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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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The 97% consensus on global warming

What the science says...

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97% of climate experts agree humans are causing global warming.

Climate Myth...

There is no consensus

The Petition Project features over 31,000 scientists signing the petition stating "There is no convincing scientific evidence that human release of carbon dioxide will, in the forseeable future, cause catastrophic heating of the Earth's atmosphere ...". (Petition Project)

Science achieves a consensus when scientists stop arguing.  When a question is first asked – like ‘what would happen if we put a load more CO2 in the atmosphere?’ – there may be many hypotheses about cause and effect. Over a period of time, each idea is tested and retested – the processes of the scientific method – because all scientists know that reputation and kudos go to those who find the right answer (and everyone else becomes an irrelevant footnote in the history of science).  Nearly all hypotheses will fall by the wayside during this testing period, because only one is going to answer the question properly, without leaving all kinds of odd dangling bits that don’t quite add up. Bad theories are usually rather untidy.

But the testing period must come to an end. Gradually, the focus of investigation narrows down to those avenues that continue to make sense, that still add up, and quite often a good theory will reveal additional answers, or make powerful predictions, that add substance to the theory.

So a consensus in science is different from a political one. There is no vote. Scientists just give up arguing because the sheer weight of consistent evidence is too compelling, the tide too strong to swim against any longer. Scientists change their minds on the basis of the evidence, and a consensus emerges over time. Not only do scientists stop arguing, they also start relying on each other's work. All science depends on that which precedes it, and when one scientist builds on the work of another, he acknowledges the work of others through citations. The work that forms the foundation of climate change science is cited with great frequency by many other scientists, demonstrating that the theory is widely accepted - and relied upon.

In the scientific field of climate studies – which is informed by many different disciplines – the consensus is demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them.

Authors of seven climate consensus studies — including Naomi OreskesPeter DoranWilliam AndereggBart VerheggenEd MaibachJ. Stuart Carlton, and John Cook — co-authored a paper that should settle this question once and for all. The two key conclusions from the paper are:

1) Depending on exactly how you measure the expert consensus, it’s somewhere between 90% and 100% that agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists.

2) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming.

consensus studies

Expert consensus results on the question of human-caused global warming among the previous studies published by the co-authors of Cook et al. (2016). Illustration: John Cook.  Available on the SkS Graphics page

consensus vs expertise

Scientific consensus on human-caused global warming as compared to the expertise of the surveyed sample. There’s a strong correlation between consensus and climate science expertise. Illustration: John Cook. Available on the SkS Graphics page

Expert consensus is a powerful thing. People know we don’t have the time or capacity to learn about everything, and so we frequently defer to the conclusions of experts. It’s why we visit doctors when we’re ill. The same is true of climate change: most people defer to the expert consensus of climate scientists. Crucially, as we note in our paper:

Public perception of the scientific consensus has been found to be a gateway belief, affecting other climate beliefs and attitudes including policy support.

That’s why those who oppose taking action to curb climate change have engaged in a misinformation campaign to deny the existence of the expert consensus. They’ve been largely successful, as the public badly underestimate the expert consensus, in what we call the “consensus gap.” Only 16% of Americans realize that the consensus is above 90%.

Lead author John Cook explaining the team’s 2016 consensus paper.


Last updated on 8 May 2016 by BaerbelW. View Archives

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Further reading

Richard Black at the BBC investigates whether there is a bias against skepticism in the scientific community.

More on what we're talking about when we say "scientific consensus,"  in an essay founded on Denial101x and scientific literature: Scientific Consensus isn’t a “Part” of the Scientific Method: it’s a Consequence of it. (or via

Further viewing

The "Climate Denial Crock of the Week" video series examines the list of "32,000 leading skeptical scientists."

Naomi Oreskes gives a thorough presentation of the development of our scientific understanding of anthropogenic global warming:

Here is a video summary of the various studies quantifying the scientific consensus on human-caused global warming, as well as the misinformation campaigns casting doubt on the consensus.


Many thanks to Joe Crouch for his efforts in tracking down scientific organizations endorsing the consensus as well as links to their public statements.


On 21 Jan 2012, we revised 'the skeptic argument' with a minor quote formatting correction.


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Comments 651 to 675 out of 906:

  1. The Forbes story amhartley asked about @650 is rather strong in its assertions. It asserts that Cook et al (2013) involves "egregious misconduct" and was "a deliberate misrepresentation designed to intimidate the public." These claims are backed up by a mis-description of the Cook et al method and the comments of some well-known scientists - Richard Tol, Craig Idso, Nicola Scafetta and Dr. Nir Shaviv, this last one being a not-so-well-known climate change denier compared with the other three.


    [JH] The author of the Forbes article is Alex Epstein, founder of the Center for Industrial Progress and author of The Moral Case for Fossil Fuels. As a Forbers contributor, Epstein states, "I write about the environmental benefits of industrial progress." I guess we know which side his bread is buttered.

  2. Thanks, MA Rodger & JH, for the input. I had a hunch Epstein was himself misrepresenting things, but as a statistician—rather than a climate scientist--I might not be able to debunk all of his claims. However, if the experts at SKS were to publish, routinely, rebuttals of claims like those, I can imagine those rebuttals could help others like me to both understand the truth & communicate it more widely.

  3. amhartley @652, there are several rebutals of various denier talking points regarding Cook et al 2012.  This is the most general, but this one is also worth looking up. 

  4. That helps, Tom.

    In fairness to Forbes, it is good to see them publishing a pro-environment perspective, too:

  5. Climathulu?

  6. The Global Warming Petition Project is straight from the department of "Lies, damned lies, and statistics."  On second thought, "damned lies" may be laying it on too thick. Their vaunted number of scientific supporters is so pitifully small, it's barely worth calling a silly fib. But since one hears their figure quoted so often by climate change deniers, let's break down the numbers, just for fun. 

    The signers of the Global Warming Petition number 31,487, all of whom are claimed to hold at least BS "or equivalent" degrees. (GWPP : Qualifications of signers)

    9,029 hold PhD degrees
    11,615 hold PhD &/or MD or DVM degrees
    18,772 hold MS or higher degrees
    31,487 hold BS or equivalent &/or higher degrees

    The American population at large, aged 25 years or older, is around 203 million. Of these:

    3.6 million (1.77%) hold PhD degrees
    7.5 million (3.27%) hold PhD &/or professional degrees
    25 million (11.8%) hold Master's &/or higher degrees
    65 million (32%) hold Bachelor's &/or higher degrees

    (Educational attainments of Americans — USCB/Wikipedia)

    Thus, the signers of the GWP represent the following percentages of each category:

    PhD degrees — 0.25%
    PhD &/or professional degrees — 0.15%
    Masters &/or higher degrees — 0.08%
    Bachelor's &/or higher degrees — 0.05%

    Obviously, these levels are vanishingly small. The GWPP’s horizon of expertise recedes even further when we consider that only 3,805 of these people claim any qualifications in Atmosphere, Earth, and Environment sciences. Granting all of them the unlikely distinction of holding doctorates, they would still represent only 0.11% of PhDs. (More realistically, they make up 0.006% of the population with a Bachelor's or better.)  But just sticking with PhDs as a whole, I would venture to guess there is not a single area of scientific study, not a single theory, not a single assertion for which one could not muster a level of dissent of 0.25%--not excluding excluding that the Earth orbits the Sun; or that the Moon is composed of rocks, not Roquefort.  

  7. Advance apologies if this question has been asked and answered many times. I just discovered the site while searching for the source of the oft-quoted 97% consensus and was disconcerted to read that the consensus refers to 97% of the 33% of authors who stated a position on human-caused warming, while the remainding two-thirds made no finding as to cause. The reality, then, is that twice as many climate researchers do not agree that gw is human-caused, do not know, or are unwilling to take a position.  I read one comment here that seemed to say that the 66% didn't  need to state an opinion because it is so obviously human-caused - the "everyone knows" argument. This wouldn't be acceptable in a courtroom or a school science project so I hope it is not the case.

    Many non-scientists are bewildered by the volume of conflicting information on this subject, by fuzzy numbers and apparently authoritative statements that amount to gobbledegook when subjected to rigorous analysis. Anyone?

  8. "while the remainding two-thirds made no finding as to cause."

    That's not quite accurate. Itd be accurate to say that those two-thirds made no statement of attribution in the abstract. That's not surprising, most climate science does not involve quantifying attribution.

  9. wakeup @657.

    You say:-

    "Many non-scientists are bewildered by the volume of conflicting information on this subject, by fuzzy numbers and apparently authoritative statements that amount to gobbledegook when subjected to rigorous analysis. Anyone?"

    The volume of 'conflicting information' and the 'fuzzy numbers' may be less easy to get you to identify, but please do give your examples of 'apparently authoritative statements that amount to gobbledegook'. It is difficult for anyone to begin to address your question without knowing what you're on about.

  10. wakeup - When you write a paper, you don't waste time rediscovering gravity, or that the sky is blue, or Archimedes Principle. You spend your time on new work and how that relates to previous hypotheses. The more accepted something is as a background fact the less you will see it explicitly discussed in a paper. It would therefore be reasonable to include the 2/3 of papers not bothering to mention GW causes as agreeing with the consensus - not doing so is a conservative choice minimizing actual agreements. 

    If, on the other hand, your work disagrees with the consensus, with accepted background material, you're going to mention that and state why, whether you consider that background material to your work or central to the paper. Meaning that we should expect a higher percentage of attribution in minority papers on climate, a higher percentage of implicit or explicit claims of dominant natural causes in 'skeptic' papers, an overrepresentation of dissention.

    And yet even with that potential overrepresentation, papers arguing against AGW still come in at less than 3% of the papers mentioning causes of climate change. 

  11. wakeup, let's consider some different scenarios;

    • If you look at all climate papers which stated causes of GW then ~97% said GW is mostly human caused.
    • If you look at all climate papers then ~33% said GW is mostly human caused.
    • If you look at all scientific papers then less than 1% said GW is mostly human caused.
    • If you look at all papers on any subject (e.g. economics, philosophy, knitting) then near 0% said GW is mostly human caused.
    • If you look at all written communication throughout human history then near 0% stated a position on any given single topic.

    People who are not trying to kill their own capacity for rational thought should be able to see that looking at anything other than the percentage amongst those who actually addressed the issue (i.e. 97%) is meaningless. The only reason to favor a percentage including some pool of data which doesn't even address the subject is to deliberately delude oneself.

  12. The case is actually stronger, if I recall correctly.  The 3% of publications addressing the human contribution are not actually comprehensive.  If we were to include only studies that determine the contributions of the full range of natural and anthro forcings, feedbacks, and oscillations, the number would not be 97%.  It would be 100%.

  13. Hello all,

    Is anyone aware of a similar study in which authors were allowed to rate their studies as "inconclusive"?  Given that this study asked authors to rate studies without the option to mark as inconclusive, I was just curious.

  14. mav1234,

    Read the advanced or intermediate tabs of the OP.  All the studies allow the papers to be rated inconclusive.  Cook had 7 ratings.  Many of the papers were rated inconclusive.  

    Where did you get the idea that inconclusive was not a choice??  If you believe the "skeptic" blogs you will never understand the issues.  Their primary purpose is to put out disinformation.

  15. michael sweet @664, in Cook et al, self raters were not given an "inconclusive" option.  Rather they were given a neutral option, without the possibility of distinguishing between "neutral because inconclusive" and "neutral because relevant issues were not addressed".  The distinction is important because the former, but not the later, should be included in the denominator in determining the proportion of endorsements.

    In the abstract rating section of the paper, a subsample of neutral papers were given a secondary rating to distinguish between "neutral because inconclusive" and "neutral because not addressed".  Only 0.1% of neutral papers fell into the former category.  Assuming that a similar proportion of papers self rated as neutral were "neutral because inconclusive", then 96.7% of self rated papers that had an opinion on the topic would have been self rated as endorsing AGW.  That compares to the 97.2% found in the actual paper without the option of distinguishing reasons for the neutral rating.

  16. Tristan: Thanks for responding. At issue is whether or not global warming is human-caused. If the goal was to find out if a significant majority of scientists publishing in the field support the theory, it's unusual, to say the least, to discard 66% of the subject papers because they "made no statement of attribution" and treat the 34% who do as 100% to reach the conclusion that 97% validate the theory of human causation.

    That would be fine if the 97% is declared for what it is: the percentage of the 34% of experts who have reached a conclusion, as it is (if you know to look for it) in the Science Project logo above. Unfortunately it is used daily to convince the public that 97% of climate change scientists agree that gw is human-caused, which, in my view, is not demonstrated by this survey.

  17. wakeup @666, thankyou for opening my eyes.  I had not realized the theory that the Earth is not flat was in so much difficulty.  However, following your methods, I noted that there is virtually zero endorsement of the proposition that the Earth is a sphere (or oblate spheroid) in scientific papers.  It follows, from your impeccable reasoning, that >>99% of scientists do not accept that the Earth is either a sphere or an oblate speroid and that, by inference they consider the theory that the Earth is flat to be at least as viable.

  18. wakeup @666.

    If your comment @666 is the substance of your enquiry (although it is more assertion than enquiry), perhaps the example of Whiskas cat food advertising will demonstrate where you are missing the point.

    This is not to do with "whether or not global warming is human-caused" as you suggest @666. Rather it is to do with whether climate scientists agree it is human-caused. And they overwhelmingly do agree.

    The UK Whiskas cat food advert of the 1980s initially used the phrase "8 out of 10 cat owners said they cat preferred it." This was adjudged to be deceitful because there were many who didn't express a preference and were not included in the "10". Thus the adverts was changed to say "8 out of 10 cat owners who expressed a preference said their cat preferred it."

    Yet this still does not give the full story. How many cat owners (or more correctly cat feeders, because they are the ones in a position to know) responded that there was not a jot of difference between these various cat foods? It could be, say, that only a third could see any difference at all between premium cat food Whiskas and some budget moggy-snack.

    What you are suggesting @666 is that all the papers reviewed are like cat feeders and so these papers would all allow an answer to the enquiry and that in the majority of cases the papers show a response "Don't know" or in the Whiskas analogy "I see no difference." Yet what that majority( that you wish to include within the results of the analysis) are saying is the equivalent of "I don't know because I don't feed the cat."

    This explains why, contrary to your assertion,  the 97% figure "is (properly) demonstrated by this survey."

  19. wakeup - By your standards, then, every science paper should also explicitly state that the sky is blue, gravity exists, green is not purple, and in essence recapitulate the entire sum of human knowledge, because otherwise that's all clearly up for debate.

    Um, no.

    Every bit of science exists within the body of shared knowledge assumed as a background. It's only when a work rests on other assumptions that it's necessary to state those, in a minority opinion - the better accepted a bit of knowledge, the less you need to start it to the readers. Meaning that climate 'skeptic' papers need to establish their (different) assumptions, but mainstream works not so much.

    I suspect (personal opinion) you are fully aware of this, and are just looking for some semantic points to dismiss the consensus on AGW. That same argument has been raised before (read back in these threads), and it's still nonsense. 

  20. I find the line of reasoning from wakeup so tenuous and the conversation so vacuous that this is coming really close to a DNFTT situation.

  21. Well there are other ways to see whether Cook is on the right track. You can ask the climate scientists directly. That would be Doran 2009, which came up with the same figure. You could also look at all the scientists who contributed research surveyed by the IPCC - ie over 4500. By contrast wikipedia provides this helpful list of dissenters. Taking out the non-climate scientists and industry shills, you are left with a list of mostly scientists who have "gone emeritus" and/or are ideologues.

    Frankly, anyone who doesnt believe that a consensus exists is pursuing an elaborate exercise in fooling themselves and I would suspect them to be ideology and/or identity driven.

  22. michael sweet @664: Please re-read Cook et al and check the author survey sent - inconclusive was not a choice given to the authors of papers.  I believe it is clear from the methods and the nature of the subset of abstracts receiving a treatment of inconclusive that Cooke et al realized their error late in the process and thus were unable to completely correct for this. I do not doubt that the number of scientists publishing papers indicating they are unconvinced is very low, but I was hoping someone was aware of such a study.

    I am trying to find if anyone has quantified this in any way, that was all.  I am not attempting to dismiss the consensus on AGW.

  23. wakeup @666: This survey is not the only evidence used "daily" to suggest an overwhelming consensus among climate scientists, and in fact, it references several other studies that support that position. I agree there are limitations of this study (hence my question), but the consensus is pretty clear from other sources as well.

  24. wakeup, so you've moved from 'there is no consensus!' to 'consensus does not matter!'? Should we anticipate that once all the evidence showing the effects of perceived expert consensus on public acceptance is presented you will move on to 'overwhelming agreement amongst experts does not make it true!' and then once all the evidence showing that AGW is true is presented (and denial of each fact countered) to 'all this evidence must be faked by the evil scientist conspiracy!'... or can we just skip to, 'Hey look, there is a complete database of information on this site which gives detailed rebuttals to every nonsensical claim you can come up with. Why don't you read those and get back to us if you find any which haven't already been proven false?'

    As to civility, who was it that introduced themselves by throwing around phrases like, "This wouldn't be acceptable in a courtroom or a school science project", "volume of conflicting information", "fuzzy numbers", and "apparently authoritative statements that amount to gobbledegook"?


    [JH] wakeup's most recent comment constituted argumentative sloganeering and was therefore deleted.  

  25. Wakeup, it isn't beyond the capacity of scientists to explain, but you do have to do some of the work.  They're not going to knock on your door.  And you do have to learn, because the science gets complicated as we move away from the basics.  It took ~850 scientists three years to summarize the existing science.  They ended up with a 3000+ page report.


    [JH] wakeup's most recent comment constituted argumentative sloganeering and was therefore deleted. 

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