Back to reporting on our presentation to the NAS panel, after which I’ll report on Mann. We presented last in the day, immediately following von Storch. Hughes and Mann presented on Friday morning. We gave them a long written presentation, and touched the high points in our PPT, also providing them with a CD of our papers. Our PPT presentation is cited in the NAS "other materials"; our "handout" is mentioned but not cited.
In deciding what to present, we decided to primarily focus on our own published work (i.e. out MBH critiques) . Like von Storch, we gave some answers to the Boehlert questions, not realizing that the panel seemed to be distinguishing its task from answering the Boehlert questions. Because the Divergence Problem grew legs in the early afternoon session, we added a couple of slides to our PPT presentation on the run, showing that it was not just a “few” series and that Briffa et al had not “explained” the problem, as well as adding a few slides from my AGU presentation showing statistical problems with the multiproxy studies as a group. Much was left unsaid.
The approach in our presentations will be pretty familiar to readers of our material. However, we varied the exposition a little from previous expositions both to reflect both the audience and the situation. We placed a lot more emphasis on MBH describing itself as a “new statistical approach”. The discrepancy between authors proposing a "new statistical approach" and MBH reluctance to disclose details of that approach had been an issue raised in Anderson et al [2005] in sharp terms by third party econometricians. MBH98 had said that they took a "new statistical approach" because they found "conventional approaches" to be " relatively ineffective."
If you have a set of proxies that are supposedly temperature proxies, then the most common "old statistical approach" would be to standardize the proxies and take an average. We showed the difference between the MBH reconstruction and a simple mean in the figure shown below. So the "new statistical approach" applied to MBH98 proxies obviously yields quite different answers than a conventional approach.
Figure 1. Top – mean of 415 proxies after standardization; bottom – MBH98.
We classified the principal aspects of the “new statistical approach” as being
1) temperature PCs reified as “climate fields”;
2) Mannian PCs applied to tree ring networks
3) a sui generis* multivariate methodology in the regression step applied to the post-tree ring PC proxies.
We placed more emphasis on (3) than in prior expositions, because the full measure of MBH data mining is not the difference between the no-PC MBH result (which concedes the sui generis multivariate method) and MBH98, but between the mean of all the proxies and MBH98. I’ve become increasingly frustrated at ad hoc use by climate scientists of sui generis multivariate methods with no citation of third-party statistical literature on confidence intervals or other statistical properties. (Hegerl et al, submitted, presented at the NAS panel is merely another example.)
We also drew attention to three main MBH claims that, in our opinion, led to widespread acceptance of MBH in the field: (1) statistical skill in RE, r and r2 statistics; (2) robustness to the presence/absence of dendro indicators; (3) confidence intervals. I don’t remember many questions from the presentation, but here I remember Cuffey asking me on what basis we were making these claims: as sociologists? I didn’t have a very snappy answer for this; I just said that we were simply trying to put the matter in context for this presentation. With a little time to think about it, I’d say that I have extensive experience in examining offering documents for securities for promotional aspects and have considerable practical experience on disclosure requirements in securities offerings, including practical knowledge of what constitutes a representation in such an offering document, and, that this experience informed my judgement that these representations in MBH98 amounted to warranties.
We then provided a detailed discussion of these representations, including exact quotations of the original representations and what we had determined by attempting to verify these claims. We asserted that "replication" of MBH98 required not just approximate representation of a squiggle, but replication of claimed skill and robustness. MBH claims of statistical skill and robustness to the presence/absence of all dendroclimatic indicators stand in stark contrast to actual results. The contrast is not very subtle. We didn’t have the Ammann and Wahl results at the time – they were released almost immediately after the NAS panel session ended. However, we do now and we plan to send them in to the panel, showing that even Ammann and Wahl have (however unwillingly) confirmed our claims of MBH statistical failure. We showed through the CENSORED files that the lack of robustness to bristlecones was known at the time.
We skipped over replication issues in our oral presentation, but there is lots of information in our written material.
We added in some slides from my AGU presentation to show a common pattern over all multiproxy studies: failed Durbin-Watson statistic in the calibration period; with catastrophic reduction of verification r2 statistic in the verification period. I was asked about periods for these calculations — they were all done with common Mannian periods. One of the panelists asked what a Durbin-Watson statistic was.
We made a few comments about the other presenters, noting that both Hegerl and D’Arrigo had refused to provide data during the IPCC process. We proposed to the panel that they not rely on any studies where the data had not been archived (this would include Luterbacher). This led to some discussion afterwards in which Hegerl, in particular, argued that their paper had been submitted to Nature and was under embargo – as though that was a sufficient explanation of why could not provide supporting data (or even identify the 12 sites) to IPCC. My conclusion was the opposite – if they were unable to supply supporting data for IPCC review, then they should have withdrawn the paper from the IPCC process (or IPCC should have deleted references to it.)
We showed a couple of slides on the Divergence Problem — a graphic from Briffa showing declining ring widths and density in the second half of the 20th century and that wonderful cargo cult quote from Briffa. We also showed a nice tripartite slide showing Site Spaghetti — the difference between Briffa’s old Urals series, the update and the Yamal substitution.
What other questions can I remember? I don’t remember very many, as I was pretty focussed on matters at hand. One of the panelists noticed a difference between the BàÆà⻲ger and Cubasch figure in our PPT and what seemed to be a similar figure in B and C itself- that was because we used a figure from the B and C supplementary information for our PPT. Otto-Bliesner asked me what we would do if we were trying to make our own reconstruction. I said that we had no views on the matter at present. With the benefit of Hughes’ presentation, I think that I could reasonably say that I would recommend a “Schweingruber scheme” to a “Fritts scheme”, if it’s not too unfair to call Mannian data manipulation a “Fritts scheme”.
Afterwards, there was some discussion of investigators retaining privileged access to their data. North said that he thought that this was necessary simply because the investigator had obtained the data. I opined that exploration geologists go to just as remote locales as paleoclimate people and it would never occur to them that they “owned” their data. Turekian said that exploration geologists made much more money than academics; I contested that, saying that many exploration geologists live contract-to-contract and scuffle. I don’t get the impression that hard-rock exploration geologists, the ones that I know, make more money than academics. In addition, the U.S. government has already set standards limiting exclusive access to two years to cover this. The problem is that NSF doesn’t enforce it. Hence ridiculous situations like no archived information on the 1989 Dunde ice core until Thompson grudgingly archived the plot points of a Climatic Change figure in 2004 (in response to my complaint) – still not an adequate archive.
There must be some other questions that are slipping my mind at present; I’ll add them in as I or Ross (or Ned or others) remember.
How did we do on balance? I’m sure that there were lots of aspects to the presentation that could be improved. This was only my second presentation to an academic audience (the other being at AGU last December) — so I’m not tremendously polished at this. My main concern was that some one on the panel would ask a question that undermined what we were saying. Nothing like that. (In fairness, the panel is pretty new to the game and maybe they will have more probing questions after a little more time on the file.) I’m prone to go into what Ross views as excessive detail; on the other hand, I think that it’s important to convey to the panel that we have control over all the details and that this is one of our biggest strengths. Anyway no one remotely challenged anything that we said.
One remaining point about von Storch that I didn’t mention before. In addition to his vivid criticisms of Hockey Team matters, he showed two charts with MBH confidence intervals on them and said that he could not replicate them and thought that they were wrong. I mention this because we also discussed confidence intervals and it will be interesting to observe how the panel dealt with this issue raised by both of us, when Mann’s turn came. The entire topic of confidence intervals is extremely important.
There was a pleasant cocktail party after the presentations and I met a number of panellists and several presenters. (Mann and Hughes did not attend, as I mentioned before.)
So what was the score after the first day of play? None of the presenters would endorse a claim that climate of 1000 years ago could be reconstructed within half a degree. Yet the error bars in the famous MBH99 hockey stick graphic used in IPCC TAR were (slightly) less than half a degree.
Alley and Schrag back-pedalled away from millennial reconstructions, with Alley making some quite extraordinary comments that the academic community could do better if it was a “priority”. (Would I ever be irritated if I were a policy-maker funding these guys.)
D’Arrigo explained that you needed to cherry pick to make cherry pie. The “Divergence Problem” reared its ugly head; D’Arrigo said that Briffa had the answers, but we showed that Briffa’s answer was simply cargo cult science.
Hegerl talked about confidence intervals from the floor to the ceiling for low-correlation reconstructions.
In addition to dumping on the HS, Von Storch dumped all over non-replicability of multiproxy studies. All this was before we even went on.
We made severe criticisms of MBH (and other studies) and no one on the panel challenged these criticisms. I’ve posted up on Hughes already and I don’t think that he said anything that would have re-assured the panel.
So by the time that Mann started his presentation at mid-morning Friday, objectively, I would say that Sir Humphrey should have been pretty concerned about how things were going — Statement of Task or no Statement of Task. Sir Humphrey needed a knock-out blow from Mann. Did he deliver? More on this tomorrow.
*The Latin term “Sui generis ” means, in a legal context: “unique.”
Climate Audit 
44 Comments
The link to the power point file is not working (at least right now).
Steve: Sorry about that. Fixed.
The Figure isn’t showing up for me.
Steve: I don’t know why the figure isnt coming up. I’ve tried to fix it. Maybe I’ll be able to figure it out tomorrow.
Steve:
Without sounding like a round of asskiss rodeo (see Messrs. Carolla and Drew), I’d like to add that your presentation was excellent.
It succinctly summarized both key issues and the history of scholarship addressing them.
I understand that many have “moved on” from the paleoclimatological debate to modeling, but the IPCC’s rush to accept Mann’s reconstructions, which have been published in textbooks worldwide, is a monstrous eye-opener regarding its judgment and care.
Looking back, regardless of where one now stands on AGW, it is simply beyond incredible that Kyoto was shoved so hard and fast down governments’ throats with these reconstructive graphs so prevalent in every policy and media debate. That is a hundreds of billions — if not trillions — of dollar decision.
The lack of care and dilligence in the entire reconstruction process is simply staggering for policy issues this large. Regardless of how many “me too” papers are subsequently slapped thereon.
In addition to the somewhat cowboyesque nature with which academic “consensus” seemed to be reached on something so central to a monstrous policy debate, the combativeness and ommissions from the hockey team are also somewhat of an eye opener for someone outside the field to view. Your publication of correspondence, as well as just watching the papers come down over the last 7 years, has been truly illuminating.
I believe many of the more reasonable people on the pro-AGW side of the debate would also agree with the above (while maintaining their stance to combat AGW). Far more of both rigor and openness will be required before any serious policy decisions should come even close to being made.
Steve: I’ve been out of this for a while. For completeness, can you show me where the IPCC TAR says that “climate of 1000 years ago could be reconstructed within half a degree”. Thanks.
If you look at the error bars of MBH99, they are a little bit less than 0.5 deg C. These error bars are illustrated in IPCC TAR.
PPT fixed.
#4 Figure 2.20 in the TAR and Figure 5 in the TAR Technical Summary show the Mann reconstruction, given with “two standard error limits.” On the graph that error is about +/- 0.5 degree in the Medieval period. That means they’re reporting the 95% confidence interval for the error in the reconstruction for 1000 years ago as approximately +/- 0.5 degree.
#4,5,6 linked here and here. (htm and pdf, respectively)
#4: The Summary for Policymakers contains the following text:
Click to access spm22-01.pdf
Regarding the assertion that the IPCC claims climate could be reconstructed within half a degree:
Showing, or indeed featuring, one reconstruction that estimated its error bars (95%) at around +/- half a degree is NOT the same thing as “claiming that climate could be reconstructed within half a degree.” Other reconstructions exist, and even the TAR itself notes on the same page that some of these others lie outside the MBH uncertainties. In other words, the TAR acknowledges that the MBH reconstruction is not the sum totality of reconstructed climate wisdom. Merely an estimate, with uncertainties that are themselves estimates.
The take home message on reading this portion of the TAR is that (i) there is a 5% likelihood that the temperatures lay outside the 1 degree range of the MBH error bars and (ii) there is a fair chance that other reconstructions will not totally agree either. It is a straw man argument to say that the TAR “claims” half a degree. The TAR SPM in fact only rates it “likely” (66-90% chance) that the late twentieth century warmth was exceptional in the millennium. This is not certainty, and if you can confuse a 66-90% chance with a 100% certainty then you would be well advised to stay away from the casino.
Steve et al: “the CENSORED files”?
I get the feeling this is an in-joke or in-group sort of reference; in any case, I follow this blog fairly well and I don’t get it. Hint?
Steve (#5): Yes, I thought as much. So, here is how your “reasoning” goes:
1. “A” reviews a field of science.
2. One paper in that field is by “B”.
3. A figure from B reproduced in A’s report shows an estimate of the “two standard error limits” made by B.
4. Therefore, A has “claimed” that “climate of 1000 years ago could be reconstructed within” the “two standard error limits” indicated in B’s figure.
So the IPCC has “claimed” that EVERY result presented in the IPCC TAR is true?
In fact, if you read the “Summary for Policymakers”, you will find that statements relating to MBH 1999 are accorded the qualification “likely” or “66-90% chance of being true”.
It’s just more spin, isn’t it? If you were honest, you would remove the statement: “Yet this was the claim made by IPCC TAR”.
The half-degree question was Cuffey’s and coincided with the error bars of the most prominent graphic of IPCC TAR. I agree that IPCC onbly assigned the term “likely” to this. But all of the NAS panel presenters were familiar with intimiately familiar with IPCC TAR use of the hockey stick graph and were at NAS as expert witnesses and none of them made this defence.
In fact, I don’t see that this defence stands up anyway because of the prior misrepresentations of the statistical “skill” of MBH. In fact, the MBH98 reconstruction fails the tests of statistical significance that it was said to have passed, in particular, the verification r2 test. Because it failed statistical verification, it was actually impossible to assign any confidence intervals to this reconstruction (or for that matter, any of the other reconstructions, but that’s a different story.) The semantics of “likely” or “very likely” have nothing to do with it. IPCC was in no position to make any claims whatever about past climate based on these reconstructions.
The CENSORED files at Mann’s ftp site.
One of Steves blog threads about the CENSORED files here.
#11. I try to be precise rather than spin. I’m not trying to over-sell this point as nothing much turns on it. I have no objection to editing the above text so as not to appear to be over-reaching and have done so.
I don’t know why both of you are so insistent on putting little jibes in your posts about casinos and "if you were honest" – nothing is added by such ragging. I’m quite prepared to edit things if I’ve missed something without any need to resort to unpleasant hectoring.
Steve (#14): Thank you Steve — it is good to work with you in improving climateaudit.
However, I don’t think making a considered response to an outrageous statement (and one that has now been retracted) is “ragging”.
And my response to your modified statement (“yet the error bars in the famous MBH99 hockey stick graphic used in IPCC TAR were (slightly) less than half a degree”) is — so what? Is this the first time experts disagree on estimated confidence limits?
Another storm in a teacup …..
Re: # 15
John, well the NAS panel asked every presenter whether or not climate could be determined to within 0.5C, so they obviously place more emphasis on it than you do.
In any event, those questions are the genesis of all this discussion about the number, so you can hardly point the finger at Steve and others for discussing it.
BTW, you’re accusing Steve of engaging in “just more spin”. To me, that sounds like “ragging”.
http://dictionary.reference.com/search?q=ragging
#9,11 Page 29 of the Technical Summary says this:
“[T]he 20th century appears to have been unprecedented during the millennium, and it cannot simply be considered as a recovery from the “Little Ice Age” of the 15th to 19th centuries. These analyses [i.e., the climate reconstructions] are complemented by sensitivity analysis of the spatial representativeness of available palaeoclimatic data, indicating that the warmth of the recent decade is outside the 95% confidence interval of temperature uncertainty, even during the warmest periods of the last millennium.”
So, what does that mean? 95% of a 66%-90% chance? Hardly. The IPCC didn’t qualify that statement. It was made right next to Mann’s prominently-displayed reconstruction, Figure 5, which featured a nice horizontal line directing the eye to notice that the year 1998 was outside the +/-0.5 degree error limit of the Medieval temperature range.
In fact the whole paragraph on pp 28-29 rings with a certainty that gainsays the tentative apologetics surrounding the word “likely.” A political cynic would view the implicit (but obvious, and obviously polemical) self-contradiction as a case of clever plausible deniability. Caution is expressed in a footnote, but the conclusions transmit an unflagging certainty. If anyone protests the certainty, the cautions can be trotted out as evidence of a scientifically approved modesty (apres Tas). They’ve gotcha coming and going. Great for a political hack, wrong for science.
John H, if you were to argue fairly, you’d not hang Steve M’s personal honesty on a single pin (“If you were honest, you would …”). Unqualifiedly judgmental moralizing like that is hardly, well, ethical.
And by the evidence of TAR SPM pp 28-29, I’d say that Steve M is well inbounds in his statement describing IPCC’s half degree claim.
BradH (#16): Thank you for indicating that I am indeed guilty of “ragging”, and for also pointing me to the dictionary definition, one of which is:
“Sports. In ice hockey, to maintain possession of (the puck) by outmaneuvering opposing players, especially so as to kill a penalty.”
….. and, yes, I did outmaneuver one certain “hockey player”.
As I understand it, the Divergence Problem is where an (recent) increase in instrumental temperature is not indicated by the tree-ring proxies. Is this really critical?
The claimed purpose of the hockey stick is to show that recent decades are the warmest in the last millennium or so. Thus, if the proxies showed a warming that was not in the instrumental record, then this clearly would be extremely critical. The reverse, however, does not seem to logically negate the hockey stick claim (though it is interesting and disquieting).
Sara, I think the issue with the divergence problem is whether tree rings are adequate proxies for temperature. Specifically, if they are unresponsive to 20th century warming, how can we be confident that they could reflect warm periods in the past?
Steve, the “handout” you provided to the NAS panel is outstanding, easily the clearest exposition of your work to date. You should link to it in the “Road Map” sticky.
Wow John, you are getting clever. Since the only grounds left to you to defend MBH is nit-picking, pick away, it shows just how professional you are.
How would you like to “honestly” now acknowledge Steve’s point that MBH98 (and 99) fail standard statistical tests and should if honestly treated, never have claimed either robustness or statistical significance. Can you take that step, can you even contemplate acknowledging that the study you have steadfastly defended over a number of years really is junk science ? Can you be that honest yourself ?
Re:#19
As James Lane says, the divergence is a problem because the hockey stick reconstructions do NOT show major warmings in the past (the relative “straightness” of the shaft). Since the tree rings do not show the warming of recent decades, perhaps the past reconstructions based on tree rings are similarly wrong and those times did in fact have periods with temperatures as high or higher than those of recent decades.
Re#19
“Thus, if the proxies showed a warming that was not in the instrumental record, then this clearly would be extremely critical.”
The instrumental record is flawed.
Simple experiments show that single buildings or paved areas raise temperature to the same or greater extent as the claimed GW.
Since most towns annd cities have expanded over over the last 100 years and most stations are near to built up areas it is no wonder the surface temperature shows an increase in the last 100 yrs.
They say that Sea Surface Temperatures confirm 100 years of warming they don’t according to Brian Forbes in the comments to “Happy Birthday Charles Darwin ” which are available at:
There is evidence that polar ice extent in the early 1900s was similar to,or less than that of today at:
http://www.warwickhughes.com/cool/cool16.htm
Re:#18
John, even if you want to play cute by choosing that particular definition of “ragging”, you might recall that Steve said that “nothing is gained by such ragging”.
While I don’t confess any great knowledge of ice hockey, it’s my understanding that nothing IS gained by ragging in hockey…apart from buying/wasting time, particularly by an under-manned team. You certainly don’t score goals by “ragging”.
Nor did you.
#25. enough ragging about ragging. #18. For the purposes, of this post, I do not agree that IPCC had clean hands in their use of HS error bars; however, it was irrelevant to the purpose of the post to argue this different topic, which I will return to on a later occasion. I made a slight edit to make a narrower claim which could not be argued. I will in the near future return to the issue of IPCC’s use of error bars, so I would request that discussion of this topic be reserved until then.
Re #11. If ‘it’s just more spin’, it’s worth while remembering when and where all the spin began. On 20 November 2000, Dr. Robert Watson, Chair of the IPCC, formally reporting to the Conference of the Parties to the United Nations Framework Convention on Climate Change in that capacity, said that:
‘It is undisputed that the two last decades has been the warmest this century, indeed the warmest for the last 1000 years.’
No ifs or buts. Nothing about a 66 to 90% likelihood. Just a flat statement that it was UNDISPUTED that the last two decades of the twentieth century were the warmest for 1000 years.
Ian Castles
Ed Snack (#22): You say:
"Can you take that step, can you even contemplate acknowledging that the study you have steadfastly defended over a number of years really is junk science ?"
I’d really like an example of where I have once "steadfastly defended" MBH 1998 or MBH 1999 — I may have commented on misrepresentations (by Steve and others), but I have never given a "steadfast defence" of MBH. As I have said elsewhere: "it isn’t my field and I am happy to leave the proponents on both sides to argue their cases themselves" (http://www.climateaudit.org/?p=127, #22).
This is just another example of what I noted in another posting, when I said:
"One of the particularly distasteful things about climateaudit is the willingness for posters to pretend A has said X when A quite clearly said Y."
Steve: to others, please don’t bother responding to John’s ragging in the latter part of this post. Personally I favor accurate quotations; I try to use exact words as much as possible. I think that my record and practices in this respect are much superior to those of the other side, who never use exact quotations. If my characterization is occasionally imprecise or incorrect, I try to correct it as quickly as possible. John, I know that you have your pet peeves and like to pick fights. I do not agree that your peeves are correct, but I do not wish them to intrude on each thread in which you participate, and I would appreciate it if you would exercise a little self-control in this respect.
Steve, I agree that using exact quotes is far superior to trying to paraphrase what a person said. Of course even quotes can be taken out of context, but at least if the quote and source is given the originator can appeal to the larger context and keep any debate at a reasonably high level.
Probably a good rule of thumb for anyone is that if you find yourself having written a post and therein alluded to something someone said then if you aren’t willing to stop, and if necessary, copy your reply or pull up a new copy of your browser and go looking for the exact quote to replace your paraphrase, you probably shouldn’t post the message anyway.
Alternatively, you can rephrase your post to reflect active listening and ask the poster if your statement accurately reflects his/her position.
Forcing yourself to go through such a process will greatly increase the quality of what you post.
The Hockey stick graph at the bottom of the Summary for Policy makers contains some interesting fine print. I don’t think this point has gotten much attention. It is written in confusing language which appears to say that fifty year averages are used up to 1850 and ten year averages are used after that.
The title of the graph is “Variations of the Earth’s surface temperature 1000 to 2100”
Nowhere does it caution the policy maker that the change in averages makes the modern climate appear more volatile than it would if the graph were presented in a better way.
I don’t expect most policy makers would have noticed the problem. I wonder if this was brought to the attention of the NAS panel. Perhaps there’s just so much wrong with what’s happened that this has gone overlooked?
Summary for Policy makers:
Click to access spm.pdf
In promotion of securities, you are responsible for everything. You can’t justify excessively promotional information in a green sheet on the basis that it was accurately disclosed in the fine print of the prospecturs.
But I do not concede that even the caveat “likely” gets IPCC WG1 off the hook. I’ll come back to this another occasion – I’m merely noting that I do not concede it for now.
Re #32,
Consider that there are people who seem to prefer to distract from the most pertinent information in the thread. From such a point of view, any distraction will suffice.
Since many people here are alien to the scientific litterature on the topics they discuss, i would like to draw the attention to a paper published by Cook et al. in QSR 2004, I am sure it has been audited here before, but the audit seems to have failed to notice the fact that the paper speeks directly to the “divergency” issue. First by showing that the diergency is an issue not for the complete set of time series of Esper et al, but only for the northern ones, as also Briffa said in 1998, then showing that during medieval times this difference or divergency between mid and high latitude series does not appear. Bottom line – no evidence of MWP divergency.
Bart,
Does the Cook paper take into consideration that only some of the tree-ring proxy series actually have any real affect on the hockey-stick nature of multiproxy studies? IOW, if trees which don’t affect the reconstructions don’t show divergency, then perhaps that might explain why you get problems when you use those which do.
Anyway the most likely cause of divergency is aerial fertilization or some other human cause and who would have expected that in medieval times? I don’t see that this article is relevant from what you say.
#33 Bart, if one doesn’t know why tree rings diverge in the present, one doesn’t know why they did not in Medieval times. The result is that with uncontrolled variables affecting the data throughout, the use of tree rings to model temperature is rendered entirely unreliable. This is basic experimental science. You must be able to extract the variable of interest from your data, with no hidden and confounding variables. Blinding oneself to accidental but accomodating correspondences is a sure way to disaster.
re 35. To repeat, only the high lat. series of Cook et al. show divergency in last 50 years, hence a number do not, and show a good fit to temperature. The divergence is between mid and high lats. In MWP this divergence was not there. Good paper to read for insight, if that is what one is after.
#36 – Bart you miss the point. If one doesn’t know why tree rings happen to diverge from temperature here, one also does not know why they happen to trend with temperature there. The underlying mechanisms determining tree ring width remain undetermined. One cannot choose out data that happen to trend with temperature, when it is not known whether it is temperature that is inducing the trend. You’re assuming causality where one can only defend association.
Re #37: To pound your point Pat, doesn’t that reasoning also apply to the relationship between rising CO2 levels and (supposedly) rising temperatures (supposedly until the temperature series can be disclosed, checked and confirmed) until a causal relationship is proven?
#38 Indeed, your point is right Bruce, and I’ve made it elsewhere on Steve’s blog several times. The critique is the same. The GCMs are not adequate to support a claim that rising CO2 has caused the apparent 0.6 C rise in global mean temperature. In science, data only take their meaning within the context of an unambiguous and falsifiable theory. The GCMs do not meet that standard and, if anything, the theoretical understanding of tree ring width seems poorer than that of climate.
To be more specific, atmospheric CO2 has a positive thermal effect, but the energy fluxes and feedbacks of Earth climate are too poorly constrained to know whether the effect of, e.g., doubling CO2 from the 1900 value, will produce a discernable effect on atmospheric temperature.
In Bart’s example, the logic most starkly is this: ‘Assume these tree rings reflect temperature. Therefore, these tree rings reflect temperature.’ Not only that, but the assumption that certain trees are following current temperature is then projected back into the centennial past to include previous temperatures. It’s circularity redux.
There’s an article about the Hockey Stick debate in this weeks New Scientist: “Grudge Match: The crucial evidence for global warming is fatally flawed – or so we are told”
The article is written by Fred Pearce and it ends with the usual twist (i.e. it means it’s going to get worst than even we thought:-) ) , with a quote from Briffa – ” ‘Greater past climate variations imply greater future climate change,’ he says. From this perspective, it would be most worrying if all the hockey sticks really are wrong.”
I’m not sure whether the last bit of the quote is from Briffa or Pearce as the bit in quotes ends with a comma?
Re #40
Presumably that will be the assertion that high variability in the past can only mean dangerously high sensitivity to CO2 change, since we know that solar variability for the past 1000 years has been negligible.
I’ve commented before that the past influence of solar variability seems to me to have been discounted in the last ten years, I do sometimes wonder whether this has actually been due to the status of the Hockey Stick.
Rod, can you email me the article?
Steve – you should have an email from me!
RE: #33. Why the smear? You try to imply that there are no scientists or other technically trained people participating here? Why does the idea that scientists, technically trained people, as well as others who have an interest, are not in accordance with the orthodoxy? That is your real issues, isn’t it? Oh, we must be on the take from Exxon, that’s it / sarc. The fact is, from my perspective, most skeptics tend to be more traditional in our approach – strict following of the scientific method, respect for noise, awareness of the limitations of measurement systems and the even greater uncertainties inherent in the use of so called proxy data. As usual, those who politicize science to promote the Radical Green agenda conveniently ignore what we all supposedly learned as Freshmen!