From: Eystein Jansen <Eystein.Jansen@geo.uib.no>
To: Keith Briffa <k.briffa@uea.ac.uk>
Subject: Fwd: Chpt 6 - last 1000 yrs
Date: Wed, 30 Aug 2006 21:43:25 +0200
Cc: Jonathan Overpeck <jto@u.arizona.edu>

   Hi Keith,

   John should have the latest versions of the comments file and the chapter text, i.e. the
   ones that went out for LA review this summer. I believe he is after some more specific
   answers in the comments and not so much changes to the text, and has selected the
   bristlecone issue, the divergency issue and the verification and robustness issues. If you
   are unsure what comments or tetx he refers to, I think the best thing is for to ask John
   for the specific comments he thinks are not adequate, or the specific lines of text which
   he suggests changed. It seems he needs some reassurance rather than you writing much new in
   terms of comments and text, so the best would be to talk to him and ask what he needs you
   to do to the documents.

   Best wishes,

   Eystein

     Envelope-to: Eystein.Jansen@geo.uib.no
     Date: Wed, 30 Aug 2006 15:31:12 +0100
     To: Eystein Jansen <Eystein.Jansen@geo.uib.no>

     From: Keith Briffa <k.briffa@uea.ac.uk>
     Subject: Fwd: Chpt 6 - last 1000 yrs
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     Eystein
     John sent these remarks - have not talked with him yet - but not sure what is now
     required
     Keith

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     Subject: Chpt 6 - last 1000 yrs
     Date: Wed, 16 Aug 2006 16:14:52 +0100
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     From: "Mitchell, John FB \(Chief Scientist\)" <john.f.mitchell@metoffice.gov.uk>
     To: "Keith Briffa" <k.briffa@uea.ac.uk>
     Cc: "Mitchell, John FB \(Chief Scientist\)" <john.f.mitchell@metoffice.gov.uk>
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     Hi Keith
     I have tried to cindense what I think the main issues for the and what the response is
     below. The weakest area seems to be statistical significance and by implication the
     likely/ very likely statements. I can't think of any easy solution - in the TAR for
     detection and attribution we used 95% limits on stats tests and them downrated them to
     allow for other uncertainties.
     I am interested in your comments
     John
     Issues
     1. Reliance on Bristlecone pine -
     Response - the issues are in calibration period- they agree with other indicators for
     the rest of the record
     2. Centring of principle components leads to "hockeysticks"-
     Response - this makes only a small difference when standardised data used.
     Comment - Would be useful to know which reconstructions do and donot make this
     assumption- this could strengthen the response
     3. The divergence issue-
     Response - it is only apparent in high latitudes, and only with some trees.
     Comment- Do we know what happens if we eliminate those records with a divergence
     problem. The wider issue is whether or not it is reasonable to extend the
     reconstructions outside the calibration range.
     4. There are different ways of verifying reconstructions and assigning significance
     levels( calibration period or seprate verifying period, different statistics)
     Response ?
     Comment- it is difficult in the text to gauge how well reconstructions are validated -
     eg using the calibration period to estimate errors as opposed to an independent period
     clearly makes a difference. This is important where "likely", "very likely"are used-
     based on what statistics? I think this is the area where I think the current response is
     weakest
     5. Robustness- Burger and Cubasch show a wide range of results using different
     assumptions-
     Response ?
     Mann makes a reasoned defence- there are other checks and tests which would rule out
     many of the arbitrary assumptions explored by Cubasch and Burger, but this is not clear
     in the response to M&M etc

     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.

     Phone: +44-1603-593909
     Fax: +44-1603-507784
      http://www.cru.uea.ac.uk/cru/people/briffa/

--

   ______________________________________________________________
   Eystein Jansen
   Professor/Director
   Bjerknes Centre for Climate Research and
   Dep. of Earth Science, Univ. of Bergen
   Allégaten 55
   N-5007 Bergen
   NORWAY
   e-mail: eystein.jansen@geo.uib.no
   Phone:    +47-55-583491  -  Home: +47-55-910661
   Fax:       +47-55-584330

