“This represents an increase up to 50% higher than previous forecasts,” said one of the authors of the study Aurélien Ribes, climatologist at the National Center for Meteorological Research (CNRM).

In the worst-case scenario, where we continue to have massive use of fossil fuels (oil, gas, coal), average temperatures could rise by 6.7 degrees, warns the study published in early October in the journal “Earth Systems Dynamics”. In the best case, the temperature increase would be 2.3°C.

But, overall, “France would warm up more (about 20%) than the planetary average”, indicates Mr. Ribes, with an average increase of 0.36 degrees per decade.

According to the UN, global warming could, if nothing is done, reach 2.7 degrees by the end of the century.

– 1.8 degrees in 2023 –

To arrive at these data concerning France, researchers from the CNRS, the CNRM, and the European Center for Research and Advanced Training in Scientific Computing (Cerfacs) based themselves on data collected since 1899 by around thirty meteorological stations distributed in France to calculate current and future warming, from different scenarios, from the most optimistic, where carbon neutrality is achieved in 2050 after major efforts at the international level, to the most pessimistic, where emissions continue to climb.

These data showed that the average temperature of France today was 1.66 degrees higher than the period 1900-1930. “Almost all of which (1.63 degrees) are due solely to human activities”, underlines Mr. Ribes.

“Each tonne of CO2 counts insofar as global warming depends on the cumulative level of emissions”, he adds, adding that “for 2023, we would already reach 1.8 degrees”.

The latest report from UN climate experts (IPCC) has shown that the planet has already gained an average of nearly 1.2°C since the pre-industrial era due to greenhouse gases generated by these human activities. .

– “Much stronger” –

But beware, the rise of 3.8 degrees in 2100 in France is only an average, warn the researchers: certain regions, particularly around the Mediterranean arc or in the mountains, could experience even higher temperatures.

And the warming would vary greatly depending on the season. If in winter, the rise in temperatures would be 3.2°C (2.3 to 4.2°C depending on the region), in summer, the thermometer could panic, with an average rise of 5.1 degrees ( 3.6 to 6.6°C depending on the region).

“This would mean that we would have extreme phenomena (heat, drought, floods, etc.) much stronger than what we experienced in the summer of 2022, when the warming was only 4 degrees on average” , underlines Julien Boé, researcher in climatology at the CNRS.

They will also be more frequent and above all more intense, notes Mr. Ribes.

According to Météo-France, in a scenario of 4° warming, heat waves in Ile-de-France, for example, would last from 21 to 94 days depending on the region, compared to seven today on the national average, and the frequency of these events is expected to double by 2050.

And, according to the IPCC, each additional degree of warming is equivalent to a 7% increase in precipitation during storms and thunderstorms.

In any case, this warming will have “consequences on ecosystems and biodiversity, with habitats that will become less favorable to certain species, which would be forced to move, and also on the agricultural system” with the abandonment of certain crops. , lack of water or a change in harvest cycles, explains Mr. Boé.

Only small positive point: “We are at the time when global warming is increasing the fastest” due to the drop in aerosols (which have a cooling effect), which is set to slow down, concomitant with the increase in greenhouse gases ( that warm).

“The rate of increase should therefore slow down after 2030,” said Mr. Ribes. But even so, if nothing changes, we will not escape 3.8 degrees.