According to the Wall Street Journal editorial, a semiretired Toronto minerals consultant and an economist, with about $5,000 of his own money and time, took on an apparently simple task — trying to double-check the influential graphic known as the “hockey stick” — and eventually confronted an influential scientific community before a Congressional Committee, and won. What was the sequence of events?

1990 — MWP — Based on numerous anecdotal studies, the Intergovernmental Panel on Climate Change (IPCC) in 1990 included a schematic view of the past 1000 years there was a period of elevated temperatures known as the Medieval Warm Period, which was followed by the Little Ice Age, and then a new period of global warming.

Alternative options for temperature history. IPCC 1990 Figure 7.1.c (red), MBH 1999 40 year average used in IPCC TAR 2001 (blue), and Moberg et al 2005 low frequency signal (black) from Wikipedia.

1998 — MBH98 — Mann, Bradley and Hughes published a quantitative study using a new climate field methodology, showing temperatures as a hockey stick shape, and eliminated the Medieval Warm Period, flattening the fluctuations in global temperatures over most of the past millennium (the blade of the hockey stick) until we get to the 20th century, where the rate of global warming takes off in a sharp upward surge (the handle of the hockey stick).

2001 — IPCC — In telling the global warming story, the IPCC, since 2001, has relied very heavily on what has become known as the “hockey stick graph”. It is based on a 1999 paper, the principal author of which was paleoclimatologist Michael Mann.

2003 — M&M — Two Canadians, Steve McIntyre, an engineer, and Ross McKitrick, an economist, challenged Mann’s work in 2003. They argued his technique produced hockey sticks from just about any set of data. They started a blog, where they continued to document the notably less than scientific manner in which Mann withheld adverse statistical results and important data, and discouraged the publication of criticism of his work.

14 Feb 2005 — WSJ — A Wall Street Journal report of the controversy let the world know about the dispute between a semiretired Toronto minerals consultant and IPCC lead author, and climatologist Michael Mann of the University of Virginia.

23 June 2005 — Barton — The WSJ article attracted the attention of the US House Committee on Energy and Commerce. It wrote to Mann and his co-authors, as well as to the IPCC, demanding relevant information and then approached independent US statisticians for advice on assessing the data provided.

18 July 2005 — Protest — The requests for information alarmed many scientists and their professional organisations who also expressed strong concerns:

• A statement from the EGU
• The American Association for the Advancement of Science (AAAS)
• A Nature editorial
• A letter from US scientists (including leading members of the NAS, a
• Nobel Prize winner and two of us (ES, GS))
• A letter from the head of the National Academy of Sciences, and
• A commentary from Tom Crowley in EOS
• Other politicians, the House Committee on Science and Henry Waxman.

June 22 — NAS — The National Academy of Sciences found there is sufficient evidence from tree rings, retreating glaciers, and other “proxies” to say with confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years, and less confidence in reconstructions of surface temperatures from 1600 back to A.D. 900, and very little confidence in findings on average temperatures before then.

14 July — Wegman — Leading US statistician Edward Wegman, of George Mason University, assembled a group of statisticians to assess the Mann data. Their report supported McKitrick and McIntyre’s criticisms of the hockey stick, finding Mann’s statistical work flawed and unable to support the claims of the hottest century, decade and year of the past millennium.

It is important to note the isolation of the paleoclimate community; even though they rely heavily on statistical methods they do not seem to be interacting with the statistical community. Additionally, we judge that the sharing of research materials, data and results was haphazardly and grudgingly done. In this case we judge that there was too much reliance on peer review, which was not necessarily independent. Moreover, the work has been sufficiently politicized that this community can hardly reassess their public positions without losing credibility. Overall, our committee believes that Dr. Mann’s assessments that the decade of the 1990s was the hottest decade of the millennium and that 1998 was the hottest year of the millennium cannot be supported by his analysis.

18 July — Press — The mainstream press were reluctant to cover the Wegman report, heavily critical of behaviour of individual scientists, and the quality of the IPCC peer review process for policy related decisions. The Australian was the first to run an op-ed, 4 days after the report was released.

19 July 2006 — Hearings

Go to an archive of all the stories when they broke at the controversial topics hockey stick archive.