Scientists Remain Uncertain: `Global Warming' Science: Fact vs. Fiction

Article excerpt

For more than a decade now, consumers have been confronted with frequent warnings that our carbon-dioxide-producing, modern way of life contributes to global warming, and thus is setting up the world for climatic catastrophe--unless we do something to reverse course soon.

Nothing new here, but in recent months the warnings have taken on a heightened sense of urgency following reports that scientific authorities have answered some key questions about the underlying science behind global-warming estimates. This increased certainty, we have been led to believe, strengthens the case for "action" on global warming, which typically involves instituting policies to meet the goals of the Kyoto global warming treaty, signed by the Clinton Administration in 1997.

Whether such efforts would do any good is another issue entirely (see page 43). At this point, judgment about whether even to take action first requires some understanding of the underlying knowledge about climate change. And, as closer scrutiny of the relevant data reveals, the underlying facts on this front are quite the opposite of what has been popularly portrayed.

As trumpeted by the popular media, our new alleged certainty about the effects and causes of global warming stem from two scientific studies: The first, drawn from a lengthy compendium of climate-change data put together by the United Nations' Intergovernmental Panel on Climate Change (IPCC), was released this past winter. The second, a follow-up study on the same subject, released last month by the National Research Council (NRC) of the National Academy of Sciences.

In both cases, publicity about these reports suggested, in so many words, that the debate about "global warming" was over. Commenting on the original IPCC study, for instance, Time magazine asserted: "Scientists no longer doubt that global warming is happening, and almost nobody questions the fact that humans are at least partly responsible."

"A decade ago, the idea that the planet was warming up as a result of human activity was largely theoretical," the newsmagazine explained this past April. "... Not anymore. As an authoritative report issued a few weeks ago by the [IPCC] makes plain, the trend toward a warmer world has unquestionably begun."

U.S. News and World Report, among other news outlets, offered a similar take on the IPCC study, calling it "the most definitive--and scary--report yet, declaring that global warming is not only real but man-made."

Yet the study in question was not all that it was made out to be. The publication, a mere 20-page "Summary for Policymakers" based on a yet-to-be-released 3,000-page report, hardly represented an authoritative picture of IPCC science, say climate researchers familiar with the project.

In fact, these researchers say, the full report itself is heavily nuanced, containing numerous qualifications, provisos and cautions about the proper interpretation of the data--as is fairly typical of scientific studies relying on many and varied sources. Most of this nuance was simply omitted in the summary, which came across as categorical and definite, thus giving rise to the scary stories.

It was precisely because of this discrepancy that the second study was commissioned--in effect, a study of a study. Because of serious questions about the reliability of the IPCC summary, in May the White House asked the National Research Council to identify "the areas in the science of climate change where there are the greatest certainties and uncertainties," and to comment in particular on the quality of science represented in the IPCC summary that had been making so many headlines.

And, ironically, the same thing happened all over again. Once more, the report in question stressed nuance and uncertainty. And once more the media stories took their cues from the boiled-down treatment available in report's summary.

Thus, The New York Times reported that NRC analysis "reaffirmed the mainstream scientific view that the earth's atmosphere was getting warmer and that human activity was largely responsible. …