Intellectual hubris and measured reality

From Thirty Years On, How Well Do Global Warming Predictions Stand Up? by Pat Michaels and Ryan Maue.

In a republican democracy with built in checks and balances, it is difficult to obtain social mass behind issues which lack demonstrable impact on most people. The standard mechanism to try and build momentum is to stoke fear. The anthropogenic global climate warming (AGW) argument of the past forty years follows that model. The changes are too small and the time frames too long, the counterfactuals too many and the confounding variables are too numerous to make it easy to get people be concerned about AGW. And indeed, while statists, select environmentalists (but by no means all), particular financial interests, and others have worked hard and long, the public across the developed world remains substantially unconcerned about AGW if not outright doubtful.

While Michales and Maue are somewhat selective in their presentation, it is a useful corrective to the bulk of breathless AGW reporting which is almost always slanted, uninformed and often incorrect. As an environmentalist and a committed empiricist, I am conflicted. I believe we have grave environmental problems which need addressing but AGW is not high on that list. It sucks oxygen from environmental discussions which I think would be useful to have.

In addition, the whole AGW debate is riddled with intellectual/academic hubris. Our data records are meager, brief, sometimes suspect and our comprehension of the complex system which is climate is only a step or two away from superficial.

One of the gifts of the Enlightenment was a new discipline of looking at things empirically and as described by Popper, one of the tests of a science is the testability of its forecasts. So where do we stand with the original AGW forecasts?

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.

What about Mr. Hansen’s other claims? Outside the warming models, his only explicit claim in the testimony was that the late ’80s and ’90s would see “greater than average warming in the southeast U.S. and the Midwest.” No such spike has been measured in these regions.

As observed temperatures diverged over the years from his predictions, Mr. Hansen doubled down. In a 2007 case on auto emissions, he stated in his deposition that most of Greenland’s ice would soon melt, raising sea levels 23 feet over the course of 100 years. Subsequent research published in Nature magazine on the history of Greenland’s ice cap demonstrated this to be impossible. Much of Greenland’s surface melts every summer, meaning rapid melting might reasonably be expected to occur in a dramatically warming world. But not in the one we live in. The Nature study found only modest ice loss after 6,000 years of much warmer temperatures than human activity could ever sustain.

Several more of Mr. Hansen’s predictions can now be judged by history. Have hurricanes gotten stronger, as Mr. Hansen predicted in a 2016 study? No. Satellite data from 1970 onward shows no evidence of this in relation to global surface temperature. Have storms caused increasing amounts of damage in the U.S.? Data from the National Oceanic and Atmospheric Administration show no such increase in damage, measured as a percentage of gross domestic product. How about stronger tornadoes? The opposite may be true, as NOAA data offers some evidence of a decline. The list of what didn’t happen is long and tedious.

AGW should not be dismissed out of hand but the true test of a hypothesis is not whether it is plausible or reasonable or how much it might appeal to our normative concerns. The test is whether the forecasts match the realities.

For AGW, so far, not yet.