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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...

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

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 archive.org)

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.

Acknowledgements

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

Update

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

Comments

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Comments 526 to 550 out of 906:

  1. Well, I'm calling shenanigans.
  2. SB, context is everything. How are current conditions similar to Cambrian conditions in terms of major forcings/feedbacks (solar output, Milankovitch cycling, continental position, general circulation, biosphere, carbon cycle, etc.)? C99 - either shenanigans or simply unfamiliar with the history and literature of the theory. Looks like a job for Richard Alley.
  3. Here is a very interesting study recently carried out... http://scienceprogress.org/2012/11/27479/ According to this chap... "I searched the Web of Science, an online science publication tool, for peer-reviewed scientific articles published between January first 1991 and November 9th 2012 that have the keyword phrases “global warming” or “global climate change.” The search produced 13,950 articles.... By my definition, 24 of the 13,950 articles, 0.17 percent or 1 in 581, clearly reject global warming or endorse a cause other than CO2 emissions for observed warming." So 99.83% of the peer-reviewed articles relating to climate change available on the Web of Science endorse the theory of AGW. I think that pretty much clears up the consensus debate.
    Response: [DB] Fixed link.
  4. It all depends on what people they choose to exclude. If "Climate Experts" refer to academia involved in climate research, this is extreemly bias as anyone who disagrees with Global Warming would have to agressively argue with senior college professors; anyone who went to college knows this is not a very easy thing to do. However if you consider all the meterologists, a group of people no one can claim is uninformed on how the atmosphere works, the actual poll numbers are far less supportive of the alarmist Global Warming mentality. Only 89% even believe warming is happening, only 59% believe man is the primary contributor to it and less than half are "very worried" about the severity of the damage it could cause. http://www.forbes.com/sites/jamestaylor/2012/03/14/shock-poll-meteorologists-are-global-warming-skeptics/ OR http://www.ametsoc.org/boardpges/cwce/docs/BEC/CICCC/2012-02-AMS-Member-Survey-Preliminary-Findings.pdf
  5. How does one being polled have do argue with anyone?
  6. Jeff313 @529, by meteorologist you mean "member of the American Meteorological Society". As not only academic meteorologists, but also broadcast meteorologists (aka, TV weathermen) can be members of the AMS, and do not require any formal qualification, or even study in meteorology to do so, I do claim that some members of the AMS do not have more than superficial knowledge of how the atmosphere works. As it happens, only 52% hold a PhD. Only 56% actively published in the peer reviewed literature in the last five years, and only 12.88% where published primarily on climate change. That is, of those participating in the survey, only 13% have a reasonable claim to be expert on the topic. As it happens, we know from Doran 2009 that around 88% of Climatologists (excluding broadcast climatologists) believe humans are the primary cause of global warming. A little albebra tells us that 45% of responses to the AMS survey where from climatologists with PhD's who agreed that there was global warming, and that humans where the main cause; an only 6% of them doubted any part of that proposition. That the vast majority of climate change "skeptics" in the AMS are broadcast meteorologists, who may or may not have skills beyond those required to look good on camera and read a weather map. Certainly Anthony Watts has repeatedly demonstrated that you can be a broadcast meteorologist (and member of the AMS) and be clueless about atmospheric physics. By the way, even the broadcast meteorologists aren't that fond of AGW "skepticism". 70% of respondents thing that humans have caused at least half of the global warming and only 6% claim global warming was the result of natural causes. Likewise, 76% or respondents think global warming will be harmful, with only 2.4% thinking it is beneficial. Consequently your consensus of the non-experts still falls firmly on the side of the IPCC, despite your best efforts to spin the surveys findings.
  7. Jeff, I don't know where you're attending university, but at the university I teach at, the professors drive students to question them. Any student who produces a useful method or discovery is going to be helped into publication by the professor(s). Your comment strongly suggests you believe a hoax is being perpetrated, and that strongly suggests you have no idea how the scientific process works. And, btw, I've talked with plenty of meteorologists who do not understand the basic theory of anthropogenic global warming. Joe Bastardi leaps to mind.
  8. As Christopher Hitchens said, "Since we do not have a spare earth, best to err on the side of caution".  Don't you think ?

  9. The signature project has 31,487 signatures, of which 9029 have PHDs, all saying that it is not man made.  Makes it hard to believe that there is a 97% consensus.

  10. Kevin, you wouldn't ask your dentists to perform heart surgery.  There is an overwhelming consensus in the atmospheric and oceanic sciences.  But why look at a consensus of people?  Why not look at a consensus of evidence.

  11. Kevin,

    Are you as gullible as you seem?  Perhaps you should look into those signatures.

  12. Keven @535, some people like to quote raw numbers because they impress the gullible with their magnitude.  Less gullible as the question, "31,487 out of how many?"  

    If it were 31,487 out of 50,000, that would indeed be evidence that there is no concensus among scientists that the late twentieth century warming was man made.  As it turns out, there were   56,335,654 residents of the United States in 2009 who held a bachelors degree, or higher.  Over the period, 1966-2008, 30.8% of all degrees issued have been science and engineering degrees, so at a reasonable estimate, there were 16.9 million holders of degrees in science or engineering.  Or in other words, of those qualified to sign the petition in 2009, at most 0.19% signed it, or had signed it.  At most, because signature of the petition are not restricted to US residents, and have been open for many years so that not all petitioners where still living in 2009.

    So, in essence, you are claiming that there is no consensus in favour of climate change because less than 0.2% of people with a (any) scientific qualification disagree.

    I'm not impressed.

    Alternatively, there were 2,348,318 residents of the US with Doctorates (Phds) in the United States in 2009.  Over the period 1966-2008, 61.8% of all doctorates have been in science or engineering.  Ergo, the pool of candidate signors exceeds 1.4 million, of which only 9,029, or 0.64% have signed.

    I am impressed by the chutzpah of your logic, that because 0.64% of all scientists holding a Phd have signed a petition denying the science, that therefore it is not true that 97% of climate scientists agree that humans have caused the late twentieth century warming.  But, as I said.  It may take in the gullible, but not those with the full facts and figures before them.

    Further reading:  Meet the Denominator

    Data:  2009 Census

    NSF report

  13. OK, make that three threads where Kevin has dropped short, content-free comments in the "gotcha"/smear style.

    This kind of drive-by commenting reflects badly on you, Kevin.

  14. OK, make that three threads where Kevin has dropped short, content-free comments in the "gotcha"/smear style.

    This kind of drive-by commenting reflects badly on you, Kevin.This wasn't a drive by, smear comment.  The gist of this thread is that there is a 97% "consensus", implying that 97% of Climate scientists believe the AGW theory.  I was pointing out a piece of evidence, one that has more participants than some of the papers that came up with the 97% figure, that disputes that.  To say that the science is over because of 97% agreement is a pretty arrogant statement to make.  I'm sure that there was greater than 97% consensus that Newton was 100% accurate prior to Einstein "proving" that there was more to it.

    All it takes is one falsification to make a theory wrong, to think that "WE" know everything about everything that goes into making our climate what it is is pretty ignorant.

     

    No gotcha/smear intended.  I do appologize that I came/come across as a gotcha smear type.  I do want to understand more about this, but dealing with people who think they have all the answers, and that if you disagree with them you are either

    1. in denial,

    2.  in the employ of "big oil" or

    3.  Ignorant

    gets old pretty quick.

     

  15. Kevin, it would be delicious if you marked out the words of others with quotation marks.  

    You say: "To say that the science is over because of 97% agreement is a pretty arrogant statement to make."

    I agree. Now, whoever said "the science is over" is wrong.  To say that the basics of the theory of AGW are "settled," though, is right.  Settled doesn't mean concretized.  It just means that nothing is stirring it up.  The basics of AGW were settled over the last century.  There hasn't been a serious challenge to the greenhouse effect since Angstrom.  The effect has been demonstrated in lab, from satellite, and directly via ground-based instrumentation.  Working products have been made that rely on the same principles.  The other settled part of AGW is the "A" part.  There are no alternative theories where the source of the rise in atmospheric CO2 is concerned.  None.  And there is abundant evidence that it's us.  If you have an alternative that works, you'll be famous.

    You say: "I'm sure that there was greater than 97% consensus that Newton was 100% accurate prior to Einstein "proving" that there was more to it."

    This is a false analogy.  You're suggesting that the levels of evidence for the compared are the same.  Not even close.  There are tens if not hundreds of thousands of people working in atmospheric and oceanic sciences.  The 97% figure was for a small group of regularly-publishing climate scientists.  How many people were working on gravity in Newton's day?  Even Einstein's day?  How robustly were the theories being tested?  If you want to see the weight of evidence--the consensus of evidence--see it here.  Or see it in the tens of thousands of publications that fill the reference sections of the IPCC ARs.

    You say: "All it takes is one falsification to make a theory wrong, to think that "WE" know everything about everything that goes into making our climate what it is is pretty ignorant."

    Who said we did?  Again, you build this strawman that says, "Climate scientists say they know everything!"  No one has ever said that.  It's funny: I argue with people regularly who condemn the IPCC for using words like "likely" and "high probability" and "medium confidence."  They want science to be absolute.  Science refuses to be absolute.

    Until you understand the evidence, it will be all too easy to read words like "settled" and "know" uncritically and mistakenly.  It is extraordinarily difficult to communicate the science to the public.  Everything is interconnected, and so everything needs to be properly contextualized.  The "16-year no warming" meme is just the latest great example of that.  The denial industry--and it is an industry, from Heartland to GWPF to SPPI and beyond--knows the difficulty, and they take advantage of it.  The focus on the words scientists use, ignoring the content of the message.  They take words like "consensus" and "settled" and spin them to make them look dishonest or anti-scientific.

    And then the public, Kevin, unaware of the game playing, does the heavy lifting by accusing the science and its defenders of being dishonest. Most of the people I discuss the issue with are not in the pay of the oil industry or one of the free market opinion-making organizations.  However, some are.  There are face-bots, or ideo-bots, created by these institutions solely for the purpose of engaging comment streams with a set of well-oiled memes.  These bots never come back to defend their comments.  There is nothing to hold them accountable for their misinformation and misrepresentation.  Yet there it is, and the public has no basis for deciding what's misinformation and what isn't.  

    This may explain why you get a strong reaction when you post an evidence-free accusation. It's in the standard playbook for paid denialists.  My advice to you is to use questions and refrain from accusations, unless you have the evidence to support them and you're willing to  defend that evidence (or change your mind if other evidence is brought to bear).

     

     

  16. Kevin, to reiterate; the article above points out that several studies have found 97% of climate scientists accept the evidence that the Earth has warmed, and that human emissions of greenhouse gases is the primary cause of that warming.

    Now, you wish to present as counter evidence that less than 0.2% of people in the US with a scientific qualification of any sort disagree.  In essence your argument boils down to the claim that:

    Less than 0.2% of people with a scientific qualification have expressed an opinion contrary to the consensus on climate change;

    Therefore,

    It is false that 97% of the scientists best qualified to assess the subject accept the concensus.

    Your argument needs only to be stated for it to be seen that it is false.

  17.  A useful example of the silliness of some of these polls/petitions is Project Steve, which is limited to people named Steve. It's about evolution, but it has over 1200 signatures now. Is it evidence? Evidence of what? Is there anything special about people named Steve that gives them increased credibility as "experts" in this subject matter?

  18. I've waded into some discussions recently and have presented some of the points here on the consensus. This to me is a very key issue, because if one cant discredit it, then the only option is looney conspiracy theories involving very large numbers of scientists over decades. Lets face it, the average (and even not so average) person is not going to be able to comphrehend and judge the detail of any scientific discussions. Its all about who you are willing to trust.

    I came across a rebuttal quoting Andrew Montford at bishop hill quoting Brandon Shollenberger. Now I know many feel that Shollenberger is an extreme wingnut, and Troll who is best not fed, but he is all excited about finding a hole in theconsensus project.

    http://www.bishop-hill.net/blog/2013/5/17/cooks-unreported-finding.html

    http://rankexploits.com/musings/2013/on-the-consensus/ 17May2013.

    It took me a little to understand what he is on about. His statements on the relative numbers of each Endorsement levels. A reminder that these levels are:
    1. Explicitly endorses and quantifies AGW as 50+%
    2. Explicitly endorses but does not quantify or minimise
    3. Implicitly endorses AGW without minimising it
    4. No Position
    5. Implicitly minimizes/rejects AGW
    6. Explicitly minimizes/rejects AGW but does not quantify
    7. Explicitly minimizes/rejects AGW as less than 50%
    8. Undecided

    His incorrect claim is that the top rating 1 - (only 65 papers) is smaller than the "Oppose AGW" numbers at 77 rejects. But he is comparing Level 1 alone with the bottom 3 levels 5,6 and 7.

    The correct comparison of course is top 3 with bottom 3, which is 3898 Endorses vrs 77 rejects, and 7976 that state no opinion.

    Amazing at how they are grasping at straws to overcome a mountain of evidence. Well .. disgusting actually.

  19. PeterBCourt:

    Even if one does not feed the trolls, misinformation must still be examined and addressed.

    So your unveiling of Schollenberger's straw-grasp is IMO a very useful exercise.

  20. "There are no national or major scientific institutions anywhere in the world that dispute the theory of anthropogenic climate change. Not one."

    Is there a reference for this statement ?

  21. Participley, as far as I know, no one has published a complete list of scientific organizations' positions on AGW.  However, the professional denial industry hasn't located any organizations that disagree, and they'd be the ones most anxious to find such an organization.  Perhaps you can locate one? 

  22. I should also point out that it's unlikely that any organization of professional scientists would actually issue a statement rejecting the theory.  Such a move would require evidence, and no such evidence exists.

  23. participley...  The wiki page on the scientific opinion on climate change they have this statement regarding dissenting opinions:

    "As of 2007, when the American Association of Petroleum Geologists released a revised statement,[11] no scientific body of national or international standing rejected the findings of human-induced effects on climate change.[10][12]"

    If anyone can find a legitimately recognised scientific body that rejects climate change, I think everyone here would be interested to know about it.

  24. [-snip-]

    Response:

    [RH]  Your question has been responded to.  Reposts of the same question have been deleted.

  25. participley, I've just gone through all of them.  I can't find one that has issued a statement of disagreement.  Did I miss one?

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