An international project group that develops climate-change scenarios used by the UN’s Intergovernmental Panel on Climate Change (IPCC) in its reports has discarded a scenario involving a 5-degree temperature increase by 2100 as unrealistic.

Since 1995, the project group Coupled Model Intercomparison Project (CMIP) has developed the scenarios in six different rounds, and it was in the fifth (CMIP5) and sixth (CMIP6) rounds, which formed the basis for the IPCC’s fifth (AR5) and sixth (AR6) assessment reports in 2013 and 2021, that a scenario called RCP8.5 predicted the sharpest increase in the world’s average temperature by the end of the present century.

RCP8.5, which was one of five highlighted scenarios in the sixth assessment report, has for many years been criticised from several quarters for lacking realism, not least because it assumes global greenhouse-gas emissions around three times higher than those at present. Nevertheless, this scenario has received extensive media coverage in the form of nightmarish descriptions of the climate of the future.

But in an article discussing the next round of climate scenarios (CMIP7), published in the scientific journal Geoscientific Model Development on 7 April, a number of researchers state that RCP8.5 is not credible in light of, among other things, recent emissions trends.

The discreet announcement has received little international media attention during these six weeks, but was mentioned on Saturday by US President Donald Trump on TruthSocial. “Good riddance,” Trump commented. He called the scenario alarmist climate nonsense used to frighten people and promote green fraud.