Best-selling author Ian McEwan surprised an audience at the Hay literary festival in Wales on Sunday by reading a preview extract from his novel in progress, due in about two years.

The book, which still doesn't have a title, tells the story of Nobel prize-winner Michael Beard, and his attempts to save the world from environmental damage.

The character will also fight against his own decline, as after winning the most precious academic award his work and life falls into a steep decline, McEwan told the audience in attendance at the book festival held each year in the town of Hay-On-Wye just over the Welsh border.

The author of "On Chesil Beach" and "Atonement" warned the novel is not a comedy, despite the fact that his extract of Michael Beard's confusion over a pack of crisps was greeted with laughter.

The idea to tackle climate change was brewing during a trip in 2005, when artists and scientists went on an expedition near the North Pole to discuss the subject.

"I realised that it's all about human nature," he said. "The way to write about climate change is through writing about human nature."

"For You," an opera that he wrote and was scheduled to open on Saturday, was cancelled due to sickness of one of the singers. It is now due to open in the autumn, the Hay Festival said.