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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 1 to 25 out of 908:

  1. Concensus only has meaning if there is no pressure to conform in either direction. In the climate debate this is extremely far from being true. How far could we reasonably expect a questioner to go in an IPCC panel when that instantly collects a denialist label and probably guarantees a dead end to even the most able career? In the current climate it is reasonable to assume the dissent camp is at least ten times the admitted size. I know that as an admittedly uninformed questioner I get some pretty vitriolic responses from the eco faithful.
  2. Roverdc hits the nail on the head. To say there is bias in the science at this point is a wild understatement. What the public hears is claims that "all scientists except a few kooks agree that catastrophic global warming is immenent and caused by your car.". This is what they think you mean by consensus. Is it safe to say the real consensus is closer to the view of those so called deniers in the National Post series or to the alarmist panic that is being widely circulated through things like "An Inconvenient Truth"?
  3. The fact that there are so many Academies of Science endorsing the global warming position is probably the strongest argument for supporting it. The question to ask is how mature is this field? If the answer is 'very mature' then this type of support has high credibility. If the answer is 'immature' then it's significance is considerably less. Here is a link to US Senate Committee on the Environment that lists in detail 400 scientists who disagree with the anthropomorphic global warming hypothesis: http://epw.senate.gov/public/index.cfm?FuseAction=Minority.SenateReport That there are so many when we repeatedly hear on the news and radio that the actual number of dissenters is 'miniscule' will have the tendency to turn believers into sceptics. I would also feel more confident if the 'hockey stick' graphics that predict rapid change and global catastrophe would not all be linked back to a small handful of researchers and students who work together and presumably have the same preconceptions and modus operandi. If there are no 'hockey sticks' then the small increase in global temperature over the last century does not statistically look different from what one would expect from natural variation.
  4. that list of 400 is about as big a hoax as the "Petition Project" was. Here's one of many sites exposing it. http://gristmill.grist.org/user/Andrew%20Dessler would you like to try again, Mr. Nitschke?
  5. sorry about the double post, and for the unintended smarmy tone.
  6. I think I'd put the list on the petition project up against the IPCC list, many of whom disagree with IPCC conclusions, any day of the week. The listed expose here paledriver is pure rubbish. Maybe you should investigate the actual list rather than the fake and distorted claims about it.
  7. The Marshall Institute co-sponsored with the OISM a deceptive campaign -- known as the Petition Project -- to undermine and discredit the scientific authority of the IPCC and to oppose the Kyoto Protocol. Early in the spring of 1998, thousands of scientists around the country received a mass mailing urging them to sign a petition calling on the government to reject the Kyoto Protocol. The petition was accompanied by other pieces including an article formatted to mimic the journal of the National Academy of Sciences. Subsequent research revealed that the article had not been peer-reviewed, nor published, nor even accepted for publication in that journal and the Academy released a strong statement disclaiming any connection to this effort and reaffirming the reality of climate change. The Petition resurfaced in 2001. They openly lied about endorsement from National Academy of Sciences, were caught, the Academy issues a statement disclaiming any connection, they re-release it again anyways, and you're foolish and gullible enough to buy it and defend it. Would you like me to post a sample of the signers? That would be embarrassing for you.
  8. i will anyways......................... The term "scientists" is often used in describing signatories. The petition requests signatories list their degree (B.S., M.S., or Ph.D.) and to list their scientific field.[3] The distribution of petitions was relatively uncontrolled: those receiving the petition could check a line that said "send more petition cards for me to distribute". The Petition Project itself used to state: “ Of the 19,700 signatures that the project has received in total so far, 17,800 have been independently verified and the other 1,900 have not yet been independently verified. Of those signers holding the degree of PhD, 95% have now been independently verified. One name that was sent in by enviro pranksters, Geri Halliwell, PhD, has been eliminated. Several names, such as Perry Mason and Robert Byrd are still on the list even though enviro press reports have ridiculed their identity with the names of famous personalities. They are actual signers. Perry Mason, for example, is a PhD Chemist.[2] ” In May 1998 the Seattle Times wrote: “ Several environmental groups questioned dozens of the names: "Perry S. Mason" (the fictitious lawyer?), "Michael J. Fox" (the actor?), "Robert C. Byrd" (the senator?), "John C. Grisham" (the lawyer-author?). And then there's the Spice Girl, a k a. Geraldine Halliwell: The petition listed "Dr. Geri Halliwell" and "Dr. Halliwell." Asked about the pop singer, Robinson said he was duped. The returned petition, one of thousands of mailings he sent out, identified her as having a degree in microbiology and living in Boston. "It's fake," he said.[15] ” In 2005, Scientific American reported: “ Scientific American took a sample of 30 of the 1,400 signatories claiming to hold a Ph.D. in a climate-related science. Of the 26 we were able to identify in various databases, 11 said they still agreed with the petition —- one was an active climate researcher, two others had relevant expertise, and eight signed based on an informal evaluation. Six said they would not sign the petition today, three did not remember any such petition, one had died, and five did not answer repeated messages. Crudely extrapolating, the petition supporters include a core of about 200 climate researchers – a respectable number, though rather a small fraction of the climatological community.[16] ” In a 2005 op-ed in the Hawaii Reporter, Todd Shelly wrote: “ In less than 10 minutes of casual scanning, I found duplicate names (Did two Joe R. Eaglemans and two David Tompkins sign the petition, or were some individuals counted twice?), single names without even an initial (Biolchini), corporate names (Graybeal & Sayre, Inc. How does a business sign a petition?), and an apparently phony single name (Redwine, Ph.D.). These examples underscore a major weakness of the list: there is no way to check the authenticity of the names. Names are given, but no identifying information (e.g., institutional affiliation) is provided. Why the lack of transparency?[17]
  9. I have the article you claim was "formatted to mimic..." sitting right here. It doesn't look like it is anything of the sort. In fact it clearly lists Author and who puplished it. It looks like a review of literature type paper which...it is. As for mass mailing as it was done with a tiny budget it was nothing of the sort. In fact I never even got one despite being on one of the main mailing lists they supposedly used. How many copies of this supposed mass mailing did you get? Aren't you bothered by a clear attempt by the "enviros" to commit fraud with fake names? Shouldn't you question why they think this is needed or something to be proud of. Is it ok to be dishonest as long as they are on your side? A sample of 30 in which some back down (people get fired for being skeptics in this field you know)is instantly credible to you while you arm wave away 17,000 You are pointing out 1 fake signature out of 19,000! Really? It was caught, we had thousands of Fake names on our voting list in one nearby city alone. You are avoiding the main issue. Consensus is not science but if it was the supposed 2500 scientists of the IPCC report have every failing you mention of the petition project and more important the people who signed the petition agreed with what it said. The same can not be said for the IPCC and its supposed 2500. Counted in that IPCC number are hundreds of non scientists, NGO reps (these are people with an agenda)and most importantly reviewers, many of whom don't even agree with the conclusions of the IPCC report. In fact most of the famous "deniers" are included in the 2500 IPCC counts. Someone made the mistake of asking them after the second IPCC report (surveyed participants) and found that over 60% did not agree with the summary for policy makers. Maybe we should stop pretending numbers and NGOs are scientists and that consensus is science. It's that claim that raises huge red flags for me.
  10. Wow, that was terrible punctuation. Darn Packers
  11. I'm sorry. Are you a Packer fan? Picked another losing cause? I'm sorry again,but I couldn't help myself on that one. Great game though.
  12. Let's take a look at the "Inhofe 400" Meteorologist George Waldenberg was named. In response to his inclusion ,Mr. Waldenberg sent an email to Senator Inhofes' staff that began "Marc, Matthew: Take me off your list of 400 (Prominent) Scientists that dispute Man-Made Global warming claims. I've never made any claims that debunk the "Consensus". You quoted a newspaper article that's main focus was scoring the accuracy of local weathermen. Hardly Scientific ... yet I'm guessing some of your other sources pale in comparison in terms of credibility. You also didn't ask for my permission to use these statements. That's not a very respectable way of doing "research". One shining example. I have many more.
  13. Again? now its one out of 400 and who the heck was talking about the Inhofe 400? The point remains it is not a popularity contest despite all the attempted score keeping by the IPCC fans. Also many of the prominent scientists counted in that score are in fact the so called deniers.
  14. the point remains that the deniers flesh out their "petitions" and "lists" with fakes, fraudulent claims, and people who in no way have made any claims against the consensus and pointedly say so. I've pointed out one of many, (which I've linked to above) And the "400" was brought up on post#3, which is why I even referred to fraudulent "Petition Project" in the first place.
  15. p.s. I'm not claiming that there's no dissent. Just that there IS a consensus. An overwhelming one.
  16. Well that awful Inhofe 400 is now over 420 as in the time it took for you to complain about the one that didn't sign 20 more "scientists" did. But, it isn't important. My problem with this is, it isn't an election, you claim the skeptics inflate their numbers, maybe so, beyond question the AGW catastrophy folks inflate theirs. At least two of the best known "deniers" are IPCC lead authors. Dozens of others are listed as contributers or reviewers, several have been so disgusted with the process they withdrew and asked their names be removed. This means they are counted on both sides. What is that overwelming consensus? Here is what is presented as that consensus: Human CO2 emissions will cause massive catastrophic warming, It will cause disaster in the near future ruining the world for our children. This warming will lead to massive flooding, drought, wide scale starvation, wars, plagues, melting of the polar ice, flooding of huge areas of the world... Refer to my post number 2 above. Which is closer to the consensus? Al Gore with 23 feet of sea level rise this century or the "deniers" with 15-20 cm ? Al Gore with his talk of "unprecidented warming". Or the "deniers" claims that the world seems to have wamed about .6-.7 C over the last century and that may be somewhat due to human activity. Most of the "deniers" probably don't even have that much trouble with the consensus as stated in the first paragraph of the original post. They are vilified largely because they refuse to accept the supposed consensus I just described. In general I agreed with the stated consensus in the original post, though based on the recent data and the trouble with the historical record I think now I would not use the word "most".
  17. 420? In the original 400 I found many who were completely unqualified, some of whom are skeptical, some of whom are not. Many who are qualified who are either not actually skeptical, are skeptical only of some proposed solutions or who have actually stated their agreement WITH the consensus. The list was not made to hold up to close scrutiny. I imagine it's the same with the additional 20.
  18. addressing claims about the IPCC............... "John McLean and the NRSP Category: Global Warming Posted on: December 20, 2007 1:02 PM, by Tim Lambert Hey, remember John McLean? The guy who kept steering Andrew Bolt into brick walls? Well he's teamed up with Tom Harris of the NRSP to accuse the IPCC of lying about the scientific support for its reports: In total, only 62 scientists reviewed the chapter in which this statement appears, the critical chapter 9, "Understanding and Attributing Climate Change". Of the comments received from the 62 reviewers of this critical chapter, almost 60% of them were rejected by IPCC editors. And of the 62 expert reviewers of this chapter, 55 had serious vested interest, leaving only seven expert reviewers who appear impartial. First, there were much more than 62 reviewers for chapter 9. McLean and Harris have only counted the reviewers of the second order draft and ignored the more numerous comments on the first order draft. Second, they mislead by giving the impression that 60% of the reviewers disagreed with the IPCC, but half of the comments (572 of them!) were made by Vincent Gray, with 97% of them rejected. Only 16% of the comments by other reviewers were rejected. Gray was also responsible for most the rejected comments on the first order draft. Examples of Gray's rejected comments include: Insert after "to" "the utterly ridiculous assumption of" Insert after "Bayesian" "(or super-guesswork)" Insret before "Calibrated" "Bogus" Dave Semeniuk has a more detailed analysis of Gray's comments -- 50 of them were Gray repeatedly asking for "anthropogenic" to be replaced with "human-induced". Third, as Richard Littlemore points out, it is pretty dodgy for the NRSP to complain about "vested interest" when their own vested interest is so blatant. But how did McLean and Harris come up with their claim that 55 of the reviewers had "serious vested interest"? McLean gives details in a piece published by the SPPI (an oil industry funded think tank that apparently does not count as a vested interested to McLean). Scientists were declared to have a vested interest if they were an IPCC author, or an IPCC author of a previous assessment, or if any of their work was cited by the report, or if they worked for a government, or if they work for an organization that gets government funding, or if they have a "possible commercial vested interest in the claim of man-made warming". Basically that leaves amateurs like Gray and McKitrick. In one of his comments Gray asked them to cite one of his Energy and Environment papers. Fortunately it was rejected, or he would have been ruled out as well. John Mashey examined McLean's background and it seems that while the National Post awarded him a PhD he actually has no scientific qualifications at all, just a Bachelor of Architecture. Which makes McLean's rant against a critic, which was captured by Nexus 6 particularly funny." http://scienceblogs.com/deltoid/2007/12/john_mclean_and_the_nrsp.php
  19. It appears you have proved my point.
  20. it took you 23 days to come up with that?
  21. You mean I should have quickly pointed out that you had proven my point? Not allow you time to elaborate or correct?
  22. please, for my age addled mind, explain how I've proved your point.
  23. My point is the consensus, such as it is, is closer to the denialist view than the popular view of Al Gore etc. The claim that there is some vast number of scientists that constitute a consensus and that agree with catastrophic warming is not only not science it isn't even correct. We constantly see people pointing out IPCC to supposedly prove this supposed consensus. IPCC isnt all qualified scientists any more than any of these lists are. But more important than that, despite the fact that a pro warming bias is built into the entire IPCC process, the actual body of the IPCC report in fact supports my position rather than that of Al Gore. When I pointed out that the petition project and other similar things like the Heidelberg appeal all had one thing the IPCC didn't have; the consent and agreement of the people involved. (This is something lacking in the lists of academies etc. in the original post as well.) You ignored it completely as if tiny politically active committees somehow spoke for all. Personal attacks on a handful of people, each of which is questionable in itself does nothing to refute my stated point. It appears rather to be a deliberate attempt to obfuscate the issue.
  24. The deniers series in the National post has grown much larger. It is still a good series can you update the link so it doesn't just lead to the first 10.
  25. Yeah, Vincent Gray made a lot of noise, ergo there's no consensus. Genius logic!

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