The Hockey Stick Illusion

The Hockey Stick Illusion (2010) by AW Montford is a superb history of the controversy surrounding dendroclimatology and in particular the 1998 paper by Michael Mann that purported to show that temperatures are at 2000 year highs with authority and subsequent similar reconstructions. The book is thorough and has sufficient detail so that the numerical arguments can be followed but is brisk and well written enough so that the book is also a good read.

Dendroclimatology is the study of determining part climate from trees and primarily from the widths of tree rings. As the instrument record only extends back to the mid 1850s it may be useful for determining the climate in the past.

The book starts off with a description of the original Mann paper, MBH98 that catapulted Mann to scientific stardom and was given lead placement in the IPCC second assessment report. In the report it was featured numerous times and was in the summary for policymakers. In addition the iconic status was further elevated as it was used as a background for presentation of the report. MBH98 was a radical change to scientific orthodoxy which had been that around the year 1100 temperatures were elevated from later years and that there were indications that it was warmer than the present time. This view was expressed in the IPCC’s first assessment report.

Steven McIntyre was a retired consultant in Canada who was interested in exactly how this paper that overturned established views, MBH98, was constructed. McIntyre had been a child math prodigy and had been awarded a scholarship to study at Oxford. He began to dig around and see if he could construct the hockey stick like reconstruction himself. Nature, the scientific publication that MBH98 was published in was meant to have rules ensuring that the data for papers was publicly accessible so that the work could be checked. What McIntyre found was that the data and methods were not at all easily obtainable. McIntyre began the blog Climate Audit so that he could share his progress in examining MBH98. Climate Audit would then be countered by the Real Climate blog which was set up by an advertising executive in order to discredit skeptics.

McIntyre and Ross McKitrick, an academic economist, published a paper showing that MBH98 was unlikely to be reliable in an obscure journal Energy and Environment. This added to the controversy surrounding the MBH98 paper and led to the Hockey Stick being examined in Washington. This examination gave the finding that the statistics used in MBH98 were deeply flawed and thus that the results were not reliable.

This did not lead to an end of hockey stick reconstructions, instead others were prepared by associates of Michael Mann, member’s of the self-named hockey team. They would then continue to use similar reconstructions and despite being labeled as ‘independent’ would use the same proxies and similar methods. The tricks of hiding the data and methodology that were used to hinder examination of MBH98 continue to be used.

Other papers have been published showing that tree rings are not reliable and that many indicate, although with considerable uncertainty, that the temperatures were higher around 1100 than in current times. These papers have not just come from skeptics but also from scientists who agree in general about global warming like Hans von Storch.

The climategate emails were reveled just as the book was about to be finished and are mentioned that showed that much of what McIntyre alleged was happening regarding suppression of dissenting views was indeed occurring. There was also the brutally honest email from non-skeptic scientist Edward Cook stating:

Without trying to prejudice this work, but also because of what I almost think I know to be the case, the results of this study will show that we can probably say a fair bit about <100 year extra-tropical NH temperature variability (at least as far as we believe the proxy estimates), but honestly know fuck-all about what the >100 year variability was like with any certainty (i.e. we know with certainty that we know fuck-all).

Yet to come was the obscene attempt by Virginia Attorney General Cuccinelli to prosecute Michael Mann. It is worth noting that Steve McIntyre also condemns this political intervention.

Interestingly the book does not discuss the implications of the uncertainty in past temperatures and the considerable likelihood that temperatures in human history were warmer than the present. This would mean that Anthropogenic Global Warming is not nearly as big a problem as is presented by many environmentalists. It does not mean that AGW is not happening or that attempts should not be made to change to low C02 emitting energy sources. The most disturbing thing about the whole affair is that people relied on highly suspect evidence and rather than making sure it was correct attempted to smear those who examined it.

The book is really well done, the story and the science and very well presented. It is, along with An Appeal to Reason by Nigel Lawson, Cool it by Bjorn Lomborg and Climate of Extremes by Pat Michaels one of the best presentations of skeptical views of global warming.



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