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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 501 to 525 out of 908:

  1. Jdey123, what do you make of that paper from Hansen et al. 11 years ago? Did you read the whole thing, and do you think that Hansen currently thinks that CO2 is not the dominant forcing where recent warming is concerned? It's easy to point to abstracts and say, "see! see!," but perhaps you can tell us what you think the paper says. I do note that it does say that CO2 and CH4 are the principal GHGs.
  2. Jdey #497 It's hard to forecast the weather more than a few days ahead, yet amazingly we can have (in the NH) real confidence that June will be warmer than December, and that June's temperature will lie within a particular range. GHGs play the role of the height of the Sun in the climate version of this analogy - the strong longer-term forcing that does not immediately dominate the vagaries of day-to-day weather, but inevitably wins in the end. Scientific theories are the best we have (read up on what a theory is). What are scientific 'facts'?
  3. I dont think Hansen 2000 establishes a crack in the consensus. The uncertainties were quickly resolved and in Hansen et al, 2002: "Climate forcings in Goddard Institute for Space Studies SI2000 simulations" Hansen was able to conclude: "The greenhouse gas forcings are known with reasonably good accuracy. CO2 (1.4 W/m2) has the largest forcing, but the CH4 forcing is half as large when its indirect effects on stratospheric H2O and tropospheric O3 are included, and the sum of non-CO2 greenhouse gas forcings exceeds the CO2 forcing." AR4 papers improve on that. The current knowledge on greenhouse attribution can be found in Schmidt et al 2010. Got anything that challenges that paper?
  4. In the Crock of the Week video above, I thought the stuff about characters from Deliverance was un-called for, showed class prejudice, and was counter-productive. Snobbishness and elitism is no way to convince climate change denialists. I've known lots of dolks with Appalachian roots, and this is offensive.
  5. The Bulletin of Atomic Scientists just moved the Doomsday Clock one minute closer to midnight (11:55). Meaningless to the science, but something worth noting anyway within the domain of climate science communication. From the report in the Guardian: "A number of the scientists who took part in the deliberations said they were also dismayed by a growing trend to disregard science." "On climate change, the scientists warned the global community may be reaching a point of no-return unless there is a push to begin building alternatives to carbon-heavy technologies within the next five years."
  6. Not that having a consensus is necessary to validate a theory, but just dealing with this argument, the first sentence of the article "Science achieves a consensus when scientists stop arguing.", would say there isn't a consensus since scientists are clearly still arguing!
  7. Consensus means that a large majority of people, or in this case scientists, agree that something is happening. There is obviously not consensus since not all scientists agree on whats happening or whats causing it. The large debate going on here is proof of that fact. Obviously there isn't enough information because science is fact and if the evidence was in there would be a consensus. Science is clear and if there was proof that the world was getting warmer or even not getting warmer scientist would agree and make up there mind like they did with gravity! Thank you
  8. YellowElephant @507 - you just contradicted yourself, first saying consensus is "a large majority", then saying there is no consensus because "not all scientists agree". Which is it, a majority, or unanimity? You were right the first time - consensus is a majority. In the case of man-made global warming, it's a vast majority (over 97% of scientific experts in agreement), as discussed in the post above.
  9. There is obviously not consensus since not all scientists agree on whats happening or whats causing it.
    Perhaps you can clarify here, YellowElephant, as to which scientists disagree. Are they climatologists or scientists in closely-related disciplines? And what is the basis of their disagreement? To my knowledge, even abject contrarians such as Spencer & Lindzen agree that heat-trapping gases (CO2, CH4, H2O, etc) cause global warming and that humans have emitted significant amounts of long-lasting heat-trapping gases. Their points of disagreement with the mainstream position lie elsewhere. When over 97% of scientists with relevant expertise agree on the basics of AGW and, as far as I am aware, every major national scientific body (NAS, Royal Society, &c) agree with the major conclusions of climatology as identified by the IPCC, and when even contrarian scientists agree with the basics, then IMO there is no "large debate" going on at all. Instead, there is what medical blogger Orac calls a 'manufactroversy'(*), where non-scientific interests attempting to defend or upend a status quo rely on various contrary arguments, increasingly of poor quality, to create the illusion of a genuine scientific debate. ----- (*) I'm not certain that Orac coined the term, however his use of it is the first I am aware of. (Orac blogs elsewhere under his real name, so my pronoun use is correct.)
  10. YellowElephant, you can easily tell when a consensus has been reached by working scientists and scientific organizations. Consensus occurs when scientists stop spending time, money, and energy to test hypotheses within an area. People stopped working on testing the radiative properties of atmospheric gases decades ago. The radiative properties of CO2 are well-established. Now, you might get the odd working engineer or geologist who doesn't understand the idea of pressure broadening, and who will make a claim like "CO2 effect is saturated!" The basics of AGW are old hat, even though blog sciency types keep making bizarre claims about them. Actual science has long since moved on to build successfully on those basics. As far as the human element goes, I've never heard an argument from a working scientist that makes the claim that we are not the source of the additional atmospheric CO2. I've read the opinion and work of hundreds and hundreds of working scientists who readily accept the mass balance argument corroborated by isotope studies. If you think you have evidence that there is not a consensus, present it. Change my mind. I take it that you have no time, energy, or training to work on understanding the science yourself. If that is the case (as it is with most of the general population), ask yourself why you believe what you believe. Why believe source X (who argues with great passion but no evidence) rather than source Y (who argues with evidence from a broad range of scientific disciplines).
  11. So a consensus in science is different from a political one.
    In theory, yes. Does though assume that scientists behave as scientists ought to, eg making their data available etc etc, and more generally searching for truth rather than pushing an agenda. Which, when the sole funder of a science is political institutions, may be easier said than done. And so an apparent science consensus may in reality be a political consensus in disguise.
  12. Example, Punksta? The social construction of knowledge via the scientific method takes the garbage out eventually. The more scrutiny the discipline gets, the quicker the garbage is taken out. I can't think of a discipline that is not funded by a political institution(s). Solely? Probably not. I keep thinking of Jeffrey Wigand's research while he was working for a tobacco company. He did good work, but he wasn't allowed to publish his findings (often the case with private research). The scientist wasn't the problem, though. Wigand wasn't pushing an agenda (well, not true - he was working on smoke-free cigarettes and that may be why he decided to work for the company); the political institution (the company) was the corrupting force (well, it didn't force Wigand to lie about his findings; it just prevented publication either in physical expression (engineered product) or in sharing with the rest of the world). The diversification and dispersal of science throughout the university system is a good way to keep politics (in the mainstream sense) from taking a heavy hand in most sciences.
  13. The best evidence of consensus on ACC appeared in the Proceedings of the National Academy of Scienc (PNAS), April 9, 2010 (Anderegga, Prallb, Haroldc, and Schneidera). Does anyone have something more recent or definitive? Abstract Although preliminary estimates from published literature and expert surveys suggest striking agreement among climate scientists on the tenets of anthropogenic climate change (ACC), the American public expresses substantial doubt about both the anthropogenic cause and the level of scientific agreement underpinning ACC. A broad analysis of the climate scientist community itself, the distribution of credibility of dissenting researchers relative to agreeing researchers, and the level of agreement among top climate experts has not been conducted and would inform future ACC discussions. Here, we use an extensive dataset of 1,372 climate researchers and their publication and citation data to show that (i) 97–98% of the climate researchers most actively publishing in the field support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.
  14. By the way, the SkS article here (in the "intermediate tab") gives a beautiful graph, but not as much text information as appears in the Abstract above (503)...e.g. the 1,372 climate researchers figure. It would also help to know more about the selection criteria for the dataset of respondants. Can anyone provide with a link to the full article?
    Response: [DB] The abstract has a link to the full article, on the right side of the page. It is also found here.
  15. OPEN ISSUES: Does the statement, “From 82% of earth scientists to 98% of climate experts agree humans are causing global warming.” accurately reflect what the studies show? It is unclear that the two studies cited here (Doran 2009 and Anderegg 2010) adequately represent contrarian views. Does either study eliminate elitism or biased sampling? The Doran study was not a random sample, but rather a reflection of about 30% who took the time to respond to an on-line study. The respondents were almost exclusively American. Are there studies or polls from other countries that show similar results? Anderegg et al started with a database of 1,372 climate researchers based on authorship of scientific assessment reports and membership on multisignatory statements about ACC. “We provide a broad assessment of the relative credibility of researchers convinced by the evidence (CE) of ACC and those unconvinced by the evidence (UE) of ACC.” Their Materials and Methods explains how this was done. “We then imposed an a priori criterion that a researcher must have authored a minimum of 20 climate publications to be considered a climate researcher, thus reducing the database to 908 researchers.” They claim this did not materially alter results, but they later state, “researchers with fewer than 20 climate publications comprise ≈80% the UE group, as opposed to less than 10% of the CE group. In other words, they removed 80% of the initial UE group, and only 10% of the CE, Can we cite more recent studies, or polls taken among climate scientists of other countries and different affiliations? Sites like World Climate Review will throw an elephant through any cracks we give them. PROPOSED DISCLAIMER: No poll or survey is perfect. Error margins should be expected.
  16. Tom, the point of Anderegg is to assess the consensus among climate experts, and in their opinion people with fewer than 20 climate-related publications are not experts. You may disagree with that definition of expertise, but it doesn't reflect "bias". I'm not aware of any more recent studies, but as it so happens, the SkS team is currently working on the definitive demonstration of the AGW consensus.
  17. Dana, I was surprised that the threshold for “expert” (20+ published papers) was so high. But I'm not a researcher, so maybe that is reasonable. The authors were admirably clear as to why and how they determined “expert” vs. “non-expert”, which was the main point of their study. Still, trying to play the Devil's Advocate of a contrarian, eliminating (1,372 - 908) of the climate scientists in the first step means that none of these 464 were reflected in the graphs that followed (Fig 1,2,3). Since the UE group is already humbled as being less published than the CE group, not even including them in overall percentages adds insult to injury. Someone may cry “foul”, justly or unjustly. If may look like elitism to outsiders. From the paper: “The UE group comprises only 2% of the top 50 climate researchers as ranked by expertise (number of climate publications), 3% of researchers of the top 100, and 2.5% of the top 200, excluding researchers present in both groups (Materials and Methods). This result closely agrees with expert surveys, indicating that ≈97% of self-identified actively publishing climate scientists agree with the tenets of ACC (2).” (Doran 2009) I would have preferred the authors go on to include what % the UE group represents out of the full 908, or even the original 1,372. The authors have made it very clear that the most published and most cited researchers are 97% to 98% CE vs. 2% to 3% UE. That's all well and good. But to stop there seems a little too pat and could raise a contrarian's suspicion that it is contrived to match the Doran results of the previous year. It leaves a reader with a simple question, “What are the percentages of CE and UE among 'non-expert' climate scientists?” Simple question, but hard to answer from reading their paper.
  18. 'The fact that there are so many Academies of Science endorsing the global warming position is probably the strongest argument for supporting it.' - Will Nitschke, on the 21st Dec. 2007, post 3. No, that's not a good reason at all. You've basically stated that if enough authority figures, from prestigious institutions, endorse an idea then we, the general public, should accept it. I can think of a better reason to accept an idea; examine the merits of it, the evidence both for and against it, weigh the probabilities of it being true, and then come to an independent assessment of its likelihood. If the idea in question is far more likely to be true than not - then, and only then, should you accept it.
  19. Yah, true Peter. However, there are a whole lot of people who do not have the time, energy, training, and/or motivation to do the math and read the literature. They need an interpreter. Who should they choose? Upon what basis should they make such a choice? You yourself have not read the literature -- that is clear from your other comments. Again, upon what basis do you speak so confidently?
  20. If someone is concerned enough about this issue, then they will find the time and motivation to 'do the maths and read the literature'. They do not 'need an interpreter'! This is reminiscent of the view widely held not so long ago that in order to 'know the mind of God' one needed to consult a priest who could act as an 'interpreter' of his will, thus keeping the poor peasants in the dark. Who would you choose to be your interpreter? (-snip-). My 'other comments' make it clear that I have not 'read the literature'? Really? In your opinion only.
    Response: [DB] Please read the Moderator Response to you here before placing further comments in this forum. Sloganeering snipped.
  21. @Peter A #518: The body of scientific evidence about anthropogenic global warming is not an “idea”, it is a body of scientific evidence. It would take years for the average person to sift and winnow through each and every cell in this body of evidence in order for him /her to make an informed decision. If your personal physician determines that you have an illness and recommends a course of treatment, do you sift and winnow through the entire body of scientific evidence about that illness and about the recommended treatment before deciding whether to proceed? If your personal physician tells you that a specific treatment for your child’s illness is recommended by the American Academy of Pediatrics, do you challenge him/her to explain why he/she is deferring to a higher authority,
  22. Peter, the "peasants" didn't need an interpreter, but when they went off on their own, they still assumed the god of their ancestors existed. In other words, they carried their cultural assumptions with them as they went to try to understand the mind of god. This is precisely why many non-experts doubt anthropogenic global warming. Humans have never had such control over the Earth before, things are developing nicely for us, these guys over here say that some of these scientists are frauds, and everyone knows that sensationalism is the way to catch a buck these days. Business as usual. Not really a rapid shift in climate of the type that humans have rarely had to deal with (and certainly not in the historical period). I find it odd that you would characterize SkS as a "priesthood" site. It has comment streams. You can ask questions. You can go directly to the science itself. On this site, there are more direct links to the science than at any other climate science site on the net, IPCC included. This is, in fact, the best place to inform yourself. All we need are links to atmospheric science textbooks, but there are links to science of doom, which is about the same thing. Now consider sites like WUWT. These are the new priesthood you describe. The owners/mods and especially the news sites that are plugged into places like WUWT assume their audience is incapable of understanding the science. They post articles containing really basic errors, and then sit around while the comment stream cheers them on. They engage in rhetorical games like "climategate." The "climategate" allegations, never formalized, are wholly fraudulent, except for one claim (Jones being mean to Soon and Baliunas, but even then there's much, much more to the story). Yet these people knew that their allegations would be swallowed whole by their congregation. They depended on it. And that congregation did not disappoint. They bleated the news far and wide, never once actually checking the claims against what Jones and Mann (and the various independent investigations) had to say. No, people don't need interpreters. They believe they need interpreters--talk radio, CNN, Anthony Watts.
  23. Peter, I'd just like to point out that your opinion of the IPCC is based entirely on what other people have told you to think, based on their own opinions and misunderstandings.
  24. Why do you say 95% in the intermediate response, when the basic says 97%, and your sources (Doran 2009, Anderegg 2010) both say 97%? Please be consistent with the message. "around 95% of active climate researchers actively publishing climate papers endorse the consensus position"
  25. 97 is one good number but not so absolute as 100 of the theologians. They are 100 percent sure of god. And they are scientists too. All the same, their over confidence will not bring such a creature to real existence. (-snip-). According the data one real scientist only can decide that the information about climate is still scarce and there are many unknown components. (-snip-).
    Response:

    [DB] Please familiarize yourself with this site's Comments Policy; additionally, please read the Big Picture post.

    Finally, commenting at Skeptical Science works best if you first limit the scope of your comment to that of the thread on which you post your comment and then follow up on those threads to see what respondents have said in response to you. There are quite literally thousands of threads here at SkS; if you do not engage with the intent to enter into a dialogue to discuss the OPs of the threads on which you place comments, you invite moderation of your comments.

    Off-topic and ideology snipped.

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