Posted by: climatewonk | March 29, 2008

Contentious consensus and other logical foibles

One of the denialist talking points is that there is no consensus among scientists that whatever warming is occurring is primarily or even remotely the result of human activities.  Go anywhere in the denialosphere and you will come across this over and over. 

So what exactly is a consensus? Does it mean that everyone agrees on some point? Does it mean that the majority (simple or otherwise) agree on the point in question? How many qualifies as a “consensus”?

The simple dictionary definition of consensus:

con·sen·sus /kənˈsɛnsəs/ Pronunciation Key – Show Spelled Pronunciation[kuhn-sen-suhs]

–noun, plural -sus·es.

1. majority of opinion: The consensus of the group was that they should meet twice a month.

2. general agreement or concord; harmony.


[Origin: 1850–55; < L, equiv. to consent(īre) to be in agreement, harmony (con- con- + sentīre to feel; cf. sense) + -tus suffix of v. action] Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.

So, it could mean “majority opinion” in which case it would be possible to contrive some poll or survey to see exactly what the “majority” believed on topic A. Of course, as with any survey or poll, the results are only as good as the methodology and research question.

If consensus means general agreement or concordance; harmony, if there is discord over an issue, such as whether global warming is real or if real, caused primarily by humans, there is no consensus according to definition 2. If there is discord, but it is on the part of a numerical minority, then the consensus can be said to exist as long as there is a majority in agreement.

When Schulte and others claim that there is no consensus among peer reviewed papers on AGW because a majority of research papers did not contain explicit statements in support of AGW, he is muddying the water, so to speak. A refusal to make an explicit statement — how does Schulte know that the authors refused to make such a statement? Perhaps none was warranted in the minds of the authors. The problem with all this counting of published peer reviewed papers on climate or global warming is this: a paper may not make an explicit statement about the cause of global warming, but its authors might still be in agreement with the statement that global warming is largely anthropogenic.

For example, many papers are published on the evolution of various species and traits, yet few if any would make an explicit statement endorsing evolutionary theory. There is no need, since there is a consensus on the matter.

This counting up of overt statements in the peer-reviewed literature is logically flawed. If one is really intent on confirming or denying the existence of a consensus, one should instead contact the authors of the papers and ask them directly.



  1. It’s amazing

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