Wednesday, April 28, 2010

Curried leftovers

The real news is that our last guest finally managed to get a flight back to the UK. But as for the latest froth on the blogosphere, I'm late to the party again, and grovelling around for the scraps...

Actually, I don't think there is much point. Stoat covers it pretty well [1, 2, 3], and I can't find much to fault in his analysis, so I'll just provide a few excerpted highlights. Judith Curry gives every appearance of basically channelling the sceptic talking points, sadly (for her) without being aware of the underlying facts. I particularly liked her OTT condemnation of DC when he accused Wegman of plagiarism, followed by hasty attempts to change the subject when it turns out that he was undeniably correct. Much of the exchange can be found on the lengthy comment thread on this post.

Let me say that this is one of the most reprehensible attacks on a reputable scientist that I have seen, and the so-called tsunami of accusations made in regards to climategate are nothing in compared to the attack on Wegman.
Hyperbole much, Professor Curry?

With commenters repeatedly pointing to the mountain of evidence in support of the claim, as posted on DC's excellent blog (not to mention various other bogosities in the report itself, and Curry's unfortunate misapprehensions as to its origins):
On comment regarding my comments on Wegman (not the Wegman report per se). The whole host of issues surrounding whether or not he is biased, the plaigarism accusation, and whatever else, are issues that I have not investigated in any detail (and don’t intend to). So my comments on this should not receive any undue consideration; they were made when i thought my mention of the Wegman Report was going to be hijacked by the plaigarism issue being raised at deepclimate. This is last word on that subject, and request that Keith not allow any more comments on this topic of plaigarism.
Bottom line is that I just don’t know that much about the Wegman situation, I have acknowledged this several places in the thread. Given this, I hope we can move off the Wegman topic.
Yeah, I bet you do. Some might consider an apology would have been much more appropriate.

The whole anti-IPCC schtick is pretty tired too, and the "failings" of Oxburgh etc, as Stoat covers. Plus:
In my opinion, there needs to be a new independent effort to produce a global historical surface temperature dataset that is transparent and that includes expertise in statistics and computational science.
Good luck with that. It's not like there are already 3 or 4 major groups around the world with decades of experience in this work. Oh wait, actually there are. And they all get the same results (modulo a few details for which there are well-known explanations, such as GISS extrapolating over the Arctic). Oh, but that just means they are all in the conspiracy together, right? And they are all discredited because of Jones being rude about someone behind their back, or the hockey stick, or something like that. Really, I have to wonder whether she has investigated the other issues in more detail than the ones relating to Wegman, that "should not receive any undue consideration"...


Steve Bloom said...

A little closer to home for you, she thinks sensitivity is 1.5C, but despite multiple challenges has failed to back up her view with anything of substance. I pointed to the recent Pliocene results as putting 1.5C on thin ground, to which she responded by referring me to Knutti & Hegerl 2008. A lot of the Pliocene stuff is more recent, in particular Lunt et al. 2009, but more oddly K&H seems like an strange place to look for support for 1.5C.

David B. Benson said...

Hard to reconcile a low climate sensitivity with the results here:
Global wrming, decade by decade
showing a response to date of 2.28 K when normalized to 2xCO2.

James Annan said...

Yes, I saw she was grumbling about the IPCC lower limit, apparently without any substance. She doesn't seem to know anything of the work that justifies this claim and has never made any contributions in this area, as far as I can tell. So I have no idea what basis she has for that criticism.

Frankly, it is hard to distinguish her behaviour here from the typical argument-from-ignorance of the garden-variety sceptics. The only real curiosity is in why she is coming out with this stuff...

Steve Bloom said...

I did notice a little more specificity from her, which was that she thinks the PDO or other ocean cycles may have resulted in a warm '90s that tricked folks into thinking sensitivity was higher.

Also, James, I hesitate to ask, but would you be willing to take a quick look at David's idea? I'm sure it's just curve-fitting (sorry, David!), but on the face of it the AMO adjustment does look pretty good.

Anonymous said...

good effing grief, it's getting even better

The people slagging off on McIntyre, Watts et al. have probably spent no time over at their blogs or made an effort to get to know them personally and understand what makes them tick. Or to talk to the scientific skeptics like Christy, Michaels. Or talk to the libertarian think tanks, like CATO and CEI. Well, i’ve made that effort, and therefore I think I know alot more about the what the “deniers” are really like than the people accusing me of naivete, who have drawn premature conclusions because somebody found some sort of obscure link to an oil company

William T said...

I think that if you spent a lot of time reading those blogs, with an "open mind" trying to understand where they're coming from, then it might have an effect. Stockholm syndrome, as apsmith has said already.

Bart Verheggen said...

Curry said that climate sensitivity may not be so well constrained at the lower bound as it's made out to be, and agrees that at the upper bound it isn't well constrained either.

That kind of leaves JulesandJames' work on this out in the woods, but she didn't claim that sensitivity is 1.5C, or did I miss that somewhere?

I think her critique of the strong 'us-versus-them' attitude deserves serious consideration, though she seems to omit any of the context of how science is under attack, which is a very serious omission indeed. said...

I asked a similar question at your site, but might as well continue here.

What is Curry's upper bound of CS estimate? Can you point to a passage where she discusses this clearly? Thanks! said...

Now that you have had a chance to reflect, perhaps you should extend your observations about Curry's statement on my analyses of Wegman et al, a statement excerpted above and at your blog.

You called Curry's satement "odd". I maintain that it was ill-informed, erroneous and therefore completely unjustified. For example, Curry specifically said my analysis was based on a single definition from Wikipedia, when in fact most of the 7 pages of material discussed have apparent antecedents in three different text books.

I also note, echoing James, that refusing to discuss a statement is not the same as withdrawing it.

Bart Verheggen said...


I don't think Curry mentioned an upper limit, though she did say that it was more poorly constrained. Seems to echo a bit the Roe and Baker line of thought (without being specific though).

I'm not defending Curry's statement regarding your Wegman analysis at all. It strikes me as ridiculous to claim that the recent attacks on science are minor in comparison to what you wrote about Wegman. But I haven't looked very much into the hockeystick affair and even less so in the Wegman report or its discussion. So I'm not gonna opine more on it (and don't have the time or desire to investigate it deeper at this point).

You're right that she hasn't subtracted anything. She seems to have gotten lured into a discussion that wasn't intent on having, and probably regretted it after the fact.

bart verheggen said...


Just to clarify, since it appears that you took offense to what I wrote over at my blog:

The only reason I brought up the Curry quote regarding your take on Wegman was to contrast it to how silent she is on the attacks on science, which I find an important omission on her part.

I didn't mean to endorse her view of your blog at all. I think your deep digging into all this hockeystick stuff is very important, since it is such a central issue for the 'skeptics'. I haven't looked much into it though, so generally try to circumvent the discussions surrounding it (except occasionally, but then more so to highlight McIntyre's communication tactics rather than technical details).

deep climate said...

I didn't take offense. Really. And I certainly did not understand your take as an endorsement of Curry's statement (although I think you could have been much clearer on that point). And I'm sure you know that I am in broad agreement with almost everything you write.

But I do think you are not seeing the full context of Wegman et al.

It's not just a contrarian touchstone that is deeply flawed and should be exposed as such, as important as that may be.

Wegman et al has to be understood in the context of the Barton investigation, which represents the worst excess (so far) of the partisan "attacks on science" you rightly deplore. That also means that it is a glaring red flag for any "honset broker" to tout Wegman et al.

I don't think you need to understand very much about the content of the report itself to understand that. But it helps, admittedly.

David B. Benson said...

Steve Bloom --- Not just curve fitting, but also a rather careful simplification of the ocean + atmosphere response. If you wish to go into detail, this globalchange thread is a good place to do so.

As for the AMO, I added that for those who were overly concerned about the wobbles around the secular trend.

Steve Reynolds said...

James Annan: "Yes, I saw she was grumbling about the IPCC lower limit, apparently without any substance."

James, your own paper says:
"We should therefore update the expert prior with the likelihood function arising from FG’s analysis of the ERBE data, and present the results in Figure 2. The resulting 5–95% posterior probability interval is 1.2–3.6C…”

So I am puzzled why you say considering the possibility of 1.5C sensitivity is without substance.

Deep Climate said...

About 3C in 2006:

Jump to January 2010:

Key quote (from the post):

A corollary is that if we apply this interpretation to the climate sensitivity estimates, we find a "very likely" confidence interval of 2.1C - 4.4C. Now I'm sure some would argue that this interval is too narrow, but I would say it is pretty reasonable, though this is somewhat fortuitous as with such a small sample the endpoints are determined entirely by the outliers. The implied 70% confidence interval of 2.3C - 4.3C is more robust, and would be hard to criticise.

Links to the papers are in the posts.

Deep Climate said...

My take is that none of that means 1.5C lower bound is indefensible, but there should be some support cited or adduced.

It's not enough to merely say, as Michael Tobis put it in another context, "not the IPCC".

James Annan said...

Steve, what I meant was that she was not backing up her complaint with any substance. If she could come up with any coherent argument I'd consider it, but she seems to just be plucking claims out of thin air, and appears to be unaware of the work that has gone on in this area. I would be very surprised to hear that she was taking that quote from our paper to be authoritative on the subject. There is other evidence (not explicitly considered in that paper, which was focussing more on the theory and the sensitivity of results to assumptions) that undermines the possibility of such a low value.

James Annan said...

David's analysis looks reasonable to me, though the main problem with these sort of things is getting a good handle on the uncertainties. Omitting the other forcings (esp aerosols) is one problem and the 1-decade delay is an over-simplification. But it's in the right ballpark. Others have done somewhat similar statistical analysis in the past, eg Tol and de Vos, 1998.

I don't know what this is based on:

"The OGTR for 2xCO2 of 2.28 K roughly corresponds to a Charney equilibrium climate sensitivity (ECS) of about 3.3 K, by one rule of thumb."

RB said...

With regards to sensitivity, particularly with regards to Lindzen's hypothesis of negative feedback, would it be fair to say that the long-tail in the pdf skewed towards the high temperatures itself is evidence of positive feedback (my interpretation of Roe and Baker 2007)? Both Royer's analysis of the last 400 million years and your paper show such a skewed distribution to apply. If so, why isn't anybody applying this argument to at least settle the positive/negative feedback debate?

James Annan said...

RB, no I don't think so - the tail is long but thin in most analyses. If we consider sensitivity as


where DT is the no-feedback sensitivity and f is the unknown feedbacks, then any symmetric distribution centred on zero for f will still leave the 50th percentile at DT, but the right hand tail will be longer and thinner than the left.

RB said...

Thanks - let me reframe my question as follows, if instead we had sensitivity = dT/(1+f) would we instead have had a long-tail to the left?
Second question - As I understand it, Roe/Baker seem to suggest the possibility of high sensitivity while your publication assigns a very low probability (or practically rules out) very high sensitivity. Out in the blog-world, I was pointed towards a recent publication which challenges Roe/Baker. Am I correct in saying that your result ruling out high sensitivity is consistent with this paper and do you agree with their statement about the flaw lying in the linearity assumptions for the feedback system? Lubos Motl in the comments section seems to find linearity a good assumption for the feedback system, practically speaking. So, what wou you think are the implications of Zaliapin/Ghil?
Thanks in advance ...

David B. Benson said...

James Annan --- One decade delay is certainly a simplification but see no reason to see it as "over" simplified.

The rule of thumb is that TCR/ECS is about 2/3 (for at least one climate model but I'm under the impression that the ratio is fairly nearly constant across models.

As for no aerosols and whatnot, I have taken Gavin Schmidt's (repeated) comments to the effect that all other forcings net to zero, leaving only CO2 standing alone. There is a somewhat similar statement in the IPCC AR4 WG1 report, I believe.

As for uncertainties, RMS=0.023 K and R^2=0.991.

Anyway, thanks for the references.

David B. Benson said...

Tol, R.S.J. and A.F. de Vos (1998), ‘A Bayesian Statistical Analysis of the Enhanced Greenhouse Effect’, Climatic Change, 38, 87-112
was enlightening. I noted with particular interest their use of a 20 year lag for the effect of CO2 on temperature. They justify this as giving best results so I suppose I ought to try that as well.

Incidently, that paper also makes it difficult to reconcile the conclusions with a low climate sensitivity.

Steve Bloom said...

I went back and carefully reviewed the thread, and to set the recortd straight regarding what Judy said about sensitivity:

1) She didn't question the upper part of the range. (Note that I had this wrong above.)

2) She did clearly say that not enough of a case had been made for 1.5C as a lower bound.

3) In discussing K&H's 2C lower bound, she referred to additional evidence she said they had not considered, but didn't say what that evidence was.

4) She said that confidence in the lower limit would need to be justified in terms of the 20th century record.

On that last point, may I suggest that I detect the faint sound of a goalpost being moved?

As I noted above, her implication that K&H somehow refutes recent Pliocene evidence for higher sensitivity seems to result from unfamiliarity with that evidence.

Steve Bloom said...

So, David, when will you be prepared to place a bet on your results? :)

James Annan said...

RB, (1) No, so long as f has some reasonably symmetrical shape then the sensitivity will have a long tail because when the denominator is small, it gets very large (maybe unbounded) whereas the left hand end is always bounded by 0 and thus compressed.

(2) I did spot that Zaliapin/Ghil paper but have not looked carefully at it. I suspect the discrepancy may be definitional, the RB paper was not really doing anything different to what is standard in the field, though I do object to some details of it. So AIUI my objections are not the same as ZG.

James Annan said...

David, I'm not saying the assumptions/approximations are unreasonable - quite the reverse, they do pretty much represent our best estimates - but they do brush a whole lot of uncertainties under the carpet. If the ocean heat uptake was larger, and the negative aerosol forcing was stronger then you would need a much larger sensitivity to explain the observed warming. Conversely, a low ocean heat uptake and weak aerosols imply a somewhat lower sensitivity (though not as much lower as the high end may be higher). So although you can get a good ballpark estimate, it is hard to use such a method to get a rigorous uncertainty bound.

David B. Benson said...

James Annan --- Aha. But I'm not after an estimate of climate sensitivity, just the observed transient response to date.

Steve Bloom --- First I'm going to redo the program to use a two decade delay, as done in Tol & DeVos.

David B. Benson said...

I'm using decadal averages so it turns out that a one decade delay in applying the lnCO2 does better than a two decade delay, enough so that I won't switch.

Carl C said...

I use to follow her apologetics on Climate Audit -- I always just assumed since she teaches at my alma mater (Georgia Tech), which is basically a right-wing wet-dream, that she hears so much from the Faux News types around her, she sort of got warped by that. It sort of happened to me upon my return to the US and then when "climategate" broke! ;-)

PS - my worst memory of how uber-right-wing GT was when they showed Apocalypse Now and the geeks would cheer every (what was supposed to be) sarcastic line and everytime a "gook" got wasted....