Cookie-Cutter Science
Oops…they did it again. .

By Paul Georgia
June 8, 2001 9:35 a.m.

esterday saw the release of yet another cookie-cutter global-warming report claiming that the world is warming and that man is to blame. This one is from the prestigious National Academy of Sciences, but what we find within is unimpressive and disappointing.

Indeed, it is 23 pages of linguistic trickery that when parsed says little. It is likely to alarm those who don't understand scientific methodology or the nuances of the global warming-debate, i.e., most of the public. Judging by the way it has been reported in the press, this is clearly an area of concern.

The report states, "Despite the uncertainties, there is general agreement that the observed warming is real and particularly strong within the past 20 years. Whether it is consistent with the change that would be expected in response to human activities is dependent upon what assumptions one makes about the time history of atmospheric concentrations of the various forcing agents, particularly aerosols" (emphasis added).

It also says, "The predicted warming of 3 degrees C (5.4 degrees F) by the end of the 21st century is consistent with the assumptions about how clouds and atmospheric relative humidity will react to global warming" (emphasis added).

Of course the predictions are consistent with the assumptions. But the assumptions are the issue here. If the assumptions are correct, then the global-warming advocates have a case; if not, they don't. That is where the scientific debate rages today and pretending that it isn't is useless and uninformative.

Assumptions need to be tested by empirical evidence, however, and many of the most important ones haven't been. The report correctly points out that the primary assumption driving speculations about global warming is the water vapor feedback effect. According to this assumption, a small temperature increase caused by rising atmospheric concentrations of manmade greenhouse gases would lead to increased evaporation. Higher water vapor levels — a major greenhouse gas — in the atmosphere, would raise global temperatures even further. Indeed, the lion's share of the predicted warming depends on this assumption.

Absent climate feedbacks, says the report, Earth's temperature would increase 1.2 degrees C (2.2 degrees F) at most. Until recently the positive feedback assumption had not been tested. In March, however, the Bulletin of the American Meteorological Society published an empirical study that found the assumption to be wrong. What it found was a negative feedback powerful enough to offset all other positive feedback effects. Other important assumptions have also gone by the wayside in the face of actual evidence. (For a broader analysis of key global-warming assumptions see http://www.cei.org/OnPointReader.asp?ID=1477.)

The report also discussed whether the Summary for Policymakers of the Third Assessment Report of the United Nations' Intergovernmental Panel on Climate Change (IPCC) accurately reflects the findings of the underlying report. It concluded that the summary "reflects less emphasis on communicating the basis for uncertainty and a stronger emphasis on areas of major concern associated with human-induced climate change," but that "most changes that did occur lacked significant impact," implying that changes of significant impact did occur.

Chapter 7 of the IPCC report on physical processes, for instance, is 35 pages long. It discusses extensively the problems with the ability to model the atmospheric processes that govern climate change. One of the major problems it discusses is the inability to accurately reflect cloud dynamics, which is directly relevant to the water vapor issue.

This lengthy chapter was summarized in one sentence in the Summary for Policymakers. It states, "Understanding of climate processes and their incorporation in climate models have improved, including water vapor, sea-ice dynamics, and ocean-heat transport." This might be defensible as a stand-alone statement, but it hardly summarizes the chapter.

To be fair to the members of the committee who wrote the report, it does heavily qualify its claims. If you read the report carefully, it becomes evident that there are serious problems with the global-warming hypothesis. It points out, for example, that the inability of the climate models to simulate natural variability makes it very difficult to establish a causal link between rising concentrations of greenhouse gases and rising global temperatures. In other words, if you don't understand the climate's natural variations, you can't determine whether the observed changes are natural or man-made.

Fortunately, the White House understands the gist of the report and the importance of the caveats. "This report shows what is known and certain, and that which is unknown or surmised," said White House press secretary Ari Fleischer. "For instance, it concludes that the Earth is warming. But it is inconclusive on why — whether it's man-made causes or whether it's natural causes."

There is no smoking gun here. The best available evidence still suggests that the amount of warming likely to occur over the next 100 years will be trivial.