date: Sun, 18 May 2008 11:13:23 +0100
from: Rob Wilson <rjsw@st-andrews.ac.uk>
subject: Re:  A General Call for Input to a Meeting on Palaeoclimate
to: Keith Briffa <k.briffa@uea.ac.uk>

   Hi Keith,
   will keep this as short as possible as you could be inundated with all sorts of replies.
   Rosanne has already sent you divergence related info. I think the only thing I would add is
   that the 'divergence' issue should really only be addressed and examined for those TR proxy
   series which have a strong relationship with climate. I was recently at the TRACE meeting
   in Poland and everybody was seeing divergence, but when the TR records only correlate at
   ~0.4 with some climatic variable, it all comes a bit academic and meaningless. Many of the
   RW chronologies in Alaska which `show' divergence are really only weak temperature proxies
   at best even in the period prior to divergence. This has become a bit of a bandwagon which
   was never my intention.
   So - areas where I think dendroclimatologists should focus:
   1. We need to specifically move on from the concept that "15 trees are enough". If at all
   possible we should try and encourage people to sample as much as possible and not be afraid
   to try and go for more than 50 series/trees per year. Of course this will not always be
   possible/easy when extending living material with historical/sub-fossil material, but there
   is no reason to restrict ourselves to only relatively few trees in the living period. High
   replication will help us overcome signal to noise issues as well as limitations in
   detrending etc.


   2. Some sort of strategic update of the large scale networks (Schweingruber's being the
   best example) is needed. Many of the important chronologies around the Northern Hemisphere
   need to be brought up to present. This will result in addressing potential calibration
   issues in the recent period, but also ensuring that resulting reconstructions will also
   extend to present.

                   Also - where possible - for those key sites (e.g. Tornetrask etc) which are
   always used in NH recons for example, some sort of validation is needed of their long term
   trends. Hakan Grudd's recent update of Tornetrask, I think, is no more believable than the
   original version (I am not saying this in a negative way - it just needs some validation).
   It would be much better to develop another similarly long TR record from a neighbouring
   climatologically similar region to check long term trends. The Alpine example is a good
   example of this where multiple independent TR series have now been developed which all
   basically show the same story.


   3. A better sampling of different age classes within a stand. At the very least, I think we
   should sample both young and old trees at a site. This will facilitate the use of
   detrending methods such as RCS as well as allowing for analyses to test for age dependent
   relationships.


   4. In the context of large scale millennial length reconstructions, we need to target
   regions where no long 1000+ year TR record exists (as well as updating existing ones!). We
   may not entirely agree on this, but I feel that much more good quality data are needed for
   better estimates of NH temperatures - especially during the MWP. Also, if we really want
   better spatial information we must increase the density of the current NH network. For
   example - there are no 1000+ year long records between the Yukon and Labrador - surely we,
   as a community, can fill this gap?


   5. Although RW data is a nice cheap proxy, more often than not, the climate signal is not
   as strong as we would like. We need to encourage labs to also measured density (or possibly
   the related blue reflectance measure) where possible. For example - Greg Wiles is sitting
   on a 1500+ year long highly replicated composite for coastal Alaska and no density work has
   been done on this material. I believe Dave Frank may have started negotiations in this
   direction though.


   6. Isotopes. I am watching results from ISONET and MILLENNIUM closely. My gut feeling is
   that in those regions and for those species where traditional RW/MXD do very well, stable
   isotopes do not provide any more useful information. However, there are encouraging results
   in areas where traditional approaches provide no information, where isotopes may indeed
   allow some sort of climatic interpretation. For example - temperature data from C and O
   isotopes measured from Oak samples in Northern Britain etc.


   7. We should not assume that the early instrumental record is robust. The recent work in
   the Alpine region with Reinhard Bohm et al. shows how TR proxy records could at least help
   identify homogeneity issues in climate records. Of course, we need to have `faith' in the
   proxies, but with more replication, multiple sites etc, I think this should not be a
   problem given time.


   8. Finally, w.r.t. to NH reconstructions, individual constituent TR chronologies should be
   assessed for their `climatic relevance' at the local scale ONLY - i.e. they are robust
   estimates for local/regional climate. It does NOT matter how they correlate with large
   scale NH temperatures. The Jacoby/D'Arrigo principle of only looking for those series that
   express some sort of mythical large scale signal is wrong and biased. Gaspe is a good
   example of this. Do not pass this on to Gordon/Rosanne. :-)


   Anyway - hope the comments are of some use

   Regards

   Rob
   Keith Briffa wrote:

     A General Call for Input to a Meeting on Palaeoclimate Uncertainties
     PLEASE NOTE - this message has been sent to a representative selection of those working
     in different tree-ring laboratories - please forward to those of your colleagues who
     would be interested - THANK YOU

     Dear Colleagues,

     I have been tasked with drafting the `White paper' in the general topic of `Reducing
     Uncertainties', in my case with a focus on tree-ring data. This is meant as the basis
     for discussion at a wider meeting dealing with various high-resolution proxy data, being
     held in Trieste funded by PAGES/CLIVAR.

      Hence I am asking for specific input from any of those among you who wish to contribute
     specific points or stress, even briefly or as concepts, areas of concern regarding
     present work or future requirements.

     The context is general dendroclimatology and the use of tree-ring-derived climate
     reconstructions specifically for establishing the precedence of instrumental
     observations in a recent multi-millennial context.

     The specific issues I have been asked to address include:

     1)      sources of climate interpretational uncertainty - how can this be quantified and
     represented?

     2)      strategies for reducing these uncertainties?

     3)      database / data archiving needs and ideas?

     The `white paper' is only intended to be several pages long - so specific ideas,
     concerns etc. along the lines indicated, would be very welcome. I would then try to
     condense them and draft the text.

     I must complete this task in the next 2 weeks - so brief, initial thoughts and points
     that you consider must be included would be most welcome.

     At present Ed Cook ,Rosanne D'Arrigo and Dave Frank are included among the participants
     ( Congratulations to Jan Esper on the recent arrival of a brace of beautiful girls -
     provided they take after their mother that is) and I would particularly hope for input
     from them - but I know it is vital to get wider input from others working in this area
     of dendroclimatology - or who have real concerns with the issue of climate change
     detection and attribution and the use of tree-ring data for model validation or work
     aimed at quantifying transient climate sensitivity in the real world.

     Any thoughts, specific text or important PowerPoint slides would be most welcome.

     With very best wishes and thanks

     Keith Briffa
     15^th May 2008

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

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

--
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Dr. Rob Wilson
Lecturer in Physical Geography
School of Geography & Geosciences
University of St Andrews
St Andrews. FIFE
KY16 9AL
Scotland. U.K.
Tel: +44 01334 463914
Fax: +44 01334 463949

[2]http://www.st-andrews.ac.uk/gg/people/wilson/

".....I have wondered about trees.

They are sensitive to light, to moisture, to wind, to pressure.
Sensitivity implies sensation. Might a man feel into the soul of a tree
for these sensations? If a tree were capable of awareness, this faculty
might prove useful. "

"The Miracle Workers" by Jack Vance
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