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Debunking 97% Climate Consensus Denial

Posted on 9 September 2013 by dana1981

Communicating the expert consensus is very important in terms of increasing public awareness of human-caused climate change and support for climate solutions.  Thus it's perhaps not surprising that Cook et al. (2013) and its 97% consensus result have been the subject of extensive denial among the usual climate contrarian suspects.  After all, the fossil fuel industry, right-wing think tanks, and climate contrarians have been engaged in a disinformation campaign regarding the expert climate consensus for over two decades.  For example, Western Fuels Association conducted a half-million dollar campaign in 1991 designed to ‘reposition global warming as theory (not fact).’

The 97% Consensus is a Robust Result

Nevertheless, the existence of the expert consensus on human-caused global warming is a reality, as is clear from an examination of the full body of evidence.  For example, Naomi Oreskes found no rejections of the consensus in a survey of 928 abstracts performed in 2004Doran & Zimmerman (2009) found a 97% consensus among actively publishing climatologists.  Anderegg et al. (2010) reviewed publicly signed declarations supporting or rejecting human-caused global warming, and again found over 97% consensus among climate experts.  Cook et al. (2013) found the same 97% result through a survey of over 12,000 climate abstracts from peer-reviewed journals, as well as from over 2,000 scientist author self-ratings, among abstracts and papers taking a position on the causes of global warming.

In addition to these studies, we have the National Academies of Science from 33 different countries all endorsing the consensus.  Dozens of scientific organizations have endorsed the consensus on human-caused global warming.  Only one has ever rejected the consensus - the American Association of Petroleum Geologists - and even they shifted to a neutral position when members threatened to not renew their memberships due to its position of climate denial.

In short, the 97% consensus on human-caused global warming is a robust result, found using several different methods in various studies over the past decade.  It really shouldn't be a surprise at this point, and denying it is, well, denial.

Quantifying the Human Global Warming Contribution

There have also been various studies quantifying the human contribution to global warming, as we have previously documented.

attribution 50 yr

Figure 1: Net human and natural percent contributions to the observed global surface warming over the past 50-65 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, light green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), Gillett et al. 2012 (G12, orange), Wigley and Santer 2012 (WS12, dark green), and Jones et al. 2013 (J12, pink).

Again, there's very little controversy here.  The scientific literature is quite clear that humans have caused most of the global surface warming over the past half century, as the 2013 IPCC report is expected to state with 95% confidence.

In Cook et al. (2013), we broadened the focus beyond definitions that quantify the human contribution, because there's a consensus gap on the mere question of whether humans are causing global warming.  Nevertheless, we used the 2007 IPCC position as one of our consensus position definitions:

"We examined a large sample of the scientific literature on global [climate change], published over a 21 year period, in order to determine the level of scientific consensus that human activity is very likely causing most of the current GW (anthropogenic global warming, or AGW)."

The IPCC position (humans causing most global warming) was represented in our categories 1 and 7, which include papers that explicitly endorse or reject/minimize human-caused global warming, and also quantify the human contribution.  Among the relatively few abstracts (75 in total) falling in these two categories, 65 (87%) endorsed the consensus view.  Among the larger sample size of author self-rated papers in categories 1 and 7 (237 in total), 228 (96%) endorsed the consensus view that humans are causing most of the current global warming.

The self-ratings offer a larger sample size on this quantification question because of the limited real estate in a paper's abstract.  Most journals have strict word limits on their abstracts, so authors have to focus on the specifics of their research.  On the other hand, the author self-ratings are based on the full papers, which have much more real estate and are thus more likely to both take a position on the cause of global warming, and quantify the human contribution.

Confused Contrarians Think they are Included in the 97%

There have been a number of contrarians claiming that they are part of the 97% consensus, which they believe is limited to the position that humans are causing some global warming.  The first error in this argument is in ignoring the fact that the data collected in Cook et al. (2013) included categories that quantify the human contribution, as Andrew Montford and the GWPF recently did, for example.

The second error has been made by individuals claiming they're in the 97%, but failing to actually check the data.  For example, Roy Spencer claimed in testimony to US Congress that he is included in the 97% consensus.  Since we made all of our data available to the public, you can see our ratings of Spencer's abstracts here. Five of his papers were captured in our literature search; we categorized four as 'no opinion' on the cause of global warming, and one as implicitly minimizing the human influence.  Thus Spencer's research was included in the fewer than 3 percent of papers that either rejected or minimized the human contribution to global warming.  Bjorn Lomborg made a similar error, claiming:

"Virtually everyone I know in the debate would automatically be included in the 97% (including me, but also many, much more skeptical)."

In reality Lomborg is included neither in the 97+% nor the less than 3% because as far as we can tell, he has not published any peer-reviewed climate research, and thus none of his writings were captured in our literature search.  The 97% is a consensus of climate science experts, and that, Lomborg is not.

Nir Shaviv took the opposite approach, claiming he was wrongly included in the 97%.  Though Shaviv also admitted that Cook et al. correctly classified his abstracts based on their content, but claimed that he worded the text in a way to slip it past the journal reviewers and editors.

"I couldn’t write these things more explicitly in the paper because of the refereeing, however, you don’t have to be a genius to reach these conclusions from the paper."

However, Shaviv, Spencer, and all other authors were invited to participate in the self-ratings process that resulted in the sae 97% consensus conclusion.

Tol's Rejected Comment

Richard Tol has also advanced various criticisms of Cook et al. (2013).  It's worth noting that Tol does not dispute the existence of the consensus, writing:

"There is no doubt in my mind that the literature on climate change overwhelmingly supports the hypothesis that climate change is caused by humans. I have very little reason to doubt that the consensus is indeed correct."

Tol has nevertheless criticized the methods applied during the Cook et al. survey.  For example, he has argued that the literature search should have been conducted with Scopus rather than the Web of Science in order to capture more papers, but also that fewer papers should have been included in the survey in order to focus on those specifically researching the causes of global warming.  Tol has also applied various statistical tests comparing the abstract ratings to the author self-ratings, but these tests are invalid because the two phases of the survey considered different information (abstracts only vs. full papers) and are thus not comparable.

In fact, when we released the self-rating data, we explicitly discussed the difference between the two datasets and how the difference was actually instructive.  As John Cook wrote,

"That's not to say our ratings of abstracts exactly matched the self-ratings by the papers' authors. On the contrary, the two sets measure different things and not only are differences expected, they're instructive."

Ultimately Tol submitted his criticisms to Environmental Research Letters as a comment, but the submission was summarily rejected by the editor who described it as a speculative opinion piece that does not identify any clear errors that would call the paper's conclusions into question. 

In short, the 97% consensus has passed peer-review, while Tol's criticisms have not.  Moreover, all of Tol's criticisms only apply to the abstract ratings, while the self-ratings also found the same 97% consensus result, completely independent from the abstract ratings.

Taking Consensus Denial to the Extreme

One critique of the consensus has been published in a paper in the journal Science & Education.  The argument made in the paper was first published by Christopher Monckton on a climate contrarian blog.  Monckton has also suggested the conspiracy theory that the journal Environmental Research Letters was created (in 2006) specifically for the purpose of publishing Cook et al. (2013).

The Monckton paper takes the point about quantification above to the extreme.  It focuses exclusively on the papers that quantified human-caused global warming, and takes these as a percentage of all 12,000 abstracts captured in the literature search, thus claiming the consensus is not 97%, but rather 0.3%.  The logical flaws in this argument should be obvious, and thus should not have passed through the peer-review process. 

Approximately two-thirds of abstracts did not take a position on the causes of global warming, for various reasons (e.g. the causes were simply not relevant to or a key component of their specific research paper).  Thus in order to estimate the consensus on human-caused global warming, it's necessary to focus on the abstracts that actually stated a position on human-caused global warming.

When addressing the consensus regarding humans being responsible for the majority of recent global warming, the same argument holds true for abstracts that do not quantify the human contribution.  We simply can't know their position on the issue - that doesn't mean they endorse or reject the consensus position; they simply don't provide that information, and thus must first be removed before estimating the quantified consensus.

As noted above, when we perform this calculation, the consensus position that humans are the main cause of global warming is endorsed in 87% of abstracts and 96% of full papers.  Monckton's argument is very similar to the myth that CO2 can't cause significant global warming because it only comprises 0.04% of the atmosphere.  99% of the atmosphere is comprised of non-greenhouse gases, but these other gases are irrelevant to the question of the CO2 greenhouse effect.  The percentage of CO2 as a fraction of all gases in the atmosphere is an irrelevant figure, as is the percentage of abstracts quantifying human-caused global warming as a percentage of all abstracts captured in our literature search.

It's also worth noting that based on Monckton's logic, only 0.08% of abstracts reject human-caused global warming.

Climate Consensus Denialism

Overall, the critiques of Cook et al. (2013) have all exhibited the characteristics of scientific denialism.  Given the long history of consensus denial campaigns by fossil fuel interests and climate contrarians, continued resistance to the consensus is an expected result.  Nevertheless, the 97% consensus is a robust result from several different studies taking a variety of approaches, including two independent methods used by Cook et al. (abstract ratings and author self-ratings).  The criticisms of the paper have all exhibited the same few logical flaws, some more extreme than others, but all erroneous.

Note: this post is the new rebuttal to the myth 97% consensus on human-caused global warming has been disproven

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Comments 1 to 35:

  1. Indeed, that shameful article in Science & Education (I'm not afraid to use such epithet given the fundamental statistical error they've apear to have made) is co-othored by Monckton himself. I think this is technically the first peer reviewed article by Monckton because I don't know of anything to his credit, please correct me if I'm wrong.

    Minor glitch, Dana. Given Monckton's conclusion, that "the consensus is not 97%, but rather 0.3%", then it appears to be a typo in this sentence:

    ...based on Monckton's logic, only 0.08% of abstracts reject human-caused global warming.

    The two numbers, suggesting the consensus set is just 4 times larger than the rejection set, do not make sense. I would rather expect the "rejection rate" to be 0.008% in this context.

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  2. Agreed

    I'm surprised ayone takes Monkton seriously given his track record. For anone who hasn't seen Potholer54 (Peter Hadfield's) excellent YouTube series on Monkton Monkton Bunkum Part 1 and following part 2 to 5 etc. I would strongly recommend as a masterclass in how to demolish a climate change "Skeptic."

    Chriskoz I think you are right about this being Monkton's first peer reviewed journal.


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  3. Silly question?  In figure 1, how is the % contribution from Humans higher than 100%?  Not sure I am reading that graph right.

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  4. joeygoze - Because natural forcings have over time declined; in the absence of anthropogenic factors the Earth would have cooled over the last century.

    In other words, without offsetting from natural cooling, we would have instead warmed by over 0.9C, rather than the observed 0.7C over that time, due to anthropogenic forcing. 

    Anthropogenic + natural versus natural only

    Modelled Anthropogenic + Natural forcings vs. Natural forcings only [Source]

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  5. Got it, thx.  Follow on question - so then I assume the graph of Anthropogenic vs.Natural forcings only is going to look more like graph A vs. B?

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  6. chriskoz @1 - 0.08% is right.  The difference is a factor of about 4 because while we had 65 abstracts in Category 1 (AGW > 50%), Monckton claims the number should have been in the 40s (and 10 abstracts were in Category 7, AGW < 50%).

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  7. What _exactly_ is the 97% consensus that is agreed upon?  The first link in this article it appears that the consensus is simply that humans cause _some_ warming -- not quantified, and definitely not explicitly greater than 1/2 of observed warming.


    Does anybody know what level of consensus there is for the statement "Humans have caused greater than 1/2 of the observed warming since xxxxx date" ?  (Pick any date).

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  8. Charlie A @7, first, I see no indication at the first link that the consensus is that humans cause "some" global warming.

    Second, it is not possible to interpret the Cook et al survey consistently such that each rating category is unique (ie, so that papers do not fall into to rating categories) without interpreting "AGW" as being a theory that implies that at least 50% of recent warming (typically ascribed as the last 50 years, or since 1950) has an anthropogenic cause.  As surveys should be interpreted as consistent if they can be, that means Cook et al find that 97% of papers discussing the issue endorse the theory that >50% of recent warming has been anthropogenic in origin.

    Suggestions to the contrary are primarilly inspired by rhetorical needs rather than analysis.  This is seen in that:

    a)  The initial response of so-called "skeptics" was to argue that papers had been incorrectly classified as endorsing the the consensus, when the papers involved all acknowledge that increasing CO2 will cause some warming.  That initial response is inconsistent with the same "skeptics" later claims that to "endorse AGW" means just to endorse that increased CO2 will cause some warming; and

    b)  The response in self rating showed a higher tendency to rate the papers as "rejecting AGW", than the abstract ratings, thus showing the authors of "skeptical" papers interpreted the "rejection of AGW" as being consistent with accepting some warming from increased CO2.

    It was only when initial rhetorical attacks on Cook et al failed to get traction that "skeptics" suddenly "discovered" that everybody endorses AGW.  Interestingly, this same rhetorical tactic has been used on every prior paper showing a consensus in support of AGW.

    So, in answer to your final question, the proportion of climate scienctists who agree with the claim that most (>50%) of recent warming has an anthropogenic cause is almost certainly >90%, and probably greater than 96%.  We know this not just from Cook et al, but from a variety of other studies examining the consensus.

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  9. Q. Why do deniers on facing the consensus of 97% of scientists on the cause of Global Warming have a the same look as a puppy who has had his nose rubbed in his own excrement?

    A. They both think you owe them an explanation about something incomprehensible to them both!

    That is why both still prefer cherry picking red herrings. The denier will seize on any distraction and the puppy will simply chase its tail or any other suitable smelling bit.

    Disclaimer. Rubbing you puppies nose in his own excrement will not work to house train it. It only makes you feel better.


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  10. Tom Curtis @7, a nonclimatic comment on 'most (>50%) of recent warming':

    For many people (like you), 'most' means 'more than half'. For many others (like me), it means 'the great majority'--with a fuzzy boundary, maybe around 70%, depending on what the most is most of. When the difference is pointed out, people from both sides are often incredulous that anyone could honestly hold to the other meaning. See, which argues that experiments show even us great-majoritarians are more-than-halfers if we'd only admit it.

    The point of which is to say that when talking about 'most of recent warming' (or anything else), it's good to add numbers to clarify, as you did. Kudos.

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  11. I agree that it is difficult to interpret the Cook et al survey consistently such that each rating category is unique.  That is one of the several flaws in the paper that make interpretation of what the paper says somewhat vague.  But if you look closely at what the paper actually says instead of how 3rd parties describe it, you will find that even a paper that just discusses method of carbon sequestration is considered to be part of the 97% that "endorses AGW".   Clearly such a paper is NOT making a claim that greater than 1/2 of the observed warming is anthropogenic.

    In looking at the paper itself, , Table 2 shows that there were 8 rating categories (counting 4a and 4b as two). 

    Category 1 is "Explicitly states that humans are the primary cause of recent global warming"

    Category 2 is "Explicitly states humans are causing global warming or refers to anthropogenic global warming/climate change as a known fact" and gives as an example "‘Emissions of a broad range of greenhouse gases of varying lifetimes contribute to global climate change"

    The paper then merges categories and never discloses what percentage of papers were evaluated as Category 1.

    In fact, the merged "endorses AGW" category includes category 3: "Implies humans are causing global warming. E.g.,research assumes greenhouse gas emissions cause warming without explicitly stating humans are the cause", with the example of "‘. . . carbon sequestration in soil is important for mitigating global climate change"

    So, as I read the article, almost any paper that discusses mitigation was considered to be "endorsing AGW".

    Clearly, a category 3 paper is NOT in any way stating an opinion that the majority of observed warming is anthropogenic.


    If you look at the SI, you will note that in Table 5, the comparison with Schulte (2008) only results for Categories 2 through 6 are reported.  Category 1,

    As for self rating, those are available at

    While there are a few category 1 self classifications, they are rare.  The self classifications definitely do not support Tom Curtis's statement of "...the proportion of climate scienctists who agree with the claim that most (>50%) of recent warming has an anthropogenic cause is almost certainly >90%,".

    Don't take my word for it.  Go to the data file and see for yourself how few papers are category 1 --- and this is in the self-selected sample of climate scientists that chose to respond.

    explicit statement that humans have caused the majority of warming, is omitted. 

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  12. @Tom Curtis, #8, You say "So, in answer to your final question, the proportion of climate scienctists who agree with the claim that most (>50%) of recent warming has an anthropogenic cause is almost certainly >90%, and probably greater than 96%."

    1.  Do you agree that a paper that states that most of recent warming has an anthropogenic cause would be classified as a Category 1 paper?

    2.  What percentage of the 12,000 abstracts reviewed were classified as Category 1?

    That is a very basic, simple question that should have been clearly disclosed in the Cook paper, but was not.  Perhaps you have some inside info and can report the actual category breakdown before Categories 1, 2, and 3 were merged.




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  13. Charlie A: "But if you look closely at what the paper actually says instead of how 3rd parties describe it, you will find that even a paper that just discusses method of carbon sequestration is considered to be part of the 97% that "endorses AGW". Clearly such a paper is NOT making a claim that greater than 1/2 of the observed warming is anthropogenic."

    Few of the papers made that explicit claim, with no surprise.  Only a relative handful are attribution studies.  Implication, then, becomes necessary (unless you'd rather the consensus be based only on attribution studies . . . in which case we get to stop nitpicking and move on to more serious topics, because your pinhole poking project won't have anything to work with).  If a paper is discussing carbon sequestration, what is the likelihood that it's simply an exercise that has no real world application?  It's much more likely that the paper is examining mitigation of the developing situation.  If the anthro component is not greater than 50%, then the likelihood of there actually being a problem is greatly reduced vs. the current range of attribution (75%-200%, depending on the method and period).  Perhaps you can point to the specific paper working on sequestration.  I suspect that it probably says nothing about attribution but does make the assumption that there is a rapid rise in atmospheric CO2 and that it is the basis of a serious, developing problem.  How else would such a paper be justified for inclusion in a major journal?  Given current data, the only situation in which sequestration is seriously considered is one in which CO2 continues to rise at an unprecedented rate (Honisch et al. 2012), a situation that requires the human component to have been and continue to be greater--much greater--than 50%. 

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  14. Charlie A - If you disagree with those abstract classifications (asserting, as you seem to, that the raters for Cook et al 2013 somehow mistook papers indicating a small anthropogenic contribution as fully endorsing AGW as the primary cause, despite clear protocols and repeated statements by the authors as to their criteria), then I have a suggestion for you in order to prove your case.

    Check the data yourself. 

    Go to the ratings page, and run through a hundred or two abstracts, rating them yourself as to endorsing/rejecting a consensus opinion of a majority contribution to global warming by AGW. Then look at your statistics - feel free to ignore the 'implicit' categories, if you like - and see just how many of the abstracts expressing an opinion endorse the consensus. I've tried it; it should require only the investment of a couple of hours to rate 100 or so. 

    Because quite frankly the multiple attempts to reinterpret this paper and dismiss its results, like yours, are both tiresome and completely evidence-free. The data is sitting right there for the review. If you don't, well, to quote Christopher Hitchens, 

    What can be asserted without evidence can be dismissed without evidence.

    Lacking evidence to the contrary, Cook et al 2013 (as well as Doran et al, Anderegg, Oreskes, and similar studies) stands as correct, and the vast majority of people in the field agree that AGW is the primary cause of recent climate change. 

    No evidence? Then you have no case, just rather empty rhetoric.

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    Moderator Response:

    [DB] Fixed text per request.

  15. #13 DSL asks "perhaps you can point to the specific paper working on sequestration"

    the sequestration example is quoted directly from the Cook paper as an example of an abstract statement that would cause a paper to be classified as part of the 97% consensus.

    See Table 2, which gives an example of category 3, part of the 97% consensus as " ... Carbon sequestration in the soil is important for mitigating climate change"

    That is the full quote from the Cook paper, including the ellipsis.

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  16. Charlie,

    How is your reading comprehension?  

    Tom said, " is not possible to interpret the Cook et al survey consistently...without interpreting "AGW" as being a theory that implies that at least 50% of recent warming...". (my emphasis)

    and you respond with, "I agree that it is difficult to interpret the Cook et al survey consistently such that each rating category is unique. That is one of the several flaws..."

    Charlie, you appear to be deliberately trying to obfuscate. You are agreeing with something Tom did not say. Especially since the numbers you ask for at 2 make as much sense as asking, "How many of the papers which took no position took position A?"  Yours is a nonsensical question, not because the answer can't be determined from the published paper (which it can be), but because the answer has no meaning.  

    Further, Tom answers your question regarding, "proportion of climate scienctists", and you counter with statements about articles.  Scientists != articles.  You led Tom into answering a questing about the consensus amongst scientists, and then countered with statements about articles.

    In the end, what difference does it make?  Any paper in categories 1-3, in conjunction with knowledge of climate change impacts, can only be interpreted to support the position that humans are better off attempting to mitigate climate change than not.  I suppose that opens the door for another round of "It's not bad.", but we've been there before, and that topic is orthogonal to the topic of "Are we causing climate change?".

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  17. Charlie A - So by your understanding an abstract discussion the importance of carbon sequestration in mitigating climate change (implying sequestration of CO2 to reduce climate change), with CO2 increases coming from anthropogenic emissions (more evidence than needed) is in some fashion not implicitly stating that that AGW is the major cause of recent climate change? 

    Please, explain - I would love to see how you justify that claim. 

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  18. Charlie, one last thing, regarding :  "Do you agree that a paper that states that most of recent warming has an anthropogenic cause would be classified as a Category 1 paper?"

    You can't do attribution without a quantification and a model to test that quantification, and the survey of papers was not limited to papers on models.  So, even assuming some agreement on what "most" means, that was not the question this paper attempted to answer.  Feel free to conduct a survey papers on climate models, and let us know what the percentage fall in the category of agreeing that "most" is caused by humans.

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  19. If there really is a 97% consensus, it make the conspiracy among scientists many deniers believe in all the more complicated. I think too complicated to be even possibly true. Its too bad they don't just be patient wait to see if the science proves them right, instead of engaging in smears.

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  20. Charlie A @11, you cannot agree with me that Cook et al survey is difficult to interpret consistently, for I neither said, nor believe anything like that.  Rather, it is impossible to interpret it consistently if you insist "AGW" refers to a theory that humans caused some, but potentially less than 50% of recent temperature rise in any rating category (1-7); but it is trivially easy to interpret it consistently if you interpret "AGW" as refering to a theory that humans caused >50% of recent warming.  That you insist on retaining an interpretation of AGW which makes a consistent interpretation of the survey impossible despite the fact that the consistent interpretation is the most natural shows you are playing rhetorical games rather than making genuine inquiries.

    It is easy to show that the theory endorsed by ratings 1-3 is that humans have caused >50% of global warming.  The most damning evidence so far as the fake "skeptics" go is that they nearly universally so interpreted it while the survey of authors was being conducted, and in their initial attempts to criticize the results of Cook et al.  There sudden fervour for an alternative interpretation gives a clear mark of how honest they are in this debate.

    Further, in both the introductory remarks in the survey of authors, and in each of rating categories 2 and 3, authors are asked if their paper explicitly states, or implies that "humans are causing global warming".  Natural interpretation of statements about causes requires that they be relevant.  If, when asked what caused the collapse of a bridge, for example, you respond by describing a factor that only contributed 10% to the collapse, while ignoring more dominant factors, you would rightly be regarded as lying by omission.  Consequently, the natural interpretation of those instructions asks whether or not humans are the dominant cause of global warming (which in context refers to the warming in the late twentieth century).

    This linguistic convention is very standard, and is why fake "skeptics" had no difficulty in interpreting the survey exactly as I do until it became rhetorically convenient to suggest another (unwarranted) interpretation.

    Finally, the most compelling evidence relates to the logic of the various responses.  It is impossible to interpret the scale (1-7) as a ranking in terms of "percentage of endorsement" where that is a ranking in terms of the percentage contribution to recent warming.  If we attempt to do so, we must rank 1 as >50%, 7 as <50%, and all other values as being in the range >50% to <50%.  Further, we must interpret endorsement as indicating greater than a particular value, and rejection as indicating less than.  I await any attempt to interpret the scale using these restrictions that does not show ranks 2 and 3 as endorsing >50% anthropogenic warming.

    The alternative interpretation is that the differences between ranks 1-3 and ranks 5-7 is not in the level of causation, but in the explicitness of the endorsement.  All of 1-3 endorse >50% anthropogenic warming, but papers rated 1 are most explicit in doing so, whereas in papers rated 3 the endorsement relies on implication.  The difference between ratings 1 and 2 is that supplying numbers or quantifiers removes doubt about the endorsement - not that they endorse different things.   

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  21. Bjorn Lomborg is definitely not a climate scientist. He is not even a reasonable economist.

    He has published comparisons of the future costs faced by future generations vs. the benefit/costs of today's generation and claims that a current generation allowed to pursue its best present for itself will develop a better future for later generations, even though the free action of the free market has never shown any inclination to do that, except by purest accident.

    His evaluations overstate the "costs" that the current generations would suffer (actually not costs at all, just less benefit) if they diligently reduced their activities that create admitted negative impacts on the future. He then understates the future costs by optimistically evaluating future consequences and limiting the consequences to the ones faced by the most fortunate, and only evaluating "human related thought at all about any other life on our planet.

    He then applies the famous "Net Present Value” discounting of those optimistically low future costs "because that is what you do" and compares that number with the lost benefit he determined for the current generation.

    The fundamental concept of the evaluation is fatally flawed even without the distortions he incorporates. His evaluation basically says a current generation can create added costs a future generation will have to deal with as long as they think the benefit they would lose by not creating those future costs would exceed the costs they think they are creating.

    These are not the thoughts of a rational reasonable person. And yet even the US government uses that same type of analysis when determining the net benefit of something they are considering allowing to be done, like a new pipeline.

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  22. Charlie A @7, to quote myself from above,

    "The IPCC position (humans causing most global warming) was represented in our categories 1 and 7, which include papers that explicitly endorse or reject/minimize human-caused global warming, and also quantify the human contribution. Among the relatively few abstracts (75 in total) falling in these two categories, 65 (87%) endorsed the consensus view. Among the larger sample size of author self-rated papers in categories 1 and 7 (237 in total), 228 (96%) endorsed the consensus view that humans are causing most of the current global warming."

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  23. jwhite100@ 20.

    Please state your point(s) in another way. I'm not sure I know what you are trying to say.

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  24. I note that Chris G @17 more than adequately answers Charlie A @12.

    I will note that one of the most damning facts about critics of Cook et al is that they do not employ one of the best, and well known, surveys of the opinions of climate scientists as a counter argument.  Bray and von Storch (2010) explicitly asked a broad range of climate scientists, "How convinced are you that most of recent or near future climate change is, or will be, a result of anthropogenic causes?" (Question 21).  On a scale of 1-7, with 1 being "not at all convinced" and 7 being "very much convinced", 83.51% responded 5 or higher, while only 11.081% responded 3 or less.

    I think this survey question poorly framed.  IMO, somebody who thinks that there is a 5% probability that it will rain today and a 95% probability that it will not is not "a little convinced that it will rain".  Rather, they are mostly convinced that it will not.  Therefore, as the survey question is asked, anybody who responds with a value greater than 1 is at least 50/50 on the proposition, and likely much greater.  Of course, people understand the context of survey questions, and will often treat the middle value as 50/50 even when the logic of the question suggests they should not.  As a result, and as a result of the significant disagreement with other relevant surveys, I consider the poor framing of the question to have biased the result low.

    I must recognize, however, that the 83.5% is a defensible position.  Somebody arguing that Cook et al over represents the "consensus" in that Bray and von Storch show the consensus of actual scientists (as opposed to papers) to be 83.5% has an arguable case.  Despite this, the fake "skeptics" do not argue this case for it would require admiting an 83.5% agreement the claim that most recent or near future warming was or will be the result of anthropogenic factors.  Worse, it requires recognizing that only 1.351% of climate scientists are certain that this is wrong.

    Even more troubling for the fake "skeptics", however, is that 78.92% of climate scientists are significantly convinced (>4 reponse) that "...climate change poses a very serious and dangerous threat to humanity" (question 22).  "Humanity" is vague as to whether the threat is merely to very large numbers (hundreds of millions, or billions) of humans, or whether it is a species level threat, ie, a threat of extinction.

    It is a difficult task you set yourself when you attempt to obfusticate and confuse the public on climate science.  You must thow over even reasonable arguments that appear to support your position, for using them will let too many facts out of the bag and loose you any thoughtful people.

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  25. "Lord" Monckton is another unreasonable economist who likes to play the game the way Lomborg does (my earlier comment @21), and he was even able to partcicipate in ruling England for a while.

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  26. One often-unsaid aspect of the public discussion on whether human-induced climate change is real, is ideology. Several months ago, the University of Kentucky hosted of forum on climate change with three excellent speakers who were all self-described conservatives. Liberals reported how they better understand that there are thoughtful conservative perspectives on, and solutions to, climate change, thus allowing for a broadened public discussion. In turn, conservatives in attendance learned the same thing. You can watch the recording of this event at The starting time for each speaker is noted at this page, so you can listen to the speakers of greatest interest to you.

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  27. Tom Curtis@28

    I would encourage you to stop legitimizing the denialist argument that "Reasonable estimates range from economic damage significantly greater than the cost of mitigation...".

    The comparison of the "cost of mitigation faced by a current generation" with "that current generation's estimate of the future economic damage it is inflicting on a future generation" in not a "reasonable thing to do".

    More important is how sustainable a human activity is. Humanity should be planning to be living forever on this one and only planet. That would mean developing ways of living that can be continued forever. The way of living that has recently developed due to the burning up and consumption of non-renewable resources is fundamentally not sustainable. It is definitely popular, but everyone cannot develop to live the life of the most fortunate which is socially not sustainable. Actually, even just the few most fortunate would not be able to live their lifestyle forever.

    The understanding that it is essential to develop truly sustainable ways of life that all humans can develop to and improve on forever needs to be the fundamental principle guiding all decisions about "acceptable human behaviour".

    Popularity cannot be allowed to influence decisions about what is acceptable. That won’t have a 97% consensus of popular opinion, but it is the only way for humanity to have a better future for all life on our ones and only planet.

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  28. OPOF @29, you have clearly misuderstood what I wrote.  I specified the range of damage estimated that IMO can reasonably be held regarding BAU.  The lower end of that range is costs significantly greater than the cost of mitigation.  Nothing in that statement implies in anyway that it is acceptable to incur those costs against future generations for the benefit of reduced costs by avoiding mitigation today.  Indeed, for the majority of still living humans (anyone under 40) the cost within their lifetime of not mitigating is likely to be higher than the cost of mitigating.

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  29. Absolute agreement with following:

    (29:One Planet Only Forever)

    "The understanding that it is essential to develop truly sustainable ways of life that all humans can develop to and improve on forever needs to be the fundamental principle guiding all decisions about "acceptable human behaviour".

    Popularity cannot be allowed to influence decisions about what is acceptable. "


    How can there be any argument with that?  We are reaping the consequences of NOT adhering to these simple declarations.   In a closed system "what goes around comes around".

    Everywhere you look, there are UNsustainable realities:  population, city growth, pollution, water use, etc etc...  All interrelated, nothing separate.

    What is civilization "worth"?  What is the human race "worth"?  What is all life on this planet "worth"?


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  30. Tom Curtis, I appreciate that your comment indicates the cost of mitigation should be comsidered to be less than the future costs created without tat mitigation, but that is still playing into the delayer/denier game of discussing the relative evaluation. They will claim there is no concensus about the relative values.

    It is simply unacceptable for a current generation to enjoy benefits from actions that create any potential problem for a future generation. It is even more uncceptable to discuss the comparison of the magnitude of the problem being created with what the current generation thinks they deserve to benefit from.

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  31. Given the low number of articles found which express the IPCC position (i.e. that humans are responsible for most of the recent warming), does this paper support the proposition that the extent of attribution is not a widely researched question?

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  32. Ironbark - As the paper itself clearly states:

    This result is expected in consensus situations where scientists '...generally focus their discussions on questions that are still disputed or unanswered rather than on matters about which everyone agrees' 

    It's been researched for over 150 years, and as per the observed consensus, the basic outline of AGW is no longer a question that requires discussion. 

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  33. Ironbark - My apologies, I may have in haste misread your post. Regarding the details of attribution, there is a lot of work ongoing, see here

    Regarding the basics of human influence being the dominant factor in warming, no, there isn't much research going on - as that's been very well established. 

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  34. Was Doran & Zimmerman (2009) considered peer-reviewed?  Because many denier blogs keep pionting this out as a point to their side. 

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  35. joeygoze @ 3

    Not a "silly question", just a tricky one.
    I would answer: keep in mind that, f.e., energy required for ice melting and due to GHGs (our "contribution") does not increases temperatures ...
    You also have an explanation from "skepticalscience":
    "... Most studies showed that recent natural contributions have been in the cooling direction, thereby masking part of the human contribution and in some cases causing it to exceed 100% of the total warming".

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