A clique of stealth activists, including the former head of the National Academies of Science, claimed a high-emissions future was possible long after it had been falsified.

Climate policies saved the world from catastrophic warming, say leading climate scientists. On September 1, a consortium that produces analyses for the UN Intergovernmental Panel on Climate Change (IPCC) released new scenarios. They say the new worst-case scenario is just 3.3 degrees Celsius of warming by 2100 over pre-industrial temperatures. That’s down from 4.6 to 4.9 degrees of the last three generations of climate scenarios used by the IPCC. “Our business-as-usual projection of 3C of warming – rather than 4 or 5C – is a testament to the progress in global decarbonization over the last few decades,” wrote climate scientists Zeke Hausfather, Glen Peters, and Piers Forster back in May.

Others agreed. Chris Smith, a modeler at the International Institute for Applied Systems Analysis who helped build the new scenarios, told Carbon Brief that “back in 2010, RCP8.5 wasn’t an implausible future, we’ve now made it an implausible future.” Gavin Schmidt, the longtime director of NASA’s Goddard Institute for Space Studies, argued that scenarios shifted “in light of what we (as a society) are doing,” so that “we have already done things and so ‘business’ is no longer ‘usual.’” Robert Vautard, cochair of the IPCC working group on physical science, said the old high scenarios “assumed no climate policies,” while “there ARE now many climate policies in many countries, developed in particular with the Paris Agreement signed in 2016.”