A core assumption in the resurgent politics of climate change needs closer study than it typically receives. It concerns the scientific consensus said to have developed that people are dangerously heating Planet Earth.
Proponents of drastic precaution against warming regularly claim that science is "settled" on the issue. For proof, they cite the United Nations' Intergov- ernmental Panel on Climate Change (IPCC) Third Assessment Report on science. They further assert that only a few cranks now question whether humanity should endure the deprivation involved in proposed efforts to manage weather.
Fresh airing
The IPCC report will receive a fresh airing next month, when the US Congress reconvenes. Several lawmakers have promised to renew pressure for sharp cuts in emissions of carbon dioxide and other greenhouse gases. They mostly want to embarrass President George W. Bush, who last April revolted the political world by stating the obvious: The US won't sacrifice its economic future to the costly and futile Kyoto Treaty on climate change.
Few Bush antagonists will have read the IPCC report. When they cite it, they will really mean the Summary for Policymakers (SPM), which was approved at a meeting in Shanghai last January, months before publication of the full document. The SPM asserts that observed warming is occurring faster than was thought before and that science has lowered doubt about the alleged link between human activity-mainly combustion of fossil fuels-and the rising sea levels and malarial swelter presumed to lie ahead.
Lawmakers inclined to use the SPM as a proxy for the IPCC report to assert scientific consensus about global warming should review May 2 testimony before the Senate Environment and Public Works Committee by Massachusetts Institute of Technology Prof. Richard S. Lindzen. A member of the working group that produced the IPCC report, Lindzen has conducted climate and related research for more than 30 years and written or cowritten more than 200 papers and books. He formerly was a professor at Harvard University and the University of Chicago. He also belongs to the group of global warming skeptics whom alarmists blithely consign to the scientific fringe.
Areas of agreement about climate change exist, Lindzen told the senators, among them that full implementation of the Kyoto Treaty would have "little detectable impact on the climate regardless of what one expects for warming." Lindzen believes that the proper response to warming, human-induced or otherwise, is adaptation.
Invocation of the IPCC report to assert scientific consensus, Lindzen said, "is more a mantra than a proper reflection of that flawed document." Media reports don't accurately describe statements in the SPM, which-"written by representatives from governments, [nongovernmental organizations], and business"-doesn't reflect the full report.
"The vast majority" of writers of the full report had no role in preparation of the summary, Lindzen said, and weren't asked whether they agreed with it. The IPCC has defended this process by noting that 14 of the full report's lead authors wrote the SPM draft. Yet the draft was changed significantly at the Shanghai meeting.
A product of that process is this widely quoted note of alarm: "In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas emissions." The original statement in the draft was strongly hedged and included an explicit warning about uncertainty of the estimates.
"In point of fact," Lindzen told the senators, "there may not have been any significant warming in the last 60 years. Moreover, such warming as may have occurred was associated with jumps that are inconsistent with greenhouse warming."
Pressure on authors
Lindzen further alleged that IPCC coordinators applied pressure to writers of the full report, insisting that the computer models underlying warming scenarios be described more favorably than some authors wished. "I personally witnessed coauthors forced to assert their 'green' credentials in defense of their statements," Lindzen testified.
As a document written by committee about a monstrously complex subject, the IPCC report represents an important scientific step. But it amounts to collective compromise in an area still governed by uncertainty. It is not consensus on scientific fact. And it is deception to claim otherwise.
