Green is as green does . . .

Who cares if Al Gore goes on a private jet, as long as he buys the appropriate carbon offset?

(A private jet, for those who may not realize it, is just about the single most carbon-wasteful thing in the world, except maybe burning high-sulfur coal for the sheer fun of it.)

There are two ways an economist could look at this.

One way of looking at it is that he doesn't add any more carbon to the world than he would taking a commercial flight, or walking, provided he buys the offset. This assumes, of course, that offsets work, a question in some doubt. But as long as you're efficiently pricing the environmental cost to be actually carbon neutral, it's none of our business what sort of transportation you use.

But another way of looking at it is that if Al Gore cares about the environment, and is willing to pay, say $500 to take the equivalent of a private-jet-trip's worth of carbon out of the air, then he ought to do so regardless of whether he has flown. He ought to buy all of the carbon offsets he feels necessary or affordable--and then reduce carbon still further by taking a commercial flight, or a train. Since Al Gore seems to feel that we should all do everything possible to reduce our carbon footprint, this is not unreasonable. Taxation is the solution to problems where you cannot secure the voluntary restraint of others; it is odd to try the same stunt on yourself.

I'm not sure which view I find more compelling. Does Al Gore have an obligation to not merely stay carbon neutral, but try to reduce the profligacy of his neighbors? Does it matter that he's made a tidy sum from those neighbors exhorting them to lower their carbon footprint? People seem to feel intuitively that it does, but the actual logical reasoning generally seems fuzzy.