date: Tue, 28 Jan 2003 12:33:35 -0500
from: "Michael E. Mann" <mannatXYZxyztiproxy.evsc.virginia.edu>
subject: Re: multiproxy
to: Ulrich Cubasch <cubaschatXYZxyzat.fu-berlin.de>
That's fine--you can go ahead and use it. But I have to issue a number of caveats first.
This is a version we gave Tim Osborne when he was visiting here, and since Tim hasn't used
it, and we haven't compared results from that code w/ our published results, I can't vouch
for it--it may or may not be the exact same version we ultimately used, and it may or may
not run properly on platforms other than the one I was using (Sun running ultrix). Scott
Rutherford (whom I've cc'd on this email) has worked with the code more frequently.
The code is not very user friendly unfortunately. For example, the determination of the
optimal subset of PCs to retain is based on application of the criterion described in our
paper, which involves running the code many times w/ different choices. So the "iterative"
process has to be performed by brute force.
The method, as outlined, is quite straightforward and others have implemented it
themselves. SO you might prefer to code it yourself. That would be my suggestion. But you
are, of course, free to use our code.
That having been said, we have essentially abandoned that method now in favor of a
somewhat more sophisticated version of the approach, which makes use of the RegEM method
for imputing missing values of a field described by Schneider (J. Climate, 2000).
Some initial results are described here:
Mann, M.E., Rutherford, S., Climate Reconstruction Using 'Pseudoproxies', Geophysical
Research Letters, 29 (10), 1501, doi: 10.1029/2001GL014554
and in a paper in press in Journal of Climate.
Rutherford, S., Mann, M.E., Delworth, T.L., Stouffer, R., The Performance of
Covariance-Based Methods of Climate Field Reconstruction Under Stationary and Nonstationary
Forcing, J. Climate, in press, 2003.
(I don't have the preprint--Scott Rutherford can provide you with one however).
In our view, this is a preferable approach on a number of levels, though the results
obtained are generally quite similar.
I will be in Nice, and looking forward to seeing you there,
At 04:59 PM 1/28/03 +0100, Ulrich Cubasch wrote:
as you might know we (Briffa, Wanner, v. Storch, Tett ...) have an
European project called SOAP,
which aims at combining multy proxi and model data.
more under http://www.cru.uea.ac.uk/cru/projects/soap
In the workpackage I am coordinating we would like to use your
multi-proxy program for some
temperature reconstructions. The collegues in Norwich have got your
program already, but I would like
to implement it here in Berlin. I therefore would like to ask you if you
can grant me the permission to use it.
I will probably copy it then from Keith and Tim directly.
I will keep you informed about the results we obtain with it.
Are you coming to Nice?
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