There is one set of circumstances in which uncertainty is a reason for inaction: (a) the measures you would take would be expensive, (b) the measures you would take will be irreversible, and (c) you will get a lot of new information soon to help you judge the situation better.
That set of circumstances does not apply here.
Precaution, uncertainty, insurance, and morality: [G]reater uncertainty argues for more caution--more willingness to accept certain current losses to avoid possible large future losses--not less. That’s because it’s easier to adjust to small changes than it is to large ones, so damage is likely to increase more-than-proportionally as the size of the change increases. Assume some climate model predicts that... temperature would rise 3° C by 2100. If the model were very accurate and precise, that might be 3°± 1°. If the mechanisms involved remain obscure and the data unclear--as is the case today – that might be 3°± 5°.... Given how bad a 3° increase would likely be, if we knew for sure that would be the outcome in the face of inaction there would be a strong agument for making big and expensive policy changes to prevent it from happening. And if we knew that for sure, it would be very hard politically to argue against doing something about the problem. By contrast, 3°± 5° means that proponents of inaction get to say “We’re not even sure there’s any problem at all.” That makes the political case for action much weaker. But it makes the logical case for action much stronger....
[A]n 8° C average temperature increase... rendering much of the tropics virtually uninhabitable and, quite plausibly, hitting various triggers for positive-feedback effects such as the melting of the polar ice caps, which would reduce the amount of solar energy reflected back into space, and the melting of the Siberian permafrost, which would release a huge amount of methane, a potent greenhouse gas. (Most systems are more stable in the face of small changes than they are in the face of large changes.) Thus a primary increase of 8° might really mean an increase even larger than that: an increase that might not be reversible even if greenhouse-gas emissions were then sharply curtailed. That would be the kind of disaster to which some version of the precautionary principle reasonably applies....
Ordinarily, it is the proponents of action who bear the burden of persuasion. But in this case political inaction means, in effect, licensing a massive gamble.... [N]one of the arguments for the freedom of economic activity appl[y]... there is simply no “invisible hand” mechanism that directs private action in such a situation in the direction of the public interest.
The willingness of some politicians and pundits to bet the planet on the claim that climate scientists are talking through their hats, which involves the larger claim that they have managed to assemble an enormous conspiracy to perpetrate a hoax, calls either their intelligence or their morals into serious question. And that goes for the journalists and media moguls who treat their ravings as if they represented simply one side in a reasonable argument.
If anyone tries to tell you that uncertainty about climate change is a reason for inaction, he’s either a fool or a scoundrel. Probably a bit of both.