OK, we're just going in circles here.

The windmills of your mind, or an artefact of flaky science?

Carl Sagan popularised the saying 'extraordinary claims requires extraordinary evidence' and yet Mann's original work, which by apparently overturning a swathe of previously accepted research certainly ranks as extraordinary, did not provide full disclosure (and to this day still hasn't). Others I’ve mentioned have also made extraordinary claims in their respective fields, notably Lewandowsky and Resplandy, but these were quickly debunked as psycho-babble twaddle and mathematically flawed respectively. What they all have in common, however, is that they all passed peer-review; a process supposedly designed to weed out the dubious.

One previously claimed that 'deniers' cannot converse logically about climate change. Perhaps one doesn't see the irony here; that having provided compelling evidence of the uncertainty of Mann's work (of its being nothing like the extraordinary originally believed) one is still prepared to accept it. Is that logical?

As repeatedly shown by Steve McIntyre, Mann's original work was heavily reliant on: "[Donald] Graybill’s stripbark bristlecone chronologies and that the contribution from all other proxies was nothing more than whitish noise. We noted that Graybill himself had attributed the marked increase in late 19th and 20th century bristlecone growth to CO2 fertilization, not temperature – a theory which was arguably a harbinger of the massive and widespread world greening, especially in dry areas, over the 30 years since Graybill et al. (1985)¹."

Even the 2006 NAS panel agreed that stripbark (Graybill) chronologies should be avoided in temperature reconstructions, though this recommendation was pointedly flouted by Mann et al. 2008, with his inclusion of 20 of them. Then came the Tiljander lakebed sediments fiasco, where he claimed he could obtain a non-dendro reconstruction.

"Because of persistent criticism over the impact of these flawed proxies, Mann et al. (2008) made the grandiose assertion that he could get a hockey stick without tree rings (and thus, a fortiori, without stripbark bristlecones) – a claim credulously promoted by Gavin Schmidt at Real Climate. However, it was almost immediately pointed out at Climate Audit that Mann’s non-bristlecone hockey stick critically depended on a Finnish lake sediment “proxy”, the modern portion of which (its blade) had been contaminated by modern agriculture and road construction and which had been used upside-down to its interpretation as a temperature proxy in pre-modern times. Mann was aware of the contamination of lake sediments, but argued that his use of contaminated (and upside down) data was legitimate because he could get a HS without them – in a calculation which used stripbark bristlecones. When challenged to show results without either stripbark bristlecones or upside-down mud, Mann (and Gavin Schmidt) stuck their fingers in their ears, with the larger climate community obtusely refusing to understand a criticism that was obvious to any analyst not subservient to the cause."

Today, thanks to efforts of Steve McIntyre and others, hockey stick construction has largely been debunked as being merely an artefact of proxy selection, and one of those blind alleys I previously alluded to. McIntyre himself once described stripbark chronologies as heroin for paleoclimatologists and Keith Briffa's Yamal chronology as cocaine; thus it is hardly surprising there are some still willing to waste time, effort and resources in their pursuit. In the meanwhile, real science has moved on.

[1] [Link: climateaudit.org]