The committee cited “their efforts to build up and disseminate knowledge about man-made climate change”.

Mr. Gore, US vice-president under Bill Clinton, said he was “deeply honored”.

Mr. Gore, 59, won an Oscar for his climate change film An Inconvenient Truth while the IPCC is the top authority on global warming.

IPCC chairman Rajendra Pachauri said he was “overwhelmed” by the award.

He told a cheering crowd of colleagues and journalists outside his office in Delhi that he hoped the award would bring a “greater awareness and a sense of urgency” to the fight against global warming.

The Norwegian Nobel Committee said it wanted to bring into sharper focus the “increased danger of violent conflicts and wars, within and between states” posed by climate change.

It highlighted a series of scientific reports issued over the last two decades by the IPCC, which comprises more than 2,000 leading climate change scientists and experts.

The reports had “created an ever-broader informed consensus about the connection between human activities and global warming”, the committee said.

Mr. Gore was praised as “probably the single individual who has done most to create greater worldwide understanding of the measures that need to be adopted”, through his lectures, films and books.

The choice of recipients continues a trend of the Nobel Peace Prize redefining the potential sources of conflict and threats to peace, says the BBC’s world affairs correspondent Mike Wooldridge.

‘Planetary emergency’

Speaking in Washington, Mr. Gore praised the IPCC, “whose members have worked tirelessly and selflessly for many years”.

“We face a true planetary emergency,” Mr. Gore warned. “It is a moral and spiritual challenge to all of humanity.”

He said he would donate his half of the $1.5m prize money to the Alliance for Climate Protection.

Mr. Gore’s selection has prompted supporters to renew calls for him to stand in next year’s US presidential race. Until now, Mr. Gore has said he will not run.

President George W. Bush, who defeated Mr Gore in a bitter fight for the presidency in 2000, was “happy” at the “important recognition” for his rival and the IPCC, a White House spokesman said.

However, the president was not about to change his more sceptical stance on global warming to a more “Gore-style” approach, the spokesman said.

The former vice-president has emerged as a leading climate campaigner. His 2006 documentary film, An Inconvenient Truth, was an unlikely box-office hit and won two Oscars.

The IPCC, established in 1988, is tasked with providing policymakers with neutral summaries of the latest expertise on climate change.

The organization involves hundreds of scientists working to collate and evaluate the work of thousands more. BBC NEWS