James Annan has heard from his eagle friends about further goings with Hegerl et al. Annan has heard from Tapil Schneider about how
Hegerl et al used a regression to estimate past temperatures anomalies as a function of proxy data, and estimated the uncertainty in reconstructed temperature as being entirely due to the uncertainty in the regression coefficient. The problem with this manifests itself most clearly when the tree ring anomaly is zero, as in this event the uncertainty in the reconstructed temperature is also zero! Steve McIntyre's plot of the data that Hegerl et al supplied as supplementary information illustrates the effect neatly (and the problem is quickly diagnosed in the comments following).Eli thought he had seen this before, and indeed he had,
in the discussion about Huang, Pollack and Shen's's boring hole long term global temperature reconstructions that were later commented on by the Fuzzy Blogger's Group Blogfather, Stoat. Stoat got an explanation from Pollack on the differences between different versions of their reconstructions which casts considerable doubt about the one above. Of course, the one above also was a favorite of Lord help us Monckton which is what made us twitch our noses in the first place when he blew the first 1K year section up.
1600 is clearly a point of zero anomalie. Huang, Pollack and Shen do not quite have "isobestic points" in their confidence limits, but close enough to imagine the same mistake has been made. Monckton is, of course, a point of infinite error.