Global warming smokescreen

Global warming smokescreen
May 1, 2000

Anyone who follows the history of global warming science vs. climate reality ought to keep a copy of the late Thomas Kuhn’s 1962 classic, The Structure of Scientific Revolutions, as a guidebook.

Kuhn’s notion is that virtually all scientists work within “paradigms,” or belief structures, “mopping up” (in his words) the inconsistencies that eventually evolve between the structure and reality. Sometimes, however, large anomalies appear that damage the central principals of the paradigm. In that case, Kuhn notes, scientists first ignore the problem, and then once they find it exists, attempt increasingly ornate, bizarre, and inconsistent explanations.

If there is one paradigm dominating the study of climate change today, it is that we are capable of producing climate models that are (in the words of the 1990 U.N. Intergovernmental Panel on Climate Change, the so-called “consensus of scientists”) “generally realistic” pictures of the way climate is altered by human additions to the greenhouse effect.

As Environment & Climate News reported last issue, the new National Academy of Sciences report on the discrepancy between ground-based vs. satellite and balloon-measured temperatures makes clear that a new consensus of scientists has now come to the stage of recognizing something is wrong. As the NAS stated, “. . . the discrepancy between global mean trends in temperature is not simply a matter of deciding which of them is correct. . . . It will require major advances in our ability to interpret and model the subtle variations in the vertical temperature profile of the lower atmosphere . . . due to human activities.”

If he were alive today, Kuhn would predict that some pretty strange explanation was waiting in the wings. And indeed that explanation may have just been published by Lawrence Livermore National Laboratory’s Ben Santer, Tom Wigley of the National Center for Atmospheric Research, and 11 others: “Interpreting Differential Temperature Trends in the Surface and Lower Troposphere” in the February 18 issue of Science.

Santer and his coauthors claim climate models do in fact explain the difference between the surface, weather balloon, and satellite records through 1998 by factoring in the big Mt. Pinatubo volcano that blew up in 1991. Pinatubo cooled surface temperatures quite handsomely through 1994.

But something is missing here. Another big volcano, El Chichón, went off in 1982, near the beginning of the satellite record. It is generally thought to have had about half of the cooling effect of Mt. Pinatubo, at least according to satellite guru John Christy. If we factor that effect in, the difference between the surface and the upper levels remains large.

Although they happily included Mt. Pinatubo, which supports their argument, Santer and colleagues admit they explicitly ignored El Chichón, which counters it. Their analysis, they write, “neglects other forcings that may be important to the understanding of remaining discrepancies between modeled and observed atmospheric temperature profiles.” This sentence contains a footnote, No. 42, which reads in part: “Examples include the effects of El Chichón and other volcanic eruptions . . .”

They omitted El Chichón. Yet the Washington Post’s Curt Suplee reported that “they factored into the climate models certain events peculiar to the period . . . [and] the umbrella-like aerosol clouds blown aloft by volcanoes El Chichón and Mt. Pinatubo. With those adjustments, ‘the predicted change in the troposphere is very much in line with observations,’ Santer said.”

No, it isn’t--at least not when you work in El Chichón.

Then there’s the problem of Santer’s ending the study on a high note, as it were, with annual average data from 1998, which just happens to be the big El Niño spike, now departed. Everyone knows that even after adjusting for the problems of orbital decay found in the satellite data last year, there is no significant overall warming unless this decidedly singular year is included (which leads us to predict a significant cooling trend from 1998 through 2007 in these data).

What happens if you end in, say, 1997, or if you adjust the satellite data for El Niños? (El Niño is, after all, a recurring phenomenon.) The correspondence drops further. In fact, when all the volcanoes are put in and the exception at the end of 1998 is dealt with in a statistically defensible way, the whole result probably will fall apart.

This working hypothesis is based only upon the fallout from Santer’s last big bomb, published in 1996. That paper, which just happened to appear in Nature magazine four days before the start of a vitally important U.N. conference on global warming policy, showed how the balloon-measured temperatures increasingly resembled his “state-of-the-art” climate model as climate evolved from 1963 through 1988. But when all of the readily available balloon record (at the time, 1958 to 1995) is used, the most prominent warming signal in the atmosphere simply fell apart. (One cause of suspicion was that the satellite showed no warming in the same zone.) In that study, too, temperatures ended on a very high note.

Somehow that led my colleagues and me to wonder things like “what happens if you use all the volcanoes?” and “what happens if you don’t end on an artificially high note?” So far, Santer’s paper appears to present an environment as target-rich as it was in 1996!

For years, we have watched as the 1990 IPCC notion that the climate models were “generally realistic” got torn apart by reality. But to actually see--at least twice now--a selective reading of the data used to shore up the paradigm of modeled warming is a tribute to Thomas Kuhn’s prescience about the way science works.


Kuhn, T.S., 1962, The Structure of Scientific Revolutions. Chicago: Chicago University Press.

Santer, B.D., et al., 1996. A search for human influences on the thermal structure of the atmosphere. Nature, 382, 36–45.

Michaels, P.J., and P.C. Knappenberger, 1996. Human effect on global climate? Nature, 384, 522–523.

Santer, B.D., et al., 2000. Interpreting differential temperature trends in the surface and lower troposphere. Science, 287, 1227–1232.

Suplee, C., 2000. Washington Post, February 21.