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According to simulations prepared by Météo-France, the Commissariat for Atomic Energy and Alternative Energies (CEA) and the CNRS, temperatures could increase by 7 degrees by 2100 if nothing is done to reduce gas emissions Greenhouse effect.
Never has climatic prediction been so precise, never has the magnitude of the task that remains to be accomplished to avoid the worst has appeared so consistent. Météo-France, the Atomic Energy Commission (CEA) and the CNRS have posted a hundred experts from all fields of climate science to model what the climate holds until 2100.
For this, they refined their models and ran the supercomputers days and nights for a year. The result is a total of 20 petabytes of data, describing eight possible scenarios across multiple geographic areas. Among these possible trajectories, there is that called business as usual : if no concrete action to limit greenhouse gas emissions is implemented, coupled with economic development comparable to today, global warming could increase by 7 degrees compared to the pre-industrial era.
Only one scenario in line with the commitments of the Paris Agreement
Our planet has already experienced warming episodes, as at the end of the Ice Age. It had then gained four degrees, but it had taken 10,000 years. An evolution like the one described in this report would have far more disastrous consequences. The episodes of heat wave that we describe as "extremes" today will be the norm in 2070. Arctic sea ice will no longer exist in summer, the Mediterranean rim will dry up, rainfall will be much higher in the tropics .
Of the eight scenarios, only one is in line with the commitments made at the signing of the Paris Agreement, namely a warming of only 1.5 degrees. But it will require substantial effort and unwavering international cooperation. It will indeed start now to drastically reduce our greenhouse gas emissions and achieve global carbon neutrality by 2060.
A more pessimistic study than the previous ones
This new study is more pessimistic than the previous ones. These last go back to 2012, and the models have been improved since. They thus make it possible to better simulate the climate response to an excess of CO2 in the atmosphere and the consequences that result from it: a warmer world is for example more humid and water vapor also acts as a greenhouse gas. These mechanisms are thus better understood than before and their better integration into the models makes it possible to obtain these results.
All this work, as well as that provided by a hundred or so other centers around the world, will greatly contribute to the next IPCC assessment report. Its first installment will be published in 2021. In the meantime, all these data are free and open for the community to analyze and review, to further improve their accuracy.