4. Ban CFCs Chlorofluorocarbons have achieved fame as the cause of the thinning of the ozone layer. But they also form a potent greenhouse gas, 20,000 times more efficient at trapping heat than CO2. These synthetic chemicals cause about 25 per cent of global warming and their use is increasing at about six per cent yearly. They should be outlawed as quickly as possible.

Can science save us?
Fred Pearce describes the frenzied scientific search
to find a magic cure for global warming.

'How to solve the carbon dioxide problem without tears' was the name of a paper at a 1988 Moscow conference. The idea was to use nuclear power to turn Siberian natural gas into hydrogen - which would then partly replace fossil fuels like coal and oil. The result: cleaner energy, no carbon dioxide (C0₂) and no greenhouse effect.

It seems every scientist is chasing a 'technical fix' to shut down global warming. Last summer a Swiss physicist published details of how a giant aluminium mirror put into space could reflect some of the sun's heat away from the earth's surface, so keeping us cool. It would have to be a big mirror, of course. One about 20 times the size of Britain would keep us going for a few decades. It would cost about as much as the world currently spends on 20 years' worth of armaments.

Somebody else said it would be easier to reflect the sun's heat back from the surface of the earth. Trillions of white polystyrene balls floating on the world's oceans might do it. Or we could paint the deserts white.

Geologists rake a different tack. There is (very expensive) technology available to remove CO₂ from the chimneys of power stations and convert it into liquid carbon dioxide. We could then bury the liquid into old coal mines or oil wells or pour it into sinking ocean currents that would take our pollution into the sea bottom. Scientists have drawn up maps of vast networks of pipelines spreading from the world's industrial centres to coastlines in order to accomplish this task. It might double the price of electricity, they say.

Biologists get in on the act too. One of nature's own methods of recycling CO₂ from the air is to absorb it in the oceans, where it feeds the growth of algae. Up to half the carbon dioxide that we put into the atmosphere today quickly ends up in the oceans. Why not help the process along? In some parts of the oceans, the growth of algae seems to be limited by the amount of iron in the water. So we could sprinkle iron filings on the sea and see what happens.

Another idea that popped up recently is to build giant lagoons along the world's coastlines, where algae could be intensively farmed: 220,000 square kilometres of lagoons would just about do it. The author suggested that it was more feasible than a terrestrial version of the same trick - planting giant forests everywhere, on the grounds that trees too absorb carbon dioxide.

All but one of the above ideas are regarded in serious circles as deeply unserious. The exception is tree planting. At the rate we are going, the world will run out of tropical forests before many decades are past. Isn't it time we planted some more? Some estimates suggest that we could damp down most of the global warming of the next half century or so with new forests the size of the US.

But watch out if you are invited to support the idea of planting lots of trees to help reduce the greenhouse effect. Vast monoculture plantations of fast-growing eucalyptus and acacia are already popping up across the tropics, sponsored by the World Bank or companies like Shell, and for entirely commercial reasons. These plantations are nothing like the real thing. They have no undergrowth, no fruit trees or dead wood or animals - none of the things that make natural forests of value to rural people throughout the tropics. Instead they have fences and guards. That is why they have inspired massive protest movements in India and, more recently, in Thailand. If we need more trees to soak up the rich world's pollution then they should be planted in the rich world.

Amid all the talk of 'technical fixes', we forget that the most obvious methods of responding to the greenhouse effect are probably the best and cheapest. One recent study of 'greenhouse solutions' by a US physics professor started from the premise that 'reducing our energy usage is not an option'. But it is. All the technology for saving energy already exists; it just needs applying. It could be brought in on schedule, with no big changes in our lifestyle - and at no real cost. But we could go even further. Why not spend the next 15 years investing in even better energy technologies; there's lots more potential in geothermal, solar and wind power.

And if we were really feeling brave, we could start thinking about bigger changes to the way we live. Like finding ways to allow people to live close to their work (thus cutting down the need for C0₂-producing cars). By comparison with grandiose scientific cures all this seems very dull. Afterwards we would probably say: 'What was all the fuss about? Why didn't we do it before?'

But it always takes a shock to change things. Only the great London smog of 1952 (when more than 4,000 people died within a week from air pollution) jolted the UK to introduce clean-air laws. Now, perhaps a few scary stories about the greenhouse effect may encourage us to do some extremely obvious things about the way we use energy.

Fred Pearce wrote Turning up the Heat: our perilous future in the Global Greenhouse. He has just finished Green Warriors, a book about the international green movement.