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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 201 to 225 out of 802:

  1. Tom, I dismiss all skeptic work, as does anyone who understands how science works. What an irony that you are worried about people being sceptic but in the same time defend someone whose ideas neglect the validity of science in general.
  2. In the section "Scientific Oranisations Endorsing the Consensus", there is a broken link. I believe the link (NASA's Goddard Institute of Space Studies) should be
    Response: Thanks for the link. However, upon reflection, I've removed that link - it's not so much an official statement by the GISS organisation as the opinion of James Hansen, a GISS employee. I'm not sure if NASA or GISS have published an official statement on climate change.
  3. "Consensus" has little meaning in science. Ground-breaking science is by definition outside the prevailing consensus. Consensus just means it is easier to publish your work. Prions were hotly disputed, and the idea of an infectious protein is about as jaw-dropping as it gets, but subsequently Stanley Prusiner won the Nobel prize for his research. Science simply consists of explaining the most data with the least long-winded explanation (aka Occam's Razor). We use the model that the earth orbits the sun because the math becomes neat and tidy using this assumption. With the earth at the center, the math becomes intractable very quickly. However, when discussing hurricanes and naval guns, folks like to assume the earth does NOT rotate, and a fictitious force called the Coriolis force must be introduced to correct. We assume the earth is flat for laying out a garden, but need a spherical model to use for space travel. Physics uses the wave theory of light in optics, and organic chemists use stick and ball models, knowing they are incorrect, but convenient, models. Everyone clear on what science is now? The Asch conformity experiments in psychology show people will knowingly lie to conform when comparing lines on a piece of paper. No ambiguity. Other experiments show the less people know about a topic, the more they conform. What happens when you have an enormously complex chaotic non-linear system (aka climate) whose inputs and outputs are not well understood, and conclusions are presented as unequivocable? The bottom line is that climate science is a bit flakey from the get-go, the data have enormous variance, and the field is not helped by over the top WAG predictions a hundred years out. The only reason it appears to have any traction, is because mankind can be blamed. There are far worse end-of-the-world-as-we-know-it scenarios with much better data, approaching almost certainty, that would merit more time and resources. Any questions?
  4. oracle2world, Nobel prizes are awarded only after a consensus is reached and Stanley Prusiner had to wait 15 years. Contrary to popular belief, this is how science works, a ground-breaking theory on something not yet explained emerges but it needs to convince the other scientists before it is accepted and form a new consensus. In real science there's no definitive proof but a (growing) amount of evidence.
  5. you do realize that there cannot be skeptics if you are talking about a theory. climate change is a theory so how can there be skiptics
  6. Here is an endorsement from the AMA. Glad to know this counts as important, even if off the beaten track of the AMA's expertise. In other words, professional society endorsements are about as useful as a professional ball player's endorsement of a particular brand of chewing gum. American Medical Association In 2008, the American Medical Association issued a policy statement on global climate change declaring that they: Support the findings of the latest Intergovernmental Panel on Climate Change report, which states that the Earth is undergoing adverse global climate change and that these changes will negatively affect public health. --
  7. Dear Riccardo My point was that science is not "consensus". Science is Occam's Razor. The least long-winded explanation of a dataset is the current model. Folks in the scientific world who are chicken to speak out, is not "consensus". Stomach ulcers were thought to be caused by emotional distress, the consensus belief. Based on a plausible theory, with no one bothering to be skeptical about it. In 1982 a physician Barry Marshall proposed that a previously unidentified bacterium Helicobacter pylori was the cause. It fit the data better, which led to new treatment, that made some drug companies VERY unhappy. Folks back then thought Marshall was completely off his rocker to challenge "the consensus". Exactly like AGW skeptics today are thought to be unhinged. Actually the only question in the whole of AGW, is whether anthropogenic CO2 emissions account for temperature data better than the random variances inherent in climate. Right now, they don't.
  8. Oracle2world, what Riccardo stated in his post is essentially correct. Science is not Occam's Razor or parsimony or whatever you want to call it. People may use such approaches in the method of discovery but the model has to explain the evidence. Watch this video, and see what consensus in science actually means. Note to John: Perhaps you could link directly to Naomi Oreskes talk here or when talking about her survey here Of course I would obviously recommend you screen the talk and its suitability yourself first :P
    Response: Thanks for the suggestion - I've added Naomi Oreskes' latest talk to What does Naomi Oreskes' study on consensus show?
  9. I've got yet another statement by a scientific organisation that you might like to add to your list. Recently in Australia, the CSIRO and the Australian Bureau of Meteorology released a joint statement on climate change .
    Response: Thanks for pointing this out. I actually read the CSIRO/BoM report earlier this week (an excellent read, particularly for Australians) but it never occured to me until reading your comment to add this to the list of scientific organisations endorsing the consensus. A case of failing to see the forest for the trees.
  10. Poptech @210, That link failed to address the key flaw in the Petition Project, so you could hardly call it a "complete" rebuttal. Namely, by the standards of the petition, 31000 represents about 0.3% of the targeted population, even with the most generous calculations.
  11. Poptech, Science is decided by evidence, not signers of petitions. The reason almost all major scientific institutions agree with the mainstream view of global warming is because the scientific evidence overwhelmingly supports it. Notice the consistency on one side of the debate: CO2 is rising, leading to warmer temperatures and a potentially serious problem that should be mitigated. Compare to the inconsistency on the skeptic side: it's not warming, it is warming but it's the sun, it's not warming, it is warming but it's el nino, CO2 is causing warming but climate sensitivity is low, it's cooling, it's warming but it's cosmic rays, it's warming and it's CO2 but cap and trade sucks, the hockey stick has been debunked, it's cooling, it's warming but it's water vapor, it's cooling because of the sun, it's a statistical mistake, it's warming, it's cooling. Is that about it? Did I succinctly summarize the "skeptic" position correctly?
  12. Poptech, Yes and I pointed out that you were wrong, the link did not "completely" refute that video. The video points out that practically anyone with a B.S. degree is eligible to sign this petition. This is the key flaw in the Petition Project. The link you provided did not refute this claim.
  13. Breaking Consensus Update... U.S. National Academies today issues three reports from the National Research Council detailing climate change research results and remaining challenges, mitigation possibilities, adaptation requirements and hurdles. This is where scientific consensus leads: Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities. Summary, links to reports here: Strong Evidence On Climate Change Underscores Need For Actions To Reduce Emissions And Begin Adapting To Impacts The petition Poptech mentions is not very useful compared to what NAS has just published.
  14. Poptech #215 I think you mistake science for some kind of democratic process. Generally we weight the opinions of scientists on a topic as to whether they have a publication record in good quality peer reviewed journals related to the topic on which they have an opinion. To illustrate why your democratic approach is faulty, consider biological sciences. Ecology and molecular biology are both important fields. Ecologists use a lot of molecular biology technologies, but are not domain experts in the subject - they follow procedures rather than have a deep understanding of the underlying science. Molecular biologists can create organisms that alter ecosystems, but with a small number of exceptions, their education in ecology is almost non-existant. As a result it would be very wrong to use the opinion of a molecular biologist on the topic of ecology because they don't know anything about it. I reckon the same is very likely for the people you describe as scientists who contribted to the petition. It has very little meaning as far as the science goes, it's a political action which is entirely unrelated.
  15. This is relevant to this topic. It is from Roger Helmer talking before the 4th International Conference on Climate Change which he recently attended. Of the 80 speakers, I noticed that fully forty-five were qualified scientists from relevant disciplines, and from respected universities around the world -- from the USA, Canada, Mexico, Russia, Sweden, Norway, UK, Australia and New Zealand. All of them have reservations about climate alarmism, ranging from concerns that we are making vastly expensive public policy decisions based on science that is, to say the least, open to question, through to outright rejection of the Anthropogenic Global Warming (AGW) model. Several of these scientists are members or former members of the IPCC Intergovernmental Panel on Climate Change. But how do 45 sceptical scientists stack up, you may well ask, against the 2500 on the official IPCC panels? But of course there aren't 2500 relevant scientists on the IPCC panel. Many of them are not strictly scientists at all. Some are merely civil servants or environmental zealots. Some are economists -- important to the debate but not experts on the science. Others are scientists in unrelated disciplines. The Chairman of the IPCC Dr. Ravendra Pachuari, is a Railway Engineer. And of the remaining minority who are indeed scientists in relevant subjects, some (like my good friend Prof Fred Singer) have explicitly rejected the IPCC's AGW theory. Whittle it down, and you end up with fifty or so true believers, most of whom are part of the “Hockey Team” behind the infamous Hockey Stick graph, perhaps the most discredited artefact in the history of science. This is a small and incestuous group of scientists (including those at the CRU at the University of East Anglia). They work closely together, jealously protecting their source data, and they peer-review each other's work. This is the “consensus” on which climate hysteria is based. And there are scarcely more of them than are sceptical scientists at this Heartland Conference in Chicago, where I am blogging today. Never mind the dozens of other scientists here in Chicago, or the thousands who have signed petitions and written to governments opposing climate hysteria. Science is not decided by numbers, but if it were, there is the case to be made that the consensus is now on the sceptical side.
  16. And here is his comment after the conference: "I’ve just returned from the Heartland Institute’s Fourth Annual Climate Conference, at the Marriott Hotel in Chicago, where something very interesting was emerging: a clear counter-consensus on climate change. Of 700+ delegates, 400 or so were scientists in relevant disciplines – arguably more than on the IPCC’s much vaunted panel (after you allow for non-scientists, scientists in irrelevant disciplines, and dissenting reviewers). These scientists came from around the world, and from highly respected academic institutions. They were by no means unanimous, but all (except for two token Warmists) agreed that the IPCC “consensus” is deeply flawed, and that the policy prescriptions based on the IPCC’s work are extremely unlikely to deliver significant results." Looking forward to reading Robert Carters new book 'Climate -the Counter Consensus'
  17. Against the Chicago rally of policy think tanks, industrial interests and latter-day Don Quixote researchers bereft of a Panza to look after their linens, let's stack the National Academies of Science and their unit the National Research Council. NAS has just released a rather stunning compendium of climate research findings, mitigation options and adaptation possibilities. Here's the takeaway for us laypersons, from the climate research portion of the set: Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities. You can find the press summary of the reports here. A free-to-read version of the report is here Now I'm sure that we'll hear squawks from people entirely clueless about what the National Academies represents to the effect that the NAS is simply ensuring that grant money continue flowing but consider, if their conclusion is that anthropogenic climate change is a settled fact beyond dispute, that hardly serves as an incentive to pouring more money into research, does it? In any case such an argument is worthless in terms of offering an alternative to accepted research findings.
  18. Doug, it is a plea for more funding. "It calls for a new era of climate change science where an emphasis is placed on "fundamental, use-inspired" research,"
  19. Clearly this article shows that approximately 1 in every 5 earth scientists could not say that AGW was a fact. Also that 1 in every 4 non-climatoligists could not say that AGW was a fact. I know that's not a majority for the anti-AGW view and you could say that it is a general consensus for the pro-AGW view but when expressed this way (rounding to the nearest integer of course) I believe the true extent of dissent is portrayed. What is frustrating is that in the media the word "consensus" is used often with the catch phrase "a handful of dissenters" or "deniers" or "trouble makers" or something like that, but that is clearly not the case. ~20% is not an insignificant figure. I also make the point that those of us in fields other than the earth sciences who criticise climate science for poorly collected and presented data coupled with poorly argued conclusions (in my/our opinion of course), specifically on AGW, would not have a high level of respect for the publications that come from climatology and to a lesser extent earth sciences on this issue. You are not providing much of an argument to us by quoting phrases like "peer-review" and "consensus" when refering to climate science. If wikipedia's explanation of the peer-review process is accurate then in light of the figures given in the article above, the "peer-review" process in the field of climatology (or more widely in earth sciences) may be a very biased excercise indeed. Here is a link to the article: The wikipedia article seems to imply that only a few reviewers are needed as a minimum and the editor of a journal does not need a consensus amongst them since their role is advisory only. The wikipedia article implies that only "experts in the field" would be invited to review and so the survey results provided in the article above reveals an obvious potential for group think during the peer-review process. A survey of scientists outside of these disciplines would be much appreciated. How often is it said that climatology is a relatively new field? Well then... let some of the professors in the more distant fields of Physics, Chem, Mathematics and Statistics "Peer-review" these articles and we will see what kind of conlcusions are published then. It is ultimately a discipline on trial and I would ask the question "Are experts from other disciplines even bothering to spend time critiquing publications on climate science or are the police left to police themselves?" You may then say that the list of endorsing scientific organisations in the article above implies that the level of dissent in a broader scope of disciplines is roughly matched by the survey. Then please provide figures of % endorsed of worldwide scientific organisations etc. and I will be more willing to accept that. However, if the level of dissent within these sci. orgs is greater than that portrayed in the survey above then the picture of a "handful of dissenters" in my opinion may fall apart. Only the heads or a majority of the higher management of these organisations need to support the AGW view in order for the entire sci. org. to be listed. Many dissenters within these organisations may not be speaking out about their position on AGW even in private to their colleagues due to the potential for work place friction on this highly emotive issue. They may also be fearing dis-favour with their own organisational heads/management, who have already made their position offically known. I'm not talking about a conspiracy just the complications of work place issues that arise when speaking out about this subject. Sure majority rules and you may have it.. but don't tell me you have an overwhelming consensus until you can provide the overall numbers.
  20. Daniel, while it may be true that 20% of earth scientists have problems with the concept of anthropogenic warming, the number of scientists who have published work supplying a strong workable alternative hypothesis that meshes well with a complicated web of other findings not even necessarily directly related to issues of climate is essentially nil. An opinion is not science.
  21. Nor is a popular hypothesis truth. The article refers to a consensus amongst scientists apparently evidenced by a survey, literature searches and a list of endorsing scientific organisations and although this may be a start in proving an overwhelming consensus amongst scientists outside of the earth sciences I feel it does not adequately gauge the level of dissent. Further to this I point out the potential for group think within the climate sciences as outlined above. Which in my own opinion (to which I am entitled and I utterly reject any idealised notion that science is devoid of opinion or opinions, look up the definition of consensus and you will find it is a pluralised synonym of the word opinion) highlights the fact that just because something is published that does not automatically guarantee a quality of work. On top of that I would argue that many qualified professionals outside of the earth sciences may not even be engaging in a thorough critique of the data due to a lack of time or interest or perhaps an unjustified trust that work being done in fields distant to their own is of the same standard they would expect in thier own circles.
  22. Well that awful Inhofe 400 is now over 420 as in the time it took for you to complain about the one that didn't sign 20 more "scientists" did
    I'm 2 years late to the party, but for the record... Nobody signed Inhofe's list. It was created by garnering selected quotes and adding the person saying/writing them. A good number of the people on it actually endorse the IPCC general conclusions, and some have even written to ask to be taken off. Inhofe's 400+ is not a petition or a declaration, just a concoction of names and highly elided quotes.
  23. #1 roverdc at 17:32 PM on 27 September, 2007 Concensus only has meaning if there is no pressure to conform in either direction. No pressure, indeed.
  24. That video is not only disgusting, it's unscientific, completely ignores what we know of effective risk communication. 10:10 needs some grownup supervision.
  25. Here's a much more useful video:

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