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What do climate scientists think?

Filed under: — gavin @ 24 June 2010 - (Español)

by Gavin and Eric.

… and why does it matter?

There is a lot of discussion this week about a new paper in PNAS (Anderegg et al, 2010) that tries to assess the credibility of scientists who have made public declarations about policy directions. This come from a long tradition of papers (and drafts) where people have tried to assess the state of the ‘scientific consensus’ (Oreskes, Brown et al, Bray and von Storch, Doran and Zimmerman etc.). What has bedevilled all these attempts is that since it is very difficult to get scientists to respond to direct questions (response rates for surveys are pitiful), proxy data of some sort or another are often used that may or may not be useful for the specifics of the ‘consensus’ being tested (which itself is often not clearly defined). Is the test based on agreeing with every word in the IPCC report? Or just the basic science elements? Does it mean adhering to a specific policy option? Or merely stating that ‘something’ should be done about emissions? Related issues arise from mis-specified or ambiguous survey questions, and from the obvious fact that opinions about climate in general are quite varied and sometimes can’t easily be placed in neatly labelled boxes.

Given these methodological issues (and there are others), why do people bother?

The answer lies squarely in the nature of the public ‘debate’ on climate. For decades, one of the main tools in the arsenal of those seeking to prevent actions to reduce emissions has been to declare the that the science is too uncertain to justify anything. To that end, folks like Fred Singer, Art Robinson, the Cato Institute and the ‘Friends’ of Science have periodically organised letters and petitions to indicate (or imply) that ‘very important scientists’ disagree with Kyoto, or the Earth Summit or Copenhagen or the IPCC etc. These are clearly attempts at ‘arguments from authority’, and like most such attempts, are fallacious and, indeed, misleading.

They are misleading because as anyone with any familiarity with the field knows, the basic consensus is almost universally accepted. That is, the planet is warming, that human activities are contributing to the greenhouse gases in the atmosphere (chiefly, but not exclusively CO2), that these changes are playing a big role in the current warming, and thus, further increases in the levels of GHGs in the atmosphere are very likely to cause further warming which could have serious impacts. You can go to any standard meeting or workshop, browse the abstracts, look at any assessment, ask any of the National Academies etc. and receive the same answer. There are certainly disputes about more detailed or specific issues (as there is in any scientific field), and lots of research continues to improve our quantitative understanding of the system, but the basic issues (as outlined above) are very widely (though not universally) accepted.

It is in response to these attempts to portray the scientific community as fractured and in disagreement, that many people have tried to find quantitative ways to assess the degree of consensus among scientists on the science and, as with this new paper, the degree of credibility and expertise among the signers of various letters advocating policies.

It is completely legitimate to examine the credentials of people making public statements (on any side of any issue) – especially if they make a claim to scientific expertise. It does make a difference if medical advice is being given by a quack or the Surgeon General. The database that Jim Prall has assembled allows anyone to look this expertise up – and since any new source of information is useful, we think this can be generally supported. Prall’s database has a number of issues of course, most of them minor but some which might be considered more problematic: it relies on citation statistics, which have well-known problems (though mostly across fields rather than within them), it uses Google Scholar rather than the standard (ISI) citation index, and there are almost certainly some confusions between people with similar names. Different methodologies could be tried – ranking via h-index perhaps – but the as long as small differences are not blown out of proportion, the rankings he comes up with appear reasonable.

So it is now possible to estimate an expertise level associated with any of the various lists and letters that are out there. Note that it is worth distinguishing between letters that have been voluntarily signed and lists that have been gathered with nothing but political point scoring in mind (the Inhofe/Morano list was egregious in its cherry picking of quotes in order to build up its numbers and can’t be relied on as an accurate reflection of peoples opinions in any way, and similarly contributing to RealClimate is not a statement about policy preferences!). Additionally, it isn’t always clear that every signatory of each letter really believes every point in the statement. For instance, does Lindzen really believe that attribution is impossible unless current changes exceed all known natural variations (implying that nothing could be said unless we got colder than Snowball Earth or warmer than the Cretaceous or sea level rose more than 120 meters….)? We doubt it. But as tests of political preferences, these letters are probably valid indicators.

So, do the climate scientists who have publicly declared that they are ‘convinced of the evidence’ that emission policies are required have more credentials and expertise than the signers of statements declaring the opposite? Yes. That doesn’t demonstrate who’s policy prescription is correct of course, and it remains a viable (if somewhat uncommon) position to acknowledge that despite most climate scientists agreeing that there is a problem, one still might not want to do anything about emissions. Does making a list of signers of public statements, or authors of the IPCC reports, constitute a ‘delegitimization’ of their views? Not in the slightest. If someone’s views are widely discounted, it is most likely because of what they have said, not who they sign letters with.

However, any attempt to use political opinions (as opposed to scientific merit) to affect funding, influence academic hiring, launch investigations, or personally harass scientists has no place in a free society – from whichever direction that comes. In this context, we note that once the categorization goes beyond a self-declared policy position, one is on very thin ice because the danger of ‘guilt by association’. For instance, one of us (Eric) feels more strongly that some of Prall’s classifications in his dataset cross a line (for more on Eric’s view, see his comments at Dotearth).

But will this paper add much to the ‘there [is/is not] a consensus’ argument? Doubtful. People are just too fond of it.

But there really is.

427 Responses to “What do climate scientists think?”

  1. 51
    dhogaza says:

    While I might agree that it is quite disingenuous of Pielke to complain here, but not in previous much more egregious cases, that doesn’t mean that he is wrong.

    It does, however, speak to morality and bias. Surely a paper that states “x% of real climate scientists support the mainstream view” is less injurious than what boil down to investigations with the filling of criminal charges as the intent?

    Pielke has had his chance to fight for truth, justice, and beauty and did not. Any criticism for him doing so now is fair subject for attack on the basis of bias, not the integrity of science.

    Right or wrong.

  2. 52
    Eli Rabett says:

    Rather curious that Roger did not see the Inhofe auto-da-fe list as a problem, indeed a blacklist, but rather a provocation from Rick Piltz who first pointed it out.

    Were Eli Roger, (Eli knows screens across the world are being wiped), he would merely point out that Jim Prall is not alone in serving up red meat for his partisan followers. Over at his blog, Roger Pielke Jr. focuses on the Anderegg paper to also use these scientists for his own partisan purposes. In his comments he adds a good deal of intensity to the issue, writing about “blacklists” and “possible loss of grants” This is just as over-the-top as the PNAS paper, and just as unhelpful — if Pielke’s concern is to improve the role of climate science in policy and politics


  3. 53
    dhogaza says:

    We are being asked to fund a multi-trillion dollar, civilization-changing, socio-political experiment without seeing evidence of predictability.

    In essence, no you’re not. You’re being asked to decide if the scientific argument is strong enough for you to change your behavior.

    Society won’t – I gave up on that several years ago.

    All I ask for is honesty – would you people be honest enough to say “I don’t care, full speed ahead!” rather than *pretending* the science is wrong so you don’t look like such selfish, short-term thinking, damn the future generations ignorants?

    Really, all that is needed for peace in the climate wars is for people like you to be honest and to say, “I don’t care! Bring it on!”.

    Rather than pretend that if the science is really true, you’d change your political stance. Because you won’t, even though the science is really true.

    Honesty, please.

  4. 54

    Gavin – You accept Hypothesis 2b. Thank you for answering clearly. Our EOS paper concluded otherwise, and it is informative to have a discussion by your readers of the three hypotheses on Real Climate. I look forward to reading them.

    [Response: Please do not put words into my mouth. First of all, I do not recognise your statements as hypotheses in any useful sense. Secondly, I see no contradiction in accepting that there are multiple sources of anthropogenic influences on climate (I think we will have over a dozen independent effects in the AR5 simulations we are doing), and acknowledging that because of the rate of the rise and the perturbation lifetime of CO2 emissions that they are the dominant issue moving forward. However that does not imply that only CO2 emission cuts are useful, and if you look at any of our recent policy-related work (Shindell et al, 2009; Unger et al, 2009), you will see a portfolio approach to calculating the impact of specific policies and sectors. See also this piece in Physics World. Thus neither 2a nor 2b properly encompass my views. Other forcings are neither negligible nor is CO2 just one issue among the rest. – gavin]

  5. 55
    Christopher Hogan says:

    I think you have to take a bigger picture view of this.

    I’m an economist, with no bona fides to comment on the science here. But here’s what I think I know, relevant to the economics of this.

    If bromine had been cheaper than chlorine, we’d all be dead by now.

    That’s not my original insight. Most HCFCs have HBFC analogs (e.g. Halon not Freon). HCFCs could, with appropriate economic incentives, largely have been HBFCs. Bromine compounds are roughly an order of magnitude more destructive of the ozone layer. If bromine had been cheaper than chlorine, it would have been used, and we’d have been dead before we figured out what was going on.

    So, we lucked out, on the ozone-layer thing. Just so happens, essentially arbitrarily, the economics lined up in our favor.

    Fossil-fuel energy is cheaper than the alternatives. By analogy, what can one say? Oops?

    There is no reason whatsoever that the economics of energy consumption should, by itself, align with the ultimate impact. There is no linkage unless we create one.

    So, where the chance alignment of economics and science saved us on HCFCs, it’s going to kill us on fossil fuels.

    As a species, we are large enough that we, in effect, roll dice for the planet. Throw them enough times, heedlessly, and we will eventually be ruined.

    The only thing that’s going to work is making fossil fuels more expensive than alternative sources of energy. And if that reduces our current standard of living, so be it.

  6. 56
    Patrick 027 says:

    Re 48 Edward A. Barkley
    We’ve learned that you can say anything you want with statistics.

    Okay, so in order to be percieved as honest, we are no longer allowed to use math?

    Now, making predictions that can be measured…that’s evidence worth writing a check for.
    Svante Arrhenius (sp?) quite some time ago
    Hansen in the 80s
    off the top of my head

    Right now, however, we are lead to believe that the complexity of the Earth’s climate is such that any type of short-term prediction is an ineffective measure, but simultaneiously, the center of a severe crisis.

    So you don’t understand unforced (internal) variability. Doesn’t mean others don’t. Look up difference between weather and climate. A climatic state includes the texture of internal variability, but the same texture can occur with different exact weather events. It’s a bit like comparing two lawns. Mowed the same, watered, fertilized, etc, they’d tend to look the same if you aren’t actually counting individual blades of grass. That’s like climate. For another analogy, consider severe weather watches. Are they completely bogus? They don’t predict hours in advance that an EF2 tornado will touch down at the corner of Elm and Rock street at 3:49 PM. Yet they can predict that there will be some severe weather in the general area, or at least more of it or more likely than at another day and time and place (the weather/climate distinction can (at least in analogy) be shifted on different timescales – for example, the exact timing and location of the landing of a snowflake may be a weather event while a blizzard may be like a climatic state (predictable at least minutes in advance). The present day arrangement of the continents is like a manifestation of mantle weather; a general pattern and rate of mantle convection would be like mantle climate.)

    Proving that C02 is a greenhouse gas and that man produces alot of it, falls far short of proving the climate models can be predictive.

    Good thing scientists have looked into the matter beyond those two items.


    No, you/we are not. The view we have is through a frosted glass window – we can’t know everything. But there are things that we do know, and we can act according to that. How much sense does it make to bet on an unlikely event, just because the more likely event is not 99.99 % certain? If you bet on the expected you’ll win more often. The bookie we’ve got is not going to reward the extra risk with greater payback. And with the good reason for expectations as they are, burden of proof should fall more heavily on the unexpected. (Note that short-term unpredictability is actually expected.) Farthermore, the uncertainties remaining in the consequences of an emissions-intensive path is itself cause for concern and a farther justification for increased mitigation – it is easier to adapt if we can plan for what we’re supposed to adapt to.

  7. 57
    MapleLeaf says:

    Dear Roger Jnr,

    You do not seem to understand why some (I am certainly not alone in that regard) have issues with your blog or your commentary on climate science. You are oftentimes ambiguous, and have made defamatory accusations against at least one three of the scientists who hosts this blog. I certainly do not recall you being as outraged/upset or outspoken about Inhofe as you are about this. IMO, your limited critique of Inhofe’s list of 17 is in stark contrast with your comments to date on the PNAS paper. For example, I do not consider you saying “So I think that it is just a bit of clown-like bluffing, serving up red meat for the partisans, but little else” to be a damning critique of Inhofe’s persecution of climate scientists.

    I do stand corrected on your stance on Cuccinelli. I retract that accusation and apologise.

    You could ignore Beck and Limbaugh, but it would not hurt to openly condemn their actions in a show of support for your colleagues. Silence can be understandably perceived by some as a quiet show of support. I’m interested to see you (hopefully) taking Morano to task for his vitriol and campaign of distortion and misinformation.

    I, of course, have no problem with the IPCC reports being as accurate and complete as is possible for such mammoth documents. I do have an issue with critique that is for the most part not constructive– and that is what I tend to associate your blog and pubic opines (such as on the BBC) with. To me at least, your critique leaves the distinct impression that you are of the opinion that the IPCC can do no right, with frequent focus on their shortcomings rathe than their strengths. If you think the IPCC has so many issues, then why do refuse to participate in this important process, contribute constructively and help improve it? I have a hypothesis there, but I’ll leave it at that.

  8. 58

    From] 2: [Response: Lindzen is often wrong, but he isn’t an idiot. – gavin]

    Yesss he is something else all right, I stand to be impressed by some accurate prediction he has made, his predictions have been always wrong (as far as I read), especially about the “cooling” we are suppose to bask in right now.
    He has a met chair without the power to make accurate predictions, MIT must be a special school…

    [Response: Whatever one may think of Lindzen he earned his position at MIT based on his brilliant (earlier) work. Please do not cast this sort of spurious aspersion on people.–eric]

  9. 59
    Chris Crawford says:

    I’ll take a moment to answer Mr. Barkley’s point in #48:


    Actually, Mr. Barkley, we’re making a multi-trillion dollar, civilization-changing social-political experiment already: the release of CO2 is changing the climate in ways that are likely going to cost us trillions of dollars. In other words, we’re ALREADY making the change that will cost us lots of money. The choice before us is not either:

    a. do nothing and pay nothing
    b. pay trillions to reduce CO2 emissions

    The choice is really this:

    a. do nothing and pay huge future costs.
    b. pay now to reduce future costs.

    I see it as a simple cost-benefit tradeoff. The information I read suggests that we can get ROIs of maybe 10% to 30% on measures to cut CO2 emissions in half by 2050.

  10. 60

    I would suggest to all contrarians to please explain Arctic sea ice demise, as it currently melts, as anything other than a validation of their opponents predictions. Sea ice is integrated weather, climate , in its purest form. What heat source other than AGW greenhouse gases are causing these greater melts ? …. I eagerly await an answer, which will never come, like a correct contrarian prediction..

  11. 61

    In my opinion, the impact of the PNAS paper is much like that of the hunter who accidently shot himself in the foot.

    With kind regards,
    Oliver K. Manuel
    Former NASA Principal
    Investigator for Apollo

  12. 62


    Eric, brilliant earlier work is irrelevant when present Lindzen prognostications are wrong. Is this the way of modern schools ? One makes a brilliant something, then it gives him or her the right to say anything? I am curious, this is after all what we are dealing with, a few well placed contrarians, literally getting 50% of the press or more about AGW. What else are we suppose to do with them? Send them flowers ? Ask them pretty please to stop?

    I am formal about the view that anyone with or without credentials has standing in climate science, when they are …… Right…… Let them fail or thrive on correct predictions. Let forums such as these expose the failures and teach the success stories…

  13. 63
    Peter says:

    #40 (Average Person)

    Q: Is there reasonable certainty that global climate change is occurring?
    A: Data in deep-sea cores demonstrates climate is capable of dramatic change, and it does not require human interference for that to occur. Instrumental record of last hundred years shows climate changes on many time scales.

    I think that what you mean to say is “yes”, but I’m not sure. I see no need to discuss whether a phenomenon is manmade or not if we can not first agree whether the phenomenon in question even exists. That’s why I put this question first. (Someone who answers “no” really doesn’t need to answer the rest of the questions.) It may be that the wording needs some help, though. I’m trying to ask if there is a consistent long-term trend in the climate data.

  14. 64
    Edward A. Barkley says:

    I was asked a few direct questions, so I will gladly follow-up my comment. I honestly thank you for including it in the blog. Eric: I was talking about the Scientific Method, so I cannot understand how an argument that predictability should trump consensus is nonsensical? If you are proposing we leave predictability out of the Scientific Method, please notify the public school system as soon as possible. :-). If my argument is nonsensical because predictability in complex systems is too difficult to factor into a computer simulation, then I suggest admitting the fallibility of Chaos Theory, and it’s role or nonroll in Global Climate Science, to those funding the research.

    Asbestos is a perfect example of my point. The first documented deaths due to asbestos exposure were in the early 1900’s. Asbestiosis was first declared a debilitating illness in both the US and the UK in the mid-20’s. It was designated as an excusable and serious work-related illness in the UK, US and across Europe before World War 2. The information wasn’t exactly “hidden by the asbestos industry” to those workers was it? We have very long term, hard evidence of why asbestos has a high-probability of causing cancer. That is why i don’t “breath deeply”.

    To those of you who deny you are asking the common man to fund a multi-trillion dollar experiment (may I call you “deniers?”):

    “The Obama Administration and the U.S. Department of Treasury says (regarding current proposed Cap and Trade Legislation) that the total in new taxes would be between $100 billion to $200 billion a year. At the upper end of the administration’s estimate, the cost per American household would be an extra $1,761 a year.”

    -CBS News

    “The authors have found that the constraints posed by the Lieberman-Warner cap-and-trade approach is equivalent to a constant (in percentage terms) consumption decrease of about 1% each year, continuing to 2050. Put another way, the cap-and-trade approach is the equivalent of a permanent tax increase for the average American household which would rise from $1,437 by 2015, to $1,979 in 2030, and $2,979 in 2050.”

    -from US News and World Report, March 2010

    You are most certainly asking me to fund the experiment: to the tune of $1700 per year from me personally (according the Obama Administrations own research).

    Dhogaza: When you ask why we won’t be honest and admit we just “don’t care” and won’t change our political positions “even though the science is really true”, I wonder why you won’t admit that this climate legislation is at best an uncertain and expensive shot-in-the-dark. I’ve never met any sensible, informed “skeptic” who believed the Earth hasn’t been warming, that humans don’t produce alot of C02, that C02 is not a GHG, or that man should simply ignore the environment and “do nothing” to improve it. Associating those types of facts with most “skeptics” is dishonest, political propaganda. I whole-heartedly support clean water/fresh air legislative efforts, reducing dependence on oil through funding of promising energy technologies, and reinstatement of the use of nitrogen-rich miracle fertilizer experimentation in the famine-stricken regions of Africa – that have, ironically, been attacked as potential global warming threats.

    According to my rough calculations, going by the Obama Administrations more conservative estimates, $1761/yr X (2050 – 2011) = $ 68,679.00 from my family personally. My 70 grand wants climate scientists to follow the Scientific Method and deliver SOME level of predictability. Forget climate versus weather. Narrow the focus. Let’s find which pieces of this puzzle have real validity. With that sum of money on the line, each one of us deserves proof.

    [Response: I’m not at all convinced that any of the policy options on the table in Washington make sense, economically or otherwise. But that’s a totally separate question from the reality of anthropogenic climate change. Don’t confuse them. If you don’t like the policy, fine, but don’t argue against it on the grounds that the science is wrong, because that’s a non-starter. You can make arguments on economic grounds, but then you shouldn’t be arguing with us at RealClimate, since we’re by no means economics experts. Go argue with Nicholas Stern.–eric]

  15. 65
    Gilles says:


    OK let’s do that first.

    Then by allowing more people to increase their standard of living through natural growth , we could choose to multiply again by a factor two the GDP and the CO2 consumption; with the same energy intensity. The net gain would be 2*(1+0.1 to 0.3) – A

    (this doesn’t need to be done AFTER the gain in efficiency of course, but it can be done without inconvenience DURING the improvement period, just by growing a few % more per year).

    where A is the (relative) climate cost of passing again from one half CO2 to the full CO2 production (retrieving the initial value).

    so net gain of the overall operation = 2.6 to 2.8 – A.

    it is > 1 if A < 1.6 to 1.8 , i.e. if the cost of passing from one half to the full CO2 production is less than 160 % to 180 % of the initial GDP.

    What is "the full" CO2 production? well I don't know exactly which is your baseline, but I don't expect we can reach more than 500 ppm before 2050. So reducing by one half would lead to 450 instead of 500 ppm; say.

    So finally the question is : is the cost A of passing from 450 to 500 ppm larger than 160 % to 180 % of initial GDP ?

    does an increase from 450 to 500 ppm cost more than that, and why exactly ?

    if nobody can insure it is the case, I think that all policymakers will invariably do the same choice – use the gain in efficiency to increase more GDP, not to reduce CO2 – just through simple cost-benefit trade-off.

  16. 66
    Ray Ladbury says:

    Roger, your hypotheses are not hypotheses in the scientific sense. A scientific hypothesis is a proposition that can be demonstrated or falsified with fairly straightforward evidence or experimentation. “CO2 is a greenhouse gas,” is an example. Your statements are really a combination of observations and attribution. It is an empirical fact that we are seeing warming outside of normal “natural” variability. That this would occur was a prediction of climate theory dating back 114 years, so the warming supports the consensus model of climate.

    I think the biggest problem I have with your approach–aside from your attacks on scientists–is your narrow focus on the issue of anthropogenic causation of the current warming. I think the focus should be on understanding climate–and unfortunately you can’t do that without a theory that predicts substantial warming due to anthropogenic CO2.

  17. 67

    AP 40: whether human emissions have a significant effect is entirely unknown

    BPL: To you. To the scientific community, the effect has been known for almost 200 years. Why don’t you pick up an introductory textbook on climatology, radiative transfer, or atmosphere physics, and actually read it? Better yet, work the problems.

  18. 68
    Ray Ladbury says:

    Edward Barkley,
    OK, let me get this straight. You state right up front that you don’t have a clue how science is done beyond what you learned in undergrad chemistry. You then demonstrate your ignorance by discounting the importance of scientific consensus and presenting a cartoon charicature of climate science and science in particular. And then you expect us to take your advice seriously?

    Climate science has a very impressive record of successful predictions.

    Ed, I only hope your health improves so that you can leave that bubble you’ve been living in. Ever hear of Peak Oil? Google it. Business as usual is not an option. Even independent of its implications for Earth’s climate, the energy infrastructure of human civilization must change. The easy petroleum is all gone–and as we can see looking out onto the Gulf, we’re having to go to extremes and take extreme risks to suck more of it out of the ground. Coal is at present plentiful, but will take us through at most another century. So the question is not whether we will spend trillions creating a new energy infrastructure. That is inevitable. The question is whether that new infrastructure will be sustainable or whether we’ll wreck our environment and then have to do it all over again in a century.

  19. 69

    EAB 48,

    Where did you get the idea that GCMs had no predictive ability? It’s stunningly wrong.

  20. 70
    Ray Ladbury says:

    It would appear that the contention of #40 is to prove that the Average Person is an ignoramus.

  21. 71

    Eli 53,

    What a wonderful post. Really makes a good point. Thanks.

  22. 72
    HotRod says:

    Genuinely confused here between science and policy.


    If I take the liberty of moving your apostrophe so it reads ‘convinced of the evidence that emission policies are required’, which I think is your sense, then it dangerously elides having ‘cred and exp’ in climate science with having ‘cred and ex’ in opining, even advising, on policy response.

    I can accept that climate scientists have ‘more credentials and expertise’ in climate science. I cannot accept that they have that in opining on emission policies.

    Emission policies get caught up in a whole new world of choice and impact. In the UK we have poured money into wind and now solar in an explicit attempt to get down our energy-generating CO2 emissions. The effects of that policy on our CO2, our GDP, how much CO2 emitting we are simply exporting, and the impact on global climate change, versus any number of counterfactuals, is simply not an area for climate scientists.

    Yes, I did read your next sentence, ‘That doesn’t demonstrate who’s (whose) policy prscription is correct of course….’, but even so this constant crossing of the line between science and policy, and the strong implication, even statement, that we must listen to climate scientists on policy, is just wrong.

    [Response: You are making a fair point, but it you’re missing a critical contextual fact. Many of the prominent (and not so prominent) ‘skeptics’ are advocating policy choices on the grounds that the mainstream scientific view of the physical science is wrong. (I do not believe that medical researchers should dictate health policy, but I sure as heck would not want to have anyone (whether they are a ‘policy expert’ or not) dictating health policy predicated on the grounds that HIV does not cause AIDS.) Furthermore you overstate your case when you say that “I cannot accept that [climate scientists] have [credentials] in opining on emission policies.” First off, they certainly do have the most expertise when it comes to “what is the likely impact of a given emission policy on CO2 concentrations and global mean temperature”? Indeed, they are by definition the only group with that expertise. Second, many climate scientists actually have also studied the policy end, professionally. You are assuming that among the experts in science, there are no experts in policy. But I suspect you are wrong. Indeed, I suspect that that if one were to take the same group of people studied by Anderegg et a., but evaluate them in terms of their credentials in the policy realm, there would still be a lopsided finding.–eric]

  23. 73

    WD 58,

    Lindzen is not incompetent by any means. He’s extremely bright. He’s just a shameless liar.

    In his peer-reviewed papers, he has to stick as close to the facts as he can. But in his public speeches he says things he knows damn well are false–global warming stopped in 1998; Mars is warming too and there are no SUVs there; it’s the sun, stupid!

    Doesn’t mean he’s an evil man at heart. I have no way to know. But he apparently does think it’s okay to lie in a good cause. He and I both disagree with Kant that’s it’s never right to lie, even to a murderer asking where his intended victim is. But I draw the line bounding times when it’s okay to lie much more narrowly than he does. I think most people do.

  24. 74

    A visit from Oliver Manuel! Cool!

    Dr. Manuel, I can’t begin to tell you how impressed I am by your thesis that the sun is made out of iron. Idiot that I am, I always swallowed the science Kool-Aid that said it was hydrogen, helium and a small admixture of metals in a hot plasma. And the idea that the core of our sun is a supernova remnant–brilliant! Who would have guessed that the sun used to be 4-40 times its present mass, lived an entire life as a main sequence blue giant, and finally wound up exploding–and then inexplicably posing as a main sequence type G2 star! THAT is original!

    Please comment here a lot more, and anywhere else on the web you can. I want people to become more familiar with your views!

    [Response: I appreciate that you want a little fun here, but all discussions of crank theories of solar processes are OT. – gavin]

  25. 75
    Anonymous Coward says:

    Unless I’ve missed something, you have misprepresented the mendacious piece Lindzen apparently signed. It doesn’t adress attribution directly but compares the satellite record with “natural” variations in the last 10’000 years. There’s no 120m there. If Lindzen is indeed proposing this comparison as a reasonable attribution test, I believe he would be discounting a lot of good science. But it wouldn’t be nearly as nuts as you claim.
    The word “natural” is very ambiguous out of context. It only breeds fuzzy thinking and confusion.

    [Response: The text reads: “Recent observations … are not evidence for abnormal climate change, for none of these changes has been shown to lie outside the bounds of known natural variability.” – this implies that nothing ‘abnormal’ (i.e. anthropogenic) can be assessed unless we surpass the bounds of ‘natural variability’. This is simply bogus, as the recent piece on attribution hopefully explains. – gavin]

  26. 76
    Geoff Wexler says:

    Re #28 Pete Best

    the BBC is forever (when it does discuss it) putting forward both arguments constantly in some kind of liberal act of a balanced view point

    It has often appeared rather worse than that. There is lots that could be said but it is slightly OT

    [I don’t include the BBC World Service which may be better and the BBC web site which is a bit different and may be more balanced]

    Take yesterday morning on Radio 4 ,about the Antarctic:

    This is one of the best series put out by Radio 4 and the programme was good. But did you notice that the topic of CO2 variation was not mentioned? This is part of a pattern of avoidance.

    Then there was the TV series by Brian Cox whose wife has said that she does not agree with the CO2 theory. It could have covered the topic of AGW but didn’t. It highlighted the role of water vapour in the greenhouse effect. That was before we had a coalition government in the UK. A fair compromise! Half way to Tyndall 1855!

    Then there was the “Climate Wars”. A compromise between weather and climate. How the presenter remembered how hot it was one year (shots of playing on the beach). And the so called ice age forecasts of the 1970’s.

    Much of the time the BBC removes the science and presents the subject as a set of opinions by rival priesthoods.

    I might welcome a balanced approach; it depends if it is done scientifically and by experts and without any of the usual misinformation.
    One example would be to balance the arguments that the world is warming with the opposite. Ditto with the rise and attribution of the rise in CO2 etc etc.

    But we don’t get that sort of balance. We get almost complete censorship of anything analytical. And now the BBC seems scared of touching the subject.

    Incidentally how about the balance of reporting of the Email hack at the CRU? Huge excited coverage last November, interviews with Morano, Inhofe et al. Then the first reports of the inquiries started to come in. Almost no coverage! A mention at lunch time but not in the evening, no details.

    What do we know for sure? That Channel 4 (a related UK Public Service broadcaster but relying on adverts) is denialist. The seniors spoke as if they really believed in the Swindle. Their idea of balance is to invite George Monbiot to discuss renewables. We don’t know what the seniors at the BBC think because they keep quiet.

  27. 77
    Ibrahim says:

    #60 Mr. Davidson

    I recommend this book from 1943 an especially page 470 onward.

    [edit ]


  28. 78

    What gets me is how the denialists argue both sides. They say there isn’t scientific consensus on AGW but dispute…

    …then they play the Galileo card and say consensus on AGW means it must be a hoax….

    I’d sure like to have my cake and eat it too.

  29. 79

    I highly respect the Team at RC and the scientists that post here but I am concerned that the tone is too muted regarding the dangerous path we are certainly on regarding the impact of climate change. I understand that a “good scientist” should be conservative and emphasize the uncertainties while trying to solve the riddles of climate change. I also understand that science is supposed to inform policy and not create policy but I agree with Dr. Hansen that we need to cross that line now before we look back and claim that scientists let us down by not shouting from the hilltops. What we say in private about the impacts needs to become more public.

    There is strong evidence that doubling CO2 to 560 ppm will result in a 3C warmer climate. Given population increases and rapid industrialization of China, India, and the developing world, it appears that 560 ppm will be reached around 2050, if not earlier. As I research the impacts of climate change, it is obvious to me that 3C is a nightmarish situation and I fear that number will not be the high point as we move toward 2100.

    What I do not understand is the people who post here and on their own blogs who claim to agree with the consensus and yet, instead of warning the public about the coming dangers, choose to vilify the IPCC, RC, and others. This behavior is essentially causing the public to be confused at a time when they need to take action.

    If you truly believe that 560 ppm is inevitable, you should stop wasting everybody’s time with crying foul over whose name appears on a list that has been public for years. Get off your high horses and start warning the public. To those that are not crying foul, please consider being a climate Paul Revere. “Climate change is coming, climate change is coming!”

    P.S. Climate models are very good all things considered.

    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    Global Warming: Man or Myth?
    My Global Warming Blog
    Twitter: AGW_Prof
    “Global Warming Fact of the Day” Facebook Group

  30. 80
    thingsbreak says:

    @33 eric:

    “that doesn’t mean that he is wrong”

    Eric, not to be a nag, but do you think you might address comment #7? There is no list of names in the paper, the SI, or the webpage linked in the SI. The data used in the paper were generated from publicly signed statements. Roger has repeatedly* claimed that there exists a list of names in the PNAS paper that constitutes a “black list”. This *is* wrong, and it’s something he knows is not true. I’m curious to hear if you actually read the paper, and if so where *you* read a list of names that prompted you to agree with Roger about this preposterous “black list”.


    *From his blog comments, well after it was pointed out that no such list existed in the paper:
    “By contrast the purpose of the PNAS list is to delegitmize a certain group simply by virtue of being on the list”

    “The problem with the PNAS black list”

    “And I would bet that many on the PNAS black list would also”

    [Response: In the supplementary information from the paper ( there is this link: At the bottom of that page, you click on “back to the main page” and you get here:

    One thing I wish to emphasize about this list is that I find it offensive not only because it lists ‘skeptics’, but also because it lists ‘activitists’. In short, I’m a commie because Anderegg et al. did a study, published in a leading journal, and said I am. –eric ]

    [I should add that I’m exaggerating here to make a point. Of course, Anderegg et al. didn’t call me anything. But I am listed as ‘activist’ on the web site. I reject any such labels.–eric]

  31. 81
    melty says:

    Complained to the BBC for its coverage if Anderegg et al. by Pallab Ghosh and his editor(s). Headline? “Climate credibility under review”. Perleeze.

  32. 82

    Mr. Prall needs to work a little harder on his list. For example it calls WIll Happer, number 6 on the list of evildoers and a very well known climate ‘skeptic’, a particle physicist. Will is an atomic/molecular physicist and in the National Academy for his work. And claiming molecular physics is not related to climate science is, well, odd.

    All in all, this paper, published under the rubric of ‘social science’ by a biologist, an engineer, a climate scientist and an MBA, is a pretty sad showing — not so much for the authors, but for PNAS, who are now publishing political rhetoric from unqualified amateurs as ‘social science’.

  33. 83

    Another thing I’ve noticed is how the denialists (consciously or unconsciously) think that policy determines the science. You get that in their arguments a lot. They’ll say “AGW is a hoax,” then next sentence, “the AGW-hoaxers are planning to impose a totalitarian dictatorship upon us.”

    They follow a policy-driven bogus science (or how many ways can a ostrich stick its head in the sand), when we should be following science-driven policies.

    First face the reality, then come up with solutions that will be as painless as possible — maybe even fun and profitable solutions. Or, be not afraid to face the science. The real alarmists and fear-mongers are the denialists.

  34. 84
    thingsbreak says:

    “At the bottom of that page, you click on “back to the main page” and…”


    I’m glad that we both agree that the Anderegg et al. paper does not in fact have any sort of list of names in it or the SI, much less a “black list”. Do you think you might want to revisit your statements that implied as much over at Dot Earth and Roger’s blog?

    If you disagree with the labels and methodology used to produce the Anderegg paper or the material that the paper drew upon, I think everyone’s open to discussing ways to do it differently. But to claim that this paper somehow put you on some sort of list *when it has no list* appears to be no more truthful than the “PNAS black list” lie that Roger is desperately shopping around. This statement “I’m a commie because Anderegg [sic] et al. … said I am” looks equally unjustifiable given the available evidence.

    Of course, it’s possible that I have misread the paper and supplementary material. I am always happy to admit an error. :)

    Thanks for the discussion.

    [Response: I’m sorry, but I think trying to separate the paper from the list on the web is disingenuous. I would like to see Anderegg and coauthors publicly disavow that list.–eric]

  35. 85
    SecularAnimist says:

    Len Ornstein wrote: ” … the predictions of the Club of Rome’s 1972, ‘The Limits to Growth’, that also have proven to have been somewhat premature.”

    Since that was copied-and-pasted from the apparently boilerplate comment you posted recently on another thread, I will respond with the same thing I said there.

    The Club of Rome’s Limits To Growth and the sequel Beyond The Limits did not make “predictions”. They set forth a range of possible scenarios, which is an entirely different thing.

    Have you ever actually read either book?

  36. 86
    thingsbreak says:

    @ eric

    “I’m sorry, but I think trying to separate the paper from the list on the web is disingenuous.”

    I can understand that point of view. My own is utilitarian. Of the people who read the paper, the number who will read the SI will be a small fraction. Of those, the ones that click through to the linked web page will be smaller still. Of those, the ones who navigate back to the main page will be smaller still, etc.

    The idea that- unprovoked by rampant accusations of McCarthyism and Stasi-like tactics- funding agencies were going to drill through several layers of material distant from the paper proper, seize upon the breakdown of lists, and use them to create a “black list” seems quite absurd to me, especially given that were they so inclined, it would be far simpler and less time consuming for them to draw from the same source material that Jim Prall used in the first place.

    The disingenuousness appears from my perspective to stem from the conflation of the website with the paper, and the idea that the website itself represented the first public creation of a list rather than a cataloging of publicly available material and statements.

  37. 87

    Eric, you should be wearing “activist” as a bad of courage. Just doing the science is not good enough anymore with the stakes so high. The world needs more scientist-activists because the message is not getting out with just “science”.

    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    Global Warming: Man or Myth?
    My Global Warming Blog
    Twitter: AGW_Prof
    “Global Warming Fact of the Day” Facebook Group

  38. 88
    Chris Crawford says:

    Gilles in #64 looks more closely at the cost-benefit tradeoff, but makes an assumption that undermines his calculation: that “ROI” refers to “net return on investment” instead of “annual return on investment”. I should have made it clear that I was referring to annual return on investment, but in fact the annual ROI is far and away the more common usage. After all, a net ROI of 50% over 100 years is lousy, while the same net ROI over one year is fabulous. That’s why it’s more useful to think in terms of annual ROI, which is what I was doing.

    There’s no question that the costs imposed by continuing climate change will be enormous. To take a simple example, the city of Miami lies at an average elevation of only about 2 meters above sea level. Should sea level rise by 1 meter, a value considered likely within this century, then much of the city will become uninhabitable. The net value of the infrastructure of Miami — buildings, roads, utility structures, and so forth — is several trillion dollars, IIRC. Somewhat smaller costs would arise for most port cities around the world (most are at average elevations higher than Miami’s). Add up all those costs and we’re talking hundreds of trillions of dollars just for dealing with sea level rise. This doesn’t include costs arising from changes in precipitation patterns, effects on agriculture, and so forth.

    Now we turn to the costs of CO2 reduction. It is often claimed, without any justification whatsoever, that carbon taxes or cap and trade schemes will cost trillions of dollars. However, the economic analyses that have been carried out yield far lower results, generally in the tens to hundreds of billions of dollars per year. Even generously discounting these values, we still end up with net annual economic benefits of perhaps 10% to 30% of the investment we make in reducing CO2 emissions.

    These numbers are, of course, fraught with uncertainty. They are based on calculations that make manifold assumptions, any one of which, if far off the mark, could dramatically alter the results. Nevertheless, the notion of making large financial decisions in an uncertain context is in no wise exotic — it’s what business executives do every day. When an executive decides to invest billions in a mine in some Third World country, he’s making huge assumptions about the political stability of that country — guess that cannot possibly be justified with any hard numbers. When an oil company decides to invest billions in drilling a deep-sea well, they’re making huge assumptions about the likelihood of actually striking oil — guesses rife with uncertainty. When a Hollywood studio decide to invest hundreds of millions of dollars in a major movie, they have no way of knowing with any certainty whether it will succeed or fail.

    In all of these cases, business people rely on much less than a straightforward calculation. They play a hunch. They put together everything they know and make a decision that they could never justify in strict logical terms. That’s how business is done. Businessmen who heed the recommendations of denialists would quickly go out of business; there are no sure things in the real world.

    I suggest that we make our political decision on this question using the same methodology used by successful businesspeople: assemble a group of the most experienced people in the relevant fields, give them resources to collect and analyze the available information, let them discuss and debate the problem, and then heed their advice. We have already done this a number of times: with the National Academy of Science, the IPCC, the Stern Report, and many other cases. They all come back with the same advice: we need to reduce CO2 emissions.

    So why are we behaving like loser businesspeople instead of winner businesspeople?

  39. 89
    Eli Rabett says:

    Given current interest rates, the ROI on any basis is a lot higher. (And if you object that the rates are uncannily low these days go look at the Japanese rates for the last twenty years.

  40. 90
    Barry Woods says:

    If realclimate coudld link to luke wamer blogs, it might reduce the criticism of advocatcy..

    ‘climate Sicence for climate scientists’

    as they link to desmog blog and geaorge monbiot,
    but not climate audit, pielke’s or say lucia’s blackboard..
    george monbiot is not a scientist, he is a journalist!

    So it does look like advocacy to a new observer
    If they cuold bring themselve to do this it would be a gesture of goodwill..

    Having a link to ‘how to talk to Global Warming Sceptic’ vetted and endorsed by professionals at RealClimate, reflects, to an observer badly on RealClimate..

    So, constructive advice, drop the links to the more ‘flag waving’ type advocacy sites, include some ‘respected’ alternative views, it would help Realclimate stop being ‘perceived’ as an advocacy site rather than a science site…

    [Response: Being listed on our blogroll does not constitute endorsement. In general, the sites we do list — whether they are run by scientists or not — tend to get the science right much of the time, and hence are consistent with our mission. Being not-listed could mean that a) we haven’t heard of the site, b) that it is uninteresting or unimportant, or c) that we consider it dishonest or disingenuous with respect to the science. Pielke Jr, Blackboard, and ClimateAudit all fall squarely into the latter category.–eric]

  41. 91
    pete best says:

    RE #76. The Great Global Warmign Swindle was part of a series of three programmes started by George Monbiot which painted a picture of our lack of energy efficiency.

    I was more thinking Radio 5 live myself which when it does discuss it its not funny and not very good. Radio 4, hmmmmm who knows on that one and some of the climate programs have been OK.

  42. 92
    J says:

    The study’s conclusions have a logic problem. As summarized by Slate:

    “If skeptics are being shut out of journals, their publication counts would go down, which would produce precisely the results shown in the PNAS paper.”

    [Response: There is, however, no evidence that ‘skeptics’ are being shut out of journals. There is indeed much evidence to the contrary. This is a canard.

    What Slate actually says is that “The authors make no attempt to tease out the extent to which prejudice, rather than a disparity in expertise, can explain why so few skeptics rank among the top climate authors.” That appears to be true, but Slate overstates its importance. A better point they make is the following (but do take note of the sentence in bold).

    “The analysis of papers from diverse fields seems to have distorted the results. Take the case of Freeman Dyson, who ranks high on the list of climate skeptics. …. His top paper, on particle physics, had 749 citations when the authors checked. That’s quite a few, but not as many as were received by several dozen climate scientists for their top papers. Dyson is by all indications badly wrong when it comes to climate change. But few scientists in any field would agree that his top work is less impressive than that of 40 climate researchers, most of whom are far more obscure. …. A proper analysis would make sure that these sorts of things hadn’t skewed the data.”


  43. 93
    dhogaza says:


    If this were true, over the last several years we would’ve been treated to a steady stream of skeptics publicizing their papers that have been turned down by peer-reviewed journals, and we could verify that they weren’t turned down for being crap but rather for not being “politically correct”.


    And, yet … what do we have? Spencer has recently made a big deal of his latest opus not getting published by his first venue of choice, only his second, with all sorts of dark hints about bias, but the reality is a high percentage of papers have to search for a home, nothing unusual about this at all. Likewise RP(sr?) making a big deal out of being denied an NSF grant, dismissed by a form letter that states his proposal made it out of the review stage but didn’t pass the final cut based on funding priorities. Bias! he screams. But the majority of grant requests to the NSF don’t get funded, regardless of merit.

    So what we have are a handful of whining complaints about bias which really don’t stand scrutiny, and certainly aren’t in numbers to account for the fact that mainstream workers are publishing hundreds or thousands more papers than the poor, downtrodden skeptics who, for the most part, don’t even bother writing papers for submission.

  44. 94
    Grunt says:

    But it was cold this winter and C02 is plant food and only a trace gas and the greenhouse effect has been disproved anyway and even if the greenhouse effect does exist, C02 has negligible impact compared to water vapour and our only source of heat is the sun so it must be the sun, unless it is due to the C02 from volcanoes, but C02 follows warming so it can’t be the C02 and the medieval warm period was warmer anyway and all the temperature reconstructions that show this not to be true are produced by corrupt scientists being paid by corrupt governments that have colluded to create an excuse to form a one world unelected social-ist government and even if the scientists are not that corrupt, although the e-mails prove they are, they have still got it wrong as the climate sensitivity is not as high as they think it is because it is basically the planets orbits and cosmic rays so we can say for a fact that the warming that probably does not exist is definatley not due to humans and even if it was the evidence is not sufficient to make drastic changes to the economy and increase taxes so that the politicians and scientists and business leaders get rich and leave us all poor – do they think we are stupid or something?

    [Response: Based on this comment, yes.–eric]

  45. 95
    Gilles says:

    #89 Chris, I think that I understand your point, but I hope you’ll understand mine.

    When you say “reduce CO2 emission”, you mean (as everybody I guess) : for a given amount of services (measured by GDP, or another index if you dislike it).

    Cause it is of course obvious to reduce CO2 emissions if everybody accepts being poorer – say going back to the XIXth century or live like indian people. So the challenge is to reduce CO2 emission without loosing our quality of life.

    My point is : ok, but once you have done that, what prevents using the spared FF to increase the wealth of much poorer people ? For instance even with Peak oil, we may be able to produce 50 Mbl/d of oil in 2050 ,say. Assume you have done a great effort for conservation, allowing to burn only 25 Mbl/d for the same standard of living. Right. My point is : are you sure that they aren’t very poor people in the world that would be very happy to use the spared 25 Mbl/d ???

    after all, there will be still plenty of oil fields, equipped with rigs , extracting these 25 Mbl/d – but very capable of extracting twice as much ! guys , the oil is just there in the ground, you just have to open the tap and find customers … do you REALLY think that nobody will be interested by these cheap extra 25 Mbl/d ??? and how will you insure that (and incidentally how will you justify morally to prevent poor people to access them ?)

    Concerning sea level rise, I would just point out that even hundreds of trillions of dollars is a very small fraction of the global GDP integrated over the whole century, and that if you believe the work of Rahmstorf et al., the sea level rise would hardly change if we divide by two the CO2 emissions, so the problem will happen anyway. I already raised the point : either the time constant is very short and the sea level rise will be kept in reasonable values (< 50 cm), or it is much longer and it will be quite insensitive to what we are doing just now – it will keep rising anyway and reach one meter or more.

  46. 96
    Snapple says:

    “The notion of making large financial decisions in an uncertain context is in no wise exotic — it’s what business executives do every day.”

    I have never heard the Libertarians, whom I watch on Russia Today (RT), make the argument that we should have let the free market forces take care of the Hitler problem.

  47. 97
    Ray Ladbury says:

    J and Slate say: “If skeptics are being shut out of journals, their publication counts would go down, which would produce precisely the results shown in the PNAS paper.”

    This demonstrates a fundamental misunderstanding of how science works. If the approaches taken by the so-called skeptics were really more fruitful for understanding Earth’s climate, they could not be shut out. Their success would speak for itself and any climate scientist who wanted to succeed would have to adopt those methods. Instead, quite the opposite effect is seen. The few “skeptical” publications really add little or no insight and generally lead nowhere. The problem is that for a scientist, it simply is not sufficient to say, “We don’t know anything! It’s too complex!!” You have to find a way forward. The consensus model of Earth’s climate is such a way. It has the unfortunate implication that we are cooking our own goose, but I am not aware of any natural law that says the world should conform to our wishes.

    [Response: Highlighted by me to reward conciseness and clarity.–eric]

  48. 98
    caerbannog says:


    If the skeptics are actually being shut out of journals, then they could provide evidence of such by producing the papers that they submitted and were then rejected, along with the reviewers’ comments.

    It’s rather hard to argue that one is being “shut out of journals” on the basis of papers that one has never submitted.

  49. 99
    MapleLeaf says:

    Grant @96. Excellent summary :) Alas, all those canards are enough to confuse many, many lay people.

  50. 100
    PaulM says:

    “[Response: There is, however, no evidence that ‘skeptics’ are being shut out of journals.]”

    Eric seems to be in denial of the climategate emails.

    [Response: Don’t be an idiot. The climategate emails, at worst, show that some people expressed frustration with some specific authors and editors, in private emails. There is no evidence that anyone actually tried to ‘block’ papers other than by expressing their strong views of the quality of the papers. Yet the papers in question still got published and cited. So even if there was some sort of nefarious intent (which I doubt) it wasn’t successful anyway.–eric]