Average global warming could hit 6.5° to 7.0°C by 2100, up to two degrees higher than the Intergovernmental Panel on Climate Change (IPCC)’s latest scenarios, if humanity doesn’t get its greenhouse gas emissions under control, according to new modelling by two leading research agencies in France.
“The new calculations also suggest the Paris Agreement goals of capping global warming at ‘well below’ 2.0°C, and 1.5°C if possible, will be harder to reach,” Agence France-Presse reports.
“With our two models, we see that the scenario known as SSP1 2.6—which normally allows us to stay under 2.0°C—doesn’t quite get us there,” said Olivier Boucher, senior research scientist at the Institut Pierre Simon Laplace Climate Modelling Centre in Paris.
The two new computer models released earlier this week are part of a new generation of about 30, collectively known as CMIP6, that will form the basis for the IPCC’s next assessment report, to be released in 2021. “CMIP6 clearly includes the latest modelling improvements,” said IPCC lead author and Imperial College London associate professor Joeri Rogelj, with what AFP describes as increased supercomputing power and sharper representations of weather systems, natural and man-made particles, and how clouds evolve in a warming world.
“We have better models now,” agreed Boucher. “They have better resolution, and they represent current climate trends more accurately.”
Those models show a higher “equilibrium climate sensitivity”, or ECS, indicating that atmospheric carbon dioxide warms the Earth’s surface more easily than scientists previously realized. That, in turn, gives humanity a smaller carbon budget to keep climate change under control.
While the French models were among the first released, “the most respected ones—from the United States, and Britain’s Met Office—also show a higher ECS,” Boucher said. And “a higher ECS means a greater likelihood of reaching higher levels of global warming, even with deeper emissions cuts.”
“Higher warming would allow less time to adapt and mean a greater likelihood of passing climate ‘tipping points’ such as thawing of permafrost, which would further accelerate warming,” the Met Office’s Stephen Belcher and Rowan Sutton of the UK National Centre for Atmospheric Science wrote in a blog post earlier this year.