|'Hypothetical thing thought to have special powers'|
Launched by Michael Mann and two co-authors in papers in 1998 and 1999, the work purported to show that temperature had been more or less flat for the past 1,000 years until the second half of the twentieth century when there was an alarming spike - the (ice) hockey stick.
Criticisms of the quality of the work centred on two issues. Some of the data, it was alleged, had been cherry picked to create a hockey stick, and the statistical methods used in analysing the data were flawed.
The response of Michael Mann and the paleoclimate community was to defend the 1998 (MBH98) and 1999 (MBH99) papers with a plethora of further peer reviewed papers which endorsed the original claims usually claiming to be independent.
I have been looking the Wegman Report, a five year old publication for a US Congressional Committee. Compiled by Edward Wegman, a respected academic expert in statistics. The report was devastating:
"In general we found MBH98 and MBH99 to be somewhat obscure and incomplete and the criticisms of MM03/05a/05b (the critics) to be valid and compelling. . . Our findings from this analysis suggest that authors in the area of paleoclimate studies are closely connected and thus 'independent studies' may not be as independent as they might appear on the surface.. . . In this case we judge that there was too much reliance on peer review, which was not necessarily independent. . . Overall, our committee believes that Mann's assessments that the decade of the 1990's was the hottest decade of the millennium and that 1998 was the hottest year of the millennium, cannot be supported by his analysis."
That all seems clear. Yet peer reviewed paper after peer reviewed paper has been produced by the paleoclimate community supporting Mann's original analysis.
Take a local example. In December 2009 the Royal Society of Edinburgh produced a briefing paper aimed at the then forthcoming Copenhagen Climate Summit which was also 'intended as a helpful summary for the Scottish Government and Parliament, for public and private bodies, and for fellow citizens.'
In this document the claim is made:
Several independent estimations have now been made of the global or hemispheric average temperatures for the last two millennia. Figure 3 is one of these, and shows that the late 20th Century warming has been rapid and large compared with earlier periods (note that this is independent of the University of East Anglia reconstruction, about which there has recently been much controversy).Figure 3 refers to Hegerl et al 2006. I wrote about Gabi Hegerl last week as being an Edinburgh members of the paleoclimate community. In Wegman's terms she is not independent of Mann. Nor is the paper cited independent from MBH99 or 'the University of East Anglia reconstruction about which there has been much controversy'. A more detailed analysis of this false claim by the Royal Society of Edinburgh, and of the deficiencies of Hegerl et al 2006, can be found here.
This week a peer reviewed paper has been published in the Annals of Applied Statistics. McShane and Wyner 2010 weighs in to the issue of the statistical methods used.
Research on multi-proxy temperature reconstructions of the earth’s temperature is now entering its second decade. While the literature is large, there has been very little collaboration with university level, professional statisticians (Wegman et al., 2006; Wegman, 2006). Our paper is an effort to apply some modern statistical methods to these problems. While our results agree with the climate scientists findings in some respects our methods of estimating model uncertainty and accuracy are in sharp disagreement. On the one hand, we conclude unequivocally that the evidence for a "long-handled" hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data.In other words, these authors consider the previous reconstructions purporting to show that the late twentieth century warmth is unprecedented in the last millennium are unsupportable. In doing so McShane and Wyner take a position which is consistent with the analysis of Wegman as well as the critics who had first challenged the Mann and University of East Anglia claims.
Of course the above doesn't prove that recent temperature increases are not unprecedented. All we know from the above is that some of the evidence upon which these IPCC claims have been based - is fairy dust.
How much of the remainder of the 'evidence' is bogus?
And why have the paleoclimate community and scientific advisers to our governments been defending fairy dust for the last five and more years?
Finally, here is a comparison of the discredited hockey stick from Mann and the temperature reconstruction attempt by McShane and Wyner.
|Mann version of the hockey stick|
|McShane & Wyner version|