"Our greatest responsibility is to be good ancestors."

-Jonas Salk

Tuesday, October 26, 2010

Judith Curry: Born Beyond the Shark?

Judith Curry leaves only one possible argument for doubt that she has jumped the shark.

You'll need some context for this one:

Lets frame belief, disbelief, and doubt in the context of the Italian flag, that was introduced previously on the hurricane thread in which evidence for a hypothesis is represented as green, evidence against is represented as red, and the white area reflecting uncommitted belief that can be associated with uncertainty in evidence or unknowns.
Let's look at an example in the above-linked article:
Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.
This statement is often used as a litmus test for belief regarding global warming, i.e. you believe this statement (consensus) or you don’t (skeptic). Very likely denotes a probability of anthropogenic influence between 90 and 99% (lets pick 95%) and I interpret most to mean between 51 and 90% (lets pick 70%), with the remainder (30%) associated with natural variability. Hence, the Italian flag analysis could represent this in the following way:

5% assigned to uncommitted belief (white),
67% assigned to anthropogenic forcing (green),
28% assigned to natural variability (red).


my personal weights for the Italian flag are:

white 40%,
green 30%,
red 30%.

My assignment allows the anthropogenic influence to be as large as 70% and as small as 30%
As I have pointed out previously, that last sentence is immensely sloppy, conflating a hypothesis (a proposition that must be either true or false) with a weighting.

Now, I believe (and haven't really made the case) that weightings are much more useful in decision making under uncertainty than are hypotheses. But that's not the issue here. The issue is that Judith Curry, in unveiling her new intellectual tool with great fanfare and off-key notes of false modesty, conflates confidence in a hypothesis with weighting.

This leads to an unambiguous contradiction.

Suppose we eliminate the white altogether, and consider only the yes and the no. I must do this because I don't understand the "uncommitted belief" idea at all. But let;s simplify. Suppose I had a measurement with a very well-characterized uncertainty of the quantity. My belief that the majority of the warming is attributable to anthropogenic influence, say, is in line with IPCC:
  • p (f < 50%) : 0.02

  • p (f > 50%) : 0.98
Suppose, to be more specific, I believed (consistent with the above) as follows:
  • p (f < 50%) : 0.02

  • p (50 % <= f < 60%) : 0.02

  • p (60 % <= f < 70%) : 0.1

  • p (70 % <= f < 80%) : 0.72

  • p (80 % <= f < 90%) : 0.1

  • p (90 % <= f <= 100%) : 0.02
Then I would be quite confident that the percentage would be in the range 60% ... 90 %. But according to Curry's mangling "My assignment allows the anthropogenic influence to be as large as 98% and as small as 98%"

In other words, a well defined uncertainty yields an inconsistent certainty.


This leaves aside how to deal with the third value in a two valued logic.

In addressing that, consider that if one believes that the odds of a proposition A is P, then according to ordinary rules the odds of not-A is assigned a value of (1oo% - P).

The desire to separate out uncertainty from "uncommitted belief" requires a good deal more serious thought than Curry has put into it. (It turns out, in fact, that a lot of people have already thought about it. Read up on frequentists vs Bayesians.)

Curry's muddle effectively demonstrates the problems with using frequentist logic in situations where an estimate is required, rather than a hypothesis tested. Suppose, to return to a favorite example, one has in view a creature and wishes to estimate whether it is a duck.

The evidence may be sufficient for a frequentist to state with confidence that the probability of the present observations in the case of a duck is P, and the probability of the present observations in the case of a not-duck is Q. In most cases (lacking a huge observational set), the sum of P and Q will be less than 1. Indeed, once there is enough evidence to make P and Q add to 1, it would be very pathologically strange not to be able to state with certainty the duckiness of the creature in question; either P will be one and Q zero or the other way round. That's essentially at the core of frequentist analysis.

I think this gap is what Curry may be trying to grapple with in her white zone, given that in earth science we often lack enough data for a compelling frequentist analysis of important questions.

Neither P nor Q is an estimate of the probability that, given the observations, one sees a duck. This depends, it turns out, on the expected rarity of ducks! Assuming you are willing to quantify your prior belief in ducks, you can make a consistent argument for the propbability space being partitioned into duck and not-duck with none of that peculiar middle ground. Now, all of this should be very old hat to people who think about uncertainty. But it appears completely unfamiliar to Curry.

Yet she unveils her muddle with great fanfare, and in doing so, presents two inconsistent views of what it means right off the bat! In the light of all this, let's consider her most recent contribution to Currian probabilistics, which begins
Historical surface temperature observations over the 20th century show a clear signal of increasing surface temperatures. Italian flag: Green 70%, White 30%, Red 0%. (Note: nobody is claiming that the temperatures have NOT increased.)
OK, is it fair to say that "Note: nobody is claiming that the temperatures have NOT increased" means that nobody claims that "Historical surface temperature observations over the 20th century show a clear signal of increasing surface temperatures"? I mean, if nobody can claim the contrary, then the signal must be clear, right? So what does that white 30% represent? Does it represent 70% "it has warmed and I can deal with it" and 30% "it has warmed and I am in denial"? Or does it represent "although nobody claims it hasn't warmed, and there is a 0% chance that it hasn't warmed, there is still a 30% chance that it hasn't NOT warmed?"

Now consider the adulation that this muddle obtains from the peanut gallery. (Note, there's plenty more where this came from, but this is from another essay in the series. Thanks to bluegrue in comments.)
Oliver Manuel: Thank you, Dr. Curry, for having the courage to question the way uncertainty has been characterized in climate assessment reports.

Gordon Ford: Excellent post. When we were young we all feared “the monster under the bed”. Many have not learned to live with monster. In the real world (such as gold mining) one learns to live with the error in the estimate exceeding the estimate.

Paskvacs, eggcorning fiercely: I’m personally in favor of letting science guys work this out all by themselves. If they end up committing suicide, so be it. Say “La V”. But, as soon as you try to ‘reasonably’ let the legal system (with any new tweaks you want add) get their greedy little hands on anything like this fiasco, you –and not the scientists– are the one committing suicide.

hunter: Very interesting. I like this concept very much.

MaxL: Thank you, Dr. Curry, for introducing the discussion of uncertainty and questioning the way it has been used in climate science.

Baa Humbug: Would it be fair to say, if the true uncertainties in the climate models were enunciated clearly, Kyoto would not have happened and Copenhagen would have been a side show attended by a handfull of people?
and finally I will quote the entire comment of one Danley Wolfe along with Curry's response
Danley Wolfe: Judith,
this is a great post. I think the phrase “(t)here can also be epistemic uncertainty about how a physical, chemical or biological process works is extremely important. Scientists suffer from “completeness fallacy” meaning they need to carry through work to some meaningful level of completion (for reasons such as need to mark progress, need to publish, need for peer recognition, need to meet deadlines for IPCC assessments, etc.). A model which lack sufficient treatment of all suspected independent variables – and their interaction is – under- ie., mis-specified. Result is that the model will tend to over-emphasize or under-emphasize attribution for the variables that are fully treated. I have long suspected this to be the case in climate modeling for global warming. There are many forcings and
some are known to be underrepresented in the modeling such as aerosols / clouds and black soot.

curryja: Danley,
very true, same goes for solar also.
Um, what?

OK. I am stretched to the limit. Somebody has to call "horseshit" here, and it might as well be me.

We have reached a point where it is impossible to judge that Curry is in touch with the science that she is supposed to be a prominent participant in. So has she lost touch, or has she never had much scientific insight to begin with? That's the only question any of this burbling raises.

Admittedly, she is very highly published. I know a couple of her students and think highly of them. On the other hand, to be honest no paper of hers has ever come across my radar in anything I've investigated. (As a dilettante, I don't contribute much to the primary literature myself, but I do read a whole lot of stuff.) I mean, could this be the stuff of some subtle neurological decay, where a formerly competent scientist starts making no more sense than the peanut gallery? After all, dedicated naysayers are still highly intelligent and scientifically competent by comparison to the lay public (that's the whole problem) even though they are actually quite ignorant and confused about the actual science. So a decline to that level of functionality would not be obvious, and if a person already had tenure, it would ordinarily go uncommented upon.

Or alternatively, is the peer review system so shabby that a person of modest intellectual accomplishments, one who, despite years of connection to the scientific community, numerous publications and promotion to a position of responsibility, is capable of such vapid, illogical, pointlessly contentious writing.

Either way it's sadly amusing to see this nonsense treated by the fan base as the breakthrough in reasoning about uncertainty that it obviously isn't.

But as far as I can see, the uncertain hypothesis raised here is

"Did Judith Curry jump the shark (green), or was she born and raised on the far side of the shark in the first place (red)?"

I think that covers all the possibilities, unfortunately, and it's either awkward or really really awkward, depending on which way it comes out.

(Note: all emphases in quotes added by me.)

Update: This post has generated some interest on a thread at Kloor's (starting with AMac lighting into me at #49) Judith Curry herself responded rather graciously, given how harsh the above was.
Well this is entertaining. MT and others seem annoyed because they think I invented uncertainty or am taking claim for it or something? Hardly. Its the Emperor’s New Clothes thing. And the fact that MT and others don’t get it (i.e. that uncertainty and allegations of overconfidence of IPCC are important things to talk about, its the naked emperor, really) just tells me how clueless some members of the community actually are.

I give MT credit for at least discussing what i say in the blog, rather than rehashing old drive by comments that I’ve made at other blogs. But i suggest he try out his arguments over at my blog, where they would receive some real dissection from some serious experts in logic, bayesian reasoning, etc. Nobody ever burns their bridges with me in terms of meaning i wouldn’t pay attention to their argument.
I replied:
I have to admit this is a surprisingly gracious response to my less-than-gracious posting. I am, in that regard at least, impressed and grateful.

I still can extract no sense from the Italian Flag arguments to date; it seems to me that there is no unifying method at all, just a sort of fig leaf for various commingled classes of rough intuitive guess.

Now, arguably that is all that IPCC is providing, and all we’re discussing is whose intuition is more reliable. If that is the case, though, that is how it should be discussed. Devices intended to illuminate should not obfuscate.

If you want to discuss uncertainty, and decision-making under uncertainty, by all means, let’s do that. (I’ve been trying to close that loop for decades, myself.)

As for the critique of models which so exercises Tom Fuller, let me withdraw it for the sake of more productive argument. If Dr. Curry wants to throw red meat to the inactivists on occasion, she should be held to account. But that only a secondary cause of my disappointment with her contributions to date.

Let’s focus on where the focus belongs, on how to think about uncertainty.

If Dr. Curry will continue to allow me to post on her site I will actually be grateful but I will nevertheless behave as an ingrate. If Dr. Curry is to make a genuinely positive contribution to the problem of how to deal with uncertainty in the high-stakes field of climate policy, she will need to proceed at least with considerably greater clarity than she has managed to date. It’s my impression that considerably greater care is needed as well.

I will continue to be an advocate for clarity and precision of thought. I hope others with some interest in uncertainty will stop yielding Dr. Curry a free pass on these matters, where she is an obvious novice.

If she actually wants to participate in a discussion of uncertainty, then it is important to do so carefully. One aspect of the problem is separating out one’s own biases from the various other sources of error, and another is careful thought along lines that are unfamiliar to most physical scientists. The casually appealing ideal of “separating politics from science” may turn out to be more subtle of a matter than it might at first appear.
I guess I was in a dreadful mood, too. The world is looking particularly messed up to me these days. (Willard has taken to calling me Doctor Doom, but I assured him that I am Victor to him.)

None of that means the Italian flag stuff made any sense, nor that Curry should continue to get a free ride. Science, in the end, is not about centrism or extremism or purity or pragmatism. Science is about reason, logic, and honest contention of ideas. I am at least provisionally convinced by this exchange that whatever else is going on, Curry honestly believes in that.

I think we should take her up on it, next time she waves that flag. I suppose we should ignore what the press or the peanut gallery thinks of her and focus on her reasoning or lack thereof.

Update: Would this posting have gotten any attention at all without the "snarky" bit at the end?

I really do think Judith Curry either jumped the shark or was never on this side of the shark. This flag stuff really looks very amateurish.

It might have been more prudent on my part not to ask the question in that way. But I did want the whole issue to get some attention, and in that I succeeded. I certainly wont apologize for this flavor of criticism to anyone who doesn't hold McIntyre to a comparable standard.

I'm impressed by the constructive spirit in which she receives this criticism. I will be more impressed if she actually addresses it. Indeed, sharks of this breed can be unjumped, as it appears Claude Allegre has just demonstrated. I'm willing to grovel on the substance if somebody can make a coherent case for it.

Anyway, if someone can't bear the sight of this sort of criticism, PDA has provided a redacted version of those parts of this article that address the uncertainty "flag".

Update: Pleased to see James in agreement.

: Fuller raises the interesting question as to whether I posted this out of scientific or political motivation (or, for that matter, out of sheer self-destructive stupidity, which I've been wondering from the start).

Here's my defense.

While there is no room for ad hominem arguments in science, what Curry is doing is apparently very far from science. Then the question of what she is doing and why becomes relevant as a political question, yes. I present a case that IFA as we have seen to date is not science.

Is she doing not-science because a) she knows it is not science and wants to fool others b) she is no longer capable of doing science or c) she was never capable of doing science?

Now, I can assure you on the basis of experience that this conversation is going on behind the scenes among actual, real scientists. The question is only whether I was right or wrong to raise it publicly, to bring it into the open.

There is no doubt I was rude within the norms of science. I stipulate that.

The credulity and adulation associated with the transparent nonsense has been a matter of some political importance. There has never been much risk that this nonsense would percolate up through scientific discussions, but there is an increasing risk that it will be forced down to science from the congressional level. So arguably it's important to raise the question, and I did so.

In this case, the contradictions are elementary enough to be accessible to a diligent political staffer. So making the case in such a way that such a staffer would be likely to come across it and work through it may be important. It's not hard to imagine this cluster of half-baked ideas making its way into the national discussion via too much credulity at the top.

Therefore, for a change Tom Fuller is right. My motivation is indeed political. I wish to defend science from an injection of nonsense from the political level. Lysenkoism never works out very well. And Lysenkoism is exactly the central risk of politicization of science.


Anonymous said...

Just for clarity, the forum comments are from the post


Doesn't make them any better or less pertinent.

Joshua Stults said...

I find the cranks (peanut gallery) on Curry's site annoying, but I find the cranks on your site annoying too. Such is life.

adelady said...

The weird white bit on the flag leaves me mystified.

I followed the intro OK. Then I got to that rising temperature explication of using the flag and was completely lost. Still am.

Michael Tobis said...

jstults, say "La V".

Simon Donner said...

Thanks. That "italian flag" post was the one post from the new blog that I've seen, and I too was confused by the logic.

Joshua Stults said...

I've noticed that Dr Curry tends to be more accepting than I'd be of comments I'd consider crankish (though she does a pretty good job of ignoring the real wackos). I'm going to assume good faith, and chalk this up to maybe a bit of over-compensation against being a mean girl.

I don't like the flag (but I appreciate the attempt at communication). I think the unwashed masses can handle things in terms of odds and probability (people seem to be intuitively Bayesian, within limits). The flag device should be judged pragmatically: if it is the source of more quibbling and fruitless discussion rather than elucidation and insight then it's not a good communication tool; otherwise let that freak, um, uncertainty flag fly!

I don't understand the point you are trying to make about conflating hypothesis with weighting. If duck and not-duck are our hypotheses (models if you prefer), then don't we associate a weighting (a conditional probability, in fact) with those two? Things are more interesting when you have a larger model space, say, duck, goose, gander and none-of-those (tricky to treat that last). Also, I think the discussion would be clearer if you stuck to continuous or discrete spaces.

Writing is a series of drafts, blogging is a series of drafts in public. La V!

Michael Tobis said...

It's one thing to tolerate cranks.

Hell, Eli practically welcomes them, and his comment sections are still well worth reading. (Perhaps a beneficial side effect of obscurantism?)

It's another thing entirely to encourage them and agree with them.

Crank: There are many forcings and some are known to be underrepresented in the modeling such as aerosols / clouds and black soot.

curryja: very true, same goes for solar also.

As far as I know, all three (or is it four) accusations are flatly false, as any reference to IPCC or to some very prominent Hansen papers would reveal.

Curry is surprisingly irresponsible in encouraging this comment (from someone who isn't clear about the distinction between clouds and aerosols, apparently) and piling on.

This is not how adult scientists normally talk about science, not even among themselves, not even in passing in blog comments, not even in unguarded moments.

It seals the deal for me. She isn't serious and shouldn't be taken seriously.

The serious question then is whether she got so far in her career with such a shallow grasp of science both as culture and as content. If so, Curry actually delivers an indictment of the maturity of climate science as a culture (if not necessarily as a body of knowledge), not by the content of her sophomoric musings themselves but by their very existence.

Apologies to any sophomores reading. It is supposed to be a curable condition.

Tom said...

Of course you would call horseshit. It's a subject you're expert on.

Blaming Curry for her commenters... Okay, I now hold you responsible for every pathetic piece of drivel your commenters have written here.

At that, their crap is now rivalled by your piece. Bah. You've become a cheap pimp.

Michael Tobis said...

No, I do not blame Curry for her readers. To some extent I blame her readers for Curry.

The response where she eagerly agrees with somebody who obviously (to someone who does know) doesn't know what he is talking about and one-ups him in cluelessness is sadly revealing.

But anyway, that's a secondary point. The primary point is that she is not making sense. None. Whatsoever.

Since she already has money and position, this groveling for respect among ill-informed outsiders is peculiar.

Alas, given the politics of the situation, it amounts to more than a personal misfortune, else it would not be worth remarking upon.

The reason for bringing commenters into it is this: if the topic weren't fraught with politics, she wouldn't be tempted to appeal to a prejudiced and ill-informed audience by reaffirming their prejudices. This is because that audience would not have been drummed into existence.

But the importance of the topic means that somebody sufficiently capable, who trudges through her verbiage enough to see that there really is nothing like clarity of thought there at all, is obligated to report that.

DirkD said...

Recall that Curry's problem with most climate scientists is that she consistently fails to be specific in her critiques. The Italian flag example, while appearing to lend some modicum of specificity in her argument, adds precisely - and practically - nowt. mt's argument is the simplest way of showing this up IMO.

Indeed, jstults is right here - "if it is the source of more quibbling and fruitless discussion rather than elucidation and insight then it's not a good communication tool." It plainly isn't, and it equates to more smoke and mirrors.

Instead, ask her "Where's the specific evidence on how IPCC are not treating uncertainty about solar/aerosol/clouds correctly?" and she deflects the question. It's a bit like Pielke Sr and his endless landuse/land cover fetish, really. There's no point in assuming good faith with her when past evidence with RPSr. (whom she is in danger of transforming into) doesn't support this.

dhogaza said...


"As far as I know, all three (or is it four) accusations are flatly false"

And she's been told so, by Gavin Schmidt, among others. It's one thing to be wrong, it's quite another thing to be wrong, then to be corrected by a leading expert in the field, and to then go forth and repeat the same error once again (or in Judy's case, regarding models, many times afterwards).

"Of course you would call horseshit. It's a subject you're expert on.

Blaming Curry for her commenters..."

No, Curry is being blamed for agreeing with three incorrect claims about climate models, and for adding yet another incorrect claim to the list.

Claims she should know are incorrect, because she's been told so by (among others) Gavin Schmidt.

If she doesn't trust Gavin, she can go read the documentation, underlying papers, and actual code relevant to GISS Model E and educate herself.

What she shouldn't be doing is to run around claiming "the models sucks because of X, Y and Z" when X, Y and Z are demonstrably false. Demonstrably false on publicly available servers, in source form, in documentation, in the peer-reviewed literature ...

DirkD said...


Slightly OT point here.

While I'm immensely impressed with your belief in the First Amendment, would it be possible to either edit or reject Tom Fuller's comments?

How is a comment ending with "You've become a cheap pimp" not either rude, excessively contentious, repetitive, or spammy?

To extend the metaphor, if Curry's born beyond the shark, hasn't Fuller been eaten, partly regurgitated, eaten again and subsequently excreted by Carcharodon carcharias?

Michael Tobis said...

Dirk, as William said on Stoat recently, one is tempted to leave the more extreme items in the stream as evidence of the sort of discourse we are up against. And in this case had I purged Tom, we wouldn't have had your delightful expansion on the shark motif.

Nevertheless, agreed, enough said.

Fuller is barred from this thread as a topic, and is barred from the thread as participant unless he makes an unlikely effort at addressing the substance of the article.

Anonymous said...

"Claims she should know are incorrect, because she's been told so by (among others) Gavin Schmidt."
Yeah, in the 'Attribution part III" thread, I posted the references to her conversation at collideascape with Gavin and also pointed out to her why her accusations are probably (I only say probably because I'm not expert, but I'm fairly sure I am correct here) complete misrepresentations about how, not only the GISS models work, but the IPCC AR4 models in general, by given text references from the IPCC itself. This is a bit frustrating because a little later in another thread, 'Heresy...' she keeps repeating the aerosol issue, IMHO, in a damaging, and factually incorrect way.

Rattus Norvegicus said...

Don't forget that before jumping the shark, she drank the kool-aid.

dhogaza said...

"Yeah, in the 'Attribution part III" thread, I posted the references to her conversation at collideascape with Gavin"

Yes, it was your post there that caused me to chase the link and to then discover how she's repeating stuff she's been corrected on previously ...

Thanks for that!

It demonstrates Kloor's cluelessness as well, unfortunately.

Aaron said...

If you are out along the river on a spring day, there will be both epistemic uncertainty and ontic uncertainty about which, and how many critters (mosquitoes, ticks, black flies, and etc.) would like to eat you, but there is no doubt that you need to take pro-active action, or you will get bit by some critter. Thus, the “uncertainty monster” does not stop me from applying DEET.

People that believe in the “uncertainty monster” and do not apply insect repellent, end up in the hospital with an insect born disease. Thus, the fallacy of the “uncertainty monster” is self correcting.

manuel moe g said...

Bye-bye Italian Flag - the world didn't need yet another vague way of speaking of uncertainty.

Uncertainty is only worth talking about if the overall statement is one of certainty -- "my historical records of rainfall, and my model for using those records to predict the future, lead me to say there is a 60% chance of rain tomorrow, and so I choose to carry an umbrella."

Because neither rain nor sunshine can invalidate "60% chance of rain tomorrow", the (possibly implied) statement about my data set and models and methods and decision process is really the most important part of the whole sentence.

Uncertainty is only worth talking about if the overall statement is one of certainty, because a statement only has content if it can inform a rational decision of a course of action. (Using this language, we consider deciding to wait to be taking an action.)

So phooey to mumble-mouthed musings about uncertainty, just a another technique of the Art of Controversy.

Anonymous said...

Before descending into her nonsense, she makes one good point - much of the "climate debate", if one can really call it that, is becoming little more than a tribe mentality. That's really starting to worry me and it's leaving the science behind.
She doesn't help in her post however, as you demonstrate here MT; she further extends the anti-science attitude.

Steve Bloom said...

moth, the political masters of the denialists engendered this debate (which Judy characterizes as "tribal", although that's not a term that most sociologists would find illuminating IMHO) as their only means of avoiding what they understood to be the clear implications of the science. Judy's attempted alternative narrative is absurd.

jules said...

I suppose the universities are to blame, but it seems to me that people raised as climate scientists are all raised on the far side of the shark, as far as statistics are concerned. As a result of their ignorance they invent all sorts of nonsense, and lack any statistical intuition. Now don't get me started on the statisticians who have no scientific intuition... ;-)

Unknown said...

Beyond the ridiculous jump from confidence to probabilistic weighting, this line from Judith Curry is problematic in another way:

"and I interpret most to mean between 51 and 90% (lets pick 70%), with the remainder (30%) associated with natural variability."

"most" in reference to the IPCC phrase "most of the observed warming". The word "most" in the dictionary simply means "majority", so why is JC eliminating 91-100%?

Moreover, the IPCC conclusion in no way discounts the possibility that natural factors may have had a cooling effect, offsetting even more than observed warming from anthropogenic factors. This in fact they determined as being "likely".

Ch. 9 Exec. Summary:

"The warming occurred in both the ocean and the atmosphere and took place at a time when natural external forcing factors would likely have produced cooling. "

Ch. 9 Exec. Summary

We can also see that in Figure SPM.4, where models indicate natural factors alone on average have a slightly negative on temperature since 1950.

Figure SPM.4

I tried to explain this to her over at Kloor's place once but it went ignored.

I also agree that these things are rather basic errors and distortions, not indicative of your typical published climate scientist.

MT: "Fuller is barred from this thread as a topic, and is barred from the thread as participant unless he makes an unlikely effort at addressing the substance of the article."

Perhaps he will run back to his blog and whine about how "warmists" are silencing debate and constructive comments like "You've become a cheap pimp".

Unknown said...

i am a bit confused about the contradiction: "according to Curry's mangling "My assignment allows the anthropogenic influence to be as large as 98% and as small as 98%". In other words, a well defined uncertainty yields an inconsistent certainty. "
could you spell it out in more detail. my confusion lie (i think) in the fact that if one eliminates the white area of the flag, wouldn't one expect the "evidence for" a hypothesis not to vary?

Michael Tobis said...

O'Neil I have no idea what it might mean. That is the point. I simply followed the structure of the 30% - 70% argument in the template. the example which Dr. Curry provided.

The thing is that if you buckle down and try to understand what she is saying (instead of just nodding in enthusiastic agreement with the "not the IPCC" position) it is incomprehensible.

In oarticular, the difference between the low end estimate and the high end estimate (presented as a hypothesis) is converted into an uncertainty range (somehow changed to an estimate). So if there is nothing in the white region, even if you contrive the statement as a perfectly conventional statement of uncertainty, the uncertainty goes away under the transformation she offers.

I think that transformation is nonsensical, so I constructed an example where it obviously made no sense.

adelady said...

I once knew a bloke who was part of a group I spent time with. But he sort of disappeared off the scene a lot. Turns out he had another group of friends who I thought (maybe snobbishly) were certainly uneducated and not very interesting to me. I asked him about this.

I cannot remember what he said, only my reaction. I thought - you want to be the cleverest person in the room. He'd much rather be admired by people who were not his intellectual equals, than participate with people who were and who would occasionally display more knowledge or insight than him.

I sometimes see a flavour of that in a bit of the interactions at jc's. Rather than being interested or informed by vigorous interaction with her peers, she's found a group of admirers.

(Can't say uncritical, if she did anything serious on high-side sensitivity, they'd tear her limb from limb.)

Anonymous said...

Steve, I totally understand and have witnessed it first hand. There's no doubt that by making this "debate" more a tribal, team-sport type of thing, denialist have effectively removed logic and replaced it with emotion.
It's become pointless trying to engage and inform with those who call themselves "sceptics" because they simply don't want to hear it.
That it's been engineered is, at this point, unimportant - it's occurred and we need to work out how to defuse the passionate irrationality of the common denier, before it ends up like northern Ireland - if we get to that, there will be no preparing for a world beyond fossil fuel addiction.

Paul Daniel Ash said...

Dr. Tobis, as I noted at CaS, I've grabbed the source of this post and re-posted my redaction to it on my WordPress blog, with formatting intact.

I don't know if it'll be any more helpful, and if you have any objection to it I'll take it down. I just thought it might be interesting to see if there could be a discussion sans tone trollery.

I've also emailed Dr. Curry and invited her response.

Michael Tobis said...

No objection at all. It will be interesting to se if anything of substance turns up in rebuttal.

David B. Benson said...

There is a standard way to apply Bayesian reasoning.

Steve Bloom said...

Obviously there are specific things that the IPCC considers to be evidence that Judy does not and/or things Judy considers to be contrary evidence (actual or potential) relative to the IPCC. Those things are, insofar as I'm aware, that there's low sensitivity and (less certainly) significant T increases driven by changes in ocean cycles. The problem is that she hasn't made a case for either of those beyond her own intuition. So the whole Italian flag business just begs the question.

Paul Daniel Ash said...

Anyone interested in a more rigorous implementation of the "Italian flag" could take a look at how Hall et. al. used it to illustrate interval probabilities.

It's actually rather interesting (at least to someone like me who forgot nine-tenths of what he learned in Math 380).

andrew adams said...

A comment by Curry from a recent thread

Monty, I regard the following statement to be controversial:
Climate sensitivity must be higher than 2C
Any climate variations (warm, cold) undoubtedly lead to negative consequences for someone, “danger” has not been well defined or convincingly argued for.

Her second point simply indicates that on a significant section of the science she is simply clueless and I'm amazed that someone in her position can make such a statement without extreme emabarrassment

The first shows (along with her comments about the probability of AGW as far as I understand them) that her opinions appear to be (and it is very difficult to be sure as she seems to avoid making a firm commitment on what she actually does believe as much as possible) far closer to the skeptics than to mainstream science. In which case how is her proclaimed aim to "engage with the skeptics" in any way meaningful? Certainly her idea of "engaging" is to constantly say "yes, you have a good point" in response to any old nonsense.
Frankly, her entire blog comes across as en extended exercise in concern trolling.

Horatio Algeranon said...

IPCC: Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.

Horatio could be wrong (has been before once or twice), but if the IPCC statement accurately reflects the underlying uncertainties, it would seem that the above actually implies a value for the minimum amount of warming due to increases in anthropogenic greenhouse gas concentrations over the period in question.

One can calculate the value of this minimum with mathematical expectation, using the total observed warming since the mid-20the century (about 0.6 degree C) and the most conservative assumptions: ie, that "most" means "51%"(min) and "very likely" means "with 90% probability" (min)
The expectation value for the minimum warming due to anthropgenic greenhouse gas increases would then be

(0.51)(0.6C)(0.9) = 0.275 C

.275/.6 = 0.46

In other word, the IPCC statement in question would seem to indicate that at least 46% of the observed increase in global average temperature since the mid-20th century is due to the observed increase in anthropogenic greenhouse gas concentrations.

Horatio does not know the actual purpose of Curry's flags (only knows that under normal usage, smart folks do not hesitate to use the white one when backed into a corner -- to surrender), but is pretty sure that her statement that
"My assignment allows the anthropogenic influence to be as large as 70% and as small as 30%"
is not actually in keeping with the IPCC statement.

First, that particular IPCC statement is really (at heart) about the minimum amount of warming due to greenhouse gases over the period in question and says nothing about the maximum.

Second, the values in the lower part (30-45%) of Curry's specified range (30-70%) are actually below the minimum (46%) calculated from the IPCC statement and therefore not consistent with it.

Steve Bloom said...
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Michael Tobis said...

Horatio, no. I do not think so.

A 90% confidence in a 51% fraction does not imply a 100% confidence in a 46% fraction, which basically is what you just said.

Tom said...

You're pathetic. From CaS:

Brandon Shollenberger Says:
October 30th, 2010 at 12:52 am
Two things. First, Michael Tobis’s behavior is pathetic and unacceptable, regardless of whether there is any merit to his claims.

Second, Michael Tobis is wrong. In fact, he is obviously wrong. Judith Curry was not expressing degrees of certainty or belief with her Italian flag analysis (IFA). She was discussing the levels of evidence. Her personal belief is 30% of warming trend is anthropogenic, 30% is natural, she doesnt’ know about the other 40%. It’s really quite simple.

There are two possible defenses for Tobis. The first defense Curry did mess up when she applied the IFA to the IPCC statement. She took a confidence level of 95% as indicating 5% of the evidence was undecided. This is obviously wrong, but it is small mistake anyone could make in a moment of carelessness. The second defense is he could claim the general wording of her post was unclear. Unfortunately (or perhaps fortunately), both of these defenses are untenable.

You see, Michael Tobis raised his concerns some time ago, back when Judith Curry’s thread was still fairly new. Half an hour later, another poster explained why Tobis was wrong. Four hours later, Curry acknowledged that other poster was correct.

So Tobis raised a concern with Curry’s post. It was immediately explained away. He said nothing. Over a month later, he repeated those concerns, only this time as damning criticisms.

This entire charade is ridiculous.

James Annan said...


Your smokescreen and distraction tactics are tedious. Curry's confusion is evident and more than a little embarrassing, given the strength and volume of her claims. It will certainly be interesting to see if she says anything coherent and quantitative in her forthcoming Climatic Change article. My bet is she'll be long on vague claims and insinuation and short on specifics.

I'd be more inclined to give her the benefit of the doubt if this pattern of behaviour wasn't so well established. At this point she has burnt though all her credibility IMO.

Tom said...

James Annan,

Lame. Fail. But then, you're trying to defend the indefensible.

Tobis: (self-snip).

Michael Tobis said...

Shollenberger via Tom (probably Fuller):

Michael Tobis is wrong. In fact, he is obviously wrong. Judith Curry was not expressing degrees of certainty or belief with her Italian flag analysis (IFA). She was discussing the levels of evidence. Her personal belief is 30% of warming trend is anthropogenic, 30% is natural, she doesnt’ know about the other 40%. It’s really quite simple.

Very well, IFA. I like that. Let us recall another piece of IFA, and apply Shollenberger's interpretation.

From the first ref above:

Will the climate of the 21st century will be dominated by anthropogenic warming (green) or natural variability (solar, volcanoes, natural internal oscillations)?

which is the question with the greatest policy relevance, IMO. My scores on this one are

* green 25%
* white 50%,
* red 25%.

On Shollenberger's interpretation, this means 25% of next century's warming will be natural, 25% will be anthropogenic, and 50% will happen but Curry doesn't know why.

This interpretation is, um, hard to interpret. Why will there be natural warming next century? And why will there be additional warming which she is currently unable to attribute?

I do not think she is making these peculiar claims. Which is the point. It is not that one or another interpretation of IFA fails on any single assertion. It is that across the writings we have seen so far it is incoherent.

I picked the example here specifically because two interpretations were presented in the same example. The fact that Shellenberger can understand one of them and ignore the other does not help us make coherent sense of Curry's IFA analyses.

Now more than likely Shellenberger is a sock puppet for the think tanks that find Curry convenient, which is why he is indulging in this bit of misdirection.

As for Tom, well, I don't know why he thinks he does what he does.

He seems convinced that I am a bad guy because I am convinced that Curry is not making sense and found the courage to stand up and say so loudly enough that the more intelligent folks on the other side would have to take notice.

I may be an idiot (anyone looking at my paycheck would agree) but I am not being a bad guy. I'm taking a hit for science, and against politics disguised as science.

Which is sort of ironic, I guess. But that's a longer story than I have room for in this margin.

Tom said...

You're a bad guy. That's the politest way of expressing it.

As for why, ready your own fucking post.

Steve Bloom said...

Michael, maybe you want to reconsider your remark above about not wanting to blame Judy for her commenters.

Note that it's Shollenberger, not Shellenberger, so presumably no BTI connection.

King of the Road said...

Tom Fuller is an interesting case study, utterly self righteous without a hint of ability to discuss fact. I don't know if he's so utterly and rabidly blinded by his hatred for Tobis that any ability to think rationally that he might have is stunted or that the lack of such ability is what causes his uncontrollable, foaming at the mouth emotional outbursts.

As to Curry, when a scientist writes in such a way that I can follow the explication of the fuzziness of her thinking, there's a problem. And as Andrew Adams states up-thread, Curry has a terrible habit of replying with "yes, that's a good point" to anything. It exhibits strange insecurity for a practicing scientist. She must be trying to please someone, who and why I don't know.

If this is too contentious, dump it but I feel better for having committed it to bytes.

Anonymous said...

My attempt at explaining Judith's rant on 'heresy';

This just gets weirder.

So Judith thought she was one of the “masters of the universe” until discovering that having public spats with fellow scientists wasn’t very clever.

As penance, she decides to engage in ‘kumbaya’ dialogue with people who wish to deny basic physics.

A correction to the former was probably in order, but why is it that people often jump from one extreme to another. And in this case, very probably a most unhelpful one. Well informed scientists yelling at each other is at least likely to generate some insight.

And equating the IPCC as “dogma” and posing as a victim just because a journalist chooses the word “heretic” in a headline (and a note of warning here – the article itself never uses such wording, strongly suggesting it was thrown in by an editor) says absolutely nothing about the “insiders” of the IPCC, only about journalists. Looks to me very much like someone’s getting a little too keen to make themsleves the story.

“then count me in as a heretic” – what self-indulgent nonsense.

Lars Karlsson said...
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Lars Karlsson said...

“Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”

The “most of … due to” part here is a statement about attribution (“most of” interpreted as “>50%”). This is not a probability. However, it is an imprecise statement of attribution. We can write it as: f > 50%.

The “very likely” part is a statement about uncertainty (probability 90% or more, let’s say 95% for simplicity). We can write it as: P(x) = 0.95 where x is some statement that can either be true or false.

So the “most of” statement is “very likely” to be true. Or to put it in mathematical terms:
P(f > 50%) = 0.95
And from this we can also conclude:
P(f <= 50%) = 1-P(f> 50%) = 0.05
So the IPCC statement has committed 95% belief to an attribution of more than 50% of warming to antro-GGs, and 5% belief to an attribution of 50% or less of warming to antro-GGs .

There is no point to talk about “uncommitted belief” here. Yet, Curry somehow turns those 5% into “uncommitted belief”. But this is not what they are. Curry really doesn’t make sense

Anonymous said...

My biggest beef with Curry's "doubt" piece is that she seems to claim equal evidence pointing to natural variability being dominant over the next 90 years as compared to anthropogenic forcing. Or alternatively, an equal portion of 21st century climate change being attributable to human induced warming as to natural variability.

Or perhaps I suffer from the same confusion as she did?

In any case, both these explanations seem way out of touch with the available evidence and current understanding.

See my detailed response to her arguments here:



Marion Delgado said...

As usual, the commenters are skimming until they discover whether she's writing "goodthink" or not.

In addition to not being restricted to the real world when arguing, which is a huge advantage, they're all obviously not crippled by false modesty, either.

Marion Delgado said...

Also, my money's on real scientist, gone emeritus while still active, and probably for crank political reasons, attention-seeking, and an inability to admit error in public.

Michael Tobis said...

The rate at which new errors (or at best woefully unsubstantiated sweeping assertions) keep emerging is astonishing, though. Possibly without precedent.

Paul Daniel Ash said...

Then you need to formulate the counter argument, which would be that 20th century warming can be explained by natural variability. Two candidates for this are the multidecadal ocean oscillations (e.g. AMO, PDO) and solar, there are others.

Oh, my.

Anonymous said...