LONDON, 9 May 2004 — It begins with a chunk of ice the size of Scotland falling into the Antarctic Sea. At breathtaking speed it develops into hailstones as big as grapefruit battering Tokyo, hurricanes pounding Hawaii, snowstorms in New Delhi and tornadoes whipping through Los Angeles.

Welcome to “The Day After Tomorrow”, the latest Hollywood blockbuster, which depicts climate change as a dramatic series of disasters sweeping across the world in a maelstrom of appalling weather.

A sudden shift in the warm waters of the Gulf Stream sends temperatures in New York and London instantly plummeting to well below zero, causing the sort of ice age not seen for thousands of years.

The makers insist the film, starring Dennis Quaid and Jake Gyllenhaal, is based on genuine science, but climate researchers have questioned its accuracy and have criticized the way it represents the speed and manner of climate change.

Critics say that the film is seriously misleading and could cause the public to be become inured to the genuine threat posed by climate change when they see it being trivialized by the same Hollywood director who made Independence Day.

But the science adviser behind the movie has hit back at its critics, arguing that The Day After Tomorrow, due for worldwide release on May 28, will do more to raise the public awareness of the greatest environmental issue of our times than any number of scientific research papers and worthy documentaries.

Michael Molitor, a former academic and climate change consultant, said that he has already received more media interest from his connection with the film than at any time in his 20 years of working away on the science and politics of global warming.

“The amount of commentary by climate scientists on this film has been unbelievable and I find it almost comical,” Dr. Molitor told The Independent.

“This film could actually do more in helping us move us in the right direction than all the scientific work and all the (US Congressional) testimonies put together,” he said. The Day After Tomorrow is set some time in the not-too-distant future and is based on the idea that global warming could trigger a sudden and dramatic change in the planet’s climate system.

Roland Emmerich, the film’s director, has chosen a sudden collapse of the Gulf Stream and the huge body of heat — equivalent to the combined output of 27,000 power stations — that it carries from the Caribbean to the northeast coast of America and Western Europe.

Oceanographers know that the Gulf Stream relies on a second, deep-water current running in the opposite direction along the seabed creating a “conveyor belt” driven by the sinking of cold, salty water in the northeastern Atlantic, a phenomenon called thermohaline circulation.

But this engine for the Gulf Stream could in theory be interrupted by the melting of the Greenland ice sheet as it pumps huge volumes of freshwater into the Atlantic, watering down the salinity and hence density of the surface water.

“A change in the thermohaline circulation in the North Atlantic is one of several abrupt climate change scenarios that we have some familiarity with,” said Dr. Molitor.

“There’s some disagreement about the probability but the fact that that link has been made is quite accepted. On that level the film is accurate.

“Where the film departs from our knowledge is where the changes in the story occur on a timescale that’s probably faster than we expect,” he said. When climatologists talk of sudden changes they usually mean alterations over a period of decades or even centuries, but this is far too slow to sustain the pace of a Hollywood film, he said.

“No one has ever made any public claims that this film is completely accurate. This is entertainment,” said Dr. Molitor. It is possible to sacrifice scientific accuracy to reach a wider audience, he argued.

“Look at the tradeoff. If this film was strictly accurate in terms of the science it probably wouldn’t be very successful commercially,” he said. “The tradeoff is between a significantly more accurate film that would depict a more accurate story that is only seen by a million people, or a film with a more exaggerated storyline that is seen by 500 million people,” he added.

Other scientists, however, are not convinced. Dr. Bogi Hansen, an oceanographer at the Faeroese Fisheries Laboratories, who monitors the thermohaline circulation, said that exaggerating the effects of global warming could lead to a public backlash.

“I don’t think it’s justifiable because you lose credibility and people tend to react in the opposite direction when they find something is not true. They then say ‘there’s no problem’,” said Dr. Hansen, who has yet to see the film. Other scientists, including Sir David King, the UK government’s chief scientific adviser, and senior figures in the Met Office have been invited to a special private screening next week in London to make up their own minds. Meanwhile, in America reaction within the scientific community was initially muted. The New York Times revealed that climatologists within the US National Aeronautics and Space Administration (NASA) had received an official instruction not to comment on the film for fear of upsetting the White House, which is famously skeptical of climate change.