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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

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.

Acknowledgements

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

Update

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

Comments

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Comments 251 to 275 out of 330:

  1. Doug, that's an incredibly weak argument. Who's going to draw attention to their incorrect predictions? They get conveniently forgotten, and we are left with amazingly accurate forecasts. It's like a bankrupt gambling addict telling you about his big wins.
  2. @mistermack: "Archie, if the evidence was as overwhelming as you say, I wouldn't waste my time looking." The fact you are "still looking" doesn't affect the quality of the evidence in now way. I'll surmise that the reason you are still looking is that you have failed to understand the science, probably because you're too biased towards your preconceived notions to be receptive to it. Again, the evidence is there, and you have yet to present a convincing claim against it. "I know for a fact that the evidence is debateable, because I've done a lot of looking, much more that the average student intake." That's argument by assertion: "I'm right because I say I am." Sorry, but that logical fallacy won't cut it here. "I think I am therefore well justified in my conclusion that most people are initially convinced by the "consensus" rather than evidence." No, you're not. You haven't presented a shred of evidence to support your accusation. Therefore, the only think we can conclude is that you don't seem to know what you're talking about. "You mention doctors, but many doctors are also homeopaths, and many are "experts" in homeopathy." That's an attempt at changing the subject, and in fact *very few* medical doctors are homeopaths. Medical experts, and the current state of medical science, condemns homeopathy as the hoax it is. "The concencus of experts in homeopathy would be overwhelmingly supporting the effectiveness of homeopathic remedies." Homeopathy is not empirical science, and the vast majority of medical experts do not accept homeopahty and its alleged remedies are effective. So your example fails. "Same applies to Chirpractic." Again, that is not a valid examples, because chiropractors are not necessarily experts in medical science (and in fact I suppose very few do). These examples fail to support your anti-intellectual attack on experts. "I'm not saying that climate science is as silly as these," No, but you're certainly implying they are similar. "I'm just pointing out that a consensus is naturally self perpetuating, till it's disproved." Again, there is no indication that people who study climate believe in AGW because of the consensus. Rather, the consensus exists because the evidence (which you *choose* to ignore) indicates AGW is very likely true. "That's why the consensus on AGW is totally valueless, as evidence." Well, that's right in an of itself. Note that the article isn't claiming that the consensus is evidence AGW is true - it doesn't. Rather, it is a rebuttal of the contrarian argument that "there is no consensus," when in fact there is (as you yourself have admitted a few times in this thread already). So, again, the contrarian argument is that there is no consensus (hence such farces as the Oregon petition project), the rebuttal is that there is. You arguing that the consensus is meaningless is off-topic (and wrong in your characterization of the consensus). Please stop insinuating that people who study the climate are motivated by groupthink rather than rational thought. It's insulting, and goes against site policy (as it suggests a conspiration of dunces). "In climate science, you can't even predict next year's trend. But you can grandly predict the trend for the next century." Indeed. "Without the slightest risk of being proved wrong." So far, they haven't as temperatures are quite close to predictions - but I'm sure you'll change the subject and start attacking the quality of temperature records next. Contrarians are *so* predictable...
  3. @mistermack: Here some more evidence of anthropogenic global warming, from those know-nothings at NASA...
  4. Archie, your link, "evidence is there" just illustrates my point perfectly. The relevant question is the sensitivity of the climate to CO2. Will increased CO2 cause a big enough rise in temperature to cause problems. That's the one bit of evidence missing. The relevant bit. The rest is just window dressing. I didn't say there is no evidence about anything. I'm saying that you need evidence for the central tenet. Link me that, if you like.
  5. Archie, your page from the "know nothings at NASA" showed evidence of warming. We all know we've had warming. What's not there is good evidence for the title "anthropogenic". That's what's always missing.
  6. @mistermack: Climate Sensitivity is estimated at between 2.5C and 4C. If you have evidence to the contrary, by all means present it. So far you have failed to do so. As for the NASA page, it clearly shows the current level of CO2, and we know CO2 "greenhouse gas" properties will increase temperatures. We also know this extra CO2 is from anthropogenic sources. Therefore, it is very likely humans are responsible for the current warming. Again, you have failed to produce a single piece of evidence that disputes this. The burden of proof is on you - better start working on that thesis! At least you agree it's warming, even if you're ready to gamble civilization's future just because you disagree (without evidence) about climate sensitivity.
  7. mistermack at 06:53 AM on 25 October 2010 Please read Lean 2010, and look at figure 6.
  8. Responseman, I looked at "Climate sensitivity is low", the first sentence is :"There are some things about our climate we are pretty certain about. Unfortunately, climate sensitivity isn’t one of them". That makes my point for me. The "consensus" is there, in spite of the lack of certainty about the central tenet of AGW. That is, is the climate sufficiently sensitive to CO2 for there to be a problem? I argued that the consensus is fortified by the consensus in a feedback loop, not by certainty of the evidence.
    Response: Read past the first sentence. Click on the "Advanced" tab. Read the section "What is the possible range of climate sensitivity?" Note that certainty is high regarding the lower limit of sensitivity, and that even that lower limit will have serious adverse consequences. (You need to read the entire Advanced post to get all that.)
  9. I did read more. I noted that it's claimed "we know that....." without saying how. I don't want to get off topic, but a model doesn't justify "we know that", you could maybe say "we calculate that...." or "our best estimate is....." What this seems to indicate, is that the "consensus" is basically the result of faith in models. Yet others are telling me that they think it's the result of evidence. I still think consensus has built itself up in a feedback loop.
    Response: Why on Earth do you think all the evidence is in this blog? The authors of these blog posts go to considerable trouble to cite, and when possible link to, the peer reviewed scientific literature so that blog readers can go there if they want more info. Commenters responding to you have done the same. It's past time for you to take advantage of those resources.
  10. I'm replying to the link you offered me. It hardly follows that I think all the evidence is here. I politely read the link you offered, and responded. But to be honest, given the purpose of this website, I would have expected all of the best evidence to be summarised here. (somewhere) Perhaps that's a suggestion. A page called "here is the best evidence for AGW" (or maybe I've missed it). I would take it as read that we've had warming. (only the warming since 1950 should count, since CO2 rises were completely insignificant before that). So a page with nothing but evidence linking manmade CO2 to the warming since 1950 would be absolutely brilliant.
    Response: The Big Picture
  11. @mistermack: "A page called "here is the best evidence for AGW" (or maybe I've missed it)." I already pointed towards it. Now, if you could indicate which information on that page is inaccurate (with evidence, which you keep asking for but never provide to support your own claims), that would be appreciated.
    Response: Also, mistermack, when on any page you see blue text, you should click on it, because it is a hyperlink to more information. And look past the end of each original post, because often there are green boxes with links to further reading and to related Skeptical Science posts.
  12. #242: "most "experts" are apologists for the concensus:" Let's accept that philosophy for a moment, postulating that it must work both ways. So W@tts and G*ddard and Jo#ova and all the other so-called 'experts' who've bought into the consensus (31000 scientists agree) that AGW is a scam are mere apologists. You can't have it both ways. But in reality, I would rather live in a world that values consensus among experts -- or at least one that values expert discussion of disagreements with logic, observation and sound science rather than name-calling and petty vitriolics. Because this is what you get when there's no consensus.
  13. Responding to Response to 261, I looked, it doesn't contain any evidence of a human link, but I clicked on the fingerprint link, to the "it's not us" argument, which is probably the closest to an evidence page as there is. It's good reading, a lot more relevant than anything else I've found on here. At the end of the day though, the evidence still boils down to models, models of where the warming should be detected, followed by this is the warming we detected. ( etc ). If you accept the models are true, you can claim plenty of evidence. If you regard the models as needing confirmation, then the evidence needs confirmation. I can't help but conclude that the models were inspired by the data, so you shouldn't call it evidence if the data matches the models. If the consensus is the result of the evidence, then it seems to depend on the data and the models matching up, which is hardly surprising.
  14. @mistermack: not all evidence rests on model, some can be directly observed and/or reproducible in a lab (the actual greenhouse properties of CO2, for example). Similarly, the fact that we are increasing the concentration of CO2 in the atmosphere can be determined without resorting to models. Now, as far as models go: you're welcome to demonstrate how the models are inaccurate, and produce your own models to explain the observed data. Until then, don't be offended if I'd rather accept the actual science presented on this site rather than the vague allegations and half-baked arguments you keep throwing around. In the meantime, why not check out the Models are unreliable page?
  15. Isn't the important consensus the following: That the earth is warming, man is a significant cause, *that the problem will be serious if nothing is done about it AND the proposed actions (e.g. Kyoto protocol, Cap and Trade, Copenhagen agreement) will prevent the problem from happening?* What % of published climate scientists would answer yes to that question? The majority of climate scientists I've heard opine on the issue of the effectiveness of any of the proposed solutions is that they won't stop the problem from happening.
  16. #268: "The majority of climate scientists I've heard opine on the issue of the effectiveness of any of the proposed solutions" Sounds like you already have your own answer to the question you posed. Is a difference of opinion sufficient reason for doing nothing? You could consider looking into the question here and here to learn something about it. If you want to engage in a serious discussion, you should also give specific references to the 'climate scientists' whose opines you are following. Helps to know what your sources are.
  17. Muoncounter #269 - what did you wake up on the wrong side of the bed today? You know any climate scientist that thinks Kyoto or Cap and Trade will stop global warming? My point is that if you're going to use consensus as argument, than you have to have consensus on the important part of the issue - what to do about it, not that it's happening. Here's a reference for you - James Hanson and Cap and Trade. http://www.nytimes.com/2009/12/07/opinion/07hansen.html
  18. #268 - Here's another reference for you - the consensus breaks down the more you dig into it. http://stats.org/stories/2008/global_warming_survey_apr23_08.html
  19. Re: StyleDoggie Interesting position to take. If you're positing that... 1. It's the total bolus of carbon slug injected into the Earth's atmosphere that matters and 2. Human nature means the cessation of burning of fossil fuels will happen when cold, dead hands are pried off the pumps ...then I'm of a similar mind. I've always liked Hansen's position on fee & dividends, but I suspect it too doesn't go far enough to forestall CO2 emissions quickly enough. Your STATS survey of climate scientists is a bit dated now. In light of current events, most on the fence will be re-thinking just how uncomfortable that position has become. But what the heck do I know? Not a climate scientist. Just some guy on a blog with degrees in the Earth Sciences... The Yooper
  20. #270: "if you're going to use consensus as argument" The consensus in question in this article is "demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them." Thus there is general agreement among serious scientists that global warming is happening and we are causing it. "you have to have consensus on the important part of the issue - what to do about it" That's a separate question and wildly off-topic. The Hansen op-ed you linked in #270 calls for stronger measures than cap and trade: "There is a better alternative, one that would be more efficient and less costly than cap and trade: 'fee and dividend.'" However, in the US, conservative talking heads have basically killed any hope for any action with their 'cap and tax' hot air. Don't conflate lack of consensus on what to do, which is mired in political rhetoric, to consensus over what is happening. If you want to continue discussing what to do, go to Solving global warming. "the consensus breaks down the more you dig into it." No, it does not. First of all, the survey is older than the Hansen article, so 'the more you dig into it' doesn't make sense. But more importantly: Based on current trends, 41% of scientists believe global climate change will pose a very great danger to the earth in the next 50 to 100 years, compared to 13% who see relatively little danger. Another 44% rate climate change as moderately dangerous. That's 85% in the moderate to very great danger camp. Makes you think that the folks shouting down any ideas for change are the ones causing the problem. Which side are you on? Yooper, I also have some earth sci degrees somewhere in my distant and checkered past. Knew there was something I liked about you.
  21. Re: StyleDoggie BTW, consensus is an ever-evolving narrative, adapting (one way or the other) to emerging understanding over time. Much has become known since 2008. That makes the study you cited dated. As my one lone example showed (had you read the link). The Yooper
  22. Re: muoncounter (273)
    "Yooper, I also have some earth sci degrees somewhere in my distant and checkered past. Knew there was something I liked about you."
    Early 80's, Central Michigan University. Diploma can be found somewhere in the paleo record. :) Appreciate the sentiments; likewise. Based on many of your comments, you received a better grounding in energy budgets than I did. My instructors taught me other things, like shotgunning whiskey into (many) beers... The Yooper
  23. #274 - Claims of settled science and scientific consensus have been around since at least 1989 - here's a reference from the NYTimes. But NOW, there REALLY IS a consensus. I see. http://query.nytimes.com/gst/fullpage.html?res=950DEED61E3CF937A25750C0A96F948260
    Response: Please refrain from using all caps. Use italics or, if really necessary, bold.
  24. " "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Doran 2009). … 97.5% of climatologists who actively publish research on climate change responded yes." That is exactly 75 people. "There are three kinds of lies: lies, damned lies, and statistics"
  25. @NQoA: what's your point, exactly? That we should trust experts on a particular matter because there's relatively few of them? I know deniers usually aren't motivated by logic, but you sir take the cake.

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