By Nick Triggle
BBC News Online
Dramatic licence: It won't happen like this, scientists say
Scientists, for once, are the heroes in the film The Day After Tomorrow, released in the UK this week. Those doing the real-life jobs of their film counterparts will be casting a careful eye over it.
Jack Hall is the climate scientist who warns of impending disaster in the film, played by Dennis Quaid. The North Atlantic currents which warm the northern hemisphere are in danger of slowing down, he says, but is slapped down by the vice president who says the economy is more of a concern.
In true movie fashion, Armageddon ensues with New York becoming submerged under a tidal wave, snow falling in New Delhi and the Royal Family freezing to death as the world is plunged into another ice age.
But the £70m film from Independence Day director Roland Emmerich is not all Hollywood fantasy.
Real-life Jack Halls are examining the behaviour of the Atlantic's thermohaline circulation (THC), referred to as the Gulf Stream in the film.
UK scientists from the Rapid Climate Change programme, a Natural Environment Research Council project which has received £20m funding, have just laid 22 moorings across the Atlantic and will be working with US, Dutch and Norwegian researchers to monitor the current over the next four years.
In the film, the current switches off completely, causing the freakish weather conditions.
Dr Meric Srokosz, whose research has included the study of waves and oceans, is based at the Southampton Oceanographic Centre, a joint venture between the University of Southampton and the Natural Environment Research Council.
Dr Meric Srokosz says the film's scenario is "a possibility but very unlikely".
"We are expecting to see some evidence of change to the current but at the moment models show that it could be anything from no change to a complete shutdown. We need to get a clearer picture."
He says there are three main factors which could cause a significant slowdown.
"Greenland is melting which would lead to more fresh water and we may also see more rainfall with the warmer atmosphere caused by global warming.
"There is some evidence that more fresh water is flowing into the Atlantic from Siberian rivers."
Dr Srokosz also believes the film portrays the relationship between politicians and scientists accurately.
"The vice president does not listen to Jack Hall because he is too concerned about the economy. That has a ring of truth about it.
"And there is one scene where Hall stands up at a conference to express his concerns but says he cannot guarantee what will happen. That is the sort of thing I would do."
The film has also attracted praise from Sir David King, the government's chief scientist, who after seeing the movie at a private screening earlier this month, said he welcomed it because it focused public attention on climate change.
But Dr David Viner, senior research scientist at the University of East Anglia's Climatic Research Unit, one of the leading institute's on climate change, remains less sure.
Dr Viner has written numerous publications on climate change and its effects, including Global warming: the world heats up.
While acknowledging the movie does raise awareness about the issue, he says the North Atlantic current will have negligible impact on the climate and global warming was "more of a concern".
The film also stretches reality by showing the climate change over a matter of days rather than decades.
Research by the Met Office's Hadley Centre for Climate Prediction and Research has predicted that if the current does shut down temperatures would fall by 5C in a decade or two.
While that may not seem much, the difference between the medieval warm period when vines were grown in England and the mini ice age in the mid 1600s was only 1C to 2C.
Dr Richard Wood, a climate scientist at the Hadley Centre, has carried out experiments into how climate change will affect the north Atlantic current.
Dr David Viner says global warming is more of a concern
Indications are that the north Atlantic current will slow down by 20% by the middle of the century but this will be more than offset by global warming.
Dr Wood says: "A small temperature fall would have huge consequences. You would have severe winters and the summers would also be significantly cooler.
"The knock-on effect would be felt in agriculture, and rainforests would become shrub land. But as for the tornadoes and tidal waves, that is artistic licence."
What is more, if the north Atlantic current was to stop, there would be no guarantee it would reverse itself as it has done in the past, says Dr Wood, whose team will be involved in interpreting the data collected by the Rapid team.
As temperatures began to rise at the end of the last real ice age 13,000 years ago, the north Atlantic current stopped as ice sheets melted, causing a dramatic increase in the freshwater supply. The blip righted itself over time and the ice age was eventually left behind.
As a future THC slowdown would be related to global warming, Mr Wood says: "You would want to reduce greenhouse gases in the atmosphere, but this would not necessarily mean the circulation would turn on again."
A never-ending cold snap? Now that is certainly something from a disaster movie.