depends on who your friends, relatives and colleagues are

All those who fail to tackle the problems of pollution and climate change “will feel guilty on their deathbeds”, says a leading environmental campaigner. Mayer Hillman, formerly a fellow of the Policy Studies Institute, claims that there is now a broad consensus that travel by both road and air is pushing the planet towards “a situation which will become critical well before 2050”.

Describing climate change as an ethical issue and personal responsibility as a moral imperative, Hillman championed the imposition of an individual allowance for greenhouse-gas emissions, allowing those who are able to live with greater energy efficiency trading their surpluses. People without cars, for instance, might sell their allocation to people who wanted to travel more often.

Having given up flying on principle, he has been unable to visit friends, relatives and colleagues around the world, but says that the sacrifices are not as bad as they might seem.
The Telegraph (UK), 24 Jul 2004