Here's a thought experiment. An evil terrorist plants a time-bomb in a school classroom. He sets the timer for six years' hence, and, in six years time the bomb duly explodes, killing and maiming a class of five-year-old children.
The terrorist would of course face universal condemnation – but was his action really wrong? When he placed the bomb, those who would eventually be harmed had not even been born. And unborn generations surely don't have rights – because if they did, we would all be forced to behave very differently, not least in terms of our greenhouse gas emissions.
It would perhaps be simplistic to use this example of the moral challenges of intergenerational equity – first posed by the late American moral philosopher Joel Feinberg – as a reason to tell people to stop flying. Aviation brings undoubted benefits: the ability to travel great distances, to stay in touch with loved ones on other continents and to see faraway parts of the world that people in the age before international jet travel could only imagine.
But what, in moral terms, is the difference? Each time we take a long-haul flight, we are personally responsible for emitting several tonnes of carbon dioxide – which will remain in the atmosphere for a century of more, warming the planet all the time, and potentially contributing to global warming so disastrous that it undoubtedly infringes the rights of future unborn generations to life and property. We would all instinctively condemn the terrorist planting the time bomb. But the climate-change time bomb we help plant every time we step on a plane is still not recognised by most people – least of all the aviation industry – as a moral issue at all.
The former Labour minister Brian Wilson, whose services have recently been bought by the aviation industry lobbying group Flying Matters, argues that "restricting people's ability to fly... will return air travel to the preserve of a wealthy elite" – an alternative appeal to morality that the industry finds convenient. But the truth is that if global warming is ever to be reined in, the growth of aviation must be stopped, as the Committee on Climate Change has recognised.
The implications are enormous. There can be no third runway at Heathrow. Even though, as the industry constantly repeats, it represents only a couple of per cent of total global emissions today, if its expansion is unchecked, it could account for up to a fifth of emissions by the middle of the century. The industry is perhaps the most unsustainable on the planet.
It is possibly because he realises this, if only subconsciously, that Ryanair's chief executive Michael O'Leary has been one of the most prominent deniers of climate change. O'Leary, who rages about global warming being "nonsense" is at least consistent, however. As a denier, he can avoid facing the moral challenge posed by his actions. Less consistent is the behaviour of executives in other airlines who claim to fully recognise the reality of climate change whilst still wanting to cause more of it.
Aviation should not be singled out for special condemnation. A tonne of carbon dioxide is the same whether it is produced by a jet engine travelling to Miami or a coal-fired power station in Germany. But other areas of economic activity can be decarbonised in decades to come. Big drives towards energy efficiency, combined with a massive expansion of renewable and nuclear, can decarbonise electricity. Heat pumps can deliver low-carbon heating and domestic hot water. Electric vehicles can decarbonise transport. But nothing can plausibly decarbonise aviation.
The use of kerosene in jet turbines will be extremely difficult to substitute technologically. Hydrogen planes will never get off the ground. Electricity, for obvious reasons, is a non-starter. The only remotely viable alternative is biofuels, which the industry is already touting as its salvation, but which raise serious questions about rainforest destruction, competition with food production and the amount of land needed. The only realistic alternative – as the Committee on Climate Change is making clear – is to constrain the expansion of aviation in general.
The industry has agreed to become part of the EU Emissions Trading Scheme, but argues that it should be given large quantities of free permits to pollute instead of having to pay for them – and the EU, shamefully, has so far agreed. The slave owners of the US south made a similar argument in the 19th-century – claiming compensation in millions of dollars for loss of property when their slaves were freed. Now we have to decide to whom the atmosphere belongs – to polluting industries, to us all, and whether it is partly also owned by future generations.
Mark Lynas is the author of 'Six Degrees: Our Future on a Hotter Planet', which won the Royal Society science books prize in 2008