24July

An organisation of aircraft pilots said that they are being made scapegoats for carbon dioxide emissions. BALPA says air travel accounts for only 2-3% of global carbon dioxide emissions. The group's chairman, Mervyn Granshaw, claimed that the latest jets are more carbon efficient than the newest high-speed trains on longer journeys.

Two points from this: first, airlines are already noticing changes in passenger behaviour. 60% of people say they might be prepared to fly less to help the environment, 25% are prepared to fly less, and 10% have already reduced their flights. Obviously, fewer passengers will translate into fewer flights, which will translate into fewer airline pilots, which will translate into fewer members of BALPA.

And second, that claim that planes produce less carbon dioxide than trains is a complete load of nonsense. Virgin Trains claims (in a 6 June 2007 press release) that its trains emit 76% less CO₂ than the same trip by plane, and cites a study by Edinburgh Centre for Carbon Management Ltd., an independent consulting company, based on flights between London, Manchester, Liverpool, and Glasgow. The Advertising Standards Authority upheld the factual accuracy of this claim.

An DEFRA study suggested the following emissions as a guideline:

Car – about 180 g CO₂/km per vehicle [1]
Train – about 35 g CO₂/km per passenger on an averagely-laden [2] train [3]
Air – about 280 g CO₂/km per passenger on an averagely-laden [4] short-haul [5] flight; about 200 g CO₂/km on a averagely-laden [6] long-haul [7] flight. [8]

[1] The additional emission from carrying an extra passenger and luggage is deemed negligible.
[2] 65% of seats occupied.
[3] Based on the passenger mileage of diesel trains (42g per km) and electric trains (25g per km) in the UK in 2002-3.
[4] 65% of seats occupied.
[5] 500km flight.
[6] 70% of seats occupied.
[7] 5000km nonstop.
[8] Aircraft figures are raw emissions multiplied by 1.9, the international standard adjustment for radiative forcing – the extra heat retention of CO₂ deposited directly into the upper atmosphere.

For a completely full long-haul plane, the emissions will drop to about 140g per passenger km. For an almost empty train running at top speed on diesel (for electrics emit about 60% less carbon dioxide than diesels, and the high speeds of express trains mean they emit more than stoppers), the emissions could rise to about the same figure.

At the very least, though, the pilots are giving a deliberately misleading impression. Very few people would take a train from (say) Glasgow to Constantinople – it's a journey of not much under three days, and travellers run the risk of the city changing its name before they arrive. A fair comparison is on routes where the train and the plane are in direct competition, such as Glasgow to London. Here, on average, short-haul flights emit about seven times as much carbon dioxide per passenger as the comparable train journey.

Is carbon dioxide the end of the argument? No, but studies have been done into this area. The total externalities for trains are slightly less than half of those for planes. This complete consideration leaves some scope for short-haul routes – for instance, Exeter and Swansea are about 100km apart as the crow flies, but almost 250km by rail. A fully-laden plane would be no more than twice as polluting as the train, far less damaging than a car, and incur lower net externalities than either.

| Permanent link