. 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? It is however a reality. Groundwater levels are at a low level according to a bulletin published by the Bureau of Geological and Mining Research (BRGM) at the end of August 2022. This decrease in the resource is partly explained by a very little rainy winter 2021-2022.

Take, for example, the animated map below comparing 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 do with those of last year.

Thus, as of September 20, 2022, the entire Brittany region remains on “drought crisis” alert, whereas in 2021, only two departments, Morbihan and Ille-et-Vilaine, were still on alert and at the lowest of the thresholds, that of “vigilance”.

It should also be noted that the restrictions on the use of water imposed by these decrees were taken at the beginning of May when Morbihan was placed on “vigilance” alert.

This blatant comparison over one year can only be considered as one of the indices of the future multiplication of periods of drought announced by climatologists.

Fires ravaged many forests this summer 2022, mainly in Gironde. At the end of August, more than 62,000 hectares had burned across France.

And Brittany, in the midst of a drought, was not spared by the fires. In particular Finistère where 2,588 hectares were destroyed in the Monts-d’Arrée this summer. To which are added several fires in Morbihan, in particular in the forest of Brocéliande.

“Over 20 years, the area burned in Brittany is quite exceptional,
relates Anne-Marie Treguier. The region is no longer sheltered from these phenomena which, in the past, affected more the south of France”.

According to Vincent Dubreuil, geographer and climatologist, we are witnessing what he calls “Mediterraneanization” of the climate in Brittany. Like Anne-Marie Tréguier, he co-chairs the Breton High Council for the Climate. This independent body, set up last May, has the mission of contributing its scientific expertise to public policies in the fight against climate change.

Déregulation, a term that 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, namely more than 25 degrees, has increased on average from 6 days per year after the Second World War to 12 days per year over the past thirty years. In Rennes, we went from 28 days to 45 days a year”.

Rennes is La Rochelle or Bordeaux fifty years ago in terms of temperature

Vincent Dubreuil

Climatologist and co-president of the Breton High Council for the Climate

Frost days decreased in both cities over the same period. In Brest, after the war, it froze on average 18 days a year, compared to 14 days for the past 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 up as a result of greenhouse gas emissions produced by human activity, more intense and prolonged periods of drought, more violent and sudden rains… and rising sea levels, slowly but surely, resulting, on the Breton coast, in a retreat of the coastline and the risk of submersion.

“This is a problem identified as major in Brittany, notes Anne-Marie Treguier. Obviously, the rise in the level of the ocean is not perceptible like that. What we are going to perceive, for example, is a quay, flooded once every 3 or 4 years at the time of a high tide, which will be systematically flooded from now on. It’s these kinds of remarkable 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 them. The sooner we act, the less abrupt the transition will be”.

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