Cannes (France) (AFP) - The Cannes Film Festival's closing film on Saturday was a call to arms to tackle climate change featuring the scientific pioneer who spent decades in Antarctica proving the existence of global warming.

"I used to be pessimistic, but I think people are changing," said Claude Lorius, the 91-year-old French scientist whose groundbreaking research on ice cores proved the link between greenhouse gases and global temperatures.

His story is told in the documentary "Ice and the Sky", featuring footage from his earliest missions in the 1950s through to the present day.

Lorius carried out 22 expeditions -- some lasting as long as a year -- in Antarctica, where he helped pioneer the drilling and examining of ice cores, gathering climatic data going back more than 400,000 years.

One of his key insights, described in the film, came from drinking whisky one day with colleagues. Watching ice crack in the glass made him realise he could extract ancient air bubbles from the ice samples they were collecting.

"I'd already had a bit to drink, otherwise I wouldn't have had this brilliant idea, this brainstorm," Lorius told reporters after the screening. "It took many years to put the ideas into practice."

Director Luc Jacquet said the world had made "fundamental progress" in understanding the problem of climate change.

"When Claude published his paper 30 years ago, the concept didn't even exist, it was hard to drum this idea into people's minds," said Jacquet.

"But people are now aware of the problem and impatient to see results."

Lorius said he was looking forward to progress at the next global climate conference being held in Paris in December.

"We expect a lot from the conference, it could really change things," he said.

"I deeply believe that if everyone tackles these issues, they will cease to be problems. They can be a source of tremendous creativity."