It seems to me that to meet IPCC precondition for coherence, datasets with a low signal to noise ratio in terms of temperature were enhanced in an attempt to extract coherent data. This is at best, risky and in this case disastrous. Although this data set is only causally connected to others, the entire process is brought into question.

“The bottom line though is that these trees likely represent a mixed temperature and moisture-supply response that might
vary on longer timescales.”…

“Another serious issue to be considered relates to the fact that the PC1 time series in
the Mann et al. analysis was adjusted to reduce the positive slope in the last 150
years (on the assumption – following an earlier paper by Lamarche et al. – that this
incressing growth was evidence of carbon dioxide fertilization) , by differencing the
data from another record produced by other workers in northern Alaska and Canada
(which incidentally was standardised in a totally different way). This last adjustment
obviously will have a large influence on the quantification of the link between these
Western US trees and N.Hemisphere temperatures. At this point , it is fair to say that
this adjustment was arbitrary and the link between Bristlecone pine growth and CO2 is ,
at the very least, arguable. Note that at least one author (Lisa Gaumlich) has stated
that the recent growth of these trees could be temperature driven and not evidence of
CO2 fertilisation.
I stil believe the “Western US” series and its interpretation in terms of Hemispheric mean
temperature is perhaps a “Pandora’s box” that we might open at our peril!
What does Jan say about this – he is very acquainted with these issues?
cheers
Keith”

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