It has long been suspected that upper-treeline ring widths are recording variability in temperature or a temperature-related variable such as growing season length (LaMarche, 1974; LaMarche and Stockton, 1974). This has been difficult to demonstrate with modern meteorological data, however, possibly due to a reduction of ring-width sensitivity to temperature.

[Emphases mine.]

Decoding the italicized phrase … this is more evidence that these guys understand that tree ring reponses are nonlinear and synergistic, and therefore unreconstructable through linear, univariate correlative/regressive models.

… An inference that might not obvious from a superficial reading.

NB: They should have provided a citation for the second statement. McIntyre’s work at CA being the most obvious choice.

“While ring width in bristlecone pine at the upper limit of its distribution may be strongly influenced by temperature or a temperature-related condition such as growing season length, in this semi-arid region drought may also influence growth, even at high elevation. The HI5 chronology was subjected to two separate Superposed Epoch Analyses (SEA) in an attempt to separate these two influences…

The SEA analysis period was AD 1595–1898; 20th century data were eliminated so as to avoid potential biases associated with industrial-era atmospheric contamination (LaMarche et al., 1984, Graybill and Idso, 1993 and Hughes and Funkhouser, 2003).”

also:

“Time-series plot of regional high elevation tree-ring index from 3000 BC to AD 2002 (HI5 chronology-variance-adjusted normalized mean of five subalpine bristlecone pine chronologies).

Bristlecones again. Once again, does this tie back to the original MBH study?

“Mann et al., 1998 M.E. Mann, R.S. Bradley and M.K. Hughes, Global-scale temperature patterns and climate forcing over the past six centuries, Nature 392 (1998), pp. 779–787.”

Guess so.

However here the author states:

a modified negative exponential curve, a straight line of negative slope, or a horizontal line were used in the standardization.

Such a procedure must give the resulting smoothed series a rising character. This seems to be the exact same kind of procedure used in MBH98 with PCA. There, as I remember, the authors used a different mean value for recent measurements resulting in a “hockey stick” shape for the smoothed graph. Here the author creates a slope in the results by deviding the original measurements by a slope.

I’ve done some analysis that supports and extends Southon’s work. I hope to publish it, but getting all the data is problematic.

In my view, the ice-core guys are heroes of science for gathering their data—spending years out on the Greenland ice cap. And their data is extremely valuable.

But I strongly dispute their ability to analyze data. Salzer & Hughes cite the work of ice core researchers Hammer et al.&nbsp[2003] on some volcanic ash; they also cite a paper of mine that criticizes Hammer et al. In fact, the main thing that my paper does is point out that Hammer et al. do not understand the concept of standard deviation. Worse, I had discussions about that with the authors prior to the publication of their paper, and I only published mine when they refused to reconsider.

I made the prediction long ago that the Sheep Mountain update will not show elevated growth through the warm 1990s and early 2000s. The present article does not settle the prediction – other than the matter is avoided by Hughes one more time.