Comments on: Latitudinal Treeline

By: Wilson, Pisaric and Gaspé « Climate Audit

Wilson, Pisaric and Gaspé « Climate Audit — Tue, 07 Jun 2011 01:16:17 +0000

[...] to the ITRDB data bank. [Update: see post here with further thoughts on the location of this site. Next post in category] Rob Wilson wrote, using an uncharacteristic Gavin-esque sigh, as follows: Sigh [...]

By: jae

jae — Fri, 30 Mar 2007 22:12:46 +0000

Now the 64K question. If you don’t average them, what do you do to establish the signal, and how does one know what kind of signal you are getting?

By: bernie

bernie — Fri, 30 Mar 2007 22:10:56 +0000

Martin:
This is interesting that within, I assume, close proximity you have positive and negative responders from with in the same species. How do you decide which is which? Are there generalizable factors that can be expressed as a variable in an equation – even as a dummy variable?

By: Steve McIntyre

Steve McIntyre — Fri, 30 Mar 2007 20:25:32 +0000

#23. Hi, Martin. you’ve provided evidence that trees are positive and negative responders. It’s one thing to be able to classify 20th century trees, but how do you go about classifying 11th century trees – since presumably the same thing would occur if there were prior warming periods?

By: Steve Sadlov

Steve Sadlov — Fri, 30 Mar 2007 20:17:45 +0000

RE: #23 – The climate in that part of Alaska is technically semi arid. A potentially confounding factor?

By: Dave Dardinger

Dave Dardinger — Fri, 30 Mar 2007 20:08:07 +0000

re: #23

Welcome, Dr. Wilmking!

Are they actually negative responders; i.e. growth slows down with higher temperature, or are they non responders; i.e. ring width not correlating with temperature? And if the former, are there also non-responders? Finally in any case, what physical factors would account for negative vs positive responders and has any research explored individual trees to see which applied in a particular case?

By: martin wilmking

martin wilmking — Fri, 30 Mar 2007 19:47:32 +0000

Hi all,

just to clarify some things. my data/trees from the brooks range ARE from latitudinal treeline, which coincides there with altitudinal treeline.

using the data from the ITRDB as was done in the graph above is a little problematic. there you averaged i assume the chronologies. when i archived my data in the ITRDB, i only submitted raw ring width of individual trees. since all of my sites contain sub-populations of positive and negative responders as you have also mentioned elsewhere, it is not advisable to average them. you basically average out the signal.

greetings
martin

By: beng

beng — Sun, 25 Mar 2007 13:21:21 +0000

For a very rough comparison w/the Andrea Lloyd series, the surface temp record for Barrow, AK is here: Barrow, AK temp The 1976 PDO shift (somewhat) & 1998 El Nino spike are apparent.

By: Tim Ball

Tim Ball — Sun, 25 Mar 2007 05:52:41 +0000

The treeline on each side of Hudson Bay is distinctly different because of the influence of the Bay on the circumpolar vortex. On the west side it is a quite distinctive line that follows the 10°C summer isotherm. On the east side it is a very indistinct line with very large outliers of trees and very large inliers of tundra. The Cri Lake site was always considered problematic because of these conditions. Brinkman and Barry attempted to clarify the climatic differences between the west and east sides of the Bay as early as 1972 following the work of Bryson in trying to establish the main position of the Polar Front. Blasing and Fritts (1976 p. 58) note “…the overall reconstructions imply a more meridional circulation in the 19th century than in the first half of the the 20th century.”

By: beng

beng — Sat, 24 Mar 2007 14:44:27 +0000

Eyeballing isn’t a statistical analysis, but those graphs do show a dip in the late 60′s & then a rise ~1976 (the PDO shift), but it’s unremarkable compared to other cycles. And looks like a 1998 El Nino pulse.

Certainly, one can qualitatively say these sites are “more” temp sensitive than arid bristlecone sites in the Amer west (which had already been identified in the literature as not correlating w/temps).