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The 5 characteristics of scientific denialism

Posted on 17 March 2010 by John Cook

A fascinating paper well worth reading is Denialism: what is it and how should scientists respond? (Diethelm & McKee 2009) (H/T to Jeremy Kemp for the heads-up). While the focus is on public health issues, it nevertheless establishes some useful general principles on the phenomenon of scientific denialism. A vivid example is the President of South Africa, Thabo Mbeki, who argued against the scientific consensus that HIV caused AIDS. This led to policies preventing thousands of HIV positive mothers in South Africa from receiving anti-retrovirals. It's estimated these policies led to the loss of more than 330,000 lives (Chigwedere 2008). Clearly the consequences of denying science can be dire, even fatal. 

The authors define denialism as "the employment of rhetorical arguments to give the appearance of legitimate debate where there is none, an approach that has the ultimate goal of rejecting a proposition on which a scientific consensus exists". They go on to identify 5 characteristics common to most forms of denialism, first suggested by Mark and Chris Hoofnagle:

  1. Conspiracy theories
    When the overwhelming body of scientific opinion believes something is true, the denialist won't admit scientists have independently studied the evidence to reach the same conclusion. Instead, they claim scientists are engaged in a complex and secretive conspiracy. The South African government of Thabo Mbeki was heavily influenced by conspiracy theorists claiming that HIV was not the cause of AIDS. When such fringe groups gain the ear of policy makers who cease to base their decisions on science-based evidence, the human impact can be disastrous.
  2. Fake experts
    These are individuals purporting to be experts but whose views are inconsistent with established knowledge. Fake experts have been used extensively by the tobacco industry who developed a strategy to recruit scientists who would counteract the growing evidence on the harmful effects of second-hand smoke. This tactic is often complemented by denigration of established experts, seeking to discredit their work. Tobacco denialists have frequently attacked Stanton Glantz, professor of medicine at the University of California, for his exposure of tobacco industry tactics, labelling his research 'junk science'.
  3. Cherry picking
    This involves selectively drawing on isolated papers that challenge the consensus to the neglect of the broader body of research. An example is a paper describing intestinal abnormalities in 12 children with autism, which suggested a possible link with immunization. This has been used extensively by campaigners against immunization, even though 10 of the paper’s 13 authors subsequently retracted the suggestion of an association.
  4. Impossible expectations of what research can deliver
    The tobacco company Philip Morris tried to promote a new standard for the conduct of epidemiological studies. These stricter guidelines would have invalidated in one sweep a large body of research on the health effects of cigarettes.
  5. Misrepresentation and logical fallacies
    Logical fallacies include the use of straw men, where the opposing argument is misrepresented, making it easier to refute. For example, the US Environmental Protection Agency (EPA) determined in 1992 that environmental tobacco smoke was carcinogenic. This was attacked as nothing less than a 'threat to the very core of democratic values and democratic public policy'.

Why is it important to define the tactics of denialism? Good faith discussion requires consideration of the full body of scientific evidence. This is difficult when confronted with rhetorical techniques which are designed to distort and distract. Identifying and publicly exposing these tactics are the first step in redirecting discussion back to a focus on the science.

This is not to say all global warming skeptic arguments employ denialist tactics. And it's certainly not advocating attacking peoples' motives. On the contrary, in most cases, focus on motives rather than methods is counterproductive. Here are some of the methods using denialist tactics in the climate debate: 

  1. Conspiracy theories
    Conspiracy theories have been growing in strength in recent months as personal attacks on climate scientists have intensified. In particular, there has been accusations of manipulation of temperature data with the result that "the surface temperature record is unreliable" has been the most popular argument over the last month. This is distracting people from the physical realities of global warming manifesting themselves all over the world. Arctic sea-ice loss is accelerating. Antarctic and Greenland ice sheets are losing ice mass at an accelerating rate. Spring is coming earlier each year. Animal breeding and migration are changing in response. Distribution of plants are shifting to higher elevations. Global sea level is rising. When one steps back to take in the full body of evidence, it overwhelmingly points to global warming.
  2. Fake experts
    A number of surveys and petitions have been published online, presenting lengthy numbers of scientists who reject man-made global warming. Close inspection of these lists show very few qualifications in climate science. On the contrary, a survey of climate scientists who actively publish climate research found that over 97% agree that human activity is significantly changing global temperature.
  3. Cherry picking
    This usually involves a focus on a single paper to the neglect of the rest of peer-review research. A recent example is the Lindzen-Choi paper that finds low climate sensitivity (around 0.5°C for doubled CO2). This neglects all the research using independent techniques studying different time periods that find our climate has high sensitivity (around 3°C for doubled CO2). This includes research using a similar approach to Lindzen-Choi but with more global coverage.
  4. Impossible expectations
    The uncertainties of climate models are often used as an excuse to reject any understanding that can come from climate models. Or worse, the uncertainty of climate models are used to reject all evidence of man-made global warming. This neglects the fact that there are multiple lines of empirical evidence that humans are causing global warming .
  5. Logical fallacies
    Strawmen arguments abound in the climate debate. Often have I heard skeptics argue "CO2 is not the only driver of climate" which every climate scientist in the world would wholeheartedly agree with. A consideration of all the evidence tells us there are a number of factors that drive climate but currently, CO2 is the dominant forcing and also the fastest rising. Logical fallacies such as "climate has changed before therefore current climate change must be natural" are the equivalent of arguing that lightning has started bushfires in the past, therefore no modern bushfire is ever started by arsonists.

Update 16 April 2012: Many thanks to Mark Hoofnagle for pointing out that the 5 characteristics of science denial didn't originate in Diethelm and McKee's paper but in an article written by Mark and Chris Hoofnagle. This is an article very worth reading for anyone interested in climate change and public discourse about science. Credit has been updated accordingly.

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Comments 151 to 155 out of 155:

  1. "JMurphy
    How is it a 'soft science' ? "

    Physics is physics. Climate science is "based" on physics (and other hard sciences), and there is nothing within climate science that can be inconsistent with these fundamentals.

    In order to structure a hard physical model with precision, you need to isolate all significant factors. Global climate is simply too complex to lend itself to this level of determinism. And there is nothing wrong with this fact except for the confusion created by those that cant understand this difference.
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  2. RSVP, Climate Science involves a lot more science than the use of models. There is lots of 'hard' science going into substantiating the present situation and the projected situations coming from models.
    But don't despair : there are lots of people out there improving the models all the time and I doubt if they would agree that they are ignoring or unable to consider all significant factors. What factors do you think they are missing or not working on, or do you think they should just give up because it's too difficult ?
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  3. I'm surprised that nobody mentioned David Brin's blog about this subject at:

    Also may I suggest that models of weather patterns and ocean currents are probably quite non-linear, so is it possible that small effects could have very large but, difficult to predict, consequences?
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  4. Earlier in this thread (e.g., here) I mentioned that several people have managed to do independent replications of the global mean surface temperature analysis using GHCN stations (i.e., replicate the results of GISSTEMP, HADCRU, etc.)

    Zeke Hausfather has helpfully compiled links to five of these analyses and has done some comparisons. Here is the 1880-present global land temperature trend in all the studies except those from Tamino and Clear Climate Code (the CCC one is so close to GISSTEMP that the two are more or less indistinguishable):

    Zeke also computed linear trends over various time intervals. Over the last three decades GISSTEMP has the lowest trend, NCDC has the highest trend, and all the "independent blog studies" show trends in the middle of the range.
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  5. And yet another entry in the do-it-yourself surface temperature programs! New ones seem to be popping up about one per week. Once again, the results closely match those from GISS, CRU, NCDC, and the other "amateur" analyses linked above.

    Here's a comparison of eight different versions:

    Not shown in that graph are results from Tamino (who's temporarily offline while moving) and Clear Climate Code (whose results are identical to GISSTEMP).

    What does this comparison show?

    (1) The increasing global mean surface temperature trend is not caused by "manipulation" of the data by NASA or UEA-CRU.

    (2) The increasing global mean surface temperature trend is not an artifact of particular algorithms or methods (multiple studies using the same input data but different methods get the same results).

    (3) Several of these people have now done comparisons of stations that were dropped in the 1990s vs those that were not dropped, and have found no significant difference in the trends. (I.e., Watts and D'Aleo are clearly wrong.)

    (4) "Amateurs" (no insult intended; these people are highly skilled ... but climate science is an avocation rather than vocation for them) can make a very substantial contribution to the field. IMHO this is pretty neat.
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  6. I'm not entirely certain where to post this, but this thread seems like a reasonable spot.

    There's a very interesting article in Mother Jones, The Science of Why We Don't Believe Science, by Chris Mooney. This discusses studies on confirmation bias, differing evaluations of legitimate authorities to listen to, etc.

    Based upon world view and personal orientations: "... people rejected the validity of a scientific source because its conclusion contradicted their deeply held views—and thus the relative risks inherent in each scenario." This holds for both left and right wing politics, individualists and hierarchical thinkers.

    World views are akin to religions - they form a framework into which people cast their self-image. Anything perceived as an attack on that world view is emotionally interpreted as a personal attack; only later do rationalizations and (possibly) reason enter into the picture once that's begun.

    One of the take home items from this article is: "If you want someone to accept new evidence, make sure to present it to them in a context that doesn't trigger a defensive, emotional reaction. ... You lead with the values—so as to give the facts a fighting chance."

    Something to think about...
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  7. 156, KR,

    Interesting. The latest issue of Scientific American (a once reasonable bridge for the scientifically-literate-but-time-limited, now dumbed down to a cursory high school level) has a similar article (an opinion piece) titled Trust Me, I'm a Scientist.

    I just yesterday posted a whimsical contrasting view of my own: It's Magic.
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  8. This is an interesting article. I am not inclined to believe that conservatives and liberals differ fundamentally (or at last not monolithically) in their ability to accept science. Conservatives were, for example, at one point very important in the US conservation movement, the EPA etc.

    What's clear is that climate science is currently caught in a larger political narrative at present that largely swamps the scientific narrative. That's one reason most scientists won't participate in this debate -- they don't have a clue what the script is and they're aware enough to realize it. It's like that nightmare when you find yourself on a stage acting in a play and you have no idea how to respond to the cue someone feeds you because suddenly the play has changed. It goes both ways, non-scientists exposed to the scientific narrative can't recognize the storyline and are immediately lost when confronted with the reams of literature out there. So they retreat into the narative they're comfortable with, which looks something like they see on ESPN...two teams banging it out.

    It does seem that the modern Republican Party (of the last couple decades) has shifted to an outright rejection of science as a mediating influence over policy. Personally, I think this shift is related to the adoption of PR mechanisms borrowed from marketing, which explicitly work on the native tendencies Chris Mooney is writing about. Such methods require messages that are simple to deliver and that target people's sense of identity. Nuance is not an advantage, so science becomes a hindrance really. Eventually, it's just been left out altogether so as to fashion efficient messages implying threat from some anonymous group or another. The circling of the wagons - the brand loyalty, if you will - that results is a real firewall against big losses politically. If those in the wagons have cash, all the better for the party in question - especially now that money is equated to speech in the US!

    It's a very rational to adopt such an approach from the point of view of politics. Of course, nature could care less what works in politics. I'd argue that undercutting science as the Republicans are doing is ultimately very bad for the very business interests they claim to support.
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  9. Thanks for the attribution on the tactics, however, it should be noted though that Diethelm and McKee used our definition of denialism as well.
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  10. IMO there are two additional characteristics of scientific denialism which do not necessarily fit in the characteristics described here in the OP or over at Denialism blog:

    Misrepresentation: Denialists tend to misrepresent - whether ignorantly, inadvertently, or intentionally - the scientific literature as well as the statements and positions of scientists, scientific bodies, and other advocates (individuals or groups) supporting the mainstream/consensus position.

    Such misrepresentations are made in the service of almost every other characteristic of denialism, which is why I would promote them to a separate characteristic.

    - misrepresentation of the content of the hacked UEA-CRU emails is undertaken to reinforce the accusations of conspiracy/hoax/what-have-you
    - misrepresentation of credentials is used by denialists to reinforce their acceptance of fake experts (e.g. Monckton's claims regarding the House of Lords or the Nobel prize)
    - cherry-picked papers are often misrepresented as stating some conclusion not related to, or out of line from, or even in diametric opposition to, what they actually say (e.g. the recent paper regarding Medieval Climate Anomaly at Antarctic sites, Monckton on Greenland ice, Forbes magazine's blowing Spencer & Braswell 2011 out of proportion)
    - the misrepresentation of climate science's basis being solely dependent on models is a necessity for setting up impossible expectations/shifting goalposts, as is the misrepresentation of historical denialism (e.g. claims that "skeptics" have never denied warming, or that CO2 causes warming, or the like)
    - most obviously, misrepresentations are often crucial components of typical logical fallacies such as ad hominem arguments, appeals to emotion, false equivalencies, and straw men arguments
    - related to my other suggested characteristic, below, the continuous use of misrepresentation creates an environment in which denialist claims can be accepted with undue credulity.

    Credulity: Denialists tend to accept - and propagate - with unseeming credulousness claims made against the body of mainstream climate science, or against scientists or advocates espousing mainstream climate science, or even against the physics underpinning mainstream climate science.

    Such credulity extends to accepting claims made on the basis of poor physics (e.g the typical crank claim that the atmospheric heat-trapping effect violates the laws of thermodynamics or other stuff routinely discussed @ Science of Doom), poor statistics (e.g. the material routinely debunked by Tamino), long-ago-refuted or dismissed material (e.g. claims that the heat-trapping effect of CO2 is saturated) or even self-contradicting sets of claims (as documented elsewhere here on Skeptical Science.

    As with misrepresentation, credulity is such a key component of other characteristics of denialism that IMO it deserves to be a characteristic of its own. Also, suffice to say, the credulity required to engage in denialism puts paid to the self-identification of denialists and contrarians as reasonable skeptics.

    - Many claims of conspiracy (such as suggesting peer review == theocracy, or claiming the resignation of the editor-in-chief of Remote Sensing over Spencer & Braswell 2011 was evidence of the IPCC 'clique' at work) require a rather credulous mindset - indeed, accepting the existence of a vast conspiracy comprising thousands of scientists across the world, the IPCC, every major scientific academy and almost every major scientific organization requires a very credulous mindset
    - I submit that it takes a great deal of credulity to accept the likes of Anthony Watts, Christopher Monckton, or Fred Singer, as superior authorities to the IPCC, the NAS, and notable climate scientists
    - Since most cherry-picking is obvious once the cherry-picked source or information is examined on its own terms or in reference to the literature, some degree of credulity is required to accept cherry-picked claims without further investigation (which is what the cherry-pickers are hoping for, of course)
    - Accepting that climate science must meet unachievable hurdles of evidentiary support before informing policy, compelling action, or being accepted as "real" science, when compared to the evidentiary support it actually has or compared to the evidentiary support for other scientific disciplines which inform policy-making or personal/societal action, again, requires credulity
    - Creduility required to accept fallacious logical arguments? Check
    - With regards to the additional characteristic suggested above, denialist credulity in climate science allows the unquestioned acceptance of various misrepresentations, however blatant.
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  11. The important thing to remember with the "The 5 characteristics of scientific denialism" is that all five characteristics can be equally applied to people on both sides of the argument.

    Denialism (or 'repudiation' to use the correct English term) is absolutely essential to the advancement of knowledge. All the great discoveries were made by individuals repudiating the scientific consensus fashionable at the time.
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  12. Justin - your comment falls under characteristic No.5, the logical fallacy. More specifically, you have put forth the argument of false equivalence. Can you provide one example where a mountain of congruent scientific evidence, like climate science today, has been overturned by an individual, or group, that doesn't even have a competing hypothesis?
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  13. Justin:

    Denialism is set squarely against the advancement of scientific knowledge and against innovation.

    Who are antivaccine denialists, AIDS/HIV denialists, germ theory denialists? They're homeopaths, chiropractors, holistic healers, reiki masters, and the like. They're the parents of autistic children asserting vaccines caused their childrens' autism and then resorting to bleach baths & enemas or industrial chelation to try to 'treat' it. They're the people claiming cancer is caused by liver flukes (Hulda Clark) or "acidity" (Robert Young). What they are not is furthering our understanding of immunology, virology, bacteriology, microbiology, and biochemistry.

    Likewise, young-earth creationists (engaged in denialism of geology & evolutionary biology) aren't the ones furthering our understanding of genetic evolutionary mechanisms or geological processes or paleontology.

    Suffice it to say, the suggestion that denialism is at all associated with scientific advancement is IMO unequivocally false.
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  14. In "Update 16 April 2012" at article's end, the link to "article written by Mark and Chris Hoofnagle" is incorrect (

    and should be

    as it is given for the phrase "first suggested by Mark and Chris Hoofnagle" at the end of the article's second paragraph.
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  15. I've spoken on this topic and done a lot of writing and debating on it. I think two thinks should be added:

    (6) Resorts to "magic bullet" arguments, erroneously believing an entire scientific theory can be unwoven with a single piece of evidence.

    (7) Resorts to a "I'm not saying X; I'm just a guy with some questions" position... (see Joe Rogan vs. Phil Plait) but does not actively seek answers for these questions or supply an alternate hypothesis which explains as much of the evidence as the existing theory does.
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