Proponents of the idea of human-induced global warming often claim that there is an overwhelming consensus among scientists that such warming is a fact. For example, consider this recent article:
Consensus Confirmed: 97 Percent of Climate Papers Agree on Manmade Global Warming
by Brendan DeMelle, 22 June 2013 Huff Post Green
“A new survey conducted by a team of volunteers at Skeptical Science has definitively confirmed the scientific consensus in climate science literature — 97 percent of peer-reviewed papers agree that global warming is happening and human activities are responsible.
“It does not get any clearer than this. It should finally put to rest the claims of climate deniers that there is a scientific debate about global warming. Of course, this bunch isn’t known for being reasonable or susceptible to facts. But maybe the mainstream media outlets that have given deniers a megaphone will finally stop…”
The problem with grandiose statements such as the one above is that consensus is simply a collection of opinions, it is not scientific proof. In fact, when “consensus” is presented as “proof” then you can be sure that the presenters do not actually have verifiable proof. Instead they are merely practicing junk science.
And what about the opinions of those scientists who hold a minority view? Should their opinions be ignored because they have less votes than the majority? No, of course not. The role of true science is to determine which group is correct.
Science converges on the truth by requiring that scientists provide verifiable
evidence of a hypothesis, not by counting scientists’ votes for or against the hypothesis
Still not convinced? I agree that it may seem intuitive that scientists’ beliefs, as confirmed by a consensus of their peers, should be used to guide us when proof is not available. But this is just gambling; there have been numerous times throughout scientific history when the consensus of scientists has been completely wrong. For example, at one time the near-unanimous consensus of doctors was that it was perfectly fine to perform their work without first washing their hands: see “Advice From Professionals: Who Do You Trust? (Part 2).” (For other reasons to be cautious about allowing intuition to be our guide, see “Why Not Go With The Gut?“)
Bottom line: Those who promote “consensus” as being equivalent to a scientific proof do not understand how science works, and should be ignored.
-Ed Walker
View Ed Walker's profile
Engineering Thinking 
Andrew Jonathan Balmer
June 24, 2013 at 2:50 pm
Hmm, good that you picked up on a fallacy. There’s nothing i like would like to do more than to cull that sacred cow of environmentalism. The idea that truth (global warming) can be arrived at through consensus is downright silly.
But then you pull out two of your own..
1. “In fact, when “consensus” is presented as “proof” then you can be sure that the presenters do not actually have verifiable proof.”
I’m not sure there is logical connection between these two statements? Perhaps the presenter of an argument like this simply doesn’t realise they are making a fallacious statement? The fact that part of their argument is wrong doesn’t disprove the entire argument.
2. “There have been numerous times throughout scientific history when the consensus of scientists has been completely wrong.”
You seem to be making a similar argument to number 1, but this time saying Mr Smith (consensus) was wrong about X (hand washing), therefore he must be wrong about a completely unrelated topic Y (Global warming). Which is again not a logical argument. Mr Smith might be wrong or right about Y for a whole number of reasons, but not simply because he was wrong about X.
The fact is scientists believe climate change is occurring not because of consensus but because there is good empirical evidence to support it.
engineeringthinking
June 26, 2013 at 6:40 pm
Andrew, thanks for your comments.
Concerning your critique of my comment: “In fact, when “consensus” is presented as “proof” then you can be sure that the presenters do not actually have verifiable proof.”
I agree that the statement is too broad. It was written within the context of the earlier quoted comments by Brendan DeMellen, wherein it appears obvious that he is vigorously equating consensus with proof, but I did not make that clear.
Here’s what would have been better said:
“The problem with grandiose statements such as the one above is that consensus is simply a collection of opinions, it is not scientific proof. In fact, when “consensus” is presented as “proof,” as in the above example, then you can be sure that the presenters are merely practicing junk science, knowingly or unknowingly.”
Concerning your second critique of my statement: “There have been numerous times throughout scientific history when the consensus of scientists has been completely wrong.”
That is a correct statement. I made no connecting statement or inference in the related paragraph to global warming, as you imply I did. I was simply cautioning against the use of consensus, and intuition, on deciding any issue. Sorry if that was not clear.
Finally, you go on to say, “The fact is scientists believe climate change is occurring not because of consensus but because there is good empirical evidence to support it.”
You have made assertions without providing any supporting evidence. Therefore I am not sure what the intent of that comment was, other than to state your opinion, which is fine, but not necessarily convincing. From my readings, I would say that some qualified scientists believe man-made climate change is occurring and some qualified scientists do not.
In any event, I appreciate your constructive comments, and note that you have a blog that –like this one — strives to apply science to topical issues. (Note to readers: Andrew’s blog address is stated in error in his original comments; the correct address is quackscience.wordpress.com)
Andrew Jonathan Balmer
June 28, 2013 at 4:04 pm
Hi Ed,
I totally agree with virtually everything you said in the above comment. I might have used a slightly different phrasing for the first point but now i am being pedantic.
With regard to my last statement, you are right. Without me backing it up it isn’t much more than a throwaway comment at the end of the post. Sorry for that, climate change isn’t my specialty. What data I have seen would suggest it is occurring and man-made, but I would have to look into it a lot more to post my argument in support in full 🙂
Hope all is well, Andy