Key excerpt: ‘The real fireworks came when Mann’s latest papers, which hypothesise that tree ring proxies have large numbers of missing rings after major volcanic eruptions, were described as “a crock of xxxx”.
Mann deletes tweet! Mann: ‘Closet #climatechange #denier Rob Wilson, comes out of the closet big time: http://www.bishop-hill.net/blog/2013/10/21/wilson-on-millennial-temperature-reconstructions.html … #BadScience #DisingenuousBehavior’
Shortly afterwards, Mann got into a long and somewhat huffy discussion with Tamsin
Last week I attended a lecture given by Rob Wilson at the University of St Andrews. This was a two-hour marathon, a format that is excellent if your lecturer is good enough to carry an audience, as it enables issues to be addressed in much more depth than is the norm. In the event, the time shot by, and if you read on you will see why.
Rob was doing a review of the millennial temperature reconstructions, following the story from the First Assessment Report through to AR5. As readers here know, Rob is no kind of a sceptic (a point he repeated over lunch), but on the northern hemisphere paleo studies his position is not a million miles away from mine. In places our positions are identical, as you will see.
Because of the prominence of Michael Mann’s work in the area, some of the lecture was devoted to the Hockey Stick, to the 2008 paper (the “upside down Tiljander” study to the initiated) and to Mann’s most recent area of focus, the influence of volcanoes on tree ring growth. Students learned that the Hockey Stick included a whole lot of inappropriate proxies and heard something of the issues with its verification statistics. The wallpapering of the Third Assessment with Mann’s magnum opus and John Houghton’s claims about unprecedented warmth based on this single study were described as “ridiculous”. “Ultimately a flawed study” was the conclusion, with a gory list of problems set out: inappropriate data, infilling of gaps, use of poorly replicated chronologies, flawed PC analysis, data and code withheld until prised from the grasp of the principals. In the paper’s defence, it was noted that it was an early attempt at a millennial reconstruction and that it did at least attempt to discern spatial variability, something that had not previously been done.
We also heard about Mann’s minumus parvum opus, The Hockey Stick and the Climate Wars, which Rob, like so many others, had given up on in fairly short order, and then saw an excerpt from Iain Stewart’s Climate Wars TV programme. Having seen Mann’s paper criticised so forcefully, I assume that Stewart’s unquestioning faith in the graph will have left the audience with a pretty low opinion of his abilities.
That was the gentle beginning. When we got onto Mann et al 2008, we learned about the silliness of the screening process, and students were invited to try screening a set of random generated timeseries in the way Mann had gone about this study. Tiljander didn’t get a mention, but I guess there are only so many flaws one can take on board, even in a two-hour lecture.
The real fireworks came when Mann’s latest papers, which hypothesise that tree ring proxies have large numbers of missing rings after major volcanic eruptions, were described as “a crock of xxxx”.
Away from the Mann stuff, this was, as I have suggested a very fair representation of the science of millennial temperature reconstructions, with the overwhelming impression being of a field that is still trying to work out if is possible to constrain the answers to the point where they are useful. The students were undoubtedly hearing the truth, warts and all, about the field they were studying. If only policymakers could hear the truth too.
Update: Meteorologist Joe Bastardi challenges Michael Mann: ‘He tears apart your work piece by piece, as do many. Why dont you simply come out and debate him one on one.?’ — ‘Judith Curry is billed by Dr. Mann as “serial climate disinformer Judy Curry”; Alinsky bullying tactics’
Flashback: 2002 Briffa email mentions Mann’s “diminishing support” and the “questionable nature of much of Mann’s verbiage”; says “Mike could be a lot more open about the real uncertainty of his early temperature estimates”
Flashback: In case you missed it: Hockey stick co-author: “it may be that Mann et al simply don’t have the long-term trend right”; “I hedge my bets on whether there were any periods in Medieval times that might have been “warm”, to the irritation of my co-authors!”
Flashback: Phil Jones to Mann: “both of us think that you’re on very dodgy ground…What the real world has done over the last 6000 years and what it ought to have done given our uunderstandingof Milankovic forcing are two very different things”
Flashback: Briffa gives Mann a positive? reference, but includes phrases like “not sufficiently aware of the characteristics of some of the data with which he worked”; “overconfidence in his work which bordered on seeming arrogance”
Flashback: Michael Mann vs Michael Mann: Did I say that the hockey stick might qualify to be the “truth” as portrayed in the IPCC Policy Makers Summary? I meant it was an “obscure graph” that unnamed other people have made “appear more definitive than it was ever intended”
Flashback: Email 1705, April 2002, what “settled” science looks like: After Michael Mann writes “There are some substantial scientific differences here, lets let them play out the way they are supposed to, objectively, and in the peer reviewed literature”, Raymond Bradley writes to Briffa “excuse me while I VOMIT!!”
‘More than 700 scientists from 400 institutions in 40 countries have contributed peer-reviewed papers providing evidence that the Medieval Warm Period was real, global, & warmer than the present’ – Climate Depot’s Medieval Warm Period Round Up of Studies
Michael Mann says lawsuit against National Review is on! Climate Depot responds to Mann and his lawyer’s claims about the Hockey Stick & Climategate — Climate Depot’s Exclusive Report Challenging Michael Mann’s climate claims