Even though many people like to say that 1998 was the warmest year in the millenium, the underlying statistical treatment by Mann et al. - also known as the hockey stick graph - has been discredited by more recent investigations.
The recent report of the NAS panel could not confirm the millenial assertion of Mann, Bradley, and Hughes, citing high levels of uncertainty. Moreover, the House Energy and Commerce Committee made three researchers, Edward Wegman (a rather well-known statistician), David Scott, and Yasmin Said, to look at the hockey stick graph again. In a report that was just released, the criticism by McKitrick and McIntyre was confirmed. Mann's method is selectively mining for hockey sticks.
- U.S. House: Factsheet
- Wegman report: full
- Wall Street Journal (subscription)
- Climate Audit & after the release
- National Center for Policy Analysis
The U.S. House committee has found that the sharing of research material, data, and results were haphazardly and grudgingly done. The players relied on peer-review too much even though it was not independent. The statisticians have studied the social network - the collaboration graph - of the extended hockey team in detail and showed that virtually all of the "independent" peer-reviewers are Michael Mann's direct co-authors, while some "cliques" are completely disconnected.
Moreover, the topic was too much politicized which makes it hard for the researchers to re-evaluate their public positions without losing credibility. I would interpret this insight as a calculation showing that Mann et al. can't really offer anything positive to science in the future. The Mann et al. research did not provide any evidence that the 1990s was the hottest decade in 1000 years and 1998 was the hottest year.
The statisticians also correctly conclude that blogs are not a good place for a scientific debate on this issue - which certainly holds for many other issues, too.
The main villain, Mr. Michael Mann, has replied that Profs. Wegman, Scott, and Said just uncritically "parrot" an economist and an "oil industry consultant" (McIntyre has worked as a consultant in hard-rock mineral mining industry), while he offers several paragraphs of downright lies about the recent report of the NAS panel. It is not a terribly constructive approach to members of the committee like David W. Scott who seems to have contributed to science more than Mann has, even if we count his flawed hockey stick papers.
Mann's frequently publicized picture of the world as a class struggle between the oil industry and heroic activists like him show that he is mentally ill, politically radical obsessed person who not only has nothing to do with a serious, prejudice-free approach to scientific questions, but who is also slightly dangerous for the society.