The aeroplane was one of the major technological innovations of the 20th century. The advent of passenger air travel opened up the world, including remote and previously inaccessible and unvisited regions, to both business and pleasure travel. Journeys that previously took weeks of travel by sea can now be completed within a matter of hours. Ever-shorter journey times have delivered many positive social and economic benefits. Discounted international flights have made foreign holidays even cheaper than domestic breaks, thereby democratising the overseas holiday market for the British public. The massive resulting expansion in air traffic has, however, led to concerns over its detrimental effects on the environment, especially since air travel is the world’s fastest growing source of greenhouse gas emissions. Currently, around 2.5 per cent of global carbon dioxide emissions result from passenger air flights.
Fast forward to October 2019. The brakes are now being applied to air traffic. The Committee for Climate Change, an independent executive non-departmental public body that advises the UK government on emission targets, has issued a report titled ‘Behaviour Change, Public Engagement and Net Zero’. The report, authored by Dr Richard Carmichael of the Centre for Environmental Policy at Imperial College London, recommends banning air mile schemes that reward frequent flyers (the 15 per cent of the UK population responsible for all 70 per cent of all flights) , while simultaneously proposing an “escalating air miles levy” to avoid penalising those taking an annual holiday.
The detrimental effects of an exponential increase in global air traffic have been recognised for some time. As a result, in October 2016, 191 nations signed a landmark accord at a meeting of the International Civil Aviation Organisation (ICAO) in Montreal. It was agreed to set a target for a 50 per cent reduction in aviation-related carbon dioxide emissions by 2050. The proposed scheme was to apply to passenger and cargo flights that generate more than 10,000 tonnes of annual greenhouse gases.
Going back to the basics- aircraft engines emit heat, noise, particulate matter and greenhouse gases. Airplane exhaust contains a range of air pollutants, including sulphur dioxide and nitrogen dioxides, in addition to carbon dioxide generated by the burning of aviation fuel- a form of fossil fuel-which adds to a largely invisible carbon footprint. Pollutants are emitted not only during take-offs and landings(so-called ground emissions), but also while climbing, cruising and descending. Even idling on an airport tarmac is a significant source of air pollution. Cruising at the usual altitudes of around 35,000 feet also creates water vapour trails (contrails or condensation trails), caused by condensation and freezing of water around aerosol emissions, and produces ozone. Contrails can further lead to cirrus cloud formation.
The question is why air travel has become so cheap. To begin with, the Convention on International Civil Aviation, signed by 52 states on December 7 1944, discouraged the taxation of aviation fuel on international flights The aim was to promote international air traffic in a new-found spirit of global amity and cooperation. Consequently, airlines do not have to pay duty or VAT on aviation fuel and airline tickets. Within the EU, Article 14 of the Energy Taxation Directive (2003) permits member states to continue to exempt aviation fuel for domestic, intra- and extra-EU flights from taxation. This has led to recent calls for the imposition of a global carbon tax on air travel. Yet, in an intensely competitive market, low-budget no-frills airline operators have slashed airline ticket prices to unbelievably low levels, achieved in part by herding economy class passengers into cattle-class transport.
So, what has the airline industry done so far to reduce carbon emissions, and what options are indeed available? Technological solutions include the introduction of new fuel-efficient aircraft, the development electrical engines or battery-driven planes, as well as the use of alternative aviation fuels in the form of biofuels based on biomass. According to the Civil Aviation Authority and other sources, fuel efficiency depends on a number of factors, other than aircraft type, weight, engine and configuration. These include flight length and route flown, weather conditions, and the total load carried, which comprises passenger numbers, amount of cargo or freight and contingency fuel. Merely reducing passenger numbers may thus be expected to reduce the carbon footprints of individual flights.
Such technological solutions are, however, not enough by themselves. The volume of global air traffic is too high for its environmental impact to be minimised solely through structural changes in aircraft and the use of alternative aviation fuels. Changes in the behaviour of air passengers are essential, given that a mere 3 per cent of the global population flew in 2017. Slowing the growth of air travel through reducing demand is a more realistic and achievable short-term goal. This is important when airport expansion is being subsidised through the construction of additional runways, and capacity is being further increased by investment in airport-related infrastructure as well as in building new airports. Increased airport capacity is providing a perverse incentive to further fuel an apparently insatiable demand for air travel.
Ultimately, personal choices will have to be made, including the consideration of alternatives to air travel wherever possible. As long as many flights, such as those to European holiday destinations, are so frequent and so cheap, one can hardly blame the general public for taking advantage of the available bargains, when factual information about the longer-term effects of air travel on global temperature is not readily available. It would seem, however, that attitudes are beginning to change and there is still hope for the future.
Ashis Banerjee (I last took a domestic flight, to Manchester in 2016, to travel at short notice-the quoted fare was a third of the train fare)