26 October 2009

A Point Resolved in the Hockey Stick Wars

Sometimes seemingly small disputes can tell you a lot. One of a what seems to be a bazillion points of dispute between Steve McIntyre and Michael Mann involves a claim by McIntyre that Mann mistakenly used a number of paleo-climate proxies upside-down. Mann replied by outright rejecting the claim:
The claim that ‘‘upside down’’ data were used is bizarre.
One of the challenges for observers of disputes about climate science is that they are often complicated, technical and nearly impossible to resolve without becoming an expert yourself. So generally people resolve them based on factors other than logic and data. In this case, it looks like this dispute will in fact be resolved unequivocally through the peer-reviewed literature, which for all of its faults, is the media of record for scientific claims and counterclaims.

Evidence pointing to a resolution of the dispute can be found in a newly released correction to a paper by the lead author (Kaufman) that was also claimed to have used proxy data upside-down. Kaufman has written a corrigendum which admits as much (here in PDF). McIntyre discusses the corrigendum today at his site. Here is an excerpt:
We pointed Mann's upside down use of the data (with a worse impact than on Kaufman) in the correct channels. Mann denied it. Once the matter is pointed out, it's not rocket science to determine who was right, but PNAS took no steps to resolve the contradiction. realclimate readers took Mann's denial as being proof that he didn't use it upside down . . . While Kaufman has admitted using the data upside down, Mann hasn't.
On this issue at least it seems that we can now resolve who's claims were correct and who's weren't.