The Yamal reconstruction was introduced in Briffa 2000, a survey paper that did not include elementary information like core counts. As a result, users of the Briffa 2000 Yamal reconstruction (including Mann and Jones 2003, Moberg 2005, Hegerl 2007; D’Arrigo 2006, IPCC 2007, etc…) used it without any knowledge that the core counts did not meet RCS standards. In his recent online article, Briffa said that the closing portion of the Yamal results should be used “cautiously”. A Delayed Oscillator reader observed at Delayed Oscillatorthat this caveat should have been made clear in Briffa’s previous papers:
Briffa should have made clear in his papers that the post 1990 reconstruction was based on very few trees, and so should be “treated with caution”, as he explained in his recent web post.
Instead of agreeing with this obvious point, Delayed Oscillator argued that Briffa et al 2008 “shows sample size for each chronology”. Briffa et al 2008 would constitute notice only to users of this data after 2008 (such as Kaufman et al 2009), but does not constitute notice for users up to and including IPCC AR4. I wish that climate scientists would simply concede this sort of unwinnable point and focus on points that are interesting ones. If they don’t understand that notice in 2008 cannot be effective notice in 2000, it’s hard to have a sensible discussion.
But even the disclosure of Yamal sample size in Briffa et al 2008 is far from satisfactory. Here is their Table 1 reporting the number of samples during periods specified in the Table. In the -200 to 2000 period, Yamal is listed as having 611 samples, nearly double the number of samples for Avam-Taimyr (330), even though Avam-Taimyr had over 100 samples in 1990, while Yamal had only 10.
In the Phil Trans B measurement archive provided in Sept 2009, there are indeed 330 cores in the Avam-Taimyr sample, but for Yamal there are only 41% of the reported “611” samples. Phil Trans B Figure 3 shows core counts by year and looks like it uses the correct core count for Yamal (252 not 611.) The scale for core counts is inconsistent between panels, so that the relatively low closing counts for Yamal are not as clear as they might be.
If it weren’t for the incorrectly reported number of 611 samples for Yamal, Delayed Oscillator might be able to argue that Figure 3 constituted notice to post-2008 users and that Kaufman et al 2009 had satisfactory notice. However, under the circumstances, it is surely more than a little embarrassing that Briffa et al 2008 incorrectly reported the Yamal sample size as 611 rather than 252. I wonder where the figure of 611 came from??