单项选择题

All big ideas start life on the fringes of debate. Very often it takes a shocking: event to move them into the mainstream. Until last year interest in climate change was espoused mainly by scientists and green lobbyists -and the few politicians they had badgered into paying attention. But since Hurricane Katrina, something seems to have changed, particularly in America.
There are plenty of anecdotal signs of change: Britain’s pro business Tories have turned green; AI Gore is back in fashion in America. Companies are beginning to take action and encouraging governments to do the same. Europe already has an emissions trading system (ETS) for its five dirtiest industries. In America, although the Bush administration still resists federal legislation, more and more states do not.
So far the political rows about global warming have centered on two polluters, smoggy factories and dirty cars. Next month the European Parliament will vote on whether to extend its emissions trading system to airlines. If it decides in favor, the whole industry will feel the impact, for it will affect not just European airlines but all those that fly into and out of the EU. Talk about this prospect soured the International Air Transport Association’s annual meeting this week in Paris. But whatever happens in the EU, the airlines look set to face vociferous demands that they should pay for their emissions.
In. some ways, the airlines are an odd target for greens. They produce only around 3% of the world’s manmade carbon emissions. Surface transport, by contrast, produces 22%. Europe’.,, merchant ships spew out around a third more carbon than aircrafts do, and nobody is going after them. And unlike cars -potent symbols of individualism -airlines are public transport, jamming in as many people as they can into each plane.
What’s more, many air travelers cannot easily switch. Car drivers can hop on the train or the bus, but transatlantic travelers can’t row from London to New York. Nor can aircraft fuel be swapped for a green alternative. Car drivers can buy electro petrol hybrids but aircrafts are, for now, stuck with kerosene, because its energy density makes it the only practical fuel to carry around in the air.
Yet in other ways, airlines are a fine target. They pay no tax on fuel for international flights, and therefore escape the "polluter pays" principle even more niftily than other forms of transport. Their emissions are especially damaging, too -partly because the nitrogen oxides from jet engine exhausts help create ozone, a potent greenhouse gas, and partly because the pretty trails that aircrafts leave behind them help make the clouds that can intensify the greenhouse effect.
Slowly, businessmen and politicians are coining to agree with scientists. If this generation does not tackle climate change, its descendants will not think much of it. That means raising costs for all sources of pollution. Even those deceptively cheap weekend breaks cannot be exempt.
The author says that airlines are a good target because