The thermometer has not finished panicking. Global temperatures could rise about 7 ° C compared to the pre-industrial period by the end of the century, according to the findings of new French climate simulations released Tuesday, September 17.
Admittedly, this is the worst-case scenario envisaged by researchers from the CNRS, Météo France and the Atomic Energy Commission (CEA). "We have established eight scenarios with variations ranging from a rise of less than 2 ° C to a forecast of + 7 ° C. But overall, our simulations indicate that the climate will heat up more than what was planned seven years ago, "says Olivier Boucher, researcher at the CNRS and head of the climate modeling center of the Pierre-Simon Laplace Institute, contacted by France 24.
Model the weather every 15 minutes throughout the 21st century
The report is the result of a collaboration within the Climeri-France platform. The French work is part of an international effort to update the 2012 climate forecast models. The Hexagon is one of the countries that is trying to improve and refine the previous simulations that predicted, at worst , on a warming of 4.8 ° C by 2100. But Climeri-France is the first of the 30 modeling centers in the world to have published its results. All this work will be compared and compiled to feed the sixth report of the Intergovernmental Panel on Climate Change (IPCC), expected for 2021.
"The models used are more and more realistic. We were able to refine the simulation parameters and increase the resolution by bringing the geographical points closer to the modeling grid ", explains Olivier Boucher. French researchers have been able to model the weather every 15 minutes over the entire 21st century all over the world, with geographic points separated by 150 km from each other.
A long-term job that required running full-speed supercomputers day and night, 7 days out of 7, for three years.
The researchers were also able, for the first time, to integrate the socio-economic context to develop their scenarios. "That is to say that we take into account the types of future population: worlds where we are more or less concerned about the environment, where the level of international cooperation to fight against global warming varies", explains Olivier Boucher.
More heat waves
This global approach allows French researchers to demonstrate, once again, how "the average temperature of the planet depends on climate policies that will be implemented now". Thus, the most pessimistic scenario relies heavily on a climatic "je m'en-foutisme" of the leaders, who would do little or nothing to prevent the world from continuing to fuel fossil fuels without restraint.
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On the other hand, to remain under the objective of a temperature increase of 2 ° C, set by the Paris agreement of 2015, it would be necessary to set up "voluntarist policies with profound changes in our way of life very quickly" , assures Olivier Boucher. It is essentially to proceed as quickly as possible to a "decarbonization of the electrical system", that is to say to forget the coal, gas or fuel oil. "Behavioral factors - such as diet, lower consumption or reducing the rise in demography - are also becoming more important in these 'low' scenarios," explains the CNRS researcher.
But this expert thinks that these two extreme scenarios are not the most credible. The international community seems to have already become aware of the dangers of an unrestrained exploitation of fossil resources, while the efforts required to remain in the nails of the objective of the Paris Agreement would have a very high social cost. , with a sharp rise in unemployment, in particular, says Olivier Boucher.
These new simulations demonstrate to what extent the commitments to reduce greenhouse gas emissions made by states under the Paris Agreement are insufficient. "They will lead to a rise of 4 ° C compared to the pre-industrial era," says Olivier Boucher.
Researchers did not just simulate globally. They also studied regional and even local climate changes. In particular, they looked at the French case to conclude that episodes of heat waves would - in all cases - intensify for at least twenty years. The temperatures of the day will be warmer, the heat waves will last longer and will occur more often. But in the most "low" scenarios, "the severity of heat waves may be limited after 2050," write the authors of the report. In the other scenarios, on the other hand, a typical summer of the 2050s will correspond to that of 2003, which has remained in the annals as one of the most scorching in Europe. It had caused the death of about 70,000 people on the Old Continent.