Almost a fifth of the global warming that has happened during the past 150 years has been missed by historical records because of “quirks” in how temperatures have been recorded.
That’s according to a new Nasa-led study which applied these quirks to climate models. The agency then performed the same calculations on both the models and the observations to make the first true “apples-to-apples comparison of warming rates”.
The models and observations were found to largely agree on expected near-term global warming and may explain why projections of future climate, based solely on historical records, have a tendency to lower the rates of warming compared to similar predictions made using climate models.
The study, published in the journal Nature Climate Change, was led by Mark Richardson of Nasa’s Jet Propulsion Laboratory, California. Although scientists have known about these quirks for some time, this is the first study to calculate their impact.
“They’re quite small on their own, but they add up in the same direction,” Richardson said. “We were surprised that they added up to such a big effect.”