PRINCETON – Many people who advocate draconian measures to counteract climate change base their argument on the so-called “precautionary principle,” which holds that when a possible future disaster would be unacceptably severe, action to prevent it is imperative. Cost-benefit analysis – balancing the cost of remedial action against the benefit of avoiding disaster – is no longer permissible. Action to counter the disaster must be taken, regardless of the cost.
This principle leads people to advocate enormously costly actions to prevent disasters that are even more enormous but whose likelihood highly uncertain. If a disaster is unacceptable, then, no matter how uncertain the likelihood of its occurrence, it must be prevented.
As a result of widespread reliance on the precautionary principle, doomsday scenarios have come to dominate discussion of climate change. It is easy to imagine disasters so severe that drastic action to prevent them would be reasonable, and advocates of drastic action can easily scare the public with imagined disasters. Nobody knows enough about the causes of climate change to prove that an imagined disaster is impossible.
What is wrong with the precautionary principle? It appears to be a statement of the obvious: unacceptable disasters require extraordinary counter-measures. The problem is that the principle cannot be applied consistently.