No Mungo, just don't have kids
In a similar vein to Mungo's post below, a new paper from the Center for Global Development (downloadable here) reckons that the most cost effective way to reduce carbon emissions in developing countries is to have there be less people in developing countries!
They don't quite put it like that; they say the policies of "family planning and female education" are the biggest bang per buck, but both common sense and a reading of the paper show that what these policies do to reduce emissions is reduce the number of people.
People, don't get me wrong; I'm fully in favor of female education for reasons completely unrelated to carbon emissions!
As far as family planning goes, most countries undergo an endogenous demographic transition as they get richer. I am not sure that posters and free condoms can significantly speed up that transition.
While I in no way wish to impugn the motives of the study, a policy of poor country population control as a method of reducing carbon emissions makes me very uncomfortable.