To: Tim Osborn <firstname.lastname@example.org>, "Tett, Simon" <email@example.com>
Subject: Re: Bristlecones!
Date: Fri Jul 29 16:30:35 2005
Cc: Keith Briffa <firstname.lastname@example.org>
If you go to this web page
You can click on a re-evaluation of MBH, which leads to a paper submitted
to Climatic Change. This shows that MBH can be reproduced. The R-code
to do this can be accessed and eventually the data - once the paper has been
IPCC will likely conclude that all MM arguments are wrong and have
been answered in papers that have either come out or will soon. MBH
is just one curve of many - more now than there were in 2001. MBH is
still in the spaghetti of curves, and is not an outlier. If there are outliers
it will be Esper et al. and another one.
Bristlecones are only crucial to the issue if you are MM. They misused
them, by their PCA application. This is all well-known to those in the know.
I have reviewed the CC paper by Wahl and Ammann. It reproduces all
the mistakes MM have made, so they know how and why their results
have been achieved. I can send you the paper if you want, subject
to the usual rules.
MBH have all responded to the same requests as IPCC got from the
US Senate. Their responses are all posted at http://www.realclimate.org/
The skeptics have shot themselves in the foot over this one.
At 15:17 29/07/2005, Tim Osborn wrote:
At 14:27 28/07/2005, Tett, Simon wrote:
John Houghton is being quized by bits of the US senate. One question is
"Whats the status of the review of the Mann hockey stick temperature
curve? I understand that studies by Stephen McIntyre and Ross McKitrick
suggest that it relied on the statistically insignificant bristlecone
pine. Is the IPCC taking another look at that work, which forms the
basis for much of todays climate change debate?"
My current thoughts on an answer is to say that other reconstructions
show a similar pattern (though not magnitude). However how many of the
other reconstructions use the bristlecone data? [I suspect yours does
Hi Simon - I was away yesterday, so couldn't answer then. Hopefully it isn't too late
to answer today.
(1) I don't understand what they mean by describing the bristlecone pine as
(2) The Mann, Bradley and Hughes (MBH1999) reconstruction is only one small piece of
information in today's climate change debate.
(3) As far as I understand, then yes the MBH1999 reconstruction does give quite a lot of
weight to a few western US tree-ring series, which are mostly bristlecone pines for the
(4) Other reconstructions show similar shape (though not magnitude) and support similar
conclusions (regarding the unprecedented nature of recent warmth/warming trend). This
is the main argument to make, as you thought. Some of these other reconstructions do
not include these bristlecones (e.g. Briffa, 2000; Crowley et al., 2003; Moberg et al.,
2005; Briffa et al., 2001). Crowely and Moberg use different Bristlecone records I
think. Other reconstructions do use the same Bristlecone pines (e.g., Mann and Jones,
2004). BUT the critical thing is that the studies either do not use these Bristlecone
pines, or if they do use them, then they give them much more similar weighting to the
other records used. I think MBH1999 is the only one that might give them a dominant
(5) IPCC is assessing all published work that relates to these issues in preparation for
the AR4 in 2007. This includes the McIntyre and McKitrick papers as well as papers that
report results contrary to McIntyre/McKitrick, such as the paper in press by Wahl and
Amman that shows the Mann et al. results are reproducible.
cc'd for additional comments to Phil and Keith (when he's back).
Dr Timothy J Osborn
Climatic Research Unit
School of Environmental Sciences, University of East Anglia
Norwich NR4 7TJ, UK
phone: +44 1603 592089
fax: +44 1603 507784
Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email email@example.com