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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

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 51 to 75 out of 908:

  1. frankbi I was referring to all the peer-reviewed papers, and the blogs that link to them. Legitimate or not, there is an awful lot of dissent. The conference you mention was more like a rally from what I have read about it. I really don't consider that dissent, although a few of it's speakers did post their papers on-line. I have read many papers on-line that are skeptical but not actually in opposition to the AGW hypothesis. Do you consider these to be dissenters?
  2. Frankbi, I believe the number 19 originally came from Andy Revkin's Dotearth blog. Andy Revkin later said that he had gotten emails from other scientists saying that there were several dozen more in attendence. Granted, its not 19,000, but its not 19 either. Beyond that, the 19,000 scientists are not all in climate related field, but apparently the Scientific American did some "crude extrapolating" and found roughly 200 climate researchers in the bunch. Again, not 19,000, but still a respectable number. The Oregon Petition isn't worth much anyhow.
  3. Robert S: Well, I couldn't find any concrete mention of any figures above 19... only some mentions of climate inactivists claiming there were "hundreds" of scientists there. Given that there were ~500 people in total, I wonder why they couldn't be more specific. In the meantime, Heartland Institute included a list of climate skeptic "co-authors" which included Mann, Rahmstorf, Keeling, and other well-known global warming theory _proponents_. And many scientists are angry about this: http://tinyurl.com/6zjxy4
  4. #52, Robert S., I don't know where you got 200 climate researchers were there, but there are over 20,000 climate scientists in the U.S. alone according to the AGU, so even there were 200 in attendance, and assuming they were all skeptics, that's still only about 1%. That would qualify as an overwhelming consensus in my book.
  5. Phillippe I don't see where you get the idea that the rate of increase of CO2 is unprecedented, or even relevent. It is supposed to be atmospheric content that makes the difference and by those standards we are not at or near anything extreme. So that argument doesn't work. But I guess that is another thread.
  6. since the topic in this forum is "the consensus" I thought I'd forward this http://www.desmogblog.com/500-scientists-with-documented-doubts...
  7. Paledriver (54), You misunderstood me: Frankbi said this "Remember the claim that there were 19,000 scientists disputing global warming? During the New York denialist conference ("2008 International Conference on Climate Change"), it turned out there were only _19_ scientists. Looks like the number 19,000 is off by a factor of 1,000." I responded to that point with this "Beyond that, the 19,000 scientists are not all in climate related field, but apparently the Scientific American did some "crude extrapolating" and found roughly 200 climate researchers in the bunch. Again, not 19,000, but still a respectable number." The 200 were supposedly from the OISM petition. And the link in your post at 56 is basically the same thing as frankbi's link at 53.
  8. Robert S. I did understand you. What I'm saying is #1, you don't know that the 200 that were, supposedly, there all disagree with the consensus and #2, 200 is an insignificant number when you realize that there are over 20,000 in the U.S. alone, and that this convention drew, I believe they claim, from all over the world.
  9. No, you didn't, and still do not, understand me. You said "I don't know where you got 200 climate researchers were there, but there are over 20,000 climate scientists in the U.S. alone according to the AGU, so even there were 200 in attendance" The 200 figure came from Scientific American when they looked at the OISM petition. There is nothing to attend regarding the OISM petition because it is a petition. You must be talking about the Heartland Conference. And I have been unable to find any concrete mention of 20,000 climate scientists in "the U.S. alone". The best I can find is an Eli Rabbett post in which Eli mentions 13,746 AGU members in climate related fields with a spread like this (quoting from Eli's blog): "-1956 Atomspheric -1564 Biogeochemistry -334 Cryosphere -751 Global climate change -4736 Hydrology -2326 Ocean sciences -634 Paleoclimate -2004 Volcanology (you can argue here if you want)" If you add foreign members, the number reaches 19,340. Now I understand what you are saying about the numbers, but please, don't make things up to prove your point. Though I never did think science was much of a popularity contest.
  10. what did I make up? My memory was a little muddy, my age perhaps, but the basic point is still there. There are about 20000ish members of the A.G.U. alone who are climate scientists, ergo 200 is about 1% or insignificant. And since we were talking about the conference, I naturally supposed you were too. It would have been better for you if you had, rather than that hoax of a petition.
  11. "what did I make up?" This: "there are over 20,000 climate scientists in the U.S. alone according to the AGU". Though I give you the benefit of the doubt (it is a big difference, however!) Anyhow, the comparison doesn't make sense --the OISM petition is Americans only, while the 20,000 includes foreign AGU members. And I don't know that I would call all of them "climate scientists": Some biogeochemists might be, majority probably are not, though they likely understand a part of the process, most volcanologists aren't climate scientists, etc... The actual number of *climate scientists* is probably much lower than 20,000 (or the 13,000 American AGU members). Then again, like I said above, I never thought science worked through popular opinion. "It would have been better for you if you had, rather than that hoax of a petition." I know the petition has it's problems, and it isn't exactly a major credible opposition to AGW, but I would hardly call it a hoax
  12. Apparently the number has increased for this new petition. In an article dated Monday, May 19, 2008 it says 31,000 Scientists Debunk Al Gore and Global Warming. Anyone know about this one?
  13. RobetS Re: "-2004 Volcanology (you can argue here if you want)" Probably the best of all sources listed. They have a better understanding of internal forcing than anyone else other than these groups: -4736 Hydrology -2326 Ocean sciences But where are the astronomers?
  14. If the Caribbean Academy of Sciences and the Royal Irish Academy endorse man made global warming can any person with a conscience still doubt? Mr Hansen from NASA's Goddard Institute thinks the doubters should be punished. Shouldn't they be given the opportunity to recant? Water boarding causes no lasting damage and requires no carbon use whatsoever, unlike burning at the stake, etc. Mr. Hansen let slip a prediction for the future. "All the Arctic sea ice will be gone in five to ten years." Going out on a limb, isn't he. He might be alive to reap the ricicule. I've marked my calendar: "Look for hell fire and inundation". For now, I'll keep the beach property.
  15. in response to number 62. this was when they claimes 17,000.....".. took a sample of 30 of the 1,400 signatories claiming to hold a Ph.D. in a climate-related science. Of the 26 we were able to identify in various databases, 11 said they still agreed with the petition -- one was an active climate researcher, two others had relevant expertise, and eight signed based on an informal evaluation. Six said they would not sign the petition today, three did not remember any such petition, one had died, and five did not answer repeated messages. Crudely extrapolating, the petition supporters include a core of about 200 climate researchers -- a respectable number, though rather a small fraction of the climatological community.". this from when it was first released......"The Marshall Institute co-sponsored with the OISM a deceptive campaign -- known as the Petition Project -- to undermine and discredit the scientific authority of the IPCC and to oppose the Kyoto Protocol. Early in the spring of 1998, thousands of scientists around the country received a mass mailing urging them to sign a petition calling on the government to reject the Kyoto Protocol. The petition was accompanied by other pieces including an article formatted to mimic the journal of the National Academy of Sciences. Subsequent research revealed that the article had not been peer-reviewed, nor published, nor even accepted for publication in that journal and the Academy released a strong statement disclaiming any connection to this effort and reaffirming the reality of climate change. The Petition resurfaced in 2001.". and more...."Of 100 names googled, only about 2 percent turn out to be scientists with any training relevant to climatology, usually physics. A small number -- about 15 percent -- were other kinds of scientists or physicians, but with no relevant training. Several in this overall pool of scientists were quite elderly. The remainder were either people with no scientific credentials whatsoever (40 percent), or names that did not appear in the search -- highly improbable nowadays if indeed such people existed." so the petition is clearly a fabrication.
  16. paledriver I was under the impression that this was a newer petition. Are you saying that this is the same one as the 20k scientists earlier in this thread?
  17. Will Nitschke There have been several updates to the link that you posted. Below is the latest one only. U.S. Senate Report: Over 400 Prominent Scientists Disputed Man-Made Global Warming Claims in 2007 Senate Report Debunks "Consensus" UPDATE: More and more scientists continue to declare their dissent of the ‘consensus.’ (LINK) Climate Skeptics Reveal ‘Horror Stories’ of Scientific Suppression (NYC Climate Conference Report - Part One of Reports) March 6, 2008 "Many prominent scientists participating and attending were very impressed by the New York City climate conference. Hurricane researcher and Meteorologist Stanley B. Goldenberg of NOAA (National Oceanic and Atmospheric Administration) in Miami praised the Heartland Instituted sponsored conference. “The fact is that this conference is evidence that there are numerous respected, established and in many cases world-renowned scientists who have done careful research in various areas of ‘climate change’ that sharply differ with the [UN] IPCC results,” Goldenberg told the New York Times."
  18. Qietman, if you go to the link provided by #62 you'll find it's the same old Petition Project by OISM. If you go to my posts 4,8,12,14 and 28 (to begin with) you'll get a start on that petition and the "inhofe 400".
  19. paledriver I have been following along but I did not realize that it was the same one because of the number and date. So this petition is still circulating?
  20. paledriver I went back and read it again. It seems to be from the same organization but it also seems to be a different petition, they mention one in 2001 with 19k+ signers, and then they talk about 31k signers with 9k+ PHDs. It does not really mean anything one way or the other as I don't accept consensus as proof of anything, if I did I would be Hindu or Buddist (I'm sure one of those two have a consensus).
  21. paledriver p.s. I put that link in 62 to see if anyone could tell me if it was the same as discussed previously.
  22. Quietman, you argument about consensus doesn't relate. In science, truth wins out over time. And over time, as more and more data comes in, the consensus on this matter grows. As I've said, I'm just a layman but I know that much at least.
  23. paledriver I'm not a scientist either, but as a research engineer I made much use of the scientific process. It does not matter how many believe a particular hypothesis is true, only the one that turns out to be right, regardless of how many backers it had. Working in the private sector, I had a lot of trouble getting some of my papers past managers who did not have a clue as to what I was talking about and believed otherwise, but once in the design staff's hands they understood and acted immediately (I have a lot of experience side-stepping managers). Let me give you a very good and reletively recent example: The late Dr. Rhodes Fairbridge studied the oceans for many years and determined that the sealevel rose and fell in cycles. It was named the Fairbridge cycle in DERISION because the consensus said he was wrong. It is now recognized to be correct and the consensus wrong. The hypothesis published in a science magazine in 1966 is the one explained by Dr. Riscard Mackey in his eulogy for Dr. Fairbridge. Again he went against the consensus but I think that he was correct. It was the only climate prediction made (last summer) that turned out to be correct thus far (it predicted low sunspot activity and cooling starting in 2008) and the IPCC, it seems, is finally paying some attention.
  24. paledriver I was rereading your post #65. Would you consider the description below qualified in climatology? "He obtained a B.A. in Physics and Mathematics with highest distinction in 1963, an M.S. in Astronomy in 1965 and a Ph.D. in Physics, in 1967, all three degrees from the University of Iowa."
  25. As a Ph.D. scientist, I can attest to the fact there is no consensus among scientists on global warming. So much so, that the American Physical Society has opened debate on the matter. http://www.dailytech.com/Myth+of+Consensus+Explodes+APS+Opens+Global+Warming+Debate/article12403.htm But facts like these seldom get in the way of religious fanatics, and anthropogenic global warming is a religion.

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