90% certain that temperatures will continue to rise, with average global surface temperature projected to increase by between 1.4 and 5.8 °C above 1990 levels by 2100". The TAR has also been endorsed by the Canadian Foundation for Climate and Atmospheric Sciences, Canadian Meteorological and Oceanographic Society, and European Geosciences Union (refer to "Endorsements of the IPCC"). In 2001, the US National Research Council (US NRC) produced a report that assessed Working Group I's (WGI) contribution to the TAR. US NRC (2001) "generally agrees" with the WGI assessment, and describes the full WGI report as an "admirable summary of research activities in climate science". IPCC author Richard Lindzen has made a number of criticisms of the TAR. Among his criticisms, Lindzen has stated that the WGI Summary for Policymakers (SPM) does not faithfully summarize the full WGI report. For example, Lindzen states that the SPM understates the uncertainty associated with climate models. John Houghton, who was a co-chair of TAR WGI, has responded to Lindzen's criticisms of the SPM. Houghton has stressed that the SPM is agreed upon by delegates from many of the world's governments, and that any changes to the SPM must be supported by scientific evidence. IPCC author Kevin Trenberth has also commented on the WGI SPM. Trenberth has stated that during the drafting of the WGI SPM, some government delegations attempted to "blunt, and perhaps obfuscate, the messages in the report". However, Trenberth concludes that the SPM is a "reasonably balanced summary". US NRC (2001) concluded that the WGI SPM and Technical Summary are "consistent" with the full WGI report. US NRC (2001) stated: ... the full [WGI] report is adequately summarized in the Technical Summary. The full WGI report and its Technical Summary are not specifically directed at policy. The Summary for Policymakers reflects less emphasis on communicating the basis for uncertainty and a stronger emphasis on areas of major concern associated with human-induced climate change. This change in emphasis appears to be the result of a summary process in which scientists work with policy makers on the document. Written responses from U.S. coordinating and lead scientific authors to the committee indicate, however, that (a) no changes were made without the consent of the convening lead authors (this group represents a fraction of the lead and contributing authors) and (b) most changes that did occur lacked significant impact. IPCC process There are a small number