cc: Keith Briffa date: Mon, 13 Aug 2007 13:52:07 -0700 (PDT) from: "David M. Ritson" subject: Re: to: Tim Osborn 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 > > > > > > > > >