Quite apart from the climate-related issues, Alex Thompson (of More4 news) made an excellent point about the foolishness of the government's decision to approve a third runway at Heathrow, in last night's Snowmail message.
Forget all the green stuff. It is simply this. The aviation business is contracting, not expanding, because of the current bust. Fact. If bust becomes boom more people travel, more people burn oil. Oil's a diminishing resource, so the price goes up. So fewer people travel because fewer people can afford it. So in a bust aviation contracts - and it will in a boom as the oil runs out. They're sunk either way. So who needs bigger airports?
That may be a pithy summary, but it's a very accurate description of a very straightforward - but often misunderstood - argument.