Don't Worry, Be Happy?

Richard S. Lindzen has a long piece in Newsweek International April 16, 2007 issue. I mostly disagree.

Judging from the media in recent months, the debate over global warming is now over. There has been a net warming of the earth over the last century and a half, and our greenhouse gas emissions are contributing at some level. Both of these statements are almost certainly true.

So far, this is firmly in the reality based mainstream. It's a useful starting point for a dialog, if there is one.

What of it? Recently many people have said that the earth is facing a crisis requiring urgent action. This statement has nothing to do with science. There is no compelling evidence that the warming trend we've seen will amount to anything close to catastrophe.

Lindzen says this has nothing to do with science, but I don't agree. The question is whether there is evidence that the warming trend produced by the greenhouse gases "will amount to something close to a catastrophe." That is a scientific question. If Lindzen is right, and the evidence for catastrophe is weak, then it's too early to take urgent and disruptive action. The question is, how strong is the evidence? It's completely disingenuous to claim that the question of the strength of the evidence is not "a scientific question."

What most commentators—and many scientists—seem to miss is that the only thing we can say with certainly about climate is that it changes.

This is pure BS. The fact is that the climate models have shown some skill, and that skill is increasing.

The earth is always warming or cooling by as much as a few tenths of a degree a year; periods of constant average temperatures are rare. Looking back on the earth's climate history, it's apparent that there's no such thing as an optimal temperature—a climate at which everything is just right.

This is an important point, but I think most scientists are well aware of it. Commentators, maybe not so much.

The current alarm rests on the false assumption not only that we live in a perfect world, temperaturewise, but also that our warming forecasts for the year 2040 are somehow more reliable than the weatherman's forecast for next week.

No, on both counts. The alarm rests on the prospect that a large and rapid change in average temperature could be profoundly disruptive to people, economies, and ecological systems. The reasons weather forecasts for next week are problematic are understood in a general sense, and are known to be related to the same causes that make detailed prediction of a turbulent system impossible even while statistical prediction can be quite good. The same considerations apply to climate models for 2040 - we certainly can't predict the detailed weather anywhere for that particular year, but there is reason to believe that statistical predictions can be made. That's probably the reason that Lindzen, and other skeptics, refuse to bet on future climates except for absurd odds.

Many of the most alarming studies rely on long-range predictions using inherently untrustworthy climate models, similar to those that cannot accurately forecast the weather a week from now. Interpretations of these studies rarely consider that the impact of carbon on temperature goes down—not up—the more carbon accumulates in the atmosphere. Even if emissions were the sole cause of the recent temperature rise—a dubious proposition—future increases wouldn't be as steep as the climb in emissions.

This is a blatant distortion. The models very explicitly take into account the dependence of the "impact of carbon on temperature" effect as a function of concentration. It also incorporates his other favorite distortion of implying that making detailed predictions about specific future dates is the same as making statistical predictions about a future with a very different thermal forcing. It's not true, and it's been demonstrated in a hundred contexts in fluid dynamics.

Indeed, one overlooked mystery is why temperatures are not already higher. Various models predict that a doubling of CO2 in the atmosphere will raise the world's average temperature by as little as 1.5 degrees Celsius or as much as 4.5 degrees. The important thing about doubled CO2 (or any other greenhouse gas) is its "forcing"—its contribution to warming. At present, the greenhouse forcing is already about three-quarters of what one would get from a doubling of CO2. But average temperatures rose only about 0.6 degrees since the beginning of the industrial era, and the change hasn't been uniform—warming has largely occurred during the periods from 1919 to 1940 and from 1976 to 1998, with cooling in between. Researchers have been unable to explain this discrepancy.

Here he makes a reasonable point, which he will promptly undercut in his next paragraph. It's true that net warming to date seems to have been underpredicted, but it's also true that models predict that we are far from seeing the full effect of the warming to date. Moreover, everyone concedes that any anthropogenic effect is supperposed on a large natural variability.

Modelers claim to have simulated the warming and cooling that occurred before 1976 by choosing among various guesses as to what effect poorly observed volcanoes and unmeasured output from the sun have had. These factors, they claim, don't explain the warming of about 0.4 degrees C between 1976 and 1998. Climate modelers assume the cause must be greenhouse-gas emissions because they have no other explanation. This is a poor substitute for evidence, and simulation hardly constitutes explanation. Ten years ago climate modelers also couldn't account for the warming that occurred from about 1050 to 1300. They tried to expunge the medieval warm period from the observational record—an effort that is now generally discredited. The models have also severely underestimated short-term variability El Niño and the Intraseasonal Oscillation. Such phenomena illustrate the ability of the complex and turbulent climate system to vary significantly with no external cause whatever, and to do so over many years, even centuries.

Climate models are improving. In previous outings Lindzen claimed warming stoppen in 1986 - an error which was based on old and erroneous data. Eli Rabett has the story here and in other recent posts.

Is there any point in pretending that CO2 increases will be catastrophic? Or could they be modest and on balance beneficial? India has warmed during the second half of the 20th century, and agricultural output has increased greatly. Infectious diseases like malaria are a matter not so much of temperature as poverty and public-health policies (like eliminating DDT). Exposure to cold is generally found to be both more dangerous and less comfortable.

The pretense is that they won't be severe. This is not an impossible result, but it is becoming increasingly unlikely. It's likely that some may benefit from global warming, at least in the short run. Subequatorial Africa, the Western United States, and quite possibly much of Souther Asia could be big losers.

Moreover, actions taken thus far to reduce emissions have already had negative consequences without improving our ability to adapt to climate change. An emphasis on ethanol, for instance, has led to angry protests against corn-price increases in Mexico, and forest clearing and habitat destruction in Southeast Asia. Carbon caps are likely to lead to increased prices, as well as corruption associated with permit trading. (Enron was a leading lobbyist for Kyoto because it had hoped to capitalize on emissions trading.) The alleged solutions have more potential for catastrophe than the putative problem. The conclusion of the late climate scientist Roger Revelle—Al Gore's supposed mentor—is worth pondering: the evidence for global warming thus far doesn't warrant any action unless it is justifiable on grounds that have nothing to do with climate.

Roger Revelle has been dead for sixteen years. The evidence of 1991 is not the evidence of today. Blaming ethanol for forest clearing and habitat destruction is a stretch, but I'm no ethanol fan. Our situation is that action may be costly, but inaction seems likely to be very costly.

Lindzen is still a smart guy, but he seems to have lost touch with both the methodology and the data. His predictions about climate haven't proven out, and he's now retreated to ideology - and though it's not evident here - insults.

Lindzen is the Alfred P. Sloan Professor of Meteorology at the Massachusetts Institute of Technology. His research has always been funded exclusively by the U.S. government. He receives no funding from any energy companies.

© 2007 Newsweek, Inc.


Popular posts from this blog

The Worst

Quora: Why Are Physicists So Smart?