As CA readers are well aware, the Briffa et al 2001 reconstruction, based on 387 tree ring density chronologies, goes down in the latter part of the 20th century – clearly contradicting the Mann reconstruction. The inconsistency between the two reconstructions ought to have troubled anyone with an actual scientific interest in the validity of these reconstructions. However, in order not to “dilute the message” in IPCC TAR, climate scientists chose to “hide the decline”, by simply deleting adverse data that went down. “Hiding the Decline” is the title of Andrew Montford’s forthcoming book.
Lewandowsky appears to be yet another person who has been “tricked” (TM – climate science) by IPCC and others hiding the decline in the Briffa reconstruction. In his post on replication, Lewandowsky claimed that the Briffa et al 2001 decline not only did not contradict the Mann hockey stick, but replicated it:
Replicable effects such as the conjunction fallacy are obviously not confined to cognitive science. In climate science, for example, the iconic “hockey stick” which shows that the current increase in global temperatures is unprecedented during the past several centuries if not millennia, has been replicated numerous times since Mann et al. published their seminal paper in 1998. (Briffa et al., 2001; Briffa et al., 2004; Cook et al. 2004; D’Arrigo et al., 2006; Esper et al., 2002; Hegerl et al., 2006; Huang et al., 2000; Juckes et al., 2007; Kaufman et al., 2009 ; Ljungqvist, 2010; Moberg et al., 2005; Oerlemans, 2005 ; Pollack & Smerdon, 2004; Rutherford et al., 2005; Smith et al., 2006).
One of the fundamental properties of proxy series is whether they go up or down in the 20th century – a seemingly elementary phenomenon that we reflected on in connection with Mann and upside-down Tiljander here, where a reader linked to an amusing video in which the protagonists didn’t care whether data went up or down, a video that seems apt for Lewandowsky as well:
Aside from satire, surely the reconstruction between the Briffa reconstruction and the Mann reconstruction ought to be more worrying to anyone actually interested in proxy reconstructions. Both the Mann reconstruction and the Briffa reconstruction used very large networks of tree ring data: explaining why one series went up while the other went down ought to have been a priority for specialists. (The “consensus” explanation by the Hockey Team is simply incorrect and all-too-typical armwaving. They claim that the Briffa reconstruction, unlike the others, is from a small geographically unrepresentative subset. In fact, the Briffa reconstruction is from a very large network of 387 sites, while the other reconstructions cited above are from small (5-18 site) networks, in which bristlecones and/or Yamal are important components. The Mann reconstruction, like Briffa, is from a large network, but its methodology results in very high weighting to the bristlecones.)
The idea that present temperatures are “unprecedented during the past several centuries” was definitely not original to the Mann hockey stick, as this view dated back to at least Hubert Lamb and could be said to be a consensus view.
Nor does the “replication” claimed by Lewandowsky necessarily impress all specialists. Esper et al 2012 (with coauthors Zorita, Wilson and Timonen) recently criticized Lewandowsky’s prefered reconstructions in terms reminiscent of Climate Audit, as follows:
The missing millennial scale trends in existing TRW records as well as the increased cooling trend after removal of this proxy type from the Arctic-wide estimates both suggest that the widely cited hemispheric reconstructions underestimate pre-instrumental temperatures to some extent. This hypothesis seems to be important as most of the annually resolved, large-scale records are solely composed of or dominated (on longer timescales) by TRW data, and their spatial domain encompasses the Northern Hemisphere extratropics including northern boreal and Arctic environments. Inclusion of tree-ring data that lack millennial scale cooling trends, as revealed here (Fig. 3 and Supplementary Fig. S1), thus probably causes an underestimation of historic temperatures.
D’Arrigo et al 2006, one of the supposed confirmations of the Stick, spoke against the ability to draw conclusions of the medieval relative to modern period as follows:
we stress that presently available paleoclimatic reconstructions are inadequate for making specific inferences, at hemispheric scales, about MWP warmth relative to the present anthropogenic period and that such comparisons can only still be made at the local/regional scale
Lewandowsky, who has written in the past on “social priming”, noted in his post that Kahneman had recently slagged social priming theories (a development covered at CA here.) Lewandowky’s post cited the following classic example of social priming:
For example, it has been reported that people walk out of the lab more slowly after being primed with words that relate to the concept “old age” (Bargh et al., 1996)
As partial support for the concept of “social priming”, it seems to me that there is a statistically significant increase in the incidence of drivel in writings by activists after being primed with words that relate to “climate skeptics”. This hypothesis will be more difficult to test among authors where the incidence of drivel is already high, even without social priming.