by Mitch Kokai
Senior Political Analyst, John Locke Foundation
Climate models used by scientists to predict how much human activities will warm the planet have been over-predicting global warming for the last six decades, according to a recent working paper by climate scientists.
“Everyone by now is familiar with the ‘pause’ or ‘slowdown’ in the rate of global warming that has taken place over the past 20 years of so, but few realize is that the observed warming rate has been beneath the model mean expectation for periods extending back to the mid-20th century—60+ years,” Patrick Michaels and Chip Knappenberger, climate scientists at the libertarian Cato Institute, write in a working paper released in December.
Michaels and Knappenberger compared observed global surface temperature warming rates since 1950 to what was predicted by 108 climate models used by government climate scientists to predict how much carbon dioxide emissions will warm the planet.
What they found was the models projected much higher warming rates than actually occurred. …
… Satellite temperatures, which measure the lowest few miles of the Earth’s atmosphere, show there’s been no significant global warming for the last two decades despite rapidly rising carbon dioxide levels in the atmosphere.
The so-called “hiatus” in warming has sparked an intense debate among climate scientists over what’s caused warming to disappear. Dozens of theories have been put forward as to why global warming has stalled, but no one has cracked the case.
Michaels and Knappenberger, however, suggest the “hiatus” and the previous decades of overblown temperature predictions point to a huge flaw in climate science: the climate isn’t as sensitive to CO2 as previously thought.
The Cato scientists argue “climate sensitivity” estimates are too high and are causing climate models to over-predict how much warming will happen with increases in greenhouse gas emissions.