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It’s settled: 90–100% of climate experts agree on human-caused global warming

Posted on 13 April 2016 by dana1981

There is an overwhelming expert scientific consensus on human-caused global warming.

Authors of seven previous climate consensus studies — including Naomi Oreskes,Peter DoranWilliam AndereggBart VerheggenEd MaibachJ. Stuart Carlton,John Cook, myself, and six of our colleagues — have co-authored a new 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

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 12% of Americans realize that the consensus is above 90%.


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

Consensus misrepresentations

Our latest paper was written in response to a critique published by Richard Tol in Environmental Research Letters, commenting on the 2013 paper published in the same journal by John Cook, myself, and colleagues finding a 97% consensus on human-caused global warming in the peer-reviewed literature.

Tol argues that when considering results from previous consensus studies, the Cook 97% figure is an outlier, which he claims is much higher than most other climate consensus estimates. He makes this argument by looking at sub-samples from previous surveys. For example, Doran’s 2009 study broke down the survey data by profession – the consensus was 47% among economic geologists, 64% among meteorologists, 82% among all Earth scientists, and 97% among publishing climate scientists. The lower the climate expertise in each group, the lower the consensus.

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

Like several of these consensus surveys, Doran cast a wide net and included responses from many non-experts, but among the experts, the consensus is consistently between 90% and 100%. However, by including the non-expert samples, it’s possible to find low “consensus” values.

The flaw in this approach is especially clear when we consider the most ridiculous sub-sample included in Tol’s critique: Verheggen’s 2015 study included a grouping of predominantly non-experts who were “unconvinced” by human-caused global warming, among whom the consensus was 7%. The only surprising thing about this number is that more than zero of those “unconvinced” by human-caused global warming agree that humans are the main cause of global warming. In his paper, Tol included this 7% “unconvinced,” non-expert sub-sample as a data point in his argument that the 97% consensus result is unusually high.

By breaking out all of these sub-samples of non-experts, the critique thus misrepresented a number of previous consensus studies in an effort to paint our 97% result as an outlier. The authors of those misrepresented studies were not impressed with this approach, denouncing the misrepresentations of their work in no uncertain terms

We subsequently collaborated with those authors in this newly-published scholarly response, bringing together an all-star lineup of climate consensus experts. The following quote from the paper sums up our feelings about the critique’s treatment of our research:

Tol’s (2016) conflation of unrepresentative non-expert sub-samples and samples of climate experts is a misrepresentation of the results of previous studies, including those published by a number of coauthors of this paper.

Consensus on consensus

In our paper, we show that including non-experts is the only way to argue for a consensus below 90–100%. The greater the climate expertise among those included in the survey sample, the higher the consensus on human-caused global warming. Similarly, if you want to know if you need open heart surgery, you’ll get much more consistent answers (higher consensus) if you only ask cardiologists than if you also survey podiatrists, neurologists, and dentists.

That’s because, as we all know, expertise matters. It’s easy to manufacture a smaller non-expert “consensus” number and argue that it contradicts the 97% figure. As our new paper shows, when you ask the climate experts, the consensus on human-caused global warming is between 90% and 100%, with several studies finding 97% consensus among publishing climate scientists.

There’s some variation in the percentage, depending on exactly how the survey is done and how the question is worded, but ultimately it’s still true that there’s a 97% consensus in the peer-reviewed scientific literature on human-caused global warming. In fact, even Richard Tol has agreed:

The consensus is of course in the high nineties.

Is the consensus 97% or 99.9%?

In fact, some believe our 97% consensus estimate was too low. These claims are usually based on an analysis done by James Powell, and the difference simply boils down to how “consensus” is defined. Powell evaluated the percentage of papers that don’t explicitly reject human-caused global warming in their abstracts. That includes 99.83% of papers published between 1991 and 2012, and 99.96% of papers published in 2013.

In short, 97% of peer-reviewed climate research that states a position on human-caused warming endorses the consensus, and about 99.9% of the total climate research doesn’t explicitly reject human-caused global warming. 

Click here to read the rest

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Comments 1 to 37:

  1. First of all consensus is not what makes a scientific theory true.  There used to be consensus that the sun orbited around the earth.  There used to be consensus that the earth is flat.   Evidence that a scientific theory is true is when predictions match reality.  Climate model predictions have deviated extensively from reality.  Tinkering with the models after the predictions fail to make them match the past is fudging and does not support any theory at all.  

    Second there was a recent large scale study in the Netherlands showing that the consensus was not that human activity caused climate change.

    0 2
    Moderator Response:

    [JH] Sloganeering sticken.

    Also, please provide references for your statements about specific studies. 

  2. @ alfalfa: this site is frequented by scientists and others who know what they're talking about. Peddle your tired misinformation elsewhere.

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  3. @ alfalfa:  The consensus is what the scientific literature states, not opinion as you seem to indicate. 

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  4. alfalfa @1 claims that "There used to be consensus that the earth is flat" (since stricken as sloganeering by the moderator).

    Of course, that claim is a myth.  That the Earth has been round has been the concensus among scholars since emperical observations have been coupled with mathematical reasoning in the fourth century BC (Aristotle).  That the Earth orbits the Sun has been the concensus since just prior to the start of the scientific revolution (ie, the wide spread acceptance that observation, not the authority of the ancients is the primary determinant of knowledge).

    What has persisted is a concensus among the ignorant that contradicts the scientific concensus - much as is the case with climate science.  Historically, where the popular view has starkly contrasted with the scientific view, the scientific view has always proved more accurate in the long run.  If alfalfa was to truly draw the lesson from history, he would conclude that the 97% consensus is good reason to think that whatever the truth about climate, it is far closer to the scientific consensus than popular theories espoused on the internet.

    Of course, he will not.  We know already from his views on climate science that his opinions are not guided by empirical facts, but by what he desires to be true.

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    Moderator Response:

    [PS] I think we have enough responses to alfalfa now. Thanks for contributions. More would be dogpiling. Let us see whether alfalfa can back his/her claims and please dont let this discussion disappear down a track of when/if people thought earth was flat. I think we can all acknowledge that consensus doesnt imply a theory is true and that consensus positions have been wrong in the past. The point is that consensus does exist and consensus position is best guide to policy. Please dont get this offtrack.

  5. Tom@4,

    Thank you for your valuable assertion and a link showing that flat earth concept was a myth among science denialist rather than the errant of science. I havn't known it! Thus Middle Ages were not "Dark Ages of Science" as wrongly portrayed by common opinion, but "Dark Ages of Science Denial". Exactly the same phenomenon as in today's climate science (Concensus Gap).

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  6. Crossing out the truth doesn't make it any less true.  If you want a reference to the Netherland study take a look at

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    Moderator Response:

    [JH] Moderation complaint snipped.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  7. Here is an article about how the antartica is growing.  Evidence is more important than consensus.

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    Moderator Response:

    [PS] Please see here for discussion on this. Note also from IPCC TAR

    "Changes in ice sheets and polar glaciers: Increased melting is expected on Arctic glaciers and the Greenland ice sheet, and they will retreat and thin close to their margins. Most of the Antarctic ice sheet is likely to thicken as a result of increased precipitation. There is a small risk, however, that the West Antarctic and Greenland ice sheets will retreat in coming centuries. Together, these cryospheric changes may make a significant contribution to sea-level rise.**** "

    so not exactly evidence against consensus. Please put any further discussion on Antartica in the appropriate thread.

    Also, when asked to back your assertions, please supply links published science not opinion pieces (and since pseudo-skeptic sites specialize in misrepresenting papers, make sure you actually read the paper).

  8. Alfalfa,  thank you for the link.  Once again I wish to point out that the scientific consensus being discussed here relates to what the published peer review research  world-wide shows.  That published research is physical evidence, not opinion.   Conversely, upon following your link I find that the non-consensus finding was an opinion poll of selected scientists in what was stated as climate related fields.  What I would have to ask is: how many of them have actually performed original climate research and had their findings published in the peer review literature?

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  9. alfalfa @6 references breitbart's spin on this study rather than the study itself.  That is nodoubt because if you look at the study itself, you will see it does not support either breitbart's spin.   Specifically, once you exclude the non-responses (unknown, I don't know, and other) 84.3% of respondents agreed with the IPCC that humans have caused 50% or greater of warming since the middle of the 20th century.  That figure is itself biased low because the respondents include a group of people invited to respond solely on the basis that they are AGW 'skeptics'.  That is, the sample population is not representative of climate scientists in general because of a deliberate bias to include additional 'skeptical' respondents.

    Breitbart tries to pull the wool over our eyes by focusing not on those who agree with the IPCC on attribution, but on that subset who also agree with the IPCC on how certain they are.  He also carefully neglects to mention the built in bias in the sample, portraying it as unbiased and representative when it is (by design) biased in favour of 'skeptical' respondents.

    alfalfa will find nothing wrong with breitbart's spin doctoring because, like all 'skeptics' his global warming denial is built on straining at gnats in the work of scientists, while swallowing camels served up by his fellow deniers.

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  10. NSIDC is down: it is discounting all of Aprils data as unreliable.

    How do we know any of March 2016, or indeed the weird few years of Arctic Sea Ice over the last few years, is reliable?

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  11. @1, Consensus starts with nomenclature!

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  12. alalfa@6,

    As expected, the study Breitbart is spinning is the one of Bart Verheggen, who is a co-author of the paper this post describes. That study is included in the wider analysis of the Carlton et al publication.

    The question for Breitbart and alfalfa is: if there are so many non-consensus scientists, then where are their papers, their AGU presentations, their conference attendances? None seem to exist beyond the 3% "usual suspects".

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  13. bozza@10

    There is more than 1 satellite:

    NSIDC Chart

    Univeristy of Breman image

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  14. I think there is a reason for this 'consensus is not science' myth.

    Consensus is a genuine feature of the scientific method, and it is used in every field of science. However most of the time it is not visible to the outsider, because we don't talk about it. The only reason it has become visible in the case of climate science is because of lay people asking 'how do you know?', which means we have to explain something of how scientific knowledge develops. If lay people were to challenge scientists in other fields, the answer would be the same.

    Here's an example from my primary field of X-ray crystallography. As it happens, a Nature paper and a whole load of protein structures have just been retracted: here and here. In the 1980s and 90s we had a significant problem with wrong structures being published, mostly due to rapidly developing methods being misapplied, but a few of them fraudulent.

    Scientists looked at how to address this problem, and decided that a paper should not be published unless both the atomic model, and the processed (in climate terms, adjusted and homogenized) X-ray data were deposited. Furthermore the results should be checked by cross-validation (leading to a statistic we call the 'Free-R factor').

    Over the course of around 5 years (which was remarkably fast) the community accepted that this was a good approach. It quickly became the norm that a paper would not be accepted without the data and cross validation tests, and eventually became a condition of publication. And as a result we now see a lot fewer wrong structures.

    Nowhere in the crystallographic literature will you find the term consensus. However that is what was going on. The community agreed there was a problem, and the community recognized that a particular solution was a good one. Decisions by journal editors and the data archives played a part, but they were in turn informed by the emergence of a consensus among methods developers and users.

    But if a lay person was to ask how the change happened, the existence of a consensus would be an important part of the answer. In fact I just did the experiment: I asked a senior figure in the field - an FRS - the question, and she used the term 'consensus' in her answer.

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  15. If I may be permitted to expand on the Dutch "Environmental Assessment Agency" survey ~ linked to by Tom Curtis @9 [and first raised by Alfalfa] :-

    I'm not quite sure of how it is named : possibly "Strengers, Verheggen & Vringer, 2015" . (Published by the Netherlands agency)

    It is based on a survey in early 2012 of opinions, requested of a select 6550 persons of whom "around 200" were chosen because of their known contrarian position against the scientific (climate) consensus.  There were more than a dozen questions, regarding attribution etc of global warming (if any).

    Of the 6550 invitees, there were 29% actual respondents (though down to 24% on some of the subsequent, more detailed questions). The survey authors claim that the known contrarians only constituted around 5% of respondents . . . possibly they mean 1/20th of the 29% .

    On the basic question of attribution, the large majority of respondents indicated that 50% to 100+% of global warming since mid-20th century was caused by anthropogenic greenhouse gases.  Around 12% opined that up to 50% was from GHG's (of whom a subgroup 7% opined 0-25% GHG attribution).

    *** This is a very different picture of scientific opinion, to what Alfalfa/Breitbart were publicizing.

    The other remarkable aspect, is the selection process for "invitees" to the survey.  The authors mentioned that the names selected for survey, were based variously on an (overlapping) basis of 500 from recent science literature; 2000 from a climate science database; and 6000 from "Web of Science"; and 200 known for their contrarian opinions.

    Most interestingly and unusually, the authors mentioned that: "half of whom only published in the gray literature on climate change" . . . and it was far from clear to me, whether they meant the contrarians or all those invited to reply to the survey.  Can anyone at SkS enlighten me about the authors' intention ~ and on the meaning of gray literature ?

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  16. Eclectic @15

    Bart Verheggen blogs on climate change at My view on climate change

    He has a post up on the paper discussed above: Consensus on consensus: a synthesis of consensus estimates on human-caused global warming

    Excellent opportunity for you to pose your questions to him directly.

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  17. I understand the concept of suggesting a consensus, but I also think that it becomes an easy taget of attack for contrarians.  I would prefer the use of 97% consilience of data to support AGW.  This goes to the heart of scientist, who they are and more importantly what they do.  

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  18. Why is this 97% or greater consensus not reflected in the attitudes of the wider community? Why is it that political persuasion has an effect on a scientific matter?

    A recent survey, January 2016, in the US found that although 70% of Americans believe the climate is changing only, 27% of respondents agreed with the “overwhelming scientific consensus that human activity is the main cause of climate change”. (

    There was a significant divide between Democrats and Republicans on the seriousness of climate change in that while 63% of the former saw climate change as a very serious matter only 18% of the latter held that view. The researchers noted that “the data exposes the extent to which this has become a partisan political issue in the U.S. rather than a scientific issue,”

    Why is climate change viewed so differently by Republicans and Democrats? Why is there so much politicisation of climate change? It’s the same science and climate is no respecter of persons be they Democrats or Republicans. Is something rather out of kilter in this global debate?

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  19. Haze @18

    Climate change has become a political football because any attempt to avert dangerous warming would entail an upheaval in our way of life.  To a lot of people this is anathema.  Consequently they fight tooth and nail to sabotage all climate action.

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  20. Digby Scorgie @19 Thanks for the response. Why however is there this significant disconnect between climate scientists and the general population? Surely it can't all be due to manipulation by the media as here in Australia the national broadcaster and the Fairfax press are very ardent advocates for the role humans play in climate change.

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  21. Digby Scorgie,

     That is my biggest problem with this whole controversy. That idea you have that mitigation necessarily requires upheaval in our way of life is not proven at all. Depends on the mitigation strategy taken. It can just as easily improve it even more. IMHO actually more likely to do that than anything.

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  22.  Digby Scorge @21.  My apologies if I have missed something but why in your reply do you say   "That idea you have that mitigation necessarily requires upheaval in our way of life is not proven at all"  Where, in what I have written at 18 and 20, do I say or even give the impresssion, that I have such an idea?

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  23. Haze,

    Yes you missed something. It was me not Digby Scorge that said that. Presumably that is where your confusion lies.

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  24. This is one of those selective arguments that distract from consideration of the holistic problems that society will have to try to cope with. Climate disruption and ocean acidification is one predicament. Others are over population, declining availability of many natural crustal resources, fertile soil and potable water together with irrevocable aging of the infrastructure that society has become so dependent on as well as devastation of the environment and pollution of land, sea, air and us.

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  25. Haze @18.

    You ask "Why is climate change viewed so differently by Republicans and Democrats?" I am a Brit so here assume the UK political scene is an equivalent to the US version.

    I once got into a long interchange on the impacts of and evidence for AGW with Peter Lilley, a right-wing Conservative MP & recently a recruit to the GWPF (Gentlemen Who Prefer Fantasy). As well as exhibiting all the signs of delusion and denial, the man eulogised the political philosopher JS Mill. This I considered rather strange as JS Mill famously said (and thus I suggest answers your question):-

    "Although it is not true that all conservatives are stupid people, it is true that most stupid people are conservative." 

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  26. As already noticed, the survey mentioned at Breitbart is based on a misrepresentation of the survey I undertook while at the Dutch PBL institute. More info about how it's been misrepresented at various places can be found on my blog. Or this post specifically how Rick Santorum misrepresented the survey.

    Basically, we found ~90% agreement among respondents with more than 10 climate related peer reviewed publications that recent global warming is for the most part (more than half) caused by anthropogenic greenhouse gases. Notice that we used a much stricter definition of what entails the consensus position than most other studies did. That probably goes a long way to explain why we found a slightly smaller level of consensus than some ither studies.

    As we explain in the paper (on which John Cook is a coauthor by the way) the fraction of outspoken contrarians (based on the puiblic list by Jim Prall) in our sample is only a few percent, and the level of consensus if this group were excluded would be ~3% higher. But approx half of this group are actually publishing climate scientists, so excluding them wouldn't be entirely fair; only excluding the "non-scientist-contrarians" (if that were possible) would only bring up the consensus level by 1 or 2%. In other words, I don't think it's fair to paint our survey as non-representative because of their inclusion.

    For more questions about or survey, see e.g. this FAQ.

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  27. Ikaika @ 17. The argument is in response to the fake skeptics' contention that there is significant disagreement among scientists, a tactic inherited from the tobacco industry. There is no significant disagreement. That's all the message of these studies.

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  28. Why are humans reluctant to wholeheartedly embrace the body of scientific evidence about manmade climate change?

    Human psychology influences the decisions we make every day, including unwise ones. Our psychological profile can make us reluctant to pay for services that benefit everyone, including those who don't contribute. It makes us focus on achieving short-term gains and avoiding short-term losses. And, most importantly, it prompts us to engage in rationalization and denial rather than tackle difficult challenges.

    Scientists suggest appealing to human psychology to create solutions to climate change by Rosemary Mena-Worth, Stanford News, Apr 13, 2016

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  29. @John #28

    Ok. I'll buy that argument. So then the obvious solution is to sever the link in the public mind that AGW mitigation requires payment of a fee/tax of any kind. If what you are saying is true, then it is a flaw in mitigation strategies that needs to be corrected so as not to meet such resistance.

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  30. MA Rodger@25.  Given that the conservatives in the UK have been in power since 2010 and won the last election fairly comfortably, the obvious conclusion from your argument is that most Britons are stupid.  

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  31. bartverheggen @26:

    "As we explain in the paper (on which John Cook is a coauthor by the way) the fraction of outspoken contrarians (based on the puiblic list by Jim Prall) in our sample is only a few percent, and the level of consensus if this group were excluded would be ~3% higher. But approx half of this group are actually publishing climate scientists, so excluding them wouldn't be entirely fair; only excluding the "non-scientist-contrarians" (if that were possible) would only bring up the consensus level by 1 or 2%. In other words, I don't think it's fair to paint our survey as non-representative because of their inclusion."

    Bart, the correct way to ensure the sample is representative is to exclude all members of the "contratrian" grouping who would not also have been included based on the other criterion for respondents.  Even just retaining "scientist contrarians" means that they could be included due to publication history in climate science or political statements agains effective policy on climate change.  In contrast, non-contrarian scientists could only be included based on publication history.  The effect is that including "scientist contrarians" who do not also appear as an author publishing on climate science is to bias the list in favour of contrarian opinions.

    Whether or not a group is representative depends on the absence of bias in the selection method for that group.  As it happens your selection method did have such bias, and the results are non-representative.  That is a different issue to how large is the impact of the bias, something you could have clarrified in your paper but chose not to.  Indeed, you have not done so even now in that the effect of the bias would be different when considering all responses compared to when considering only those responses from respondents with 10 or more papers.  I assume the 3% and 1-2% figures are related to the latter grouping.

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  32. Haze, RedBaron, denisaf

    Our present way of life, at least in the developed world, is healthy neither for us nor the planet.  I'm convinced, whether I'm right or not, that mitigation efforts to avoid dangerous warming would entail considerable change — upheaval — in that way of life.  We and the planet would be the better for it, but the people fighting such efforts don't see it that way — hence the campaign to bamboozle the general public into thinking scientists are still arguing amongst themselves about the reality or otherwise of climate change.

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  33. Tom (31),

    Contrary to your claim we did clarify in our article how large the impact on the consensus estimate was by including known contrarians:

    "As indicated, contrarian viewpoints are likely overrepresented
    in our sample (amounting to ∼5% of respondents), about half
    of whom have published peer-reviewed articles in the area of
    climate. However, this does not fully explain the difference with
    the abovementioned studies. Excluding those tagged as
    “unconvinced” more closely approximates the methodologies
    of earlier studies and increases the level of agreement, for
    example, from 84% to 87% based on Q1, excluding undetermined responses."

    By quantifying the approximate impact of their inclusion and seeing that it's very small, I stand by what I wrote earlier: I don't think it's fair to paint our survey as non-representative because of their inclusion.

    Also: Both Cook (2013) and Verheggen (2014) are partly based on the same sample, namely a WoS keyword search for global climate change or global warming. That includes many scientists who study climate impacts or mitigation. Many of them are not climate scientists in the sense of studying the physical climate system. That doesn't invalidate the findings of course, but it does mean that these surveys sample the wider scientific field wo have published on climate issues. In other words, for each survey you have to take into account what sample of articles/persons is being surveyd.

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  34. This will likely get the axe despite it making an important point that can't be made as effectively any other way ....

    If you went to 100 IT Specialists and 97 said you were in danger of being Hacked, 2 said they weren't sure and one said your Security is just fine don't worry, what would you do?

    If you are a Republican you'd OBVIOUSLY end up with a hacked computer and an empty bank account ....

    If you went to 100 auto mechanics and 97 said your brakes are gone, 2 said they weren't sure and one said don't worry you have plenty of brakes left, what would you do?

    If you are a Republican you'd OBVIOUSLY die from a car wreck (and stupidity) because your brakes failed ....

    If you went to 100 doctors and 97 said you have Cancer but it's treatable, 2 said they weren't sure and 1 said you are Cancer free don't worry what would you do?

    If you are a Republican you'd OBVIOUSLY die from an untreated Cancer (and stupidity)

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    Moderator Response:

    [RH] No all caps, please.

  35. bartverheggen @33, first, and for question 1, the percentage of all respondents that agreed with the IPCC (attribution of 50% plus) was 65.9% +/- 2%.  Your claim is that including the unconvinced shifts results by about 3%.  As that is larger than the uncertainty margin, the results are biased based on the inclusion of respondents based on their stated opinion rather than merely their publication history.  Ergo, the sample is nonrepresentative.  The bias is small, but small is not the same as non-existent.

    Because that bias exists, and differs in magnitude based on the number of respondents to each question, the effect of removing the bias by considering just that subsample of respondents included on the basis of publication (including overlaps with the unconvinced group) should also have been reported for each question IMO.  Failure to do so means you did not clarrify the impact of the bias.  I have no major objection to modifying that claim to "insuficiently clarrified the impact of the bias"; but as it stands the inclusion of "unconvinced" introduces a known bias of unkown quantity in the results as reported, so I think the stronger claim is justified.

    Have no doubt, I think that failure is a flaw in the paper.  It is particularly a flaw given that you must have known heading in to publication that AGW deniers would pick up on the paper and misprepresent it.  Limiting that misrepresentation by forcing them to ignore clear statements regarding the impact of the bias, and reporting the result absent that bias for each question inadvertently made that task of misrepresentation easier.

    This is a very specific criticism, and should not be misinterpreted as a general criticism of the paper (which I consider well concieved and and excellent addition to the quantification of the consensus on AGW).

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  36. Haze @30.

    I don't think we should dwell on this as it is off-topic here. But the Tories were in a coalition government 2010-15 which may have lulled many into a false sense of security with the Tories. And while the Tories did win a small majority in the 2015 elections allowing them to mis-rule alone, they achieved that small majority with a minority of the popular vote (37%) and a minority of the full electorate's support (24%). This may make one-in-four of the population candidates for being branded as 'stupid people' although JS Mill (as quoted @25) is quite definite to suggest not all would be 'stupid people'. I should also mention the FPTP system of voting employed in UK elections may give some of those Tory voters the excuse of not being Tories at all, but having voted tactically.

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  37. I hope it is not off topic here to ask whether there is a case for addressing the "consensus is not science" argument directly, as a myth in its own right? I appreciate that it isn't a claim about the content of the science itself, but it is a "metaclaim" about the methodology and philosphy of science in the context of climate. And it is an argument hat seems to come up frequently.

    Here, for what it's worth is how I'd frame a reply to the claim:

    Climate scientists don't base their conclusions on consensus. They base it on evidence, and that evidence is overwhelming.
    Consensus matters for the rest of us when we try to understand areas of science where we are not experts. That is when it is sensible to see what most true experts think. In this case they think that climate change is real and human-caused.
    In the same way, if I get cancer and someone claims that I can cure it myself with vitamin pills I will ask myself what the consensus of oncologists thinks.

    The common denialist meme says that "science does not work by consensus". Of course, that is true, but it is a straw man; nobody ever claims that it does. The point about consensus is that it arises amongst climate from the convergence or consilience of many strands of evidence, not that consensus is the evidence on which practicing climate scientists build their conclusions.

    So consensus is not central to the science itself, but to the understanding that the rest of us form as non-scientists (or at least non climate scientists). How else can a non-specialist form a well-founded opinion about any field in which they are not experts, but by asking themselves whether there is an informed consensus amongst actual experts? The only alternative would be for each of us to take advanced degrees in each field of expertise ourselves, before making a judgment. Good luck with that!

    (By the way, I think John Cook and colleagues are wise to shift from talking about consensus of evidence to consilience or convergence, to avoid confusion about that point.)

    Accepting the consensus is not a guarantee that we will be right. That's because neither science or any other form of human study promises certainty or "proof" (except, possibly , mathematics?). Consensus could be wrong, but at any one time it is the best bet, and other positions are sucker bets. It gives us the best chance of being right.

    Of course, that is only true if the consensus has arisen from well-founded scientific practice. Climate science is so formed, despite the deniers' best attempts to show otherwise. It is a mature, theoretically sophisticated field with a wide range of empirical and analytical methods at its disposal.

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