Airport expansion and the Paris Agreement

A couple of weeks ago I commented to a fellow blogger on a posting about airport expansion at Heathrow or Gatwick and said:-

COP21 brought a touch of reality to thinking in high places on climate change. One implication is that the UK’s commitment to 80% cuts [in greenhouse gas emissions] by 2050 can no longer be considered adequate. By 2050 we will need to be completely carbon neutral, as will the whole world shortly after. This means that by then any aviation will either need to be completely carbon neutral (running exclusively on biofuels or something not yet invented) or offset by carbon-negative activity.

The date by which we become carbon neutral is less important than what we emit in the meantime. We need to start making big cuts in emissions now and I don’t think an optimal mix of cuts could exclude aviation.

Hence the big issue is not where we site a new runway but how quickly we can reduce aviation, so turning any new investment in airport capacity into stranded assets....

Sorry – I’ve made a lot of sweeping statements here. I’ll try and justify my position in a resuscitation of my own blog.

Well, this is the resuscitation and I hope my blog survives for a reasonable time before it falls into its next coma.

For me, the key feature of the Paris Agreement was the commitment "to pursue  efforts  to limit the  temperature  increase  to 1.5°C above  pre-industrial levels". These are weasely words but at least they signal a recognition that to aim for a mere likelihood of keeping warming under 2°C was not enough - it involved an unacceptable risk of runaway global warming with catastrophic consequences for human civilisation.

Since I wrote the comment I have put together my justification based on the Paris Agreement and the latest IPCC assessment report (AR5). It's pretty wonkish so I've relegated it to a separate page. it concludes:

If the government decides to allow expansion at either Heathrow or Gatwick, this will be a clear signal that it has no intention of honouring perhaps the most critical commitment in the Paris Agreement.

My justification strays a little from my original comment as I based it on a scenario showing the phase-out of emissions extending to 2100. However this necessitates global emissions reductions of 95% by 2050 so I think my comment remains broadly valid.

I have a lot of faith in my own fallibility so I would welcome scrutiny of the page and comment by a fellow wonk.

You may well ask why did I bother. After all, no-one ought to take any notice of a quasi-scientific paper by anyone as unqualified as me. Well, I regard myself as a student of the issues and, to get to grips with them, I sometimes feel a need to get my hands dirty and work out my own conclusions from comparatively raw data (raw when compared with, say, the content of a newspaper report). What I have concluded seems roughly in line with what mainstream scientists (but not politicians) are saying.