they weight the proxies according to their correlation with NH temperature

This doesn’t make any sense physically since trees respond to local climate and not global climate. Perhaps they should have weighted them by the r^2 of local temperature. I wonder if this would cause the LIA and MWP to reappear?

Before they get to their Total Least Squares step, they weight the proxies according to their correlation with NH temperature – I’ve written about Partial Least Squares regression previously and , of course, this is Partial Least Squares. I’ve shown that the Mannian regression methodology reduces to PArtial Least Squares in the early steps – of course they didn’t realize it. So here we have two climate reconstrucions both using Partial Least Squares, both supposedly as novel inventions.

Mann made a PArtial Least Squares estimator and re-scaled it to match the variance of the temperature PC1. Hegerl et al re-scale their PLS estimator a little differently – by a Total Least Squares regression on NH temperature.

The Hegerl proxies are, as I predicted, virtually identical to the Osborn and Briffa “independent” reconstruction: PC1, foxtails, Yamal, Tornetrask, Yang composite, etc. It’s pretty funny.

#83. bender, speaking of bin-and-pin, have you read Mann’s discussion of endpoint smoothing – it was a Comment by Willie Soon and Reply by Mann in GRL a couple of years ago. Should be up on Mann’s website. I didn’t try to sort it out and, since it’s Mann-speak, it always takes time.

The reply by Mann in GRL compared three methods. Here’s his description of the methods:

To approximate the “minimum norm’ constraint, one pads the series with the long-term mean beyond the boundaries (up to at least one filter width) prior to smoothing.

To approximate the “minimum slope’ constraint, one pads the series with the values within one filter width of the boundary reflected about the time boundary. This leads the smooth towards zero slope as it approaches the boundary.

Finally, to approximate the “minimum roughness’ constraint, one pads the series with the values within one filter width of the boundary reflected about the time boundary, and reflected vertically (i.e., about the “”y” axis) relative to the final value. This tends to impose a point of inflection at the boundary, and leads the smooth towards the boundary with constant slope.” (Mann, 2004)

He recommends using the “minimum roughness” constraint … apparently without noticing that it pins the endpoints.

I wrote a reply to GRL pointing this out, and advocating another method than one of those three, but they declined to publish it. I’m resubmitting it.

w.

All the blue triangles in North America look like Mann’s North American tree ring network – all the sites available after 1750. But the MBH99 PC1 only uses 28 sites, and is, of course, almost entirely weighted towards bristlecones, especially Sheep Mountain – (I guess Hughes didn’t send Hegerl the updated Sheep Mountain data.) I would bet dollars to doughnuts that most of the sites shown do not contribute to the PC1.

w. Siberia: in order to avoid any heavy biases of the mean composite by a number of sites from one region, the west Siberia time series is a composite of three/four time series from this region: two “polar Urals” records east of the Urals — Yamal (Briffa et al. 1995) and Mangazeja (Hantemirov and Shiyatov 2002 – both by way of Esper et al.) and two records from west of the Urals (Hantemirov and Shiyatov 2002). The records from each side of the Urals were first averaged and then combined for the w.Siberia.short composite; the w.Siberia.long composite involved Yamal and the west.Urals composite. The sites from Esper have been RCS processed.

I guess that they feel that identifying the sites is somewhat of a concession and they don’t need to be encumbered by any considerations of making the identifications easy. For example, Mangazeja is not mentioned in Hantemitov and Shiyatov 2002, but is used in Esper et al 2002. I presume that this is the version carried forward.

We’ve had lots of discussion of Yamal on this site, but they don’t seem troubled by it. Here they’ve attributed the “Yamal” site to Briffa et al 1995, which discusses the different Polar Urals site; the Yamal substitution took place in Briffa 2000. However, Esper et al 2002 is the ONLY study that used the Polar Urals update – so it’s still a guess what series they used. The start date shown is in the 10th century – so it’s possible that they might have used the Briffa et al 1995 series that started then without the update.

They mention two sites east of the Urals attributed to Hantemirov and Shiyatov 2002, which doesn’t mention any such sites. I wonder what they are.

I’ve posted up Hantemirov and Shiyatov here (which is an interesting read in its own right.)