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The level of debate on global warming is shriekingly poor. Not that I have any hope of convincing the world to reject bad logic, but here are some of the more common fallacies making the rounds.

  1. The Consensus Appealing to “the” consensus is a form of the appeal-to-authority fallacy, but it is more so a stacking-the-deck fallacy. It works thusly: the IPCC goes out among the credentialed and asks, “Doest thou agree with me?” If the answer be “Aye”, the person is added to the Nice list; if it be “Nay”, the unfortunate is entered into the Persona Non Grata ledger. The IPCC then reports that there is a consensus among its membership, and that because this consensus is a consensus, its conclusions are beyond question.

    But “the” consensus is not a consensus of all climatologists. Your own author, for example, despite offering his services repeatedly—to be remunerated at the same rates as the rest of the Aye-sayers: he has to eat, after all—has never had his offer accepted. “The consensus” is therefore not a consensus in the plain English meaning of the word.

    Actually, of course, even some who say Nay make it onto the Nice list, but their views are not accorded equal weight with those of the leadership. See Judith Curry’s interesting post on “the” consensus for more on this (suggested by an anonymous reader).

  2. You’re no climatologist! The grandfather of all fallacies, the appeal to authority. This one generates more hilarity than any other. This fallacy occurs when a point made by a person outside “the” consensus is said to be invalid because the person making the point is not a “genuine” or “real” climatologist.

    First, if this fallacy was not one, then how can we explain that the IPCC could include so many non-genuine, un-real climatologists? A great chunk (even a majority?) of its members are economists, biologists, etc. Should we disbelieve what they say because these people are not genuine climatologists?

    An example of hilarity: musing on climate-gate, academic philosopher Gary Gutting writes in the New York Times,

    Some non-expert opponents of global warming have made much of a number of e-mails written and circulated among a handful of climate scientists that they see as evidence of bias toward global warming. But unless this group is willing to argue from this small (and questionable) sample to the general unreliability of climate science as a discipline, they have no alternative but to accept the consensus view of climate scientists that these e-mails do not undermine the core result of global warming.

    But, Gary, dear boy, just think: if you’re dismissing the claims of critics because they are “non-expert”, how then could you, as non-expert as they come, judge the IPCC’s claims to be valid? How can any non-expert “accept the consensus view”? I am an expert: I do not accept “the” consensus view. My expertise surely trumps yours. Therefore, you must believe what I say. If you retort that more experts take the opposite view than mine, and that therefore you choose to believe that what they say is true, then you have reduced truth to a vote. (Via Bishop Hill, via Randy Brich).

    This fallacy is pervasive and almost always used in Gutting’s form by civilians anxious not to learn any physics, but who are keen to shut up the other side.

    A person’s lack of credentials can be, and often is, relevant to why that person uttered a falsity, but it is irrelevant to proving the fallacy.

  3. The asinine comparison Technically known as the non sequitur, this one is most popular with politicians and pundits, and even the occasional academic philosopher. Examples here are legion. This is usually evidenced by calling somebody a “denier,” as pathetic a ploy as exists.

    It has also been used, in peer-reviewed publications, to compare disbelief if global warming as comparable for support of slavery. Whenever you hear we must not listen to the nay-sayers because we must “Save the planet,” or its many variants, you are hearing this fallacy.

  4. The economic fallacy See this post for complete details. The gist: the source of funding to the person who makes a statement is irrelevant to whether that statement is true or false. The source of funding could be, and often is, relevant to understanding why the person uttered a falsity, but it is irrelevant to proving the falsity.
  5. What you say hasn’t been peer reviewed! Yes, the appeal-to-authority in disguise. A statement is not true because a busy editor and two reviewers (who first look if their own papers are quoted in the paper under review) have said it is. Similarly, a statement is not false because it appears on a web site (and only reviewed in the comments).

    Again, a person’s failing to submit a statement to “peer approval” is, and often is, relevant to whythat person uttered a falsity, but it is irrelevant to proving the fallacy.