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A scholarly rejoinder to the Economist article 

Dana Nuccitelli & Michael Mann have posted a response to the Economist story on climate scientists' assessment of the performance of surface-temperature models. I found it very interesting and educational -- and also heartening.

The response is critical. N&M think the studies the Economist article reports on, and the article's own characterization of the state of the scientific debate, are wrong.

But from start to end, N&M engage the Economist article's sources -- studies by climate scientists engaged in assessing the performance of forecasting models over the last decade -- in a scholarly way focused on facts and evidence.  Actually one of the articles that N&M rely on -- a paper in Journal of Geophysical Research suggesting that temperatures may have been moderated by greater deep-ocean absorption of carbon  -- was featured prominently in the Economist article, which also reported on the theory that volcanic eruptions might also have contributed, another N&M point.

This is all in the nature of classic "conjecture & refutation"--the signature form of intellectual exchange in science, in which knowledge is advanced by spirited interrogation of alternative evidence-grounded inferences. It's a testament to the skill of the Economist author as a science journalist (whether or not the 2500-word story "got it right" in every detail or matter of emphasis) that in the course of describing such an exchange among scientists he or she ended up creating a modest example of the same, and thus a testament, too, to the skill & public spirit of N&M that they responded as they did, enabling curious and reflective citizens to form an understanding of a complex scientific issue.

Estimating  the impact of the Economist article on the "science communication environment"  is open to a degree of uncertainty even larger than that surrounding the impact of CO2 emissions on global surface temperatures. 

But my own "model" (one that is constantly & w/o embarrassment being calibrated on the basis of any discrepancy between prediction & observation) forecasts a better less toxic, reaction when thoughtful critics respond with earnest, empirics-grounded counterpoints (as here) rather than with charged, culturally evocative denunciations.

The former approach genuinely enlightens the small fraction of the population actually trying to understand the issues (who of course will w/ curiosity and an open mind read & consider responses offered in the same spirit). The latter doesn't; it only adds to the already abundant stock of antagonistic cultural resonances that polarize the remainder of the population, which is tuned in only to the "us-them" signal being transmitted by  the climate change debate.

Amplifying that signal is the one clear mistake for any communicator who wants to promote constructive engagement with climate science. 

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Reader Comments (9)

The former approach genuinely enlightens the small tiny fraction of the population actually trying to understand the issues (who of course will w/ curiosity and an open mind read & consider responses offered in the same spirit). The latter doesn't; it only adds to the already abundant stock of antagonistic cultural resonances that polarize the remainder of the population, which is tuned in only to the "us-them" signal being transmitted by the climate change debate.

My take as a matter of scale, the impact of the former approach is basically negligible. Many people are basically indifferent - unless there has been some kind of proximal weather event that may or may not be attributable to climate change. They are not particularly engaged

That group can be enlarged by people who aren't indifferent, but who lack the time or the skills or the confidence to assimilate detailed analysis - and thus people who fit into that category care, but are minimally engaged

Then there are those who care, largely, because of the antagonistic cultural resonances. They are basically indifferent to the form of the science communication. There is nothing that Nuccitelli & Michael Mann could write that would result in responses that are easily predictable by virtue of the political, cultural, personal, ideological, or psychological identifications of their readers.

I can't imagine that any more than a miniscule number of people would fall through the cracks of those categories.

But my own "model" (one that is constantly & w/o embarrassment being calibrated on the basis of the discrepancy between prediction & observation) forecasts a better less toxic, reaction when thoughtful critics respond calmly with facts (as here) rather than with charged, culturally evocative denunciations.

I would love to see a controlled pre-test/post-test study (assessing views on climate change before and after this article was introduced) of this - with a randomly collected sample. My guess is that the toxicity of the reactions would be essentially unchanged. I'd bet that even a sample collection process designed to select subjects who were genuinely trying to understand the issues would register little change pre-test/post-test.

But that would be the control group. The next group with be one that was previously given a workshop, utilizing a meta-cognition-based instructional methodology, that focuses explicitly at the impact of cultural cognition in how we reason.

April 12, 2013 | Unregistered CommenterJoshua

I agree that the N&M article is less abrasive than many of their previous communications on climate science. That's certainly a positive.

There are a couple of odd points in the content, that I suspect might irritate those already aware of the background. They say "The claim was primarily supported by a single as-yet unpublished article by a group in Norway," which isn't true. It's based on a number of studies, several of which the Economist article mentioned, and there are more that they didn't cover.

They also say "It is unfortunate that none of these studies and findings, each of which conflict with the dominant narrative of The Economist piece, were cited or discussed beyond a brief mention." which besides seeming a peculiar construction - they didn't talk about the studies they mentioned? - is exactly the complaint sceptics make about the mainstream surveys, which rarely pay much attention to the conflicting observations. You can't have it both ways - either you're expected to address both sides in every article or you're not.

They are correct in observing that observations don't tightly constrain sensitivity, and that seeing the addition of a decade of data changing the estimate so dramatically indicates an issue with this approach. What it doesn't do is show whether it was the earlier, high estimates that were in error, or the later low ones.

They then mention three studies. The first, not yet published (although accepted for publication), is a comment about a different approach for estimating sensitivity with models, and argues that models underestimate natural variability which can give a misleading impression of high (if the noise goes up) or low (if it goes down) sensitivity. It therefore offers no support to N&M's contention that the new sensitivity estimate is low rather than the earlier ones being high. Not only that, but the Economist article discusses the findings that natural variability estimates being low high may have thrown off the sensitivity estimates.

The second reports new observations of aerosols since 2000 where they conclude that volcanoes and not people are responsible for the change in sulphur dioxide particles. They don't appear to be saying that more warming is being offset. The Economist article does also mention the possibility, but notes that the IPCC estimates of aerosol forcing have gone the other way, which M&N don't address.

The third is a Trenberth study that observes deep ocean warming (the measurements are uncertain and disputed) and claim without evidence that this heat is coming from greenhouse warming, rather than any other source (e.g. El Nino). It is, in any case, not relevant, since climate sensitivity is about the surface temperature. If sensitivity is lower than thought because some of it goes into the deep ocean, it's still lower than thought. And the Economist article does discuss Trenberth's ocean heat results, even showing a graph.

So none of them actually refute the point being made by the Economist article, or explain why climate sensitivity estimates are subject to such variability. All of them are issues that the Economist article covered. N&M's complaint is therefore only that they haven't paid enough attention (i.e. all of it) to the studies on their side of the fence. Yes, it's polite and scholarly, but it's not a convincing refutation.

April 12, 2013 | Unregistered CommenterNiV

In addition to NiV's comment, one problem with talking about deep ocean is that it changes the discussion to enthalpy. As NiV mentions an enthalpy balance is controversial. One of the controversies wrt CS is that we have only a few years of data for enthalpy that are considered as even close to correct. But such a short time line and the use of non independent model data generation, the actual data are sparse, means that it is unusable for the claims one way or the other. Besides, as NIV points out, using this means that not only will the crossover from adaptation to mitigation should occur hundreds of years in the future, but that it means that the short term natural variation may not be that at all. A case one way or the other has not been proposed nor vetted.

In one respect, N&M do a disservice. Not only are there several studies that have low sensitivity as most probable, almost all studies have low sensitivity. The typical span in AR4 is from about 1.5C to 6C due to the large uncertainties. Thus the only item of note is that the studies with a most probable low CS have a low versus a high CS. With high uncertainty, the large number of assumptions whether using modern data or paleo, and the number of assumptions and simplifications to get from the derivation to the actual working equations, the range of CS should be broad, or as in this study, variable with respect to number of observations.

This is not the fault of any authors that have done the studies. However, one cannot be so generous with N&M since the studies and their problems are well known, but no mention in the article. This makes the piece just another spitwad in the food fight, and another missed opportunity.

April 13, 2013 | Unregistered CommenterJohn F. Pittman

N&M leave off the portion of the graphic that highlights how poor some of the data used actualy is. As such, the N&M article becomes misleading. I also note that the actual study N&M relies on for the graph is not linked, though others, such as the activist blog Real Climate are.

See below for a link to the complete graphic, Fig. 3, that N&M truncates without notice or linking.

Note the number of studies that have large uncertainties, are poorly understood, very few studies or conflicting, unclear, cannot be quantified, ect.

It does seems strange where N&M berate the authors of the E article for using current studies and data and not using the older study that N&M prefer.

April 13, 2013 | Unregistered CommenterEd Forbes

Well put as usual. In the area of GMOs I've been attracting 5-10 inquires a week that want more real information. A lot of this comes from scientific, evidence-based discussion and openness to help. Using a real name and offering an email helps too. It takes a lot of time to answer this stuff, but good in the context of enhancing public understanding.

However, sometimes it does feel good to lay into the unteachable. I'm guilty of not always taking the high road, but I'm passionate about science. Sometimes I make the mistake of getting out the sledge hammer when I need to be gentle. It sure feels good though.

April 13, 2013 | Unregistered CommenterKevin Folta

It is not true to assert that "almost all studies have low sensitivity" - an assertion like that imples there is agreemetn on what "low" means. Citation of a range of data would be more useful, rather than using a post praising the tone of the N&M article to lower the tone of the ensuing exchange ("spitwad" etc).

I would prefer to emphasise where N&M agree with the Economist:

"Despite all the work on sensitivity, no one really knows how the climate would react if temperatures rose by as much as 4°C. Hardly reassuring."


Given that it will take a significant effort to avoid doubling the amount of carbon dioxide in the atmosphere, from a policy perspective arguments about the precise climate sensitivity are somewhat irrelevant. Even at the lower end of the estimated sensitivity range, the projected impacts of climate change are likely to be devastating to human civilisation and our environment.

April 16, 2013 | Unregistered Commentertoby

Late, but still pertinent, here's Judith Curry's own scholarly rejoinder, including Mann/Nucitelli, the Economist, and a variety of other papers on both sides of the climate sensitivity issue -- her synthesis:

Mann and Nuccitelli state:

"When the collective information from all of these independent sources of information is combined, climate scientists indeed find evidence for a climate sensitivity that is very close to the canonical 3°C estimate. That estimate still remains the scientific consensus, and current generation climate models — which tend to cluster in their climate sensitivity values around this estimate — remain our best tools for projecting future climate change and its potential impacts."

The Economist article stated:

"If climate scientists were credit-rating agencies, climate sensitivity would be on negative watch. But it would not yet be downgraded."

The combination of the articles by Schlesinger, Lewis, and Masters (not mentioned in the Economist article) add substantial weight to the negative watch.

In support of estimates on the high end, we have the Fasullo and Trenberth paper, which in my mind is refuted by the combination of the Olson et al., Tung and Zhou, and Klocke et al. papers. If a climate model under represents the multidecadal modes of climate variability yet agrees well with observations during a period of warming, then it is to be inferred that the climate model sensitivity is too high.

That leaves Jim Hansen’s as yet unpublished paper among the recent research that provides support for sensitivity on the high end.

On the RealClimate thread, Gavin made the following statement:

"In the meantime, the ‘meta-uncertainty’ across the methods remains stubbornly high with support for both relatively low numbers around 2ºC and higher ones around 4ºC, so that is likely to remain the consensus range."

In weighing the new evidence, especially improvements in the methodology of sensitivity analysis, it is becoming increasing difficult not to downgrade the estimates of climate sensitivity.

And finally, it is a major coup for the freelance/citizen climate scientist movement to see Nic Lewis and Troy masters publish influential papers on this topic in leading journals.

Should indicate, if nothing else, that debate over this significant point continues, and that climate ideologues committed to heightening alarm in order to achieve political (and these days often financial) ends indeed have cause for concern.

April 18, 2013 | Unregistered CommenterLarry

toby, I think I understand your point, but then you did not actually engage that it was N&M who wrote the article, and their responsibilities to meet your criteria, so I am not sure.

You state that there is some implied, on my part, agreement as to what low means, and state I need citation. Funny that N&M did not offer a citation for me to compare or contrast about that 3C. Thank you for adding another "spitball" to their account for the reasons you stated. My response was a short comment and not a published article. N&M must be worse than I thought. Please inform us as how your conversation with N&M go in this matter.

Myself, I use AR4 where it is agreed that CS cannot be below 1C by most who study CS. And agreement as you use it is a strawman, since the articles are about disagreement. So using most without citation is equitable to N&M using 3C without citation. I would assume it was the study and graphs they included.

Note N&M had the chance as I stated, and had a chance to include your criteria for assertions, wrote the article and did not. However, they included a study with graphs where you can see there is agreement by most of the graphs, it cannot be 1C or less, and that by most of the graphs 1.5C, or so, is low probability but significant.

"Even at the lower end of the estimated sensitivity range, the projected impacts of climate change are likely to be devastating to human civilisation and our environment." At the lower end of what is shown in the graphs, according to AR4, we would expect a net benefit, and the human civilization is doing quite fine already. Perhaps N&M did not consider that the very likely estimate in the graph included such low CS. I count 6 of 9 at 1.5C or less as very likely. And one of the three has a significant chance of 1.5C or less that did not make the very likely for some reason.

April 22, 2013 | Unregistered CommenterJohn F. Pittman


as soon as you cite work by an unscrupulous zealot like Dana Nuccitelli approvingly, and go so far as to suggest he's a scientist (which is logically unbelievable), you forfeit the trust of many skeptics and undo much of what you've done to detoxify the debate. A quick background check on Nuccitelli's character would have prevented this "cultural faux pas."

You didn't even need to google him, you could have just asked a skeptic. Many of us still remember the defamatory "review" of The Hockey Stick Illusion Dana posted on Amazon. I'd link you to it, but Amazon took it down when it became undeniably clear that Dana hadn't even read the book he was slandering. Dana was clearly embarrassed, on a strategic level, for being caught out, but I don't remember him showing any actual contrition, any moral comprehension that people shouldn't do things like that to other people; he didn't retract and apologise to the author; but then, why would he? We're just denialist scum to him. And a fake book review is nothing; as Lewandowsky has argued, it's OK to lie to deniers, steal constitutionally-protected private information from us, and circulate forged documents that appear to implicate us in a conspiracy against science... you know, for the "public good."

(When people say "Feynman must be spinning in his grave," I'm pretty sure they're alluding to the fact that integrity and probity are no longer prerequisites for a career in "science.")

The sooner you start asking some hard, and perhaps culturally-uncongenial, questions about the kind of crowd you've fallen in with, Dan, the better. For your research, for your conscience and for the health of the climate conversation in general.

September 10, 2013 | Unregistered CommenterBrad Keyes

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