The American Clean Energy and Security Act (ACES) -- the bill that would impose a cap and trade regime for U.S. carbon emissions -- has passed the House of Representatives. Was it worth it? Well, on its own, ACES will in no sense make the world a cooler place. Other nations will help themselves to more coal, like bad kids on Christmas morning. An American cap and trade bill will have a meaningful impact only if it induces other nations to follow suit. So the hope -- plausible if not irresistible, I think -- is that passing climate-change legislation will be a powerful gesture before December's United Nations climate change conference.
But even if the Copenhagen Conference produces a meaningful consensus on climate change, will it matter? Jim Manzi does not think so. He runs some numbers, in response to a post I wrote yesterday, and concludes that even if you eliminate all the costs of global warming in the next century, the economic benefits would be negligible -- and certainly disproportionate to the hysterical rhetoric you hear from the left.
It's possible to quibble with Manzi's data. (More recent temperature estimates than the IPCC's exist: You can check out the work of MIT's Joint Program on Global Change for more.) Or, one might suggest that the factual uncertainty here suggests erring on the side of caution. (If Manzi is right, your children will enjoy a 1% increase in consumption. If Manzi is wrong, your children will know a world with fewer island nations.) But I don't think making a compelling case for regulating carbon emissions requires diving down that empirical rabbit hole. Even if we assume that the worldwide future economic benefits from cap and trade are tiny -- and, on the flipside, assume that the average economic costs of global warming are small -- the critical consideration is where those costs and benefits fall.