Climate Change Models Got It Right

shutterhold/Adobe StockA Siberian town registered the highest temperature ever recorded in the Arctic Circle this week – 100 degrees Fahrenheit. While warm summers are typical in the Arctic, recent months have been abnormally high. And data demonstrate that the Arctic Circle is warming at about twice the rate as the rest of the globe – a fact predicted by decades-old climate models.

Earlier this year, scientists from the University of California at Berkeley, MIT and the NASA Goddard Institute for Space Studies published a ground-breaking review that demonstrates the accuracy of climate models that have predicted the warming of the globe over the past 50 years.

In the systematic review published in Geophysical Research Letters, researchers chose 17 global climate models dating from 1997 to 2007 and compared the models to observational data.  None of the models they chose are still in use because they have been replaced by more sophisticated versions. But the review found that even early climate predictions models that used far fewer variables than currently-used models have been fairly accurate in predicting climate change over time.

“The projection skill of the 1970s models is particularly impressive given the limited observational evidence of warming at the time, as the world was thought to have been cooling for the past few decades,” the authors wrote.

Scientists have demonstrated that carbon dioxide, or CO2 emissions, are a major factor contributing to global warming. Accurately modeling climate change depends on two elements: an estimation of future CO2 emissions and modeling of how those emission will impact global temperatures. Even the most robust model will yield incorrect forecasts if researchers don’t accurately predict future CO2 emissions.

The authors of the most recent review article accounted for these variables by looking at how the relationship between temperature and atmospheric CO2 differed between models and observations. They found that climate models published over the past five decades “were generally quite accurate in predicting global warming in the years after publication.” This was especially true when they looked specifically at whether the models had accurately estimated C02 emissions. (Models that predicted warmer than observed temperatures did so because their authors overestimated C02 emissions, and those that predicted lower than observed temperatures underestimated CO2 emissions.)

The take-home message: Climate forecasting over the past 50 years has proved to be surprisingly accurate – with clear evidence that increased CO2 emissions across the globe are a major contributor to global warming.

Visit Cornell University’s Bronfenbrenner Center for Translational Research’s website for more information on our work.

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