A Decade of Hot Air

By all measures of global temperature — and we have three — Hansen’s forecast was a bust. Temperatures on the ground rose a mere 0.11º C during the decade, while temperatures of the lower atmosphere measured by satellites and weather balloons actually declined — by 0.24º C and 0.36º C, respectively.

In a recent paper in the Proceedings of the National Academy of Sciences, Hansen explains why he was wrong: the planet is getting greener and consuming carbon dioxide, the main greenhouse warming gas, at a rate far exceeding what he and the other climate modelers predicted a mere 10 years ago. In fact, the observed changes in carbon dioxide levels are below the lowest scenarios thought to be reasonable by none other than the United Nations Intergovernmental Panel on Climate Change — otherwise known as the “consensus of 2,500 scientists” that Vice President Gore is fond of marshaling in support of his position on the issue.

We could have saved a lot of time and grief if we had just listened to the “cynics” (Washingtonese for those who don’t think Washington is required for global salvation) when Hansen made his 1988 splash. They pointed out that the observed planetary warming, even back then, was far too small to support Hansen’s forecast. And, to make things worse, at least half of that warming had occurred prior to 1930, before greenhouse changes could have caused it. The lion’s share of the warming was also confined to the coldest air masses of Siberia and northwestern North America in the dead of winter, where warming from an average temperature of -40 degrees Celsius to, say, -38 degrees, is hardly a disaster.

The failing paradigm of dramatic warming was to be shored up with a great deal of intellectual effort — as is common in science. Thomas Kuhn frequently pointed out in his many studies of the evolution of scientific thought that explanations become increasingly ornate and bizarre as the disconnection between models and reality broadens.

One such artifice, championed by Hansen in a 1990 paper, was that the warming was being moderated by sulfate aerosols, another result of fossil fuel combustion that whitens the sky and reflects away the sun’s rays, thereby compensating for greenhouse warming. When he prepared testimony on this matter in 1992, the Bush administration tried to soften its stridency, as Hansen remained committed to dramatic warming in the near future. That kindled then‐​senator Al Gore, who had just published a bestseller singing Hansen’s praises. He stood on the Capitol steps with his arm around the NASA scientist, vowing to “start World War III” if anyone attempted to modify Hansen’s testimony.

In 1996 my colleague Chip Knappenberger and I noted in Nature that the sulfate hypothesis doesn’t hold up because the sulfate‐​free regions of the planet have actually cooled in the last decade, instead of warming. About the same time, Hansen concurred, publishing a paper demonstrating that sulfates have exerted no net cooling effect in the last two decades after all. That considerable change of direction pushed him into a dilemma — if sulfates weren’t responsible for the lack of warming, what was?

Undaunted, the vice president was in Kyoto a year later, pushing U.S. negotiators into approving language in a UN climate treaty that would require an astonishing 43 percent reduction in fossil fuel‐​related emissions of greenhouse gases by the year 2010, compared to the emissions we would produce if we remained on the trajectory we have been on for nearly two decades. In preparation for Kyoto, U.S. Under Secretary of State Timothy Wirth (now working for Ted Turner’s anti‐​global warming campaign) repeatedly declared that “the science is settled.”

Here’s how Hansen has settled the science. According to his PNAS paper, “Apparently the rate of uptake by carbon dioxide sinks, either the ocean, or more likely, forests and soils, has increased.” In other words, the planet is not warming because it is getting greener.

In spite of that, Hansen remains compelled to sound the alarm. While admitting that observed climate changes have been too small for anyone to notice, he proposes a “common‐​sense” government‐​sponsored index of climate change that he feels will whip up enough concern to create a political consensus to act.

In PNAS, Hansen trots out his index. Lo and behold, the only place it shows persistent greenhouse changes is in the dead of winter in Siberia and northwestern Canada, exactly where the “cynics” told him to look in 1988!

When someone like NASA’s Jim Hansen says that all of the anomalous warming is in Siberia and Nunavit, and that the planet is getting much greener and not much hotter as a result of increased carbon dioxide, it is over. The science is settled. The case is closed and the Kyoto treaty is dead, shot through the heart by the climatologist for whom Al Gore vowed to go to war.