Climate Models Are Running Red Hot, and Scientists Don't Know Why

The model run by NCAR, one of American’s main climate-science institutions, started producing unusual data last year while trying to reproduce the recent past. “We got some really strange results,” Gettelman said.

The scientists went on to try 300 configurations of rain, pollution, and heat flows—something they can do as gods of their own digital earth—before matching the model to history. But by solving that puzzle, Gettelman’s team sent future projections upward at an unheard-of rate. NCAR found that CO₂ doubling would lead to 5.3°C world, a 33% jump from the model’s past reading on global warming.

Soon there were multiple teams at other institutions putting out new climate-sensitivity numbers that looked like worst-case scenarios on steroids. The Met Office Hadley Center, the U.K.’s main research group, found a doubling of CO₂ would deliver 5.5°C warming. A team at the U.S. Department of Energy ended up with 5.3°C, and the Canadian model topped out at 5.6°C. France’s National Center for Meteorological Research saw its estimate jump to 4.9°C from 3.3°C.