The end of the world as we know it

HAILSTONES the size of grapefruit rain down on the streets of Tokyo, leaving dozens of commuters dead and dying. Hurricanes batter Hawaii, snow falls in New Delhi, tornadoes devastate Los Angeles, ripping up the Hollywood sign, and a freak storm in Scotland sees the temperature drop to minus 150 degrees.

In New York, a vast tsunami floods the city, and ocean liners sail between the skyscrapers. And then the snow and ice arrive. Global warming pushes the planet into a new Ice Age.

Twentieth Century Fox's last disaster movie was Independence Day in 1996, but there was no widely-held belief that an alien invasion was imminent. Eight years on, The Day After Tomorrow describes a scenario which some scientists believe could well happen. Not so much science fiction, as just science.

Around 8,000 years ago, a dam of ice in north-eastern Canada burst, releasing millions of gallons of meltwater into the North Atlantic. According to some experts, the result was a 200-year Ice Age, which saw man flee northern Europe in search of less hostile territory.

And it's a similar phenomenon which drives the apocalyptic scenes of The Day After Tomorrow. Climatologist Jack Hall, played by Dennis Quaid, witnesses a huge glacier break off the Antarctic Ice Shelf. The melting polar ice caps pour too much fresh water into the oceans and disrupt the currents which stabilise our climate, setting in chain a rapid sequence of events culminating in snow drifts covering Manhattan.

"We pushed the time period in which an Ice Age could occur for dramatic purposes, but the theory that global warming could cause an abrupt climate shift is gaining mainstream attention," says the film's producer Mark Gordon. "While nobody knows what the exact result will be of mankind's addition of carbon dioxide into the atmosphere, some experts have referred to it as 'the largest uncontrolled scientific experiment in history'."

The film-makers point to an increase in extreme weather in recent years as evidence there is nothing far-fetched about this movie. Hailstones the size of eggs killed 25 people in China during pre-production in July 2002; in August, floods hit Central Europe, leaving the Prague metro underwater; in November, just days after principal photography began, 75 tornadoes touched down in the US in one day, leaving 36 people dead.

Perhaps most eerily of all, in March 2002, the Larsen B ice shelf in Antarctica fell into the sea. "At that time we joked that we had better start shooting soon or we'd be making a documentary," says director Roland Emmerich, who also helmed Independence Day.

Although the struggle of man against the elements is common to most disaster movies, what marks The Day After Tomorrow apart is the plausibility its creators are investing in the film.

"At the core of any disaster movie there always has to be something factual, something real for the audience to grab onto," says Emmerich, who also co-wrote the screenplay. "What we already know about global warming and climate change has provided us with a great fact base for the movie and that directly affects the believability of the characters and the world we have created for them."

But Chris Kilsby, a lecturer in climate change at Newcastle University, while welcoming the chance to air the subject which the film affords, is less enamoured of the science behind the celluloid, and not just because it might be seen as too sensational, and therefore crying wolf.

"There are no certainties about future climate change, and anyone who tells you otherwise is a charlatan. However, some future scenarios are rather more likely than others," he says.

He says the basis for the Ice Age in the film is the collapse of the thermohaline circulation in the North Atlantic. This circulation, of which the Gulf Stream is a part, drives the warm water currents, and keeps north-western Europe warmer than it should be, given its latitude, which is the same as Newfoundland in Canada.

If this circulation weakens and eventually breaks down, with the influx of fresh water from the ice caps, then there will be a marked lowering of temperatures, with the UK particularly vulnerable.

But, while Mr Kilsby says this scenario can't be ruled out, and is thought by some to have actually happened thousands of years ago, the consensus among the scientific community is that not only is it unlikely, but that the opposite is generally thought to be more probable.

In this alternative future, global warming sees the atmosphere become warmer, and thus able to hold more water vapour. This, in turn, allows the possibility of increased rainfall and evaporation. The result of the increased fluctuation of water vapour in the atmosphere is that the extremes of weather conditions will be further apart. For the UK, this means more floods, but more droughts; wetter winters, but drier summers. More energy in the atmosphere also means more storms.

'The other issue I have with the film is that it is rather like Inspector Morse, where everything is compressed and exaggerated," Mr Kilsby says. "There couldn't possibly be that many murders in Oxford, and there couldn't possibly be that many weather events happening at once.

"Allowing for that, pretty well all the events that are depicted could happen, somewhere at some time, although they're not going to happen in close proximity, as in the film.

"The volume of water and inertia in the oceans mean they take many months or years to change, but hailstones large enough to cause injury do happen; we already have tidal waves; we already have hurricanes - they just don't happen very often. I don't think they have gone beyond the bounds of possibility with this stuff."

As to when it will happen, he says the majority scientific opinion is that the levels of carbon dioxide in the atmosphere will double by the end of the century. But while the maximum effect of global warming will be felt in 100 years time, it is cumulative: the world is already warming up, with a half a degree temperature rise in the last century, and another two or three degrees to come. Another unknown is whether the changes will be gradual, or whether there will be a rapid readjustment to the temperature rise.

But while governments have been slow to respond to the danger, it is not in their hands alone. According to the Energy Saving Trust (EST), a quarter of carbon dioxide emissions comes from the energy we use at home.

EST chief executive Philip Sellwood says: "Climate change is a reality - just last year, the UK experienced an unprecedented combination of record temperatures, tornadoes and flooding. Despite these clear signs, most people are still not acknowledging the effect their actions are having on the environment.

"We hope that The Day After Tomorrow will help to break consumer apathy towards climate change. Even if we can get a small number of the film's audience to make the link between climate change and what they do in their day-to-day lives, then this will be a big achievement."

This is a sentiment with which Mr Kilsby would concur. For all the film's scientific flaws, it does have the merit of highlighting an issue which is too frequently ignored, and ignored maybe not at our peril, but at least at our children's.

"It is raising awareness of the likelihood of climate change, which will affect the way we live and which will bring danger," he adds. "Any publicity is good publicity for climate change. We can't prove how dangerous that change could be, but we need to plan for it now."

* The Day After Tomorrow opens in cinemas on Thursday and will be reviewed next week's 7DAYS entertainment supplement.

* Tomorrow, Five hosts Survival Sunday, a series of films and documentaries about natural disasters, including The Poseidon Adventure, Armageddon and Global Storming: The Making of The Day After Tomorrow.