So it's Heathrow

Last week I commented on the then impending decision on a new runway at Heathrow or Gatwick. At the weekend I was pleased to see an opinion piece in The Observer by David Mitchell, where he raised a question: 

Climate change is definitely happening. Aviation contributes hugely to it. So global levels of aviation must be significantly reduced. Why is it, then, that everyone with a whisker of a chance of power agrees that London’s airport capacity should increase?

Heathrow or Gatwick - do either make sense?

Recent political events have caused some previously disjointed thoughts to coalesce.

Let's start with the impending decision on whether a new runway should be built at Heathrow or Gatwick. This raises an interesting question: how much aviation will be possible in a zero-carbon Britain and a zero-carbon world? The only attempt at an answer that I know of comes from the Centre for Alternative Technology (CAT), who gave a tentative estimate in 2013 that in zero-carbon Britain, aviation would be limited to about a third of its present level.