[This post was updated on December 12 to provide additional context that strengthens the original analysis – see below for details.]
This so-called Climategate is really getting out of hand, isn’t it?
Steve McIntyre has published allegations – twice now – that an internal IPCC authors’ debate about the inclusion of Briffa’s tree-ring reconstruction in a key figure from the 2001 WG1 Third Assesement Report was driven by concern about the post-1960 “decline” in tree-ring widths, a decline that showed a marked divergence with the instrumental tempertaure record.
The Climategate Letters show clearly that the relevant context is the IPCC Lead Authors’ meeting in Tanzania in September 1999 at which the decline in the Briffa reconstruction was perceived by IPCC as “diluting the message”, as a “problem”, as a “potential distraction/detraction”. [Emphasis added]
McIntyre even claims that lead author Michael Mann worried that showing the series with this decline would give “fodder” to “skeptics”.
But even a cursory examination of the emails in question shows that the discussion was really about other aspects of the reconstruction, specifically obvious discrepancies between Briffa’s reconstruction and the other two under consideration over the major part of the reconstruction’s length. Thus, once again, McIntyre’s speculations are shown to be utterly without foundation.
Even worse, McIntyre left out intervening sentences within the actual proffered quotes in what appears to be an unsophisticated attempt to mislead.