Friday, June 15, 2012

5203.txt

cc: Scott Rutherford <srutherfordatXYZxyz.edu>, mannatXYZxyzginia.edu
date: Tue, 20 Jan 2004 07:58:56 -0500
from: "Michael E. Mann" <mannatXYZxyzginia.edu>
subject: Re: J. Climate paper - in confidence
to: Keith Briffa <k.briffaatXYZxyz.ac.uk>, "Malcolm Hughes" <mhughesatXYZxyzr.arizona.edu>, "Malcolm Hughes" <mhughesatXYZxyzr.arizona.edu>, Tim Osborn <t.osbornatXYZxyz.ac.uk>

Thanks Keith,
I agree w/ this--I think the Vaganov chronologies were pretty heavily standardized, and the
other issues you raise are important. In the future, we would (and will) be a bit more
circumspect about the use of some of these data.
In the present case, however, I think we are forced to use the exact same network.
Re, the omission of some results. I think we can probably keep them. Simply by cleaning up
the text, removing redundancy, etc. I've shortened and tightened the manuscript
considerably, and I think I've improved the logical flow a bit in the process. So my
feeling is that we will not have to split this up, but I'll leave this to all of you to
decide after you see the revised draft from Scott and me...
Thanks,
mike
At 09:45 AM 1/20/2004 +0000, Keith Briffa wrote:

Malcolm seems to have done a good job sorting out these constituent sets , and I don't
have anything to add other than agreeing that as a general principal , where possible,
original chronologies should be used in preference to reconstructed temperature series (
the latter having been already optimized using simple or multiple regression to fit the
target temperature series ). This applies not only to our western US reconstructions
(which it should be stressed are based on very flexible curve fitting in the
standardisation - and inevitably can show little variance on time scales longer than a
decade or so) but also to the Tornetrask and Polar Urals reconstructions (each of which
was based on ring width and density data , but standardised to try to preserve
centennial variability - though the density series had by far the largest regression
coefficients). There is though a question regarding the PCs of the Siberian network
(presumably provided by Eugene?) . The correlation between density and ring width can
get high in central and eastern parts of the network , so even though these are
different variables , it might not be strictly true to think of them as truly
independent (statistically) of the density chronologies we use from the Schweingruber
network ( there may also be a standardisation issue here , as the density chronologies
were standardised with Hugershoff functions for our initial network work (as reported in
the Holocene Special Issue) whereas your PC amplitudes may be based on "Corridor
Standardisation" - which likely preserves less low frequency? ) .
These remarks are simply for clarification and discussion , and I too will wait on your
response draft , though I would throw in the pot the fact that omitting the time
dependent stuff would simplify the message at his stage.
cheers
Keith
At 01:42 PM 1/19/04 -0700, Malcolm Hughes wrote:

Mike - there are the following density data in that set:
1) 20 Schweingruber/Frttss series from the ITRDB (those that
met the criteria described in the Mann et al 2000 EI paper)
2) Northern Fennoscandia reconstruction (from Keith)
3) Northern Urals reconstruction (from Keith)
4) 1 density series for China (Hughes data) and one from India
(also Hughes data) - neither included in Keith's data set, I think.
5) To my great surprise I find that you used the Briffa gridded
temperature reconstruction from W. N. America (mis-attributed
to Fritts and Shao) - of course I should have picked up on this 6
years ago when reading the proofs of the Nature sup mat. It was
my understanding that we had decided not to use these
reconstructions, as the data on which they were based were in the
ITRDB, and had been subject to that screening process. So
depending on whether you used the long or the shorter versions
of these, there will have been a considerable number of density
series included , some of them twice. It means that there is
considerably more overlap between the two data sets, in North
America, than I have been telling people. I stand corrected.
Cheers, Malcolm
.
.Malcolm Hughes
Professor of Dendrochronology
Laboratory of Tree-Ring Research
University of Arizona
Tucson, AZ 85721
520-621-6470
fax 520-621-8229

--
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/

______________________________________________________________
Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
_______________________________________________________________________
e-mail: mannatXYZxyzginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137
[2]http://www.evsc.virginia.edu/faculty/people/mann.shtml

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