A lot of people, conservatives especially, look at these data points and say there's no reason for the United States to take any action on emissions levels. It doesn't seem as if there's any hope of us canceling out China's growth, after all. I think that's wrong for a couple of reasons. First, given our historical and current per capita contribution to global emissions, we have a moral responsibility to do our part. Second, our contribution to current emissions is substantial; reducing per capita carbon output to European levels would have an appreciable impact on global emissions. Third, we shouldn't be too pessimistic about Chinese emissions growth (and emerging market growth generally) because most of the infrastructure and power generation construction they're going to do lies ahead of them, suggesting there's a lot of scope for green investment there (especially if we offer to help with these investments). Fourth, we can make a lot of money providing green technologies to the Chinese, and fifth, the best way to encourage development of potentially profitable green technologies is to price carbon here.

Alternatively, we could do nothing but harangue China about their emissions growth while we continue to live some of the dirtiest lives on earth.

Libertarians out there will say there's a third option -- we could offer an enormous prize to whichever inventor comes up with a carbon eating technology that will save us all. These folks will argue that we shouldn't want China to do anything to slow their growth, in that case, because a richer China will be more likely to come up with the requisite technology.

I'm much more sanguine about the likely effects of carbon pricing on short and long-term growth than such writers, and so I see few reasons to not make pricing part of whatever solution set we choose. But I think it's also important to recognize that technology is unpredictable -- think of all the innovations that have been just around the corner for decades -- and so I'd prefer to count on the millions of small innovations likely to result from carbon pricing which will help us to reduce carbon output, than hold out hope for one which can effectively reduce atmospheric carbon.

And second, given a long enough time frame for the development of the savior technology, during which time emissions will grow unabated, the negative effects that we're likely to experience from warming may be severe enough to make realization of the miracle technology a rather Pyrrhic victory. Uncertainty remains about the probable path of CO2 concentrations, and uncertainty is not our friend. If a concentration of 450ppm touches off feedback effects that rapidly get us to 800+ppm, then it won't much matter if we eventually find something which can get concentrations back to safe levels.

Once we get to a high enough concentration, we're in a corner -- either we'll invent our way out of trouble or suffer dire consequences -- and the folks alive then will wonder why we didn't try to hedge our bets by reducing actual emissions at a time when it would have mattered.