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.

Some flying will be possible, if planes can be made to run entirely on synthetic fuels. This looks technically feasible and it seems likely that fuels could be synthesised in a way that does not directly compete with food production, perhaps using biomass and hydrogen produced using solar power. However, if the CAT estimate is borne out, flying will still need to be cut by two thirds. This is partly because the warming effect of emissions from flying is greater than through the release of the same gases at ground level.

The days are long gone when an 80% reduction in carbon emissions, enshrined in the Climate Change Act, was an adequate target for 2050 (see a previous posting). With some increases in efficiency, that 80% target would have allowed aviation to continue at least at its present level until 2050. In the absence of proven technologies to suck greenhouse gases out of the atmosphere, the whole world needs not only to be carbon-neutral by about 2050 but also to keep within a strict carbon budget in the meantime. We won't suddenly be cutting aviation by two thirds in 2049. Long before then, we will need a reduction in flying to contribute to the general reduction in greenhouse gas emissions.

How sensible, then, is it to cater for expanding demand? If we are serious about climate change, the level of carbon-intensive activities should be determined not just by demand but also by the need to cut carbon emissions. If the CAT estimate is anywhere near right, investment in new airport capacity looks like stranded assets from the start. 

The drive for airport expansion is getting extra impetus from Brexit. Reduced trade with EU countries implies more trade with more distant countries and that means more demand for long-haul flights. It also implies that the goods we import and export will travel longer distances and will hence require more energy to deliver to their markets.

However, other scenarios are possible. Reduction in trade with the EU countries may simply mean less trade overall. This could mean that the British economy becomes more self-contained, diverse and resilient but less efficient, yielding lower but perhaps adequate material living standards. Britain could become a pioneer in post-growth economics -  though I doubt if this is what many people had in mind when they voted Leave.