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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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The 97% consensus on global warming

What the science says...

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97% of climate experts agree humans are causing global warming.

Climate Myth...

There is no consensus

The Petition Project features over 31,000 scientists signing the petition stating "There is no convincing scientific evidence that human release of carbon dioxide will, in the forseeable future, cause catastrophic heating of the Earth's atmosphere ...". (Petition Project)

Science achieves a consensus when scientists stop arguing.  When a question is first asked – like ‘what would happen if we put a load more CO2 in the atmosphere?’ – there may be many hypotheses about cause and effect. Over a period of time, each idea is tested and retested – the processes of the scientific method – because all scientists know that reputation and kudos go to those who find the right answer (and everyone else becomes an irrelevant footnote in the history of science).  Nearly all hypotheses will fall by the wayside during this testing period, because only one is going to answer the question properly, without leaving all kinds of odd dangling bits that don’t quite add up. Bad theories are usually rather untidy.

But the testing period must come to an end. Gradually, the focus of investigation narrows down to those avenues that continue to make sense, that still add up, and quite often a good theory will reveal additional answers, or make powerful predictions, that add substance to the theory.

So a consensus in science is different from a political one. There is no vote. Scientists just give up arguing because the sheer weight of consistent evidence is too compelling, the tide too strong to swim against any longer. Scientists change their minds on the basis of the evidence, and a consensus emerges over time. Not only do scientists stop arguing, they also start relying on each other's work. All science depends on that which precedes it, and when one scientist builds on the work of another, he acknowledges the work of others through citations. The work that forms the foundation of climate change science is cited with great frequency by many other scientists, demonstrating that the theory is widely accepted - and relied upon.

In the scientific field of climate studies – which is informed by many different disciplines – the consensus is demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them.

Authors of seven climate consensus studies — including Naomi OreskesPeter DoranWilliam AndereggBart VerheggenEd MaibachJ. Stuart Carlton, and John Cook — co-authored a paper that should settle this question once and for all. The two key conclusions from the paper are:

1) Depending on exactly how you measure the expert consensus, it’s somewhere between 90% and 100% that agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists.

2) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming.

consensus studies

Expert consensus results on the question of human-caused global warming among the previous studies published by the co-authors of Cook et al. (2016). Illustration: John Cook.  Available on the SkS Graphics page

consensus vs expertise

Scientific consensus on human-caused global warming as compared to the expertise of the surveyed sample. There’s a strong correlation between consensus and climate science expertise. Illustration: John Cook. Available on the SkS Graphics page

Expert consensus is a powerful thing. People know we don’t have the time or capacity to learn about everything, and so we frequently defer to the conclusions of experts. It’s why we visit doctors when we’re ill. The same is true of climate change: most people defer to the expert consensus of climate scientists. Crucially, as we note in our paper:

Public perception of the scientific consensus has been found to be a gateway belief, affecting other climate beliefs and attitudes including policy support.

That’s why those who oppose taking action to curb climate change have engaged in a misinformation campaign to deny the existence of the expert consensus. They’ve been largely successful, as the public badly underestimate the expert consensus, in what we call the “consensus gap.” Only 16% of Americans realize that the consensus is above 90%.

Lead author John Cook explaining the team’s 2016 consensus paper.


Last updated on 8 May 2016 by BaerbelW. View Archives

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Further reading

Richard Black at the BBC investigates whether there is a bias against skepticism in the scientific community.

More on what we're talking about when we say "scientific consensus,"  in an essay founded on Denial101x and scientific literature: Scientific Consensus isn’t a “Part” of the Scientific Method: it’s a Consequence of it. (or via

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 901 to 908 out of 908:

  1. Star-affinity @ #900 :

    Thank you for the reference to the 2016 Forbes  article by Earl Ritchie, who describes himself as a retired oil industry executive (not a scientist).   I read the article with interest, and found it disappointing.  It was more a propaganda piece, and not at all a rigorous logical examination of the issue.

    Star-affinity, if one chooses to define things very loosely, and also use rhetoric like a lawyer-advocate  ~ then one can come to any "conclusion" that is desired.   (e.g. the good Lord Monckton - not at all a scientist - can re-define "3%" to be the result of the excellently clever Cook 2013 survey of scientific papers which produced the famous "97%" consensus figure.)

    What is a consensus here?  (See some of the comments upthread.)   Broadly, consensus in non-scientific matters is all about opinion  ~ and opinion is worth the price of the paper it is printed on [except in politics!]

    But consensus in scientific matters (such as climate science) is all about the evidence.  And that evidence is expressed in the scientific literature (peer-reviewed papers published in reputable journals).   And there you will nowadays  find a 99+% consensus in line with the mainstream science.   Not an 80-90% consensus (not even in 2013 or 2016).

    The 80-90% figure you (or Mr Richie) are mentioning, is a result of canvassing opinions of "scientists"  ~ not of canvassing the evidence.   And who is a scientist?  And are their individual opinions relevant?  The notorious Oregon Petition (of the 1990's) had "scientists" ranging from Wood Engineers to Spice Girls.   In other words, it was a completely worthless survey,  simply gathered for propaganda value.

    In short, Mr Ritchie's article is worthless.

  2. Star-affinity @#900:

    Several other studies have looked at the scientific consensus on human-caused climate change since that Forbes article was published. Here is a blog post from last year written by John Cook about a study he was involved with, replicating Doran & Zimmermann (2009) with a larger sample:

    The scientific consensus on climate change gets even stronger

    The interesting thing with the Forbes' article is, that it has to cherry pick a particular study to make its point of a lower than 90% consensus. And expecting 100% agreement of climate scientists before accepting the evidence is a case of impossible expectations, one of the main science denial techniques covered in the FLICC framework.

  3. BaerbelW  @  #902  :  We can look even further, regarding the Forbes 2016 article mentioned by Star-affinity @ #900 .

    The article's author, Mr Earl Ritchie, has grossly misrepresented the vonStorch 2013 survey  ~ the survey simply does not support Ritchie's thrust of argument.   Ritchie is severely misleading the Forbes  readers - readers who are probably good at business but probably rather unthinking (and ill-informed) on science.   And Ritchie is also misleading them about the Cook 2013 survey of scientific papers.

    The vonStorch 2013 survey [now 8 years old] had its interesting points.  And I think the brief "Mertonian" discussion on pages 68 & 69 was a pleasant change of pace.   And at the end of the survey report, Bray & vonStorch published a long list of comments criticizing the deficiencies of the survey (participants' critiques ~ especiallly about the ambiguities of the survey questions).

    Additionally, please note that the survey had a 7% return rate.  (Vastly different from the Cook 2013 survey, which had a different structure.)

    And, the survey was about opinions ~ and much of it was about opinions on technical aspects/adequacies of climate models & future projections.

    Most of the questions were rather vague and fuzzy and "word based" instead of scientific concept based.  So, somewhat difficult for the participants to express themselves about the overall climate science situation  ~ in analogy: they were invited to give opinion about a leaf or two, but not to discuss the background forest.

    (There were a few exceptions in the questions:  one where 2.5%  of respondents opined that they were not at all convinced about AGW.   And another question, where 89% of respondents said they were now more convinced [versus in 2007] that greenhouse gasses had produced modern global warming.)

    All this compares very poorly with the excellent methodology used in the Cook 2013 assessment of scientific consensus.

  4. Regarding the utility of surveys such as the Oregon Petition mentioned by Eclectic, I always think of Project Steve, which the National Center for Science Education uses to track opinions on the scientific validity of evolution theory. (Wikipedia also has a page on the project.)

    The question basically comes down to whether the selection of individuals responding to the survey is reasonable or not.

  5. Thank you, Bob, for showing the ingenious Project Steve.

    The vonStorch survey [referred to, above] may not have many Steves, but it is a good survey - in the sense that it has a suitable first filter.  It contacts many thousands of appropriately qualified scientists.

    Unfortunately, the low 7% return rate is the first weakness.  It would have been better (but at much greater expense) for expert interviewers to personally meet with a truly random selection of perhaps 200 of the scientists . . . and gently hound them for their views, allowing no-one to drop out or excuse himself!

    At 7% return , there is the reasonable fear that the respondents include a relatively high proportion of "extremists" (from either end of the spectrum).   For example, in one of the questions, 2.5% of respondents replied that they were "not at all"  convinced that AGW existed.   And this 2.5% is an amazingly high percentage, in view of the accumulated overwhelming evidence that the 2.5 percenters are flat wrong.

    In such extreme cases, one suspects that a big slice of the 2.5 percenters have bizarre/extremist political views & a lot of cognitive dissonance.  But 'twas ever thus ~ for almost any field of science.  (Personal anecdote - I know quite well a PhD-level scientific researcher who is a member of his local Flat-Earth Society.)

    And the vonStorch survey questions were very unsuited to elicit actual consensus-relevant opinions.

    Overall, John Cook's 2013 survey of the true scientific literature was the optimum approach to the "consensus" issue.  It was reasonably neutral in selection; it didn't suffer from drop-outs (drop-outs by the busy, or by the disgruntled) . . . and it looked at the actual science , not the sometimes-flaky opinions of us imperfect human beings.

    And on top of it, the Cook 2013 survey doubled-down by asking the scientists personally to confirm (or not) what they viewed their scientific papers as saying.   Brilliant !

  6. In response to Star-affinity @#900:

    Comprehensive responses to the question about the magnitude of consensus regarding human induced global warming and resulting climate changes have been provided by others.

    My initial supplement is: Rather than debating the magnitude of consensus for the theory that “significant anthropogenic climate change is occurring” ask for an evaluation of the level of consensus for the theory that “No anthropogenic climate change impacts are occurring”.

    Increased atmospheric CO2 is unquestionably due to human activity. And increased CO2, along with other human impacts, unquestionably produce global warming and significant, hard to precisely identify, but unquestionably harmful climate changes from the conditions that human civilization developed in through the past several thousand years.

    However, there is more to consider. It is important to be aligned on the context/objectives for a 'debate'. Without objective alignment the result can be a waste of time.

    My primary objective is to try to help develop a sustainable improving future for humanity. Increased awareness and improved understanding of what is going on is essential to sustainable improvement of the future of humanity. And increased awareness of what is harmful and learning how to limit harm done is key, with climate change impacts of human activity being a significant sub-set of concern.

    Science questions things with the objective of increasing awareness and improving the understanding of what is really going on in a way that develops “improved common sense”. It is important for that “common sense” to help improve the future of humanity.

    Note that not all science or application of science is helpful. Misleading marketing is a good example of harmful scientific investigation and application. It can develop cult-like groups of believers with nonsense as “their common sense”.

    Every individual’s perception of what is going on is their reality. All understandings of what is going on are individual beliefs. And everyone has biases regarding what they learn. Everyone develops their understanding based on their experiences in the socioeconomic-political environment they grow up in. In many cases people develop a fondness for, or addiction to, harmful unsustainable developments (systems and beliefs) and resist correction of harm done that they benefit from or hope to benefit from.

    Getting alignment on the objective of “reducing harm done to the future of humanity and developing lasting improvements for humanity” is essential. Without that alignment the discussion can be a competition with the different sides having different sets of rules about how the game is played or judged/refereed. That can be a waste of time.

    Debating details about the level of consensus of understanding that human activity is causing harmful rapid climate change impacts is one of those waste of time games. Establishing that there is significant consensus is important. However, questioning a well developed understanding of the level of consensus is a game being played to delay and distract from the important discussions of how to identify and most effectively limit the harmful impacts of the many developed unsustainable activities that cause climate change impacts.

    One of the most harmful activities is misleading marketing. Always keep in mind that popularity and profitability have no reason to be aligned with limiting harm done. They are measures that are indifferent to harm done . Being more popular or profitable does not mean something is less harmful. In fact, getting away with being more harmful or misleading can be a competitive advantage in games of popularity and profit. And being more popular and profitable can make harmful beliefs and actions harder to correct (the persistence of climate science denial is one of many cases proving that point).

  7. Dr. David Evans made the statement: "Yes, it's important to get our response right. If the alarmist is correct, then we should cut down our carbon emissions of the planet from overheating. If the alarmist is wrong, it's important not to cut back our carbon emissions or we'll create widespread poverty unnecessary.

  8. Sun:

    There is a lot in between the two extremes of "catasrophe" and "no need to do anything". It is not a binary system or "right or wrong" - it is a range of likely outcomes and risks.

    We know with pretty much 100% certainty that adding CO2 causes some warming. For doubling of CO2 (from 300 to 600ppm) it is very unlikely that it will be less than 1.5-2.0C. It will also be very unlikely that it will be more than 4.5-5.0C. But that leaves a lot of range of likely temperature effects that will cause serious changes in climate and very likely serious (and expensive) impacts on society. The larger the temperature change and the impact, the more important it is that we take additional action.

    The idea that CO2 limits will harm the economy is discussed in this thread at Skeptical Science.

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