The notion of "scientific unanimity'' is currently intimately tied to the Working Group I report of the Intergovernmental Panel on Climate Change issued in September 1990. That panel consists largely of scientists posted to it by government agencies. The panel has three working groups. Working Group I nominally deals with climate science. Approximately 150 scientists contributed to the report, but university representation from the United States was relatively small and is likely to remain so, since the funds and time needed for participation are not available to most university scientists.
Many governments have agreed to use that report as the authoritative basis for climate policy. The report, as such, has both positive and negative features.
Methodologically, the report is deeply committed to reliance on large models, and within the report models are largely verified by comparison with other models.
Given that models are known to agree more with each other than with nature (even after "tuning''), that approach does not seem promising. In addition, a number of the participants have testified to the pressures placed on them to emphasize results supportive of the current scenario and to suppress other results.
That pressure has frequently been effective, and a survey of participants reveals substantial disagreement with the final report.
Nonetheless, the body of the report is extremely ambiguous, and the caveats are numerous. The report is prefaced by a policymakers' summary written by the editor, Sir John Houghton, director of the United Kingdom Meteorological Office.
His summary largely ignores the uncertainty in the report and attempts to present the expectation of substantial warming as firmly based science. The summary was published as a separate document, and, it is safe to say that policymakers are unlikely to read anything further.
On the basis of the summary, one frequently hears that "hundreds of the world's greatest climate scientists from dozens of countries all agreed that.|.|.|.'' It hardly matters what the agreement refers to, since whoever refers to the summary insists that it agrees with the most extreme scenarios (which, in all fairness, it does not). I should add that the climatology community, until the past few years, was quite small and heavily concentrated in the United States and Europe.
While the International Panel on Climate Change's reports were in preparation, the National Research Council in the United States was commissioned to prepare a synthesis of the current state of the global change situation.
The panel chosen was hardly promising. It had no members of the academy expert in climate. Indeed, it had only one scientist directly involved in climate, Stephen Schneider, who is an ardent environmental advocate. It also included three professional environmental advocates, and it was headed by a former senator, Dan Evans.
The panel did include distinguished scientists and economists outside the area of climate, and, perhaps because of this, the report issued by the panel was by and large fair. The report concluded that the scientific basis for costly action was absent, although prudence might indicate that actions that were cheap or worth doing anyway should be considered.
A subcommittee of the panel issued a report on adaptation that argued that even with the more severe warming scenarios, the United States would have little difficulty adapting.
Not surprisingly, the environmentalists on the panel not only strongly influenced the reports, but failing to completely have their way, attempted to distance themselves from the reports by either resigning or by issuing minority dissents.
Equally unsurprising is the fact that the New York Times typically carried reports on that panel on page 46. The findings were never subsequently discussed in the popular media--except for claims that the reports supported the catastrophic vision. Nevertheless, the reports of that panel were indicative of the growing skepticism concerning the warming issue.
Indeed, the growing skepticism is in many ways remarkable. One of the earliest protagonists of global warming, Roger Revelle, the late professor of ocean sciences at Scripps Institution of Oceanography who initiated the direct monitoring of carbon dioxide during the International Geophysical Year (1958), coauthored with S. Fred Singer and Chauncy Starr a paper recommending that action concerning global warming be delayed insofar as current knowledge was totally inadequate.
Another active advocate of global warming, Michael McElroy, head of the Department of Earth and Planetary Sciences at Harvard, has recently written a paper acknowledging that existing models cannot be used to forecast climate.
One might think that such growing skepticism would have some influence on public debate, but the insistence on "scientific unanimity'' continues unabated.
At times, that insistence takes some very strange forms. Over a year ago, Robert White, former head of the U.S. Weather Bureau and currently president of the National Academy of Engineering, wrote an article for Scientific American that pointed out that the questionable scientific basis for global warming predictions was totally inadequate to justify any costly actions.
He did state that if one were to insist on doing something, one should only do things that one would do even if there were no warming threat.
Immediately after that article appeared, Tom Wicker, a New York Times columnist and a confidant of Sen. Gore, wrote a piece in which he stated that White had called for immediate action on "global warming.''
My own experiences have been similar. In an article in Audubon Stephen Schneider states that I have "conceded that some warming now appears inevitable.'' Differences between expectations of unmeasurable changes of a few tenths of a degree and warming of several degrees are conveniently ignored.
Karen White in a lengthy and laudatory article on James Hansen that appeared in the New York Times Sunday Magazine reported that even I agreed that there would be warming, having "reluctantly offered an estimate of 1.2 degrees.'' That was, of course, untrue.
Most recently, I testified at a Senate hearing conducted by Sen. Gore. There was a rather arcane discussion of the water vapor in the upper troposphere. Two years ago, I had pointed out that if the source of water vapor in that region in the tropics was from deep clouds, then surface warming would be accompanied by reduced upper level water vapor. Subsequent research has established that there must be an additional source--widely believed to be ice crystals thrown off by those deep clouds. I noted that that source too probably acts to produce less moisture in a warmer atmosphere.
Both processes cause the major feedback process to become negative rather than positive. Sen. Gore asked whether I now rejected my suggestion of two years ago as a major factor. I answered that I did.
Gore then called for the recording secretary to note that I had retracted my objections to "global warming.'' In the ensuing argument, involving mostly other participants in the hearing, Gore was told that he was confusing matters.
Shortly thereafter, however, Tom Wicker published an article in the New York Times that claimed that I had retracted my opposition to warming and that that warranted immediate action to curb the purported menace. I wrote a letter to the Times indicating that my position had been severely misrepresented, and, after a delay of over a month, my letter was published.
Sen. Gore nonetheless claims in his book that I have indeed retracted my scientific objections to the catastrophic warming scenario and also warns others who doubt the scenario that they are hurting humanity.
Why, one might wonder, is there such insistence on scientific unanimity on the warming issue?
After all, unanimity in science is virtually nonexistent on far less complex matters.
Unanimity on an issue as uncertain as "global warming'' would be surprising and suspicious. Moreover, why are the opinions of scientists sought regardless of their field of expertise? Biologists and physicians are rarely asked to endorse some theory in high energy physics.
Apparently, when one comes to "global warming,'' any scientist's agreement will do.
The answer almost certainly lies in politics. For example, at the Earth Summit in Rio, attempts were made to negotiate international carbon emission agreements. The potential costs and implications of such agreements are likely to be profound for both industrial and developing countries.
Under the circumstances, it would be very risky for politicians to undertake such agreements unless scientists "insisted.'' Nevertheless, the situation is probably a good deal more complicated than that example suggests.