Balancing Risks

I agree with Jim Manzi’s position, as he lays it out in his smart reply to Jonathan Chait:

Carbon dioxide is greenhouse gas, and if you put more of it in the atmosphere, then all else equal the Earth will get warmer. The key unknown, because of the complexities of climate feedbacks, is how much warmer. The UN IPCC forecasts that Earth will get something less than 3C hotter within about a century, and further estimates that 4C of warming would cause the world to lose 1% – 5% of GDP; therefore the expected costs of global warming are on the order of 3% of GDP sometime well into the 22nd century. This is a huge amount of money, but not exactly consistent with Miami becoming an underwater theme park. Given that global consumption is projected to grow from about $6,600 per person per year today to about $40,000 per person per year over the next century, it’s pretty hard to justify massive sacrifice of wealth today for the purpose of preventing our descendants a hundred years from now being only 5.7 times, instead of 6 times, as rich as we are. The real risk is that science has radically understated the greenhouse effect. A carbon tax designed for the expected case can safely be avoided for decades, while a carbon tax high enough to ameliorate a low-odds disaster scenario would be insanely expensive. Relatively low-cost investments in specific technologies that would be useful if such a disaster scenario arose, on the other hand, are a smart insurance policy.

Why don’t more people believe something like this?