Thursday, June 30

Climate. Weather: cities in eastern France (much) more exposed to future heat waves

It is now certain, as has already been verified for 30 to 40 years: heat waves will be more frequent, more intense, longer in the future. But with strong disparities according to the geographical sectors.

Quite counter-intuitive results

Modeling by Météo France researchers shows rather counter-intuitive results: the greatest increases in temperature are rather expected over a large eastern half of the country, in the north as well as in the south.

From data from the Drias study the National Meteorological Research Center (CNRM, Météo France)our colleagues from Le Figaro have listed the cities that will be most affected after 2040.

The results are median data, and relate to the months most likely to experience a heat wave: June, July and August. They are based on the “medium” scenario (neither optimistic nor pessimistic), known as “RCP 4.5” – which anticipates “stabilized” CO2 emissions.

For each major French city, this made it possible to determine the number of “abnormally hot” days and nights expected for the period 2041-2070, compared to the averages recorded between 1975-2006. “Abnormally hot”, that is to say with an average temperature 5°C or more higher than normal. And even if the models relate to a “distant” period, the phenomenon will begin before.

The east is much more exposed than the west of the country

The results are as mixed as they are alarming, as shown by this graph of the 26 most affected cities, i.e. which will suffer at least 20 “abnormal” episodes, day and night combined:

> Click here if the graph is not displayed

Surprisingly enough, it is especially the eastern half of the country that will be the most affected – and by far.

In Annecy (Haute-Savoie), 27 additional abnormal events are expected (16 days, 11 nights), over a period of three months. Remember that this number is added to the abnormal episodes already observed over the period 1975-2006. The Haute-Savoie town has also declared itself in a “state of climate emergency” during a municipal council in November 2019.

The south-east of the country occupies almost the entire beginning of the “ranking: after Annecy come Lyon, Saint-Étienne, Avignon, Valence, Dijon then Chambéry.

Hardly less exposed, the big cities of the mouth of the Rhône (Arles, Nîmes, Aix-en-Provence) precede those of the north-east of the country: Mulhouse, Nancy, Metz, Strasbourg, Besançon, Colmar… all among the 25 most affected.

Surprising… but nothing more normal, according to Météo-France, which recalls that the effects of climate change will be more marked in the south and east of France.

To the west, the risk of rising waters

The overheating, in the west, will be more moderate: apart from Poitiers, Saint-Nazaire and Tours, all the major cities on the coast and inland will record “only” 6 to 19 abnormal episodes per summer.

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