The Live Earth concert was worthwhile, because it provoked this splendid argument from a columnist in The Sun, who insists the climate isn't changing - "Global warming is simply the new way of screwing more and more taxes out of us." So it turns out all those scientists and weather people and botanists and people measuring glaciers have made it all up so the Government can propose a twelve quid long-haul airline tax. There's probably a secret group in Greenland hacking icebergs to bits with a shovel to make it look more convincing.

Next week he'll add: "And what about these so-called 'sound waves'? Have you ever seen one? Of course not, because they're simply another scam dreamed up by the BBC so they can charge us a license fee." This is the level of debate offered by those who dispute global warming is happening. Either that, or they repeat some snippet they've seen on a website, like: "What about the Montana Institute of Snow, eh? They analysed nine different snowflakes in the Andes and concluded flakes are bigger now than in the olden days, so although there are less flakes, there's 80-per-cent more snow in total than ever before, and the man who does the graphs to say there's global warming is being paid by a cycle shop in Taunton."

Even this would be more convincing than the theory of Johnny Ball, who for some reason has become one of their media spokemen, and who cornered me for half an hour, during which time he said with great conviction: "Do you know what causes more global warming than anything else? The methane from spiders." The little buggers. I bet they're using coal-powered webs, with not a thought for the environment. And instead of hanging from beams in sheds, they're flying round garages in Boeing 757s they've had built by bees.

One thing the spiders should be ashamed of is their effect on the islands of Kiribati, some of which have been sunk by rising sea levels, forcing the population to flee. Or maybe that was caused by condensation. The Sun columnist would go round and say: "Aah, I say what's happened here - someone's had the kettle on."

The other main point of the sceptics is that Al Gore is a pompous politician who flies everywhere himself. Which is true, but this has little bearing on whether the climate is changing. You might as well say, "Isaac Newton was a right scruffy bastard. And yet you expect me to believe in gravity?"

Some of the science is confusing and uncertain, so one way to judge it is to look at who's on which side of the argument. The Intergovernmental Panel on Climate Change report was made by 600 scientists from 40 countries, assessed by 600 reviewers, and agrees this is happening. Whereas most of the stuff that contradicts it can be traced back to websites that aren't entirely neutral. For example, one leading source for the "global warming's a myth" supporters is called "Friends of Science" - except their president admitted: "About one third of the funding for the Friends of Science is provided by the oil industry." Yet this stuff is repeated round the world by columnists as fact.

Exxon has spent millions of dollars on a website that disputes global warming. Or there's the publication called 21st Century Science and Technology, which claimed that 55 per cent of glaciers are actually growing at the moment. But this paper turns out to be owned by an American millionaire by the name of Lyndon Larouche, who has also claimed the British royal family is running an international drugs syndicate. Nonetheless, he's been quoted by global warming sceptics, including David Bellamy.

Johnny Ball, David Bellamy - why does this affliction seem to target 1970s TV presenters? Soon Frank Bough will announce that global warming is caused by cyclists, because they disrupt the path of flies who then whizz about more erratically, making themselves a more difficult prey for spiders, who have to move faster to catch them, causing methane mayhem.

Apart from TV presenters, opponents of the scientists seem to be supporters of the oil companies, or people who believe they're standing up against a woozy liberal agenda. Because the PC mafia are forcing us to burn our cars and buy tandems and not go on holiday, while the only people resisting this are the downtrodden voices of the petro-chemical industry, the airlines, and the government of America.

So they're not interested in the science at all. When they were at a chemistry class in school, and the teacher announced that the litmus paper had turned red so vinegar must be an acid, they probably shouted: "Oh what do you know? I suppose now we'll all have to campaign to save alkalines from extinction will we?"

Live Earth may have brought the scale of the climate problem to people's attention. But it can't be resolved without confronting those giant companies and governments in whose interest it is to deny the problem is there at all.

For example, to reduce the number of cars, we could invest in a re-nationalised public transport system, which would upset the private rail firms and the car firms. And it would upset the people who complained that Live Earth "only put one point of view". They'll probably also complain the coverage of the Tour de France "only puts one point of view," as there should be someone else saying: "They can't have gone all that way, they'd have tipped over the edge."

(Por Mark Steel, The Independent, 11/07/2007)