Carbon constraints relating to a new runway have been lost amongst the debate, not on “if” but only on “where”

In a blog, the Carbon Brief has a look at the climate and environmental impacts of the expansion plans by London’s airports. Leaving aside the noise and other impacts, and looking here just at carbon, it is clear that there is an issue.  While UK aviation makes up some 6% of just CO2 emissions, under the current system by which aviation is not required to cut its emissions by 2050, UK aviation will then make up about 25% of UK carbon emitted. The UK is required to cut its overall carbon emissions by 80% of their 1990 level, by 2050. Aviation just needs to keep its emissions to 37.5 megatonnes – which was about the level in 2005.  As long as the rest of the economy decarbonises very intensively, aviation could keep its very generous allocation. But that means not going above 37.5 Mt. A report in July, by AEF, showed that it would be likely that an additional new runway would contribute some 8.2Mt of CO2 per year, making meeting the 37.5 Mt target “effectively impossible”.  It would require air travel at regional airports to be reduced, which apart from contradicting regional development policies would be”politically very difficult to implement and have significant economic consequences.”


Blog by The Carbon Brief

Assessing the climate and environment impact of London’s airport plans

  • 2 Sep 2014,
  • By Robert McSweeney

 Airplane taking off | Shutterstock

This morning the Airport Commission dismissed Mayor of London Boris Johnson’s proposal for a new hub airport in the Thames estuary. With remaining options for expansion at either Heathrow or Gatwick what are the potential climate and environmental impacts of each?

The Airports Commission, chaired by Sir Howard Davies, recommended adding a second runway to south east England by 2030, with the possibility of another by 2050.

In December 2013, the Commission shortlisted three options for the first additional runway in its Interim Report – a second runway at Gatwick, a third runway at Heathrow or an extension to the second runway at Heathrow (so it operates like two).

Any expansion of airport capacity will lead to more flights and more passengers, and increase carbon emissions from aviation.

Carbon emissions

At the moment aviation makes up around 5% of the UK’s emissions – around 33.3 megatonnes (Mt) of carbon a year in 2011.  [More like 6.5% in reality].  Under the Climate Change Act, the UK must reduce its carbon emissions by 80% by 2050, compared with 1990 levels. That would mean we emitted no more than 160 Mt of carbon per year in 2050.

The Committee on Climate Change suggests that to stay under this limit, carbon emissions from flights will need to be no more than 37.5Mt per year.  At that level aviation would use up just under a quarter of the UK’s carbon budget in 2050.

So can airports expand and stay within this level?

Research from the think tank Aviation Environment Federation (AEF) suggests not. Their analysis found that a new runway – wherever it is situated – would contribute an additional 8.2 Mt of carbon emissions, making meeting the 37.5 Mt target “effectively impossible”.  [AEF report  The Implications of South East Expansion for Regional Airports”  is available for download here.]

The study, funded by the WWF, developed future scenarios of emissions based on aviation forecasts from the Department for Transport.  It found that in order to build a new runway and still meet the 37.5 Mt target, air travel at regional airports would need to be reduced. This, the study concluded, would be “politically very difficult to implement and have significant economic consequences.”

Other environmental impacts

Heathrow has been a victim of its own success. An extra runway would make this huge airport even bigger, exacerbating local environmental challenges. The air quality around Heathrow, for example, is consistently worse than the standards required by the EU. Heathrow’s most recent proposal suggests more frequent rail links and a congestion charge to discourage passengers from using their cars.

Noise is also a significant issue. A study commissioned by the Mayor of London found that a third runway at Heathrow would increase the number of people affected by aircraft noise by over 300,000 – to over a million.

Solutions such as steeper flight paths, no-flight periods and paying for insulation are proposed to manage the problem. Failing that, the airport says it will provide compensation to those affected.

Heathrow Expansion _Air Noise

Change in patterns of air noise with additional runways at Heathrow.  Heathrow Airport July 2013

Heathrow is also on Greenbelt land, but the 2003 government White Paper on Aviation had already decided that: “the benefits [of expansion] would outweigh the environmental impact as long as the effects were properly controlled.”

Gatwick would face many of the same issues as Heathrow, albeit to a lesser degree as it is a smaller airport.  But it’s also located in a more rural area. A study commissioned by West Sussex County Council found that a new runway would require 30,000 to 45,000 new homes to be built in the area. Gatwick’s largest nearby town is currently Crawley, with a population of around 40,000.

Rejected options

‘Boris Island’ is the most famous of the airport expansion proposals, with the Mayor putting forward plans for a hub airport to be built in either the inner or outer Thames estuary. Its drawbacks were well documented – not least a potential cost of £120 billion and the likely impacts on important habitats in the area.

But a hub airport in the inner estuary did have some appeal to the Airport Commission, particularly for the potential to “reduce aviation noise impacts in the South East of England.”

Other options – such as expansion of Stansted or Birmingham airport – were also discounted in the Commission’s Interim Report, primarily because those airports will not be operating at capacity for many years.

With the Commission expected to make its final decision next summer, this leaves three options in two locations.

But with vocal advocates and opposition for each, it appears for the moment that the effect any new runway would have on the UK’s carbon targets has been lost amongst the noise.



The key findings of the AEF (Aviation Environment Federation) report  are:

 Building a new runway in the South East would in practice mean that airport capacity elsewhere would need to be reduced in order for UK aviation to keep within carbon limits required by the Climate Change Act. This could involve closure of a number of regional airports.

 Government policy, however, supports the growth of regional airports, and official forecasts anticipate that they will grow by over 200% between now and 2050. Many airports in fact consider Government figures to be conservative. With politicians from all main parties having made commitments to supporting regional economic growth, capping or reducing aviation activity outside the South East would therefore require very significant hurdles to be overcome.

 By contrast, with full utilisation of current airport capacity, it would be challenging but
achievable to keep aviation emissions to a level compatible with the Climate Change Act.


The Summary of the AEF report states:

Capping capacity may not at first glance appear the ideal solution to the aviation emissions
challenges. Indeed the fact that emissions are forecast to exceed the 2050 target even without increasing runway capacity demonstrates that other measures – such as MBMs, taxes, carbon efficiency incentives, or a moratorium on any new planning permissions or terminal expansions – would need to be implemented even if no new runways were built in order to bring emissions down to the required level.

But as we argued in our 2011 analysis for WWF, we believe that while challenging, the 37.5 Mt tonne target is – with a committed focus on making best use of existing airport capacity – achievable. With a new runway, by contrast, it would be effectively impossible.

Our airport capacity scenarios illustrate how difficult it would be to constrain demand to a target compatible level if a new runway were to be built. The fact that the 37.5 Mt target would be breached even if regional airports were prevented from increasing their passenger throughput from today’s levels (for example using powers available to the Secretary of State under the Civil Aviation Act) suggests that achieving the climate target while building a new South East runway would require an overall reduction in activity at regional airports.

Not only would this be politically very difficult to implement and have significant economic consequences, it would also run directly counter to the Government’s support for regional airport growth set out in the 2013 Aviation Policy

Full report at