From Burt Rutan's Blog:
"One has only to look at the two most notable charts (below) from two United Nations IPCC summary reports, published a decade apart, to realize that something might be seriously wrong.
Estimated average global temperatures for the last thousand years
"The fact that the 2001 “hockey stick” chart was presented in color in several sections of the 2001 IPCC report, without explaining how the scientists managed to completely eliminate their earlier depiction of the Medieval Warm Period and the Little Ice Age (both are well covered in historical documents as well as scientific analysis is unacceptable behavior (see http://www.co2science.org/data/mwp/mwpp.php). Click on link at top for remainder of post.