In any environmental or sociological study there are always worries about hidden factors, etc. (and limits to how many you can check.) The issue wrt Mann is to address their seriousness (within the grownups world of knowing this common concern). Not run around prattling 3 unknowns/2 equations like a simpleton.

I assume it’s ok to hit Dave, while letting Sid slide for 10 posts. Most sites I hang out at, I am the pet troll and allowed to be disruptive (double standard).

I’m thinking about another sabbatical or cutting back to weekly comments…

I’m going to post up on upside-down quadratics. We observed this in passing in our E&E article. The point seems so obvious and so unarguable that it’s remarkable that policy continues to be driven by tree rings.

When you add in the precipitation issues, it becomes like Monty Python. Half the proxies in MBH98 which are supposely temperature proxies are used in Cook et al [2004] as precipitation proxies.

As an aside to the above, the Graybill-Idso sites may in fact have a linear temperature response, it is just that the CO2 or other response is stronger. So perhaps the reason sites should be rejected is not because they fail to meet MBH98 inadequately stated assumptions of linearity, but should be rejected because of a confounding factor.

Nevertheless, the conditions for success of tree ring proxies are much stronger than stated. It is not clear what the restated assumptions regarding linearity to one or more instrumental training patterns would entail, or if it is even a weaker condition than proxies following a linear temperature response. What I am saying is that irrespective of other flaws and problems of this particular study, the use of treegrowth as a proxy seems to be a very poorly specified model, that could only succeed under very limited conditions and would explain the general mess that the data show.

Under MBH98 methodology, 16 overweighted sites (out of 70) account for virtually all the North American PC1 variance. All were high-altitude sites, mostly with cambial dieback (“strip-bark”) formation, showing very high 20th century growth rates. An unreported MBH98 calculation5, studying exclusion of these 16 and four other high-altitude sites, yielded a PC1 nearly identical to ours (Figure1c – correlation=0.95). 15 of these sites were collected by the same researcher (Donald Graybill). Graybill and Idso6 stated that their nonlinear growth rates could not be attributed to temperature and hypothesized direct CO2 fertilization. Hughes and Funkhouser7 called their growth rates a “mystery”. Mann et al.8 stated that their growth rates “are more dramatic than can be explained by instrumental temperature trends.” Since MBH98 methodology requires (p. 780) that proxies follow a linear temperature response, the Graybill-Idso sites should have been disqualified. Instead they were heavily overweighted.

Mann replied:

MM04 demonstrate their failure to understand our methods by claiming that we required that “proxies follow a linear temperature response”. In fact we specified (MBH98) that indicators should be “linearly related to one or more of the instrumental training patterns”, not local temperatures.

The idea that the Stahle/SWM network PC7 could have an intimate relationship with a temperatature PC11 is bizarre even for the Hockey Team, but that’s why they say.

“[MBH98] The indicators in our multiproxy trainee network are linearly related to one or more of the instrumental training patterns. In the relatively unlikely event that a proxy indicator represents a truly local climate phenomenon which is uncorrelated with larger scale climate variations, or represents a highly nonlinear response to climate variations, this assumption will not be satisfied.”