An interesting concept if applied across the board, and somewhat at odds with other moral precepts holding that we, the present, create future generations and have a moral obligation to improve their lot. Still, there's another reply that Felix Salmon came up with a while back:
I'd add that the benefits, to the extent that it involves technology transfers to developing countries, can help present-day poor people (yes, I know the $400b could help today's poorest even more effectively than through clean tech, but that's a purely rhetorical argument since it won't actually be used for that purpose.)
the $400 billion cost will not be borne by all present citizens equally – it will be borne much more by the rich, who are the major consumers of energy. If you compare the wealth of the rich today to the wealth of future generations in general tomorrow, then the increase looks much smaller.
The rest of Salmon's post is also good.
Via Brad DeLong.