Geoffrey Lean: How Rupert Murdoch saved the planet (and other tall stories)

Will Rupert Murdoch and Jake Gyllenhaal together save the planet? It seems an unlikely pairing, and an even less likely prospect. But environmentalists and top scientists are predicting - at some risk to their reputations - that the septuagenarian mogul and the teenagers' heartthrob might just pull it off.

They are pinning their hopes on next week's launch of the latest Hollywood blockbuster, The Day After Tomorrow. Released by Murdoch's Twentieth Century Fox and starring Gyllenhaal, the film depicts global warming plunging North America and Europe into an ice age during the course of a single storm after global warming shuts down the Gulf Stream.

A 100ft tidal wave slams into New York, and then submerges the city in ice as temperatures fall catastrophically. A tornado devastates Los Angeles and helicopters (and their crews) freeze solid over Scotland as they fly to rescue the Royal Family from Balmoral.

The special effects are stunning, the story - as Gyllenhaal's scientist father sets out to rescue him - schmaltzy. Predictable visual plugs for Murdoch's Fox and Sky news channels are interspersed with surprisingly radical political comment.

The villain is a United States vice-president with a striking resemblance to Dick Cheney, one of the architects of America's obstruction of international action to combat global warming. He recants after an evacuated US government is given refuge in Mexico in return - a nice touch this - for cancelling Latin America's debt.

The environmentalists and scientists hope that the film will wreak a similar change of heart in real life, by raising public concern about global warming, particularly in middle America. But they are putting their faith in a lie.

For the film is scientific bunk. As one of Britain's top climatologists, Professor Mike Hulme of the University of East Anglia, points out, some of its key events defy the laws of physics.

Worse, it blurs the line between truth and falsehood in an issue desperately in need of greater public understanding, Global warming, as Tony Blair said last month, is indeed "the most important issue that we face as a global community". And, as this newspaper has reported for years, it could just possibly so weaken the Gulf Stream that Europe (though not North America) could switch to a very much colder climate - but in a decade, not overnight.

To confuse matters further, the film opens with a real event - the break-up of an Antarctic ice sheet - and gives an accurate explanation of how the Gulf Stream could be weakened before lunging into the scientifically impossible.

None of this bothers the film-makers. Michael Molitor, the film's "scientific adviser" says, with more than a touch of arrogance, "This film could actually do more in helping us move in the right direction than all the scientific work and all the [US Congressional] testimonies put together."

The makers - no doubt with an eye to the publicity - have urged campaigners to take advantage. Greenpeace is duly putting up posters linking the film to their boycott of Esso, the oil firm leading resistance to global action. Future Forests and the Royal Society for the Protection of Birds are also obliging.

More surprisingly, distinguished scientists in both Britain and the United States - normally so quick to jump on the slightest simplification - seem happy to forgive the film's gross distortions. Last Wednesday, a panel headed by Professor Sir David King, the government's chief scientist - while pointing out the film's inaccuracies - studiously avoided criticising it or expressing any disappointment or concern.

Sir David said: "I welcome the movie in the sense that it raises the profile of a critically important public debate about global warming, and the need to persuade governments to take action now."

The scientists and environmentalists are understandably desperate to exploit any opportunity to make progress on the issue. But they are entering dangerous territory. For they risk linking their credibility with that of the film, and turning it from harmless hokum - such as Godzilla or Independence Day - to a liability to their cause.

How, for example, will they now be able to raise concern about real, but quite different consequences of global warming? A devastating seven-year drought is gripping the western states of America, cause enough to spur action. But how can they credibly link this to climate change, if they help fix in the public mind that its effect would be to cause an ice-age in New York?

And how will they answer the filmgoers' question: could the events depicted really happen? The short answer is "no". How many of the questioners will wait for the longer explanation that global warming is important, but the most likely effects will be very different? Will they not just cross the issue off their worry list? As climate scientist Bogi Hansen says: "People tend to react in the opposite direction when they find something is not true."

Certainly the well-funded contrarian lobby will exploit this. The scientists have welcomed a lie, it will say, so they cannot be trusted on global warming at all. The contrarians have used such unfair tactics in the past, and are already beginning to seize this unexpected opportunity.

The scientists reply that none of this matters because the public can tell the difference between fiction and real life. But they cannot have it both ways. If filmgoers discount the film as fantasy, why back it in the hope that it will persuade cinema audiences of the importance of climate change?

The scientists' naivety may well surrender hard-won ground. Opinion polls consistently show that 70 to 80 per cent of Americans disagree with their government on global warming. This pressure is already forcing even Republican states to take action to curb the pollution that causes it, and is rapidly shifting opinion in Congress. Why risk undermining its credibility now?

I may, of course, be wrong. I hope so. But I fear that after recklessly jumping on Mr Murdoch's money-making bandwagon the scientists and environmentalists will find they are riding a tiger - and Esso's tiger at that.