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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 351 to 375 out of 908:

  1. Earlier today I had a discussion with a person who described himself a "skeptic", not a denier concerning scientific consensus on ACC. His stance was that there is no consensus among climate scientists that the current climate change was due to human causes. Of course, I directed them to Anderegg 2010, Doran 2009 and Oreskes 2004; but he kept coming back with the statement, "there are climate scientists who do not believe there is a consensus among climate scientists". I kept trying to explain that yes, there are climate scientists that disagree with the consensus, but not that there is no consensus. Are there actually any practicing climate scientists that disagree that there is a consensus?
  2. Hey everyone, A climate skeptic sent me to these websites as proof that climate change is not happening and there is no scientific consensus. Help me in arguing back? Cheers, Michael.
  3. 355, mik_rosser, [snipped uncalled-for harsh reply] For information, just use the search function on this site. Searches for the following will give you more than enough ammunition to thoroughly refute each of those 1,000 times over (not to mention this very post on the consensus): climategate peer review pop tech
  4. 354, RickG, You can find climate scientists that believe that smoking does not cause cancer, and that the theory of evolution is false, so I imagine you can certainly find a few that will even claim that there is no consensus. But let me get this straight... their argument is that there is no consensus on climate change, because there is no 100% consensus on whether or not there is a consensus on climate change? Do they drink from the "Drink Me" bottle or eat the "Eat Me" cake, or both, in their special little wonderland?
  5. mik_rosser @355: Peer Review: The process of peer review if properly adhered to means that every paper published in a scientific journal has been read carefully by at least two people reasonably expert in the field, who have been able to convince a third person who is capable of understanding the argument (the editor) that: a) It contains no obvious errors; and that b) It is written well enough that somebody who wants to could reproduce the procedures and analysis used; and that c) It takes proper account of relevant scientific literature. The process is onerous, but it sets a very low bar. It requires you to convince just three people who know what they are talking about that the paper is not an obvious blunder. That does not show that the paper is not false, or that it is worthwhile or anything like that. Only that it probably does not contain an obvious blunder. The peer review process does not always work, either because reviewers miss obvious blunders (they are human and do make mistakes), or more frequently, because people with bizzare theories game the system by approaching an editor known to by sympathetic to their cause, who will shepherd the paper through to publication without proper peer review. Even creationist papers have been shepherded through in that way, and several "climate skeptic papers" which were obviously flawed have been shepherded through that way. In addition, a large number of papers, some by "skeptics", but many not, have been published which simply do not have the implications "skeptics" attach to them. In many cases, the supposed implications as stated by "skeptics" are directly contradicted by the paper itself, and a large number of scientists have complained about misrepresentation of their papers by "skeptics". Consequently I would take Poptech's list with a very large grain of salt. Because of this tendency of so-called "skeptics" to outright misrepresent the nature of research, many defenders of climate science including myself think a more appropriate label for them is "AGW deniers", in that they are not behaving skeptically, and because they are denying the descriptor of "skeptical" to the many climate scientists who do behave skeptically. However, the crucial point about peer reviewed publication is that it is just a first hurdle for science, and a very low one. It is, however, one that "skeptic's" arguments repeatedly come a cropper on. The simple test of convincing just three reasonably informed people that your argument does not contain obvious blunders is too difficult a challenge for most "skeptics" to meet. As a result they take their arguments to the internet, and to conventions organised by conservative think tanks, and to talk back radio shows. In other words, being unable to persuade even a few well informed people trained in scientific analysis, they take their arguments to people who are neither well informed, nor trained in scientific analysis. That shows clearly their agenda. If their agenda was the advance of knowledge, there would be no substitute for convincing the scientific community. I know of a number of controversial theories which do no have a scientific consensus, but whose adherents repeatedly try to break through the peer reviewed barrier and to convince scientists. That is because they believe their theory is true, and that truth matters. Consequently they think their theory can, and should face the most rigorous test possible. In contrast, AGW deniers have no such confidence or belief. What is important to them is not the truth of their theories, but the political effect of wide spread acceptance of their theories. They are playing a political game - not doing science. It is for that reason that (with rare exceptions) they give an uncritical pass to the egregious lies of some of their number, while straining at fleas in actual climate science. Finally, peer reviewed publication is just the first hurdle of peer review. After publication, papers are read by a very large number of scientists who can analyse the arguments and decide whether they are good, and well supported by evidence; largely irrelevant; or outright bad. The outright bad, ie, almost certainly false papers attract a small number of citations as scientist publish refutations. The irrelevant papers attract almost no citations as people ignore the paper. The good papers attract a large number of citations as people repeatedly reference the result in their own papers. Initial peer review is only a test to see if the paper contains an obvious blunder; citations are the true mark of a worthwhile paper. In that are, "skeptic papers" fare very poorly.
  6. mik_rosser @355: Consensus: I think there are two important things to understand about consensus and climate change. The first and most important is that arguments about consensus are not an argument from authority, it is an argument about who is an authority. It is an unfortunate fact of life that most things that we "know" we accept on authority. It can hardly be any other way - there is simply to much to learn, and to much to analyse for anybody to have more than a passing understanding of more than a small range of topics. Even in those topics where we claim some expertise, most of what we know we know on authority because we have not done the experiments or made the observations ourselves. To give just one example, how do I know that man has ever trod on the moon? The answer is, on authority. I was not on any trip to the moon, nor part of the effort to get man there. I have not myself seen footprints on the moon. Consequently, at some level I must accept the theory that man has walked on the moon on authority. There are those who do not accept that theory, who dispute the claims of those who could actually check for themselves (such as Neil Armstrong and Buzz Aldrin). I can, and have, looked at the evidence the lunar landing deniers present, and see that their claims are unsupported. That means I can show that they do not have a reason to believe the various films of men walking on the moon are doctored, or staged. But what I can't do is prove that they were not doctored or staged because there is no in-principle limit on how well such doctoring or staging can be done. At some point I just have to trust that the films are not fakes - but when I do, I am accepting something on authority. Now, it is obviously best to rely as little on authority as you can, especially in matters of importance. In climate science, if you don't want to rely on authority at all, you first need to get yourself a PhD in physics, making sure you are well qualified in programming and statistics. You then need to read carefully around a thousand scientific papers. That's less than a quarter of all the relevant papers, but it should get you up to speed. You then need to start a major program of experimentation that will require an annual budget of millions to sustain. Even then you will need to accept the authority of various space agencies to make use of satellite data. But you will probably then be in as good a position as anyone to not rely on authority at all in your beliefs about climate change. Of course, not everyone in the population is going to do that. Indeed, only a tiny fraction of the population will undertake the limited measure or reading multiple books, about 100 scientific papers, and several excellent essays need to become, not expert, but moderately competent in understanding the arguments about global warming. Consequently, most people will have to accept most of what they believe about global warming on authority. If anybody ever tells you different, they are lying to you*. Not only are most people going to have to accept most of what they believe about global warming on authority, it is vital that most people actually have an opinion about global warming. This is because we live in a democracy, and there is not substitute for democracy as legitimate government. Given the risks involved, is is therefore vital that people have informed opinions about global warming. But to do that, they must accept much on authority. So the essential issue for most people is this: Whose authority do you accept? So called "climate change skeptics" claim that they are the authority that you should listen to. They say that they are scientists (and some of them are); and that they have studied the issue (and some of them have even done that); and the implicit claim is that you should accept them as your authority. I disagree. If you are not very well informed on a subject, and do not intend to become so, the only rational choice is to accept on authority the consensus opinion of the people who are most informed, and who have studied the issue most closely. Recently Lord Monckton described this as a "fascist point of view", but to me it is just common sense. So common that we govern our lives by it for almost every major decision, whether that be what medicines to take, and when, or what foods to consider safe. In fact, for all their posturing, the so-called "climate skeptics" recognise that this is rational approach. They recognise it by continuously portraying the actual scientific consensus as being smaller than it is; as being perhaps a small majority at most rather than the over whelming majority that it is; and portraying there numbers as being much larger than they actually are by misleading comparisons. They compare, for example, the total number of scientists involved in the IPCC (which they drastically and deceitfully understate) with a list of "scientists" by which they mean anyone with a medical or engineering degree a if that where the appropriate comparison. In fact, comparing like with like, deniers make up around 3% of actively publishing (and hence researching) scientists of any type, and just 1% of actively publishing climate scientists. But they want you to ignore the reasoning and evidence that has raised acceptance of AGW among climate scientists from around 40% two decades ago to around 97% today. The argument from consensus points out that ignoring that evidence is not a reasonable thing to do. So, while I definitely encourage anyone interested to become genuinely familiar with the science of climate change (which is fascinating in its own right), if you are not willing to do so, don't be conned into accepting a false authority by inaccurate comparisons with Galileo. * Lord Monckton actually begins his seminars by saying he will not ask anyone to accept anything on authority. He then proceeds to tell whopper after whopper secure in the knowledge that most of his audience won't check. In other words, he is banking on their accepting his authority, and the disclaimer is a sham. This is a common tactic among deniers, and is equivalent to the "cockroach trap" mail order scam. In that scam a cockroach trap is advertised with a money back guarantee. It turns out the "trap" is just two bricks and instructions to bang them together with the cockroach between. The business is legit in that the money is give back to those who apply, but the scammers make a fortune because most people don't make the effort.
  7. Sorry, forgot to cover the important thing, but two essays is enough or one day. Very briefly, it is the nature of the IPCC consensus. The positions taken by the IPCC are the position that nearly all scientists have least disagreement with. Some might disagree significantly with some points, but an equal number will disagree just as much in the opposite direction. A rough measure the level of disagreement is the statement of the likelihood of the claim (which should be paid careful attention to.) If something is considered very likely, there is very little disagreement, and those who disagree do not disagree by much. If something is "more likely than not" then there is wide disagreement, but the IPCC position is still the position from which there is least disagreement.
  8. Anyone reviewing this site that assigns a percentage for each chapter and working group of the IPCC? No
  9. PS: It seems to be getting promoted out there in the Denialosphere, and has a 'score card' in which this photographer somehow rates the % of peer-review for each chapter of the IPCC report.
  10. It is nonsense. Indeed, it is OBVIOUSLY nonsense. The first massive flaw in their methodology which I noticed is that they treated every reference in the IPCC reports as a 'scientific reference' with which to dispute the IPCC claim that its scientific findings were based solely on peer reviewed research. Thus, reports on progress of various countries towards meeting the Kyoto targets, economic impact estimates, and even citations of objections from 'skeptics' (e.g. Bjorn Lomborg's book 'Global Crises, Global Solutions') are counted against the IPCC's 'score'. In short, no effort whatsoever was made to review WHAT the citation referred to in the text or whether it had anything to do with the case for AGW. The second ridiculous flaw is that their determination of whether something was peer-reviewed or not was entirely based on whether an obvious scientific journal was cited in the reference. Thus, for instance, dozens of references citing "Cambridge University Press" were marked as NOT peer reviewed... demonstrating that no attempt whatsoever was made to track down any of these papers - which appeared in the multiple peer reviewed academic journals which Cambridge publishes. Ditto various other major universities. Ditto anything in the references which people with no apparent knowledge of academic publishing did not immediately recognize as a peer reviewed journal. In short, the 'grades' they present do NOT measure the accuracy of the IPCC's claim that its scientific findings are based on peer reviewed research. Rather, they are measuring the percentages of references on any subject in the IPCC reports which they could determine to be peer reviewed with a cursory inspection by people who don't know what they are doing. A meaningless statistic... which they get completely wrong.
  11. Eclipse @10, I just reviewed the Working Group III references, only to find that CBDunkerson has stolen my thunder with an excellent response. I will add to his points just three more: First, in order to get the "failing grade", the "No consensus" website has obviously had to include as "grey literature" sources as diverse as IPCC reports, the Stern Review, papers presented at academic conferences, and chapters of books by reputed academic publishing houses. While many of these sources have not been through a standard journal type peer review, there is no doubt that they have been extensively reviewed to a far more rigorous standard than would be implied by such peer review. In other words, their ideosyncratic standard of "peer reviewed" is artificially restricted, and exclude much material of the highest academic quality. Second, even with this highly artificial standard, the Working Group 1 chapters nearly all get an A, with only two falling below that standard to get a B. Based on that assessment, if they took their own measure seriously, they would not question the essential results of WG 1. Clearly they do not do that, which reveals what a hypocritical exercise they are indulging in. Three, what is entirely absent is any assessment using their standard of the work of deniers. That assessment would, of course, show the deniers work in a very poor light indeed.
  12. I'm not sure if this is the right thread for this post, but I'm asking whether there is any material addressing this new theory? It's really doing the rounds in Australia. It's all about heat exchange in the upper atmosphere — Douglas Cotton Lastly, how do I subscribe to a thread? I'm not getting emails when someone answers me?

    [DB] You should be getting those now.  You may have to log out of SkS and then re-log back in for the changes I made to take effect.

  13. Eclipse @366, I am not sure of the correct thread, so I'll make my response here. First I should say, what a load of tripe Douglas Cotton has produced. He persistently claims that the IPCC "assumes" values which have been measured, while asserting without measurement "facts" to be true simply on the basis that they are convenient to his theory. Like many deniers, he obviously has no idea what goes into a General Circulation Model, assuming that they have the properties of a one dimensional model, while he himself employs an unphysical model of radiative transfer, the most obvious flaw of which is that he assumes any upward transmitted radiation from the atmosphere is immediately emitted to space (whereas most of it is simply absorbed by higher levels of the atmosphere). His core assumption is that:
    "The IPCC models assume far too much radiation from the Earth's surface instead of convection with air molecules which do not emit photons that can be captured by CO2"
    He defends that claim with this illustration: The defense consists of simply reasserting his claim, and an analogy based on a cooking pot. Of course, the IPCC (actually Kiehl and Trenberth 1997, which has since been updated with Trenberth, Fasullo and Kiehl 2008 [PDF]) based their conclusions on actual measurement. The difficulty arises because it is not possible to measure the upward surface IR radiation at all, or even many locations around the globe. Rather, detailed measurements have been done over particular land surface types under various conditions. These measurements produce results like these: Note that the upward IR radiation is consistently greater than 400 W/m^2. (It is shown as a negative number to distinguish energy leaving from energy entering the surface. For comparison, consider these measurements of Net radiation, Q*, (Incoming shortwave plus incoming longwave minus outgoing shortwave minus outgoing longwave), latent energy, LW, and sensible heat, H. Sensible Heat, Cotton's "conduction" does not rise above 200 W/m^2 except over a dry lake bed, and is negative for much of the time. Clearly, averaged across the twenty four hour day, and across a variety of locations, it is a much smaller component than the outgoing surface IR radiation. Khiel and Trenberth's figures where generated by taking a great number of measurements such as these, and using them together with knowledge of the proportion of the Earth's surface covered by each surface type to estimate a global figure. In contrast, Cotton's alternative estimate was made by waving his hand near a cooking pot. The difference in procedure is a true indicator of the difference in value of the two works.
  14. Well, I had to read it carefully to make sure this guy was serious and not a Poe. So many unphysical things, so little time. You might like to look also at Greenhouse theory violates 2nd Law thread too. Unfortunately, there are a great many "papers" like this around. Appinsys and are full of them (often mutually contradictory). The question is ask is "has it been published in a peer-reviewed journal?" (and E&E doesnt count). There is a Nobel prize waiting for someone who can get humanity off the global warming hook. I'd cheer them all the way, but Cotton isn't the man.
  15. Tom wrote: "In contrast, Cotton's alternative estimate was made by waving his hand near a cooking pot." LOL! That's taking 'hand waving' arguments to a whole new level. :]
  16. The gravitational warmth theory seems to be making the rounds these days. The idea that the Earth would heat itself through gravity in the absense of the sun boggles the mind. Especially after going to great lengths to show how the incoming solar radiation has fluctuated throuhgout history. While some people like his hand waving over the cooking pot, it does show how some scientists are placing to much emphasis on outgoing radiation effects in the atmosphere as opposed to convection. Of course, this is due to the much larger difficulty in measuring the convection effects.
  17. EtR#370: "gravitational warmth theory" We heard that one over and over on the 2nd Law threads; its all due to the potential energy released by air molecules falling from the upper atmosphere. That does not rise to the level of 'theory'; call it an idea, a notion, a delusion. "some people like his hand waving over the cooking pot," It's easier than doing actual research. Fewer annoying things like 'data' to worry about.
  18. Eric the Red @370, which scientists are "...placing to much emphasis on outgoing radiation effects in the atmosphere as opposed to convection"? It is certainly not the mainstream climate scientists. The importance of convection as a distributor of heat has been central to the theory of the greenhouse effect since Manabe and Wetherald 1967, and is a central feature of GCMs.
  19. 370, Eric the Red, does show how some scientists are placing to much emphasis on outgoing radiation effects in the atmosphere as opposed to convection.
    Evidence, please. This is mere assertion. At the same time, please reference Trenberth's energy budget, which is a careful accounting of exactly how energy is transferred, backed by actual measurements. Coming down: 517 W/m2. Going up (in W/m2)...
    Convection (thermals):17
    Total: 517 Everything balances as measured (in/out/retained). Gee, whiz, those dang scientists really do know what they are talking about... precisely, and without simple assertions and hand waving.
  20. Michael Pidwirney of NASA has some different values: Incoming radiation: 340 W/m2 Reflected: 99 W/m2 Absorbed by Atmosphere: 78 W/m2 Absorbed by Surfase: 163 W/m2 Of that absorbed by the surface, his ebergy transfer numbers are: Thermal radiation: 61 W/m2 Convection: 17 W/m2 Evaporation: 85 W/m2 You can stop waving your hands now.
  21. 374, Eric the Red, If you are getting your numbers from Pidwirny's article on energy balance of the earth where this diagram is just a revision of Trenberth's, substituting percentages for W/m2, then I'm afraid you are reading it incorrectly. In any event your numbers are incomplete. You are only accounting for incoming radiation (340) and not the greenhouse effect (which adds additional energy to the surface that must be accounted for). Either way, how does this in any way support your original contention that "scientists are placing too much emphasis on outgoing radiation effects in the atmosphere as opposed to convection"? Or are you openly withdrawing that comment?
  22. Eric the Red @374, I am going to need a citation for that claim. I have googled several articles articles written by Pidwirny, and none of them have the figures you show. Further, as Sphaerica points out, your quoted figure was for net thermal radiation (Surface Radiation minus Back Radiation), whereas Cotton and I where clearly discussing the Surface Radiation alone.
  23. Tom, Try here.
  24. 377, Eric the Red, Yes, we know. That's where we looked. That site is not only in complete agreement with Trenberth, but it got its data from Trenberth. Follow the citations at the end of the article. You have greatly misinterpreted what you found there. You need to read it much, much more carefully. And where exactly in that did you get your numbers from? I don't find your particular numbers anywhere there.
  25. 377, Eric the Red, You also avoided my salient questions from post 375:
    Either way, how does this in any way support your original contention that "scientists are placing too much emphasis on outgoing radiation effects in the atmosphere as opposed to convection"? Or are you openly withdrawing that comment?

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