Global warming may reach +7°C, French scientists warn

The average global temperature could rise by as much as 7°C by 2100, scientists said

Global warming is likely to be more severe than previously predicted, with global average temperatures potentially rising by as much as 7°C by 2100, French scientists have warned.

Around 100 scientists and engineers from research centres le Centre National de la Recherche Scientifique (CNRS), le Commissariat à l'Énergie Atomique (CEA) and from forecaster Météo France issued the warning as part of work for a climate report for the UN, expected for release in 2021-22.

Researchers created two climate change models spanning 80,000 years, and then tested them via several potential scenarios. The testing required supercomputers to process 20 million billion bytes (20 petabytes) of data, running 24 hours a day for a year.

In the “worst case” - including rapid global economic growth and the continued use of fossil fuels - the report said: “...the rise in average global temperature would reach 6.5-7°C by 2100”.

This contrasts significantly with the most recent predictions from 2014 - upon which the Paris Agreement was decided - which said that the worst-case scenario would lead to a rise of 4.8°C.

The most optimistic scenario would allow temperatures to rise by just under 2°C, the report said, which appears to be inevitable now, given what it called “inertia of the climate system”. This will still only happen through “strong international cooperation, giving priority to sustainable development”,  it said.

This would “imply an immediate reduction in CO2 emissions to reach planet-wide carbon neutrality by 2060, as well as the capping of atmospheric CO2 by 10-15 billion tonnes per year by 2100”. This is currently technologically impossible.

The experts continued: “The average temperature of the planet by the end of the century therefore relies strongly on climate change policy that will be put in place now and throughout the 21st century.”

Oliver Boucher, research director at the CNRS, told news source FranceInfo that the new conclusions represent a “refinement” of the climate change modelling process, and use new models that “better represent the current climate”.

He said: “The intensity and frequency of heatwaves have risen in recent decades and this trend will continue for at least the next two decades, whatever the scenario considered.”

The Paris Agreement, which was agreed in 2015, aims to reduce global average temperature rise by less than 2°C, and by 1.5°C if possible.

But, current estimates suggest that the measures taken by the Agreement states so far will in fact lead to a rise of 3°C.

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