The Loehle Reconstruction

19 11 2007
So this is my Sunday-night review, hopefully a more peaceful one than my Friday outburst on Climate Audit. I have re-read the paper and don’t have many more nice things to say about it… But hopefully i have weeded out the superfluous – including the “aggravated tone” . There might still be some irony left : apologies in advance.
I have refrained from reading CA comments that followed by friday-evening post (221), to stay on point. Comments to the answers to the comments to the questions will come in due time (i have a busy week coming up, and have unchained quite a firestorm that i cannot tackle tonight…).

Before we start, however, I have a few disclaimers to make :

  • I am conducting this review alone. This is unrequested work, i am only doing it for the defense of my own scientific conviction and to share it with other readers, some of which have little background on the subject. Needless to say, the form would be vastly different if this were a review carried out for a scientific journal. However, my angle on it is : does Loehle’s reconstruction, meet the basic criteria that i would apply to a review, were i asked to be a referee ? Anyone is free to disagree – and i am looking forward to insightful comments from statisticians.
  • Since the issue has started to appear on this CA thread, let me be perfectly clear. I am not here to defend previous work : the sole focus of this review is Loehle’s article. I am a newcormer to this game, having entered the wonderfully charged world of paleoclimate reconstructions less than a year ago. As such, i do not pretend to have inoxydizable expertise on all recontrusctions to date, much less on all of ClimateAudit’s blogposts. Hence, please do not ask me to justify so-and-so’s methods. Loehle comes as a challenger in this game, and i believe it is the job of the underdog to do at least as well as the Establishment he criticizes. I will accept no excuse of the type :”this had not be done in the usual reconstruction” if they are demonstratedly doable in the case of this simple method (cf error bars). McIntyre is well-founded when he says that much of my criticisms would apply to some previous work, none of which have i ever pretended to defend.
  • I am not emphatically not here on behalf of RealClimate, the IPCC, GaTech and certainly not here to defend Dr Mann. I am entitled to the independence of my views and refer to none but my own education, judgment, and bibliography. Dr Mann, on the other hand, is entitled to the defense of his own work, has done so with relentless (and arguably, successful) effort over the past 9 years, and is an equally independent scientist who can fend for himself. My own opinion on the MBH99 reconstruction ? I wouldn’t bet the family farm that “1998 was the warmest year in at least a millennium”, but i agree with the NAS panel when they find that , “with a high level of confidence […] Global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries”. Ditto that is it is plausible that “The Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium”.

    Mann’s publication record speaks for itself, he and collaborators like Scott Rutherford have undertaken very extensive re-workings of the MBH98/99 algorithm, albeit not necessarily gracefully – in CA’s eyes. I wholeheartedly agree that climate science is lagging behind other fields in terms of providing open access to data and methods, and Steve McIntyre’s efforts are much needed in improving these standards. Nonetheless, i find CA-dwellers a little antiquated in their constant re-hashing of MBH98 criticisms. They would be well inspired to direct them at his most recent work if they so wish, rather than beating horses dead in 1998 or 1999. While it is true that MBH98 is not the panacea of climate reconstructions, it would be reductionist to corner all of “Team” into one article and ignore almost a decade of subsequent work. Since CA readers get understandably upset when i lump them together with climate obscurantists, they should lend a sympathetic hear to the statement that not every climate scientist is guilty of pensée unique.


Review of Loehle (2007).

The article comes from Craig Loehle (a PhD in Mathematical Ecology with a rather freshly-discovered interest in climate research) , and published in the infamous “Energy & Environment“, a peer-reviewed journal that recently emerged as the number one printing device for climate obscurantism. Indeed, said ‘peers’ do not seem to know much about climate. Be that as it may : let’s go beyond appearances and give the paper an honest read : Loehle could be a revolutionary mind, whose deep mathematical insight will cure many of the ailments that have henceforth plagued the efforts of many a climate scientist – who, owing to CA, are allegedly ignorant in statistics.

We start by an extensive introduction that argues for the inability of tree-rings to record any temperature signal on the period of interest, and is decently informed. While it would be excessive to throw out just ANY tree-ring series (though they had issues with strip-bark trees, i don’t believe the NAS panel recommended the incineration of the entire dendroclimatological literature), the point is well taken : in light of the many factors that influence tree-ring growth over long periods, it is certainly a valid “What if ?” experiment to produce a reconstruction free of such data. Since the author acknowledges that it is not the first (Moberg [2005] and Viau et al [2006] have already done similar things) , we are eagerly awaiting what original statistical techniques will be presented here if the author is to arrive at a substantially different conclusion.

Eyebrows start rising when the only references given to support the existence of a “Medieval Warm Period” (MWP) are from the author himself (Loehle 2006), and Soon and Baliunas (2003), which has been thoroughly debunked by RealClimate colleagues (see Myth #2). For those not so versed in blog wars, The MWP is a favorite of global-warming denialists, because if you coax the data into showing a warm enough early millennium, you can negate all of the IPCC’s work : it’s super duper cool.
Unfortunately, there is ample evidence that the so-called Medieval Warm Period was far from global : see for instance the NAS report (North et al, 2006, chapter 11 and references therein). There is, however, great interest in understanding why it was warm in Europe or dry in the US South West and central America, and seemingly cool in the eastern tropical Pacific (cf Graham, 2006), so let’s read on.

METHODS : The section is startlingly short. 18 proxy timeseries are selected on the grounds that : a) they are available for 2000 years b) they are not tree-rings. A decent case is made that one should not worry too much about dating uncertainties. Fair enough. What next ? Data are smoothed, standardized, and… averaged. Period.

I had to read the article 3 times (re-downlading it just in case i had gotten a faulty version the first time) to convince myself that i wasn’t dreaming. All subsequent figures show the arithmetic mean of 17 or 18 series, as if they all recorded local temperature with the same accuracy, and were representative of the same geographical area.

Proxy temperature relationship

Since the article’s title mentions a “global temperature reconstruction”, one would expect two fundamental aspects to be discussed . 1) these are reliable temperature proxies ; 2) they are representative of a global average. In that light, i expected the merits of said proxies as paleothermometers to be at least brushed upon. There are only 18 of them (unlike most paleoproxy studies, which can compile >200 ), so it wouldn’t break the author’s back to at least READ the papers he is citing, dig up the error estimate, and put this all into a pretty table. It’s not so clear he does *read*, however, otherwise he wouldn’t have retrieved a “Borehole 18O temperature” from Dahl-Jensen et al. [1998], just a borehole temperature inversion.

This is a very different situation from usual multiproxy studies which use sophisticated methods to ensure that a proxy’s weight in the final result reflects its ability to record some variance in the temperature field (whether local or not). While there is merit in exploring a bare bones approach (arithmetic mean), it then becomes indispensable to demonstrate that each proxy is : a) a temperature proxy (not a salinity one…). b) a good one at that.

At first glance, a) is dubious for the Holmgren and Keigwin timeseries (that’s at first glance… i need to dig more), and b) can usually be assessed from the authors’ error analysis. If it is not, then the author should conduct his own, or drop the use of such proxy.
Once again, such care would not be required when a climate-field-reconstruction or “composite-plus-scale” approach is employed, as the proxy’s ability to record temperature is implicit in the calibration therein. Since the author effectively treats the proxies are perfect thermometers (which is conceptually acceptable as long as it is explicitly justified), the lack of this discussion is unforgivable, and in my book, constitutes grounds for rejection any day of the week.

Error propagation analysis

This part is usually immensely complicated in the case of non-linear estimators, but it should be a piece of cake here. Since the proxies are so concisely described (i agree that a map would have been nice – apparently it didn’t take S. McIntyre very long to make one), it comes as no surprise that the final result is utterly devoid of error bars.
Instead, the author chooses a jacknife analysis, which in my view only speaks to the relative importance of each proxy in the final results. Imagine all proxies had a standard error of 2.5 degrees with the actual temperature : this analysis would say nothing about the accuracy of the mean.

Let’s be more constructive than in my original CA post : there are several possible approaches. For instance, one could assemble a vector of proxy errors, and assume the temperature proxies are iid and Gaussian, which is quite reasonable. It would not take a PhD in mathematics to prove that the arithmetic mean is also a Gaussian random variable with a standard deviation that is the L2-norm of the sigma vector (divided by the number of series). This is rather simple-minded, but since the approach is deliberately simple, it would be consistent with this framework. There maybe more elaborate ways, as discussed by Hu McCullough here.

In any case, it is unacceptable to make the quantitative claim that the data ”would indeed seem to show the MWP to be warmer than the late 20th century” , “by about 0.3 degrees. This number is worthless without an error bar, or at least an insightful discussion of uncertainty.
Rejection again, sunday or friday.

Reconstruction skill.

Again, impressive concision ! Where are the CE, RE, and most importantly R-squared statistics that are so dear to ClimateAuditers when used by the Team ? How are we supposed to guess whether the reconstruction has any skill ? (skill, by the way, is a ubiquitous term in the numerical weather and climate forecasting literature. It is intuitive enough, but if statisticians need a more statistical term, i can try and dig one up over the next few days). In his original response, Loehle argues that these statistics are irrelevant because he does not have a model. This is false, as pointed out by bender, and myself. Despite claims of using a “simple mean”, the author’s approach is effectively a multivariate regression. Indeed, each of the proxies was calibrated against temperature using such regression methods, usually linear, but sometimes non-linear (Mg/Ca ratios depend exponentially on seawater temperature, for instance). So by doing even a simple average, the author is effectively using a statistical model, and is therefore not exempt from the verification exercise.

(incidentally, i regret that bender seems to believe i have been plagiarizing his ideas. I was responding to earlier comments when he posted his and did not see them until after i had submitted mine – an unfortunate consequence of the high traffic at CA… This convergence does, however, suggest we have more in common than what superficial disputes would suggest, so perhaps one day we’ll have real dialogue)

Minor comments :

– I could not find a reference for “simple mean” (p1053). It may be a novel contribution to the mathematical literature – which had heretofore used “arithmetic mean”. I only point this out since CA statisticians seem always eager to correct climatologists on their improper use of statistical terminology. While i am genuinely eager to be educated in statistics, i wish the same standards applied to everyone.

– I believe it is the first time i read ‘I believe’ in a scientific paper (it’s different in politics), and it is there 3 times in the discussion. Hmmmmm…

– R. Villabala does not appear to have any publications on the Medieval Warm Period. Ricardo Villalba, other other hand, does. (the error is present in the text and reference list). This reinforces the feeling that the basic homework really hasn’t been done.

In summary, this article is a poorly-described compilation of proxy data, with a conciseness in methodology that borders on farce. In the present form , it is unacceptable in any scientific journal that i am aware of. Though the approach is conceptually useful, it is not novel : the author himself acknowledges that Moberg (2005) and Viau (2006) have left out tree-rings from some parts of their reconstruction before. So what is new here ? It can only be the methodology. We have shown that its elliptic nature is naive at best, misleading at worse. Even with all the good will in the world, it is hard to grant the author the benefit of the doubt, given how loosely he handles his references and prose : this simply is not credible work. The author’s argument that his “strategy in writing this was to make it as short as possible to avoid complications during review” is distinctly unconvincing. Why not, then, bypass the whole ‘methods’ section, and simply give us a curve without any explanation ? Brevity is the soul of wit, yes – but when crucial information is missing, this “science” has an odd scent of disinformation.

I am glad to see that a healthy debate has now engaged on CA and that Steve McIntyre has undertaken a serious audit of this study (e.g. here and here). Already, some of my question regarding spatial sampling have been admirably addressed, and though it should have been the author’s job to do this before submission, the only thing that matters here is that the question be answered somehow.

I hope this debate will bring Craig Loehle to produce a scientifically-acceptable reconstruction – one that meets our basic field’s criteria for publication. He would otherwise condemn himself to sub-standard journals like Energy & Environment, ensuring that they are invisible to climate scientists – for good reason.

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29 responses

19 11 2007
epica

Julien
I posted this on CA and I thought I share this with your blog.
Cheers

Some remarks to one of the used series. The Mangini d18O Speleothem record (with a nice representation of the MWP).
I think this record has very serious problems and the “calibration” of the original authors hardly merit this name.
1) The calibration of this European (Austrian) high-altitude cave record is done using 3 points: Today, 1900, Little Ice Age. For the LIA the authors take an assumed mean European value of what the LIA is supposed to be averaged over the entire continent. This is no calibration in the usual sense of the word.
2) The 18O cabonate record is INVERSELY related to temperature. What does this mean? After subtracting the direct fractionation effects of calcite formation there is a negative relationship between the 18O of dropwater and Temperature. Warmer temperature, more fractionation ie more negative drop water. The drop water is of course mainly controlled by meteorological water and therefore this relations ship is the inverse of what you find everywhere in Europe or of what is used interpreting high latitude ice cores. It is simply an unphysical relationship. Mangini et al argue that infact the drop water is not at all controlled by the isotopic composition of the water falling in the catchment of the cave but is controlled by unknown and unmeasured soil processes. No verification, no explanation whatsoever.

19 11 2007
El Niño

thanks a lot. Epica ! This is the type of comment i most want to see, because you have actually read and scrutinized the paper – while i confessed i haven’t yet. I enjoy this pre-screening and will reserve my judgement on the Mangini record for after a careful reading.

19 11 2007
RichardT

I remember being impressed reading some of Loehle’s papers when I was a PhD student. His latest work is a disappointment. I was expecting a much more interesting mathematical treatment of the problem. Indeed we even have to draw our own map (which took 20 minutes), to see the geographical distribution of proxies. I would have recommended a major rewrite of the paper had I had it to review.

20 11 2007
Anonymous

Well Julien, this is much nicer, though you still can’t help heaping scorn on me. Moberg’s low-res series included 2 series uncalibrated to temperature and he then rescaled his low-res series to have a variance of 1. No explanation. This did not seem robust to me. Your description of doing error bars is very nice, and I am quite capable of programming monte carlo sampling, but how would you handle the huge variety of data interval, from annual to once per century, in the different series, with dating error usually unknown or unspecified by the original authors? There is also a novel element you have missed. In typical recons, the different series have deviations computed based on a given decade or several decade period. I believe this will create noise when there are dating errors and irregular sampling, so I normalized each series against its own long term mean. My purpose in doing the study was to get my foot in the door that other proxies produce a different result than tree rings, which everyone is hooked on. I have achieved my purpose and if you think I did a crappy job, please repeat the study in a proper manner. I don’t have my lifework tied up in this. Maybe we could collaborate on the remake?
Craig Loehle

20 11 2007
Anonymous

But, Dr. Loehle – with those admitted dating errors, how can one be sure that they represent the correct eras to make a comparison with the 20th century? There are significant dating errors with radiocarbon dating between ~1550 & 1950 A.D.; I cannot find the source, but I’m positive there are more ‘plateaus’ in radiocarbon dating over the last 2000 yrs. This is a significant limitation to the reconstruction that you have made.

Unless the dating was made with lead-210 or cesium, the last 400 yrs of your record could be fraught with errors.

Several of the proxies you use are better for longer time periods than the last 1000 yrs. This combined with the other flaws further supports Julien’s rejection from mainstream the mainstream lit. For some reason this is not taken seriously over at CA.

20 11 2007
Michael Strong

You are the most important fresh voice in climate blogging in a long, long time. Your take on the virtues and vices of both RC and CA strikes me as apt, you respond fairly and well in the face of often ill-mannered attacks at CA, and you address legitimate questions brought up there squarely without prevarication or evasion. As someone who really wants to know the answers to many of the questions posed at CA, I’m very grateful to have an open, honest, playful, good humored, intelligent, and qualified advocate of the IPCC position engaged in the public debate both there and here. Please keep it up!

20 11 2007
Anonymous

Let the force be with you.
=========================

20 11 2007
El Niño

michael strong : thank you. really. I have been spending a lot of time on this over the past 4 days, and it feels amazing to hear that i wasn’t “pissing in a cello” as we say in French…

Craig Loehle

“Moberg’s low-res series included 2 series uncalibrated to temperature and he then rescaled his low-res series to have a variance of 1. No explanation. This did not seem robust to me. “

i don’t think it is either, but i don’t see what it has to do with the present argument.

“Your description of doing error bars is very nice, and I am quite capable of programming monte carlo sampling, but how would you handle the huge variety of data interval, from annual to once per century, in the different series, with dating error usually unknown or unspecified by the original authors? “

Isn’t that a question you might have wanted to consider before publication ? Welcome to Paleo-world : it’s a rough one. Many paleoclimatologists lack a good training in statistics – much less advanced mathematics – so there’s an avenue for people like you to bring real progress to the discipline. But that requires upping up the ante, not lowering the standards.

“There is also a novel element you have missed. In typical recons, the different series have deviations computed based on a given decade or several decade period. I believe this will create noise when there are dating errors and irregular sampling, so I normalized each series against its own long term mean.”

The reason for estimating the mean over the instrumental period (1856-1999, or some subinterval thereof) is that most studies had bothered to compare their results to the instrumental record.

“I don’t have my lifework tied up in this. Maybe we could collaborate on the remake?”

I appreciate the offer. I need to read some of your other work to decide if your work ethics are compatible with mine. Perhaps we can meet ?

21 11 2007
Chris Christner

Julien wrote:

[But] i agree with the NAS panel when they find that , “with a high level of confidence […] Global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries”

I’m not sure what you think that statement proves, the Little Ice Age ended 400 years ago, so it’s not a tough call to predict that temperatures would climb afterwards.

Ditto that is it is plausible that “The Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium”.

It’s just as plausible that the preceding century was not unusually warm when compared to the Medieval Warm Period and other warm cycles over the millennium. Especially given the equivocal nature of Mann’s data.

I am not here to defend previous work : the sole focus of this review is Loehle’s article. I am a newcormer to this game, having entered the wonderfully charged world of paleoclimate reconstructions less than a year ago.

Hello, you won’t comment on errors in Mann’s work because you’re inexperienced, yet you feel competent to criticize Loehle’s paper? For committing many of the same sins as Mann and others in his “social network?!”

How can you not have formed an opinion on one of the biggest controversies in the debate over AGW? Are Steve McIntyre, Wegman and the NAS correct that Mann’s work was seriously flawed?

You’re fond of calling AGW skeptics “deniers” and “obscurantists”, but remember that it took Steve McIntyre, not peer review or other climate scientists to discover the errors in MBH’s work. Have you seen the AGW community give thanks for his contributions? Of course not, his results have been greeted with contemptuous scorn, so take a hard look in the mirror and ask who the real deniers are.

21 11 2007
TCO

It’s amazing how the same people who claim to being oppressed by biased reviewers also write papers that are so sloppy on even basic points (citations, etc.) I don’t buy it from these cats. They need to be able to do the basics. And if they did…and if they were buttoned up in all aspects of their papers (not just clerical, but logical), they could easily rock in and publish controversial papers. Landsea seems to be able to get into top journals. But he’s a real scientist. Not an internet nitanoid that needs a figurative forearm shiver.

21 11 2007
TCO

Craig: You should want to do it right! You should care! You should want to learn…to do science…to explore nature…and uncover features of the world and even of mathematics. and you should know and care when you do good work. You should be able to sense it. To taste it. I know that whatever I do…wether a science paper or a corporate business analysis…I can TELL when it’s good work. And I can tell when it’s lacking. And I do all kinds of lacking work. But I want to do GOOD work. And I don’t want to put stuff into the permanent literature (granted EE is not real literature…haha) that is not worthy of posterity.

21 11 2007
Anonymous

TCO, if I didn’t know better (well, actually I don’t), I would think Loehle might be quite content with people calling his current publication substandard so long as the mass barrage produces a stronger paper. He is now, in essence, setting the stage for what might be the first “open-source” paper as every single flaw is being criticized and examined… what will remain after corrections and caveats will be a nearly-perfect paper to be re-published.

21 11 2007
Francois O

Julien,

Funny how easy it is to give a bad review to a paper that comes from outside your little circle of friends and colleagues. As a matter of experience, I would say more than 90% of the papers I have ever reviewed were “substandard”. Yet, I did let many of them pass anyway. But one thing I realized, when I left the beautiful world of academia, was that I now had the freedom to really criticize the papers I reviewed. I had no friends to protect (and eventually everyone in your field is a friend), and I didn’t have to watch my own back.

Surely climate science is exceptional as a scientific field in that all the papers are outstanding. Not to mention your own work ethics, which we all admire. In my own field, there was, and there still is, a lot of junk being published, and despite my own work ethics (which is of course just as admirable as yours), sometimes I really didn’t have the time to make a good review.

Now I will hypothesize that your personal bias in this case is obvious, for example knowing the political positions that you have expressed here on your blog, and that it obscures and distorts your judgment. If I were an Editor, I would try to chose a reviewer who has not overtly expressed disdain and contempt towards others on the basis of their apparent political position, or simply their scientific opinion. In any case, I would be very suspicious of insinuated ad-homs about work ethics and the like. A little humility would also help…

In other words, if I were an Editor of a climatology journal, I would find it very, very hard to find a suitable reviewer these days.

21 11 2007
El Niño

Julien wrote:
Chris Christner said

It’s just as plausible that the preceding century was not unusually warm when compared to the Medieval Warm Period and other warm cycles over the millennium. Especially given the equivocal nature of Mann’s data.

Fair enough. That’s why i am in this game : so that “plausible” gets turned to “likely” or ‘unlikely’ (unfortunately we may never be able to be more accurate than that).

Hello, you won’t comment on errors in Mann’s work because you’re inexperienced, yet you feel competent to criticize Loehle’s paper? For committing many of the same sins as Mann and others in his “social network?!

I believe the sins are very different. Mann et al are not exempt from logical criticisms – no one is. But clearly Loehle did not do his basic homework on that one, and i’m giving him as tough a time as i would with any paper that comes my way at this day in age (not when i was in college, in 1998). I do so particularly because i know people like you would be prompt to brandish this work as a ‘definite proof against man-made global warming’.

You can easily understand that i am not going to undertake a comprehensive audit of the review process of the past 10 years – unless you want to pay me for that. Do you have petro-dollars to share ? 😉

Have you seen the AGW community give thanks for [Steve McIntyre’s] contributions? Of course not, his results have been greeted with contemptuous scorn, so take a hard look in the mirror and ask who the real deniers are.

I agree that the community needs to be taking the CA watchdogs more seriously, because they do very interesting work. However, the scorn stems in large part for the aggressive , inappropriate, and disrespectful tone they continually employ.
They are only getting a run for their money. As pointed out earlier, Landsea knows how to navigate these crowds and successfully gets his views heard in peer-reviewed journals. There are enough academics in CA that they could get their act together if they chose to play by the rules. Since they prefer intimidation tactics and punches below the belt,
they can’t expect to be treated much better.

When i treated them in a similarly offensive manner as they treat the very scientists they should be talking to (Mannm, Hansen, etc), you can see for yourself how uproarious they were. Lesson ?

Perhaps we should all cool off and engage in a real dialogue.

21 11 2007
El Niño

Francois O said :

I would say more than 90% of the papers I have ever reviewed were “substandard”. Yet, I did let many of them pass anyway.

I imagine we should all admire your work ethics, then ?

But one thing I realized, when I left the beautiful world of academia, was that I now had the freedom to really criticize the papers I reviewed. I had no friends to protect (and eventually everyone in your field is a friend), and I didn’t have to watch my own back.

Great : so the solution to unbiased reviewing is the abolition of academia ? I would think a combination of double-blind reviews and open-source reviewing à la “Climate of the Past discussions” would be a better start. Of course, every journal has an editor ; do you want to cut that head as well ?

Now I will hypothesize that your personal bias in this case is obvious, for example knowing the political positions that you have expressed here on your blog, and that it obscures and distorts your judgment.

You are entitled to any hypothesis. I personally think that transparency is a good thing. I wish i knew your motives and those of every climate skeptic. Their views are all too often “obscured and distorted” by a murky past in the mining, oil and energy industry.
At least i’m clear about mine.

Do they obscure my reasoning ? If they were, we wouldn’t be having this open discussion.

In my own experience (biology, earth sciences, physics), 80% or 90% of academia (Europe or US) is liberal. Does it mean non-academic conservatives with a solid science background should review their work ? You’d be hard-pressed to find some objective ones in there !!!

And FYI, some intelligent conservatives do believe in Anthropogenic Global Warming. Kerry Emanuel (MIT) is a prime example.

if I were an Editor of a climatology journal, I would find it very, very hard to find a suitable reviewer these days.

While the review was utterly unsolicited, the best proof of its relevance is the vigor of the debate now animating the ClimateAudit pages (for which, of course, i am only partially responsible).

So while your own political bias would lead you to choose different reviewers, i must have had some good points. Isn’t that what matters ?

21 11 2007
El Niño

Oh, and TCO : i could not agree more. On both accounts.

21 11 2007
Francois O

Julien,

See, you’re quick to label me a climate skeptic (you don’t know my opinion on the subject), and allude to a “murky past in the mining, oil and energy industry”. Yet, you don’t know ANYTHING about me!

You attribute political motives to my post, instead of taking it as what it is: a criticism of the peer review system in academia, and of the distortion it leads to when a scientific issue has political echoes in the society. In any other context, any other scientist would have acknowledged a high degree of truth in what I said, if not in public, certainly in private. Come on, I’ve been there long enough!

You don’t hesitate to make an open review of Loehle, but it’s so hard to have you say anything against Mann, because he’s powerful in your field, and, gosh! you might even write a paper with him, and have some of his reputation spill over onto you. What a boon for your young carreer! Of course you’ll go easy on him. You can say anything you want about your work ethics, and how you are interested in truth above all, in the end you’re really just an ambitious young scientist who wants to fit in.

See, I can attribute motives too.

22 11 2007
TCmutherfuckjingO

If he wants the thing, “murder boarded” to make it better fine. But he should do a GOOD, hard, best job first. And then get it boarded. Not do crap and expect others to fix it. That’s butt lasiness.

22 11 2007
Hippikos

Again as I said, El JEG is an opportunist with an obvious agenda under the disguise of a fresh approach of the discussion. Old wine in new bags. There’s too much status and money involved.

22 11 2007
paulm

Well, sadly I have to withdraw my comment on another thread about you presenting a balanced view of the debate. You reveal your true colors firstly with the ridiculous unprovoked remarks to Francois O about climate skeptics having a murky past in the oil industry (where does this come from – having you been reading the nonsense on exxonsecrets?). Secondly with the absurd remarks about the MWP being a ‘busted myth’ – the global MWP is well established from numerous papers. Just choose your country and google will find several, eg for china, http://www.springerlink.com/content/gh98230822m7g01l/
– the 13th C was the warmest time of the last 1000 yrs in China.

22 11 2007
TCO

It was a great peer review. I can see a good mind and can see when it has made an effort to do useful analysis. Mr. anonymous has likely never read the Feymnan books or Popper or other things like that.

23 11 2007
AK

I don’t know if an amateur question involving thermodynamics is on topic, but I guess I’ll find out. I don’t think I understand this field well enough to be certain my questions make sense, but here goes:

As I understand it, the “global average surface temperature” that is predicted to rise as a result of increased GHG’s is some sort of “thermodynamic average” (my term, in ignorance of the correct one). As I understand it, it might (for a first approximation) amount to a weighted average of surface temperatures with the weighting depending on things like e.g. cloud cover. Thus an area covered by IR opaque high clouds would have a weighting of zero (since for radiative purposes it wouldn’t matter what the surface temp was).

For purposes of climate change impact, I would guess some sort of agricultural measure, such as the integral over time of the daylight temp over 51 F. Other effects such as snowpack/icepack time/extent, groundwater, precipitation, etc. would be caused by local conditions, and thus could maybe be neglected?

As I understand it, all of these studies, from MBH98 forward, are trying to asses an average of temp over area, without weighting. Wouldn’t such an average be only a proxy itself, at best, of either of the measures I described above? Moreover, since even a thermometer temperature serves as only a proxy for its location’s contribution to the “thermodynamic average”, wouldn’t PC analysis be a better method than simple averaging in every case?

24 11 2007
Anonymous

With all due respect, the tone of this blog makes CA look like a meeting of church ladies. Sad really. Julien, you should at least ask those throwing ad hominems to grow up.
Bernie

24 11 2007
Geoff Sherington

Please stand back and take a broader view. An analogy. You are buying a new car. You ensure the engine works, the brakes, the transmission, the indicators … in short, each variable you examine appears to behave in an expected way. Then your wife says she does not like the colour, change from black to pink.

You throw your accumulated ideas together, leave paint colour out and conclude that you are about to buy a reasonably robust car.

The some guy appears and says “I’m an expert on auto emissions. You should get Instrument X hooked to your exhaust and measure if it is between A and B in values of this and that”. Another guy appears and says “I’m an expert on fuel consumption. You should instal a fuel meter and calibrate it for engine speeds under load on a dyno to see that the quoted figures are within the error bars”. Etc etc for more experts.

Now with Dr Loehle’s paper, the experts have already done their testing. The author has decided to leave out paint colour but the rest of the variables look in good shape to him. So he buys the car, displaying behaviour as normal as most people buying cars do every day.

Julien, why don’t you act like a normal car buyer instead of insisting that each transaction be studied to death, when it’s already stated as studied?

Not a perfect analogy, but if it looks like a car, sounds like a car, moves like a car, it might probably be a car.

25 11 2007
Tom C

Julien –

You wrote: Their views are all too often “obscured and distorted” by a murky past in the mining, oil and energy industry.

Can you please explain how a career in the mining industry taints an opinion regarding climate science?

26 11 2007
Sylvain.

Julien,

Maybe I missed it in the comment, but I don’t see anywhere any aknowledgement that the verification you requested were done and posted at CA. That these verification have shone this work to be robust.

Another interesting post is the combining of Loehle proxies with the tree rings used by Moberg. Which still shows the MWP to be warmer than today.

4 12 2007
EliRabett

“It’s just as plausible that the preceding century was not unusually warm when compared to the Medieval Warm Period and other warm cycles over the millennium. Especially given the equivocal nature of Mann’s data.”

These two simple statements raise two issues. First, the preceding century extended from 1901 – 2000, and the period we are most concerned with started about 1970 (or 1960 if you prefer), when greenhouse gas forcing started to kick in with a vengence. Second, the data no more belongs to Mann than the data cited by Loehle belongs to him, although you could make an argument that some of the dendro data belonged to Malcolm Hughes, which brings home the point that close examination of the data is required for any such study or better put, anyone doing serious reconstructions had better consult with or team up with experts on the several proxy measurements used.

2 10 2010
Inversion Table

I may have missed something, but it’s raining in Manchester. Not what I call strange weather.

4 11 2010
El Niño

Oye. This is the sort of comment that exemplifies zero knowledge of the problem. Climate is not weather, weather is not climate. Please don’t waste your time or ours writing such pearls of ignorance.

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