I noticed the following quote from Esper et al 2003 (reference in earlier post
It is important to know that at least in distinct periods subsets of trees deviate from common trends recorded in a particular site. Such biased series represent a characteristic feature in the process of chronology building. Leaving these trees in the pool of series to calculate a mean site curve would result in a biased chronology as well. However if the variance between the majorities of trees in a site is common, the biased individual series can be excluded from the further investigation steps. This is generally done even if the reasons for uncommon growth reactions are unknown.
I posted up the next quote from Esper previously, but it’s worth repeating in the present context:
However as we mentioned earlier on the subject of biological growth populations, this does not mean that one could not improve a chronology by reducing the number of series used if the purpose of removing samples is to enhance a desired signal. The ability to pick and choose which samples to use is an advantage unique to dendroclimatology.
These statements just make my jaw drop. If the information at a site level is being fiddled with (“adjusted”) in the way that Esper indicates here (and in my opinion, it would be a worthwhile investigation for someone to check whether it is – and not just from the bosses), how can you ever rely on anything? If the field workers know that the boss has a "signal" in mind and their methods do not require 100% of the data to be recorded, you have biases way beyond D’Arrigo cherry picking individual sites. Maybe I’m just interpreting injudicious comments in an adverse light, but the comments are hugely inappropriate for authors of studies being relied on by IPCC and policy-makers and deserve to be looked into.