• The summer of 2022 was marked by several very intense heat waves and a critical drought, giving a first image of what daily life will be like in a world where the objective of the Paris agreement would not be respected.

  • September also started with a heat wave, before giving way to the first signs of autumn.

    But the dryness is not resorbed for as much.

  • Three climatologists answered questions from

    20 Minutes

    to give some forecasts for the fall of 2022 and imagine the fall of the future.

If the start of the school year was placed under the sign of longshoremen and heat, the month of September ends in the grayness and the frost.

No doubt: autumn is here.

But after a summer of all records, we would almost hesitate when it comes to bringing out turtlenecks and down jackets.

What if it was still mild, very mild?

“There are quite a few correlations between the seasons in meteorological terms”, tempers Robert Vautard, climatologist and author of the IPCC, interviewed by

20 Minutes

.

It is therefore not because the summer was hot that the autumn will be too, even if "on the average for the month of September, we are above normal", underlines Christine Berne, climatologist at Météo- France and author of Drias, a forecast report on the climate in France in the 21st century.

According to Météo-France's three-month forecast, there is a 50% chance that autumn temperatures will be higher than the seasonal average.

It is not only the thermometer in the air that connects the two seasons.

The sea also remains warm.

"Between Corsica and the Gulf of Lion, there is still a three degree difference from normal", notes Robert Vautard.

A heat that is slow to dissipate, and constitutes an important reservoir of energy for the famous "Mediterranean episodes" or Cévennes.

However, with the summer drought, “arid lands are no longer able to capture significant rainfall”, explains

Sabrina Speich, professor of geoscience at the ENS de Paris , to

20 Minutes .

“There are fewer signs of climate change” in autumn

The water then runs off the surface, with the risk of creating flooding and significant material damage.

“The rains will gradually allow water to be found in the different layers of the ground, but there are regions where the hydrological situation is still critical.

The drought will persist”, further warns Robert Vautard, for whom “the plant world will not repair itself in a few months”.

So much for the forecasts for this autumn, post-overheated summer.

But if we look at the longer term, what will the autumn of the future look like, in a global warming version?

"The whole year is warming up but autumn is the season that changes the least" and during which "there are fewer signals of climate change", notes Christine Berne.

According to the data that was used to create the Drias forecast report, autumn took +0.3 degrees per decade, evenly across the territory.

Conversely, summers "warm up faster in the East", and increased by 1.5 degrees between the period 1961-1990 and 1991-2020.

What reinforces the impression that the temperature drops are sometimes brutal?

The South facing more violent events

"The alternation between warm air from the Sahara and cold air from the North is more increased" according to Sabrina Speich, due to vortices that accompany the "deeper" westerly winds.

The Italian-born researcher, who notes that the temperature difference between Milan and Paris has faded in thirty years, admits that her observation is still debated.

But “what is most certain is that autumn will not be colder but more restless”.

Christine Berne confirms this at

20 Minutes

, supporting IPCC report: there will be "an increase in precipitation in the Mediterranean regions", linked "to more intense events and not to regular rains".

Still in the Mediterranean, Robert Vautard indicates that "the small cyclones called Médicanes should decrease in frequency but will see their intensity increase" too.

If these phenomena mainly affect the south of Italy or Greece, "it is not forbidden to see them in France".

On August 18, a deadly storm also devastated part of Corsica, pushing Gérald Darmanin to want to investigate a fault by Météo-France.

“Since Chirac, we have not stopped dismantling the public service.

The previous management of Météo-France closed several regional centers when it would be necessary to do just the opposite, ”denounces Sabrina Speich, who also calls for investing in research for adaptation.



On the Atlantic coasts, on the other hand, even if tropical cyclones migrate north more easily, like storm Fiona in Canada, "in general they turn into a more classic depression" before reaching Europe, reassures Robert Vautard, even if “remains of cyclones can cause damage”.

The IPCC expert also predicts “more rainy late autumns”, in agreement with Christine Berne who mentions “a more marked drought in September and October, less in November”.

Drier, a little milder and above all more agitated, especially in the South, the autumn of the future will however retain one characteristic: "the leaves will always fall", smiles Robert Vautard.

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