Tag Archives: weights

McShane and Wyner Weights on Mann 2008 Proxies

Most CA readers are aware that proxy reconstructions use linear methods and that, accordingly, all the huffing and puffing of complicated multivariate methodologies simply end up assigning a vector of weights. Surprisingly this obvious point was not understood by paleos when I started in this field. Because one can assign a vector of weights, it’s […]

Chladni and the Bristlecones

Some of the CA posts that I’ve found most interesting to write have been about identifying Chladni patterns in supposedly “significant” reconstructions when principal component methods have been applied to spatially autocorrelated red noise. (This is by no means a new observation, as warnings about the risks of building “castles in the air” using principal […]

Mann and his bristlecones

Gavin Schmidt and others have claimed that the M08 usage of the Tiljander sediments didn’t ‘matter’, because they could “get’ a series that looked somewhat similar without the sediments. They’ve usually talked around the impact of the Tiljander series on the no-dendro reconstruction. But there are two pieces of information on this. A figure added […]

TTLS in a Steig Context

Many CA readers know a lot about regression and quite a bit about principal components, but I dare say that a much fewer number are familiar with Truncated Total Least Squares (to which the regpar parameter belongs.) We’re seeing interesting interactions between PC=k and regpar=r – and there is little, if anything, in regular statistical […]

Mann 2008 – Replication II

Let’s continue Mann 2008 – Replication with EIV. To run regreclow.m and regrechigh.m you’ll need files climate, eofnumb, and proxyN, where N runs from 1 to 19. I’ve run prepinputforrecon.m with required folder structure (C:\holocene\s1\zuz10\work1\temann\ etc.) in my computer. After that I did run regrechigh.m in folder C:\holocene\s1\zuz10\work1\temann\zzrecon1209\nhnhscrihad\highf and regreclow.m in folder C:\holocene\s1\zuz10\work1\temann\zzrecon1209\nhnhscrihad\lowf The regem […]

Interaction of Infilling on Std Deviation

Standardization in Mannian algorithms is always a bit of an adventure. The bias towards bristlecones and HS-shaped series from the impact of Mann’s short segment standardization on his tree ring PCs has been widely publicized. Smerdon’s demonstration of defects in Rutherford et al 2005, Mann et al 2005 and Mann et al 2007 all relate […]

Reconciling to Wahl and Ammann

When Wahl and Ammann’s script first came out, I was able to immediately reconcile our results to theirs – see here. As Wegman later said: when using the same proxies as and the same methodology as MM, Wahl and Ammann essentially reproduce the MM curves. Thus, far from disproving the MM work, they reinforce the […]

An Example of MBH "Robustness"

In the MBH source code, they apply steps that purport to weight the temperature PCs in their regression calculations proportional to their eigenvalues. Comments on their code say: c set specified weights on data … c weights on PCs are proportional to their singular values This is one of two weighting procedures in MBH for […]

Squared Weights in MBH98

A couple of weeks ago, I said that I would document (at least for Jean S and UC) an observation about the use of squared weights in MBH98. I realize that most readers won’t be fascinated with this particular exposition, but indulge us a little since this sort of entry is actually a very useful […]

PC Weights on a Square Region

A few days ago, I showed some plots showing distribution of weights arising from principal components carried out on data from a region arranged as a line segment (think Chile). Today I’ve done a similar analysis for a square shaped region again assuming spatial autocorrelation governed by distance. In this case, I made a regular […]

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