Reposted from WUWT, this article by Talkshop contributor Lucy Skywalker is excellent background to the latest episodes in the hockey stick wars between Realclimate.org and ClimateAudit.org, where Steve McIntyre has just delivered two more blows to the ‘Team’ treering chronology-temperature reconstructions. These have been used to support the ‘Hockey Stick’ graph drawn by Michael Mann using statistical techniques whixh have since been heavily criticised by expert statisticians. Mann was also selective in which tree ring chronologies he used, favouring ones which supported his conclusion, and excluding ones which didn’t. This kind of selection bias is frowned on in all scientific disciplines; except paleo-dendro-climatology apparently, where they have been known to cheerfully admit to it.
However as we mentioned earlier on the subject of biological growth populations, this does not mean that one could not improve a chronology by reducing the number of series used if the purpose of removing samples is to enhance a desired signal. The ability to pick and choose which samples to use is an advantage unique to dendroclimatology.
– Esper et al 2003–
Or more succinctly
you had to pick cherries if you want to make cherry pie
Rosanne D’Arrigo
They really need to read Lucia’s post on cherry picking.
Guest post by Lucy Skywalker
Let’s look closely and compare local thermometer records (GISS) with the Twelve Trees, upon whose treerings depend all the IPCC claims of “unprecedented recent temperature rise”.
For my earlier Yamal work, see here and here. For the original Hockey Stick story, see here and here.
Half the Hockey Stick graphs depend on bristlecone pine temperature proxies, whose worthlessness has already been exposed. They were kept because the other HS graphs, which depend on Briffa’s Yamal larch treering series, could not be disproved. We now find that Briffa calibrated centuries of temperature records on the strength of 12 trees and one rogue outlier in particular. Such a small sample is scandalous; the non-release of this information for 9 years is scandalous; the use of this undisclosed data as crucial evidence for several more official HS graphs is scandalous. And not properly comparing treering evidence with local thermometers is the mother of all scandals.
I checked out the NASA GISS page for all thermometer records in the vicinity of Yamal and the Polar Urals, in “raw”, “combined”, and “homogenized” varieties. Here are their locations (white). The Siberian larch treering samples in question come from Yamal and Taimyr. Salehard and Dudinka have populations of around 20,000; Pecora around 50,000; Surgut around 100,000; all the rest are officially “rural” sites. Some are long records, some are short.

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