Under the headline “UN Climate Panel Confronts Implausibly Hot Forecasts of Future Warming,” a July 27 article in Science covers the bombshell that has just hit the IPCC’s climate modelers: “Many of the world’s leading models are now projecting warming rates that most scientists, including the model makers themselves, believe are implausibly fast.”
Now, the article says, “scientists have scrambled to understand what went wrong.” Some of them are wondering how they can “turn their models into useful guidance for policymakers” – which was their supposed raison d’être in the first place! Worst of all for them, their feet are being held to the fire by Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, who said,: “It’s become clear over the last year or so that we can’t avoid this” fixing the models.
In the past, most models projected a “climate sensitivity”—the warming expected when atmospheric carbon dioxide (CO2) is doubled over preindustrial times—of between 2°C and 4.5°C. Last year, a landmark paper that largely eschewed models and instead used documented factors including ongoing warming trends calculated a likely climate sensitivity of between 2.6°C and 3.9°C. But many of the new models from leading centers showed warming of more than 5°C—uncomfortably outside these bounds.