Friday, May 18, 2012

4401.txt

date: Mon Jun 2 13:28:58 2008
from: Keith Briffa <k.briffaatXYZxyz.ac.uk>
subject: Fwd: Re: A General Call for Input to a Meeting on Palaeoclimate
to: drdendroatXYZxyzo.columbia.edu

Date: Mon, 02 Jun 2008 13:27:48 +0100
To: Rob Wilson <rjswatXYZxyzandrews.ac.uk>
From: Keith Briffa <k.briffaatXYZxyz.ac.uk>
Subject: Re: A General Call for Input to a Meeting on Palaeoclimate Uncertainties
Rob
I agree with virtually everything you say - thanks. I will not be at the meeting now as
Amy , my daughter is ill , but will forward this on (I think virtually all points are
covered in my brief notes to Ed anyway) to ED and Dave Frank who will be leading the
tree-ring discussion in my abscence. Cheers
Keith
At 11:13 18/05/2008, you wrote:

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 (Schweingrubers 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 Grudds 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.

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/

--
-----------------------------------------------------------------------
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
-----------------------------------------------------------------------

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

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

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

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

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