They did not expect this result. Using a new method to assess global warming, scientists from Météo France and CNRS have calculated that it could lead to an increase in the average temperature in mainland France. 3.8°C in 2100. “Compared to previous estimates, this represents an upward revision of up to 50%.“, explains Aurélien Ribes, lead author of the study. Before summarizing: “Recent observations suggest that France has warmed and will continue to warm more, and faster than previously thought.”
Their work, published on October 4 in the journal Earth System Dynamics (in English)are a variation, on the scale of France, of the new approach used by the Intergovernmental Panel on Climate Change (IPCC) in its last report of 2021. This method consists of using observations – temperature readings taken in recent years – for “reduce the uncertainty of future predictions”, explains Christophe Cassou, climatologist and co-author of the IPCC, who did not participate in the study. Thanks to this method, the scientists were able to confirm the warming already observed in France (+1.7°C), which is higher than the world average (+1.1°C). They were also able to obtain more accurate and reliable forecasts for the future.
The figure of 3.8°C, put forward by the authors of the study, corresponds to an emissions scenario “intermediate”. That is to say a world where greenhouse gas emissions generated by human activities, via the combustion of fossil fuels (coal, oil, gas) and deforestation, have decreased. But not enough to respect the Paris agreement: +2.7°C instead of the objectives of 1.5°C and 2°C.
“This is the trend scenario towards which we are heading with the policies currently on the table”, analyzes Christophe Cassou. Before warning: “That means not going back on it, which is not won at all. We can see very well that it’s a bit fragile in the current context of energy tensions.” If greenhouse gas emissions continue to increase, the average temperature in France could rise by 5.6°C, or even 6.7°C in a disaster scenario now considered implausible.
It is difficult to imagine what these 3.8°C rise in temperatures mean. This is an average increase, which will be more marked in summer (+5.1°C) than in winter (+3.2°C). By way of comparison, the particularly hot summer of 2022 was 4°C warmer than normal, underlines Aurélien Ribes.
In 2100, it will therefore be warmer on average during the summer season than this year. And “a slightly hot summer in the future will be very much above what we have experienced, not to mention an extreme summer”, notes Aurélien Ribes, mentioning the possibility of summers at +7°C. This increase in temperature will also result in an increase in the intensity of extreme events (heat wave, drought, etc.). “With the internal variability of the climate, which oscillates between +1°C and -1°C, this threshold will be reached before 2100”warns Christophe Cassou, insisting on the need to adapt our societies to this burning future.
These worrying results are a reminder of the need to quickly reduce our greenhouse gas emissions to limit the damage. “Global warming is proportional to the cumulative emissions of greenhouse gases, this is valid on a global scale, as in France. Each ton of CO2 counts”, recalls Aurélien Ribes. In France, these emissions – mainly generated by transport (31%), agriculture (19%) and industry (19%) – have been falling in recent years, but at a largely insufficient rate, as reminded the High Council for the Climate in June.