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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 76 to 100 out of 908:

  1. Austerlitz The blog that you gave the URL for was interesting but I found the actual APS newsletter even more interesting.
  2. Quietman, Here is another scientist who writes some compelling arguments against the theory:,25197,24036736-7583,00.html I have not checked his credentials; however, I find his arguments convincing. Of course, the Inquisition will dismiss him, as the consensus has already spoken.
  3. Austerlitz Thanks for the link. I have posted it at the LiveScience website in an argument that I'm having with one of the NASA guys who isn't a climatologist. Not being a scientist it's hard to be taken seriously so I appreciate the link.
  4. An outright lie about the American Physical Society "The newest denialist talking point Physicists reaffirm that human-induced GHGs affect the atmosphere Posted by Andrew Dessler (Guest Contributor) at 1:23 PM on 18 Jul 2008 Read more about: climate | climate science | climate change skepticism | greenhouse-gas emissions | scientific research Tools: print | email | + digg | + | + reddit | + stumbleupon It goes something like this: The American Physical Society, an organization representing nearly 50,000 physicists, has reversed its stance on climate change and is now proclaiming that many of its members disbelieve in human-induced global warming. Of course that's not true. Today a statement appeared on the APS website saying: APS Position Remains Unchanged The American Physical Society reaffirms the following position on climate change, adopted by its governing body, the APS Council, on November 18, 2007: "Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth's climate." An article at odds with this statement recently appeared in an online newsletter of the APS Forum on Physics and Society, one of 39 units of APS. The header of this newsletter carries the statement that "Opinions expressed are those of the authors alone and do not necessarily reflect the views of the APS or of the Forum." This newsletter is not a journal of the APS and it is not peer reviewed. For a list of societies that have endorsed the mainstream position on climate change, see this post."
  5. here's those credentials for you, auster.... "Who is 'Rocket Scientist' David Evans? 22 Jul 08 UPDATED: David Evans has sent along his definition of a rocket scientist. See below for details. This title grabbed our attention: Top Rocket Scientist: No evidence C02 causes global warming. And it should. It is a pretty bold statement and the implications would be pretty big news. So we decided to compile a backgrounder on 'The Top Rocket Scientist." Here's the research database entry on David Evans: No peer-reviewed articles on climate change According to his own resume, Evans has not published a single peer-reviewed research paper on the subject of climate change. Evans published only a single paper in 1987 in his career and it is unrelated to climate change. Evans has published an article for the Alabama-based Ludwig von Mises Instutute, a right-wing free-market think tank. Evans also published a "background briefing" (pdf) document for the Australian chapter of the Lavoisier Group, a global warming "skeptic" organization with close ties to the mining industry. "I am not a climate modeler" From 1999 to 2006 Evans worked for the Australian Greenhouse Office designing a carbon accounting system that is used by the Australian Government to calculate its land-use carbon accounts for the Kyoto Protocol. While Evans says (pdf) that "[he] know[s] a heck of a lot about modeling and computers," he states clearly that he is "not a climate modeler." Background David Evans lives in Australia and gained media attention after an article he wrote titled, No Smoking Hot Spot was published in The Australian in June, 2008.The article claims that climate change is not caused by C02 emissions because there is no evidence of "a hot spot about 10km up in the atmosphere over the tropics." Evan's claim has been thoroughly debunked by Tim Lambert, a computer scientist at the University of New South Wales. According to his bio, Evans claims to be a 'Rocket Scientist' and one article claims that he is a 'Top Rocket Scientist.' While Evans background does show that he has a PhD in electrical engineering, there is no evidence that he was ever employed as a rocket scientist. Evans answered our inquiry about his claim to being a rocket scientist with the following explanation: In US academic and industry parlance, "rocket scientist" means anyone who has completed a PhD in one of the hard sciences at one of the top US institutions. The term arose for people who *could* do rocket science, not those who literally build rockets.Thus the term "rocket scientist" means someone with a PhD in physics, electrical engineering, or mathematics (or perhaps a couple of other closely related disciplines), from MIT, Stanford, Caltech, and maybe a few other institutions. I did a PhD in electrical engineering at Stanford in the 1980s. Electrical engineering is your basic high tech degree, because most high technology spawned from electrical information technology. I specialized in signal processing, maths, and statistics. The definition provided by Evans would appear to be at odds with the conventional use of the term 'rocket scientist' which according to various sources is "One specializing in the science or study of rockets and their design." For example, here's an entry on about Hermann Oberth a famous Rocket Scientist who published a book about rocket travel into outer space in 1932 and is considered one of 3 founding fathers of modern rocketry and astronautics. Evans also claims to be "building a word processor for Windows." DeSmogBlog contacted Microsoft Corp. and they have confirmed that he does not work for Microsoft Corporation."
  6. paledriver You are talking about two peoples seperated by a common language. American connotation varies state to state and even city to city and you nit pick over the connotation of a word used on the opposite side of the world. A little strange I would say. He used the slang meaning of a rocket scientist in a way that an American would not but how is this term normally used in Australia? Maybe John can tell us.
  7. PS Publishing peer reviewed papers does not a scientist make.
  8. Paledriver, There was no outright lie about the APS. No one said their position changed (a strawman argument); rather, that there is debate. Granted, it turns out it was a subset of the APS, but it is still part of the APS. Here is the link from the APS website: Partially quoted herein: "With this issue of Physics & Society, we kick off a debate concerning one of the main conclusions of the International Panel on Climate Change (IPCC), the UN body which, together with Al Gore, recently won the Nobel Prize for its work concerning climate change research. There is a considerable presence within the scientific community of people who do not agree with the IPCC conclusion that anthropogenic CO2 emissions are very probably likely to be primarily responsible for the global warming that has occurred since the Industrial Revolution." Personally, I think you do your self a disservice quoting a smear site ( that only seeks to discredit and personally attack those who argue against anthropogenic warming. Arguing semantics about "rocket scientist"? Contacting Microsoft Corp. because he says he is "building a word processor for Windows"? Is this disgraceful behavior all the Inquisition has to offer?
  9. I missed that windows comment entirely. Writing a program for windows is not the same as writing for microsoft. It means to run on the windows O/S rather than on a unix or Linux or Mac O/S. Most likely using an MS language for compatibility like visual basic.
  10. Consensus: lit. to think alike or to be in general agreement with others. If most people think the same thing then it has got to be true hasn't it? Even when what they think is based on an incomplete understanding of the thing they are discussing? But hey, everybody is entitled to an opinion surely? And doesn't that include scientists on both sides? As stated by someone else..consensus is NOT science. Opinion is NOT science. Science is about hard, repeatably demonstrable, irrefutable, facts.
  11. "... very probably likely to be primarily ..." ... that sure convinces me!
  12. From this weeks "Skeptic of the week": "In particular I am referring to the arrogance, the activities aimed at shutting down debate; the outright fabrications; the mindless defense of bogus science; and the politicisation of the IPCC process and the science process itself." LOL - I Love it!
  13. #83. Yes that claim WAS made..."The American Physical Society, an organization representing nearly 50,000 physicists, has reversed its stance on climate change and is now proclaiming that many of its members disbelieve in human-induced global warming. " from Daily Tech.. so you got it wrong, again. and Mizimi, scientists have come to a consensus BECAUSE of the haed, irrefutable facts. and it's a growing consensus because of there continues to be more hard, irrefutable evidence uncovered. meanwhile, the other side consists mostly of former big tobacco schills who once told us there is no science to link smoking with lung cancer. remember that when you're picking your team.
  14. #88 Yes we have a lot of facts, some hard, some soft (paleoproxies for example), some incorporated into models and some unable to be included in detail (clouds and water vapour); do we know all the facts or even enough to make decisions that will adversely affect the lives of millions of people? Are those models sufficiently close to reality to act upon? Ah but, you will no doubt say, global warming will affect millions of people too.........according to those imprecise models. Recent GMT history says different. I don't disbelieve in human induced warming, I just don't accept the projected figures because it doesn't appear to be happening at the rate predicted, and those models are unable to incorporate components that have a major impact on the resultant. So why would I trust them?
  15. #88 Can you provide some links for your claims? Thanks in advance.
  16. Re: Post #77 from Austerlitz - if you pin your hopes on 'skeptics' like David Evans, maybe you should see this article (by David Evans) posted on the Lavoisier Group website (Australian 'skeptics' org with links to the coal industry, among others). See the 5th from last paragraph, starting 'I emphasise that we are making a bet...'. Evans estimates that the likelihood that CO2 emissions are the dominant cause of global warming is only 20%, not 90% as per the IPCC estimate. Note the wording - 'dominant' cause. I understand Richard Lindzen is now also similarly lukewarm on the odds. Maybe others could confirm. If there was only a 20% chance of your house burning down, would you go without insurance? With skeptics like that, who needs believers? P.S. I am not a scientist (published or otherwise), but a risk management professional. I am curious as to what the risk appetite of those participating in the global warming debate is - just how much risk of dangerous climate change is acceptable?
  17. #88: Exactly right. I don't have a problem with a few skeptics stating their opinion. I do have a problem, however, with gross distortions and dishonest rhetoric. In this case, a single APS member and editor of one of their many non-peer-reviewed newsletters decided to post his opinion and some material. It gets widely reported among the denialsphere as "The American Physical Society, an organization representing nearly 50,000 physicists, has reversed its stance on climate change". There is a clear and concerted effort to blow every fabric of data well out of proportion, whether it's of scientific nature or in this case, activities of an APS member. This is the reason why many climatologists don't have a lot of respect for the arguments from many of those who call themselves climate "skeptics". Dr. John Holdren (recently selected as Obama's science advisor), describes it best. He had a good op-ed piece earlier this year with an even better follow-up.
  18. Holdren, like Hansen, is a known alarmist. These are the people that call skeptics deniers. In science you propose a hypothesis and test that hypothesis in a manner that other scientists can reproduce. You DO NOT call the other scientists that disagree with you "deniers" because they happen to disagree, especially when they provide evidence to disprove your hypothesis.
  19. Re: "If there was only a 20% chance of your house burning down, would you go without insurance?" Assinine comparison.
  20. #93 They are called "deniers" when they resort to the type of tactics described in Dr. Holdren's op-ed, the clearly dishonest APS spin described above, repeatedly making multiple dubious claims as catalogued nicely on this website (while arrogantly and falsely asserting it "disproves" AGW and promoting their claims to any willing media outlet), calling global warming a "hoax", or calling the overwhelming majority of climate scientists "alarmists" because they don't like the implications of the science. Holdren makes the distinction between "skeptic" and "denier". Every scientist is a skeptic so that doesn't say much. "Denier" might be to harsh. I'd settle for "contrarian". A comment from another scientist on this issue: “They argue not as scientists but as lawyers. When they argue, they pick one piece of the fabric of evidence and blow it up all out of proportion…Their purpose is to confuse.” - Pieter Tans #94 You're right. It's conservatively more like 90%-95%. Personally, I thought it was time to act when IPCC2 presented the "more likely than not" conclusion regarding "most of the observed warming" before moving on to "likely" and "very likely". Of course, mitigating actions carry their own risk. If we decided to cut emissions 95% in 5 years, it would very likely cause severe economic damage. However, every objective economic study on mitigation proposals made so far suggest relatively affordable net economic costs in comparison with the risks this century (even the relatively conservative estimates) if we don't act. A few studies result in net gains - and most studies don't consider the economic benefits of decreased reliance on foreign fossil fuels and some of the avoided massive economic costs of climate change. Thus, it's ironic that those preaching gloom and doom on the economy call many scientists "alarmists".
  21. Re: post #94 - 'Assinine comparison': how so? It may be an oversimplification to describe anthropogenic climate change as a house fire and cuts to emissions as insurance, but with odds like this, would you go on with business as usual, or might you be inclined to make changes at reasonable cost, ahead of absolute certainty? Re: post #94: add geopolitical stability to the list of spin-off benefits. No need for a war for oil.
  22. Risky at 15:09 PM on 1 January, 2009 Re: post #94 - 'Assinine comparison': how so? Because your house CAN burn down, it is possible. This is very different from AGW since AGW is 1. Hypothetical, based on poorly written fortran code. 2. Historically false, If the CO2 was the powerful GHG it is claimed to be there would be no life on this planet. Upper Mesozoic and early Cenezoic had a constant extremely high level of CO2. Life flourished, our ancestors appear at the PETM, ie. it is the climate we evolved in. On the flip side, we nearly went extinct along with our Neandertal ancestors in H4 (glacial maximum) ***. It is COLD not hot that causes extinctions. So while warming will cause a few adjustments it would not be the catastrophe prophesized by algore and his followers. The alarmists base their science on the concept of equilibrium and deny that the earth goes through cycles and yet they call skeptical scientists "deniers". Skeptics realize that we are undergoing climate change, it is not AGW, it is not GW, it IS climate change, plain and simple. The amount of AGW added to this change is meaningless. All I have asked since day 1 is to see proof of this catastrophic GW. None has been provided, only that there is CC, no GW other than what is expected by natural cycles such as the PDO, Sun spot cycles and plate tectonics. *** "Neanderthal Extinction by Competitive Exclusion" William E. Banks1*, Francesco d’Errico1,2, A. Townsend Peterson3, Masa Kageyama4, Adriana Sima4, Maria-Fernanda Sa´nchez-Gon i5 There is a link to the above paper at the bottom of the article: Competition, Not Climate Change, Led To Neanderthal Extinction, Study Shows ScienceDaily (Dec. 30, 2008) For alternate reasons for climate change see (under arguments heading at the top of this page) The PDO and Volcano and sensitivity articles. Or you can just assume the alarmist position (fingers firmly in ears and eyes shut) and ignore the arguments entirely. To deny the facts is to show ignorance, that is not what science is about, that attitude belongs firmly in religion and politics.
  23. correction to 97: Neandertal ancestors s/b Neandertal cousins because the debate on admixture indicates that they were not ancestral to H. sapiens.
  24. NewYorkJ They are called "deniers" because they are skeptics, plain and simple. This is what happens to science when fanatics reach a level of majority, we return to the dark age when dissent is punishable, in this case by infantile name calling.
  25. Re: “They argue not as scientists but as lawyers. When they argue, they pick one piece of the fabric of evidence and blow it up all out of proportion…Their purpose is to confuse.” - Pieter Tans This describes the AGW alarmist to a T.

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