One major problem with most invocations of the precautionary principle is that people tend to apply it to whatever danger they want to prevent, but largely ignore it in considering the potential dangers created by the policies they advocate. For example, Dick Cheney applied a version of the principle to the threat of terrorism, arguing that even a small chance of a catastrophic terrorist attack justified taking sweeping measures to eliminate it. At the same time, he tended to ignore the potential dangers of the anti-terrorist measures themselves. Similarly, environmentalists apply the precautionary principle to global warming, but not to the risks created by policies intended to alleviate global warming.
If we have to take seriously the dangers of a global warming catastrophe, we should give equally serious consideration to the risks on the other side. For example, it’s possible that cutting carbon dioxide emissions by 80%, as some environmentalists advocate, would devastate the global economy, impoverishing millions and causing widespread suffering and death. Moreover, enforcing a worldwide cap and trade regime strong enough to compel obedience by China, India, Russia, and other potentially recalcitrant states might require a global authority with massive powers; even if these states formally agree to a cap and trade system, they might not enforce it aggressively against their own industries, unless compelled. The vast powers necessary to impose compliance could easily be abused in a variety of ways. In the most extreme scenario, the enforcement authority could eventually become an oppressive or even totalitarian world government from which there is no hope of escape. These two scenarios are admittedly unlikely (though the first is improbable largely because an 80% emissions cut is likely to be politically infeasible for the foreseeable future), but they can’t be completely ruled out. If, as Thomas Friedman [...]