Sunday, May 6, 2012

3865.txt

cc: Scott Rutherford <srutherfordatXYZxyz.edu>, mannatXYZxyzginia.edu
date: Mon, 19 Jan 2004 16:34:02 -0500
from: "Michael E. Mann" <mannatXYZxyzginia.edu>
subject: Re: J. Climate paper - in confidence
to: "Malcolm Hughes" <mhughesatXYZxyzr.arizona.edu>, Tim Osborn <t.osbornatXYZxyz.ac.uk>, Briffa Keith <k.briffaatXYZxyz.ac.uk>

Thanks Malcolm,
Fair enough--in future work, we can eliminate the redundant predictors, such as trd.dat
(which is just, as you say, a single regional mean as estimated by Ray and Phil backn in
'93). But for the purposes of this paper, the network should be the MBH98 network, so we
need to keep these. Of course, keeping them or eliminating them doesn't even make a dent in
the 3rd decimal place, I can assure you. Will go w/ the number 22. So 22/415 = 5% of our
predictors were in common w/ the MXD network--we can call that "nearly independent", but
note the small number of common predictors.
A revised draft of the J. Clim for all to comment on should be available soon...
Thanks again,
mike
At 02:37 PM 1/19/2004 -0700, Malcolm Hughes wrote:

Hi Mike - I'd forgotten the connection with the BJ93 paper. I'm
working at home today (university closed for MLK day), so it
will be tomorrow before I can check a couple of things. Both the
Fritts and Shao gridded reconstructions from ring width (and the
density based one attributed to them) were gridded
recosntructions based on many chronologies. When reading the
supmat today, I assumed that these were what was used. From
what you say I assume that Ray and Phil must have made some
regional means out of these rather than using the gridpoints
directly?
Anyway, we shouldn't include the two Western North America
series in question (Dendro ring widths air temp 39N
111W 1602 Fritts & Shao 1992) or (Western North America
Dendro density air temp 39N 111W 1600 ") in
anything we do now or in the future if we are also including the
original chronologies on which they were based in our screening
(as we did).
Apart from this (i.e. the trd.dat series is entirely based on Keith's
reconstruction using density data) the only Briffa/Schweingruber
data explicitly used were 20 from the ITRDB (with the 'x' suffix,
plus the Fennoscandia and Polar(northern) Urals, i.e. 22 series.
CHeers, Malcolm
.
..
On 19 Jan 2004 at 15:59, Michael E. Mann wrote:
> Malcolm,
>
> series (5) is 'trd.dat', a Bradley & Jones (93) series.BJ93 was of
> course the nucleus of the MBH98 network, which was constructed by
> adding other indicators to that initial dataset. Of course, that does
> imply some redundancy, since many of the BJ93 series were composites
> of other data, etc. I might have gotten the reference from BJ93 for
> trd.dat wrong (Fritts and Shao is for correct for trw.dat, but perhaps
> not trd.dat, right?). I don't have BJ93 w/ me? What reference does it
> give for trd.dat? Scott should fix this in the revised MBH98 data
> list:
>
> [1]ftp://holocene.evsc.virginia.edu/pub/sdr/temp/nature/MANNETAL98/PROXY/
> mbh98dat asummary.txt
>
> In any case, this hardly constitutes "considerably more overlap". This
> represents 1 series/indicator out of 415 series/112 indicators used.
>
> So, in total, there are 24 density series used out of a total of 415
> proxy indicators, in the MBH98 network. Its fair to say this comprises
> a "very small fraction" of the network, but of course we must be
> careful to point out that the two networks are therefore not entirely
> independent. I will modify the wording in the paper accordingly.
>
> One final question, was each of the 24 density series in question
> actually used in the Briffa et al MXD network (Tim/Keith?).
>
> Thanks all for the feedback,
>
> mike
>
> At 01:42 PM 1/19/2004 -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 Michael E. Mann
> Department of Environmental Sciences, Clark Hall
> University of Virginia
> Charlottesville, VA 22903
> ______________________________________________________________________
> _ e-mail: mannatXYZxyzginia.edu Phone: (434) 924-7770FAX: (434) 982-2137
> [2]http://www.evsc.virginia.edu/faculty/people/mann.shtml
Malcolm Hughes
Professor of Dendrochronology
Laboratory of Tree-Ring Research
University of Arizona
Tucson, AZ 85721
520-621-6470
fax 520-621-8229

______________________________________________________________
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
[3]http://www.evsc.virginia.edu/faculty/people/mann.shtml

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