Sensibly applied, the idea behind the Precautionary Principle could be useful for global warming. The idea is that we should worry a lot about catastrophic low-probability events. The standard warmist scenario is not at all catastrophic. Adjusting to even a rise of 10 degrees Farenheit over 100 years is just not that bad. It’s the difference between Philadelphia and San Diego, and people do find the heat bearable when they move to San Diego. (Or use Boston and Atlanta if you like. But one thing I wonder about is how much of global warming will just be to make winters milder. The Highs in the Tropics are not higher than in the Midwest— they just last longer.)
But there is a possible catastrophe. It would be because of runaway effects caused by, for example, methane being released from Siberian swamps.
Correct use of the precautionary principle would say that we should forget about little things like cap-and-trade and instead (a) study possible catastrophes very hard,and (b) work on geoengineering, since mere cutbacks don’t address the problem (we could well be heading to catastrophe just with our present warming, and maybe it’s too late to go back unless we can get rid of carbon dioxide already in the atmosphere).
Thus, the precautionary principle really has the opposite implication of its standard use, which is to call for expensive CO2 cuts that won’t help with the small-probability, really-bad outcomes.
In fact, we could go a step further. Suppose we are limited to spending at most one trillion dollars dealing with climate change. Suppose, too, we think that(a) there is a 99% chance that if we do nothing, the temperature will rise and cause 3 trillion dollars in harm to the global economy , (b) there is a 0% chance that the temperature won’t rise, and (c) there is a 1% chance that the temperature will rise dramatically, killing off 90% of the world’s population. The standard global warming line is that we should spend the trillion dollars on substituting other inputs for energy, to reduce CO2 output and prevent the loss of the 3 trillion dollars. The precautionary principle says that we shouldn’t waste the trillion dollars on that— we should spend it on geoengineering research and technology to deal with the 1% probability of disaster, instead.
You may be tempted to reply that both the CO2 reduction and the geoengineering projects should be undertaken. Well, suppose we have 5 trillion dollars to spend. Why shouldn’t we spend all 5 trillion on dealing with the 1% probability of disaster? The more we spend, the higher probability we avoid the disaster, so why divert any of the funds to non-disaster scenarios?