Friday, 27 December 2013

How can we meet climate change targets while building new runways?

On 17th December, the Airports Commission announced their intention to consider Gatwick for a new runway and Heathrow for a double length runway, in order to increase capacity for more flights [1]. Many people object to these plans because of increased noise and pollution and also climate change impacts. More flights means more carbon emissions. However, the Committee on Climate Change (CCC) has estimated that we can fly 60% more than we did in 2005 and still meet out climate change targets [2]. How can this be?

The short answer is that our targets for carbon emissions for aviation are extraordinarily unambitious, compared to other sectors. While the overall aim is to reduce our greenhouse gas emissions by 2050 by 80% from 1990 levels, our current goal for aviation is for 2050 emissions to be no worse than 2005. As it happens, 2005 was a peak year for aviation emissions, at 38 Mt CO2 (see chart below). Then the recession hit and although emissions are creeping up again they were below 35 MT CO2 in 2011. Also, emissions in 1990 were half those in 2005 so this target implies doubling emissions for aviation compared to 1990 while everything else reduces by 80%.

UK greenhouse gas emissions from aviation (2011) (

This would not matter if airline emissions were an insignificant part of our overall emissions but this is not the case: in 2011 the aviation accounted for 5.9% of UK greenhouse gas emissions [3]. If the absolute level stays the same then by 2050 aviation will be 30% of our emissions.

Our government is apparently unable to conceive a future where airline travel does not grow. The 2050 pathways analysis calculator [4]allows you to evaluate the impact of various strategies for achieving our overall climate change targets. It gives you 4 levels of increasing ambition on 42 policy options, with level 4 requiring a huge effort. For example level 4 on home insulation requires 24 million homes to be extensively insulated and overall heat loss from the housing stock reduced by 50%. For domestic transport, level 4 involves the same amount of travel as today but more use of buses and trains and much less use of cars. For international aviation the level 4 scenario is 'only' an 85% increase in passenger miles. The level 1 option, business as usual, is 130% more.

Air travel can grow without increasing emissions if there are efficiency savings to offset the growth. The CCC projects 1% increase in efficiency per year leading to a 35% saving by 2050, mostly by improving designs for aircraft engines and airframe. They also anticipate some savings from switching to biofuels - but even if you agree that biofuels do contribute to carbon savings there will be a lot of other competing uses for them.

The current UK target of keeping emissions to 2005 levels was announced in 2009 and is not legally binding like our other targets. This is because there is no international agreement on how to limit aviation emissions and they come outside the Kyoto protocol. At the last summit of the International Civil Aviation Organisation (ICAO) in September this year it was agreed that member nations should report back in 2016 for a market based measure that could be implemented by 2020. In the meantime, the EU established a cap and trade scheme covering all flights arriving or departing from the European Economic Area. The cap is set to reduce slowly so that in 2020 it will be down to 95% of 2005 emissions. This is a bit more ambitious than the current UK target but still nothing to get excited about. Even so, the scheme attracted huge opposition: 26 third party nations, include the US, Russia, China and India, have formally objected on various grounds including infringement of their sovereignty. The EU was forced to compromise. Negotiations continue and in the interim the scheme is only enforced on flights within Europe.

By the way, high speed rail is not a panacea for reducing carbon emissions from intercontinental travel. High speed trains use more energy than conventional trains, which is hardly surprising considering that air resistance increases with the cube of speed. In any case, aeroplanes aren't as bad as you might think compared to trains. The carbon factors for UK national rail travel are 58 g CO2 /pkm compared to 91 gCO2/pkm for economy class short haul international flights [5]. (The air is much thinner up there so air resistance is lower). Network Rail admits that high speed rail has higher carbon emissions than conventional rail per seat km but estimates lower emissions per passenger km for HS1 because the faster trains will be more full of people [6].

You might think that growth in airline travel is critical for our economy, because limiting air travel will inhibit international business. However, my earlier research (Airline Boom or Airline Bust - and telepresence ) found that only 13% of travel is for business and this is one area where alternatives such as video conferencing are effective. In fact most air travel is for holidays so more air travel will mean more tourism. This makes me rather worried. Speaking as a resident I can assure you that Cambridge has quite enough visitors already. Can the additional holidaymakers go somewhere else, please.

[1] Airports Commission: Interim Report ( 17th Dec 2013
[2] Committee on Climate Change Factsheet: Aviation ( March 2013
[3] UK Emissions by sector (
[4] 2050 calculator tool
[5] Guidelines to Defra /DECC GHG Conversion Factors for Company Reporting (wwww.defra.2012)
[6] Comparing environmental impact of conventional and high speed rail (Network Rail)

1 comment:

  1. As you observe high speed rail isn't _that_ much more energy efficient, but a) it is electrified and thus can be made very low carbon and b) the longer travel times reduce long-haul travel in themselves (A significant fraction of long-haul flying only occurs because it's quick - if it took 3-5 days people would think a lot harder about how badly they needed to go)