There has been a lot of digital ink spilled on the use of the Lake Korttajarvi varve series in the long-term temperature reconstructions that are at the heart of Mann et al’s 2008 PNAS paper. Unfortunately, there haven’t been very many informed conversations in which the issues are discussed in a knowledgable and technically-focused manner by supporters and detractors of Mann’s uses of the proxies.
Three comments threads at William M. Connolley’s blog Stoat come closest, in my opinion.
Although a couple of obstacles became evident over the course of the three conversations there (Oh dear oh dear oh dear oh dear, Tiljander, and Tiljander, again).
One is that WMC often responds to critics by inserting remarks into the middle of their arguments, making those arguments harder to follow. Another is the two-edged sword represented by his liberal comment-truncation and deletion policy: the tactic can keep conversations on track, but it can also cause the facts and reasoning marshalled by critics to appear weaker and more disjointed than is actually the case.
This weekend, I reviewed the comments thread of Oh dear oh dear oh dear oh dear, revisiting some of the key points debated there. For context, the post itself is a mocking criticism of Roger Pielke, Jr., contending that Pielke “doesn’t’ understand” Mann et al’s use of the Lake Korttajarvi varve proxies. Most interesting is that WMC is an accomplished software engineer and climate modeler who has written extensively about sea ice and warming trends in the Antarctic, and who has authored posts at the flagship AGW Consensus blog RealClimate.org defending and defining that Consensus--prominent ongoing topics at Stoat.
An abridged and annotated version of that post's comments thread follows the "read more" break. For clarity, I have moved WMC’s interspersed comments to the end of each comment. I have also added some of my own thoughts; these are limited to the paragraphs that begin with the text "AMac 12/7/09".