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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

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 751 to 800 out of 899:

  1. qwertie @749 & 750

    I disagree that we have to follow the framing of those who still deny the consensus and to then basically censor ourselves by no longer mentioning particular studies.

    As for the details from "Consensus on consensus", they are already just a click away and - at a guess - it wouldn't matter at all if that information were also included right within the rebuttal. They'd still ignore and/or twist it to their liking.

  2. After reading way to many pages of this threads, one thing is certain, too many people are simply going to believe what they want to believe.  To deny that there are legitimate arguments on both sides is dishonest simply dishonest.


    [DB] You are invited to pick the "legitimate argument" you feel the strongest about, and bring the citational evidence to support it, and post it on the most relevant thread here at SkS.

    [PS] You will do everyone a favour if you check your "legitimate argument" is not:

     - a strawman (ie check what science actually does say in eg IPCC WG1, rather than what someone tells you it says)

     - cherry picking data. The other common denier tactic.

    You might also like to run your argument against this list here. If you still think you have a good argument, then please comment on the appropriate thread. Given USA pull out of Paris, some good news would be welcome.

  3. True, CycleGeek @752, there are people who are so divorced from reality as to believe what they want to believe, in defiance of the actual state of affairs.

    If you yourself are not one of these people, then you will now (having read so many pages) be able to give a brief summary of the "legitimate arguments" against the existence of the scientific consensus.

    Reading this thread, and using the most strenuous skepticism, I have been unable to find any such "legitimate arguments" — so I very much look forward to being enlightened by your reply (assuming you can find any arguments that are not simply delusional and unrealistic as Monckton's ).

  4. A paper by five leading climatologists published in the journal Science and Education found only 41 out of the 11,944 published climate studies examined in Cook’s study explicitly stated mankind has caused most of the warming since 1950 — meaning the actual consensus is 0.3 percent, not 97%.


    [DB] In this venue, participants cite credible sources.  In this case, if you wish to cite a published study, then furnish a link to the actual study, and not to some news article that may or may not be misrepresenting the paper.

    Please read this venue's Comments Policy to familiarize yourself with this venue's permitted rules of engagement.  Thanks!

  5. Sorry, Rikoshaprl @754 , but the link you supply mentions the main "leading climatologist" as Richard Lindzen — an ex-climatologist who was so unscientific, that he caused major embarrassment to his colleagues at M.I.T. when he was there.  And the other climatologists your article (at yournewswire) links to, are little better!  Lindzen makes a triple fail, because his own climate predictions are now a full degree Celsius below the present day global surface temperature.   That is a colossal error by Lindzen.  And Lindzen still seems to think there has been hardly any warming, despite all the evidence to the contrary!  Lindzen is severely out of touch with reality.  And his third fail, is that he appears to hold a religious-based belief that Jehovah would prevent a global warming of more than the slightest amount.  Completely unscientific attitude there, as I am sure you must agree.  Among genuine climatologists, Lindzen is a laughing stock.

    Now to the Cook study itself.   Rikoshaprl, it appears you have not read the Cook paper.   If you had read it, then you would see that the second part of the paper consists of questioning the authors of those papers — and here, the authors themselves rate their own papers at around 97% support of the consensus figure found in the first section of the study [i.e. also 97%]

    Sorry, Rikoshaprl, but you haven't a leg to stand on.

    Perhaps you can inform us of how you came to make such a complete mistake of the real situation.   For your own benefit, you should do some reading about what is actually happening in the field of climate science — and you can learn a great deal, right here at Skepticalscience.

    Avoid foolish propaganda sites such as Yournewswire.  They will misinform you and lead you to embarrass yourself, hugely !!

  6. Just because there is consensus doesn't automatically mean that the view is correct. Historically, scientific consensus has not only been proven to be wrong, but spectacularly wrong...time and time again.


    [PS] This sloganeering without a  scrap of support. If you want to dispute, pick a point, back your argument with references/data. If you are taken in by the nonsense in link presented, then I strongly recommend you read here and here

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  7. The point is that scientific consensus can be wrong. Nobody disputes the following:

    • Prior to Einstein’s general theory of relativity, a magical “luminiferous aether” was considered by scientific consensus as the medium for the propagation of light. Einstein was actually still trying to work the aether into the theory of relativity as late as 1924. Evidence:
    • Prior to the 1970’s, the scientific consensus for macro geologic processes was not plate tectonics. Evidence:
    • Prior to the 1980’s, the scientific consensus was that there was no such thing as dark energy and dark matter. Scientific consensus was that we could see 100% of the matter and energy in the universe. We now understand that visible matter and energy represent only a small fraction of the matter and energy in the universe. Evidence:
    • Prior to the 1980’s, scientific consensus would tell you that sauropods lived in lakes and that dinosaurs were cold blooded and extinct. We now understand these things to be entirely false.

    The point is that simply pointing to scientific consensus is not fool-proof. I think this is a valuable input to the discussion.


    [PS] You are again indulging in the strawman arguments. Where is the claim that scientific consensus is foolproof?  The claim is:

    1/ There is a scientific consensus on the cause of current warming (and a very strong one at that)

    2/ That the scientific consensus (particularly when strong) is the rational basis for policy making (on any technical topic).

    Feel free to bring evidence against the claim but dont bother disputing non-claims.Take your sophistry elsewhere.

  8. Look, your argument is that anthropogenic causes are proved by scientific consensus. I have presented examples where scientific consensus was not just incorrect by exactly the opposite of what we know today. Although you deleted them. That's the only point. I happen to believe in the anthropotenic causes for cliimate change, but basing that upon scientific consensus is problematic. If you want to talk about logical fallacies, there you go.


    [PS] "Look, your argument is that anthropogenic causes are proved by scientific consensus. "

    No, as repeatedly said, that is not the argument and you repeating it does not make it so. Nothing is "proved" in science. What is asserted is that the vast weight of scientific evidence supports the notion of anthropogenic cause, so much so that a scientific consensus has formed on that. It might be wrong, but until someone shows evidence that it does, policy should be guided by that consensus. Show us anywhere in the IPCC report (or peer-reviewed paper) where it is claimed that anthropogenic warming is proved by consensus. That is a nonsense statement. The papers discussed above simply a methods to determine whether a consensus exists.

  9. I agree that scientific consensus is that climate change has anthropogenic causes. I think I was pretty clear about that.


    [PS] Great but didnt say you didnt. I am saying that you are making claim about that means that neither the article nor any scientific source actually makes. (ie a strawman).

  10. I am not going to make the argument again but post 712 sums it up splendidly. 

    TLDR: read the paper by Cook et al and you will see what the consensus is really about. Not that much shocking facts. Human activity is creating greenhouse gas and this impacts the global climate. 

    So basically I would advise any skeptic to read and think for themselves. Don't accept what is pre

  11. I can't edit, so I will rephrase that last sentence. 

    Don't just accept what is presented to you, think critical and challenge the assumptions. 

  12. Unfortunately many of the links have aged out in your "Scientific organizations endorsing the consensus" section. You might want to try updating them. Although good luck with the EPA these days...

  13. As this is your first post, Skeptical Science respectfully reminds you to pleIt  ase follow our comments policy. Thank You!

    It is one thing to establish Global Warming, it is quite another to reach fairly accurate conclusions or predictions concerning the effects.  Most projections I've seen mention a rise in sea level of maybe several inches over a 20 year period.  With that one scenario, don't you think that human ingenuity and engineering skills can meet the challenge?


    [PS] This post is offtopic. Any responses to it, put in appropriate thread and post only a link to it. To find an appropriate thread, use the search tool or look under arguments (eg taxomony, "its not bad").

    Also please cite your sources of information. Note for instance that Stern report for instance costed adaptation. The argument is that it is cheaper to get off fossil fuels than adapt. (I assume you are happy to pay for seawalls in areas affected by typhoons and monsoon river levels to pump, in countries that have contributed next to nothing to the problem.) Please respond on "its cheaper to adapt" thread.

  14. The laws of physics are not in dispute whereas those of geology are. The laws of physics apply to an infinite number of possible events at any time: geological theories state whether certain events occurred at certain times on this one planet. The laws of history are endlessly debatable. The laws about which there is the greatest certainty are capable of mathematical formulation: those about which there is least certainty are not.
    Is there a mathematical formula agreed by the 97% in the matter of global warming according to which the future can be predicted depending on stated variables? If so, what is it?

  15. Adrian White @764 , regarding "the laws of history" [your quote] ,

    Adrian, you appear to have a very strange and peculiar definition of the meaning of the word "laws".

    By failing to use English words in a standard English sense, you render your comments rather meaningless.   Please re-state (more intelligibly) the ideas you are trying to convey.

    (B) Question: Is there a mathematical formula agreed by 97% of biologists, which will describe & predict the processes of Evolution?   If so, what is it?   If not so — then we must presume that Evolution is false (and a form of Junk Science).

    We need better communication from you, please Adrian !

  16. Climate change is real and has very clear anthropogenic causes. Countless people have died due to smog and pollution, proven. It has a negative impact on the environment, proven. CFCs and other greenhouse gases created a hole in Antarctica's ozone layer, proven. Banning CFCs helped the ozone layer heal, proven. Just because oil conglomerates will lose billions switching to renewable energy and it's more expensive for them to observe emissions regulations while mass producing plastics doesn't mean the science behind industrialization changing our climate isn't true.

  17. How is anyone against what the scientists are saying against global warming? They're telling you to, you know, drive less, use less coal/petrol/other forms of fossil fuel, don't litter, recylce, etc. To me, it seems win-win either way and so far anyone who wants to disbelieve these scientists seem to be trying to justify themselves for their environmentally destructive behaviours. Let's give everyone a benefit of the doubt and use two hypotheses:

    a) Global warming is real.
     If it is real, then if you do all the things the scientists are saying, you'll be slowing down the process. Sweet, we get extra years, we don't have to experience such extreme weather conditions/changes, etc. Good for us.

    b) Global warming is a hoax.
     If it is fake, then if you do all the things the scientists are saying, you'll be cleaning up the planet. Sweet, we get a clean planet to live on. Good for us.

    So tell me, why is it so hard for you to accept global warming?? Do you only disagree because it seems like the "mainstream" thing to do and you want to seem "different"? I never understood this.

  18. Also, this article:

    David Archibald says "higher level of CO2 is better for all lifeforms on the Earth" - OK, well, can we trap him in a room that only has CO2 in it and see how much he benefits from it? I would love to watch that. For scientific purposes.
    CO2 is a waste material for any species that requires cellular respiration - and, uh, there are heaps of species like this out there. Tell me you at least know this. In case you didn't pay attention in Biology classes in high school, the waste products of cellular respiration is H2O and CO2. That's why you have to breathe out and pee. Bottom line: humans, as well as many lifeforms that are not plants, do not benefit from high CO2 level. Who benefits from the waste products?

    He says "lucky for us, the relationship between CO2 level and temperature is logarithmic, not arithmetic" - buddy, a logarithmic relationship increases faster than arithmetic. This is where you lost all credibility. You can't even tell the difference between the two and claim to know "science".

    Lastly, our good old David is also a CEO of an oil company in Australia. You know why he keeps claiming there's no global warming? It's cos he's losing money if you believe the facts. Wake up.

  19. I can't edit my comment there, but @767, I meant "How is anyone against what the scientists are recommending against global warming".

    I sincerely believe that global warming is real.

  20. As this is your first post, Skeptical Science respectfully reminds you to please follow our comments policy. Thank You!

    Found this forum on a link posted on a POW(Protect our Winters) EM article I recieved. I consider myself an open minded person and willing to listen to many points of view and draw my own conclusions from the facts presented, regardless of my personal opinions.  My views have changed on several things over the years.  Winston Churchhill, hardly a scientist but certianly one of the biggest influencers on the course of 20th century history, once said that "if you are not a liberal in your twenties you have no heart, and if you are not a conservetive in your forties you have no brain."

    The heart creates passion, and passion emotionalizes arguements, obscuring the validity of points of contention.  One of the obscured points is the method that one of the cited studies was conducted, the Doran study, conducted by Margeret R.K. Zimmerman, as a grad student under Doran's direction.  Points that make you go huh?... 10,257 surveys were sent out. 3,146 bothered to respond.  Does that mean 7,111 questionaires were not delivered? Or that the intended recipients had no opinions, yea or nay? Only 30%, give or take, bothered to respond. Only 79 respondents answers were eventually used to come up with the 97%- the other responses supposedly did not come from "climate scientists" so they were not used.  Why were they even sent?  There are other questions that arise from the conclusions that were drawn from this study but I think the point is made.  When any survey requires closed answers the results must be considered with a skeptical eye.

    Facts are not arrived at by consensus.  If this were true, the earth would still be flat, and Giordano Bruno's burning by the Vatican Inquisition in defense of geocentrism would be justifiable. Aristotle's expansion on spontaneous generation were accepted as fact for over 2,000 years! Neaderthals are not ancestral to modern man! Micheal Bradley's assertation of Neanderthalic genitics in "The Iceman Inheritance" was laughed at and later decried as racist. Indeed, the scientific community's persecution of any one who questions the dogma of the alarmists who have made substantial financial gains espousing the global warming/end of the world would be entirely defensible.  One of Micheal E. Manns (the hockey stick guy) claims in the defamation lawsuit against Mark Styen,et al., was that it is (or should be) a crime to defame a Nobel Prize winner.  Of course he is not, and it is not.  This claim was dismissed from the suit. The financial gains to be garnered by silencing any thought contrary to the prevailing AGW theocratic dogma is too great to be allowed a voice.  This site has poo-poo'ed Judith Curry and some of her claims, but I have found more open minded and even handed writings on her site, on both sides of the issue. Humankind thinks that they are of gret consequence but the truth is we are like all other afflictions this globe has suffered, and when she tires of us she will shake us off like raindrops and without a second thought.

  21. Windrunner @770 , welcome (back) to SkepticalScience !

    If you have come to defend Dr Judith Curry's reputation as a scientist, then alas you come too late.  That ship has sailed.

    If you have come to argue that the climate scientist consensus on AGW is anything less than 99%, then alas you come 30 years too late.  The consensus has been steadily rising for many years now, and has reached 100% (or more precisely:  100% minus a few crackpots, who are entirely unable to provide any valid contrarian scientific reasoning or supportive facts).

    In addition, your "Churchillian" quote is wrongly ascribed.  There have been many versions of it -— the Twenty-First Century version is:  "If you are not a liberal in your twenties you have no heart, and if you are not a conservative in your forties you have no brain, and if you are not an environmentalist by your sixties then you have no conscience."

  22. "Facts are not arrived at by consensus"

    This is a very tiresome strawman argument. We agree. However, the important facts are: a/ the consensus does exist and b/ scientific consensus (especially when strong), is the best guide to policy.  A true scientific consensus is very seldom wrong and you would be an idiot to bet the planet on it being wrong.

    Citing pre-scientific examples of societial consensus (a very different thing) is pointless. 

    "One of Micheal E. Manns (the hockey stick guy) claims in the defamation lawsuit against Mark Styen,et al., was that it is (or should be) a crime to defame a Nobel Prize winner." Citation please. What were his actual words?

  23. I agree with the consensus research. But I want to address something to those who don't believe it. That is: is there NO CHANCE that these scientists are correct? As in zero? It's hard for me to accept that a thinking person could rule out the possibility unilaterally.

    So let's assume for argument's sake that there is some chance these scientists are right, and that climate change is as real and dangerous as they say. Maybe not even a 50% chance. Maybe just a 20% chance.

    Now put a single bullet in your 5-chamber revolver, spin the cylinder, point it at your child's head, and pull the trigger. Why not? There's only a 20% chance it will go off, and an 80% chance it won't. But of course no reeasonable person would do that because the consequences of being wrong are unthinkable.

    I would argue that climate change isn't that different. Already, low-lying countries like the Maldives and Bangladesh are losing real estate. Already ski areas in the U.S. are going out of business because winters are warmer. Some lakes have dried up completely. Thousands of square miles of ponderosa pine are dead in the southwest because winters are no longer cold enough to kill the bark beetle. Hundreds of American kids are getting sick because the Lone Star tick is no longer confined to the deep south, but has been found as far north as the Canadian border, bringing with it five diseases and an allergy to mammal meat. And this is just the beginning. Are we ready for NYC to be under water in 40 years? For our farmland to become desert? For wars over drinking water? (Those crazy liberals at the Pentagon are preparing for climate change, check ut their published studies. Maybe we should be preparing, or better yet preventing, too.)

    I happen to believe the scientists are right. But even if you don't, can you reasonably argue that there's no possibility you're wrong?

  24. A scientific consensus does not make a theory correct and it certainly does not rule out the existance of an alternative theory which better explains observations. More importantly, no scientist has made such a claim - it is a deniers favourite straw man arguement.

    The important thing about a scientific consensus it that it is the only rational basis for policy decisions, especially when it is strong. Betting on say a 20% chance of scientists being wrong is a bad bet especially when consequences for getting it wrong are terrible. The research into the consensus was to determine the strength of consensus and lay to rest the unsupported assertion by deniers that there was no consensus.

  25. The 97% mantra is debunked in this empirical analysis, including some rebuttals by actual scientists cited in the 97% claim who say their assessments were misrepresented.

    Any responses to clear up this speed bump would be appreciated.

  26. Richard Tol accidentally confirmed the 97% global warming consensus. An "own-goal" if there ever was one.

    There is no doubt in my mind that the literature on climate change overwhelmingly supports the hypothesis that climate change is caused by humans. I have very little reason to doubt that the consensus is indeed correct.

    Own Goal

    LINK 1




  27. realelybritt, you should have followed the link included in the paper you referred. All this is old news. Cook et al published a response to Tol 2014, here are the highlights:

    T14′s consensus value is based on a math error that manufactures ~300 nonexistent rejection papers.

    •T14 infers data drift using an inappropriate statistic that poorly correlates with consensus.

    •Analysis of appropriate consensus statistics reveals no significant data drift.

    •T14 wrongly conflates abstract ratings and author self-ratings; differences are detailed in C13.

    •Re-analysis without T14′s errors confirms 97±1% consensus on AGW

  28. Both sides of this argument seem to be exagerating their own subjective evidence and the weight of support for their views. This indicates a lack of real certainty. It seems also that many on both sides have a vested interest. In the majority of scientific experiments, before a conclusion can be drawn there needs to be a control. There is no 2nd planet Earth without man made co2 to make an accurate comparison of climate change. Therefore, even if the 97% consensus claim is true, it can hardly be considered credible.


    [PS] Sloganeering. please provide evidence to support your assertion that science is exagerating subjective evidence. Your claim that science has some kind of vested interest is verging on a conspiracy theory. Vast areas of science do not work the way you suppose (eg geology) so it would be better to learn how the scientific method actually works. In essence, you predict the outcome of an observation from known physics, make the observation and compare to prediction. This is been done in countless ways to build modern climate theory.

    Nothing is certain in science - but a scientific consensus, particularly when strong is the only rational basis for policy.

  29. How many of those identified by Cook through his unscientific interpretaion have been approached to confirm their views on anthropogenic climate change? I suspect that would sink his dodgy statistics once and for all. 


    [JH] Inflammatory sloganeering striked through. Inflammatory tone and sloganeering are both prohibited by the SkS Comments Policy.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  30. Foundusually @779 : Quite evidently you have no understanding of the scientific consensus, and have not managed to read the award-winning Cook et al 2013 paper (where your question is answered).

    Please educate yourself.

  31. I have come across a climate denier who makes statements such as:

    It is difficult to know what exactly is the scientific consensus on the predictions about the effects of climate change in the future.

    I have read estimates that the global sea level is expected to rise anywhere from 6 inches to 6 feet by the year 2100.

    What I am looking for is a consensus among climate scientists about the specific effects of climate change in the coming several decades.

    I'm sure there is a souce here on Skeptical Science if someone could kindly point me to it.

  32. Sea level rise estimates are largely based on the future emissions concentration pathways that we would need a crystal ball to foresee.  Hence the estimates are dependant on those future decisions society makes.  And those decisions matter a very great deal to future SLR by 2100.

    Per the NCA4, Volume 1, Chapter 12, Table 12.1:

    Table 12.1, NCA4, Volume 1


    For reference, we are currently following RCP 6.0 pathways, so I would look at the Intermediate-High set of values.


  33. @ 782 Daniel,

    Thanks so very much that's a great resource!

  34. "that's a great resource!"

    The best part about using it on a denier is that you can tell him that the information was released by the Trump Administration...I never fail to remind them of that.

  35. While I do believe there's sufficient consensus, I'd like to see the following considerations addressed. I'm pretty sure it's nothing new, but still it's not something widely discussed in popular science media, so any hints appreciated. 

    1. "Attractor" theory - since CO2 AGW is the predominant one, other alternative theories may not receive the attention and resources thay may potentially deserve, resulting in low number of papers, etc. 

    2. Peer influence - putting pseudoscience outliners aside, I find it plausible those wit mildly dissenting views will feel some pressure to conform to the level they wouldn't if the topic wasn't so controversial. 

    So again, I fully agree there's strong consensus and believe AGW is almost certainly real, methodologically when determining the level of consensus, the above two variables need to be controlled for. I'm just not sure if & how it was done. 

  36. Pl @785 ,

    1. The original "attractor" theory (held up until the 1930's) was that the Earth's climate was self-correcting i.e. homeostatic within narrow limits.  But that was disproven, as experimental & observational & paleo-climatic evidence mounted up.  Satellite-based evidence has re-inforced that, too.

    2. "Peer influence" is not a problem ~ because genuine scientists have a natural tendency to be contrarian & genuinely skeptical.

    The consensus is pretty much unanimous for climatologists, because nowadays (unlike 50 or 100 years ago) the evidence for "CO2/AGW" is conclusive.  There are no longer any "alternative theories" that hold any validity ~ the plausible alternative have been disproven (e.g. GW from variation in cosmic ray intensity; homeostatic cloud formation as an "Iris Effect"; long-cycle ocean current effects).

    If you take time to learn more about the mechanisms influencing global climate, you will recognize that the (mere handful of) "dissenting" climatologists are offering only empty dissent . . . because they have nothing valid to back up their dissent.   They are just running on automatic . . . such as the well-known retired Professor Lindzen, who has an Old Testament religious belief that the Earth has been designed to remain close to the Garden of Eden climate status.  A few others suffer from extremist political beliefs, motivating them to cherry-pick / ignore the plain evidence.

    Please note that the respected scientific journals welcome dissenting views provided that there is reasonable supportive evidence.  (Journals and scientists gain prestige & fame by demonstrating valid contrarian evidence.)  

    But alas, every contrarian idea has failed the validity test, and there are extremely strong reasons why no "undiscovered" factor exists.

  37. Eclectic @786, 

    My comment was mainly about the method of determining the level of consensus. 

    Point 1 ("attractor" theory) addressed my assumption, that the method includes statistics about numbers of articles - which can be strongly biased by such "attractor". If there was another attractor in rather distant past, it has little to do with this argument. However, I also assume that such bias may have been controlled for - I'm simply asking for brief explanation how. 

    Point 2 (peer influence) - I know in the ideal world, scientists have such characteristics as you claim, in real world they often follow direction or advice of their more senior peers, topics are to significant extent determined by projects / programs, etc. Again, I'm not saying this is a big issue, but it's most likely not totally negligible either. I'm interested in how such bias was / would be addressed when determining the level of consensus. 

    On a related note - a foot soldier of science may find it more productive to focus on particulars rather than spending time questioning consensual claims. I'm probably not the only one seeing a bit of positive feedback loop in there. 

    Regarding lack of valid alternative theories - I fully agree. There are softer claims than that though - "the field is young, it's not established science yet, the link to human activity is not conclusive yet" and similar. Only miniscule part of general public is able to determine that themselves, so I find preaching the importance of scientific consensus probably the most effective way. I.e. the arguments for it (specific consensus and it's level in climate science) better be airtight. Therefore my original comment. 

  38. Pl @787 ,

    of course you are quite correct that there are institutional pressures towards conformity.   As well as the genetically-inherited tendency of humans to "team up" in a tribal manner : just witness the current mindless tribalism in political matters ~ "full steam ahead and damn the facts!"   ;-)

    But your question suggests you are insufficiently aware of the drive towards contrarianism by scientists as individuals.   The up-and-coming scientist seeks not money, but reputation / respect / fame / prestige.  Yes, a Nobel Prize may well be awarded in 10 years' time or more . . . but scientific acclaim this year is a powerful inducement for publishing clever / innovative / iconoclastic work.  And the competition is fierce !

    Similarly, there is no shortage of respected journals that are ready & willing to publish novel dissenting papers (always provided the ideas have some reasonable evidentiary backing . . . and are not just fruitcake speculation.)   A journal gains in prestige by being the first to publish groundbreaking work.

    Between the scores of journals and the 10,000+ climate-related scientists, there is really nothing for you to fear that any worthy contrarian idea will be suppressed.

    Yes, there are a few real scientists who speak against the mainstream climate science, but they have no actual evidence to back up their viewpoint ~ and if you look more closely at them, you find a sorry collection of crackpots / religious nutcases / political extremists / and a few aging "emeritus" types (even a rare Nobel Laureate) whose maverick-inclined personalities have become warped by the early changes of senility.  [  I myself know a once-respected researcher, PhD equipped etc, who is a member in good standing of a local branch of the Flat Earth Society.]

    But let's not get bogged down in Ad Homs ~ however apt & amusing.   The basic problem is that the climate contrarians are still fighting last century's battles ~ and they have no facts to support themselves.

    All they can muster is rhetoric & the unjustified "soft claims" you mention . . . in their attempt to sway the susceptible.


    ( btw, since the consensus of climate experts is extremely close to the 100% mark, I am wondering what you can mean by "the method of determining the level of consensus".  What can you be thinking of ? )

  39. Eclectic @786,

    I think you made some of these points above already, you are somehow overstating my claims, I think my two points are more subtle in their supposed effect. 

    To be clear, I like playing devil's advocate more than preaching to the choir, so you can take that context into account when responding. 

    Re motivation of scientists - that's probably more complex, my guess would be that the primary driving factor is usually interest in the topic and natural curiosity, so not necessarily fame and pursuing contrarian views. But this is a bit off topic, so I'll leave it at that. 

    Let me focus on your last question - what do I think of when writing "the method of determineng the level of consensus":

    I've skimmed through one of the papers linked above, you can see they are discussing such methods in length. They don't seem to address the two points I made above (attractor theory and peer influence), unless I missed it in the text. 

    Stamping a specific number with % sign to a consensus is non-trivial task. For example, processing abstracts using some simplistic method may potentially skew the result a lot, so I would personally prefer surveying scientists, allowing non-binary response, weighting the data by their level of expertise in the field and ability to critically think... - which would be very difficult, if not impossible to pull off. 

    Therefore my question(s) in first comment I made. The paper I linked to don't seem to address that and I'm lazy to study all consensus survey papers on my own, so I was hoping someone who knows the answers may chime in. 


  40. Pl @789 ,

    I would certainly not wish to overstate your claims.

    At the same time, it would be best if you clarified your claims far more precisely than you have in post #789 and prior.   Otherwise, we are mutually tackling a Hydra-headed creature called a consensus, and doing so in an uncoordinated manner.

    From my position as somewhat of a "naive realist", the primary meaning of (climate) consensus is in the basic sense of : the scientific consensus of our modern knowledge of climate physics.   In other words, the current understanding of the science (of climate).   In essence, the science is found in the (summation of) scientific papers published in reputable peer-reviewed scientific journals.   Twas ever thus !

    That is why a number of studies (including the very clever Cook et al., 2013 with its notorious 97% ) have looked at what is found in the many thousands of published papers.   BTW, the Cook study was outstandingly excellent, because it cross-checked its findings by asking the actual authors what they considered their own papers showed.  And yet it is important to remember that the Cook paper of 2013 was centered on a median paper "age" of approximately 2005 date ~ and the "consensus" has moved on by a considerable amount in the 12+ years since then.

    Some other studies were even older than that.

    However, it is even more important to remember that the scientific consensus (on climate matters) is the science itself ~ and that it is not a vote or a percentage or an opinion poll.   (As you yourself have implied, we can easily end up in a futile tangle of shades of definition, if we are merely assessing "opinions" by scientists of all stripes.)

    A survey of opinions is only a proxy of the scientific consensus.   Taking a vox pop of scientists shows (as we would expect!) that "the level of consensus correlates with expertise in climate science" [Cook et al., 2013].   Obviously here, Cook is using consensus in its loose meaning of "opinion".   It is understandable that the non-scientists & politicians of this world would have a desire to deal with a brief proxy of the complex science of climate ~ and a "percentage consensus" is a handy first approximation.   But it is only a proxy, and we should never mistake it for the underlying science.

    As your linked 2016 reference (to the IPCC) states: "human influence has been the dominant cause of the observed warming since the mid-20th century."   That is a fair summation, though expressed in an overly-conservative manner.   And - as you yourself say - "stamping a specific number with % sign to a consensus is [a] non-trivial task".   To which I would add: it is both non-trivial and essentially irrelevant.

  41. I'm going to be blunt here, and I hope that this doesn't cross any moderation lines. The voices that most loudly and most often deny climate science seem (in my very personal opinion!) to fall into four categories, often several at once.

    Lobbyists, loons, ideologues, and opportunists.

    Such people show up repeatedly in the few surveyed papers objecting to climate science consensus, often cross-referencing other deniers or just themselves. 

    Lobbyists are self-evident; often residing in 'think tanks' that receive business funding. Loons hold obviously counter-factual positions, ignoring the majority of data in deference to their pet theories. Ideologues include for example libertarians, Randian capitalists, and others who object to climate science because they view any response to climate change as increasing the role of governments - not an objection to the science, but rather to the correction methods implied. That also includes teleological religious types who feel that the world was made for us to use, or who think a Rapture is imminent and why bother with the ecology. Opportunists are simply folks who find it more personally profitable/rewarding to object to climate science, rather than pursue more mainstream (and factually based) approaches - the average scientist doesn't get invited to travel around the world, or provide frequent Congressional testimony. 

    There's just no hard science making sustainable objections to the consensus climate views. None that I've seen, at least, and I've been looking. I won't name names WRT the preceding classifications, but I think that most people following the 'debate' can find a few loud climate deniers who fall into one or more of those categories. 

    I would gladly read anything with a scientific basis that supportably points out issues with the climate consensus - it's not a joyful outlook, sad to say. But I just haven't seen anything that holds up to examination. 

  42. Quite agree, KR @791 . . . and longish post follows.

    There are probably rather more than four categories of denialist . . . but the madness/badness of the human psyche is so commonplace, that it would be tiresome for you (or anyone) to allocate further mental effort to refine categories beyond your four !

    As you say, KR, science-deniers (and here I include some well-educated scientists who nevertheless deny climate science directly or indirectly) have a tendency to occupy more than one category.

    Perhaps they start off in a single category, and then some amplification or or positive feedback process causes them to swell and overflow into neighbouring categories?   Do you know of any psychological study which quantifies the TCLS (Transient Climate Lunacy Sensitivity = number of years until Climate Lunacy has doubled in an individual denialist) . . . or quantifies the ECLS (Equilibrium Climate Lunacy Sensitivity) ??     Though I suspect that the ECLS is a difficult matter to quantify, because ECL is only reached at the moment of death.

    If I am permitted to name names which fit primarily into your fourth category, it would be easy to pick Richard L and Judith C ~ being scientists who in earlier decades have made some contribution to climate science, but whose contribution history has been more ordinary than illustrious.   Yet they are only human, and doubtless enjoy the perks & celebrity status awarded by the general denialist community (who have a desperately thin field of champions to choose from).

    Now a "Fourther" who has puzzled me is Dr Koonin ~ does he justify a fifth category, or is it merely a case of "opportunism"?   Perhaps he suffers from LDS (Limelight Deprivation Syndrome) as he moves out of public life . . . but then again, LDS would also explain some of the motivation of emeritus professors & other retirees who occupy category 4.

    Returning more closely on topic : we have the multi-category award winner Mr Monckton.   Lord M has been lauded by (Mr Watts and his cronies at) WUWT website, for his innumerate [in both meanings!] and strenuous denunciations of the consensus demonstrated by Cook et al., 2013.

    Now, at various times I have touted the excellent Youtube video series produced by science journalist Potholer54 on climate matters & climate myth debunking.   In particular, Potholer has an amusing 5-part video exposure of the mendacity of Lord M.   (Look for "Monckton Bunkum".)   And I gather that Potholer also posted on WUWT, to show the utter falsity of Lord M's positions & calculations (especially regarding Consensus figures) . . . and before very long, Mr Watt banned & expunged Potholer from the website.   I did not witness these events ~ but I know that Potholer makes a point of always being civil or showing icy politeness.   So it seems Mr Watts was infuriated by the relentless logic provide by Potholer . . . and Lord M's denunciations of Consensus are still extant on WUWT (or were so, last time I looked).

  43. Eclectic @790,

    "Consensus" can mean either the proposition itself, or the fact that there's an agreement. For me, the former is rather clear ("AGW is a thing"), the quantification of the latter is what I'm commenting.

    The paper I was linking to is also "Cook et al", but from 2016, so perhaps an updated and upgraded version.

    Where our views may differ is your last sentence, where you consider measure of consensus "essentially irrelevant". I may agree that it is not absolutely essential in case of AGW, where it's rather obvious that a widespread consensus exists. I still think it is relevant, especially as questioning the consensus is one of the lines of attack from deniers.

    Generally speaking, measuring consensus as a concept of skeptical thinking is also very relevant, but I think it's pretty obvious.

    So circling back to my original comment, I still don't see couple of variables influencing the measure (I have given two examples) being addressed.

    In addition to the two examples, there'd be more. I already alluded to natural non-binary nature of scientific claims. Skimming through the Cook 2016 article, I also didn't find it explicitly addressed. We would probably agree that it's something completely different to claim "90+% of scientists agree, that the probability of AGW is above x" when the x is 50% compared to say x=99%.

  44. Pl @793 ,

    < "Consensus" can mean either the proposition itself, or the fact that there's an agreement. For me, the former is rather clear ("AGW is a thing"), the quantification of the latter is what I'm commenting. >  unquote .

    "Consensus" is potentially a very large Venn Circle indeed, and we would do well to define it more closely and pragmatically.  (Semantic confusion can easily be a Black Hole that swallows up any effectual discussion.)

    "AGW is a thing" is far from correct.   AGW is much more than "a thing" in the colloquial sense ~ AGW is a physical reality.   Likewise, choosing to label the Consensus as a proposition, is a choice of even more nebulous terminology.

    As I mentioned in an earlier post, for climate purposes Consensus is essentially a term for the established science.   (There have been rare occasions when the established non-climate science has been overthrown or enormously modified - think Newtonian/Einsteinian physics of motion - but the established climate science is the product of a century of work by countless thousands of modern scientists, not the work of a single English genius in the 17th Century . . . and the chance of the mainstream climate science being seriously overthrown by startling new insights, is such a vanishingly small chance, as to be ridiculously fanciful.



    In looser terminology, "Consensus" is often used in climate matters as a type of numerical proxy for the scientific position.   It is this latter meaning which gives rise to public confusion/uncertainty about the actual underlying science (a confusion magnified by numerous propagandists who injected much deliberate obfuscation).

    The purpose of the Cook et al., 2013 study was to achieve an improvement over earlier studies/surveys : to achieve a more definitive figure for the numerical consensus, and to greatly reduce the scope for any [as you yourself quote:] "lines of attack from deniers".   The Cook study was very clever  - and award-winning -  and produced the very widely cited 97% figure, which has become notorious (and which has become infuriating & nauseating, to all the science-deniers).

    As might be expected, the denialists' fury has resulted in massive eruptions of Motivated Reasoning.   The gigantic brain of Lord Monckton (and cronies) has produced very "creative accounting" which has variously redefined the Cook 97% figure down to 33% or 13% or 4% or similar absurd figures.   Yet that's hardly surprising, coming from intellects which are in full denial about the physical properties of CO2.

    As I mentioned earlier, the 2013 Cook study is now quite dated ~ centered on approximately 2005.   More modern studies [e.g. 2014] show a consensus well above 99%.   And more importantly, the "contrarians" have still produced nothing valid in the way of support for their skepticism.   Nothing at all.

    Pl , the 2016 link you gave earlier (to Cook and other consensus investigators) is merely a meta-analysis.



    "Circling back" to your original comments ~ Pl , I had hoped I had already answered your "two examples" ; answered them directly as well as en passant.   If that is not so (in your own mind), then perhaps I have not expressed myself clearly enough.   Or perhaps you are doubling-down on your "Devil's Advocacy".   Either way, you will need to state your objections in a far more precise & thorough manner.

    At the same time, you might care to expand on the "non-binary nature" you mentioned ~ although once you have eliminated the obscurity, it might well be that we find it rather off-topic for this thread.

  45. "A couple of variables." Who cares? Splitting hair about the consensus is likely the least useful way one could spend time on climate change (except for reading WUWT perhaps). Anyone with a functioning brain and some critical thinking skills looking at the science will quickly see where the weight of the evidence resides. There are now some much more pressing imperatives than quantifying and/or qualifying the consensus. The lack of scientific consensus is just another defunct lie from deniers. The rest is details, of truly little interest.

  46. Eclectic @794, 

    first, you must excuse some inaccuracy in my text, English is not my strongest skill. By "AGW is a thing" as a simplified statement of the consensus proposition I simply mean "GW is happening and human influence on it is significant" - or similar statement where I don't expect any disagreement. 

    You did not address my original points though - you expressed your view and opinions - which BTW I don't have many reasons to disagree with - but what I was looking for was to see, how these variables (and maybe I added another one in later comments) were controlled for in studies establishing the level of consensus - I haven't seen that in the study I linked to, nor in the comments. 

    Also, I wouldn't call it "objections" - I'm simply interested in some details of the "consensus measurement" methodology. 

    Regarding the "non-binary nature", it's rather trivial, see final paragraph of @793. No true scientist can claim something with absolute 100% confidence, despite human brains have tendency to use such heuristic. It's not an off-topic here, because - let me quote myself: We would probably agree that it's something completely different to claim "90+% of scientists agree, that the probability of AGW is above x" when the x is 50% compared to say x=99%.

  47. Philippe Chantreau @795, 

    assuming you are commenting my "nitpicking" here. I believe I already stated I don't consider these considerations critical to the actual topic of AGW and I don't claim it has high priority on any related to-do list. However, I also consider the question how a consensus in measured and how the resulting "numerical level" is adjusted for apparent systemic biases to be relevant - both in general (as some kind of methodological best practice, regardless of the field) and also in the field of climate science, if not for anything else, at least to prevent possible attacks from deniers. I'm afraid people waste time on many less useful things than that. 

  48. Philippe Chantreau is quite correct that the question of the Consensus has become trivial and largely irrelevant.   The science (of AGW) is settled enough for practical purposes [the practical purposes being the political policies for dealing with the climate situation].   And the "numerical consensus" is well over 99% and climbing ever closer to 100%.

    Nevertheless, this thread here stays open for those who wish to split hairs about what are nowadays irrelevant trivialities.    ;-)

    Pl , you are correct in stating that AGW is "a thing" in the sense of a reality.   But the "A Thing" phrase is so widely applied to all sorts of abstract concepts & ephemeral fashions, that it becomes quite ambiguous and unhelpful in our discussion here.

    The surveys assessing the state of the (climate) science show that the (scientific) consensus, as measured by the published scientific papers in recent years, is in effect 100%.   Over the years, there's been a tiny (and reducing) number of "contrarian" papers ~ and these papers have been mutually contradictory in their expressed concepts, and have utterly failed to present any valid evidence to support themselves.

    In the far looser terminology of the Consensus in the form of an opinion poll of scientists . . . surely the only worthwhile poll can be made of scientists who are well-informed on climate science and who have definite expertise in this field.

    Even rather old studies [such as the Cook 2013 study] show that the greater the climate expertise of the scientists, the closer to 100% is their "consensus of opinion".

    And surely the whole concept of numerical consensus loses any useful meaning if the assessments include more and more of the ill-informed and the deliberately ignorant.   Surely there can be no real value in a consensus that includes the opinions of blowpipe-toting hunters in the upper Orinoco River or iPhone-toting hipsters in the upper Missouri River.


    Pl , the "non-binary" question you mention, is one that has been much discussed in years past.   This, and your "original points", are all examples of imprecision of expression; and I must yet again beg you to clarify what you are driving at.


  49. The truth is not found thru a vote, just ask Ptolemy ;-)

  50. As been stated many time here, the point of consensus studies is to counter myth that consensus doesnt exist.

    The Scientific consensus might be wrong but it is the only basis for rational policy especially when it is strong.

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