Even 50-year-old climate models correctly predicted global warming
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, ZekeHausfather, a graduate student at the University of California, Berkeley.
Climate scientists first began to use computers to predict future global temperatures in the early 1970s.
That’s when newfound computing power coincided with a growing realization that rising carbon dioxide levels could boost global temperatures. As the issue gained public attention,critics questioned the reliability of rudimentary model predictions. Even a 1989 news article in Science radiated skepticism, stating that “climatologists may have a gut feeling that the greenhouse effect is heating up the Earth, but they have not been close to proving it.”
Today, the models are much more sophisticated.Mainframe computers driven by paper punch cards have given way to supercomputers running trillions of calculations in 1 second.
Modern models account for myriad interactions, including ice and snow, changes in forest coverage, and cloud formation—things that early modelers could only dream of doing. But Hausfather and his colleagues still wanted to see how accurate those bygone models really were.
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 0.9°C since 1970.For 10 forecasts, there was no statistically significant difference between theiroutput and historic observations
