"An Inconvienent Truth" is a documentary about Gore's slick one-man "travelling global warming show" which he has taken to some 1,000 schools and conferences around the United States.

Backed with graphics, facts and figures some dating back 650,000 years, and even a Bart Simpson-style cartoon short, Gore wittily and engagingly explains the dangerous path which the planet is pursuing.

Computer-generated graphics even show rising sea waters creeping up Manhattan and swamping the World Trade Centre memorial site if the Greenland ice cap melts, or flooding vast areas of The Netherlands, China and South Asia.

His slide-show is interspersed with family photos, a trip to the family farm, and a moving account of how he was forced to re-examine his life when his six-year-old son nearly died in a road accident.

Even the dimpled chads in Florida polling stations which conspired to rob him of the presidency in 2000 make an appearance, as Gore admits that his defeat by George W. Bush was "a hard blow."

Gore hopes the 98-minute film directed by Davis Guggenheim, which is being shown out of competition here, will inspire action among those who have so far failed to grasp what he calls "the biggest moral challenge facing our global civilisation."

"Mother Nature has joined this debate with a very powerful and persuasive voice," Gore told a news conference, referring to the increasing spate of natural disasters such as Hurricane Katrina last August.

"The key to solving this crisis depends upon the people demanding action and not just of a president, but of the Congress as well."

Until recently, he said, the people in the US had been living in a bubble of unreality.

"But I believe that as more citizens understand the gravity of this planetary emergency they will by much more forceful in insisting that politicians respond to it," he said.

Meanwhile, the jury was watching two films by women directors in the official competition.

"Red Road" by British director Andrea Arnold is the only film to be competing for both the Palme d'Or and the Camera d'Or, which is awarded for the best first full-length feature.

Arnold's intriguing movie is part of an innovative approach to film-making involving three directors writing stories around the same nine characters.

The only rules are that all of the characters must appear in all of the films, and the films have to be set in Scotland. The two other films are still in production and are set to be completely different in tone.

In the first film a CCTV camera operator monitoring dozens of surveillance cameras trained on a rough Glasgow estate spots a man linked to the deaths of her husband and daughter, and starts to track him.

The story unravels slowly against the bleak background with audiences not quite certain just why Jackie, played by Kate Dickie, is so compelled to follow the man, or what she is searching for, until the end.

It provides a chilling glimpse of our "Big Brother" society.

"I've been fascinated with it for quite a while, wondering who's behind the cameras and who's watching. And they are amazing, they can zoom into your handbag," Arnold, director of the Oscar-winning short "Wasp", told a press conference here.

"I used to find it very creepy, but having been in the centre and realise how much the people care and are trying to help I feel very torn," said Dickie.

But the cast all agreed that they had since modified their behaviour when out in the streets for fear of the "eye in the sky."

"It's strange having that awareness as I think most of the population don't understand how intense the cameras are in Glasgow ... and how close they can see. It's quite unsettling," said Dickie.

"Charlie Says" by French director Nicole Garcia was also to be seen by some of the 4,000 accredited journalists among the 30,000 industry professionals attending the 59th festival.

The film, billed as three days and seven lives, takes place in a town on France's Atlantic coast, out of season.

With the festival still in its early days, critics are keenly awaiting "Marie Antoinette" by US director Sofia Coppola, set to be screened in the coming week, which is already a hot favourite here, along with Spanish director Pedro Almodovar's hauntingly seductive "Volver".

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