Guest commentary by Tamino
Update: Another review of the book has been published by Alistair McIntosh in the Scottish Review of Books (scroll down about 25% through the page to find McIintosh’s review)
Update #2 (8/19/10): The Guardian has now weighed in as well.
If you don’t know much about climate science, or about the details of the controversy over the “hockey stick,” then A. W. Montford’s book The Hockey Stick Illusion: Climategate and the Corruption of Science might persuade you that not only the hockey stick, but all of modern climate science, is a fraud perpetrated by a massive conspiracy of climate scientists and politicians, in order to guarantee an unending supply of research funding and political power. That idea gets planted early, in the 6th paragraph of chapter 1.
The chief focus is the original hockey stick, a reconstruction of past temperature for the northern hemisphere covering the last 600 years by Mike Mann, Ray Bradley, and Malcolm Hughes (1998, Nature, 392, 779, doi:10.1038/33859, available here), hereafter called “MBH98” (the reconstruction was later extended back to a thousand years by Mann et al, 1999, or “MBH99” ). The reconstruction was based on proxy data, most of which are not direct temperature measurements but may be indicative of temperature. To piece together past temperature, MBH98 estimated the relationships between the proxies and observed temperatures in the 20th century, checked the validity of the relationships using observed temperatures in the latter half of the 19th century, then used the relationships to estimate temperatures as far back as 1400. The reconstruction all the way back to the year 1400 used 22 proxy data series, although some of the 22 were combinations of larger numbers of proxy series by a method known as “principal components analysis” (hereafter called “PCA”–see here). For later centuries, even more proxy series were used. The result was that temperatures had risen rapidly in the 20th century compared to the preceding 5 centuries. The sharp “blade” of 20th-century rise compared to the flat “handle” of the 15-19th centuries was reminiscent of a “hockey stick” — giving rise to the name describing temperature history.
But if you do know something about climate science and the politically motivated controversy around it, you might be able to see that reality is the opposite of the way Montford paints it. In fact Montford goes so far over the top that if you’re a knowledgeable and thoughtful reader, it eventually dawns on you that the real goal of those whose story Montford tells is not to understand past climate, it’s to destroy the hockey stick by any means necessary.
Montford’s hero is Steve McIntyre, portrayed as a tireless, selfless, unimpeachable seeker of truth whose only character flaw is that he’s just too polite. McIntyre, so the story goes, is looking for answers from only the purest motives but uncovers a web of deceit designed to affirm foregone conclusions whether they’re so or not — that humankind is creating dangerous climate change, the likes of which hasn’t been seen for at least a thousand or two years. McIntyre and his collaborator Ross McKitrick made it their mission to get rid of anything resembling a hockey stick in the MBH98 (and any other) reconstruction of past temperature.
Principal Components
For instance: one of the proxy series used as far back as the year 1400 was NOAMERPC1, the 1st “principal component” (PC1) used to represent patterns in a series of 70 tree-ring data sets from North America; this proxy series strongly resembles a hockey stick. McIntyre & McKitrick (hereafter called “MM”) claimed that the PCA used by MBH98 wasn’t valid because they had used a different “centering” convention than is customary. It’s customary to subtract the average value from each data series as the first step of computing PCA, but MBH98 had subtracted the average value during the 20th century. When MM applied PCA to the North American tree-ring series but centered the data in the usual way, then retained 2 PC series just as MBH98 had, lo and behold — the hockey-stick-shaped PC wasn’t among them! One hockey stick gone.
Or so they claimed. In fact the hockey-stick shaped PC was still there, but it was no longer the strongest PC (PC1), it was now only 4th-strongest (PC4). This raises the question, how many PCs should be included from such an analysis? MBH98 had originally included two PC series from this analysis because that’s the number indicated by a standard “selection rule” for PC analysis (read about it here).
MM used the standard centering convention, but applied no selection rule — they just imitated MBH98 by including 2 PC series, and since the hockey stick wasn’t one of those 2, that was good enough for them. But applying the standard selection rules to the PCA analysis of MM indicates that you should include five PC series, and the hockey-stick shaped PC is among them (at #4). Whether you use the MBH98 non-standard centering, or standard centering, the hockey-stick shaped PC must still be included in the analysis.
It was also pointed out (by Peter Huybers) that MM hadn’t applied “standard” PCA either. They used a standard centering but hadn’t normalized the data series. The 2 PC series that were #1 and #2 in the analysis of MBH98 became #2 and #1 with normalized PCA, and both should unquestionably be included by standard selection rules. Again, whether you use MBH non-standard centering, MM standard centering without normalization, or fully “standard” centering and normalization, the hockey-stick shaped PC must still be included in the analysis.
In reply, MM complained that the MBH98 PC1 (the hockey-stick shaped one) wasn’t PC1 in the completely standard analysis, that normalization wasn’t required for the analysis, and that “Preisendorfer’s rule N” (the selection rule used by MBH98) wasn’t the “industry standard” MBH claimed it to be. Montford even goes so far as to rattle off a list of potential selection rules referred to in the scientific literature, to give the impression that the MBH98 choice isn’t “automatic,” but the salient point which emerges from such a list is that MM never used any selection rules — at least, none that are published in the literature.
The truth is that whichever version of PCA you use, the hockey-stick shaped PC is one of the statistically significant patterns. There’s a reason for that: the hockey-stick shaped pattern is in the data, and it’s not just noise it’s signal. Montford’s book makes it obvious that MM actually do have a selection rule of their own devising: if it looks like a hockey stick, get rid of it.
The PCA dispute is a prime example of a recurring McIntyre/Montford theme: that the hockey stick depends critically on some element or factor, and when that’s taken away the whole structure collapses. The implication that the hockey stick depends on the centering convention used in the MBH98 PCA analysis makes a very persuasive “Aha — gotcha!” argument. Too bad it’s just not true.
Different, yes. Completely, no.
As another example, Montford makes the claim that if you eliminate just two of the proxies used for the MBH98 reconstruction since 1400, the Stahle and NOAMER PC1 series, “you got a completely different result — the Medieval Warm Period magically reappeared and suddenly the modern warming didn’t look quite so frightening.” That argument is sure to sell to those who haven’t done so. But I have. I computed my own reconstructions by multiple regression, first using all 22 proxy series in the original MBH98 analysis, then excluding the Stahle and NOAMER PC1 series. Here’s the result with all 22 proxies (the thick line is a 10-year moving average):
Here it is with just 20 proxies:
Finally, here are the 10-year moving average for both cases, and for the instrumental record:
Certainly the result is different — how could it not be, using different data? — but calling it “completely different” is just plain wrong. Yes, the pre-20th century is warmer with the 15th century a wee bit warmer still — but again, how could it not be when eliminating two hand-picked proxy series for the sole purpose of denying the unprecedented nature of modern warming? Yet even allowing this cherry-picking of proxies is still not enough to accomplish McIntyre’s purpose; preceding centuries still don’t come close to the late-20th century warming. In spite of Montford’s claims, it’s still a hockey stick.
Beyond Reason
Another of McIntyre’s targets was the Gaspe series, referred to in the MBH98 data as “treeline-11.” It just might be the most hockey-stick shaped proxy of all. This particular series doesn’t extend all the way back to the year 1400, it doesn’t start until 1404, so MBH98 had extended the series back four years by persistence — taking the earliest value and repeating it for the preceding four years. This is not at all an unusual practice, and — let’s face facts folks — extending 4 years out of a nearly 600-year record on one out of 22 proxies isn’t going to change things much. But McIntyre objected that the entire Gaspe series had to be eliminated because it didn’t extend all the way back to 1400. This argument is downright ludicrous — what it really tells us is that McIntyre & McKitrick are less interested in reconstructing past temperature than in killing anything that looks like a hockey stick.
McIntyre also objected that other series had been filled in by persistence, not on the early end but on the late end, to bring them up to the year 1980 (the last year of the MBH98 reconstruction). Again, this is not a reasonable argument. Mann responded by simply computing the reconstruction you get if you start at 1404 and end at 1972 so you don’t have to do any infilling at all. The result: a hockey stick.
Again, we have another example of Montford implying that some single element is both faulty and crucial. Without nonstandard PCA the hockey stick falls apart! Without the Stahle and NOAMER PC1 data series the hockey stick falls apart! Without the Gaspe series the hockey stick falls apart! Without bristlecone pine tree rings the hockey stick falls apart! It’s all very persuasive, especially to the conspiracy-minded, but the truth is that the hockey stick depends on none of these elements. You get a hockey stick with standard PCA, in fact you get a hockey stick using no PCA at all. Remove the NOAMER PC1 and Stahle series, you’re left with a hockey stick. Remove the Gaspe series, it’s still a hockey stick.
As a great deal of other research has shown, you can even reconstruct past temperature without bristlecone pine tree rings, or without any tree ring data at all, resulting in: a hockey stick. It also shows, consistently, that nobody is trying to “get rid of the medieval warm period” or “flatten out the little ice age” since those are features of all reconstructions of the last 1000 to 2000 years. What paleoclimate researchers are trying to do is make objective estimates of how warm and how cold those past centuries were. The consistent answer is, not as warm as the last century and not nearly as warm as right now.
The hockey stick is so thoroughly imprinted on the actual data that what’s truly impressive is how many things you have to get rid of to eliminate it. There’s a scientific term for results which are so strong and so resistant to changes in data and methods: robust.
Cynical Indeed
Montford doesn’t just criticize hockey-stick shaped proxies, he bends over backwards to level every criticism conceivable. For instance, one of the proxy series was estimated summer temperature in central England taken from an earlier study by Bradley and Jones (1993, the Holocene, 3, 367-376). It’s true that a better choice for central England would have been the central England temperature time series (CETR), which is an instrumental record covering the full year rather than just summertime. The CETR also shows a stronger hockey-stick shape than the central England series used by MBH98, in part because it includes earlier data (from the late 17th century) than the Bradley and Jones dataset. Yet Montford sees fit to criticize their choice, saying “Cynical observers might, however, have noticed that the late seventeenth century numbers for CETR were distinctly cold, so the effect of this truncation may well have been to flatten out the little ice age.”
In effect, even when MBH98 used data which weakens the difference between modern warmth and preceding centuries, they’re criticized for it. Cynical indeed.
Face-Palm
The willingness of Montford and McIntyre to level any criticism which might discredit the hockey stick just might reach is zenith in a criticism which Montford repeats, but is so nonsensical that one can hardly resist the proverbial “face-palm.” Montford more than once complains that hockey-stick shaped proxies dominate climate reconstructions — unfairly, he implies — because they correlate well to temperature.
Duh.
Guilty
Criticism of MBH98 isn’t restricted to claims of incorrect data and analysis, Montford and McIntyre also see deliberate deception everywhere they look. This is almost comically illustrated by Montford’s comments about an email from Malcolm Hughes to Mike Mann (emphasis added by Montford):
Mike — the only one of the new S.American chronologies I just sent you that already appears in the ITRDB sets you already have is [ARGE030]. You should remove this from the two ITRDB data sets, as the new version should be different (and better for our purposes).
Cheers,
Malcolm
Here’s what Montford has to say:
It was possible that there was an innocent explanation for the use of the expression “better for our purposes”, but McIntyre can hardly be blamed for wondering exactly what “purposes” the Hockey Stick authors were pursuing. A cynic might be concerned that the phrase actually had something to do with “getting rid of the Medieval Warm Period”. And if Hughes meant “more reliable”, why hadn’t he just said so?
This is nothing more than quote-mining, in order to interpret an entirely innocent turn of phrase in the most nefarious way possible. It says a great deal more about the motives and honesty of Montford and McIntyre, than about Mann, Bradley, and Hughes. The idea that MM’s so-called “correction” of MBH98 “restored the MWP” constitutes a particularly popular meme in contrarian circles, despite the fact that it is quite self-evidently nonsense: MBH98 only went back to AD 1400, while the MWP, by nearly all definitions found in the professional literature, ended at least a century earlier! Such internal contradictions in logic appear to be no impediment, however, to Montford and his ilk.
Conspiracies Everywhere
Montford also goes to great lengths to accuse a host of researchers, bloggers, and others of attempting to suppress the truth and issue personal attacks on McIntyre. The “enemies list” includes RealClimate itself, claimed to be a politically motivated mouthpiece for “Environmental Media Services,” described as a “pivotal organization in the green movement” run by David Fenton, called “one of the most influential PR people of the 20th century.” Also implicated are William Connolley for criticizing McIntyre on sci.environment and James Annan for criticizing McIntyre and McKitrick. In a telling episode of conspiracy theorizing, we are told that their “ideas had been picked up and propagated across the left-wing blogosphere.” Further conspirators, we are informed, include Brad DeLong and Tim Lambert. And of course one mustn’t omit the principal voice of RealClimate, Gavin Schmidt.
Perhaps I should feel personally honored to be included on Montford’s list of co-conspirators, because yours truly is also mentioned. According to Montford’s typical sloppy research I have styled myself as “Mann’s Bulldog.” I’ve never done so, although I find such an appellation flattering; I just hope Jim Hansen doesn’t feel slighted by the mistaken reference.
The conspiracy doesn’t end with the hockey team, climate researchers, and bloggers. It includes the editorial staff of any journal which didn’t bend over to accommodate McIntyre, including Nature and GRL which are accused of interfering with, delaying, and obstructing McIntyre’s publications.
Spy Story
The book concludes with speculation about the underhanded meaning of the emails stolen from the Climate Research Unit (CRU) in the U.K. It’s really just the same quote-mining and misinterpretation we’ve heard from many quarters of the so-called “skeptics.” Although the book came out very shortly after the CRU hack, with hardly sufficient time to investigate the truth, the temptation to use the emails for propaganda purposes was irresistible. Montford indulges in every damning speculation he can get his hands on.
Since that time, investigation has been conducted, both into the conduct of the researchers at CRU (especially Phil Jones) and Mike Mann (the leader of the “hockey team”). Certainly some unkind words were said in private emails, but the result of both investigations is clear: climate researchers have been cleared of any wrongdoing in their research and scientific conduct. Thank goodness some of those who bought in to the false accusations, like Andy Revkin and George Monbiot, have seen fit actually to apologize for doing so. Perhaps they realize that one can’t get at the truth simply by reading people’s private emails.
Montford certainly spins a tale of suspense, conflict, and lively action, intertwining conspiracy and covert skullduggery, politics and big money, into a narrative worthy of the best spy thrillers. I’m not qualified to compare Montford’s writing skill to that of such a widely-read author as, say, Michael Crichton, but I do know they share this in common: they’re both skilled fiction writers.
The only corruption of science in the “hockey stick” is in the minds of McIntyre and Montford. They were looking for corruption, and they found it. Someone looking for actual science would have found it as well.
The problem with the “hockey stick” is quite simple: it is a very effective graphic. Anyone, regardless of scientific background, can understand, and remember, it. Thus, it must be attacked with the greatest ferocity. Words are nowhere near as effective.
Re: Andy @ 38
I’m frustrated that discussions about “public” vs “private” email always degenerate to legal definitions of ownership. A far more important distinction, the first one you have to make before you can interpret any communication, is public vs. private *audience*.
Imagine that you have a teenaged child, and you overhear them saying to a friend, “Getting drunk tonight would be crazy”. You would likely ask yourself, “Does that mean crazy-stay-away or crazy-I-can-hardly-wait?” The key point is that when you intercept a private communication, the only meaning that matters is the one the *participants* attach to it. Your definition of “crazy” is irrelevant here. If you want to know what your kid is planning, you have to decide what “crazy” means to him or her talking to this friend. No other interpretation is valid.
In the same way, the CRU emails were private in that they were written for a specific audience. If you want to understand them, you have to do so within the context of the individuals directly in the conversation and their context. What do words like “Mike’s Nature trick” or “better for our purposes” mean to the people on the address list (and *only* them) at the time the author wrote the message?
This is simply the first step you have to take before you can make an honest interpretation of any communication that was intended for a limited audience—the key sense of “private” here. It’s not a mitigating factor or an excuse, it’s the essential first step to making sense of what you’re reading. Although context is a complex topic and linguists have detailed theories of deixis, the basic idea is simple enough and every adult makes use of it routinely when they overhear someone else’s conversation at a coffee shop. It says a lot about people like Montford that their argument ignores this basic skill of interpreting a private communication. It almost makes them look insincere.
Excellent Article Tamino–
This may be the most comprehensive single writeup on the internets surrounding the hockey stick and the efforts to get rid of the hockey stick.
I think your characterization: //”Montford’s hero is Steve McIntyre, portrayed as a tireless, selfless, unimpeachable seeker of truth whose only character flaw is that he’s just too polite”// is how many people view the situation only transparently. In fact, McIntyre thrives on the “I’m a victim” card. Even after the loss of Stephen Schneider, McIntyre couldn’t help but turn that into how Schneider kicked him off a journal editor job. It is rather sickening the nonsense he is allowed to get away with and put other researchers under the “conspirator” category, even if he himself will not say that in public.
Andy Revkin– With all due respect, your post is rubbish. The e-mails were private communications between scientists that were illegally taken, illegally distributed, severely misrepresented (by McIntyre especially, especially with respect to ‘hide the decline’), and used to score political points and attack the credibility of well-respected scientists.
#51
Indeed. Apparently it must be declared broken, over and over again.
This nonsense goes back to 2003 (some background here, detailing M&M’s co-operation with various think tanks, PR types and right-wing politicians):
http://deepclimate.org/2010/02/04/steve-mcintyre-and-ross-mckitrick-part-1-in-the-beginning/
http://deepclimate.org/2010/02/08/steve-mcintyre-and-ross-mckitrick-part-2-barton-wegman/
In all that time, McIntyre and McKitrick have published exactly one article in a peer-reviewed scientific journal (GRL in 2005), and none whatsoever since then.
What’s wrong with this picture?
Good one.
Meanwhile here in Australia, we have a federal election on, and both major parties are way off in lala land on climate change, supported by the Murdoch media.
The opposition “Liberal” Party leader is on record as saying climate science is “crap”, and the prime minister is proposing calling a “peoples assembly” to decide what to do … one better than legislating the value of pi: let’s call a meeting of citizens and decide what it should be.
I urge everyone here who can write coherently to write letters to the Australian media, and comment online. For my part I’m campaigning for the Greens because there is no other option.
It would be great if someone with real authority like James Hansen could write an article for one of the big newspapers. If anyone wants to share ideas, go to my blog (link on my name) and use the contact form.
off topic but raised at skepticalscience and puzzles me. Total water vapour data from 1983-> at ISCCP shows water vapour trending downward. I would have expected it to increase with increasing global temperature. The data seems at odds with precip water vapour trends. Can someone explain the anomaly to me please?
Thanks
[Response: ISCCP? Unlikely, that is a cloud monitoring project. Perhaps you mean NCEP which is a reanalysis, but be very careful here. These are weather models that assimilate observed data, but as observing systems and technology has changed, they often have apparent trends that are not climatic in origin. The water vapour in the upper troposphere is one example which is strongly affected by improvements in radio-sonde technology over time and the introdcution of satellite data in 1979. The trends are not robust in the other reanalysis products (ERA or JMA) and do not accord with direct observations. – gavin]
Revkin @ 38
Not seeing how a rather vacuous statement of UCS posture is background. Maybe digging into the relative merits of the British Information Commissioner’s Office actual position would be background.
If attacking a 1998 paper is all the deniers have, you have to wonder how anyone thinks they are at all credible.
It would be an interesting exercise to select a sufficient number for statistical significance of random papers in other fields of science, and try to recreate their results based on publicly available data, and compare that against the allegations against climate scientists. I started working in a biology lab after being in computer science for a couple of decades, and my experience in a field of large data sets created by people with no basic understanding of data representation has been … interesting.
Perhaps we could interest someone like George Monbiot in the outcome of such a study. He needs his perception that climate scientists are remiss because they are less than perfect hauled back to reality.
Mr. Revkin-
The Information Commissioner’s Office (ICO) has a site that explains Environmental Information Regulations. I think this page has some interesting information. The page begins by noting:
“The Environmental Information Regulations give you the right to obtain information about the environment held by public authorities, unless there are good reasons to keep it confidential.”
http://www.ico.gov.uk/what_we_cover/environmental_information_regulation.aspx
@52–“This is simply the first step you have to take before you can make an honest interpretation of any communication that was intended for a limited audience. . .”
True. The crucial words being “honest interpretation.”
Personally, I don’t believe for one second that “honest interpretation” was ever part of the hacker’s (or the denialist commentators’) intent. The goal was disinformation, pure and simple–the grotesque exaggerations which proliferated so quickly show that quite clearly.
48 (tamino),
Fair enough. I did understand exactly why you used quotes on centering when I read it. As I said, there was just an uneasy implication because of the way deniers use them. It was that and only that which reflected on your use.
On Jolliffe… I tried to go back to re-read his comments before posting. It’s been a while since I first read the thread, so I don’t remember it perfectly, but when I tried to find it to re-read it (and your excellent 4 part instruction on PCA, for which I thank you), it was gone: 404.
I did, however, just find a copy of one part of the thread on (ick) climateaudit.org. That particular comment by Jolliffe certainly does not refute the use of decentered PCA. It is far more nuanced. I do remember that he was also more clear in following comments on the thread, but again, those are now lost.
Whatever the case, I think I have little choice but to accept your position and retract my objection. If you are comfortable with your phrasing (and again, my attitude is simply that the cold facts weigh so strongly on Mann’s side that no special tactics are necessary), then it can and should stand.
#38 (Andy Revkin and Gavin’s reply)
In the US when government agencies are making regulations and enforcing these regulations there are ample opportunities for public involvement. Rules allow this, but these rules at times limit how much public involvement can occur. The public’s right to know is balanced with the agencies’ duty to carry out their responsibilities.
It sounds like the call for openness in science is often an end run around these restrictions. I have to agree with Gavin that 100% openness is not workable.
The data in the first, second and third plots in no way resemble a hockey stick. They show no overall warming trend.
Only when the instrument data set is grafted on to these plots does a hockey stick like figure appear.
A reasonable person would make the observation that the instrument data set should not be superimposed on to these plots. It is somewhat deceptive.
[Response: Sigh….And where is the ‘grafting’ in these plots, exactly?–eric]
IIRC, essentially Jolliffe said that Mann’s explanation in MBH98 (IIRC) wasn’t sufficiently detailed for him to determine exactly what Mann had done, so he didn’t take an explicit position, other than to grumble that this novel approach should’ve been documented better with more detail. He also, in essence, grumbled against needless novelty, and also had questions whether PCA was the best approach in the first place but said he hadn’t looked into it in sufficient detail to say yeah or nay (but was aware that non-PCA approaches led to a hockey stick, and made clear he wasn’t arguing against the validity of that).
I’d say it was the typical grumbling of a perfectionist, who first arrived pissed at Tamino because of a simple misunderstanding centered around “centered” IIRC. He was a bit aloof and held himself aloof from the analytical POV (i.e. didn’t think Mann provided enough detail for him to understand Mann’s brand of PCA, but didn’t follow up by e-mailing Mann or otherwise seeking more info). He wants to do theoretical stats, not mess around in the mud with science, is my read.
If Tamino or others think my recollection is wrong, I hope they chime in, but since apparently the thread’s gone, we’re going on recollection.
Doug Bostrom #45, very true.
But, imagine if this were to happen anyway — what an opportunity for academic investigation of the journalistic process, its foibles and weaknesses, and especially its dishonesty and corruption — which we are all very well aware of of course, but have rarely witnessed at first hand!
Evidence is evidence. Legalistic nonsense aside, wouldn’t this be great?
Just joking. Only just.
Andy Revkin wrote:
“One aspect of this saga that I think needs to be disabused is the notion that these were “private” emails. They may have been perceived by the communicators as private conversations, but nearly all of the e-mail exchanges were done by people operating with public funding or, in some cases, on government e-mail accounts.”
I’m a mathematician at the University of California who has an NSF grant. So you’re saying that the emails I send using the computer at my university aren’t “private”? That’s news! The University of California has a privacy policy that says “An electronic communications holder’s consent shall be obtained by the University prior to any access for the purpose of examination or disclosure of the contents of University electronic communications records in the holder’s possession, except as provided for below” – where the exceptions are for things like subpoenas, emergencies and so on. So, faculty typically communicate using email with the expectation that nobody is spying on them.
“MBH98 had originally included two PC series from this analysis because that’s the number indicated by a standard “selection rule” for PC analysis.”
…
“But applying the standard selection rules to the PCA analysis of MM indicates that you should include five PC series.”
Could you explain briefly the difference, please? I don’t see why, when analysing the same data, MBH98 was perfectly correct to use two PCs but the MM analysis must use instead five PCs. Otherwise, skeptics might argue that, if two PCs were good enough for MBH98, then that number should be good enough for MM when attempting to replicate the results…
[Response: They might argue that, but that would be out of ignorance. Its easy to demonstrate with synthetic examples that the selection criteria are a function of the centering convention and that different conventions do lead to different estimated eigenvector cutoff levels. This is shown in the links provided in the article, and demonstrated in exhaustive detail by Wahl and Ammann (2007). –mike]
Response: Sigh….And where is the ‘grafting’ in these plots, exactly?–eric]
The plot under the title:
Finally, here are the 10-year moving average for both cases, and for the instrumental record:
Extreme rain event: In Iowa, the corn and soybeans are high, but many fields are now flooded and the crop is ruined. We have had a whole year’s worth of rain already this year. This is the third super-wet year in a row. Saw it on local TV.
Thanks Gavin for those caveats. I am getting the data from ISCCP,
http://isccp.giss.nasa.gov/products/browseatmos.html
total column water vapour. Not a lot of metadata but maybe I havent searched hard enough. Data is post 1983, and variable description is:
“This parameter represents the total precipitable centimeters of water vapor in the atmosphere and is determined from analysis of satellite infrared sounder data (NOAA operational analysis). Since the result comes from measurements of absorption at infrared wavelengths, the results are strictly valid only for relatively cloud-free locations (cloud cover fraction over a 300 km region less than about 60%). The original data report water vapor amounts for three layers covering the lowest part of the troposphere (approximately from the surface to the 300 mb level — there is only a very small amount of water vapor above this level) and are sampled at intervals of about 300 km and 1 day.”
Graphs posted in a comment at skepticalsci originated at
http://www.climate4you.com/ClimateAndClouds.htm but do seems to the data from ISCCP.
[Response: Thanks. I wasn’t aware of that data. First impressions are that this has a number of artifacts in it likely due to inhomogeneities in the satellites (varying levels of spatial coverage through time as satellites drop in or out). The definitive precipitable water vapour analyses are discussed in Chapter 3 of AR4, and I’d start with those publications and authors to see what the differences are with the ISCCP product. – gavin]
This article itself is a piece of good news. I have never been happy with those well meaning comments which have simply argued that the first MBH papers are out of date or some such. One of the main motives behind the continuing attack on them is not to alter the conclusions but to discredit the authors and by implication anyone who belongs to the same community as them.
Its a powerful article but I have one concern:
Re #44
I couldn’t agree more. That would help a lot. Either that or another book or best of all both. The article would be easier to follow for readers who have read your previous five articles on the hockey stick .. especially part 5.
There are of course all the other topics. Its like losing an admission ticket to a library.
There is one small point forgotten about here concerning the MBH98 algorithm/methodology.
When tested with stationary (no trend) noise the algorithm still produces a hockey stick. Therefore the method cannot be classified as “robust” or having any merit.
[Response: Well, I’m sure you’ve done the calculations for this (being a ‘thinking scientist’), and so I’m curious as to why you don’t mention the fact that the amplitude of such an artifact is an order of magnitude smaller than the actual HS in the data? The reason that the final reconstruction is robust is precisely because the signal is in the data. But let’s be clear, if you don’t like the original method, fix all the supposed problems and do it over. Oh yes, already done. – gavin]
I think the realclimate regulars might do well to follow Judith Curry’s advice and actually read Andrew Montford’s book.
It was very obvious on for example the Guardian panel that it came as a surprise to the other panel members that Mcintyre had shown little interest in the CRU crutem record. Clearly Monbiot, Watson et al. criticise McIntyre without actually reading much of what he has to say.
Even if you are not inclined to support sceptical views I think as a scientist that it is always preferable to read for oneself what is being said and to form your own views rather than just confirming your prejudices by listening dyed in the wool critics.
With so many of the realclimate regulars now apparently doing this, this blog is beginning to feel a just a little claustrophobic.
[Response: For McIntyre was ‘not interested’ in the crutem record is completely laughable. It is a trivial matter to go over to his site, do a search, and find direct links — clearly and unambiguously supported by McIntyre — to other sites directly claiming fraud, data manipulation, etc. The panel members you refer to may have been surprised, but this doesn’t mean they didn’t see through this false claim. –eric]
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.
[Response: Grading on the Curry Curve perhaps?
Judith, the fact is that endless repetitions of allegations of corruption do not make them true. Really, do you think that collaborators having a ‘purpose’ is some terrible indictment of their research? Tamino has demonstrated clearly that Montford’s book is full of errors and insinuations that have no basis in fact. And now you come along and tell us that, no those weren’t the important bits at all, it’s the other stuff. Which you still haven’t actually described. You might find it amusing to play hunt the thimble, but excuse me if I find it a little tiresome. Please make your actual point. – gavin]
#63–“The data in the first, second and third plots in no way resemble a hockey stick. They show no overall warming trend.”
To my eye, both statements are false.
True, the instrumental record–which is not “grafted,” but simply shown in parallel using a different color–makes the overall shape more dramatic. But it doesn’t, IMO, create a whole new shape. And most of the reason that the instrumental record creates a more dramatic “hockey stick” is that–unlike the proxy data–it extends up to the present, which supplies something like 15 years of warming.
You know Julian, that is the point, it’s the instrumental record, the part that really sticks up in the air, that makes the curve a hockey stick. Of course, that is the part of the record we know best, but since the proxys follow the instrumental curve in the validation period we have some confidence in them, and since, as Tamino points out, the more proxys we add the more confident we can be, and we can even take a bunch out and get more or less the same behavior, why yes, there is a problem.
63 (Julian),
How can you possibly arrive at an adjective like “deceptive?” It’s clearly shown without the instrument record first, and then with the instrument record very, very clearly separated in contrasting red and labeled, so that one can easily see how closely the proxy measurements match the instrument record.
What more can possibly be done? How can you claim “deception?”
As far as:
This is the problem with graphs. They’re interpretation is fuzzy, so people can see what they choose to see.
But if you look at the ten year running average (the thick black line), you can clearly and indisputably see that from 1400 to a little past 1900, the range of values fluctuates erratically between about -0.25 and -0.6˚C. This is obvious and indisputable.
After that time, the range abruptly rises from the previous range all the way up to a maximum of a little less the +0.1˚C, and a minimum of about -0.1˚C, and does not drop back down into the previous range. ———/
Lastly, if you google “hockey stick mann” you get 234,000 results. Everyone else on the planet has been calling this a hockey stick, and suddenly you claim that you can’t see it? There simply is no warming trend in the graph?
There’s a word for this. Let me see, what was it? It starts with a “d,” I think. It’s right on the tip of my tongue. No, wait, don’t tell me, I’ll get it…
This.
And also, the proxies had to be used for periods before we started keeping temperature records. But now, we can actually measure GHG concentrations and temperature directly. Duh. So, there’s not that much interest any longer in studying most of the proxies going forward. It’s hard work, it costs money, and what exactly is the purpose when we can measure the stuff directly now?
[Response: There’s still much important work to be done–and being done–on proxy-based analyses. Also, keep in mind that proxies are not just for temporal extension into the pre-instrumental past–they are also useful (esp tree rings) for spatial interpolation in the more recent past, and present. There are still some real interesting and important issues to work out, as you allude to at the end.–Jim]
Ah, but some would argue that we still need to see how the proxies track temperature and GHG concentrations into the future because this is an indication of how well they tracked in the past. Right? Only, pre-industrial revolution, mankind wasn’t affecting the climate *at all*. Now it looks like we’re messing with it to such an extent that we’ve invalidated some of the proxies. For instance, it is thought that the reason why (some of) the northern hemisphere pines don’t track temperature very well since about 1960 (hide the decline, hide the decline!) may have anthropogenic causes which result in drought constraining the poor things, and also allow less sunlight to reach them. But the science isn’t in yet on this one, so we can’t say with certainty. Pity, that.
Julian@63
“Only when the instrument data set is grafted on to these plots does a hockey stick like figure appear.
A reasonable person would make the observation that the instrument data set should not be superimposed on to these plots. It is somewhat deceptive.”
My interpretation of this is that you are saying that if we want to get an understanding of temperature trends on centennial or millenial timescales, we should wilfully ignore the higher-precision instrumental record in favour of the lower-precision proxies. Is that correct?
If so, then why? If not, then what are you driving at?
Regards
Luke
This dispute is more about whether tree-rings are a proxy at all. The shocking hockey stick temperature uptick brought attention onto itself and it was not surprising that someone stood back and said – “is this really a true thing?” After all, wood shrinks, and old ring widths would necessarily look thinner and new rings wider, falsely implying rapid tree growth in later years. This dispute was inevitable and will continue till better proxies are found. Until then, please stop relying on tree-rings to tell a story of temperature.
[Response: Actually, you are incorrect, tree rings can be good climate proxies. But remember that this is a paper that more than 10 years old. Research has moved on and indeed, other proxies are increasingly being used. Perhaps you might find it surprising, but the basic picture whether you use tree rings or no tree rings at all is very similar. – gavin]
[Response: You have some real serious misconceptions about tree rings, about which there is a vast literature coming from multiple disciplines. You can start to correct that here and here.–Jim
As the link in the article shows, George Monbiot does indeed offer apologies for his previous assessment of the e-mail scandal and his indictment of Phil Jones, which is laudable (although personally I find Monbiot’s final sentence “..I’d conclude that Phil Jones should hang on – but only just” extremely irritating – just who does he think he is?)
However, one of the points raised in his article is the following:
“1. The loss of Chinese weather station documents. A paper written in 1990 by Phil Jones, who later became the CRU head, claimed that almost all the Chinese stations whose data he was using had stayed put. This claim was used to argue that the rising temperatures in those places could not have been caused by creeping urbanisation. It later emerged that most of them had in fact moved, that many of the records of their locations had been lost, and that Jones and his co-author appear to have been reluctant to admit it.”
As a semi-regular visitor to many of the reality-based climate sites, I missed this part of the story. If it doesn’t stray too far off-topic, can anyone enlighten me about what this is all about?
Dear Tamino,
I have a small point and a bigger point I would like you to comment on:
The small one is:
– You talk about 4 years for the Gaspe data, R. McKitrick writes (here: http://www.uoguelph.ca/~rmckitri/research/McKitrick-hockeystick.pdf) about that “The data begin in 1404, but the chronology is based on only one tree up to 1421 and only 2 trees up to 1447. Dendrochronologists do not use site data where only one or two (or zero!) trees are sampled. In fact the authors who originally sampled the Gaspé data don’t use any of the data before AD1600”
And a bigger one (for which I really would like to see how much everyone can aggree on..)
– The Graybill-Idso proxies seem to be flawed in a sense that they don’t represent a valid temperature proxi. So by not using them, we should expect a better result, right!?
(This is actually a point where M. Mann’s work gets highly doubious for me, since he seems to have known about issues with these proxie and did not mention so in his publication)
As a result of this “correction” the heckeystick only appears in the PC4 isntead of PC1. There is a big difference between PC1 and PC4 (as you know with no doubt):
The dominant pattern is in PC1, PC2 is the PC of the residuals ..
So if you find some signal in the residuals^3 of the signal for a dataset which is “not too rich in information” to start with . . isn’t that fairly “unimpressive”?
How much does the statistical confidence degrease by this change?
I find it particulary “alarming”, that when a neccesary correction is done, most of the result (the confidence drops more than two orders of magnitude) disapears.
RE: Gavin’s reply to #72
I don’t need to do the calculations myself as they were clearly shown in MM2005 (GRL):
“Without the MBH98 transformation, a 1 SD hockey stick occurs in the PC1 only 15.3% of the time (1.5 SD – 0.1%). Using the MBH98 transformation a 1 SD
hockey stick occurs over 99% of the time, (1.5 SD – 73%; 1.75 SD – 21% and 2 SD 0.2%”
[Response: Well, if you done it yourself, you would have seen the differences in amplitude. But it really is moot, don’t use that convention and the answer is the same. – gavin]
RE: #67 if in MBH98 the Hockey Stick result lies in PC2 and this method fails red noise tests, and in MM03 it appears in PC4 then just exactly what do the MAIN signals in the proxy record in PC1 (MBH98) or MM (PC1, PC2 and PC3) correspond to in the climate record? After all, a look at the Hockey Stick result suggests that climate was pretty much flat (slightly declining) for 600 years and yet apparently the Hockey Stick (with its enormous deviation and variance) does not appear in PC1. Why not?
[Response: You are confusing one element in the proxies (the north american tree rings) with the whole thing. PC’s are just a way of reducing data – they do not come with obvious interpretations necessarily. Sometimes they can be clearly seen to be related to known phenomena (for instance the first PC for tropical Pacific temperatures is closely related to El Niño), but not always. Multi-proxy methods like this look for patterns in the data that are correlated to other proxy records and the target temperature data and so purely local elements, whether climatic or not, get down-weighted. The test of whether this is useful is whether you have some predictability in the validation interval, and whether the basic patterns hold up when you add more data, change the method, hold back some data etc. And they are. – gavin]
JC:
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.
Claims implying that valid points offering utility for discussion are censored from view on RC are a regular occurrence, novel perhaps for somebody new on the scene. Dig up old threads on RC and one may see that if there’s a legitimate complaint to be made about moderation of comments on this site it’s more probably the inordinately permissive instincts of the moderators, frequently allowing threads to be filled with noisy and distracting rubbish.
Anyway, there are simple methods to address this putative problem but they won’t wash without honesty on the part of those making comments. As an example, RC could set up a generic /dev/nul thread where posts not deemed to have any utility could be dumped for public perusal. Unfortunately such a scheme will only be satisfactory if those claiming to have had posts deleted are honest and of course we have no way of making a final determination on that question. “My comment was deleted” is naturally susceptible to circular logic; the supposed invisibility of a comment is a strange form of a final and incontrovertible argument.
hveerten #81: long story. You could start here, item 2:
http://www.uea.ac.uk/mac/comm/media/press/CRUstatements/guardianstatement
Executive summary: the denialist lie that the contested station location change information would in any way be essential for the 1990 paper’s conclusions is shown to be poppycock. You get the same result if you do correct for the effect of station location changes, which the 1990 paper did not but the 2008 paper did. It’s just “nice to know” info not used in the actual (1990) analysis.
The statement in the 1990 paper is probably wrong, but why and how is lost in the mists of history — this was two decades ago for crying out loud. Stuff happens. The charge of fraud was ludicrous on its face. See also
https://www.realclimate.org/index.php/archives/2010/02/the-guardian-disappoints/#more-2808
scroll to Part 5 esp. the end!
RE #52 Ted Kirkpatrick wrote :
“Imagine that you have a teenaged child, and you overhear them saying to a friend, “Getting drunk tonight would be crazy”. You would likely ask yourself, “Does that mean crazy-stay-away or crazy-I-can-hardly-wait?” The key point is that when you intercept a private communication, the only meaning that matters is the one the *participants* attach to it. Your definition of “crazy” is irrelevant here. If you want to know what your kid is planning, you have to decide what “crazy” means to him or her talking to this friend. No other interpretation is valid. ”
This is a perfect analogy. To further the analogy, if you are already suspicious of your teenager drinking, you would likely assume “crazy” to mean “I can hardly wait”. When people already skeptical of scientists or AGW are spoon fed quotes like “hide the decline” from stolen emails, they are likely to assume the worst. This is exactly what happened.
Is it possible to have a “green slope” version of Mr. Tamino’s analysis in “The Monford Delusion”, i.e. in everyday language? I have started a blog called the Climate Pioneer (theclimatepioneer.org) in which I aim, among other things, aiming to translate credible climate change science into common-speak for people like myself with a science background but who are at the same time not grounded in climate science jargon. Such a translation would be invaluable to me and in turn to many others who want to be able to address climate change naysayers in intelligent yet accessible language. Thanks.
I hope to see Andy Revkin reply to John Baez, 23 July 2010 at 1:24 AM
Andy, you know who John Baez is.
Deal with this please.
Re: Edward Greisch says:
22 July 2010 at 3:18 PM
“13 Brian Angliss or somebody: Could you please trace where M&M get their money to do all of their anti-science? We know it has to be the fossil fuel industry, but more a specific path and the information on how much would be useful.”
Yes that’s right. Anybody, anywhere that dost protest or criticize any piece of climate science, clearly must be in the employ of Big Oil.
Bash the deniers as conspiracy theorists and theorize about the big oil conspiracy all at once. Migraine inducing irony, bravo.
gavin@80 “tree rings can be good climate proxies” They CAN if you pick the right ones. But who picks them? The dispute is that only CERTAIN trees are used – the ones that conform to other proxies. It would be in the best interest of science to abandon tree rings altogether – and formally withdraw the hockey stick graph.
[Response:The dendrochronologists pick sites based on their knowledge of likely response patterns of particular species/site combinations. Don’t post any more until you show that you have spent at least 15 minutes trying to understand even the first rudiments of a topic that have been known for over a century. It won’t fly here, won’t even stumble along.–Jim]
31, I think Tamino was using the C convention of counting from 0 :). It is actually paragraph 7.
RE: #83
Firstly, thank you for allowing my response through as this is the first time this has happened to me. I am sure a more open debate will benefit all (see also JC comment repeated at #84).
However, your reply to #83 states “The test of whether this is useful is whether you have some predictability in the validation interval, and whether the basic patterns hold up when you add more data, change the method, hold back some data etc. And they are. – gavin]”
I have 2 questions:
1. So why then do Briffa and others exclude post-1960 temperature data as part of the validation period?
[Response: ‘others’? There is a well known problem with a certain class of tree ring density records that briffa et al have worked on. As you certainly do know, this is something that affects their proxies post 1960, even while they correspond to other proxies and instrumental data earlier. This is clearly an issue, and is being looked into by many groups. Doesn’t affect mbh98 or any of the subsequent Mann et al papers though. If you don’t like this, feel free to discount these proxies until it is resolved. – gavin]
2. Both MBH98 and WahlAmman2007 fail a significance test on R. (I am aware MBH98 did not quote R, but it was shown by MM that it would fail this test). Please can you identify a statistical authority (eg Cressie, Ripley etc) with a section or page number as to why it does not matter that neither of these reconstructions pass a significance test for R and yet R is widely used in similar proxy reconstructions elsewhere (including my own proxy reconstruction work)? The explanation in WahlAmman2007 is based on a clearly artificial example, not a general case.
[Response: the metric you look at for any particular application depends on what it is you are trying to assess. The low r2 values are associated with year to year variability which is not really what is being looked for, rather you want a statistic that works at capturing the general level. The RE score does that and demonstrates that there is skill (which obviously decreases as you go back in time). The way you should look at this is that the metric you use defines what you can infer from the reconstruction. So at 1450 say, you can’t trust the year-to-year variability, but the longer term average is more skillful. -gavin]
Re Doug @ #84. I can see where this is headed. Soon they will be claiming that their posts are being deleted from the “dumped” thread, and thence, a call for a “dumped from the dump” thread, and so on until the entire internet consists of nothing but RC threads…
re: #74 JC and seriousnesses
I have actually read the book, and noted that many things are missing, like:
– any discussion of predecessor attacks&buildup: Essex&MKitrick’s 2002 “Taken by Storm”, the CEI/Ebell recruitment of McKitrick, the CEI/GMI support of M&M, coaching, promoting M&M in Washington, DC, M&M being GMI “experts”, being introduced to Inhofe, publicized in the WSJ, etc, etc … i.e., the material covered by Deep Climate and others, such as CCC, Section 5, and Appendix A.10.4.
The discussion of the Barton hearings and Wegman Report (WR) is mainly on pp.249-262 of HSI.
Deep Climate had demonstrated clear “striking similarities” (that’s the legal term commonly used for plagiarism) of text between the WR and Raymond Bradley’s 1999 book, here and here. The tree-rings discussion was modified to introduce “confounding” and invert a key Bradley conclusion.
Then DC showed the same for Social networking text Some plagiarism can be arguable. Text that is 50%+ cut-and-paste, plus trivial rewordings of the sort often done by student to evade plagiarism-detection software, and modest rephrasings, is not… Some of that material showed up later in a journal for which Said was an associate editor, and Wegman a long-time advisor, impressively moving Received to Accepted in 6 days, and citing 3 separate government contracts for support. Of course, that journal generally has not published Social Network Analysis, unlike the sister Elsevier journal Social Networks, a far more relevant journal. However, SN’s editors/editorial board might have been a problem, given that 1 was one of them was one of the plagiarized authors and 2 were coauthors/colleagues of other plagiarized authors.
Dr Curry wrote 04/25/10 @ Collide-a-scape, regarding Deep Climate:
“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.
Wegman is very unpopular with the warmists because his 2006 NRC report was very critical of the statistics used by mann et al. in the creation of the hockey stick. Prior to summer 2006, Wegman had no apparent interest or involvement in climate science or politics.
He was asked to chair this effort by the NRC since he was Chair of NRCs Committee on Applied Statistics. When asked to explain the greenhouse effect, he really didn’t know anything about the physics of how it worked. So I don’t think you could have gotten a more unbiased person to do this review. To see such a respected academic accused in this way (with the accusations so obviously baseless) is absolutely reprehensible.”
and then 04/26/10.
“On comment regarding my comments on Wegman (not the Wegman report per se). 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 don’t 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 politely ask: has Dr. Curry explicitly withdrawn “reprehensible” and apologized to Deep Climate yet? I could not find any such, but maybe I have missed it.
====Notes.
Of course, he was not asked by the NRC to do this, but by via Jerry Coffey.
Regarding not understanding greenhouse effect, I’ve read the testimony. He may or may not have understood that, but repeatedly evaded questions about it. He was willing to admit temperature had risen. He was *not* willing to admit any CO2-temperature connection, often saying he was just a statistician. The WR report in effect dismissed it as “correlation is not causation.”
However, that did not stop him from often talking/writing about tree-rings, bristlecone pines, the 1990 IPCC chart, boreholes, and social networks. He claimed a narrow focus on MBH98/99, but the WR summarized many of the later papers (badly), and cited even more.
As for unopopularity, people might want to look at the 2007 ASA invited workshop @ NCAR, October 2007. The participants were distinguished climate scientists and statisticians with climate expertise. The presentations were interesting. I found statistician Jim Berger’s talk a useful perspective, especially comments on pp.17-19.
This looks like a high-expertise workshop of people trying to make progress. Now, take a look at the Wegman talk. I’m not sure the audience would have been thrilled by slides 2-4. I’d hazard a guess that being shown book covers by Crichton(1), Singer(2), Michaels(2) probably didn’t go over well.
Being asked 21 questions, of which a few seemed reasonable, but most were easily answerable in the literature, or even directly answered in the NRC report, or by Gerald North at the Barton hearings … probably wasn’t received positively. I suspect Slide 30 was not well-received.
I suspect that in 2007, using the TAR hockey stick as background may not have been a felicitous choice, although it certainly does resemble the cover of HIS, although without the horizontal bar.
@85, Martin Vermeer,
thanks for that. I had already read that RC post, but must have forgotten about the Chinese weather stations. I did indeed notice that this dates back to ’90, and would therefore have dismissed it out of hand for the non-story that it is clearly shown to be in your link, if it wasn’t for the fact that George Monbiot saw a need to bring it up in the article where he makes his excuses. Shows that he almost gets it, ‘but only just’ not completely gets it.
In all, this is so very, very tedious and tiresome, even for a bystander like me. I can only imagine the exasperation of the scientists involved. I did a “grep ‘trick’ * -R” on my source code directory containing computer code written by colleagues and myself, and got enough results to be very happy that I am active in a completely uncontroversial field of research (astronomy)…
This is OT, but I need help answering a denialist who wrote (when I suggested WV is a positive feedback, responding to the warming caused by CO2, enhancing the warming further):
[blockquote]The water vapour positive feedback theory has already been comprehensively disproven by independent investigations by Douglass, Lindzen, Paltridge and Spencer, inter alia (who used satellite data and radiosondes to reach their conclusions and showed that the posited feedbacks are either missing or negative). The water vapour theory suggests that a small increase in CO2 will result in a large positive feedback loop from water vapour and this feedback loop will lead to dangerous warming. If this were true though, we would see a hotspot about 12km above the equator – as the “climate models” predict, no such hotspot has materialised though, which essentially invalidates the theory. VW amplification is conjecture, with no evidence that matters in the real-world.[/blockquote]
I suppose he’s talking about clouds and Lindzen’s iris hypothesis.
Hi Gavin,
Also on your reply to #83 states “The test of whether this is useful is whether you have some predictability in the validation interval, and whether the basic patterns hold up when you add more data, change the method, hold back some data etc. And they are. – gavin]”
Well, somehow I see the opposite .. If you improve the proxies used in MBH98 by throwing out some Pines which are non-temperature Proxies more than 99% of your result disappears. This looks just like the opposite of what you are saying .. particulary in the light that the method used in that paper was shown to sometimes mine hockey-sticks out of noise.
[Response: You are very confused I’m afraid. Quantitative methods actually come up with numbers that can be checked by anyone. Your ‘99%’ is just pulled out of your .a**e. Look, the charge that the HS is simply a statistical artefact is just wrong. If you switch to a more standard centering it is still there. If you drop the north american tree rings, it is still there, if you include more recently published proxies, it is there, if you dump the tree rings altogether, it is still there. It’s there because the planet really is warming. Why is this such an issue for you? It doesn’t have any influence on the attribution of current climate changes to human forcings, it doesn’t impact the radiative properties of CO2, so really, why do you care so much that you are willing to just make up stuff? – gavin]
RE: Doug Boston #84
“Claims implying that valid points offering utility for discussion are censored from view on RC are a regular occurrence”
I have had far more comments moderated at RC than actually appear posted but I have never been snipped, moderated or edited at any other site including climateaudit.org, bishophill.squarespace.com, wattsupwiththat.com and others. But I bet this comment won’t get through and if it does the names of those websites will be replaced by [edit] as they always have been in the past. I have previously pointed out that this type of moderation is self-defeating for RC. If you let this post through in its entirety then fair play and respect to the moderator for taking the time and thank you for listening.
Doug Boston your argument is circular and does not stand up: if you set up somewhere for those moderated posts to go then the criticism that relevent posts are moderated would be somewhat assuaged. However you then say “Unfortunately such a scheme will only be satisfactory if those claiming to have had posts deleted are honest and of course we have no way of making a final determination on that question.” Nonsense. If all posts rejected appear on an unthreaded, dated post for rejected comments then clearly if they appear there then they were posted. Although not an ideal arrangement I for one would be happier with that because at least my right of reply has then been partially allowed.
The other problem would be what to do with posts that were rejected immediately by the automatic filters – which might (intentionally or accidentally) contain offensive words or statements. Well those could appear as simply a reference to poster, time and date but without the potentially offensive words, perhaps on a separate list. Providing the two lists documented time and date of ALL submissions and the content of those that did not get automatically deleted then the criticism by JC (and myself) of RC would be somewhat mitigated.
If RC doesn’t want to do this then I am afraid you will have to accept that to many interested in this debate your legitimacy will remain somewhat compromised.
RE: #92 Gavin says:
[Response: the metric you look at for any particular application depends on what it is you are trying to assess. The low r2 values are associated with year to year variability which is not really what is being looked for, rather you want a statistic that works at capturing the general level. The RE score does that and demonstrates that there is skill (which obviously decreases as you go back in time). The way you should look at this is that the metric you use defines what you can infer from the reconstruction. So at 1450 say, you can’t trust the year-to-year variability, but the longer term average is more skillful. -gavin]
Thank you for your reply. Your answer makes little sense – how can an arbitrarily scaled proxy variable like tree ring data relate reliably to reconstruction of the mean in the past but the obvious year to year variability that dominates tree ring record is somehow irrelevant and secondary? This appears to turn the evidence back to front.
But if you note from my original post the question I asked was:
“Please can you identify a statistical authority (eg Cressie, Ripley etc) with a section or page number as to why it does not matter that neither of these reconstructions pass a significance test for R and yet R is widely used in similar proxy reconstructions elsewhere (including my own proxy reconstruction work)?”
What is the statistical authority for it being acceptable to fail an R test for this type of data and still claim the result statistically significant?
[Response: This just isn’t that complicated. I find something I want to predict based on information that I have that I think is related to the thing I want to predict. I can create any metric I want to test the prediction in the validation period. That might be r2, RE, CE or the RMS error or anything else. Each of these is a measure of some different aspect of the prediction. I can also create a monte-carlo simulation using random noise to examine the distribution of that statistic using my reconstruction method to determine what significance would imply (i.e. how large or small does that statistic need to be to exceed 95% of the random cases). By doing that, you can find under what circumstances your method is skillful. The aspects of the reconstruction that show skill (in this case the long term mean, but not the year to year variability) are things that are worth pursuing. This is very general. If you don’t like a particular metric for some reason, or you think that one other metric is more useful, then fine, publish a paper showing what you conclude from the data. It really isn’t that important. – gavin]
Good thing too. We know who dominates most discussions on unmoderated blogs about climate. The test has already been done. The results can be seen everywhere. Just consider the Guardian’s ‘Comment is Free’ (CIF) for example. Its a variation of the ‘gish gallop’ rhetorical technique. Instead of flooding the argument with a large number of incoherent points, the thread is swamped by a vast number of posters. Nothing is rationally discussed and the set of comments are rendered worthless. It was at its worst just after the Email theft when the comments were about 100 to 1 in favour of a lynch mob.
But JC appears to use an opposite logic i.e. that the discussions on RC are of no value because of an assertion that some posts don’t make it.
Incidentally I suspect that some posts may not make it for other reasons, e.g. mistakes or faults at the poster’s end but I can’t prove it. Some may just be delayed providing the grievance collector with ammunition.