The Hegerl et al 2006 climate reconstruction is finally online here . I’m going to go through the proxies individually before talking about method. Obviously the first one to look for is Mann’s North American PC1. Although they say that they’ve “moved on”, Mann’s PC1 was used in Osborn and Briffa 2006 and was one of my predictions when I tried to guess what proxies were used in Hegerl et al.
There is no mention of principal components whatever in Hegerl et al. They state that they used a western U.S . tree ring series, but clearly avoid any reference to principal components or bristlecones. They state:
western U.S.: this time series uses an RCS processed treering composite used in Mann et al. (1999), and kindly provided by Malcolm Hughes, and two sites generated by Lloyd and Graumlich (1997), analyzed by Esper et al. (Boreal and Upper Wright), and provided by E. Cook. The Esper analyses were first averaged. Although there are a number of broad similarities between the Esper and Hughes reconstructions, the correlation is only 0.66. The two composites were averaged.
Their Figure A1 shows that this proxy is available in 500- well before the start of MBH99 in 1000. MBH99 made no mention of the use of “an RCS processed treering composite”. Hegerl et al make no mention of Mann’s PC1 – and after all the publicity, you’d think that they’d make sure to mention any use of this controversial proxy. Here’s their series labeled as “w U.S.A. – Hughes”.
Fig 1. Excerpt from Hegerl et al 2006 Figure A1
Now for comparison, here is a smoothed version of Mann’s PC1 from Mann and Jones 2003. Look familiar?
Fig 2. Re-plot of Mann and Jones PC1, with 21 year gaussian smooth.
Finally, for good order’s sake, here’s a plot of the Western U.S. series from Osborn and Briffa 2006, using their smooth as archived.
Fig 3. Plot of western U.S. series from Osborn and Briffa 2006.
I think that we can safely conclude that Hegerl et al 2006 used Mann’s PC1 and have incorrectly described what they used. How on earth could they have accidentally mis-described this series? It’s not as though Gabi Hegerl is unaware of the issues pertaining to Mann’s PC1. She was at the NAS Panel for example.
In terms of my predictions of what Hegerl et al 2006, I’m scoring this 1 for 1 so far. I’ll keep going through my predictions individually over the next few days.