The climate change crusaders, who have been at it for a quarter-century, appear to be going clinically mad. Start with the rhetorical monotony and worship of authority (“97 percent of all scientists agree!”), add the Salem witch trial-style intimidation and persecution of dissenters, and the categorical demand that debate about science or policy is over because the matter is settled, and you have the profile of a cult-like sectarianism that has descended into paranoia and reflexive bullying. Never mind the scattered and not fully suppressed findings of climate scientists that the narrative of catastrophic global warming is overstated, like nearly every previous predicted environmental apocalypse. It matters not. The recent crescendo of scary government climate reports and dutiful media alarm has paved the way for the Obama administration to throw its weight around in ways that would make Woodrow Wilson blush.
Making sense of this tiresome issue requires stepping back for the long view. If you strip away all of the noise from smaller scientific controversies that clutter the debate—arctic ice, extreme weather events, droughts, and so forth—the central issue is climate sensitivity: How much will average global temperature increase from adding a given level of greenhouse gases to the atmosphere? The most recent “official” estimate of the Intergovernmental Panel on Climate Change (IPCC), given a doubling of greenhouse gases, is a planet 1.1 to 4.8 degrees Celsius warmer a century from now. On the low end of this range—up to as much as 2 degrees—warming would be no big deal, and possibly a net benefit. Warming on the high end of this range would present significant problems, requiring a number of responses. Narrowing the range of outcomes is therefore the most pressing climate science question. Everything else is a sideshow.
It may well be that it can’t be done. Right now the IPCC can’t settle on a best-guess estimate within the 1.1‑4.8 degree range, though a number of scenarios for the year 2100 cluster around 2 degrees of warming. This is nearly the same range and best guess as the previous four reports of the IPCC stretching back to 1990. More astonishing, this range differs little from that proposed by Swedish scientist Svante Arrhenius in 1896. It was Arrhenius, winner of the Nobel Prize for chemistry in 1903, who first supplied the basic equation that forms the basis for modern climate models. Working without a computer, he estimated a range of climate sensitivity from a doubling of greenhouse gases of 1.6 to about 5 degrees Celsius, with a best guess of about 2.1 degrees.
In other words, despite billions spent on climate research and the development of enormously complex computer models, we are no closer to predictive precision than we were 110 years ago. The computer models are still too crude and limited, especially about the crucial question of water vapor “feedbacks” (clouds in ordinary language), to spit out the answers we’re looking for. We can fiddle with the models all we want, and perhaps end up with one that might produce a correct prediction, but we can never be sure so long as our understanding of water vapor behavior remains sketchy.
While climate skeptics are denounced for mentioning “uncertainty,” the terms “uncertain” and “uncertainty” appear 173 times, while “error” and “errors” appear 192 times, in the 218-page chapter on climate models in the latest IPCC report released last September. As the IPCC admits, “there remain significant errors in the model simulation of clouds. It is very likely that these errors contribute significantly to the uncertainties in estimates of cloud feedbacks and consequently in the climate change projections.” The IPCC’s latest report rates the confidence of our understanding of clouds and aerosols as “low,” and allows that it is possible that clouds could cancel out most of the warming effect of greenhouse gases. If anything, our uncertainty about future climate change has increased with each new IPCC report.