I have been catching up with the Department for Transport’s latest ‘UK Air Passenger Demand and Carbon Dioxide Forecasts’, issued in January at the time of the decision to build a third runway at Heathrow.  A key question is whether there is a long term future for this extra runway in a world in which greenhouse gas emissions are reduced substantially.

UK aviation carbon dioxide emissions are forecast to be 58.4Mt in 2030 (37.5 in 2005), stabilising at 60Mt in 2050 on account of ‘market maturity and capacity constraints slowing demand growth’.   The capacity constraints arise from the assumption that the only additional runways ever to be built in the South East would be one at Heathrow and one at Stansted.   This seems rather arbitrary.   If there is case for more capacity to meet rising demand, why limit this to two runways; and if there is case for limiting capacity in the long run, why add runways now?

With the UK’s overall carbon dioxide emissions falling to meet the 80% reduction target by 2050, aviation’s share would be in the range 19-54%, according to the Department for Transport.   Currently, two-thirds of international passenger traffic through UK airports arises from leisure travel.   Is it plausible that leisure travel by air could be the source of a large part of the UK’s total carbon dioxide emissions by mid-century?  If not, the case for the extra runways looks thin.