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What Is a Consensus?

by Brian Dunning, Jan 03 2013

IMG_3741Anyone who has ever pointed out that a scientific consensus exists on a certain matter has probably been meet with laughter and derision. The word consensus has practically become a punchline. It is reminiscent of the famous corollary to Godwin’s Law which states that the first person to mention Nazis has automatically lost the argument; so it frequently goes with the first person to mention consensus. So many highly visible personalities deny and deride scientific consensus that the term has, in popular usage, become synonymous with a fatally weak argument.

A common criticism I hear of scientific consensus is “science should not be decided by a vote”. I agree. People making this argument are probably genuinely unaware that science-specific use of the word consensus differs from its common use. Of course, the scientific community does not ever gather in a secret conference and vote on the official scientific dogma of the day. That would make a cool 1984-style cautionary sci-fi story, but it doesn’t happen in real life. (Who would pay for all those flights, hotel rooms, and bar tabs?)

The way the word use differs is that in common use, a consensus merely means the general agreement of the majority. We all have a consensus that killing people is bad. Non-scientists also have a consensus on certain matters of science: gravity makes a ball drop, the Earth is globe shaped, sunburns are harmful. But for a scientific consensus to exist, it must be based on more than just personal opinions and observations of the majority; it must be based on results.

I found a dramatic example of this when I did my Skeptoid episode on left handedness. I found that the majority of research shows that left handers have shorter life expectancy. Now there are a lot of ways that the data can be analyzed, and a lot of possible explanations for this; and quite a few researchers disagree with that finding. However, I found that the scientific consensus shows left handers do indeed have shorter life expectancy. Not everyone agrees, but a clear majority do. This is based on the conclusions reached by many, many researchers over many, many studies. This consensus excludes Joe Blow like you and I, who have not done any such research. Ideally, it also excludes psychologists who may have strong opinions, but who have not performed or analyzed the research. Even though handedness is an active field of study that includes dissenting viewpoints, we currently have a scientific consensus that left handers have shorter life expectancy.

The obvious application of consensus in today’s political climate is global warming. A scientific consensus exists that shows anthropogenic global warming is a reality. This consensus is far stronger than the one I found pertaining to lefties; it is, in fact, virtually unanimous among professional climate researchers. But quite obviously, there is no common consensus about global warming. If we took a vote among the public, we’d essentially get a near-50/50 division along political party lines. This does not constitute a general agreement among a clear majority. However, the more we focused our study group toward people in scientific fields, the closer the common consensus would morph toward the scientific consensus. The scientific community at large would show a trend toward AGW as a reality, but it would include many dissenting voices, and could not really be called a scientific consensus. If we focus our group further to exclude scientists from non-climate fields, the scientific consensus would strengthen. Finally, if we limit our group to only those professional researchers with advanced degrees in climate science who actively work, publish, and review work specific to global climate, we find that the consensus is (very nearly) unanimous.*

So, simultaneously, there is no consensus on AGW, and there is strong consensus on AGW. It depends on whether you’re using the scientific meaning of the word consensus or not. Scientific consensus does not equate to a vote of the majority. It more closely represents the majority of the current published research.

Consensus does, of course, change as knowledge improves. It must change, or it is useless. Its whole value is that it represents the current state of our knowledge, to the best of our ability to determine it. When the fringe research turns out to be true, the results are repeated by others in the field and the consensus changes to represent it. Cold fusion failed to persuade other researchers who failed to replicate the results; and consensus did not change. The idea that HIV does not cause AIDS has also failed to move the consensus. However, scientific consensus does still actively change. It has recently changed to reflect that a type of bacteria, not stress or diet, is the cause of peptic ulcers; and even the Standard Model has had to have been updated recently to show that neutrinos have mass. Scientific consensus is an extraordinarily powerful tool.

By all rights, it should be the case that the first person to reveal the scientific consensus should win the argument. Because, really, whatever the current consensus is, is the first and last word on a scientific question for us people on the street — until the researchers working hard at changing it manage to do so.

* – The question of whether these authors and researchers are all paid stooges participating in a global conspiracy is an unrelated question. To change the scientific consensus, the brave patriots who turn down the Big Warming paychecks need to get publishing!

44 Responses to “What Is a Consensus?”

  1. Canman says:

    A scientific consensus exists that shows anthropogenic global warming is a reality.

    “Anthropogenic global warming” seems like a pretty nebulous concept. I don’t think Matt Ridley’s Agnus Miller lecture contradicts “anthropogenic global warming:

  2. Canman says:

    I also don’t think any particular field of science is immune to confirmation bias or above groupthink, or even overstating a problem. In this 15 minute YouTube video, Willis Eschenbach describes a paper he has had published on extinctions:

    • @blamer says:

      That word “immune” can mean exempt from (as in completely) or can mean merely “resistant to”.

      It’s rather trivial to point out that professionals make thinking errors.

      Any profoundness would be to suggest that respected science outfits are discouraging scientists away from (not encouraging them towards) the discoveries that reveal the cognitive mistakes of others. Such social-science findings I expect –if permitted by Science to be investigated– would need to be either futuristic happenings, or to be currently (self)censored out of reputable Science sources…perhaps naively or conspiratorially.

      However until such a profound social-science trend (re)emerges, then the prevailing wisdom within Science (but not all workplaces) is that THOSE professional reputations are actively & primarily regulated by demonstrating cognitive superiority.

      Thus, we can assume scientific consensus trends ARE “immune” (resistant) to credulous brains. Most human endeavors aren’t.

  3. Max says:

    Now isn’t that better than saying, “I don’t believe that you actually want to know that.”

  4. Max says:

    There’s a science of science called Scientometrics.

    Check out Sam Arbesman’s talk on the half-life of facts.

  5. Somite says:

    Specialties do have meetings where they meet and tough out issues for consensus. Scientists present their work to colleagues for sometimes brutal feedback. May include yelling.

  6. Donald Prothero says:

    Two recent polls, one taken just before the Nov. 6 election and one in late November, have shown that Americans are now about 75-80% in agreement with the idea that global climate change is real, not the 50/50 split that used to be quoted. Ironically, it was probably not listening to the scientific consensus (since there is so much misinformation and propaganda obscuring it out there), but the weather events of 2012 (the droughts and heat waves of the summer, followed by Superstorm Sandy) that seem to have tilted the balance. We keep reminding people that climate does not equal weather, but enough aberrant weather events year in and and year out do convince people…

  7. Somite says:

    “So, simultaneously, there is no consensus on AGW, and there is strong consensus on AGW. It depends on whether you’re using the scientific meaning of the word consensus or not.”

    If you are applying the word to a scientific concept like AGW you must use the scientific term. I would rephrase the previous sentence to “It depends on whether you are using the term correctly”.

  8. Chris Howard says:

    The people that I’ve encountered really don’t get scientific consensus, or many other scientific concepts. (I do live in Texas, and we have one of the worst educational systems in the country, so…)

    The best example given was at a philosophy dialogue at Texas State University. A psychology professor was discussing the current theories of personality. When asked about a particular theory, I think it was in relation to Bronfenbrenner, the professor said that he didn’t “…personally buy it, but it is the consensus…” and that he couldn’t rebut the evidence.

    He then spent a minute explaining what scientific consensus meant from a scientific perspective. Enough of the philosophy students were unaware that a scientist could disagree with the consensus, but would usually advance the consensus unless they had good scientific reason not to.

    This confused a lot of people in the room.

    • What a neat story. Good for him!

    • @blamer says:

      Hardly seems surprising that students were confused by a professor from another department ;)

      Hopefully the confused philosophy students were curious enough about science (philosophy of, and psychology) to seek a better understanding of “scientific consensus” via reputable sources.

      My quick flip through wikipedia reminded me that this professor mightn’t buy the theory or the paradigm or specific discoveries, etc etc. All rather deliciously confusing and curiosity stoking!

  9. Canman says:

    There’s certainly a consensus that increasing CO2 increasing temperature. Is there one on what the sensitivity is or on how cloud feedback works?

    • Somite says:

      Consensus usually refers to a high level conclusion that has implications to the whole field. I am sure climate scientists are working on what is the correct sensitivity and the effects of cloud feedback.

      When a climate scientist tells you that we need immediate action on climate you can be assured she and other in her field have taken account all possibilities. Anyone that is not a climate scientist would find it very difficult to find something that was overlooked unless they engage in research and publish it as well.

      • Canman says:

        If this climate scientist wants the world to make major changes in its economy because of her conclusions, she can expect a lot more scrutiny than if she was just proving whether dinosaurs were hot or cold blooded. Part of her job is explaining her conclusions, not hiding declines and dodging FOI requests.

      • @blamer says:

        Who doesn’t want the world to make major changes in its economy.

        If you’re interested in hiding and dodging, look towards those in control of the economy, not the worker bees.

      • Max says:

        It’s nice for scientists to explain the science to non-scientists, but non-scientists are still not qualified to tell whether the dumbed down explanations are right or wrong. To a layman, quantum physics may sound crazier than a perpetual motion machine. In the end, you go with the people you trust rather than the explanation that sounds more correct.

      • Sad but true, especially now that “America’s Doctor” is no longer Dean Edell but Mehmet Oz.

      • tmac57 says:

        Also sad but true Brian.
        I was telling a friend of mine why homeopathy was nonsense,when she said “That’s not true!!! Dr. Oz uses it!” I sighed and said “Dr Oz is a very poor source for reliable medical information,and seems to be becoming a quack.” She indignantly replied
        “Dr Oz is a VERY respected, legitimate Dr. with a
        good reputation!!!”
        This is what we are dealing with.

      • Max says:

        The evidence in favor of changes should be weighed against evidence in favor of the status quo.

      • laursaurus says:

        Dr Dean probably played the biggest role in my becoming the skeptic I am today. Loved his radio show! It seems like most skeptical programs are cynical and snarky. I only suffer through SGU when they feature a guest that I happen to like. I had almost given up on skeptical podcasts until I found Skeptoid. I remember an iTunes comment saying that it was definitely not like other skeptical podcasts and to give it a try. So I did and I loved it!
        Dean and Brian are upbeat, interesting, and humorous without being cynical. Sorry I don’t want to whine about some town in the middle of nowhere dealing with a kook who wants to start teaching Creation in science class. Jenny McCarthy’s body count doesn’t deserve regular updates. Enough about the tragic nutjob who prays instead of taking his kid to the doctor. That stuff deserves to be mentioned. But it’s not very entertaining to dwell on it when there are some really cool and fascinating topics to learn about instead. SGU’s worst crime was making a celebrity out of Rebecca Watson. Hey, thanks for that!

      • laursaurus says:

        ps. I support Skeptoid.

  10. Mikeb says:

    So there is this magnificent speech from someone who has changed his mind about genetically modified foods:

    In the comments section, someone says:

    “The problem is, consensus is a tool of politics. It has no role in science, none whatsoever. Scientific truth is not, ever, under any circumstances, decided by consensus. To argue on the basis of consensus is to argue on the basis of politics, and politics has no role in determining scientific truth either. What we get when politics is given a role is Lysenkoism, and a field of study stuffed sideways for decades.

    The only basis for argument in science is the data. If you can’t argue from the data then you have no argument at all. To argue on the basis of consensus is to argue from authority, and that is about as contra science as it gets.”

    Being a lay observer is hard.

    • tmac57 says:

      The unstated major premise there was that the consensus of scientists were not coming to that conclusion based ON the data.That was covertly asserted but not supported.
      And yes being a lay observer is hard.

      • Mikeb says:

        Yeah. My response to that blog comment was “Data doesn’t evaluate itself,” but he was having none of it.

  11. ed says:

    I thought a Consensus was essentially a religion aka a belief system.

    • laursaurus says:

      Consensus is a religion? Where is this People’s Church who vote on their objective theological doctrine? Do the clergymen who deliver the best homily or sermon become elected as Bishops? Funny how Jesus seemed to lose politically, yet rise to the level of Savior a few centuries after his execution.
      Or is it like saying atheism is a religion? According to SCOTUS it pretty much is.

  12. Seebs says:

    It’s important to distinguish between “consensus” as used in science and “consensus” as used in other fields. For instance, Quakers make a lot of decisions using a “consensus” process, by which they mean that a single very strongly-opinionated person thinking something is a bad idea is often sufficient reason to wait on it even though a hundred people think it’s a good idea. (This may sound crazy, but it suits the intended purpose quite well.)

    Might be useful to distinguish the terms more carefully in writing, simply because it’s so easy to misunderstand the term of art. I was only vaguely aware that “consensus” was being used in a slightly different way in science stuff…

  13. Canman says:

    This post by Roger Pielke Jr. about references to a paper of his being blocked by Jones and Trenberth in the IPCC AR4, undermines my faith in climate scientists:

  14. laursaurus says:

    The thing about AGW is that temp has increased by 1 degree C. If it went down by 1 degree then the consensus would be global cooling.

    The 2nd release of the Climategate emails weren’t as juicy as the first. But what they did reveal that the certainty claimed by the Prophet Al Gore was a wholly inaccurate picture.
    If Al Gore hadn’t misrepresented the science to indulge his bruised political ego and shore up his long-term investments, AGW would not have become a purely political issue. Did Progressives really expect that Conservatives weren’t going blindly accept the beating? Gore certainly took the opportunity to write political pot-shots at President Bush into the movie script for AIT. When it was communicated to the public as political science it was treated as such. Lord Monckton could not have become a celebrity if there were no Al Gore. No James Delingpole without George Monbiot. No Mark Moreno without Joe Romm. You can’t use turn science into a political club to beat your opponents and expect them to take it lying down. Al Gore corrupted this concept called the “scientific consensus” as much as The Skeptical Movement feels that AGW skeptics have bastardized their identity label. Sorry Brian! The rightful definition of scientific consensus has become political propaganda. After all, those who usurped its rhetorical power simultaneously Godwinned their political opponents as Deniers, akin to Holocaust Deniers. Let us not forget NYT Op-Ed columnists declaring that those who “denied” AGW must be tried and convicted in by the United Nations for “Crimes against Humanity”. Scary stuff considering the penalty is execution. Yes, questioning this “scientific consensus” ought to be punishable by death. Oh, you don’t want to die? Then pay off the 3rd world nations so they don’t need to build a carbon-emitting economy. Not sure how that would cool down the globe. According to the scientific consensus, that’s where the evidence points. Really? This is science? Because it sure isn’t supported by any economic consensus. You know, those people who work long and hard in their expert fields?
    Where do scientific ethics come into play? AGW has the real potential to scientifically justify inhumane tactics for the ultimate good of the masses. What would success look like? Will the overall global average temperature stay constant or cool down? How do we know Sandy, Wilma, and Katrina were due to AGW, but Andrew and Hugo weren’t? What if 1 degree warmer is better?

    • AmSci says:

      Global warming was politicized way before Al Gore. The personal attacks on scientists began no later than the eighties. Some recommended reading: “Merchants of Doubt” and “The Hockey Stick and the Climate Wars.”

  15. Janis says:

    The problem with global warming/climate change was demonstrated by the revelations of “Climategate.” The “scientists” at University of East Anglia were caught admitting in their emails that they didn’t use ALL available data to construct their COMPUTER climate models. How can you declare a trend in warmer temperatures if all data are not used. I personally do not buy climate change caused by humans. The sun’s activities are far more important to our climate. I believe climate change hysteria is mainly for the purpose of taking away civil liberties and there is plenty of evidence for that view.

  16. Janis says:

    I also refer you to the work of Dr. Tim Ball, who is a phd in Climatology and has studied the climate for more than 50 years. He scoffs at the idea of human caused global warming and says that it is an impossibility.