ignoratio elenchi n.
A logical fallacy of presenting an argument that may in itself be valid, but has nothing to do with the proposition it purports to prove. Also known as “irrelevant conclusion”. [Lat. ignorance of refutation.]
The recent NY Times piece on the scientists who have criticized the movie An Inconvenient Truth has generated a flurry of discussion. What I saw when I read it was a series of Ignoratio Elenchi fallacies, so the scientists featured in the article win this week’s Ignoratio Elenchi Award.
The most basic of the Ignoratio Elenchi fallacies in the article is that if flaws in the movie can be found, the whole science of global warming is discredited. Even if, hypothetically speaking, the criticisms of the movie are correct, they don’t invalidate the basic facts – that global warming is caused by human activity (with 90 percent certainty, per the IPCC report), that the consequences could be catastrophic (again per the IPCC), and although the process is slow, the point of no return is coming upon us fast. It may take hundreds of years for sea levels to rise 20 feet, but if we don’t do something soon, there will be no stopping it. (See why the IPCC report is credible.)
A common thread of many of the criticisms in the New York Times piece is that the climate has changed in the past (true), so therefore global warming is of no concern today (not true). This “natural climate variability argument” typically comes in one of three varieties, each an Ignoratio Elenchi fallacy. Let’s take a look at them and their logical flaws, in case you have skeptics in your life with similar arguments.
Argument: Natural climate has varied in the past and life on earth survived, so the current climate change will not have catastrophic consequences.
The Facts: Climate has changed in the past, true. The difference now is that there are 6 billion people in the world. If millions of people are displaced by rising sea levels (a disaster that is already happening in some places), where will they go? If east coast cities are decimated by storms (think Katrina), what will we do?
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Argument: Past climate change was due to natural causes so the present climate change must also be due to natural causes.
The Facts: Climate has varied naturally in the past, and will continue to do so in the future. However, we understand the causes of past changes, and they don’t explain the current warming. If temperature increases, there must be a source of extra heat – this is a basic tenet of physics. In the case of global warming, scientists have eliminated all possible candidates (including the sun) with one exception – greenhouse gas pollution.
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Argument: Climate has varied in the past, so it could suddenly shift in the next decade to reverse global warming.
The Facts: The probability that global warming will spontaneously reverse itself is infinitesimally small. The probability that it won’t and we are on a collision path with disaster is very high.
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For more examples of typical skeptic arguments and the facts that refute them, check out our “Review of the Facts [PDF]“.