spiked has provided a rare opportunity for a balanced debate without one side being censored, as usually happens in the established media. Some of the contributions are rather prolix and diffuse, but the attack on Courtney by Viner cries out for logical analysis. The first two sentences are colourful abuse and can be dismissed as empty rhetoric. Then we have:
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Courtney may dispute human-induced climate change, yet he cannot produce the evidence against it. This is an example of the fallacy of argumentum ad ignorantiam: you cannot prove that the moon is not made of green cheese, therefore it is.
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Even the Bush administration accepts that climate change is occurring, as do many other governments and large corporations. The fallacy argumentum ad vericandiam; quoting authorities who are not experts in the field.
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Courtney is one of a dwindling and increasingly ignored band of individuals who perpetuate incorrect and flawed propaganda. The fallacy argumentum ad hominem (abusive) supported by unsubstantiated assertions. Also by implication, the fallacy argumentum ad populum, that a proposition is true because it is popular.
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The IPCC does not state that the climate has not changed in the past - it has, and it is these changes that enable scientists to view the current changes in context. The Straw Man fallacy; attacking an argument that was not put forward in the first place.
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At least Courtney accepts that the Earth's temperature has risen by 0.6 degrees C, accepting a major finding of the IPCC. Misrepresentation; Courtney accepts nothing of the kind.
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Courtney's statements regarding carbon dioxide (CO2) and temperature (that 'one follows the other') are partly correct. Increase temperature and the carbon cycle responds: CO2 increases. What drove these changes in the past were long-term (tens of thousands of years) changes in the Earth/solar orbit. However, there is also a proven link that if you increase CO2 you increase the radiative forcing, and temperature increases. Thus any temperature increase will raise CO2 levels even further - a positive feedback effect on top of any human-induced increase in CO2 emissions. The fallacy of exclusion; the hugely dominant greenhouse gas (water vapour) is left out of the argument.
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Who is ignorant of misrepresenting the science, Mr Courtney? This sentence defies logical analysis.
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With regards to petitions, the Oregon petition that Courtney refers to was organised by a right-wing think-tank that has no scientific credibility. The fallacy argumentum ad hominem; the organiser might well be a murderous Nazi rapist, but this does not affect the validity of the exercise. Furthermore, the political cat is let out of the bag.
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The signatories (including the Drs in MASH and Ginger Spice!), if real, are themselves not scientists (there are not 18,000 climate scientists in the USA). The fallacy of composition (in the parenthesis followed by an exclamation mark, though it is not an exclamation); a few exceptions do not devalue the genuine thousands. This is a well-established technique of undermining the opposition's petition. In any large petition a few Donald Ducks and Marilyn Monroes are inevitable. The main clause, apart from breathtaking hubris, is a nice inversion of the fallacy argumentum ad vericandiam; the Bush administration is an acceptable authority, but thousands of people who are (or ought to be) trained in the scientific method are not. Daring to claim that many of the most distinguished people in science are not scientists beggars belief. The fact that the number of climate scientists is small (mercifully, if I may intrude an opinion) is irrelevant (the fallacy ignoratio elenchi) and many would regard the subject as a purely political construct around a branch of applied physics.
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Courtney has showed his ignorance or deliberate misrepresentation by saying that people only read the one-page executive summary of the IPCC. If people are to make bold statements about the IPCC reports they should read the reports. A non sequitur; the second sentence, which is true, does not follow from the first, an abusive account of a generalisation that is largely true.
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The coda is a return to the fanciful abuse of the opening. One is tempted to fall into the fallacy of ad hominem tu quoque - You too, Guv! Which is an exclamation.
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For further explanations of the fallacies see, for example, Stephen'sGuide to the Logical Fallacies
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John Brignell is author of Sorry, Wrong Number! The Abuse of Measurement and the website Number Watch.
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