UPDATE3: professor Rob Wilson leaves some scathing comments about the Mann paper. See below.
UPDATE2: There’s been some additional discussion on the dendro listserver, and it seems quite clear now that the scientists in the dendrochronology field don’t think much of Dr. Mann’s effort – and it appears there is a rift now between former co-authors. See the must read below. I’ll make this a sticky for about a day, and new posts will appear below this one. – Anthony
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People send me stuff.
In case you don’t know, ITRDBFOR is an electronic forum (a listserver) subscribed to by most of the world’s dendrochronologists. What is most interesting is that Hughes and Briffa are co-authors of the response to Mann.
—– Original Message —–
From: Rob Wilson
To: ITRDBFOR@LISTSERV.ARIZONA.EDU
Sent: Sunday, 25 November, 2012 20:43
Subject: [ITRDBFOR] Comment to Mann et al. (2012) at Nature Geoscience
Dear Forum,
In February of this year, Mike Mann and colleagues published a paper in Nature Geoscience entitled, “Underestimation of volcanic cooling in tree-ring based reconstructions of hemispheric temperatures”. Their main conclusion was that a tree-ring based Northern Hemisphere (NH) reconstruction of D’Arrigo et al. (2006) failed to corroborate volcanically forced cold years that were simulated in modelling results (e.g. 1258, 1816 etc). Their main hypothesis was that there was a temporary cessation of tree growth (i.e. missing rings for all trees) at some sites near the temperature limit for growth.
This implies Dendrochronology’s inability to detect missing rings results in an underestimation of reconstructed cold years when different regional chronologies are averaged to derive a large scale NH composite.
We scrutinized this study and wrote a response to Nature Geoscience. We are pleased to announce that our comment, along with a reply by Mann et al., was finally published on Nov. 25, 2012 (http://www.nature.com/ngeo/journal/vaop/ncurrent/index.html) – 8 months after submission.
Our comment focuses on several factors that challenge the Mann et al. (2012) hypothesis of missing tree rings. We highlight problems in Mann et al.’s implementation of the tree ring model used, a lack of consideration for uncertainty in the amplitude and spatial pattern of volcanic forcing and associated climate responses, and a lack of any empirical evidence for misdating of tree-ring chronologies.
We look forward to a continued discussion on this subject.
Kevin J. Anchukaitis, Petra Breitenmoser, Keith R. Briffa, Agata Buchwal, Ulf Büntgen, Edward R. Cook, Rosanne D. D’Arrigo, Jan Esper, Michael N. Evans, David Frank, Håkan Grudd, Björn Gunnarson, Malcolm K. Hughes, Alexander V. Kirdyanov, Christian Körner, Paul J. Krusic, Brian Luckman, Thomas M. Melvin, Matthew W. Salzer, Alexander V. Shashkin, Claudia Timmreck, Eugene A. Vaganov, and Rob J.S. Wilson
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Dr. Rob Wilson
Senior Lecturer in Physical Geography
School of Geography & Geosciences
University of St Andrews
St Andrews. FIFE
KY16 9AL
Scotland. U.K.
http://earthsci.st-andrews.ac.uk/profile_rjsw.aspx
“…..I have wondered about trees. They are sensitive to light, to moisture, to wind, to pressure. Sensitivity implies sensation. Might a man feel into the soul of a tree for these sensations? If a tree were capable of awareness, this faculty might prove useful. ”
“The Miracle Workers” by Jack Vance
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UPDATE: RomanM locates the Mann paper in comments, writing:
The original Mann article seems to be available at his web site:
http://www.meteo.psu.edu/holocene/public_html/shared/articles/MFRNatureGeosciAdvance12.pdf
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UPDATE2: More from the listserv
From: “Malcolm Hughes” <mhughes@LTRR.ARIZONA.EDU>
To: <ITRDBFOR@LISTSERV.ARIZONA.EDU>
Sent: Monday, 26 November, 2012 16:42
Subject: Re: [ITRDBFOR] Comment to Mann et al. (2012) at Nature Geoscience
> Ron – no dendrochronologists were involved in the offending Mann et al
> 2012 paper. What Rob described was the response of a number of us to
> some of the multiple flaws in the original paper. Cheers, Malcolm
>
> Malcolm K Hughes
> Regents’ Professor of Dendrochronology
> Laboratory of Tree-Ring Research
> University of Arizona
> Tucson, AZ 85721
—– Original Message —–
From: RONALD LANNER
To: ITRDBFOR@LISTSERV.ARIZONA.EDU
Sent: Monday, 26 November, 2012 03:48
Subject: Re: [ITRDBFOR] Comment to Mann et al. (2012) at Nature Geoscience
“a temporary cessation of tree growth” resulting in no rings for all trees? Now that is a hypothesis that I am willing to bet good money has no empirical support since studies of trees began 200 years or so ago. Speculation this bald could give dendrochronologists a bad name.
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UPDATE 3: Rob Wilson leaves this comment at Bishop Hill today, bolded section is my emphasis:
Nov 26, 2012 at 9:00 PM | 
Rob Wilson
Hi Again,
Our comment and Mann’s response to it can be accessed from this link:
http://www.st-andrews.ac.uk/~rjsw/all%20pdfs/Anchukaitisetal2012.pdf
his original paper is here:
http://www.meteo.psu.edu/holocene/public_html/shared/articles/MFRNatureGeosci12.pdf
Hmmm – what do I think of Mann’s response. Where does one start!
Well – he has provided NO evidence that there are stand (regional) wide missing rings for major volcanically forced cool years. Let’s focus on 1816 as an example – The “Year without a Summer” – where historical observations clearly show cool summer conditions (related to Tambora in 1815) throughout NE North America and Europe. Using either long instrumental records or historical indices, there is no evidence of a stand-wide missing ring in temperature sensitive tree-ring chronologies in Labrador, Scotland, Scandinavia or the Alps. Mann would probably turn around and say – well, actually, my model says that 50% of the sites would express missing rings – just not those in NE America and Europe. Sheesh!
To be less flippant, and putting aside criticisms of tree-ring series as proxies of past climate, the method of crossdating is robust and easily verifiable by different groups. I would be surprised if Mann has ever sampled a tree, looked at the resultant samples and even tried to crossdate them. He has utterly failed to understand the fundamental foundation of dendrochronology.
I undertook most of the analysis in D’Arrigo et al. (2006) and we clearly stated in the original paper that due to the paucity of sites (only 19) around the northern hemisphere, the reconstruction was most robust at time-scales greater than 20 years. Using the D’Arrigo reconstruction to look at inter-annual response to volcanically forced cool summers was a poor choice. Maximum density records, as shown in our response, would clearly be a far superior tree-ring parameter to use for such an exercise – as Briffa clearly showed in 1998. See also this paper:
http://www.st-andrews.ac.uk/~rjsw/all%20pdfs/D’Arrigoetal2009a.pdf
There is a lot more I could say, but this can all wait until next week at the AGU Fall Meeting.
One final observation is I urge you to look at Figure 1 in Mann’s original article. The instrumental record (black line) in Figure 1a (upper panel) clearly does not show strong cool temperatures in 1884 related to Krakatoa as seen in the two models. Following Mann’s hypothesis, the instrumental data must be wrong.
Time for some red wine
Rob