Thursday, December 22, 2011

1164059987.txt

From: Malcolm Hughes <mhughes@ltrr.arizona.edu>
To: Martin Juckes <m.n.juckes@rl.ac.uk>
Subject: Re: Bristlecone pines
Date: Mon, 20 Nov 2006 16:59:47 -0700
Cc: Keith Briffa <k.briffa@uea.ac.uk>

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Martin Juckes wrote:
> Hello Prof. Hughes,
>
> I'm involved in a discussion with Stephen McIntyre about Bristlecone pines,
> which I have used as temperature proxies in a recent work
> (http://www.copernicus.org/EGU/cp/cpd/2/1001/cpd-2-1001.htm).
>
> I've read the NAS report section on this issue, and most of the references
> cited in the paragraph about bristlecones. I'm unimpressed by the evidence
> presented to support the idea that these valuable records of past climate
> should be discarded. In particular, the most relevant study appears to be
> that of Bunn et al., and this clearly shows anomalous strip-bark growth
> occurring well before significant atmospheric CO2 rises. Their study used
> whitebark pine, which is clearly not the same as bristlecone, but perhaps
> closer than the orange trees cited by Graybill and Idso.
>
> I'm looking for further literature and if possible data on the issue. Do you
> know of any data on anomalous growth in bristlecone strip-bark pines which is
> available for analysis?
>
> sincerely,
> Martin Juckes
>
Dear Dr. Jukes,
I'm afraid that, apart from the Bunn et al 2003 paper you mention, I
know of no other recent literature or data directly relevant to this
question. There is a graduate student here working on a dissertation
related to this, but neither their data nor any publications on them are
available at the moment. Two points concerning Graybill and Idso (1993):
1) I don't think the sour orange trees used in Sherwood Idso's
experiments were stripbark - where did this idea come from? 2) When
considering the use of upper forest border bristlecone pine (e.g. Sheep
Mountain, Campito Mountain, and similar sites mainly above 3100m in the
relevant region) as temperature proxies it would be a mistake to
discount Figure 3 in Graybill and Idso (1993) which is a comparison of a
ufb bristlecone pine chronology with a smoothed gridpoint reconstruction
from maximum latewood density in quite different trees provided by Keith
Briffa, one of your co-authors. I read this graph as confirmation of
LaMarche's interpretation of the ufb bcp records as having a ~bidecadal
temperature signal combined with an interannual precipitation signal, at
least before the 20th century. This is referred to Hughes and Funkhouser
(2003).
I hope this helps, Malcolm Hughes
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