Professor Cowen says:
Your net carbon impact depends far more on the number of children you will have than any other variable; remember good environmentalism uses a zero rate of discount. So people with no biological children should be allowed to fly a lot and people with lots of biological children should not get to fly so much at all. Is that so far from the reality we observe?
It's nice of the good Professor to suggest that some people should be allowed to fly. I hope our new economist overlords will continue to grant us some freedoms, even if they increasingly work to tax all costly behaviors (i.e. all behaviors).
The question I have in response is: what price should be paid by childless people for being childless? After all, if everyone is childless, the GDP of the world will gradually approach $0; that's a PPP-adjusted loss of roughly $65 trillion. Even if you don't use a discount rate that guarantees your desired outcome in advance, that's still a huge loss.