I am a skeptic.
Not a climate skeptic, not in the sense of the improperly commandeered word we use in the climate debates. In my experience they know little of real skepticism as a general rule. But me, I really do dislike taking assertions on their face if I don't have all the facts and I really do try to form my own opinions, especially about people.
So I have tried very hard to reserve judgement on Judith Curry and her emerging role in the climate blogosphere despite reading some pretty damning reviews of her blog performances from voices in my own "camp". My first awareness of her is from the hurricane wars a few years ago, around the time of Katrina. She struck me as a voice of calm and perspective in what was a quite passionate debate about very unsettled science. I watched her venture on to Climate Audit and try to reason with people who can be very... um, unreasonable.
So it is really with regret and even sadness that, faced with clear and incontrovertible evidence, my opinion of her has plumetted to rock bottom.
It really started a couple of month's ago on Keith Kloor's blog when among other eybrow raising things Judith defended the Wegman report against DeepClimate's accusations of plagarism. Okay, I only have second hand information about Wegman and the underlying technical arguments of the underlying scientific issues are well beyond my personal grasp of statistics so who am I to dismiss the opinion of a working scientist? But she did not talk statistics, she said:
Deepclimate accuses Wegman of plaigarism. A very serious charge, that would constitute scientific misconduct. So what is the actual accusation? They accuse him of plaigarizing the definition of "social network" from the Wikipedia, and then complain that the word changes that Wegman made pervert the original meaning of the wikipedia definition.
Huh?
Further down in the same comment she feels so strongly she writes this:
Let me say that this is one of the most reprehensible attacks on a reputable scientist that I have seen, and the so-called tsunami of accusations made in regards to climategate are nothing in compared to the attack on Wegman.
A lot of people jumped on this comment because on the matters of fact it is completely wrong (let's just leave aside how divorced from reality the comment "nothing compared to climategate" is!) Deepclimate's accusations are much more serious than her presentation of them and they are very well supported. Faced with a pile-on of objections chock full of specifics and supporting citations what does she do? She brushes it all off with a casual admission that she actually has no idea what she is talking about and suggests that no one mention it again.
To borrow her own rhetorical device: "huh"?!
Look again at what she said about the author of DeepClimate and ask yourself if you would ever use such strong language to describe something you "have not investigated in any detail (and don't intend to)"?
I wasn't impressed by that, but because I have not investigated Deepclimate's work myself in any detail (and don't intend to) I still wanted to reserve judgement on Dr Curry, unlike Dr. Curry herself. On top of that, she was facing a multitude of antagonists, and people in such situations tend to behave very, well, very tribally.
As I said, that was some three months ago. Fast forward to July 22 and an RC article written by tamino. This is a review of yet another attack on the infamous MBH Hockey stick, this time in book form. I thought tamino's rebuttal was pretty convincing, but the technicalities are, as I have always admitted, beyond my statistical understanding. I was curious when Judy Curry popped in with this rather brusque critique:
JC's grade for the review: C-
pros: well written, persuasive
cons: numerous factual errors and misrepresentations, failure to address many of the main points of the book
If anyone is seriously interested in a discussion on this book, I can see that RC isn't the place, people elsewhere are already describing their posts not making it through moderation.
Hmmm. Surely this is not just that as-common-as-it-is-infuriating hand wave of a reference to "numerous" problems that will never be identified. You know, like what we get from the most common of trolls. Surely she will come back with at least one example? Page after page of comments goes by but no elaboration materializes. Too bad, she is a working climatologist and I am very interested in her considered opinion. I guess she is too busy (or as it turns out later, maybe she does not actually have one?).
Ah! Here she is, on page four, as I suspected she has been too busy and she is back to "clarify the weaknesses in Tamino's review."
What follows is jaw dropping in its vacuity. She presents a long list of what turns out to be simple restatements of many fallacies from Montford's book with exactly zero references to anything tamino wrote. So nowhere is the promised "clarification" of any alledged weaknesses in tamino's article, or anything about "numerous factual errors and misrepresentations". Then, when soundly rebutted point by point by Gavin, (go read it, there is simply no contest) she has only this as her answer:
Gavin, the post I made in #167 was a summary of Montford's book as closely as I can remember it, sort of a review. I did not particularly bring in my personal opinions into this, other than the framing of montford's points. So asking me to retract a point made in a book in a review of that book is, well, pointless. your attempt to rebut my points are full of logical fallacies and arguing at points i didn't make. As a result, Montford's theses look even more convincing.
Here is the bald truth of the matter in her own words. She is simply parroting stuff she reads from denialists, plain and simple. Yet she presented it as her own opinion (just like before). That is not okay. I want to respect her opinions as a working climatologist but she is not even bothering to form her own opinions. She has no time to verify anything she says and she freely admits what she does say is motivated by knee-jerk reactions, not an independant assessment of the actual arguments and evidence. She did not like Gavin's rebuttal so that must mean Montford is right, no need for any thought of her own. It is really shameful, really.
And she is clearly just blustering about Gavin's responses. Just like "tamino's numerous errors", Gavin's "logical fallacies" will never be identified. He dignified her comment with a thorough point by point response, a response she did not even have the common courtesy to address.
Here is a sample of the points she said she finds convincing in Montford's book. She said:
1. The high level of confidence ascribed to the hockey stick inferences in the IPCC TAR, based upon two very recent papers (MBH) that, while provocative and innovative, used new methods and found results that were counter to the prevailing views. Plus the iconic status that the hockey stick achieved in the TAR and Al Gore's movie.
But the TAR only ever said the findings of this century and the 1990's being higher were "likely", that is hardly a "high level of confidence", I looked. And An Inconvenient Truth barely mentions this part of paleoclimatology, I looked. And what bearing does it have on the paper how one of its graph's is subsequently used? Sorry, wrong on the non-substantive points and completely lacking on substantive ones. Okay for your average anonymous blog commenter but where is her responsibility to her field of expertise?
2. The extreme difficulties that Steve McIntyre had in reproducing the MBH results. Any argument that defends these difficulties by saying that Steve McIntyre is incompetent or lacking in persistence is just plain counter to the evidence that Montford provides. Science needs to be reproducible. Period. And authors need to provide all of the data and metadata needed to reproduce the results, not just draft or incomplete datasets
I think at this point it is pretty safe to assume she has not bothered to examine the "evidence that Montford provides", she has admitted as much, so her reliance on it is hardly compelling though it is baffling. And as for reproducible science, study after study in the 12 years since MBH was published has come up with hockey stick after hockey stick. Get over it, it is simply reality.
3. The NAS North et al. report found that the MBH conclusions and "likely" and "very likely" conclusions in the IPCC TAR report were unsupported at that those confidence levels.
Another fail on matters of verifiable fact: MBH and the IPCC TAR never presented "very likely" conclusions. Facts matter! Gavin covers nicely what the NAS report did say.
4. A direct consequence of the North NAS report is that the conclusions in the IPCC AR4 essentially retracted much of what was in the IPCC TAR regarding the paleo reconstructions.
Well, she got wrong what the report said, so how can we expect her to know its consequences? I hardly know which is the more charitable explanation here, that she is bluffing to cover her weak position or she is as uninformed as she is vocal. The TAR says this:
New analyses of proxy data for the Northern Hemisphere indicate that the increase in temperature in the 20th century is likely7 to have been the largest of any century during the past 1,000 years. It is also likely7 that, in the Northern Hemisphere, the 1990s was the warmest decade and 1998 the warmest year (Figure 1b). Because less data are available, less is known about annual averages prior to 1,000 years before present and for conditions prevailing in most of the Southern Hemisphere prior to 1861.
The AR4 says this:
Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years. Some recent studies indicate greater variability in Northern Hemisphere temperatures than suggested in the TAR, particularly finding that cooler periods existed in the 12th to 14th, 17th and 19th centuries. Warmer periods prior to the 20th century are within the uncertainty range given in the TAR.
Where is the retraction of much of what the TAR said? There is only some change in nuance, more confidence in one aspect, less in another. Facts matter.
7. The Mann et al. 2008, which purports to address all the issues raised by MM and produce a range of different reconstructions using different methodologies, still do not include a single reconstruction that is free of questioned tree rings and centered PCA.
This is nothing more than an unthinkingly repeation of false accusations from denialist blogs. The third instance we have examined today. If she arrived on this lowly blog with such a comment we would all tell her to go read a real research paper for a change and be careful about believing everything she reads on he internet. No one would believe for a second that she is an actual researcher herself. Gavin's inline response is actually pretty restrained considering such an insulting lack of effort or integrity on Judith's part.
As I said, I am no expert in statistics so these are the non-technical points only. Gavin does not dodge, dissemble or digress in his responses to the technical points so it is a little difficult to come up with any reason for trusting Judith Curry's arguments. Or Montford's arguments rather, or I guess those are Steve McIntyre's points... whatever. If she can't be bothered to think for herself, I sure as hell can't be bothered to place an ounce of credibility on what she writes.
This is the first RC thread I've read through completely in a long time and it is worth doing, not only for the sad spectacle I am covering here but for interesting exchanges with seemingly knowledgable people. Gavin and tamino have provided a great number of inline responses so there is much education and entertainment. Judy gets beat up quite a bit but she sorely deserves it, I am embarassed for her.
[Oh, I also see there are two more pages I have to catch up on. Good grief, now she refers to her listing of Montford's points as "the points i made in my review of Montford's book". So when asked to defend them, they are someone else's, 100 comments later they are her's again! My head is spinning.]]
I'm sorry, but I really did expect more from her. Unless and until she owns up to this shameful display why should anyone ever take her seriously again? There are many sources of information out there, deciding which to trust is an important and time consuming task.
The list of reliabile sources in climatology just got a bit shorter.
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Curry is correct here. Mann's use of non-centered PCA was unjustified nonsense, and "Realclimate" should have let that sleeping dog lie, rather than defend that nonsense.
Imagine a meteorologist using data from weather balloons and satellites to predict weather 1 week out. Suppose a second
prognosticator adopted the ancient Roman system of reading the entrails of dead birds to make predictions.
Even if both accurately predicted weather 1 week out, the general consensus would be that the meteorologist's methods should be supported, and the second prognosticator's methods should be denounced.
Note that Judith Curry is NOT at apostate; she still believes in "The Good Word" of CAGW. She's just denouncing a "false prophet."
Alan D McIntire, you are just spouting denier rubbish as usual.
Get a life and start reading science papers not bumf from denier sites.
RE: Curry is correct here. Mann's use of non-centered PCA was unjustified nonsense
I haven't seen anyone attempt to defend non-centered PCA - in fact tamino says in the comments
Finally: none of that has anything to do with being robust. What makes it robust is that you get essentially the same PC for NoAmer ITRDB data using the MBH98 procedure, or the MM PCA procedure, or fully normalized PCA (a la Huybers). Hence that PC is insensitive to changes in the chosen method of PCA, i.e., itâs robust.
That it would have been a better idea to use full-centered and normalized PCA (as Huybers recommends) is my opinion. That the result would have been the same is a fact.
And the point is doubly moot since recent work (Mann et al. 2008) uses a method that doesnât involve any data reduction step for representing regional proxy networks.
A shame Dr Curry's recent comments at RC are no more substantial than those you'll find at, for instance, The Guardian's comment sections which usually contain "CAGW is a religion", "Al Gore is fat", "Sea ice is recovering", and "The corrupt peer review process...".
If she arrived on this lowly blog with such a comment we would all tell her to go read a real research paper for a change and be careful about believing everything she reads on he internet.
I'm afraid Mandas in particular would have insisted on stressing this very point.
Interesting post, Coby. I guess I've never really been in much of a fuss either way about the stick controversy. But thanks for keeping tabs on this.
The problem, in my view, is when a brilliant, prolific, sophisticated academic finally blunders, (s)he still regards her(him)self as a brilliant, prolific, sophisticated academic, and can't face the ugly truth.
I am an academic, but neither brilliant, prolific, nor sophisticated, so when I am wrong all I need is the wit to see it. Admitting it is never difficult. I have no exalted status to covet.
I always tell my students this (and myself in moments of renewal):
Your most potent intellectual attribute is not your IQ; its your honesty.
coby's presentation of JC on the RC trail is no exaggeration. She spews off a bunch of points which Gavin demolishes in detail; then denies that they are her points. And then takes ownership of them again later. Whew!
My impression of her original motivation was that she intended to be or build a bridge between the scientists and the "skeptics" by wanting to focus on how the scientists dealt (perhaps not as skillfully as could have been hoped) with the "skeptics". However, in this case she chose to build this bridge by sacrificing her trust in the integrity of scientists in a field with which she seems to have no background (paleoclimate studies) as a peace offering to the "skeptics": She swallows their view of events whole. I don't think she would do that to scientists in an area she actually knows something about (atmospheric studies).
Nonetheless, this kind of "splitting the difference" with the facts is completely inappropriate for a professional scientist, or for anyone with a sense of intellectual integrity. The fact that she is chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology is horrifying.
"Ill fares the land, to hast'ning ill a prey,
Where wealth accumulates, and men decay;
Princes and Lords may flourish, or may fade:
A breath can make them, as a breath has made;
but a bold peasantry, their country's pride,
When once destroyed can never be supplied."
I think today's peasants are the scientists. And they are under attack.
She continues to commit credibility suppuku over at Climate Progress ...
(she doesn't jump in until fairly deep in the thread, but Joe points to it in the main post)
To summarize, Mann created the "hockey stick" using non-centered Principal Component Analysis. McIntyre and McKittrick, and later Wegman, stated
that Mann's use of non-centered Principal component Analysis was flawed, and that the algorithm in effect was "searching for hockey sticks".
Mann et al at "realclimate", on January 6, 2005, stated that McIntyre and McKittrick were mistaken, and cited "Jolliffe" as an authority on PCA, stating that
non-centered PCA was a valid procedure.
Tamino later posted a series on "PCA" on his blog, "Open Mind". Part 4 was posted on March 6, 2008. In this posting he asserted that
non centerd PCA was perfectly okay, stating,
" You shouldn't just take my word for it, but you should take the word of Ian Jolliffe, one of the world's foremost experts on PCA..."
Finally there's a reply from Ian Jolliffe himself, who in effect said McIntyre and McKittrick's criticism was correct, and Mann's hockey stick
was based on dubious statistics.
From the January 6, 2005 "realclimate" post,
http://www.realclimate.org/index.php/archives/2005/01/on-yet-another-fa…
"6 Jan 2005
On Yet Another False Claim by McIntyre and McKitrick"...
"McIntyre and McKitrick (MM), in one of their many false claims regarding the Mann et al (MBH98) temperature reconstruction, assert that the âHockey Stickâ shape of the reconstruction is an artifact of the ânon-centeredâ Principal Components Analysis (PCA) convention used by MBH98 in representing the North American International Tree Ring Data Bank (ITRDB) data series. "...
"Contrary to MMâs assertions, the use of non-centered PCA is well-established in the statistical literature, and in some cases is shown to give superior results to standard, centered PCA. See for example page 3 (middle paragraph) of this review. For specific applications of non-centered PCA to climate data, consider this presentation provided by statistical climatologist Ian Jolliffe who specializes in applications of PCA in the atmospheric sciences, having written a widely used text book on PCA. In his presentation, Jollife explains that non-centered PCA is appropriate when the reference means are chosen to have some a priori meaningful interpretation for the problem at hand." ....
On March 6, 2008, "Open Mind" defended Mann's hockey stick.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-s…
"First letâs dispense with the last claim, that non-centered PCA isnât right. This point was hammered by Wegman, who was recently quoted in reader comments thus:
âThe controversy of Mannâs methods lies in that the proxies are centered on the mean of the period 1902-1995, rather than on the whole time period. This mean is, thus, actually decentered low, which will cause it to exhibit a larger variance, giving it preference for being selected as the first principal component. The net effect of this decentering using the proxy data in MBH and MBH99 is to produce a âhockey stickâ shape. Centering the mean is a critical factor in using the principal component methodology properly. It is not clear that Mann and associates realized the error in their methodology at the time of publication.â
Just plain wrong. Centering is the usual custom, but other choices are still valid; we can perfectly well define PCs based on variation from any âoriginâ rather than from the average. It fact it has distinct advantages IF the origin has particular relevance to the issue at hand. You shouldnât just take my word for it, but you *should* take the word of Ian Jolliffe, one of the worldâs foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation."
And finally we get a reply from Jolliffe himself:
http://tamino.wordpress.com/2008/08/10/open-thread-5-2/#comment-21873
"Ian Jolliffe // September 8, 2008 at 9:36 am
Apologies if this is not the correct place to make these comments. I am a complete newcomer to this largely anonymous mode of communication. Iâd be grateful if my comments could be displayed wherever it is appropriate for them to appear.
It has recently come to my notice that on the following website, related to this one, my views have been misrepresented, and I would therefore like to correct any wrong impression that has been given.
http://tamino.wordpress.com/2008/03/06/pca-part-4-non-centered-hockey-s…
An apology from the person who wrote the page would be nice.
In reacting to Wegmanâs criticism of âdecentredâ PCA, the author says that Wegman is âjust plain wrongâ and goes on to say âYou shouldnât just take my word for it, but you *should* take the word of Ian Jolliffe, one of the worldâs foremost experts on PCA, author of a seminal book on the subject. He takes an interesting look at the centering issue in this presentation.â It is flattering to be recognised as a world expert, and Iâd like to think that the final sentence is true, though only âtoyâ examples were given. However there is a strong implication that I have endorsed âdecentred PCAâ. This is âjust plain wrongâ.
The link to the presentation fails, as I changed my affiliation 18 months ago, and the website where the talk lived was closed down. The talk, although no longer very recent â it was given at 9IMSC in 2004 â is still accessible as talk 6 at http://www.secamlocal.ex.ac.uk/people/staff/itj201/RecentTalks.html
It certainly does not endorse decentred PCA. Indeed I had not understood what MBH had done until a few months ago. Furthermore, the talk is distinctly cool about anything other than the usual column-centred version of PCA. It gives situations where uncentred or doubly-centred versions might conceivably be of use, but especially for uncentred analyses, these are fairly restricted special cases. It is said that for all these different centrings âitâs less clear what we are optimising and how to interpret the resultsâ.
I canât claim to have read more than a tiny fraction of the vast amount written on the controversy surrounding decentred PCA (life is too short), but from what Iâve seen, this quote is entirely appropriate for that technique. There are an awful lot of red herrings, and a fair amount of bluster, out there in the discussion Iâve seen, but my main concern is that I donât know how to interpret the results when such a strange centring is used? Does anyone? What are you optimising? A peculiar mixture of means and variances? An argument Iâve seen is that the standard PCA and decentred PCA are simply different ways of describing/decomposing the data, so decentring is OK. But equally, if both are OK, why be perverse and choose the technique whose results are hard to interpret? Of course, given that the data appear to be non-stationary, itâs arguable whether you should be using any type of PCA.
I am by no means a climate change denier. My strong impressive is that the evidence rests on much much more than the hockey stick. It therefore seems crazy that the MBH hockey stick has been given such prominence and that a group of influential climate scientists have doggedly defended a piece of dubious statistics. Misrepresenting the views of an independent scientist does little for their case either. It gives ammunition to those who wish to discredit climate change research more generally. It is possible that there are good reasons for decentred PCA to be the technique of choice for some types of analyses and that it has some virtues that I have so far failed to grasp, but I remain skeptical. "
Ian Jolliffe
Straight from the horse's mouth
You just have to weep reading stuff like
and
All non-centered PCA does (as opposed to centered PCA) is to push deviations from the calibration period into the first PC. It's an eigendecomposition, for crying out loud, and you get the same result as long as you take the eigenvectors that correspond to signal and leave the ones that correspond to noise, and there are objective methods to tell which are which by looking at the eigenvalue spectrum. The only reason Mann et al. should have avoided non-centered PCA is so they wouldn't have to listen to ignorant hacks whine about it for twelve years. Sheesh.
Hell hath no fury greater than that you guys seem to reserve for a colleague who looks like she might be jumping ship from (or rather questioning one small aspect of!)the True Religion.
I have often heard it said that many climate scientists and scientists from other related disciplines are wary of expressing even the slightest dissent for fear of the backlash to career prospect and of provoking the combined ire of the "concensus". I now see what they were afraid of.
Nice work, guys, here, on Real Climate and Climate Progress ( and although I have not looked yet, doubtless already or soon on Desmogblog and Stoat, etc) . The Spanish Inquisition could take lessons from you.
Ugly stuff. Even if you are completely correct in every aspect this was an unjustifiably brutal mobbing. If you turn out to have been mistaken, I wonder how you could live with yourselves.
Professional scientific courtesy in climate science died today. You should be ashamed. I am ashamed to witness it.
For all you deniers who insist that there are two sides, yes you are right there are two sides. On one side, "real scientists" who are honest and on the other, you deniers whose only stock in trade is lies, deception, cherry picking and other forms of scientific malfeasance.
You guys are pathetic, what will your mothers think of you when they see what disgrace you are bringing to your families.
I think the issue, Jack, is more that Judith is making obvious errors, showing poor understanding of the current literature, parroting claptrap, while acting like some neutral parental arbiter scolding errant children. It's actually embarrassing for someone of her standing.
I think Coby presents a nice summary of the issue (which you seem to ignore to play something akin to a tone troll).
On one side you have Wegmann, Steve McIntyre, and Jolliffe,
REAL statistics. On the other, you have amateur statisticians Mann, Wahl, etc. This is a case of dubious statistics being defended, and it has nothing to do one way or the other about true belief in CAGW.
Learn a little about the subject matter before you go around denouncing people.
The use of decentered, non-centered, short centered or whatever you want to call it was improper as many have admitted. It was also inconsequential to the result, which is a fact that "skeptics" need to come to grips with.
When I read this post this morning I was initially taken aback at the intensity of feeling in some of the comments. I do have some sympathy with Ian's view re the savaging of JC, and it may well be that he is correct re the opinion of the turning against one's own. Its sort of like the 'woman scorned' metaphor - you are more scathing in your criticisms of someone who you believe is acting like a traitor, rather than someone who you always accepted as your enemy.
That being said, I believe there are a couple of issues here. The first is the statistical issue of the use of non centred PCA by Mann etc. And I am going to stay WAY out of any discussion in that regard. I tried to do some reading on it, and the maths are way out of my league and my head nearly exploded when I tried to understand it (but then, statistics were never my strong suit even if I do have a basic understanding).
The second is the actions of Dr Curry and some of her comments on other blogs. I do have some sympathies with the views of Dr Curry, in that it would be nice to be able to have a rational discussion with the deniers and focus on the issues rather than setting ourselves up in opposing camps. Unfortunately, I think she is being naive. Of course, scientists can have a rational discussion with the likes of Steve MacIntyre (even if they don't agree with him) because he at least approaches the subject from a rational perspective. But he is in a VERY small minority, and most of the deniers out there have no idea what they are talking about, and they just parrot the opinions of others who also have no idea what they are talking about (think Anthony Watts for example) and speak from a dogmatic, preconceived worldview sans evidence.
I also have sympathies with her opinion that science needs to be open and transparent, but I do believe she takes the view too far by suggesting that all data be freely available to all who wish to access it. That is impractical, and would result in every armchair expert with an opinion and a calculator (but no science training) spending all their time critiquing the views and wasting the time of scientists with questions and comments.
I had a read through some of the comments etc that have been linked to in the thread, and I believe coby has a point regarding some of the comments that Dr Curry made on the issue. This one in particular does concen me:
"....The whole host of issues surrounding whether or not he is biased, the plaigarism accusation, and whatever else, are issues that I have not investigated in any detail (and donât intend to). So my comments on this should not receive any undue consideration; they were made when i thought my mention of the Wegman Report was going to be hijacked by the plaigarism issue being raised at deepclimate. This is last word on that subject, and request that Keith not allow any more comments on this topic of plaigarism...."
I have stated in this forum on numerous occasions (too many to count probably) that people should refrain from commenting on an issue until they have read what they are commenting on. To me at least it is a statement of the obvious, but it is surprising how many people fail to follow it. Unfortunately, Dr Curry seems also have failed to follow it, by commenting on something that she has not read in any detail (by her own admission), then dismissing criticism and attempting to change the subject when she gets called on it (remind you of anyone?). In my opinion, that's pretty poor, especially coming from someone with who repeatedly pushes the issue of scientific ethics.
However, to be fair, if you continue to read the thread you will notice that Dr Curry does moderate her statements somewhat, even admitting to an 'error of judgement on the issue' at one point in the thread (sorry I can't find the quote again - its a very long thread and I didn't mark it when I read it). So I'm going to give her the benefit of the doubt here. I have a lot of respect for what she is trying to do (even if I do disagree with some of her opinions), and I'll just put it down to a bad day rather than trying to savage her.
McIntyre, you know nothing about what you are telling us. Please read up on Wegmann's deceit at Deep Climate. It shows him up for the uneducated shyster that he is, pretending to be an academic.
As for Jolliffe, he is a theoretical statistician who does not want to get his hands dirty actually studying real life statistics. Why should anyone take his word that one statistical method is good and another is bad? That is typical of an academic ego.
As I said above all you deniers have is lies, deception, cherry picking and other forms of scientific malfeasance.
Why you are unable to see this for yourself only shows that you are in a terminal case of DKS.
"I think the issue, Jack, is more that Judith is making obvious errors, showing poor understanding of the current literature, parroting claptrap, while acting like some neutral parental arbiter scolding errant children. It's actually embarrassing for someone of her standing."
No. That is YOUR issue. MY issue remains as stated. People are behaving abominably.
On the subject of YOUR issue perhaps you would care to speculate on why Ms.Curry has (according to you) suddenly started to behave in what, given "her standing", is presumably an uncharacteristicly "embarrassing " way?
Go on. Let yourself go. Classical Greek Hysteria perhaps? A sudden preoccupation with kittens?
If you will not say it, doubtless someone else will.
That's cool, Jack. Clutch your pearls in horror that some think Judith is making a fool of herself and have clearly said so.
But the fact remains that *Dr* Curry has been making some rather egregious errors. Coby has outlined many of them in his post.
As to why she seems to be expressing such behaviour - I have absolutely no idea.
"The use of decentered, non-centered, short centered or whatever you want to call it was improper as many have admitted."
You concede the point- that's what Curry was pointing out on
Tamino's "Realclimate" post.
"It was also inconsequential to the result,which is a fact that "skeptics" need to come to grips with."
Posted by: cce | July 26, 2010 6:02 PM"
No, using crap mathto come to the right result is NEVER justified. If I derived 166/664 = 16/65= 1/4 by
canceling out the sixes, my math sucks, and the fortuitous accident that I got the right answer is irrelevant
I actually thought that Joliffe was pretty unfair. He states:
"It gives situations where uncentred or doubly-centred versions might conceivably be of use, but especially for uncentred analyses, these are fairly restricted special cases."
And reading his presentation he does outline those restricted 'special cases'. On slide 24 he specifically states anomaly data (population means of 0, sample means non-zero). He might not endorse the approach, but he does outline situations when it could conceivably be used.
With statistics it's not always a case of criticising 2+2=5, but more a situation of having several methods which can be applied. Some more or less ideal than others depending on data and question - and I think we can all agree that the non-centred PCA was probably less ideal than other approaches.
But we can verify how robust a particular finding is by applying different statistical approaches (and why perseverating on non-centred MBH 98/99 is little more than navel gazing 12 years on).
What you don't seem to comprehend is that non-centered PCA isn't 'crap,' just marginally sub-optimal. The fact that it produces almost identical results to centered PCA isn't fortuitous at all.
Maybe Judith is more like a vegetable korma, than a curry?.
Alan, could you please show us where Judith Curry pointed to the PCA issue (and was correct)?
If the whole issue was about the short-centered PCA, discussions would have stopped in 2000 already (last used in 1999). It isn't. Montford's book is filled with errors, several of which are pointed out by Tamino. Curry then claims Tamino is wrong. When asked to identify some points, she comes with a summary of Montford's book. Gavin points to MANY mistakes in those claims, upon which Curry suddenly (and angrily!) claims these are not *her* claims, but merely a summary of Montford's claims. Which brings us back to Curry not answering to the request of pointing out Tamino's errors...
And she openly admits to it on climateprogress! She admits she has no intention to dig deeper into the claims from either side! She just acts as a conduit. For some vague reason we are supposed to read Montford's book to learn...errr....something, regardless of whether its claims are right or wrong (and as shown, Judith apparently learned a few things that were outright false from reading that book).
A rationally acting person would have looked at the responses by Gavin, and scratched his/her head. "Gee, did I get it so wrong? I should become more skeptical".
There are really two issues here. PCA is a system for weighting several measurements into 1 or 2 principle components. An alternative method is just to take all the
components and run a multi-linear regression.
When you weigh 20 or 30 factors in creating a regression line, you are practically "bound" to get a regression with 5% TO 3% significance using just the calibration data. That means, if something happens by chance only 5% of the time, and I select from 20 factors, there's a reasonable chance that 1 of those 20 factors will give a result significant within 5%.
You also need a "test" period to see if your results are actually significant, or just a case of "data mining".
I see at this link
http://climateaudit.org/2010/07/25/repost-of-tamino-and-the-magic-flute/
that the verification was worked out for the "non calibrated" period, and an r^2 of between 0.018 and 0.189 was obtained over the different periods.
A typical interpretation of a low squared statistic combined with a higher RE statistic is that they deal with overfitting - the "model" for calculating the past temperature depends on too many variables. At any rate, the predictions can't be trusted. The RE statistic is spuriously high only due to self-correlations of the proxies in the calibration period.
It seems that once you analyze papers that were proposed as evidence for "extraordinary" warming in the 20th century, you will see that they are based on estimates of the temperature in the past millenium that look like worthless noise and guessing.
Mann's tree ring analysis is about as reliable as Roman Augurs' analysis of birds' intestines.
Alan, remove the tree rings, and you get essentially the same result. Abandon PCA, and you get the same result. Boreholes? Again essentially the same result. Others looking at tree rings? Again essentially the same result.
A robust result, almost independent of the method, investigators, and of the proxies that are used. Sad state of affairs when people then still make such a big deal.
Oh, and we're still waiting for Steve McIntyre to finally publish HIS paleoclimate reconstruction.
Has anyone ever tried to solicit a "consensus" among statistical experts regarding this controversy? Is that what the NAS report claims to be?
I think that we (that is all thinking people) can see what McIntyre's agenda is. All he can quote is back to climatefraudit. What a joke.
Are you related to SM? Maybe blood is thicker than neural networks.
Skip, the answer to your question would be twice a no. The NAS report did do a lot more than the Wegman report, but didn't have that many statistical discussions. And having had some run-ins with statisticians, I'm sure we can find statisticians arguing both ways.
The more I see of what she writes, the less impressed I am. Regarding how she handled the Deep Climate v Wegman thing, I find her parting comment (as noted by mandas above) downright creepy:
So she started with some very strong language against DC, later admitted she had no clue on the subject, then seemed to think that the best thing for everyone is to have the subject swept under the rug by moderation! (Huh?) It's almost as if reality has to be altered to put her in the best light possible; and that it's a good thing.
I've known people like her before. They know they're right. They know they're reasonable. They know they're polite. Anything they do or say must be described that way, no matter what. Any dissension will be viewed with hurt, suspicion, anger and mistrust and will be categorized as the opposite of their fantasy of themselves: wrong, unreasonable and impolite.
Notice my name is spelled "McIntire". I'm no relation to Steve "McIntyre".
The big point is, tree ring proxies are worthless.
McIntire said:
And just what level of expertise do you have that you can make this assertion? Quoting climatefraudit doesn't count as a source of credible information.
Have you ever heard of Dunning Kruger Syndrome? You are a prime example.
"The big point is, tree ring proxies are worthless."
This may be McIntire's (and McIntyre's) "big point" but it is hardly the big point for policy, IPCC findings, or even paleoclimatolgy TODAY.
Without going into the political issue of just what you're measuring, ask a disinterested statistician what an r^ of 0.018 implies
I'd imagine they'd ask you just what you're measuring.
Uh, she claims that Mann '08 still uses PCA. This is a false statement.
Joliffe: "I am by no means a climate change denier. My strong impressive is that the evidence rests on much much more than the hockey stick. It therefore seems crazy that the MBH hockey stick has been given such prominence ..."
Wegman: "Time to move on"
http://ncf.uschamber.com/wp-content/uploads/resources-the_deniers_12200…
I think Ian Forrester has nailed our friend Mr McIntire perfectly. Google his name and you will be staggered by how many places he posts and the wide range of topics that he professes an expertise in (not bad for someone with an undergraduate degree in physics who sings in a barbershop quartet and picked up his expertise in statistics in 2008 by reading a basic introduction to statistics textbook - apparently).
"The big point is, tree ring proxies are worthless."
Fine. Throw the tree rings away and re-do the analysis. (this was done in Mann 2008). You get the same result.
None of the supposedly killer criticisms of the hockey-stick that have been bruited about in the denia-sphere all these years have had any material effect on the result he got.
None of them. Not one. Zip. Nada. Nothing.
Mike Mann could have printed his '98 paper in the blood of dozens of sacrificial statisticians, then danced naked in front of the Wegman panel singing 'I despise Chi-squared tests and all who cleave to them' and it would not matter. The result is robust, repeatable and has been independantly replicated.
The hockey wars are over and you guys lost. Deal with it.
Regards
Luke
danced naked in front of the . . . panel singing 'I despise Chi-squared tests and all who cleave to them' . . .
You jest, but this is damn near what I had to do in my last revise-and-resubmit.
Speaking of Wegman:
http://deepclimate.org/2010/07/29/wegman-report-update-part-1-more-dubi…
This time, Iâm looking at section 2.2 (see Wegman Report PDF at p. 15), which gives the background of key statistical concepts, including Principal Component Analysis. Astonishingly, even this section appears to contain a significant amount of unattributed material from other sources, although quite a bit less than the other sections. Again, Wikipedia appears to be a key source, along with a couple of text books.
So now all three sections of the Wegman report background sections have been shown to have material "strikingly similar" to unattributed antecedents. (Previously I had looked at the background sections on proxies and on social networks).
It's also worth noting that Wegman et al spend many pages of the report on "short-centred" PCA, yet studiously avoid the whole issue of PC retention/selection, not to mention all of the peer-reviwed scientific critiques of M&M (i.e. Wahl and Ammann 2007 in Climatic Change, and the Huybers and von Storch GRL comments).
We don't have to do science by swaggering analogy. That's why whenever factuality or the truth are the criteria, we win. We don't need to say Lindzen/Akasofu/Kramm/Gehrlicher/Spencer/whoever's XXX is as useful/scientific/believeable as . We don't bother.
Another reason they lose - like the IDists and creationists who always fight science as it was when they started fighting, they don't realize it moves on.
We have good match of tree rings as proxies with other proxies. We have good matches with the actual temperature record. Very late in the game, around the 1960s, we have a divergence that increased and in a fairly smooth, measurable, even predictable pattern. We now have more insights into why.
So what makes up our fossil record is not frozen in amber. :)
LOL!!!! Same experience here! Oh, I'm still laughing---if you said that in person I'd be buying you and your friends your choice of beverage. :-))))
I'm interested in the comments to Dr. Oppenheimer at RP Jr's blog*, bearing in mind the furore over the 'flack' Prof. Curry has received. These are edited extracts for flavour (Tom Fuller will be proud I'm sure...):
"Such analyses are no better than astrology"
"A study like this...is delibrately playing the racist card."
"This is nothing more than political lobbying wrapped up in science themed wrapping paper."
"Geez, this is pathetic"
"This story is just the kind of daft alarmism that confuses rather than informs"
"Does this blatantly shoddy work not call into question everything else ever done by this scientist?"
Now, don't get me wrong, I don't think the study is that great (not for the same reasons as Pielke & Tol), though to be honest I only skimmed it. But I find it interesting that these comments attacking the author of a published paper (and having the grace to respond in person to Pielke Jr's previous blogpost) exist unheralded when comments attacking A.N.Other blog commenter who happens to be a University professor have garnered widespread opprobrium.
(Crossposted at Deltoid)
* http://rogerpielkejr.blogspot.com/2010/07/michael-oppenheimer-responds…
Mandas, you make a disparaging remark about my singing in a barbershop quartet as a hobby. He would be shocked to find that Max Plank and Harry Truman played the piano, and Werner Heisenberg had a reputation as the best ping pong player in the physics community.
I assume you picked it up from this link:
http://wmbriggs.com/blog/?p=465
William Briggs was reviewing a musical theory book
"The central problem is this: how many and at what steps do you divide the interval between octaves, where an octave is a doubling (or halving) of a frequency (or tone). In other words, how do you create notes."
I segued into the topic by mentioning my hobby,
"I sing in a barbershop quartet. A few years ago someone coaching us mentioned that the different notes on a pitch pipe are not scaled perfectly- That means when the lead sings a C note, the tenor doesnât sing the E on the pitch pipe, but a note a hair lower than that to get the perfect harmony. The person singing the G should sing a note a hair higher than the pitch pipe G to produce a perfect harmonic.
I hadnât given this a thought previously, but I immediately realized that since 3/2 and 5/4 donât have rational 12th roots, the 12 steps on a piano scale must be a compromise between a perfect pythagorean scale and an ability to play in differnet keys.
This math forum thread gives a pretty clear explanation."
http://mathforum.org/library/drmath/view/52470.html
A pretty simple formula, really, which even a high school student should be able to understand- it hardly takes any
"expeertise".
As to the statistics, you must be referring to this:
http://rankexploits.com/musings/2008/falsifying-is-hard-to-do-%CE%B2-er…
"1. I became aware of autocorrelation on reading Climate Audit. Iâm sure either side of the alpha beta argument
could counter with the argument that year to year temperature fluctuations are not completely random, but dependent on previous yearsâ temperatures..."
Note that I didn't state that I had been unfamiliar with
linear correlation or statistics, only that I had been unfamiliar with AUTOcorrelation. Autocorrelation comes up in TIME series, like daily stock prices and daily temperatures, where the figures are not random, but dependent on yesterday's figures. It takes TIME for temperatures to heat up or cool down. The net result is
the correlation stays the same, but the significance level goes down.
Back to my point on the meaning of a correlation of 0.018. I'll ignore tests of significance- whether you have enough data to make any statement about confidence intervals, which Mann did not have.
For example, say you have a century sample of random temperatures, with a mean set to 0 and a standard deviation of 0.3C. Your best guess for a temperature will be that zero mean, and your average miss will be 0.3 C.
Now run a tree ring match with a validated correlation of
0.018
When the ACTUAL temperature is + 0.5 C, your test will
give 0.18*.5 = .09 C on the average. Your average
guestimated MISS will decrease by a factor of
(1 - (0.018)^2)^0.5 times the original,
or from 0.3 C in my example to 0.2995C
Alan
Nothing disparaging about my remark at all - simply an observation. You have very diverse talents, which is obvious from the number of subjects that you have an opinion on.