The IPCC’s conclusions are not based solely on painstaking studies. Nor is the IPCC’s source material all published in peer-reviewed journals. In fact, 30% of the references in the IPCC’s 2007 report (5,587 out of 18,531) are to grey literature – including press releases, magazine articles, and advocacy material produced by groups such as Greenpeace. Furthermore, the genuinely peer-reviewed material cited by the IPCC amounts to several thousand studies. Simple arithmetic indicates that only a fraction could possibly have appeared in the world’s leading journals.