Even 50-Year-Old Climate Models Correctly Predicted Global Warming

sciencehabit writes: Climate change doubters have a favorite target: climate models. They claim that computer simulations conducted decades ago didn’t accurately predict current warming, so the public should be wary of the predictive power of newer models. Now, the most sweeping evaluation of these older models — some half a century old — shows most of them were indeed accurate. “How much warming we are having today is pretty much right on where models have predicted,” says the study’s lead author, Zeke Hausfather, a graduate student at the University of California, Berkeley. The researchers compared annual average surface temperatures across the globe to the surface temperatures predicted in 17 forecasts. Those predictions were drawn from 14 separate computer models released between 1970 and 2001. In some cases, the studies and their computer codes were so old that the team had to extract data published in papers, using special software to gauge the exact numbers represented by points on a printed graph. Most of the models accurately predicted recent global surface temperatures, which have risen approximately 0.9C since 1970. For 10 forecasts, there was no statistically significant difference between their output and historic observations, the team reports today in Geophysical Research Letters. Seven older models missed the mark by as much as 0.1C per decade. But the accuracy of five of those forecasts improved enough to match observations when the scientists adjusted a key input to the models: how much climate-changing pollution humans have emitted over the years.