填空题 All big ideas start life on the fringes of debate. Very often it takes a shocking event to move them into the mainstream. Unti1 last year climate change was mainly the interest of scientists and green lobbyists. But since Hurricane Katrina, something seems to have changed, particularly in America. Nobody knows whether the hurricane really had anything to do with the earth warming. But for the first time less green voters and big business had a clearer idea about the "extreme weather events" whose increasing frequency scientists had been talking about.
There are plenty of anecdotal signs of change: Britain's pro-business Conservatives have turned green; A1 Gore is back in fashion in America; hybrid cars no longer get stared at. (41)______.
So far the political rows about global warming have centred on two polluters, smoggy factories and dirty cars. (42)______.
In some ways, the airlines are an odd target for greens. They produce only around 3% of the world's man-made carbon emissions. (43)______. By shipping hordes of ordinary people around the globe for not very much money, they have improved the lives of millions.
(44)______. Air transport will soon be central, not marginal, to the emissions issue.
What, if anything, should be done? As usual, there are dangers on both sides. Excessive regulation would unnecessarily restrict individual choice and restrain an industry that makes both rich and poor countries better off. On the other hand, airlines no less than any other industry must pay for pollution.
(45)______. And, although other forms of transport cannot easily replace flying, demand for many flights is sensitive to price. A quarter of flying is business-related; many of those journeys are essential, but others are scarcely more important than a telephone call or video-conference.
However, addressing individuals' consciences won't go that far. Air pollution is a collective problem, which in this case requires a change in policy. As it stands, the market is in favour of air travel; the aim should be to make it more balanced. Two approaches are on offer. Some think the best way to limit emissions is to tax them; others argue for a system that sets a cap on pollution, and let polluters trade the right to emit.

[A] But there is no sign of governments embracing that idea. Given that it is the world's first serious attempt to cut emissions internationally, that is not surprising. The world can learn from its imperfections, and design a better scheme for airlines.
[B] Now a new front is being opened up—in the skies. Next month the European Parliament will vote on whether to extend its emissions-trading system to airlines. If it decides in favour, 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. But whatever happens in the EU, it seems that the airlines are bound to face demands that they should pay for their emissions.
[C] Slowly, businessmen and politicians are coming 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 inexpensive weekend breaks will be cancelled.
[D] As the debate grows, some flyers may reconsider their ways. Put frankly, air travel makes a mockery of many people's attempts to live a green life. Somebody who wants to reduce his "carbon footprint" can bicycle to work, never buy sprays and turn off his air-conditioner—and still blow away all this virtue on a couple of long flights.
[E] Companies are beginning to take actions 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.
[F] 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. Their emissions are especially damaging, too, And the industry's energy consumption has been growing faster than that of other polluting industries.
[G] Surface transport, by contrast, produces 22%. Europe's merchant ships spew out around a third more carbon than aircraft do, and nobody is going after them. And unlike cars— potent symbols of individualism (and, some would say, individual selfishness) — airlines are public transport, jamming in as many people as they can into each plane.