I was inspired to create my own example* of a type of fallacy which I’ve just added - Self Defeating Argument:
Global warming won’t happen because an increase in ocean levels will mean an increase in ocean surface area, and as a consequence, more evaporation. This evaporation will cause cooling, thus cancelling out global warming from the greenhouse effect.
If we believe the conclusion, that excessive evaporation will cancel out warming by greenhouse gases, then how did the ocean surface area increase? (A prediction of global warming is the melting of polar ice caps which will cause a rise in ocean levels.) I.e,. the conclusion contradicts the premise, so is invalid (by definition the premise must be accepted as true for the conclusion to be valid - and a contradiction invalidates the premise). Thus we have a meaningless claim.
Now, of course, rephrasing we can forward a reasonable, non-contradictory hypothesis. The increase in ocean surface area could damp climate change - causing a lag in warming. Also it could be involved in a cycle, temp goes up, temp goes down, temp goes up, temp goes down... Or it could add to it, a positive feedback loop. (And, of course, there are thousands of other variables to take into account.)
*Disclaimer - any similarities between this "argument" and any argument forwarded by anyone, anytime, past present or future, is merely a coincidence.
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