Yes, they r pretty accurate at predicting the weather a day or two out, but if they r off by even a small margin (which they always r), then the farther out u predict, the more it magnifies the error (doesn't just add to it, it multiplies it) to the point of being irrelevant. When it comes to global warming, the models are (without fail) always wrong. According to the earliest ones, we should have used up all fossil fuels, used up the worlds food supply, ect... all before I was born in 1980!
So, according to your logic here, if we r dealing with something that, if true, has great potential to harm us we should take action to prevent it. The burden of proof is secondary to the percieved threat. Can u say Big Brother? Japan might declare war on us again. There is no evidence to suggest they r thinking that, and they have no military to speak of, but they might, so lets put all american japanese back into concentration camps!!
The point I am making, is that, logically the burden of proof has to primary, before the degree of any potential threat is to be considered. Basically, u r reversing the same logic that liberals and libertarians use against the Patriot Act and the war in Iraq.