For an interesting look back at the history of IPCC deceptions, it is worth reviving the 1996 op-ed piece in the Wall Street Journal, A Major Deception on Global Warming, written by Dr. Frederick Seitz, former president of both the National Academy of Sciences and the American Physical Society.During the preparation of the IPCC's Climate Change 1995, the US State Department weighed in with a letter pressuring the IPCC to make changes to the document's important eighth chapter so as to make the text of the report conform to the recommendations of the pro-man-made-global-warming Summary for policymakers, which had been written by policymakers (not scientists) prior to the scientific report written by the IPCC scientists. This arbitrary rewriting of the document, over the objections of the scientists who participated in the original writing, was called "the most disturbing corruption of the peer review process I have ever witnessed" in Dr. Seitz's editorial. This adulterated 1995 document formed the "scientific basis" of the Kyoto Protocols. Numerous other accounts of similar IPPC corruptions of the peer-review process have led to resignations from the IPCC by prominent scientists (noted here and here and several others).
And see here for the political history of James Hansen of NASA/GISS.