And in the air

The short answer generally is try not to fly if you can avoid it. A new movement is starting up of people who refuse to fly, not through personal fear, but because of fear about what all those aircraft are doing to the atmosphere. Short-haul flights typically produce as much carbon dioxide per passenger per mile as a car with one occupant, though long-haul flights are a bit better. A trip from London to New York and back emits as much as a typical car driver does in a year - about half a tonne of carbon.

Air travel is the fastest-rising source of greenhouse gases. Unfortunately, cheap flights mean the price incentives are ridiculously strong. We are currently living in a 'golden age' for air travel. Unlike other transport fuels, kerosene fuel for aircraft carries no taxes. International law forbids it. And air emissions fall outside the Kyoto Protocol, so no government has any incentive to curb flights. Britain, as a major air hub as well as a pioneer of cheap air travel, is particularly culpable. The reductions in greenhouse emissions that we have made since 1990 would be wiped out at a stroke if aircraft emissions were included.

It is true, as they argue, that cheap-flight operators work hard to fill their planes. So the individual carbon footprint of each passenger is less because the emissions are shared out among more people. But that cannot get round the fact that weekend breaks across Europe are a major new source of greenhouse-gas pollution.

It seems almost certain that this 'golden age' will soon end. Europe already wants to include aircraft emissions in its new carbon emissions trading scheme, and the next phase of the Kyoto Protocol is likely to cover aircraft emissions. So air fares will rise steeply eventually.

But if you care about the climate don't take advantage of the current free-for-all. Ask: Is that business trip really necessary? How about taking that weekend break - or buying that second home, come to that - in the UK rather than eastern or southern Europe? Why not travel to European destinations by train? You'll see much more of the countryside. If you do fly, take the advice of the more ecologically-minded travel guide publishers. Take full advantage of the trip and stay longer.