Cont.-

I’ve written multiple posts on the mathematics of borehole inversion calculations, which purport to estimate temperatures for thousands of years into the past from modern day temperatures measured downhole. These calculations require the inversion of a multicollinear matrix (with determinant close to 0). As far as I’m concerned, nearly all the details that specialists pontificate about are a sort of Chladni pattern artifact.

But that’s another story. Here the problem was much stranger. A few years earlier, I had (circuitously) managed to obtain a copy of the code used to calculate this borehole inversion (which is not archived anywhere.) The code showed that they had deleted the top 15 meters of the core from their calculation.

I’ve had a LOT of trouble getting the underlying borehole temperatures for some famous series. (The 2006 NAS panel cited one such result, but the original author (a US government employee) refused to make the data available, and, to my knowledge, it remains unavailable.) However, in this case, the underlying downhole temperatures had been archived, including the values had been deleted. Needless to say, they went down. An inversion using all the data would not have resulted in the impressive Hockey Stick in the PAGES2019 dataset, but a substantial recent decline.

There are one series with an enormous hockey stick: Mackenzie Delta (Porter 2013); and two series (“GB [Great Basin]” and nv512) with noticeable closing upticks. Sharp-eyed readers may have already figured out some of this story.

I discussed the Mackenzie Delta super-stick of Porter et al (2013), a new entry to hockey stick fabrication technology, in July 2019 here on Twitter. It comes from Yukon, Canada, an area that, in a 2004 study by d’Arrigo et al, had been a type location for the classic “divergence problem” – ring widths going down, while temperatures went up. So how did Porter et al manage to get a super-stick that had eluded Jacoby and d’Arrigo, long-time searchers for hockey sticks in tree ring data and not shy about picking cherries in order to make cherry pie?

They took “hide the decline” to extremes that had never been contemplated by prior practitioners of this dark art. Rather than hiding the decline in the final product, they did so for individual trees: as explained in the underlying article, they excluded the “divergent portions” of individual trees that had temerity to have decreasing growth in recent years. Even Briffa would never have contemplated such woke radical measures.



To be fair, Porter et al’s original article showed both the actual (non-descript) chronology from all trees, together with superstick resulting from “hide the decline” on individual trees: the decision to use the spurious superstick belongs to Neukom and PAGES2019.

Readers will also recall that the 2006 NAS Panel recommended that “stripbark” chronologies be “avoided” in temperature reconstructions. Although the climate community has professed to implement the recommendations of the NAS Panel, they are addicted to stripbark chronologies, the properties of which are well known. Five different PAGES2019 series use stripbark bristlecones (three from original Graybill versions): nv512 (Pearl Peak); nv513 (Mount Washington); ca529 (Timber Gap Upper); SFP (an update of San Francisco Peaks, incorporating az510) and GB (a composite of Pearl Peak, Mount Washington and Sheep Mountain, using both Graybill and updated information).

In 2018, I looked at how North American tree ring networks had changed since MBH98. The one constant was the addiction of paleoclimatologists to stripbark chronologies- a phenomenon that I had commented on long before Climategate (citing Clapton et al and Paeffgen et al), much to the annoyance of dendros, but the comment remains as true now as it was then. "

https://climateaudit.org/2021/08/11/the-ipcc-ar6-hockeystick/
Can everybody say cherry pick?