The Decline - Exposed!

Steve McIntyre manages to undo “Mike’s Nature Trick” and reveals the decline that Phil Jones et al tried so hard to remain hidden (re-scraped from Watts Up with That via SDA):

For the very first time, the Climategate Letters “archived” the deleted portion of the Briffa MXD reconstruction of “Hide the Decline” fame – see here.

Gavin Schmidt claimed that the decline had been “hidden in plain sight” (see here. ). This isn’t true. The post-1960 data was deleted from the archived version of this reconstruction at NOAA here and not shown in the corresponding figure in Briffa et al 2001, though pre-calibration values were archived in a different NCDC file here. While the decline was shown in Briffa et al 1998 and Briffa 2000, it was not shown in the IPCC 2001 graph, one that Mann, Jones, Briffa, Folland and Karl were working in the two weeks prior to the “trick” email (or for that matter in the IPCC 2007 graph, an issue that I’ll return to.) For now, here is a graphic showing the deleted data in red. A retrieval script follows.

Figure 1. Two versions of Briffa MXD reconstruction, showing archived and climategate versions.

The relevant IPCC 2001 graph, shown below, clearly does not show the decline in the Briffa MXD reconstruction. Contrary to Gavin Schmidt’s claim that the decline is “hidden in plain sight”, the inconvenient data has simply been deleted. The reason, as explained on Sep 22, 1999 by Michael Mann to coauthors in 938018124.txt, was to avoid giving “fodder to the skeptics”. Reasonable people might well disagree with Gavin Schmidt as to whether this is a “a good way to deal with a problem” or simply a trick.

Figure 2. IPCC 2001 Fig 2.21 showing Briffa, Jones and Mann reconstructions together with HadCRU temperature.

It reminds me of the warning given to all of us by the great economist Ronald Coase: “If you torture the data long enough, it will confess.”

Cross-posted to Virginia Virtucon

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