The credibility of the IPCC has been the subject of much debate, as it has been suggested that IPCC officials violated standard rules of procedure in finalizing their 1990 and 1995 reports. Underlying these violations is the allegation that IPCC findings have been altered in such a way as to justify a conspiratory political agenda--that global warming is a real and legitimate threat.
Shortly before the Earth Summit in Rio de Janeiro, the Science and Environmental Policy Project (SEPP), headed by well-known contrarian Dr. S. Fred Singer, released a report attacking the IPCC on numerous counts. Among the most serious accusations was the following: that Chapter 8 the IPCC report, the chapter detailing the extent of human influence on global climate, had been edited, with key clauses expressing the uncertainty of man's impact on climate change intentionally discarded in order to conform to the Summary for Policy Makers--a clear violation of the formal scientific review process essential to all ongoing scientific debates.
In its defense, the IPCC rebutted that the reasons for these changes were for the purpose of scientific clarity. All changes were scientifically justifiable and were made upon the recommendation of IPCC scientists and policy makers, and represent the consensus of those involved in Working Group-I of the IPCC. However, a survey conducted in 1991 by SEPP suggests otherwise, reporting that many scientists involved in the IPCC process do not agree with the Summary as printed in the 1990 and 1992 reports. The survey indicated that not only did 40 percent of the group not agree with the IPCC summary, but also, that many felt that the report was running into the danger of describing a false scenario to the public. Almost all of the IPCC group agreed with the basic conclusion stated on p 254 of the report that, "it is not possible to attribute all, or even a large part, of the observed global mean warming to the enhanced greenhouse effect on the basis of observational data currently available."
It has also been alleged that the conclusions of the IPCC Summary are not supported by the evidence listed in the report. For example, the summary states that increasing temperature trends are in accordance with GCMs, while the body of the report expresses concern over the certainty of the very GCMs used to make such predictions. The SEPP survey indicates that 60 percent of the IPCC group does not believe that the models accurately simulate the ocean-atmosphere circulation system., an essential component of any climate model. Furthermore, the panel's position concerning the role of water vapor in forcing climate change is one of uncertainty as well, as it's latest assessment stresses the lack of data and overall uncertainty concerning the mechanisms behind H20 vapor.
In 1996, the Global Climate Coalition (GCC) issued a report attacking lead-author Ben Santer, claiming that he and the IPCC were guilty of avoiding the highly necessary peer review process, and that instead of following standard scientific-review guidelines, all changes were approved by a panel of editors who were also among the authors, thus allowing them to accept and make changes in accordance with their own interests. The GCC maintain that the concluding summary had been deleted from the final report, in addition to a paragraph which down plays the uncertainty of man-made climate change. Santer claims that all reports of scientific uncertainty were not removed, and that the executive summary and a significant portion of Chapter eight were devoted to a discussion of the uncertainties underlying human-induced climate change. He states that it is a "supreme irony" that he is the subject of attack for such manipulation of the truth when he was the one to urge the inclusion of signal and noise uncertainties in the text, and adds that there is a calculated conspiracy to undermine the IPCC as the leading scientific authority on global warming and climate change as well as his reputation as a scientist.