CANNES, France (Reuters) - The French director who charmed the world and won an Oscar with his 2005 documentary "March of the Penguins" will close the Cannes festival on a somber note with a film about global warming that says not only the penguins should be worried.
Luc Jacquet's "La Glace et le Ciel" (The Ice and the Sky), is not in competition but will be screened after the Palme d'Or winner is announced on Sunday night.
The film is a portrait of the octogenarian French glaciologist Claude Lorius who, from the age of 23, made more than 20 polar expeditions, most of them to Antarctica.
Making extensive use of archival footage, the film shows Lorius heading off on his first expedition to France's Charcot base in the Antarctic, and the hazards of working in temperatures that sometimes plunged to -90 Celsius.
It shows Lorius and his colleagues surviving the successive wrecks of two American transport planes that crashed while trying to take off in the Antarctic, luckily causing no injuries.
The film also contains an unnerving, tracking shot that starts on what looks like a vast expanse of polar ice but quickly shows the ice sagging, melting and finally rushing out from under the ice cap as a turbulent stream.
The film's message is that the earth is warming up faster than it has in hundreds of millennia.
Lorius bases this assertion on his analysis of samples obtained by drilling thousands of feet below the polar ice cap, some of them up to 800,000 years old.
From the isotopes of hydrogen in the samples, Lorius says he can determine the ambient temperature when the ice was formed.
At one point, he realized how much more information the samples contained when he put shavings of ice in his whisky and saw bubbles released -- bubbles which contained air from tens of thousands of years earlier.
The film, with its unabashedly pro-environmental agenda, ends by posing the question: "Now that you know, what will you do?"
Lorius gives his own optimistic forecast. Mankind, he says, always rises to the challenge.
Writing by Michael Roddy; Editing by Andrew Heavens