SOURCE: Phys.org

DATE: September 17, 2019

SNIP: Greenhouse gases thrust into the atmosphere mainly by burning fossil fuels are warming Earth’s surface more quickly than previously understood, according to new climate models set to replace those used in current UN projections, scientists said Tuesday.

By 2100, average temperatures could rise 7.0 degrees Celsius above pre-industrial levels if carbon emissions continue unabated, separate models from two leading research centres in France showed.

That is up to two degrees higher than the equivalent scenario in the Intergovernmental Panel for Climate Change’s (IPCC) 2014 benchmark 5th Assessment Report.

A new generation of 30-odd climate models known collectively as CMIP6—including the two unveiled Tuesday—will underpin the IPCC’s next major report in 2021.

These include 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,” said Olivier Boucher, head of the Institute Pierre Simon Laplace Climate Modelling Centre in Paris. “They have better resolution, and they represent current climate trends more accurately.”

A core finding of the new models is that increased levels of CO2 in the atmosphere will warm Earth’s surface more—and more easily—than earlier calculations had suggested.

If confirmed, this higher “equilibrium climate sensitivity”, or ECS, means humanity’s carbon budget—our total emissions allowance—is likely to shrink.

The French models are the first to be released. But other models developed independently have come to the same unsettling conclusion, Boucher confirmed.

“The most respected ones—from the United States, and Britain’s Met Office—also show a higher ECS” than the previous generation of models, he said.