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Everything You Know About Climate Proxies May Be Wrong

Andrew Montford, Bishop Hill

Well, well. Look what Steve McIntyre has found. After all those years of sceptics calling for tree-ring series to be updated so as to provide out-of-sample validation of their effectiveness as proxies, and all those years of mainstream climatologists telling us how this couldn’t happen because of the cost and difficulty, one of the key series in the Hockey Stick and many other temperature reconstructions has finally been brought up to date.

The series in question is Sheep Mountain, prominently featured in The Hockey Stick Illusion as having a hockey stick shape, the blade of the stick allegedly tracking the rise in northern hemisphere temperatures up to 1980, the end of the Hockey Stick reconstruction. Since 1980 we had another 18 years of temperature rises followed by a decade and a half of the pause.

So what has been happening to tree rings on Sheep Mountain been doing in that time? As McIntyre explains, we already knew about the first few years, because Donald Graybill, who collected the original data, did so in 1987.

The original Graybill Sheep Mountain chronology ended in 1987 (rather than 1980) and, though little discussed previously, actually declined quite sharply in the 1980s.

And now that hint of problems being swept under the carpet has been brought out into the open. The update, by Salzer et al, comes in the form of two different updates to the Sheep Mountain record – the northern and southern series (NFa and SFa):

The updated Salzer SFa chronology…shows a dramatic decline from the closing values of the series used in Mann et al 1998.  While the Salzer NFa chronology…  is slightly elevated relative to the SFa chronology and to the millenium mean, its values are also much lower than closing MBH98 values of the Graybill chronology. Both diverge dramatically from the NH temperature. To have kept pace, SFa and NFa chronology values ought to have reached nearly 3, while the SFa chronology has almost reverted to the long-term mean, with several recent values actually below the long-term mean. Perhaps this accounted for the interest in looking at north-facing exposure separately.

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