Here is the ‘spaghetti graph’ of a number of prominent reconstructions, with two-sigma confidence interval. The CRU calibration temperatures are the solid black line. Can you find the random reconstruction? (Thanks to Steve McIntyre at http://www.climateaudit.org/?p=566 for recon data.)
Here I am just applying the same red noise technique to the â€™select and averageâ€™ method in use by many including Esper et.al. prior to MBH98 Principle Components method examined in detail in MM05 (see http://www.climateaudit.org/?p=110). McIntyre quoting Hughes at the NAS meeting:
Hughes said that there were two main ways of temperature reconstruction using tree rings: 1) the Schweingruber scheme â€“ choose sites to be temperature sensitive. (The Schweingruber sites are the ones in the Briffa network that decreases in the second half 20th). 2) The â€œFrittsï¿½? scheme: many records are put in the network, which are â€œempirically disentangledï¿½? using methods like PCA.
Looking at it, it seems there might be a valid approach to finding a signal by getting the expectation of the shape of the random reconstructions and testing for deviations from that. Eg. The recons suggest that there might be a significant broad dip in temperatures from 1600-1700 (LIA). This however is the only significant signal I would think you would find.
Before doing any signal analysis, one should determine the detection limits of the methodology. Just looking at I would think that 0.5 degrees would be a good guess – so maybe the consensus of the NAS panel that estimates of past temperature are only accurate to 0.5 degrees could be right. Where does that put claims that the last centuries 0.6 degree rise was anomolous, or unusual? Just my ideas for a couple of constructive quantifications.
Esper et al. (Cook, Krusic, Peters, Schweingruber) from Tree Ring Res. 2003, p.92,