Flipping bizarre
Feb 6, 2010
Bishop Hill in Climate: HSI, Climate: Mann

An interesting little development on one of the story lines from The Hockey Stick Illusion. In Chapter 14, I tell the story of one of Michael Mann's later attempts at creating a hockey stick shaped temperature curve - Mann 2008. This paper is not as well-known as the Hockey Stick itself, of course, but has become fairly notorious because of an oddity in Mann's algorithm. Because of the way it works, the algorithm is unable to detect the orientation of the proxy series in a dataset and in the case of Mann 2008, this failing had some unfortunate consequences, namely that some of the series ended up upside-down, with what would normally have been read as declining temperatures flipped over so that they looked like warming.

This error was picked up extremely quickly by Climate Audit readers, and McIntyre included this point in a formal comment on the paper. The correction didn't, however, prevent an identical error being made in a later paper, Kaufman 2009, which was written by some of the same authors as Mann 2008 (although not the HockeyStickMeister himself).

McIntyre's comment was accepted for publication but received a brief dismissal from Mann et al, who said that his observation was "bizarre".

Now, however, the story has moved on slightly. Kaufman has admitted the error in his paper and has just published a correction (although without mentioning McIntyre). Interestingly though, some of the Scandinavian scientists involved in collecting the original data series have revealed that they have been discussing the problem with Raymond Bradley, an author on both the Mann 2008 and Kaufman 2009 papers. Bradley, it seems, has told Professor Matti Saarnisto that the error was not deliberate, an explanation that the Finn is trying hard to accept.

Well, when Bradley says so to me, I don’t doubt even a slightest moment. I hold him in high regard. He is one of the best paleoclimate researchers, and … a frequent visitor in Finland.

Well, absolutely, but with the same error happening again and again, one does start to wonder. Certainly Saarnisto seems troubled.

It has been turned twice upside-down in Science, and now I doubt if it can be a mistake anymore.

It's fair to say that this position is probably widely shared. Lady Bracknell might have something to say about this: "To flip one proxy series may be regarded as a misfortune, Dr Bradley, to flip two...." And in fact the error has been observed no less than three times now. One hates to think what Lady Bracknell would think of that.

But if this isn't bad enough, there's an even sharper sting in the tail. If Bradley, one of Mann's co-authors on the 2008 paper, says the error was inadvertent, how is it that when he and Mann responded to McIntyre's comment on that paper, they described the idea that some of the proxies were upside down as "bizarre"?

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