National Policy Analysis Paper #177
published December 1997

The Myth of Scientific Consensus
on Global Warming

by David Ridenour

Forget what you've read in the press or heard on television: There is no scientific consensus on global warming.

In recent months, there has been much talk in the national news media about a scientific consensus on global warming. A page one story appearing in The Washington Post on November 12, for example, blared, "Consensus Emerges Earth is Warming -- Now What?"

But precisely how did The Washington Post and other papers conclude that a scientific consensus exists? Did they poll climate scientists? Perhaps they, like Vice President Gore and other administration officials, relied on various letters supporting the global warming theory signed by self-proclaimed "scientific experts."

One such letter, "Scientists' Statement on Global Climatic Disruption," was circulated by a Washington, D.C.-based group called Ozone Action. It purported to have as signatories 2,611 scientists from the U.S. and abroad endorsing the idea that the scientific evidence of global warming was conclusive. The only problem is, most of the signers have little or no background in climate science. According to Citizens for a Sound Economy, only about 10% of the letter's signers have experience in fields connected with climate science. What's worse, the letter includes as signers two landscape architects, ten people with backgrounds in psychology, one person trained in traditional Chinese medicine techniques and one person trained in gynecology. There is a world of difference between a gynecologist and a climatologist. Still, a number of journalists actually took the Ozone Action letter seriously.

Or, perhaps The Washington Post and others determined there was a consensus based upon the Second Assessment Report of the United Nations Intergovernment Panel on Climate Change (IPCC) released in 1995. The report, which purports to be the culmination of some 2,000 scientists' work, found that the "balance of evidence suggests a discernible human influence" on climate. But this is misleading: While many scientists did indeed work on the Second Assessment Report, they did not necessarily support the conclusions of the final report. As Dr. John W. Zillman, one of the scientists who participated in the process noted, "[The IPCC was] meticulous in insisting that the final decision on whether to accept particular review comments should reside with chapter Lead Authors. This was at variance with the normal role of journal editorial boards and led to suggestions that some Lead Authors ignored valid critical comments or failed to adequately reflect dissenting views when revising their text."

Surveys of climate scientists and meteorologists don't lend much credibility to the argument that a consensus exists either:

A survey of over 400 German, American and Canadian climate researchers conducted by Dennis Bray of the Meteorologisches Institut der Universitat Hamburg and Hans von Storch of GKSS Forschungszentrum and reported in the United Nations Climate Change Bulletin, for example, found that only 10% of the researchers surveyed "strongly agreed" with the statement "We can say for certain that global warming is a process already underway." Further, 35% of those surveyed either disagreed with the statement or were undecided. Perhaps even more interesting, 67% of the researchers either disagreed or were uncertain about the proposition that climate change will occur so suddenly that a lack of preparation would devastate certain parts of the world -- the underlying assumption on which the talks in Kyoto, Japan were based. Close to half of the researchers -- 48% -- indicated that they don't have faith in the forecasts of the global climate models, the strongest argument in favor of quick, decisive, international action to counter the threat of global warming. Another 20% expressed uncertainty about these models.

Another survey, conducted by American Viewpoint for Citizens for a Sound Economy, found that, by a margin of 44% to 17%, state climatologists believe that global warming is largely a natural phenomenon. The survey further found that 58% of the climatologists disagreed with President Clinton's assertion that "the overwhelming balance of evidence and scientific opinion is that it is no longer a theory, but now fact, that global warming is for real," while only 36% agreed with the assertion. Thirty-six of the nation's 48 official state climatologists participated in the survey.

There is, therefore, no scientific consensus on global warming.

But perhaps even more important than whether or not scientists have reached a consensus, however, is whether or not the scientific data backs up the theory. Data collected from NASA's TIROs series of weather satellites show a slight cooling trend of .04 degrees Celsius over the past 18 years. These findings have been confirmed by weather balloons.

Even if scientists haven't developed a consensus on global warming, the scientific data has: Global warming is not occurring.


(Ridenour is vice-president and director of environmental and regulatory affairs at
The National Center for Public Policy Research in Washington, D.C.)

published December 1997 by
The National Center for Public Policy Research
300 Eye St. NE #3
Washington, D.C. 20002
202/543-1286  --  Fax 202/543-4779
Reprints permitted provided source is credited.

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