From: Phil Jones <p.jones@uea.ac.uk>
To: Tim Osborn <t.osborn@uea.ac.uk>, "Tett, Simon" <simon.tett@metoffice.gov.uk>
Subject: Re: Bristlecones!
Date: Fri Jul 29 16:30:35 2005
Cc: Keith Briffa <k.briffa@uea.ac.uk>

    Simon,
       If you go to this web page
    [1]http://www.ucar.edu/news/releases/2005/ammann.shtml
    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
    accepted.
       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 [2]http://www.realclimate.org/
       The skeptics have shot themselves in the foot over this one.
    Cheers
    Phil
   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
     not]

     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
     "statistically insignificant".
     (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
     longest records.
     (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
     weighting.
     (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).
     Cheers
     Tim
     Dr Timothy J Osborn
     Climatic Research Unit
     School of Environmental Sciences, University of East Anglia
     Norwich  NR4 7TJ, UK
     e-mail:   t.osborn@uea.ac.uk
     phone:    +44 1603 592089
     fax:      +44 1603 507784
     web:      [3]http://www.cru.uea.ac.uk/~timo/
     sunclock: [4]http://www.cru.uea.ac.uk/~timo/sunclock.htm

   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    p.jones@uea.ac.uk
   NR4 7TJ
   UK
   ----------------------------------------------------------------------------

References

   1. http://www.ucar.edu/news/releases/2005/ammann.shtml
   2. http://www.realclimate.org/
   3. http://www.cru.uea.ac.uk/~timo/
   4. http://www.cru.uea.ac.uk/~timo/sunclock.htm

