The CC was a group of economists who got together and tried to figure out which world-problems were most economical to solve. I.e., if you had a fixed amount of money where would you spend it to do the most good. The list was something like: 1. AIDS prevention in Africa. 2. AIDS treatment in Africa. 3. Generalized healthcare in the 3rd world. etc etc. Last. Climate change
There are a lot of problems with the approach they took (considering only at the monetary value of lives not the "spiritual" value, assuming that charitable giving is a finite resource), but their approach of trying to do a reasonable cost-benefit analysis yields some very interesting results.
If I really thought the cost was equivalent to "counting beans" and the benefit was avoiding a situation where we could no longer find arable land, I would agree that we should act quickly and strongly to halt CO2 emissions. In fact, I suspect that allowing the third-world access to cheap (fossil fuel) energy will benefit them more than avoiding small changes in climate.
Of course, when it comes to American's perceived god-given right to drive around in monsterous SUVs...I come down firmly on the side of the environmentalists!