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The 97% consensus on global warming

What the science says...

Select a level... Basic Intermediate Advanced

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.


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


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


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Comments 701 to 750 out of 899:

  1. LeonD - I expect you're doing a 'drive-by', rather than actually engaging in conversation, but I would ask you to consider just what proportion of peer-reviewed biology papers make explicit statements for or against the validity of evolution in their abstracts? And whether you, for some reason, think the large percentage of such papers not restating known facts is in some fashion disagreement with evolution?

    The same holds of climate science. In fact, I suspect the estimated percentage of disagreement on climate is biased towards the negative (that the percentage might be lower than 3%), since authors disagreeing with the consensus have far more reason to mention AGW than authors who treat it as a known and understood background to the data. 


  2. The source is the paper itself: 

    Specifically Table 5

    I am referring to the self-rated results but the abstract results are even less in favour of AGW.

  3. LeonD - I'll repeat my question: do you think the high percentage of biology papers that fail to state a position on evolution are in fact evidence that biologists disagree with it? Or that the infinitesimal number of modern physics studies stating a position on the existence of atoms represents evidence of major disagreement there?

    There's no need to repeat known facts, especially in the limited space of a paper or even more so the 200-500 words of an abstract  - your argument is absurd.

  4. I cannot find the reference at the moment, but as I recall Naomi Oreskes noted that as a scientific consensus grows the explicit mention of that consensus declines - because, again, there's no need to repeatedly tell your audience that water is wet, or that a clear sky is blue...

  5. My mistake, I thought they were querying the authors on their own views not on what their papers were saying.  

  6. LeonD...  I think that's a very common mistake. Relative to the Cook13 paper, many people fail to discern the difference between "position" and "opinion."

  7. For a survey of scientific opinions, rather than the published work, see Doran 2009, whose survey found that among scientists who had more than half of their recent work on climate (i.e., who are actively researching the matter), 97% agreed that: 

    "...human activity is a significant contributing factor in changing mean global temperatures".

  8. KR @707, I think insufficient attention has been paid to uncertainty intervals with regard to the concensus.  In particular, in the case of Doran, Kendall and Zimmerman (2009), the sample size for question two, ie, the question on attribution, is only 77.  

    Calculating uncertainty depends not only on the sample size, but also (weakly) on the size of the total population.  In the case of climate scientists, the total number of climate scientists in the world is an unknown.  However, based on a literature review, Verheggen et al (2014) found the emails of approximately 8000 people, of which approximately 7600 where climate scientists (the other 400 being contacted because they where known "skeptics".  On that basis, the total number of climate scientists in the world is likely to be greater than 5000, but less than 50000.

    Using these figures and a confidence interval calculator, it is possible to determine that the 99% confidence interval is approximately is between + 2.6% and - 4.64 to 4.68%.  The larger of the two figures assumes 50 thousand climate scientists.  Of course the confidence interval calculator assumes a normal distribution, which is not possible in this case because there cannot be more than 100% concensus.  That is likely to mean the lower bound is understated by a small amount, but the 95% confidence interval almost certainly has a lower bound less than or equal to 4.7% based on these figures.

    More troubling for Doran is the actual question, which is:

    "2. Do you think human activity is a significant contributing factor in changing mean global temperatures?"

    (My emphasis)

    By asking if human activity is "a significant factor", it allows that other influences are as, or even more significant.  

    Taking significance to be "statistically significant", it asks whether global temperature increase since the "pre-1800s" would have been less than that observed by a statistically significant amount absent human influence.  Given the statistical uncertainty in determining pre-1800s temperatures (see graph below) that requires greater than 50% of the warming be attributed to anthropogenic factors.  I think this means the question must be understood colloquially, where "significant" does not imply "statistically significant".


    Colloquially, something contributing 25% of the effect would be considered "a significant contributing factor".  Arguably something contributing just 10% of the effect would also be considered "a significant contributing factor" but that is more dubious.  Taking the 25% benchmark, we can compare Doran et al to Verheggen et al, in which just over 90% agree that 25% or more of the warming is due to anthropogenic factors.  Allowing for the inclusion of approximately 5% known "skeptics" without regard of their scientific qualifications (and in most cases absent relevant scientific expertise), that result is qualitatively equivalent to Doran et al's.

    The upshot is that unless we are making the weak claim that the consensus is that anthropogenic factors are a significant factor in recent warming, we should no longer be citing Doran et al, and hence the 97% figure, for the percentage of scientists who accept the concensus position.  That is particularly the case given Bray and von Storch (2010) and Verheggen et al (2014), both of which post date Doran et al, have larger sample sizes and support a consensus figure in the high 80 percents.  In particular, Verheggen et al, excluding those invited because of their known "skeptical" opinion and without regard to their scientific qualification, find a concensus figure of 87% (85-89%). 

  9. Tom Curtis - I would agree that little attention has been paid to the uncertainty ranges on consensus estimates. However, as you yourself have noted WRT Doran, with perhaps the smallest sample, the uncertainty is <5% - meaning that even at the extrema we are still looking at a >90% consensus on AGW in the literature, and in at least some surveys of the expert opinions. (As I understand it, B. Verheggen is of the opinion that the lower number in their survey was actually due to a much more detailed/specific question, rather than the mean range thought appropriate - that the respondents didn't think they could narrow it down to the specificity given)

    And when you look at actual attribution studies in AR5, the fraction of warming due to AGW has a mean of 110%, with less than a 5% chance of anthropogenic causes being responsible for less than 50% of observed warming. That makes AGW not just a significant, but a dominant cause. 

    Quite frankly, the various arguments on consensus (and denial thereof by the pseudoskeptics) are equivalent to discussing the number of angels who can dance on a pin, given that by any measure the scientific consensus on AGW is as high as that on ozone depletion by CFCs, acid rain, or the dangers of smoking tobacco, in all of which we found the consensus sufficient to act. 

    We know enough to take appropriate action. 

  10. KR @709, Verheggen et al argue that the percentage of respondents excluding undetermined results (ie, "unknown", "I do not know" and "other") for both the qualitative and quantitative responses are equivalent.  Specifically, 84 +/- 2% of respondents agreed that 50% or more of "global warming since the mid 20th century" can be attributed to "human induced increases in atmospheric greenhouse gas (GHG) concentrations"; while 86 +/- 2% agreed that greenhouse gases had a moderate or strong warming contribution to the "reported global warming of ~0.8 degrees C since pre-industrial times".

    As an aside, the unequal time periods for the quantitative and qualitative questions substantially weaken that argument.  However, I think it is a no brainer that "I do not know" and "other" responses should not be included.  On the other hand, arguably "unknown" responses claim scientific ignorance (ie, it has not been determined adequately by scientists) rather than mere personal ignorance, and so should not be included.  Against that, an "unknown" response may merely indicate the respondent thinks it is not yet determined whether the greenhouse gas contribution was 75-100 or 100-125% (quantitative question) or a moderate or strong warming contribution (qualitative question).  Therefore while presumable some respondents answering "unknown" do not agree with the consensus, it is problematic including the "unknown" figures because doing so assumes that all who so answered disagreed with the consensus which is not at all certain.

    More important are the figures with no "unconvinced", ie, those deliberately invited to participate because of their "skeptical opinion" rather than because they are just scientists.  Excluding both "undetermined" responses and "unconvinced" invitees, 87 +/-2% agreed that 50% plus of recent warming has been due to anthropogenic greenhouse gases.  That does not lie in the uncertainty range of Doran et al. As Verheggen et al. is much more recent then Doran et al, we must therefore either conclude that there has been an approximately 10% slide in agreement with the concensus among climate scientists; or that differences in the questions made a substantial (approximately 10%) difference in the response.  The later is what I argue above, based on the difference between "a significant contributor" and "the major contributor".

    I completely agree with your final two paragraphs, but do not think that reason to by imprecise or selective when quoting determination of the size of the concensus.  That is, to the best of our current knowledge, ~87% of climate scientists (on attribution), and ~97% of climate science papers.  IMO those figures show that the approximately 13% of climate scientists who do not agree with the IPCC on attribution do not do so based on publishable evidence.  Put another way, it means that political opinion has influenced the scientific views of some climate scientists, but against the IPCC position, not for it (ie, in the opposite direction of the bias claimed by "skeptics"). 

  11. Response to sjw40364 on the appropriate thread.

  12. Okay so while a sceptic is mostly interested in checking (and if necessary refuting) new scientific claims, it is reasonable to discuss the "consensus" issue due to its importance to science as a whole.

    Ironically, there is no consensus on the meanings of the terms used to define this consensus. Does it mean a majority? Or just an important and strongly agreed minority? Do voices with authority carry sway, or is it democratic. Does it need to be "overwhelming" and is it, in fact? Is it absolute or is there internal dissent? Which human beings count as scientists? Which institutions act as gatekeepers thereof and what is their motivation?

    Rather than work trough all of these, I will simply ask the reader to consider whether it is healthy that you are being asked to accept the speakers' tacit definitions on these matters, as well as their unstated assumptions. You are being guided toward what is really more of a psychological sensation than any fact-based argument - the sensation of being part of something big and powerful. Maybe a sense of belonging and safety. Maybe moral superiority. Maybe the clarity that comes from being decisively led.

    If the reader is ready to understand their own (and their peers') fralties in such areas, then I do not need to discuss the history of systems of control and subjudication. If not, there's no point getting in to it except to suggest you may wish to begin with the Milgram experiment.

    Instead, I will take a single example, from the current article, of a flagrent manipulation of the meaning of "consensus" and surrounding terms: the 97% pie-chart.

    You thought it said 97% of scientists, right? No. It's 97% of papers. That's right there in the jpeg image itself but you didn't notice it. What else didn't you notice?

    If you read the underlying study, what 97% really agree with is somthing along the lines of "do you agree that (a) humans emit CO2 and (b) that the greenhouse effect is real". Your present author does, and so would be a part of the consensus!

    The trick here is a toxic mix of pedantry and tactical naivety - as so often seen among precotious fifteen-year-olds, but in this case carefully hidden within a typically dull metholodgy section in a paper. It is *pedantically* true that human CO2 plus greenhouse effect implies *probably* *some* human generated warming. But has human generated warming been *shown* to occur? Not implied. Is it problematic? Not implied. Significant? Not implied. Even detectable? Not implied. Nor does the position in the question even imply that there won't be compensating factors or that warming would even be harmful anyway.

    In summary, consensus taken in general is too subject to the frailties of the human condition for any wise person to pay any attention to it. Specific factoids, such as the 97% pie-chart (and there are others) may seem to lend concrete validity, but as soon as you check them you find nothing meaningful, only trickery. 

    Should we accept climate consensus because consensus exists around, say evolution? A real sceptic can answer this easily: the whole point of science is to investigate methodically the questions whose answers are *not* obvious on the surface. No scientist would ever be so intellectually lazy as to reason that since the climate consensus "sort-of looks like" the Darwinian consensus, that their underlying scientific validities should also match.

    Climate consensus is much more like a rainbow. Amazing to look at; vast and magical. But how many times do you have to check for that pot of gold before you accept there's really *nothing there at all*!

  13. A.R.S.Says @ #712 :

    To be blunt: the word consensus has a very plain, straightforward meaning in the English language.

    Your expressed "logic" is a complete failure, since you seem unable to connect words and concepts and realities.

    (btw, I must commend your sense of humour in choice of your nom-de-plume ~ the abbreviation is priceless.)


    [JH] Inflamatory & off-topic.

  14. I'm looking for the data on climate change. I haven't been able to find it. I don't care how many agree, I want to know what evidence they base their opinion on. I was taught to question, not swallow. Please just post the data on climate, not the politics of popularity. Thank you.


    [DB]  Data and codes are openly available, and have been for years:

    Note that the Muir Russell Commission was able to do a full global reconstruction from the raw data linked to from the above page, WITHOUT ANY CODE, in a mere 2 days (when asked, they replied "any competent researcher could have done the same).

    The Auditors over at McIntyre's Climate Audit have been struggling with their "audit" reconstruction for many years now.

  15. KiAnCa @ #714 : You have my sympathies, for your desire to gain good quality scientific information about the amount of global warming going, and how severely the problem is building. As you have doubtless already noticed, the mainstream media generally does a poor job in supplying realistic information ~ and it gives an inordinate amount of space to anti-science propagandists (with lawyer-type rhetoric designed to make you think black is white, or that there are so many "doubtful" shades inbetween, such that there is nothing meaningful in this whole universe).

    You will find a vast amount of science-based info on this website . . . but you have my sympathy, because that info is not presented as a giant-size single meal where you simply chew your way through from one end of the pie to the other end.

    Best (a) if you go to the Home page, central top region, and click on the small box titled "The Big Picture" . . . and then follow to areas that interest you,

    or (b) on the Home page, click on the nearby box titled "Newcomers, start here" . . . and look down to the second heading, titled "Good starting point for newbies" where [second line of the paragraph] you can click on "Warming Indicators" and from that go to "Evidence for Global Warming (intermediate)" . . . where you can follow your interests. I must  point out that this particular section generally holds info up to about 2010 ~ and so doesn't directly mention all the additional weight of scientific info in the last five years [i.e. all the newer "hot year" global records and even faster Ice Melt and sea-level rise]. No great matter, since the "sufficient evidence" was already overwhelmingly convincing, long before that date [indeed, in a recently publicised scandal, it appears that Exxon already had convincing evidence of the CO2/Warming problem by 1979],

    or (c) if your scientific education is already above average, then you can simply skip to the "Arguments" [on Home page] and pursue any of the 170+ "arguments" [arranged by Climate Myth] which interest you, and delve further from there. The Myths are quite entertaining, because the info there does neatly deflate all the rubbish/nonsense talked by the small number of shills & mavericks who oppose the mainstream science (i.e. the mainstream science which results in virtually all the climate scientists being in accord with the consensus of 97% . . . or nowadays more likely 99% )

    Good hunting ~ and please use the appropriate thread's Comments Section for any questions that you want clarified.

  16. One  of the human finger prints cited in the first week of the Denial course was that the atmospheric warming this century is unique in the fact of warming lower atmosphere and cooling upper atmosphere. What evidence from past warming episodes establises that this is unique to the current warming. How do we know what happened in the upper stmosphere in the past warming/ increased CO2 events?


    [Rob P] - A cooling upper atmosphere and warming lower atmosphere is a signature unique to the enhanced (increased) Greenhouse Effect. If we had a Tardis, we would be able to go back in time to the Paleoecene-Eocene Thermal Maximum (PETM) about 55-56 million years ago, a time of substantial natural global warming, and observe the Greenhouse Effect growing stronger.

    The enhanced Greenhouse Effect we are now measuring is a human fingerprint because the source of it is the continued emission of greenhouse gases, primarily carbon dioxide, produced by industrial activity. See the SkS post: Climate Change Cluedo.

  17. Thanks for Responce @Rob P and for the link to Climate Cluedo. I get that carbon isotopes are critical in determining CO2 sources and ways of determining concentrations but my question speicifically was what is it about a cooling upper atmosphere in conjunction with a warming lower atmosphere that is unique. Another way to ask this might be, why is the upper atmosphere cooling with increased GHG levels while the lower atmosphere continues to rise at a sharp rate compared to background seasonal oscilations? And how do we know that in the past when the lower atmosphere warmed, so to did the upper atmospthere, or did it just stay the same. (I only found three hits on the Cluedo page when searching "upper atmos" and they were all in comments. no hits for "lower atmos") 

  18. What you should be looking for is "stratospheric cooling". It is not an easily understood concept, but there are several attempts around the internet to explain it. At basic level, It falls out of the equations for radiative transfer if you increase a greenhouse gas. Other forcings that change the surface temperature like changing albedo, solar influx, or aerosols do not produce this effect.

  19. John writes: "Science achieves a consensus when scientists stop arguing"

    Actually that's a bit simplistic. A scientifi consensus is formed after a series of scientists are able to reproduce the work of the scientist advancing a hypothesis. This is done by publishing confiming/denying results in refreed journals. Tom make that possible, the person advancing the hypothesis first fully explains it, then describes how it was tested (the "mehtodology"), the observed data and the results.

    A scientific consensus isn't formed by simple agreement between scientists, it's evidence based and very much dependent on repeatable experiment. So while the consensus that CO2 is a "greenhouse" gas, meaning that like water vapor and methane it absorbs and radiates solar energy in known quanta, there is no consensus on the effect or "sensitivity" Earth's climate has to increases or decreases in it. Which is the problem.

    We know CO2 absorbs IR. Water vaport (H20) observes much more, so much more that IR astronomers put their telescopes as high as possible, on Mauna Kea, Medium Altitude soborbital platforms like the KAO and SOPHIA, and in low Earth orbit in order to get above H20. IR astronomers aren't particularly worried about CO2 because its effect is so small it just doesn't matter.


    [PS] Myths about water vapour are addressed under "water is the most powerful greenhouse gas". Make your arguments there. Offtopic comments will be deleted.

  20. "Tom" doesn't make it possible. "To make"

    "methodology" not "mehtodology"

    "vapor" not "vaport"

    "suborbital" not "soborbital"

  21. I was proof reading my post here on the last page of comments when I encountered this gem:

    "One of the human finger prints cited in the first week of the Denial course was that the atmospheric warming this century is unique in the fact of warming lower atmosphere and cooling upper atmosphere"

    Not sure who came up with this but it's trully choice. So how many folks were measuring the temperature of Earth's stratosphere 200 years ago? 500 years ago? 2000? 20,000 years ago?

    Whoever made up that fun fact should get a prize, it's a real whopper.


    [PS] try reading for understanding rather than demostrating misunderstanding before banding about accusations. The surface temperature of any planet can be altered by changing solar input, albedo, GHG composition or aerosols. Increases in GHG composition is unique in that it is only forcing change that will warm the surface but cool stratosphere.

  22. It would be very nice if this site allowed comments to be edited.

  23. @Pfc. Parts 
    I gather from you're tone your here to troll not to learn, understand or convey science. But if you're interested in the source you can listen the full interview with Ben Santer (lead author of the historic 1995 IPCC) here:

    He states, no known natural mechanisms or combination of natural causes  have that sustained effect, that human fingerprint, in this unquie way.

    My focus has been, in the last 10 years or so, on two things. One is the vertical structure of temperature changes in the atmosphere. If you look from the surface of the Earth right up into the stratosphere, 20 miles above the surface of the Earth, what we’ve actually observed in weather balloon measurements and satellite measurements is this complex pattern of warming low down and cooling up high. The lower atmosphere, the troposphere, has shown warming pretty much across all latitude bends, and the upper atmosphere has shown cooling over the last 30 to 40 years or so.

    It turns out that that pattern of warming low down and cooling up high is really distinctive. We know of no natural mechanisms that can generate something like that, sustained for three or four decades. Volcanoes can’t do it. The sun can’t do it. Internal climate variability can’t do it, nor can some combination of natural causes: volcanoes, the sun, and internal variability generate that complex pattern of warming low down and cooling of the upper atmosphere. The only thing that we know of that can generate that distinctive fingerprint is human-caused increase in heat-trapping greenhouse gasses, and human-caused depletion in the upper atmosphere of stratospheric ozone.

    It’s been fascinating over my career to look at ever-better satellite observations and ever-better model simulations and see that fingerprint pattern of human effects literally emerging from the noise. The best information we have now from our most recent research is that the chances of getting a fingerprint match between that human fingerprint pattern of warming low down and cooling up high and purely natural causes is infinitesimally small. The signal-to-noise ratio is greater than 10. That’s what our research tells us. There’s just no way of explaining what we’ve actually observed without invoking a strong human effect on climate.

  24. to Pfc.Parts @722 : you make a fair point, with your comment "It would be very nice if this site allowed comments to be edited."

    On balance though, that would not be a good idea ~ and I am sure you can picture the chaos and non-sequiturs which would occur as posters go back and modify their posts, even with innocent intent (let alone the malicious intent). Nope: to be fair to all, a non-self-modified posting system is definitely far better.

    Mind you, it could be reasonable to allow a poster to later insert a very obvious "corrigendum" paragraph at the end, to deal with clumsy bloopers / typos / or poorly-expressed phrasing . . . and this would help the flow of understanding in the commentary [rather than having such corrections appear later and quite possibly be half-buried by other intervening posts]. Such corrigendum would require clear demarcation and date/time label.

    But . . . there would probably need to be a 24 or 48-hour cut-off for such "grafted-on" corrections. And even there, I am sure you can picture how some posters would try to play games and thoroughly abuse such a system. So, overall, it's simpler to keep this as they are : and it also makes for a simpler and less vulnerable control of the comments column.

    [apologies for this off-topic excursion]

  25. If you read the sentence stating 97% support, it's a self selecting subset of the data,

    "of papers stating a position on human caused global warming"  

    of all the papaers in the Cook study,  only 0.5% Explicitly support and quantify AWG as > 50%.,  (64 out of 11944)

    of all papers stating a position, that number jumps to a whopping 1.5%.  (64 out of 3974)

    can someone explain to me how that equates to "consensus"

  26. flavoid, sure I'll explain:

    We only look at papers stating a position on the topic (of which 97% state that humans are causing most global warming) because factoring in papers which DON'T address the topic would be ridiculous.

    Papers on needlepoint don't state that humans are responsible for global warming... ergo no consensus. See? Ridiculous.

    Happy to help.


    [PS] Perhaps flavoid could clarify their position about "self-selected dataset" by providing examples of papers that dont support the consensus that would be missed by the selection procedure.

  27. Flavoid, to put it another way: your statements have gone well wide of reality ~ you have missed the truth by a country mile !

    I don't know how you managed to get it so wrong. Very likely, you haven't actually read the paper Cook et al., 2013. Even just a read of the the paper's Abstract [see link at the head of this thread] will show you how wide of the mark you are. Read with a calm mind, and you will see how straightforward it all is.

    You will then also note the excellent quality-control of the Cook paper ~ and how the surveyed papers' authors themselves have expressed the same 97%  via their own assessment.

    So the matter of consensus is quite clear, too.

    Even mavericks like Dr R. Tol have admitted (in a slightly curmudgeonly way) that the "consensus" is 90+% .

    If there is to be a valid criticism of the "97%" as shown in the Cook paper, then the criticism [today] would be that the 97% is based on somewhat dated information [i.e. being on papers averaging about 10 years old by now].

    A present-day and deep-searching survey would now probably show a climate-scientist consensus closer to 99% .

  28. Has anyone looked at the rebuttal from José Duarte regarding Cook's 97% consensus paper? (

    He makes quite a good case about various biases being in the methodology along with pointing out how the claimed standards have not been met in various ways.

    From what I can tell he makes a pretty compelling case that the 97% consensus is way overstated as a result of those errors.


    [RH] Please inform us when Duarte gets his rebuttal through peer review and we can discuss it at that time.

  29. TheRobin @728, I have addressed Duarte's criticism elsewhere.  The upshot is that even if we allowed his criticisms as being entirely valid, and removed from the study all papers to which it applies, it would only reduce the consensus to 96.8%.  That reduction ignores that several of the papers on Duarte's list were classified as 4, and therefore did not contribute to the consensus value; and that no doubt there were opposite errors were papers supporting the consensus were excluded or classified as 4 (both of which are known to have been the case).  Ergo the 96.8% represents a generous overestimate of the impact of taking Duarte's criticism into account.

    It is astonishing how consistently critics of Cook et al (2013) fail to estimate the impacts of their criticism on the 97%; and how consistently the impacts are negligible at best.  There is a reasons why Duarte's criticism will not make it into peer review - but will be endlessly bandied around by those for whom rhetoric is more important than analysis.

  30. TheRobin @ 728, my viewpoint is much more the layman's , compared with Tom Curtis's more scientific assessment.

    I had a look through some of Duarte's blogging output, about a year ago.  That guy has a very weird way of viewing the world [to put it politely] . . . and my recommendation is that you will be wasting your time reading his ideas.   Life is too short, to make it worthwhile spending time sifting through such quasi-sapient ramblings.  Duarte is clearly intelligent, but his ratiocination is rather disconnected from reality.


    [PS] Eclectic - please refresh your memory of the Comments Policy. In particular, note the "no ad hom, no inflammatory tone, no accusations of fraud". Recent comments have pushed or been over the line.

  31. I just had a quick question. I know that all but two scientific bodies with national or international standing have endorsed anthropogenic climate change. The two that have not take no official position. I was just wondering exactly how many scientific organizations have national or international standing. Is it hundreds of organizations or scores of organizations?

  32. Wikipedia has a pretty up to date listing of scientific organizations and their position on the climate here. They show four non-commital groups (all geologists, for some reason), with none expressing a group opinion contrary to the current consensus. 

  33. Thanks KR. I knew about the Wikipedia page, but I was hoping someone had already done the counting. Here is the simplified list from Wikipedia of scientific organizations that have endorsed anthropogenic climate change. I hope someone will let me know if I missed any or counted some twice.

    1. Inter Academy Council

    2. International Council of Academics of Engineering and Technological Sciences.

    3. National Science Academy of Australia

    4. National Science Academy of Belgium.

    5. National Science Academy of Brazil.

    6. National Science Academy of Canada

    7. National Science Academy of the Caribbean.

    8. National Science Academy of China.

    9. National Science Academy of France.

    10. National Science Academy of Germany.

    11. National Science Academy of India.

    12. National Science Academy of Indonesia.

    13. National Science Academy of Ireland.

    14. National Science Academy of Italy.

    15. National Science Academy of Malaysia.

    16. National Science Academy of New Zealand.

    17. National Science Academy of Sweden.

    18. National Science Academy of Turkey.

    19. National Science Academy of the United Kingdom.

    20. National Science Academy of Japan.

    21. National Science Academy of Russia.

    22. National Science Academy of the United States.

    23. National Science Academy of South Africa.

    24. National Science Academy of Cameroon.

    25. National Science Academy of Ghana.

    26. National Science Academy of Kenya.

    27. National Science Academy of Madagascar.

    28. National Science Academy of Nigeria.

    29. National Science Academy of Senegal.

    30. National Science Academy of Sudan.

    31. National Science Academy of Tanzania.

    32. National Science Academy of Uganda.

    33. National Science Academy of Zambia.

    34. National Science Academy of Zimbabwe.

    35. African Academy of Sciences.

    36. Polish Academy of Sciences.

    37. American Association for the Advancement of Science.

    38. Federation of Australian Scientific and Technological Societies.

    39. United States National Research Council.

    40. European Academy of Sciences and Arts.

    41. European Science Foundation.

    42. American Chemical Society.

    43. American Institute of Physics.

    44. American Physical Society.

    45. Australian Institute of Physics.

    46. European Physical Society.

    47. American Geophysical Union.

    48. American Society of Agronomy.

    49. Crop Science Society of America.

    50. Soil Science Society of America.

    51. European Federation of Geologists.

    52. European Geosciences Union.

    53. Geological Society of America

    54. Geological Society of London.

    55. International Union of Geodesy and Geophysics.

    56. National Association of Geoscience Teachers.

    57. American Meteorological Society.

    58. Australian Meteorological and Oceanographic Society.

    59. Canadian Meteorological Society.

    60. Royal Meteorological Society (UK).

    61. World Meteorological Organization.

    62. Amercian Quaternary Association.

    63. International Union for Quaternary Research.

    64. American Association of Wildlife Veterinarians.

    65. American Institute of Biological Sciences.

    66. American Society for Microbiology.

    67. Australian Coral Reef Society.

    68. Institute of Biology (UK)

    69. Society of American Foresters.

    70. The Wildlife Society.

    71. American Academy of Pediatrics.

    72. American College of Preventable Medicine.

    73. American Medical Association.

    74. American Public Health Association.

    75. Australian Medical Association.

    76. World Federation of Public Health Associations.

    77. World Health Organization.

    78. American Astronomical Society.

    79. American Statistical Association.

    80. Canadian Council of Professional Engineers.

    81. The Institution of Engineers Australia.

    82. International Association of Great Lakes Research.

    83. Institute of Professional Engineers New Zealand.

    84. The World Federation of Engineering Organizations.

    Scientific Bodies Rejecting Anthropogenic Global Warming:


    Scientific Bodies With No Official Position.

    1. American Association of Petroleum Geologists.

    2. American Institute of Professional Geologists.

    3. Candadian Federation of Earth Sciences.

    4. Geological Society of Australia.

    So, if your basketball team had a record of 84-0-4, that would be a pretty good year. If you tell me there is no consensus I would advise you to see a phychiatrist.

  34. A point about messaging to the public. In the "Consensus of Scientists" video, John Cook makes the well-reasoned point about relying on expertise. But I think the general public could reasonably still be confused by the fact that non-expert scientists aren't showing nearly as strong of a consensus based on the current surveys. Is this because the wrong question is being asked of them, at least in terms of the type of question that is relevant to the public? Should there be a different survey that asks whether they trust the findings of the climate scientists in regard to climate change? In other words, should the quesiton be posed so that non-experts are not being asked about their personal confidence based on their expertise but rather of their trust in the findings of climate scientists, who are the experts? If the question was posed in such a way, would it show a much broader support in the science community for the acceptance of climate change and the need to act? Would this clarify the messaging to the public by separating a scientist's personal expertise from their support for the relevant experts? I guess one could just point to all the scientific societies that give the same supporting message on climate change, but maybe that could still be miscontrued by the public as a "top-down" opinion being pushed by representatives rather than an accurate reflection of the opinions of individual scientists.

  35. If the body of evidence is so strong and the concensus so overwhelming, why is it that no organisation, including IPCC, will directly answer the question "what percentage of forecast global warming is due to greenhouse gas emissions". They seem happy to forecast temperature rises to a tenth of a degree over a decade, so presumably have data to segregate causes.


    Welcome to Skeptical Science. Please take the time to review the comments policy and ensure future comments are in full compliance with it.

    In particular, please note the ban on sloganeering which your comment runs dangerously close to. This means that you must back your assertions with references/data.

    Your comment seems strange because it appears that you have not in fact read what the IPCC says. It does not "forecast" as such, nor do models have any skill at decadal level prediction of surface temperature. The report most certainly does have an attribution statement on warming.

    "It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period."

    That statement is discussed in more detail here.

    You will find discussions here more productive if you do not raise strawmen arguments (ie make sure what you claim someone says is in fact true).

  36. dfern @735, here are the IPCC's AR5 attribution of recent warming (1951-2010) to various anthropogenic factors based on their figure 10.5:

    Note, OA stands for Other Anthropogenic factors, primarilly the aerosol direct and indirect effects and Land Use Change, all of which are negative forcings.  As indicated, the certainty of the total anthropogenic contribution is much greater than that for the decomposed elements.  The figure needs a slight qualification in that it does not include the uncertainty of the correctness of the models, so that the actual uncertainty is larger than that shown, but not quantifiably so.  To allow for this, the IPCC AR5 stated that at least 90% of the Probability Density Function of anthropogenic contribution (ie, the equivalent of the area under the orange line, once model uncertainty is accounted for) lies above 50%.  They used a technical short hand to say that, but that is the ghist.  Note that expanding the uncertainty will reduce the peak, and broaden the area under the curve, but ill not shift the position of the peak, so that the most probable anthropogenic contribution is 108% over that interval, and the most probable greenhouse gas contribution is 138%.

    In short, your supposition that the IPCC has not directly answered the question as to the percentage of warming contributed by anthropogenic factors, or even greenhouse gases is false.

  37. There definitely is a consensus that CO2 can increase temerature,

    BUT NOBODY KNOWS BY HOW MUCH, that part is NOT consensus. According to believers the icecaps would have been long gone by now and we would be in knee deep water in Florida.

    There is no consensus on CATASTROPHIC climate change.

    Over the past 11,000 years the Earth has had temperatures above today's average temperature about 9 times. We are now at average temp according to this data: GISP2 below


    During evolution, the CO2 was many thousands of ppm and man was definitely not around then and yet life was possible during this "catastrophic" CO2 level


    [RH] Shortened link. Please note that use of all caps is against our commenting policy.

    [TD] Your comments are most appropriate on several other threads. Please read the following, and if you want to comment further on those topics do so on those threads, not this one:

    "...the icecaps would have been long gone by now." You need to provide a reference for your claim. I'm unaware of anyone who has claimed that. For actual peer reviewed scientific projections of ice loss, type into the Search field at the top left of any page relevant terms such as ice, sea ice, land ice, and glacier, and choose from among the resulting hits. Here is one of those: Read the Intermediate tabbed pane of "How the IPCC is more likely to underestimate the climate response," scrolling down to the section on Arctic sea ice.

    "...we would be in knee deep water in Florida." You need to provide a reference for your claim. I'm unaware of anyone who has claimed that. For actual peer reviewed scientific projections of sea level rise, type "sea level" into the Search field at the top left of any page, and choose from among the resulting hits. Here is one of those: "How much will sea levels rise in the 21st Century?" After you read the Basic tabbed pane there, read the Intermediate one.

    "There is no consensus on catastrophic global warming." "Catastrophic" is too ambiguous a term; scientists' projections are much more specific. Read "Positives and negatives of global warming." After you read the Basic tabbed pane, read the Intermediate and then the Advanced.

    "Over the past 11,000 years the Earth has had temperatures above today's average temperature about 9 times. We are now at average temp according to this data: GISP2 below." The GISP2 graph you linked has as its most recent data the year 1855. Not even 1955, but 1855. So it does not show anything like "today." Also, it reflects the temperature only from a single spot in Greenland, which is not at all representative of the entire Earth. Read "Most of the last 10,000 years were warmer." To learn about temperature indices that are representative of the entire Earth, and that go up to much closer to today, read "Real skepticism about the Marcott hockey stick." Then use the Search field to look for more posts  about Marcott, and posts about PAGES 2K.

  38. Why do we analyze only a few hundred years back.

    We need to look back 11,000 years and you will see that the temperature has been much higher in the past and increased at a much faster rate in many occasions in the past. We focus to much on the recent past and its wron to base conclusions on this tiime period alone.


    [TD] This comment is redundant with your previous one. Don't do that.

  39. Hathawad:

    If you want to learn about these things, go to the "View All Arguments" at the bottom of the thermometer image on the upper left of each page (below "Most Used Cliamte Myths"). You wll find nearly 200 links to various myths, of which your brief posts have covered a surprisingly large number for so few words.

    Your assertions are completely unsupported, and that counts for nothing at this site.

    ...and read the comments policy (link just above the box you type your comment in)

  40. Hathawad @737:

    1)      "There definitely is a consensus that CO2 can increase temperature, but nobody knows by how much"

    IPCC AR5:

    "The equilibrium climate sensitivity quantifies the response of the climate system to constant radiative forcing on multicentury time scales. It is defined as the change in global mean surface temperature at equilibrium that is caused by a doubling of the atmospheric CO2 concentration. Equilibrium climate sensitivity is likely [probability of 66% or more] in the range 1.5°C to 4.5°C [0.41- 1.22 C/(W/m^2))](high confidence), extremely unlikely [probability of 5% or less] less than 1°C [0.27 C/(W/m^2))] (high confidence), and very unlikely [probability of 10% or less] greater than 6°C [1.6 C/(W/m^2))] (medium confidence)."

    That is very simple to interpret.  If your assessment of the Probability Density Function (PDF) of the Equilibrium Climate Sensitivity (ECS) shows a probability that the ECS lies between 1.5 and 4.5 C less than 66%, you are in disagreement with the IPCC, and your assessment lies outside of the consensus.  If your assessment is that the probability that the ECS is less than 1 C is greater than 5%, you are in disagreement with the IPCC, and your assessment lies outside of the consensus.  If your assessment is that the probability that the ECS lies above 6 C is greater then you are in disagreement with the IPCC, and your assessment lies outside of the consensus.  As a result it is clear that Nick Stokes estimates of the ECS, though low, are clearly within the consensus while those of deniers claiming an ECS of 1 C or less are not.

    I included in the quote from the IPCC the values interpreted as a Climate Sensitivity Factor, which allows you to simply multiply out a forcing to see the temperature response to that forcing.  Thus, at doubled CO2 the forcing is 3.7 W/m^2 +/- 10%.  From the forcing and the Climate Sensitivity Factor, the temperature impact of CO2 at equilibrium is easilly calculated.  In short, the temperature impact of CO2 is known within a significantly constrained range that excludes most denier estimates of the impact.

    2)    "According to believers the icecaps would have been long gone by now..."

    No climate scientist of any repute has claimed that the ice caps (ie, kilometers deep layers of ice covering Antarctica and Greenland, and some thinner ones on islands in the Canadian Archipelago) would have melted by now, or even by the end of the century.    Wieslaw Maslowski and Peter Wadhams has predicted an early loss of Arctic sea ice (ie, the very thin ice floating on the sea surface) around this decade.  The low bracket of their estimate has come and gone.  The central value of his estimate falls in the remaining four years of this decade, and are widely considered by sea ice experts to be utterly implausible.  The actual consensus position, as given in the IPCC AR5 is:

    "Based on the CMIP5 multi-model ensemble, projections of average reductions in Arctic sea ice extent for 2081–2100 compared to 1986–2005 range from 8% for RCP2.6 to 34% for RCP8.5 in February and from 43% for RCP2.6 to 94% for RCP8.5 in September (medium confidence).  A nearly ice-free Arctic Ocean (sea ice extent less than 1 × 106 km2 for at least 5 consecutive years) in September before mid-century is likely under RCP8.5 (medium confidence), based on an assessment of a subset of models that most closely reproduce the climatological mean state and 1979–2012 trend of the Arctic sea ice cover. Some climate projections exhibit 5- to 10-year periods of sharp summer Arctic sea ice decline—even steeper than observed over the last decade—and it is likely that such instances of rapid ice loss will occur in the future. There is little evidence in global climate models of a tipping point (or critical threshold) in the transition from a perennially ice-covered to a seasonally ice-free Arctic Ocean beyond which further sea ice loss is unstoppable and irreversible."

    (My emphasis)

    (See the upper right panel in particular.)

    So, the consensus position is for a sea ice free Arctic around mid century, approximately 30 years from now, and that being avoidable if we mitigate climate change.

    3)   "...and we would be in knee deep water in Florida".

    The IPCC AR5 predicts a likely range for sea level rice in 2081-2100 of 0.52 to 0.98 meters (ie, enough to make you shin to knee deep if you stand at the current water level) assuming RCP 8.5 (essentially business as usual.  Predictions of knee deep sea level now except as a result of storm surge are figments of your own imagination.

    4)   "Over the past 11,000 years..."

    GISP 2 represents a temperature proxy for only one location on the earths surface, and consequently does not represent Global Mean Surface Temperature (GMST).  You should at the minimum use a mean of several long term temperature proxies, such as this one from Global Warming Art:

    The recent decadal average is up around 1 C on this scale, and well above the 2004 value indicated in the graph, and hence above the mean across all decades.  These proxies do not have a annual time scale so some decades in the past 10,000 years may have been warmer than our current decade - but we do not know that any were and it is likely that very few were.  Further, the temperature rise since 1850 is almost certainly unprecedented since the end of the last glacial.

    5)  "During evolution, the CO2 was many thousands of ppm and man was definitely not around then and yet life was possible during this "catastrophic" CO2 level"

    Durring those periods with very high CO2 levels, solar activity was significantly less than it is today.  This is known because solar activity increases overtime in a very predictable pattern.  The result is that combined forcing of CO2 plus solar was not much greater than preindustrial levels, and less than likely levels of forcing with Business As Usual:

    It is interesting to note that up to 65 million years ago, land life was dominated by ectotherms and endotherms, ie, creatures much less vulnerable to heat stress than is the case for humans.  Periods of elevated temperatures in the last 65 million years have also see a dominance of smaller animals, with a higher surface to volume ratio and higher basal temperatures (both contributing to more efficient cooling).  Neither of these facts is comforting to large, homeothermic animals such as humans when facing similarly elevated temperatures.  Rodents, snakes and cockroaches, on the other hand, will do just fine.

    In summary, your "points" rely mostly on misrepresenting the claims of climate scientists, or misrepresenting what is actually known.  An argument that can only be pressed by such means (as is the case with nearly all denier arguments) are not worth pursuing, or indeed, giving any credence to. 

    If you surprise me by actually responding, please do so on the appropriate threads as indicated by the moderator.


    [JH] To make it easier for readers to disgest your posts, I suggest that you use italics font for the material you are quoting from the commenter you are responding to.  In this particular case, you may also want to put the quotes in bold-face because they essential serve as subject headers. 

  41. Hi,

    I have a question regarding the famous Cook et al. (2013) paper on scientific consensus regarding AGW, and critical responses to this paper, especially the one by Legates et al. (2015). The only response to this paper by Legates et al. that I could find was included in the '24 errors of Tol' (page 6). In their paper, Legates et al. claim that Cook et al. misrepresent the consensus since only a small minority of papers actually say that 'human activity is very likely causing most of the current GW'. The two biggest categories of papers accepting the AGW hypothesis are either of the implicit or explicit  but unquantified variety. In response to the critique, Cook et al. argue that it is an impossible expectation to expect authors to explicitly quantify the extent of global warming. I do not think that this is what Legates et al. are expecting though - they are only expecting papers to say that they are 'causing most of the current GW', which is the definition made by Cook et al. at the outset of the paper. So in so far as I'm reading the original Cook et al. paper correctly, i.e. they are querying what percentage of papers agrees with the definition of the AGW hypothesis Cook et al. establish in their paper, namely "human activity is verly likely causing most of the current GW", it appears to me that Legates et al. are correct in arguin that Cook et al. cannot show that 97% of the papers that express an opinion do express this strong of an opinion.

    I think Legates et al. do have a point in the sense that there is a clear difference between a paper saying that humans are contributing to climate change (this being the example statement in the Cook et al. paper for their category 2) and a paper saying that humans are the primary cause of climate change. 'Humans are contributing to climate change' is something that, as far as I am aware of the denialist literature, even most denialists would agree with - they would just say that the human contribution is minimal.

    Thanks in advance for any clarification on this matter!

  42. Spassapparat @741, Legates et al do not have a good point, because they apply it selectively.  We may well be interested in a comparison between the number of papers that "explicitly endorse with quantification" (65) and those that "explicitly reject with quantification" (10) which means an 86.67% endorsement rate among papers whose abstracts explicitly endorse or reject AGW, not the 0.03% used by Legates et al.  (Indeed, Legates figure is doubly wrong because 0.3% of 11,944 abstracts is 36, not the actual 65 explicit endorsements as can be determined by a simple search of the abstracts.)  We might be more interested in the 52 author rated "explicit endorse with quantification" and 9 author rated "explicit reject with quantification" (85.25% endorsement rate).  We may also be interested in the 10 rated "explicit endorse with quantification" and 0 rated "explicit reject with quantification" (100% endorsement rate) from among those abstracts that which include the term "attribute" or its cognates in the title.  We also may be interested to know that among those abstracts that include "attribute" or its cognates, the quantities in each endorsement category are:

    1: 10



    4: 366

    5: 5



    for a total endorsement rate of 97.09% among those that state a position in the abstract.

    The point is that it is not true that only those papers whose abstracts explicitly endorse with quantification actually endorse AGW.  Therefore if you are going to restrict discussion to just those abstracts with numerical attribution values, you need to compare them with just those abstracts - not the total of abstracts which have been excluded from consideration on a technicality.  Not including a specific quantification may simply occur because the quantification has been reserved for the conclusion rather than being revealed in the abstract (a common trait in scientific papers), or because the paper was not explicitly about attribution so that a more general statement was sufficient.  Pretending that is not the case to make rhetorical points is not good science.  It is pseudoscience.

  43. Mr. Curtis,

    thanks so much for your quick reply! I agree with everything you have written, and I do think that Legates et al.'s 0,03 number is completely bogus.

    What I did agree with Legates et al. is that Cook et al's wording is at least unfortunate. In my opinion, if, as is Cook et al's outset question, you want to figure out the number of papers who accept the hypothesis that 'human activity is responsible for most of current GW'  you cannot include papers that write that 'human activity is contributing to current GW' as part of the total number of papers that agree with 'human activity is responsible for most of current GW. Now the word 'attribute' is a different ballpark, since if I write 'current GW is attributed to human activity' then I actually mean, in contrast to 'contribute', that most (or all) of current GW is due to human activity. (or at least, this is my understanding, I am not a native speaker of English)


    I do believe that words matter. In my view, then, papers that use the word 'attribute' or similar should have been separated from papers that use 'contribute', 'play a part/role', 'add to', etc. If this is what is done in the analysis you posted, then this shows that Cook et al's analysis is robust to Legates et al's critique.


    I have another question: something that is also critiqued in Legates et al. as well as other critical papers is the issue of the search term used - they claim that the search term 'global warming' or 'global climate change' biases against critical research since at least some critical research does not use these terms - do you give any credence to the view that this is a significant bias?

    Thanks again!

  44. I have now dabbled with the search tool you posted a bit and looked up papers whose abstracts include 'attribute'. Just on the first page, I found several papers that use the word attribute, but in association with someting other than climate change attributed to human impact. Did your analysis of the word attribute and its cognates only include such papers that used the word attribute and its cognates specifically for this purpose?


    Also, I was wondering about what the paper is actually saying. If we include category 2 and 3, don't we have to dial down what we are saying to what is included in the weakest category (category 3), i.e. all we can say is 97% of papers agree that humans are causing global warming to some extent. That is decidedly not how this paper is used in public discourse though, I think in many instances this paper is used to say that not only do humans cause global warming, but they are also the major cause and the degree of effect on nature/climate is in some way dangerous and needs to be mitigated. This only is true for a minority of the papers though. Would you agree with this assessment?


  45. Spassapparat @744 & prior :

    two points for your consideration, are (A) the design of the Cook-2013 study included a second part where the scientific paper authors were surveyed to discover their assessments of their own papers, regarding attribution ... and this second part confirmed the accuracy of the first part

    and (B) the average "age" of the papers equalled approx. 2005 ... so 10 years or more ago.   Reading the Cook et al. study shows that later papers were more "attributive" than earlier papers.   This result is exactly what one would expect, in view of scientific research subsequent to 2005 all indicating the high [ approx. 100% ] attribution to human-causation of global warming.  (See the latest IPCC summaries)

    Additionally, if you look around the world today, you find almost no genuine climate scientists who attempt to support a contrary [ =non-human ] attribution for the present & continuing rapid warming.

    We can enjoy having Spass with words & rhetoric, but it is our duty to look at the Realitaet — the physical reality of atoms & energies which underlie the words.  That reality is experiencing major warming, and the causation is scientifically very clear and obvious.

  46. Eclectic @745 , thanks for your response!

    Since the chair of the science committee in today's hearing on climate change brought the papers critiquing the Cook et al study into public record, this brought me back here.

    I am aware of (A), but one should note that even there we still do not get close to a 97% consensus on category (1). I've looked into the data, and it suggests that 17% of the authors of papers that do express an opinion on climate change self-identify their paper as a category 1 paper. This is substantially higher than the rating by Cook et al. themselves, but still a farcry from the 97%.

    If Cook et al. are now saying that many papers do not make a definite statement because it is obvious that most of global warming is human-made, I am inclined to agree with this assumption, not least because of other research referenced on this page showing a similar degree of consensus. However it is still just that, an assumption.

    I do not think it is just Spass to play with words, I do think there is a substantial difference between saying "Cook et al. show that there is a 97% consensus that most of global warming is human made" (which, in my opinion, is an untrue statement) and "Cook et al. show there is a 97% consensus that some global warming is human made".

    I wonder why, since there are half a dozen other studies showing a similar agreement, this site in particular and the climate science  community in public discourse in general chooses to use a study whose proclaimed findings are so easily attackable.

  47. Spassapparat @746, in Cook et al, endorsement or rejection is explicitly stated to be endorsement or rejection of the theory of AGW.  That is, it is endorsement or rejection of a specific theory which states, in part, that anthropogenic factors are responsible for greater than 50% of warming since 1950.  If you interpret the different categories of endorsement (implicit, explicit, and explicit with quantification) as applying to successively stronger theories, you have misinterpreted the paper and misunderstood the methodology in the paper.

    You say (@744):

    "Also, I was wondering about what the paper is actually saying. If we include category 2 and 3, don't we have to dial down what we are saying to what is included in the weakest category (category 3)"

    However, category 3 is not endorsement of a weaker theory, but a less strong endorsement of the same theory.  In category 1, endorsement is explicit, and a quantification is give so there can be no doubt that AGW is endorsed.  In category 3, endorsement is implicit, so while the theory endorsed is the same, the possibility of error in assessing whether or not the paper endorses the theory is greater.

    I am aware that climate "skeptics" reject this understanding of the paper, but it was the understanding of the authors, and it was the understanding of the raters.  More importantly, if the endorsements are not understood in that way, it makes the paper inconsistent.  That means critics are rejecting a consistent understanding of the paper, which was held by the authors and raters, in order that a criticism they have should be valid.  Another way of putting that is that they are raising a straw man.

  48. Spassapparat @746 ,

    the purpose of science is to discover the truths of our universe.

    And the purpose of surveys such as Cook et al., 2013 , is to discover the truth about what scientists hold to be factual.

    Of course, we should also look for further evidence that may corroborate what the surveys do find (they find that, for expert climate scientists, a percentage figure in the high 90's is holding AGW theory to be factual).

    These survey results are (unsurprisingly) supported by word-of-mouth opinion from expert scientists about their colleagues — and Spassapparat, this is a matter which you can rather easily ascertain for yourself, by questioning some genuine climate-related scientists.  I am confident you will find it difficult, indeed almost impossible, to find any genuine "contrarian" scientist.  And any such, that you can find, will be unable to provide any real evidence to support their contrarian viewpoints.

    For the year 2013, it is reported that over 2000 climate-related scientific papers were published (totalling 9000 authors).  And yet in that period, only one paper made a contrarian claim [i.e. that modern global warming is caused by an alteration of cosmic ray bombardment of the atmosphere].  This single paper was by a Russian astronomer, and was published in a Russian journal of proceedings.  The paper was vaguely-worded; it did not measure the claimed effect; and it failed to dispose of the well-measured and well-understood CO2 mechanism known to produce AGW.  This cosmic ray hypothesis had already been debunked before 2013 : and in addition, since 2013 there has been more evidence (from cloud-chamber experiments by CERN scientists) showing that this cosmic ray hypothesis is false.  In short, the Russian paper was Dreck.

    So in reality, Null out of 2000 papers could support a non-AGW position.  To me this seems excellent corroboration that the "over 97%" Cook et al. study is the correct representation of the truth — and that the Cook 97% figure very much understates the current status.

    In seeking truth, it is our duty to use complete Ehrlichkeit, and to avoid word-games which are unsupported by the general evidence, and to avoid unredlich conclusions (even when these unredlich conclusions are politically fashionable in some quarters).

  49. This page needs to be updated because denialists are using a new strategy: rather than deny the consensus itself, they deny what the consensus view is. One guy that I debated at length repeatedly ignored the words "most" and "mostly" present in many of the survey questions, instead summarizing the survey questions as asking whether warming is affected by humans "at all" so that scientists' views would not be in conflict with his (he and the 3 followers 'liking' all his posts ignored me as I repeatedly pointed out the ridiculousness of claiming "most" = "any at all".)

    Also, this page should give the EXACT wording of each survey question and the percentage of publishing climate scientists in agreement. According to the "consensus on consensus" paper, for instance, I noticed that 88% of members of the AMS surveyed whose area of expertise was climate science, agreed in 2014 that half or more of the warming was caused by human activities, including 78% who agreed that “the cause of global warming over the past 150 years was mostly human”. “An additional 6% answered ‘I do not believe we know enough to determine the degree of human causation.’” (Stenhouse 2014)

    Notice the window on this question: 150 years. Now, it’s clear the numbers on this very web site that humans caused substantially less than half of global warming in the early 20th century and before. Why, then, do 88% of American climate scientists still agree, despite this, that the roughly 1°C of global warming over the last 150 years was half-or-more human-caused? The obvious answer: although the human contribution was below half before 1940, it was far more than half in the last 50–65 years. So on average, in aggregate, humans are responsible for 50% or more, and much more than that if we limit the window to 50–65 years.

    Smart climate deniers may ignore this reasoning and focus on numbers like 78%, saying 22% disagreed and that's not a consensus. (The one I spoke with will simply change the subject and dazzle you with his encyclopedic knowledge of contrarian claims, never admitting that he holds a minority opinion or disagrees with scientists.) Yet if the question had asked about the most recent 50-65 years instead of 150 years, the consensus might have been 97%.

    We can't stop denialists from twisting words around, but if the survey questions and methodology are not easily discoverable to the public then it is harder to counter their claims.

  50. Oh, and specifically it's no longer useful to cite Doran 2009 which asked if "human activity is a significant contributing factor in changing mean global temperatures". Denialists will interpret "significant" as "anything above zero" and claim to be "in" the 97%. Instead be sure to quote one of the other 97% surveys that uses the word "most" or "mostly".

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