These Hollywood special effects may cost the world $15 trillion, says Bjorn Lomborg

In the final minutes of the Hollywood doomsday spectacular The Day After Tomorrow, which opens in Britain at the end of the month, the US president makes a ludicrously over-the-top State of the Nation speech. It is a great deal less realistic than the performance by the undoubted star of this $125 million [€106 million :-)] blockbuster of a film: a 100 ft high tidal wave that engulfs New York. [roughly 30 meters :-)]

Indeed, the film loses any credibility long before that. This is not because of any one of the far-fetched incidents that occur in the course of its 125 minutes. It isn't the flash freezing of a presidential motorcade, or even the escape of man-eating wolves from New York Zoo. No, this extremely enjoyable film has been let down by the simple fact that it has got its science all wrong. None of it could happen.

The story goes like this. As a consequence of global warming, the polar caps melt, sending vast quantities of fresh water into the world's salty oceans. The torrent stops the Gulf Stream, a major current in the North Atlantic, precipitating a global storm that instantly creates a new Ice Age. This is an excuse for breathtaking special effects: Manhattan is buried in 30-storey snowdrifts, Los Angeles is hit by 250 mph tornadoes, [400 km/h :-)] and a fearless paleoclimatologist, played by Denis Quaid, straps on his snow shoes to trek from Washington, DC to New York to rescue his son.

The bad guy is the vice president, who bears a striking resemblance to the real one. This Dick Cheney doppelganger arrogantly dismisses the Kyoto Protocol -- it is too expensive -- and rejects concern about climate change as fearmongering. The scriptwriters save him from death only to subject him to a mea culpa public address at the movie's climax, saying roughly, "We thought that we could affect the Earth's delicate systems without suffering the consequences. We were wrong. I was wrong." This State of the Nation address is broadcast live on the Weather Channel.

If The Day After Tomorrow had no claims to be anything more than another cheesy Hollywood movie with some fabulous special effects, we could happily turn a blind eye to its bogus science and concentrate on the sight of the Statue of Liberty up to her armpits in the water. But the film claims to be offering something more than this.

"There's more truth than hype," the filmmakers promise in their publicity. The German director, Roland Emmerich, claims he tried to present us with a valuable fund of scientific information. The film's website provides links to news stories published in February about "a secret report prepared by the Pentagon" which warned that climate change would "lead to global catastrophe costing millions of lives". What this publicity does not reveal is that the Pentagon report was merely a hypothetical worst-case scenario -- and one that has already been thoroughly debunked. In fact, the respected magazine Science has reviewed this Pentagon report and the alleged scientific support for The Day After Tomorrow and concludes that "it is highly unlikely that global warming will lead to a widespread collapse" of the Gulf Stream, and "it is safe to say that global warming will not lead to the onset of a new Ice Age".

In Nature, another highly-respected scientific journal, a researcher finds that halting the Gulf Stream would be impossible, arguing that "the only way to produce an ocean circulation without the Gulf Stream would be to turn off the wind system or stop the Earth's rotation, or both."

Now, although it is not going to kill us the day after tomorrow, global warming certainly is a reality. It is caused at least partly by mankind's use of fossil fuels. The effects will be predominantly adverse -- although high-latitude nations might prosper in a warmer world, tropical countries will have to deal with more heat-days, altered precipitation and higher sea-levels. So what is wrong with using a piece of popular entertainment to campaign for action to save people from that? As the Nasa research oceanographer William Patzert says: "The science is bad, but perhaps it's an opportunity to crank up the dialogue on our role in climate change."

The problem is that if we overestimate the risk that climate change poses, then we will pay less attention to the other challenges that face us. That appears to be exactly the aim of the movie's creators. Emmerich believes that global warming is "the only problem big enough to force all the countries of the world to stop fighting and work together to save the planet"; he says that his great dream is that "this film will force politicians to act".

If politicians were to see The Day After Tomorrow and act on its agenda, what would happen? Implementing the Kyoto agreement on climate change would cost at least $150 billion [€127 billion :-)] each year, yet would do no more than postpone global warming for six years by 2100. That is to say, it would cause temperatures to increase slightly more slowly -- the temperature we would have reached in 2100 without Kyoto, we would now reach in 2106. Those families in Bangladesh who will get flooded will have an extra six years to move. Even if the film's creators are right -- and the scientists are wrong -- and the Gulf Stream current does collapse within a decade, then Kyoto would have made no difference.

There is another reason why it is wrong -- I would even say amoral -- to overplay the case for combatting climate change. We cannot do everything. Our resources are limited, and our attention is quickly diverted from one fashionable cause to another. We must ask ourselves if spending $150 billion every year for the rest of the century to postpone warming for six years is really the best use of that money.

For the cost of implementing Kyoto in just one year, we could permanently provide clean drinking water and sanitation to everyone on the planet. Of course it is unlikely that Emmerich will cast Brad Pitt as a sewage engineer in Kenya for his next glamorous movie. Nor are there many good plotlines to be made from tales of a government which invests in malarial vaccines, or of a global conference called to remove trade barriers. But these are real options that policy-makers face every time they spend a dollar with the intention of easing human suffering.

The world needs a rational basis for making such priorities. That is the aim of a new project, Copenhagen Consensus, which will bring together nine economists -- including four Nobel Prize winners -- to prioritise solutions to 10 great challenges facing humanity. They will look at problems ranging from financial instability to communicable diseases, examining several different solutions to each challenge. The experts will produce a ranked list -- at the top will be the solution that will achieve the most for humanity.

In an ideal world, we would be able to achieve everything -- we should halt global warming and eradicate corruption, end malnutrition and win the war against communicable diseases. Because we cannot do everything, we need sound reasoning and high quality information to defeat the hysteria of Hollywood. I believe there is more hope in truth than in hype.