RealClimate logo

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. 1
    Steve Bloom says:

    “(I)t 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.”

    I’m afraid this position is all too common, albeit rarely stated overtly. The closely related position of “emissions reductions are too hard, so let’s dig for a techno-pony instead” is, as you know, heavily promoted. I would argue that the latter has the effect of facilitating the former.

  2. 2
    Luboš Motl says:

    Of course that Richard Lindzen thinks – knows, to be more accurate – that attribution is impossible unless the “signal” exceeds “noise”. Isn’t it a tautology from statistics? Isn’t it how a “signal” is really defined?

    [Response: If you think that the only signal of sea level rise that can be recognized has to exceed 120m, then you are more than a little confused. – gavin]

    Richard emphasizes these points more often and more clearly than anyone else. The planet is “breathing” and these changes don’t have any simple-to-describe causes. It is a pretty much chaotic system. After all, that’s why Richard is skeptical even with respect to various “simple” answers about the causes of climate change that have been proposed by some of the skeptics, most notably with respect to cosmoclimatology.

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

    The idea that one can describe every wiggle of the climate by some manageable, predictive models – and that a cause for every wiggle has to be looked for and found – is just childish. There actually exists a consensus among all sensible people about pretty much all of these basic qualitative questions.

    [Response: Not sure who you are arguing with here. But wiggles at any scale usually have some set of scientists interested in them. – gavin]

    The only problem is that the consensus fundamentally disagrees with the texts one can read on the Real Climate blog.

    [Response: Let’s leave that for the readers to decide, eh? Or perhaps it should be decided by relative Erdos numbers? ;) – gavin]

  3. 3
    Jim Groom says:

    Well done gentlemen. Will your comments add much to the consensus argument? You end with ‘doubtful,’ I certainly hope you are incorrect.

  4. 4
    Richard T says:

    Based on the rage against this paper at some skeptic blogs, I thought the list of unconvinced scientists must have been derived from hacked emails and waterboarding.

  5. 5
    bigcitylib says:

    Would Eric’s objection to Prall’s dataset (which is mind you NOT given in the paper and not even precisely the list used in the paper, merely linked to by the package of material around the paper) be met if the dataset were made private or pulled down?

    I think this objection is a bit of a red herring: the signatories were more than willing to have their names associated with these petitions when they were in production and being sent off to whomsoever, and the underlying documents are still out there, so a “blacklist” be created from any of them. But would it really be this easy to satisfy Mr. Steig?

  6. 6
    Peter says:

    It seems to me that there are a number of straightforward questions that scientists can answer for the general public to show whether or not there is a consensus. The questions are
    1) Is there reasonable certainty that global climate change occurring?

    [Response: Yes. Multiple independent datasets show consistent patterns of change. – gavin]

    2) Is there reasonable certainty that the dominant driving force in the climate change is caused by man? (What you call attribution.)

    [Response: This isn’t quite what is meant by attribution. The dominant driving forces on climate are caused by man (chiefly the increase in GHGs, aerosols, land use change etc.), and it is very likely that this explains the bulk of the changes in the last few decades. – gavin]

    3) Is climate change something to raise concern over? That is, is it likely to cause significant adverse effects that people should worry about?

    [Response: Yes. Many of the choices that society has made implicitly rely on climate – where we grow crops, how close to the beach we build houses, what kind of houses we build, how we get our water etc. The climate changes foreseen under ‘business as usual’ policies will make obsolete many of those assumptions. ]

    4) Can we do anything to halt and/or undo the change?

    [Response: Yes. There are easy things – greater energy efficiency, reductions in methane and black carbon emissions etc. – and there are harder things, scaling up renewable energy sources, electrifying surface transport, international agreements – but those actions should be able to steer our course away from the worst impacts (although some further warming is inevitable and will need to be adapted to in any case). ]

    I think that these are simple enough yes or no questions that the average person will understand but informative enough to give a general consensus. The average person honestly doesn’t care about the specific wording of the IPCC report (please don’t take offense at this) but they want to know if global climate change is going to affect their lives.

    [Response: No offense taken! (and indeed, I completely agree). – gavin]

  7. 7
    thingsbreak says:

    “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).”

    Are the comments section of this post an appropriate place to engage Eric on his Dot Earth comments? For instance, I’m sure I’m not alone in being more than a little puzzled by them. Especially:

    “The idea of listing the names of those people analyzed is disturbing for reasons that should be obvious. In this respect I completely agree with Roger that the “blacklist” metaphor is appropriate. And it cuts both ways too. People can now use this list to create their own “blacklist” of so-called “believiers.””

    There was no “listing of names” in the paper, the SI, or the link provided in the SI. This was a complete fabrication by some interested in discrediting the paper. The names *used* in generating data for the paper were taken from public statements, i.e. the only “lists” or “black lists” were those created by the signers themselves. It sounds an awful lot like Eric either didn’t read the paper, or is confused about where those data came from. There is no justification for disparaging Prall’s efforts as creating a “black list” from what I can see.

    If Eric could address this issue, it would be greatly appreciated.

  8. 8
    Len Ornstein says:

    Gavin and Eric:

    I agree completely with your comment.

    However, a very large part of how the public responds to the ‘divide’ between “the consensus” and the “deniers”, has more serious roots:

    Generally, considering that technological applications of scientific models, developed to reduce uncertainty about real-world risks, have been widely successful for making life safer and more comfortable for an increasing fraction of the world population, why is there so little trust in the judgments of scientists who generate and test such models?

    To answer this question, let’s examine SOME of the roots of the divide between the anthropogenic global warming (AGW) scientific “consensus” and the view of the skeptical “deniers”:

    Can the divide be bridged?

    Beginning (near the turn of the 20th century) with the theoretical studies of Svante Arrhenius about how infrared absorbing gases help determine the surface temperature of the earth; then spurred by the reexamination of those models in the 1950’s, by Roger Revelle, and in the 1960’s, by Jule Charney; and then James Hansen’s modeling of the unique green-house-gas (GHG) forcing of the very hot atmospheric temperature of Venus – climatologists and geophysicists began to vigorously reexamine such models in greater detail. This was strongly stimulated by Charles Keeling’s accumulating data of the steadily increasing concentration of well-mixed atmospheric CO2, measured at the Mauna Loa Observatory, beginning in 1958, at about 317 ppm (and presently at about 390 ppm). Quite early, it became quite clear that the CO2 concentration had been flat, at about 280 ppm for centuries (if not millennia) prior to the growing burning of fossil carbon (coal, petroleum and natural gas) to fuel the industrial revolution. That CO2 record was the prototypical – and almost ‘noiseless’ – “hockey stick”.

    Although the most advanced theoretical climate models still leave uncertainty, particularly about the sign and magnitudes of the effects, on GHG feedbacks, of some low- and high-clouds, a consensus began to develop that threats of resulting increases in global temperature – and the very large risks associated with their possible consequences – deserved substantial increase in attention.

    Increasing efforts ensued to TRY to collect sufficiently unbiased, and statistically significant ‘other’ proxies for the hockey stick: global mean surface temperatures (GMST), ocean heat content (OHC), seal level rise (SLR), glacial ice-cores, sediment cores, tree-ring dendrology, etc. – all much ‘noisier’ than the Keeling curve. The GMST trend for the last 40 or so years has converged to something like a mean of +0.2ºC/century, with considerable spread to the associated ‘95% confidence interval’. The other proxies may be slightly less convincing – but are not too out of line. And the increasingly more realistic (and more complicated) climate models, initialized with historic data sets, provide predicted/projected extrapolations that are not ‘too’ far off either.

    There’s a general ‘feeling’ that such ‘reinforcing’ correlation of very different ‘kinds observations’ and models SHOULD help to build confidence above the level provided by each ‘independent’ data set. But SO FAR, no good ‘statistical’ tools exist for ‘averaging’ such diverse results to get a ‘net mean and its confidence interval’. In the breach, a widely accepted, but ‘uncomfortable’ paradigm has developed, among both scientists and policy makers, to tentatively rely on the collective intuitions and confidence of those ‘expert peers’ who are judged to be most familiar with the data sets and with the relevance of that data to related physical models.

    Even if the GMST trend were ‘only’ +0.1ºC/century, the associated risks would be delayed only by a ‘blink’ of geologic time – still demanding to be taken quite seriously, NOW! However, that conclusion is pretty much ignored!

    This certainly is an over-simplified account. But it probably describes the root of the origins of the mainstream AGW “consensus” – and of the current position of more conservative ‘warmists’ – and why they believe we must begin to seriously, at least, plan for mitigating AGW risks.

    Some of the apparent internal ‘contradictions’ just reviewed seem inimical to the mind-set of most skeptical “deniers”.

    They, and many others, are also put off by the record of apparent ‘failed jeremiahs’:

    1) Robert Malthus, who at the end of the 18th century, published his simple but penetrating theoretical econometric model, “An Essay on the Principle of Population”, that has turned out to have been ‘off’ in the timing of its predictions (but I believe, probably is about ‘correct’ in predicting what we must expect, if some appropriate changes in human behavior fail to accommodate – ‘in time’ – to the reality of the finite resources of our planet); and

    2) the predictions of the Club of Rome’s 1972, “The Limits to Growth”, that also have proven to have been somewhat premature.

    Whether there remains any residual truth is such “predictions” is ignored. A majority look at them as major scams, dishonestly foisted on the public by unscrupulous – or dishonest scientists.

    And the IPCC was supposed to adhere closely to “policy relevant” rather than “policy prescriptive” issues! How could the IPCC leadership get away with pushing their ideological perspective on the world, in such stark contravention of their assigned task? That policy relevance depends completely upon assigning values to possible outcomes, and therefore is inseparable from models of possible prescriptive cures, – that the charge is self-contradictory (and impossible?) – is ignored.


    a) The perceptions of just where science fits – in the spectrum of beliefs – differ among policy makers, the general public – and, to some extent, even among scientists – and this also has to contribute a great deal to the resulting dissonance.

    b) It certainly doesn’t help that many believe motivation for science, does and should stem from values derived from Golden Rules (close to: pragmatic rules to govern personal behavior of members of a very communication-competent species, to tend to enhance biological ‘self’-preservation, through cooperation designed to maximize ‘group/species’-survival),

    c) while others, e.g., Logical Positivists, insist that science can, – and ‘should’ – be freed from all such metaphysical baggage (fundamentally incorrect conclusions, as I argue in the reference, below). And

    d) still others say the only motivation for ‘true’ science ‘must’ arise from value-free curiosity – whatever that is – poses other serious problems ;-)

    I believe these unpleasant pieces of the puzzle need to be fit into place in order to understand the internally conflicting positions of many honest “deniers”, and to understand and the positions of others who are committed to absolute confidence in the truth of some fundamental ‘axioms’ of their ideological (religious/mathematic/econometric/political) belief systems. Like so many others, as well, they don’t yet understand how to accommodate to the unavoidable finite range of residual uncertainties about ALL scientific ‘facts’. They fail to appreciate that observations only can increase or decrease – but never absolutely prove, or FALSIFY – confidence in scientific models/theories.

    Their conundrum therefore remains: which models/theories of science can be trusted; HOW MUCH can they be trusted; and why? So far, science and science education rarely even attempt to answer these questions in a straightforward manner!

    For further ‘clarification’ of these latter points, see:

    “The Sceptical Scientific Mind-Set in the Spectrum of Belief: It’s about models of ‘reality’ – and the unavoidable incompleteness of evidence, for – or against – any model”, for THE(?) argument of why science provides the ONLY reliable tools to help us to deal with real-world risks!

  9. 9
    Tom Fuller says:

    Regardless of the authors’ motives, there now exists a list of people who have signed petitions of widely varying subjects and goals. They will be lumped together. It will be used as a blacklist.

    [Response: Oh please. Michael Tobis has said all there is to say with respect to this. Take it over there. – gavin]

    Given Spencer Weart’s almost immediate dismissal of this paper, I find it astonishing that you attempt to keep it alive as possibly relevant to the climate change discussion or to science itself.

    Eric, your comments to Roger Pielke Jr. were much more salient yesterday. This is junk science that will be used maliciously. Do the world a favor and say so here, as you did yesterday at Pielke’s blog, where you wrote:

    “Wow. Roger, you know I disagree with you on many things, but not on this.
    What the heck where they thinking? Even if the analysis had some validity — and from a first glance, I’m definitely not convinced it does — it’s not helpful, to put it mildly. I’m totally appalled.”

  10. 10
    David B. Benson says:

    Peter (6) — I recommend reading Mark Lynas’s “Six Degrees”:
    We already experiencing some of the effects of the first degree.

  11. 11
    Tom S says:

    I think one should consider some confounding factors here:

    1. What are the political leanings of the convinced list?

    [Response: The ‘CE’ list is that of people who have signed statements basically calling for emission cuts. There is no further insight into their political leanings. – gavin]

    As AGW is a highly politicized field, is it not true that this may simply be a measure that most of the highly qualified scientists are Democrat, or lean to the left? Academia is heavily biased toward the left, so one would expect most highly degree’d researchers to be left leaning.

    [Response: But these aren’t statements about the most qualified scientists, just those who signed public letters calling for action. However, there certainly are a wide diversity of political beliefs among climate scientists and though I won’t go through lists, I know a few strong Republicans and few that are more to the left, and more than a few independents. However, for the vast majority of my climate scientist colleagues, I have no idea since it doesn’t come up in conversation much. – gavin]

    2. If research funding is heavily biased in favor of proving AGW, would not the natural result be the one that was found?

    [Response: It isn’t, so your question is moot. Look up some of the NSF awards on the subject (all online), they simply aren’t the kind of thing you imagine. – gavin]

    Whether research is heavily biased toward “proving AGW” is a slippery topic that cannot be readily proven. An interesting question though. Maybe someone should do a paper on it (ha ha).

    [Response: Sure it can, Read the abstracts of what does get funded. – gavin]

    Although research results are supposed to be neutral, I expect there is a lot of pressure to produce results that confirm AGW. This tends to show up with a lot of highly qualified scientists making questionable statements to the media to the effect of “we believe X is a result of AGW, but we need to perform further research to confirm this…”.

    [Response: This is simply fantasy. – gavin]

    3. A reminder, being smart != being right. It may mean it is more likely though.

    It may also be the case that nobody knows an answer with any meaningful degree of certainty, which I believe to be the case here. When forced to take a position, if more PhD’s say a coin will land heads up, it is not meaningful data. Crappy analogy, but you get the point.

  12. 12
    Steve Bloom says:

    Re Gavin’s response to #2: “Or perhaps it should be decided by relative Erdos numbers? ;)”

    Ooh, so painful, so richly deserved. This one goes into my favorites folder.

  13. 13
    BobN says:

    Glad to see you guys weigh in on this and that you recognize some of the shortcomings of the paper. To me at least, using proxies to both assign individuals to one group or another and to assess their credibility is problematic. If, however, instead of trying to make their findings about the fairly subjective term of credibility, the authors had instead used the term “credentials” as you do above, the paper would likely not have created quite the stir it did and might be a better piece of work.

  14. 14
    Edward Greisch says:

    Reference: “Climate Cover-Up” by James Hoggan. The first reason for confusion is the fossil fuel industry, notably the Western Fuels Association, Exxon-Mobil and Koch Oil Co have spent half a billion dollars so far to confuse everybody. They have succeeded with a great many people.

    The second reason for the confusion is the journalistic habit of selling newspapers by reporting controversy, whether there is any or not.

    The third, but most important reason for confusion is the poverty of education. Most high school students take no physics at all. Most people don’t go beyond high school. Whatever the reasons for this, the result is an electorate that is easily led astray. Anderegg et al’s paper would not be necessary if almost all citizens had an education appropriate to a high technology civilization.

  15. 15
    Peter says:

    I hope that my earlier post was not taken as an AGW denial. I meant it only as a suggestion on how to investigate the opinion of the majority of climatologists and communicate that to the general public. I understand the statement that the climatologists (and scientists in general) may not be entirely interested in responding to a survey, but limitting it to 4 very simple and straightforward questions couldn’t hurt.

    David: Very interesting and terrifying article. The text of the 3rd degree seems to indicate that we are already in a very dire situation. It is my opinion that we can not possibly get the world to reduce it’s carbon emissions. :( I will not be sleeping well tonight.

  16. 16
    MapleLeaf says:

    Personally I am incredibly disappointed that Pielke Jnr and Spencer, amongst other ‘skeptics’ have decided to use this paper to play victim. The whole “black list” myth is pure political spin and nothing more. Shame on you Roger Pielke Jnr and you too Roy Spencer.

    Anderegg et al. decided who to place in the UE group according to which petitions or letters of protest the people in question elected to add their names to. If someone else has a better objective way, then please let us hear it. They willfully placed their names on those petitions, and in doing so signed off on the statement that went with said petition or letter arguing that AGW/ACC is a non-issue. for example.

    So I am dumbfounded how they claim to be on some fictitious “black list”, when they are happy to publicly state their stance on one or more petitions.

    It is also ironic that it is the skeptics who repeatedly claim that there is no consensus (e.g., Solomon’s recent claims) and then when presented with quantitative evidence to the contrary cry foul and descend into invoking Godwin’s law, the Spanish inquisition, McCarthyism and mysterious “black lists”.

    IMHO, the “consensus” on the validity of AGW/ACC arises from the scientific literature and observations, and multiple independent lines of evidence pointing to a discernible and increasing anthropogenic finger print on the climate system, and not necessarily form a head count of scientists being in one group or the other.

  17. 17
    Doug Bostrom says:

    Gavin: Look up some of the NSF awards on the subject…

    NSF maintains a marvelous database, freely accessible. Here’s a link with the query parameters set to an appropriate program.


  18. 18
    Roger Pielke, Jr. says:

    Gavin and Eric- You have mischaracterized the PNAS paper, it does not make any claim whatsoever to be segregating people based on their politics, as you suggest, but purely on their views of science.

    This confusion/conflation gets to the nub of the matter:

    [Response: Sorry, but it is you that are confused. First off, the statement in the above post you quote “So, do climate scientists…” is perfectly true and not actually referenced to the paper you want to discuss. Second, there is no indication anywhere in any list of what people’s ‘politics’ are – merely whether they have publicly pushed for policies that would regulate emissions or not. This in no way determines someone’s ‘politics’. Third, the comparisons in the paper are among people that have signed letters that advocate for something, not merely lists of people that agree with the IPCC report. Try reading them! Whatever flaws or ambiguities exist in the paper, the use of the letters as source materials for any comparison cannot purely be a test of agreement with the IPCC (as we stated above – you could agree with every word in the IPCC report and still not want to do anything about emissions), but must be a test of someone’s opinion about what to do about it.

    For instance, the Bali letter was in support of a 2 deg C guardrail for temperature, the Cato letter was against any action on emissions, the 1992 SEPP letter was against ‘immediate action’ on emissions etc. – each of the letters is clearly related to policy (though generally not in a very specific sense). Thus the only way in my mind to interpret a comparison of signers is a categorization by policy direction, not understanding or agreement on the science. Perhaps the authors of the PNAS paper would disagree, but that is up to them. Do not confuse something they may or may not have said with what I and Eric have said. We aren’t the same people. Thanks! – gavin]

    [Further Response: My characterisation of the Cato letter is not right. It’s not explicit what the signers are advocating (though implicitly the message is clear). The advocacy of the SPPI letter is much more explicit. – gavin]

  19. 19
    Roger Pielke, Jr. says:


    I am not a skeptic, nor am I on any of the Anderegg et al. lists, nor have I signed any petitions. Thanks!

  20. 20
    David B. Benson says:

    Tom S (11) — I urge you to consider the simplified physics in
    which explains the last 13 decades of the instrumental record as primarily due to increasing concentrations of CO2 in the atmosphere.

    Peter (15) — I encourage you to encourage many people to read it.

  21. 21
    Andrew Adams says:


    Although research results are supposed to be neutral, I expect there is a lot of pressure to produce results that confirm AGW.

    What motive would there be for this?

  22. 22
    Andrew Adams says:

    #9 Regardless of the authors’ motives, there now exists a list of people who have signed petitions of widely varying subjects and goals. They will be lumped together. It will be used as a blacklist.

    By whom and for what purpose? Anyway the lists on Prall’s website have been there for ages – how come people are only complaining now?

    [Response: Rhetorical convenience is the obvious answer. But can we not go down this ridiculous ‘black list’ rabbit hole? There are real issues and real harassment and real persecutions going on without having to invent reasons to be outraged. – gavin]

  23. 23
    Gneiss says:

    Len Ornstein wrote,
    “They, and many others, are also put off by the record of apparent ‘failed jeremiahs’:

    2) the predictions of the Club of Rome’s 1972, ‘The Limits to Growth’, that also have proven to have been somewhat premature.”

    A bit off topic but I’d like to respond regarding the belief, widely held by people who haven’t read the book, that The Limits to Growth prematurely predicted doom.

    Looking forward from 1970, the model of Meadows et al. does predict doom in the form of population/resource/pollution overshoot and collapse. But that doom isn’t supposed to have happened by now. The model’s standard run (Figure 36) depicts world population climbing until the mid-21st century before crashing down.

    They carefully state that this is not meant as a firm prediction,
    “The exact timing of these events is not meaningful, given the great aggregation and many uncertainties in the model. It is significant, however, that growth is stopped well before 2100.” (p.132)

    It seems premature to call this warning premature, does it not?

  24. 24
    MarkB says:

    Tom Fuller: “Regardless of the authors’ motives, there now exists a list of people who have signed petitions of widely varying subjects and goals. They will be lumped together. It will be used as a blacklist.”

    Umm…Tom? Those lists have been out there for a long time. Direct your faux outrage towards Inhofe/Morano, for starters.

  25. 25
    gavin says:

    Just to make a couple of things clearer. First, a database with cross tabs on various issues can be looked at in many ways and even if someone doesn’t like the way Anderegg et al have done it, anyone can do it any way they choose (as we did above).

    Second, please do not bother leaving comments with ridiculously stretched analogies. You might be surprised at how close to home some of those historical events are to many people here, and the trivialisation of those issues by their use on this issue demeans everyone who uses them. So just don’t.

  26. 26
    MarkB says:

    Calling on AGU climate science experts:

    This has the potential to go a long way to combat disinformation and a confused media.

  27. 27

    Len 8,

    Try 0.2 K per DECADE, not per CENTURY.

  28. 28
    pete best says:

    Dear RC

    Of course that Richard Lindzen thinks – knows, to be more accurate – that attribution is impossible unless the “signal” exceeds “noise”. Isn’t it a tautology from statistics? Isn’t it how a “signal” is really defined?

    [Response: If you think that the only signal of sea level rise that can be recognized has to exceed 120m, then you are more than a little confused. – gavin]

    From Lubos Motl’s post I often see this argument about the noise and the signal. Is this spurious or real in climate science. One alleged climate scientist I spoke with online once via a forum beat me around the head with this statistical fact. I still cant find a valid answer to it but its one that needs to be addressed so I can answer him back.

    I am presumng that this article is refering to the NAS report on the medias attitude to ACC?

    Quite frankly here in the UK 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. Its just not right to do it this way but it is the way it is done. In the USA both sides are heard but not so much balance is given I guess.

  29. 29

    Andrew Adams 21: What motive would there be for this?

    [Brain voice:] To take over the world!

  30. 30
    Phil Scadden says:

    “Yes. There are easy things – greater energy efficiency, reductions in methane and black carbon emissions etc.”

    And how about rapid phasing out of all subsidies on fossil fuel. How hard is that?

  31. 31
    w kensit says:

    to #9,
    There is nothing more dangerous to the future of mankind than the IPCC report and the articles derived from it painting the scenarios of 350 ppb or 450 ppb or 550 ppb of CO2. The assumption that we can smoothly forecast the future climate beyond what is visible out the kitchen window is highly misleading. We live with an atmosphere composed of 393ppb CO2. Any forecasting of our future climate even with no increase in GHG is fantasy.
    The IPCC works with knowns and refuses to entertain the possibilities, rightfully so for fear of opening itself to charges of sensationalism, of the unknowns. Today scientists can’t tell you what will be the minimum extent of arctic ice this summer or quantify the cubic kilometers of ice lost from 2009 to 2010. I can assure you however that the scientific consensus will underestimate the actual as it has consistently done in the past.
    Picture climate as a large soft inflated balloon floating in a room and 1C as a poke in its side 3 centimeters deep. Scientists calculate where that poke will propel the balloon. But as the balloon crosses the room it passes other people who are free to poke it with various energies, left,right,up,down,forward and even backward. How much are you willing to bet on the scientist’s forecast? Mankind is betting its future on the scientists forecasts of life at 450ppb. How comfortable are you with that? If I told you that I just read of plumes of methane being discovered rising in the Arctic ocean, would that change your comfort level?

  32. 32
    David B. Benson says:

    Phil Scadden (30) — Hard, but give it a try.

  33. 33
    MapleLeaf says:

    Dear Roger,

    Let me be clear, I was talking about “skeptics” in general. I singled you and Spencer out for your inflammatory blog posts. I never said you were on the UE list.

    That said, going by the content that you elect to place on your blog, I’m afraid you sound very much like a “skeptic” or a contrarian perhaps. You are certainly skeptical of the IPCC and WGII in particular.

    Anyhow, I know that you are not in the UE database, so all the more reason to be perplexed why you are getting so upset; and why on earth are you using this paper as an opportunity to make ridiculous assertions about fictitious nefarious lists on your blog? You seem to be trying to pick a fight for no justifiable reason (I am trying to leave your dad out of this, so please don’t go there, besides he can fight his own battles if need be, no?).

    As others have stated, Dr. Tobis is has summarized the paper and its context very nicely. This outrage by those critics of climate science is much at to do about nothing and seemingly has been jumped on by you and others for the purpose of trying to score political points. Do you agree with what Spencer said? I would very much appreciate an answer. Thanks.

    The real travesty here is that some climate scientists really are being persecuted, yet you have not been terribly vocal, if at all, in condemning the suggestions of Beck, Morano, Limbaugh, Cuccinelli and Inhofe. IMHO, your credibility would benefit much more from taking the aforementioned persons to task rather than providing more fodder for the ‘skeptics’. With respect, in failing to do so you really have no reason to whine about this.

    [Response: 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.–eric]

  34. 34
    Roger Pielke Jr. says:

    Gavin (#18)

    Thanks kindly for your response. A few replies.

    First, you write, “Whatever flaws or ambiguities exist in the paper, the use of the letters as source materials for any comparison cannot purely be a test of agreement with the IPCC (as we stated above – you could agree with every word in the IPCC report and still not want to do anything about emissions), but must be a test of someone’s opinion about what to do about it. . . Thus the only way in my mind to interpret a comparison of signers is a categorization by policy direction, not understanding or agreement on the science. Perhaps the authors of the PNAS paper would disagree, but that is up to them. Do not confuse something they may or may not have said with what I and Eric have said.”

    You do realize I hope that with these statements you have completely undercut the entire methodology of the PNAS paper? I had thought that this post was about that paper. If it is about something else, then indeed I am confused. I have characterized the paper as an inkblot, and perhaps that is what we see here.

    [Response: All we see here is you continually ‘misunderstanding’ things in order to make sophmoric debating points. You do not seem to tire of this, but I certainly have. – gavin]

    2. Thank’s for the lecture of the definition of “politics” — I will share with my colleagues in political science ;-)

    [Response: Let me know if they want the definition of science too. ;-) – gavin]

    3. But lets take your spin on the paper rather than the authors’and let me ask a follow up question — To be clear, do you really think that a 1992 statement on “immediate action” is relevant to discerning someone’s views on action in 2010? Really?

    [Response: Hey, I know what, why don’t you ask him? In the meantime, please note that this is completely besides the point. The database exists and people can do any comparison that they feel is meaningful. If you want to focus on letters written since 2007, go right ahead. Be sure to let us know how it turns out. – gavin]

    PS. Some of us actually have lives, so if you want specific responses after work hours, you might need to be a little patient.

  35. 35
    Roger Pielke Jr. says:

    -33-Maple Leaf

    Thanks for the response. My “skepticism” of IPCC WGII has to do with its misrepresentation of peer reviewed science involving work that I’ve contributed to. if you’d like to learn more, drop me an email or read the relevant posts on my blog. I hardly think that asking for science to be correct is qualifications for the old “skeptic” label, but who knows these days;-)

    I have not read Spencer’s comments, sorry.

    Do you really want to claim that I have not criticized Inhofe and Cuccinelli? I have a pending debate with Morano in the works. I generally ignore Limbaugh and Beck, though beck did criticize soccer, which I saw as way over the line, and said so. ;-)

    Anyway, your criticisms will be much more solid if you inform yourself of my actual views. Thanks!

  36. 36

    I have posted on the PNAS paper on my weblog – Comments On The PNAS Article “Expert Credibility In Climate Change” By Anderegg Et Al 2010 []

    [edit out offensive statement]I propose your readers comment our paper (of which all of the authors are AGU Fellows]:

    Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R.
    Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W.
    Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell, W. Rossow,
    J. Schaake, J. Smith, S. Sorooshian, and E. Wood, 2009: Climate
    change: The need to consider human forcings besides greenhouse gases.
    Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American
    Geophysical Union.

    including comments on the three hypotheses, discussed in our paper, that I reproduce below

    Hypothesis 1: Human influence on climate variability and change is of minimal importance, and natural causes dominate climate variations and changes on all time scales. In coming decades, the human influence will continue to be minimal.

    Hypothesis 2a: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and involve a diverse range of first order climate forcings, including, but not limited to, the human input of carbon dioxide (CO2). Most, if not all, of these human influences on regional and global climate will continue to be of concern during the coming decades.

    Hypothesis 2b: Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and are dominated by the emissions into the atmosphere of greenhouse gases, the most important of which is CO2. The adverse impact of these gases on regional and global climate constitutes the primary climate issue for the coming decades.

    [Response: The problem with this paper is that it strongly implies that Hypothesis 2a is original, and that the rest of the climate science research community thinks that only 2b applies. That’s a strawman argument. Furthermore, these are not well-separated, mutually exclusive hypotheses, which means that choosing one over the other is misleading. Yes, I have read the paper.–eric]

  37. 37
    Len Ornstein says:

    Gneiss (23)

    I agree with you. Note I said “apparent”.

    B. P. Levenson (27)

    Wow! Thanks. What a dumb typo! Hope most readers recognized them (also “+ 0.1/century”) as typos.

  38. 38
    Zer0th says:

    Mr MapleLeaf, your calling on Rodger to deliver ritual denunciations to enhance his perceived credibility in your mind, neatly demonstrates the problem here. Fact is, like or not, a number of notables from across the entire spectrum on climate/politics et al, that agree on little else, are reflexively discomforted by this paper.

  39. 39
    Snapple says:

    “The real travesty here is that some climate scientists really are being persecuted.”

    Amen to that!

    Dr. Jones almost killed himself and the bloggers mocked him. Cuccinelli is persecuting Dr. Mann. He want all his papers so he can find something to hang a fraud charge on.

    I didn’t understand what those Republicans were until Climategate. Now I get it.

  40. 40
    Average Person says:


    1) 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.

    2) Yes, because of the huge increases in GHG, but there is no proof. Climate always changes, and our understanding of past changes also lacks clear proof (important point).

    3) Yes and no, the observations and proxy data such as deep-sea cores shows that climate will very likely change in the future, whether human emissions have a significant effect is entirely unknown (no proof). Research on human GHGs and their effect may be pointless, since the future climate may have already been determined thousands of years ago. Indeed, with a quick glance at the deep-sea core record, it does not take much imagination to figure out what is likely to happen next. The system appears to be deterministic.

    4) Unlikely. Deep-sea cores confirm glacial cycles. We only have a few hundred decades left, so you better grow some body hair.

  41. 41
    Didactylos says:

    I have enormous respect for Anderegg et al, and Naomi Oreskes. It takes a lot of courage to paint such a huge target on themselves and their work by shining a light on the scummy underside of climate denial.

    The vitriol and calumny that floods towards these scientists is simply reprehensible, and a sign of the lack of respect for science that permeates society. It is a violent knee-jerk reaction that never pauses to ask “who is right?”

    Those other unfortunate scientists (such as Mann or Jones) who never asked to be thrust into the centre of this manufactroversy have my total sympathy, and my full support. History will vindicate them, but that’s not enough.

  42. 42
    Steven Sullivan says:

    #36 — Why would *reflexive* discomfort of notables be something to appeal to? It implies a gut decision, not a thoughtful consideration.

  43. 43

    Eric – Please elaborate, however, on why hypotheses 2a and 2b are not sufficiently distinct. The 19 authors of our 2009 EOS paper concluded that they are. Hypothesis 2b is clearly the emphasis of the 2007 IPCC reports.

    As we wrote in our article

    “The evidence predominantly suggests that humans are significantly altering the global environment, and thus climate, in a variety of diverse ways beyond the effects of human emissions of greenhouse gases, including CO2. Unfortunately, the 2007 Intergovernmental Panel on Climate Change (IPCC) assessment did not sufficiently acknowledge the importance of these other human climate forcings in altering regional and global climate and their effects on predictability at the regional scale.”

    Also, you state that Hypothesis 2a is not original. Please refer us to where this perspective is discussed in the IPCC (and CCSP) reports.

    [Response: Eric can speak for himself, but other forcings are discussed in WG1 Chapter 2, section 2.3, 2.4, 2.5, through most of chapter 6, and all of chapter 7. The dominance of CO2 among the greenhouse gases is seen in fig 2.20 and fig 2.21 as well as the diversity of other forcings. – gavin]

    [Response: To answer your question about hypotheses 2a and 2b, it simply depends on what aspect of the climate system you are talking about. In many land areas, deforestation has a huge impact on the local climate, certainly larger than CO2, so far (Hypothesis 2a). In the central Pacific, it is certainly not land use that dominates; CO2 probably does (Hypothesis 2b). To suggest these are mutually exclusive is just wrong.

  44. 44
    Frank Giger says:

    Really? We knew all about character assassination from our experience with Democrats!

    Both sides do it, and have been for a long time. Doesn’t make it right, it just makes it an unfortunate reality.

    I really don’t understand why any scientist would sign the long petition that has many points unless one is in total agreement. There isn’t a line item veto or signing statement that goes with it – if I didn’t agree with all of it, I dang sure wouldn’t put my name on it. “Clarifying” what parts one agreed or disagreed with after the fact invariably sounds like trying to weasel out of one’s signature to the document (even when it is genuine).

  45. 45
    Geoff Wexler says:

    I shall try to recall my state of mind before I knew much about this subject. I did not have to rely entirely on authority because I could struggle with some of the original publications ,i.e a better kind of authority. But asking the judgements of experts was a major part of learning.

    Which experts? This can be an important choice when there is some controversy. I personally would not have found the Anderegg et al paper that useful for the reasons I have given here:

    However there are other indicators

    1. Does the author provide evidence of having considerable experience in the precise topic concerned? For example I was always supicious about so called experts who would rant about climate models without appearing to have worked in the area. (How about Freeman Dyson? and even some climatologists?).

    1a). Parts of climatology are mathematical.I would tend to give more weight to theoretical papers written by professional theorists than observational scientists who tend to write like amateurs when it comes to analysis. You can find examples in Tamino’s blogs at Open Mind (or of course RC).

    1b). The above argument has been been used in reverse to attack climatologists over their lack of statistical expertise especially over the first hockey stick paper by MBH. As I see it the reason for recent progress in this area has to do with improved data rather than improved statistical methods. I now think the original attack doesn’t stand up (see RC, Open Mind,Wahl and Ammann) although some anti-consensus scientists keep on echoing this old argument.

    2. In the case of theoretical papers,have their conclusions been confirmed by subsequent observations?
    Lindzen’s adaptive iris and his suggestions about negative feedback from water vapour are examples. They sound attractive at first sight because they provide a modern contradiction to Arrhenious’s initial paper. But time has passed and it should have become clearer. The first idea has never been substantiated by other work, and the second one has to contend with mounting observational and theoretical counter-evidence.

    3. I cannot help being influenced by some items which are not in the peer reviewed papers e.g. the popular writings of the same authors. It may be slightly illogical, but if they contain too much populist spin I become much more skeptical about the serious writings as well. Any writings by authors of some really bad papers fall into the same category. How do we know? It may require some skill but RC and Open Mind have been here to help and they have not been shown to be wrong over these very bad papers.

    4. I also have some experience in talking to other scientists both for and against the consensus in the core conclusions. I have noticed that the second category invariably consists of people who have not had the time to inform themselves and have had to rely on the media.

  46. 46
    Ray Ladbury says:

    It would appear that Tom S. is echoing Conservipedia in concluding that reality has a liberal bias.

    FWIW, I would not view the Anderegg paper as assessing credibility so much as assessing how positions re the consensus affect productivity. It is not that there are no smart denialists. It is rather that their rejection of consensus science regarding Earth’s climate places them at a tremendous disadvantage in trying to understand it.

    I would contend that this certainly has implications for their credibility on these matters and on policy, but to characterize the result as a “blacklist” is simply absurd. Scientists who are expert in a field generally know who to trust based on their experience and understanding–and the methods they use are not dissimilar. This work merely makes those assessments intelligible to a less expert population.

  47. 47
    Timothy Chase says:

    Regarding “Expert Credibility in Climate Change” (which is open access by the way) a friend of mine stated, “… the only ‘lists’ or ‘black lists’ were those created by the signers themselves.”

    I believe this is the point that really needs to be driven home. That and the fact that what the “contrarians” are really upset about is that they were trying by means of their lists to create the appearance that the climatology community is evenly divided — but now those lists and lists by scientists that affirm the conclusions of mainstream science have been used to show just how un-divided the scientific community actually is.

    The contrarians are a tiny but vocal and well-financed minority, similar to the libertarian/industry-funded scientists that opposed the regulation/phasing-out of dioxins, CFCs, asbestos, and cigarettes. (For more on this readers might want to consult the book “Doubt is Their Product” by David Michaels.) They publish less often, are cited less often, typically they are much closer to retirement as opposed to the concerned scientists, and even when they do publish in the peer-reviewed literature, typically their views are much more conventional than what they choose to express in the popular press.

  48. 48
    Edward A. Barkley says:

    From a layman’s perspective, even one who only remembers the textbook definition of the scientific method from undergraduate chemistry, any kind of consensus of opinions should be irrelevant to a scientific endeavor. We think scientists should be using the working theory to make predictions for the future that can be measured and verified – preferably as clearly as possible in advance that success can be properly lauded. 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. 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. We are being asked to fund a multi-trillion dollar, civilization-changing, socio-political experiment without seeing evidence of predictability. If your computer models cannot stand up strongly enough to make reasonable predictions of near-term climate effects, then the word “crisis” should leave the debate along with several trailing zero’s at the end of the funding check. We are not asking you to predict the world’s climate on the day of next year’s World’s Cup Final, we are only asking for some kind of measurable predictability. [edit – defamatory and vague accusations removed] will not convince anyone anymore. We’ve learned that you can say anything you want with statistics. Now, making predictions that can be measured…that’s evidence worth writing a check for.

    [Response:Your arguments about non-predictibility is nonsensicle. If I tell you that breathing asbestos has a high probability of causing lung cancer, but that you won’t be able to see the effect for 10-20 years, what is your response? Breathe deep?–eric]

  49. 49
    BobN says:

    The above back and forth between Roger Pielke Jr and Rc (#18) just illuminated for me one of the significant problems with the Anderegg et al paper. In defining its grouping, it uses singed delcarations/letters which are political statements regarding appropriate actions/inactions as proxies for assessing a scientific conclusions regarding the attribution of recent warming. some of this political statements may be reasonable proxies for a scientist’s position on the relative role of GHGs (e.g., the 2008 Manhattan Declaration) while others (e.g. the 1992 SePP Statement and the 1995 Leipzig Declaration) are decidely poor proxies, both because of the great amount of time between these statements and the 2007 AR4 report and because neither addresses attribution in any meaningful way but rather objects to the assumption of “catastrophic” impacts from the ongoing warming. So in a sense both Pielke Jr and GAvin and Eric are right. The paper purports it’s classification syste as being about science but really it is about politics.

    Relative to Pielke Sr.’s comments above, it sems crazy to me to so quickly dismiss his position as unoriginal or that it suggest that only option 2B applies. It is very clear from the Anderegg et al paper that they were attempting to gauge agreement with option 2B from both the clear language in the paper and any other position was treated as Unconvinced by the evidence (ie. a skeptic, denier or contrarian). In my mind, I continue to be baffled by the AGW mainstream’s position when Pielke Sr.’s position (i.e., Yes, there is significant anthropogenic impact on climate, but it is due to more than just GHG) intuitively makes so much sense.

    [Response: To use an overused metaphor, you are basically asking “Do you still beat your wife, sir?”. The point is that the “AGW” mainstream (at least, as represented by the IPCC) is not in conflict with Pielke’s position, at least not the way it is expressed by you. As I note above the real problem with his position is that it is a false dicotomy. Both 2a and 2b are correct depending on what part of the system you are talking about. Pielke Sr. makes it sound like the ‘mainstream’ is missing something when they aren’t. Hence the definition of a loaded question: one that presupposes something that has not been proven or accepted by all the people involved. If Pielke Sr. gets classified as a skeptic, or contrarian, or whatever, it is due to this sort of misleading rhetoric. It may not purposefully intend to mislead, but it is misleading nevertheless, and in quite substantive ways (because it implies that the mainstream view that we probably ought to cut CO2 emissions is based on faulty science). Note, however, this none of this has anything to do with Anderegg et al., except that, if in fact he gets classified as a ‘denier’ in their analysis, this is probably why. –eric]

  50. 50

    Hypothesis 2c: The human influences now dwarf natural influences and are dominated by the emissions into the atmosphere of greenhouse gases, the most important of which is CO2. God help us if the developing world decides to reduce aerosols that are likely masking the true underlying GHG-induced warming. The adverse impact of GHGs on regional and global climate is the single most important issue facing humanity this century.

    Just keeping it real.

    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