date: Thu Jun  5 14:06:36 1997
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: Your paper
to: drdendro@ldgo.columbia.edu (Edward R. Cook)

Ed,
  many thanks indeed for your comments. I agree about the carbon sequestration emphasis and to be honest I would be happy to tone that down or leave it out - the truth is that this was meant as a possible lead into a later paper on the increasing biomass on the longer term. We are ahead of you on the rotated PCA of the effect and in factoring out the decline in the density data by identifying it in a analysis of the rotated PCs. This stuff is for a more detailed (some would say scientific) paper - but is too detailed for a first (wider appeal!) description of the phenomenon. I too agree that soil moisture stress must play some part in this but I do not believe we have unprecidented conditions (summer precip. or temp) that explain this without the need to invoke a new synergistic effect - nitrate/CO2/UVb or whatever. This effect - and particularly in the density , is I believe real and important.
   I appreciate Gordon's comments too - but the effect is a valid signal even when identified on these spatial scales. We are justified in drawing attention to it and following up with a detailed analysis. For once I think this deserves the audience of a Nature paper which is why it will probably be rejected!
We need you to do some work with us on this and I still want to get the means of doing this sorted. Please let us make it happen.
                                                 Keith

At 08:54 05/06/97 -0400, you wrote:
>Hi Keith,
>
>I got your draft paper from Gordon, with his comments, and read it. It
>reads pretty well. I would have emphasized things a bit differently, but
>it's all a matter of taste. For example, I wouldn't have mentioned the
>carbon sequestration thing, or at least would not have made it an important
>issue. Rather, I would have emphasized the possible large-scale degradation
>of a globally significant biome (or maybe ecotype, i.e. temperature-limited
>trees), which is highly significant whether or not it relates in any
>meaningful way to changes in carbon sequestration. I read Gordon's comments
>and talked with him a bit about it. He is beating his usual
>anti-Schweingruber drum in reference to lumping large swaths of data
>without taking account of site differences. But he even admits, in his
>written comments to you anyway, that it is a useful way to go as a first
>cut in documenting the problem.
>
>Obviously, there are numerous ways to proceed with the analyses that would
>answer many of the questions and criticisms that Gordon raises. It should
>be possible to more objectively regionalize the data using rotated EOF
>analysis. That would, perhaps, blunt that criticism. Also, doing the high
>and low-pass filtering should enable one to indirectly determine the degree
>to which a change in climate response (say temperature to moisture) is
>involved. I am sure that Gordon is right about some sites have increasing
>moisture stress, but I doubt that that is the main cause, or even one that
>is of any significance in a large-scale sense. The main hypotheses I favor
>are (not necessarily in order of importance): Arctic haze, excessively high
>temperatures, and UV-B. However, I do favor the first two above UV-B.
>"Maybe I don't know" (a Nepali saying).
>
>Cheers,
>
>Ed
>
>
>
>