Thirty Years On, How Well Do Global Warming Predictions Stand Up? James Hansen issued dire warnings in the summer of 1988. Today earth is only modestly warmer. By Pat Michaels and Ryan Maue
https://www.wsj.com/articles/thirty-years-on-how-well-do-global-warming-predictions-stand-up-1529623442
James E. Hansen wiped sweat from his brow. Outside it was a record-high 98 degrees on June 23, 1988, as the NASA scientist testified before the Senate Committee on Energy and Natural Resources during a prolonged heat wave, which he decided to cast as a climate event of cosmic significance. He expressed to the senators his “high degree of confidence” in “a cause-and-effect relationship between the greenhouse effect and observed warming.”
With that testimony and an accompanying paper in the Journal of Geophysical Research, Mr. Hansen lit the bonfire of the greenhouse vanities, igniting a world-wide debate that continues today about the energy structure of the entire planet. President Obama’s environmental policies were predicated on similar models of rapid, high-cost warming. But the 30th anniversary of Mr. Hansen’s predictions affords an opportunity to see how well his forecasts have done—and to reconsider environmental policy accordingly.
Mr. Hansen’s testimony described three possible scenarios for the future of carbon dioxide emissions. He called Scenario A “business as usual,” as it maintained the accelerating emissions growth typical of the 1970s and ’80s. This scenario predicted the earth would warm 1 degree Celsius by 2018. Scenario B set emissions lower, rising at the same rate today as in 1988. Mr. Hansen called this outcome the “most plausible,” and predicted it would lead to about 0.7 degree of warming by this year. He added a final projection, Scenario C, which he deemed highly unlikely: constant emissions beginning in 2000. In that forecast, temperatures would rise a few tenths of a degree before flatlining after 2000.
Thirty years of data have been collected since Mr. Hansen outlined his scenarios—enough to determine which was closest to reality. And the winner is Scenario C. Global surface temperature has not increased significantly since 2000, discounting the larger-than-usual El Niño of 2015-16. Assessed by Mr. Hansen’s model, surface temperatures are behaving as if we had capped 18 years ago the carbon-dioxide emissions responsible for the enhanced greenhouse effect. But we didn’t. And it isn’t just Mr. Hansen who got it wrong. Models devised by the United Nations Intergovernmental Panel on Climate Change have, on average, predicted about twice as much warming as has been observed since global satellite temperature monitoring began 40 years ago. CONTINUE AT SITE
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