There’s an interesting announcement by the Cato Institute that is running in the New York Times and elsewhere, challenging the assumption that climate change is a crucial problem. You can see the ad at http://www.cato.org/fiscalreality. The interesting thing about this ad is that it relies almost entirely on "argument from credibility". Approximately 10% of the full-page announcement is devoted to what we’d call logical argument—e.g., “After controlling for population growth and property values, there has been no increase in damages from severe weather-related events. The computer models forecasting rapid temperature change abjectly fail to explain recent climate behavior.” The rest of the ad—about 80%--is devoted to a list of scientists, authors, and others (mainly Ph.D.s) who support the Institute’s position—115 to be exact—along with their degrees and affiliation or claim to authority. The website provides additional names. Regardless of what you think about climate change, the ad is interesting in terms of persuasion and the ways in which credibility and testimony can be used in building a persuasive case.