The Australian Broadcasting Corp. had an interview with Malcolm Hughes on Apr 5 when he once more attempted to blame the messengers for identifying the shortcomings of their own statistical methodology. We eagerly await the Dendro Truth Squad rebutting this “misinformation”.
But first some comments by Hughes on bristlecones which are germane to our discussion of upper treeline proxies. He described bristlecone environment as “wickedly dry” – something that one would think would be a disadvantage in disentangling termperature:
And the problem there was, remember I told you they live in high, cold, dry places, they’re really wickedly dry places actually, less than 500 millimetres of precipitation a year, even in very high mountains.
He conceded that dendro-ists could do better with cold years than warm years, something that few readers here would disagree with:
if they’re at a lower elevation place and they’re limited by moisture then we can usually do a pretty good job of the driest years and not do a bad job of the moderate years, and a poorer job of the really wet years, because if you’ve got enough you’ve got enough and you’re not going to get any bigger, then we’d have to use other things in the size of the rings. Likewise with temperature, you can usually do a better job with tree rings of nailing down the cooler years than the warmer ones.
We still haven’t seen any formal discussion by Hughes of the U of A seminar topic Why are Upper Elevation Bristlecone Pine Really Growing Faster?, but maybe his interview gives some clues. Hughes claims that, in their consideration of bristlecones, they “set the last century aside”: because they are unable to allocate 20th century growth between warmer temperatures, CO2 fertilization and even nitrogen fertilization. Hughes:
One of the things that we set aside in our work about the bristlecone pine … and their effect on climate, was the last century. And the reason we set the last century aside is because these trees have been growing faster since the early 20th century than any time in the last 5000 years and we have this nailed down very firmly. It’s been known broadly for 20 years but we’ve taken a lot more samples, analysed a lot more wood and we’re seeing very, very clearly that something extraordinary is happening and at the moment we only have a partial idea of why it is happening. So to what extent this is warmer temperatures, to what extent this is direct fertilisation of the tree growth by increased atmospheric carbon dioxide I wouldn’t want to say just now.
In addition to CO2 fertilization, Hughes noted the possibility of nitrogen fertilization:
…. Well, there’s a couple of other possibilities, which is nitrogen; these plants are growing in tough conditions. Anyone who gardens knows you may need to add some nitrogen, we may have done that by populating California 100, 150 years ago. These trees are some hundreds of kilometres downwind of LA. If fog or smog can get to the Grand Canyon from the LA area it should be able to get to eastern California, too. So we haven’t completely ruled that out either.
The trouble is this: MBH didn’t “set aside” the last century in their discussion of bristlecones. The effect of Mann’s PC methodology, as has been endlessly observed, was to enhance the impact of bristlecones – a proxy which prior to Mann (and Hughes) had been avoided in multiproxy reconstructions and which the NAS Panel has said, once again, should be “avoided”.
But the Team is addicted to bristlecones and their interbreeding cousin, foxtails. Mann’s PC1 and bristlecones was used in more studies in 2006 than in any previous year (Osborn and Briffa 2006; Hegerl et al 2006; Ammann and Wahl, in press; and Juckes et al, status ??) In our discussions with Juckes on this blog, you can see how tenaciously the Team fights to hang on to bristlecones because their distinctive HS shape is important to yielding a HS reconstruction. So for Hughes to tell the Australian audience that they “set aside” bristlecone growth in the last century is, in Rob Wilson’s phrase, “misinformation” and I’m sure that the Dendro Truth Squad over at the Arizona listserv will pursue this vigorously.
The other problem is that Mann knew that there was no HS without the bristlecones (as evidenced by the CENSORED directory) and yet, as late as 2000, claimed that their reconstruction was “robust” to the presence/absence of all dendro series, while knowing that it was not robust even to the presence/absence of bristlecones, again a point that the Dendro Truth Squad has been strangely silent about.
Hughes speculates that the attention paid to the MBH hockey stick derives from its use by IPCC, as though that were a great insight. He doesn’t need to speculate on this. OF course, that’s the reason. It was also not used incidentally but featured prominently in the IPCC press conference releasing the WG1 report and just as prominently by governments. Kurt Cuffey of the NAS Panel said that IPCC “oversold” the hockey stick. Here’s Hughes feeling sorry for himself:
I think, and this is my interpretation, I don’t have anything other than supposition to support this, I think our particular diagram attracted the attention because it was used as figure 1b of the Summary for Policy Makers of the previous Intergovernmental Panel on Climate Change report 7 years ago. Had somebody else’s diagram, and there were a couple of other possibilities with the same findings, then they would have been the subject of, you know, angry email from Retired Engineer from Woola Woola or statements by senators who might not know a scientific question from the back end of a rhinoceros. So, I think whoever’s work had been used to illustrate that point would have been subject to that attention and it happened, on this occasion, to be ours.
Here’s an amusing exchange between Robyn Williams, the Australian interviewer, and Hughes:
Williams: … But since then the Academy of Science has come out and said that the hockey stick is valid on all sorts of criteria and yet the critics have persisted. Why do you think they get away with it?
Malcolm Hughes: Well, I don’t know that they do get away with it.
Williams closed by saying:
And the US Academy of Sciences endorsed the hockey stick in a report published on June 22 last year. I’m Robyn Williams.
There doesn’t seem to be a “consensus” at the University of Arizona about this. Scott Saleska of the University of Arizona, one of the climate scientists who filed the Amicus Curiae in the recent Mass vs EPA writes on another thread,
Though I haven’t so far worked in the climate proxy field, I basically see what you are trying to do here as scientific in a fundamental sense: evidence based inquiry, without accepting the say-so of anybody no matter their authority.
Whenever I look at this site … I am reminded of the saying that I think I first saw on the Splus news list: “In god we trust, all others must bring data.”) CA certainly is more scientific in terms of representing the actual ongoing (sometimes messy) process of ongoing evidence-based inquiry than any blog I am aware of. I read your GRL paper when published, thought it a reasonable criticism at the time, and noted that the NAS report did basically endorse it.
A third University of Arizona scientist, Matthew Salzer, has also recently opined on my work, complaining that I “broke the rules” – without specifying anything further. Maybe he meant that I broke the rules by trying do science “in a fundamental sense: evidence based inquiry, without accepting the say-so of anybody no matter their authority.” No wonder Rob Wilson thinks that it “could be dangerous to leave Steve McIntyre unchecked”.
[By the way, the NAS Panel did not endorse the MBH hockey stick any more than Stephen Jay Gould endorsed the Piltdown Man. Believing in evolution does not and did not oblige scientists to accept the Piltdown Man.]
Eduardo Zorita said at the time that the NAS Panel report was as severe a criticism of Mann as was possible in the circumstances. The NAS Panel certainly believed that it was “plausible” that the modern period could be shown to be warmer than the medieval period on alternate grounds than MBH, but accepted every one of our specific criticisms of MBH. Our papers did not comment one way or the other on whether some other set of data might resolve this issue, only that MBH didn’t. At the blog, I’ve observed that each of the other Hockey Team reconstructions likewise has fatal problems, but again I do not preclude the possibility that some future paper using better analysis (or more likely new and better proxies) may resolve the question.
I might add that several talented young scientists at AGU privately agreed that the various Hockey Team reconstructions were dead (they were not prepared to be identified publicly), but it’s gratifying to even get private acknowledgement from young scientists.