Hockey Stick reduced to sawdust

by William Yeatman on October 7, 2004

in Science

Once again (see previous issue), a new study finds that the hockey stick reconstruction of past temperatures produced by Michael Mann and colleagues is based on methodological errors and shortcomings.  In Re-constructing Past Climate from Noisy Data (Science Express, Sept. 30), Hans von Storch and colleagues first looked at the likelihood of being able to get an accurate climate signal from historical proxy data (tree rings, boreholes, ice cores, etc.) by estimating the amount of statistical noise inherent in such data.  They discovered that the amount of noise was such that it was likely that hockey-stick like reconstructions had severely underestimated past climate variability. 


This would explain why the hockey stick, which claims to show that the global mean temperature during the first 900 years of the last millennium was relatively stable and then rose sharply in the twentieth century, failed to show evidence of the Medieval Climate Optimum and the Little Ice Age, for which there is a great deal of historical and paleo-climatological evidence.  The hockey-stick graph was featured prominently in the IPCCs Third Assessment Report, published in 2001.


In a commentary on von Storch et als paper, T. J. Osborn and K. R. Briffa, prominent paleo-climatologists from the University of East Anglia, stress the importance of the findings.  They say, The message of the study by von Storch et al. is that existing reconstructions of the NH temperature of recent centuries may systematically underestimate the true centennial variability of climate and, If the true natural variability of NH [northern hemisphere] temperature is indeed greater than is currently accepted, the extent to which recent warming can be viewed as unusual would need to be reassessed.


In an interview with the German newspaper Der Spiegel, von Storch commented, We were able to show in a publication in Science that this [hockey stick] graph contains assumptions that are not permissible.  Methodologically it is wrong: rubbish.  Von Storch also pointed out the IPCCs role in cutting off questioning on the subject: It remains important for science to point out the erroneous nature of the Mann curve.  In recent years it has been elevated to the status of truth by the U. N. appointed science body, the Intergovernmental Panel on Climate Change (IPCC).  This handicapped all that research which strives to make a realistic distinction between human influences and climate and natural variability.


Von Storch also commented on Manns defense of his now thoroughly discredited research.  His influence in the community of climate researchers is great, he said.  And Mann rejects any reproach most forcefully.  His defensiveness is understandable.  Nobody likes to see his own child die.  But we must respect our credibility as research scientists.  Otherwise we play into the hands of those skeptics of global climate change who imagine a conspiracy between science and politics.

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