Some of my acquaintances believe that climate change may end human life (or at least civilization) and that the only way to save humanity is to massively reduce economic growth and consumption. Other acquaintances believe that climate change is, if not an outright hoax, a minor problem- and that even the slightest attempt to regulate emission-creating industries will itself destroy American civilization.
Most of these people are not scientists (let alone scientists specializing in climate-related science), so I strongly suspect that their opinions come from Al Gore's movie and Rush Limbaugh's talk show, rather than from a comprehensive review of the footnote-filled scientific papers addressing climate change. Nevertheless, they are as certain in their opinions as real scientists are. How come?
A plausible explanation was supplied by a Harvard Law Review article I recently read.* The article links disputes over technical issues to clusters of values that form competing cultural worldviews, most notably "egalitarian" and "individualist" worldviews.
The article asserts that egalitarians are "naturally sensitive to environmental hazards, the abatement of which justifies regulating commercial activities that produce social inequality." In other words, egalitarians are predisposed to be hostile to large-scale capitalism, and will thus naturally believe any theory that supports this predisposition. When capitalism failed to deliver economic growth in the 1930s, some intellectuals supported communism as more likely to do so (and perhaps more likely to enhance the status of intellectuals by dragging down corporate elites that outrun them in the race for wealth and power). And when capitalism has delivered economic growth, modern egalitarians decided that growth wasn't so great after all.
By contrast, the article notes, "individualists" generally "dismiss claims of environmental risk as specious, in line with their commitment to the autonomy of markets." In other words, individualists believe that (1) government should only regulates transactions that cause harm to others, and (2) this no-harm rule justifies a small government that does not interfere with commercial activity except to prohibit force and fraud. But proposition (2) makes sense only if most commercial transactions in fact do not cause significant harm to nonparties (or to use an economic term, "externalities"). But if nearly all commerical transactions do in fact create dangerous greenhouse gas emissions, proposition (2) fails, which means that the entire ideology of individualism is based on a falsehood (the idea that business activity does not generally create externalities justifying regulation). Because climate change appears to threaten the core idea of individualism, individualists will engage in considerable intellectual gymnastics to avoid climate regulation.
In sum, most people (other than a few scientists and economists who actually know what they are talking about)** with strong opinions on climate policy are responding less to objective reality than to their cultural values. As a practical matter, this means that Americans are going to have a great deal of difficulty reaching a popular consensus on climate policy; because the issue is so technical, ill-informed public opinion is likely to be impervious to new scientific evidence. The stalemate can only be broken through policies that appeal to both sides.
Indeed, the climate change stalemate provides a lesson for policy entrepreneurs in other fields (such as planning-related issues). Policies that attract broad popular support will be policies that attract support from both egalitarians and individualists. For example, zoning (despite its many flaws) is popular because it appeals to both egalitarians' desire to bridle developers and to individualist homeowners' desire to protect their property rights (since even individualist homeowners often see their neighborhood as part of their property).
*The cite is 119 Harvard Law Review 1071, and the article is available online at http://www.harvardlawreview.org/issues/119/feb06/kahan.pdf
**I make no claim to be part of this group.