cc: Keith Briffa <k.briffa@uea.ac.uk>
date: Mon, 13 Aug 2007 13:52:07 -0700 (PDT)
from: "David M. Ritson" <dmr@slac.stanford.edu>
subject: Re:
to: Tim Osborn <t.osborn@uea.ac.uk>

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Dear Tim,

Just a reminder. RCS also is plagued with systematic distortions. I really
would like to see your  basis for it in greater detail than provided in the 
Cook .. Briffa 1995 article, where it appears more a wish than a fact.

Cheers

Dave



On Sun, 29 Jul 2007, David M. Ritson wrote:

>
> Dear Tim,
>
> Thanks for your clarifications. However my underlying concern was to find a
> detailed account and defense of the RCS method ("global RCS" processing).
> I may well have missed something but was not helped by your  references.
> in this connection. I  have already , as carefully as possible, read
> the extant RCS literature starting from Fritts 1976 and Briffa's 1992 and
> proceeding to the present.
>
> The claim  that RCS methodology avoids the problems
> of `the segment curse' appears to rest on an
> (otherwise unsupported(?) claim in Cook  et al 1995 that " ,,, the
> cross-dated annual changes in ring-width between trees due to
> climate are forced out of alignment and effectively averaged out in the
> creation of the mean regional curve."? If Cook et al's above statement was a 
> valid approximation,  RCS would indeed
> avoid the `segment curse'. I have taken a preliminary look at this using
> simulated data focussed on cases with sufficient data to
> make systematics the primary final error-source.
> In the presence of systematic trends in paleo forcing history and 
> sample-depth the Cook cancellations are less than perfect. This is of course
> preliminary.  I have no desire to reinvent the wheel, and particularly not to 
> replace it with a square wheel, and may not be doing what you guys do, or
> you may have already looked at this in depth.
> In my past life as a particle physicist, prior to analysis we would write-out 
> a detailed mathematical prescription for processing a set of data. Such an 
> algorithm was sufficient so that it could  (if wished) be handed over to a 
> soft-ware programmer and he/she could then, even without knowledge of the 
> field, provide clean working code. I presume
> that you follow this procedure. Your RCS mathematical algorithm is what I am 
> looking for, not its code implementation.
>
> I would be grateful if you could let me have this and of
> course any revelant work of you or others in this area. Hopefully this is not 
> a burdensome request,
>
> Cheers
>
> Dave
>
>
>
>
>
>
>
>
>
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