Gore, who lost narrowly to Bush in the 2000 presidential election and who some hope will run again in 2008, shared the US$1.5 million prize with the United Nations Intergovernmental Panel on Climate Change (IPCC).

The former Democratic senator, speaking in California, called global warming "the most dangerous challenge we've ever faced" but declined to address whether he might enter the presidential race. He has said he has no plans to do so.

The committee awarded the prize from a near record field of 181 candidates for their efforts to draw attention to mankind's impact on the climate and measures needed to address it.

"Action is necessary now, before climate change moves beyond man's control," the committee said.

It warned that climate change -- linked to droughts, floods and rising seas -- could threaten living conditions across the world, prompt mass migrations and increase the risk of wars.

"We wish to put world climate on the agenda in connection with peace," committee chairman Ole Danbolt Mjoes said.

Since leaving office in 2001, Gore has lectured extensively on the threat of global warming and last year starred in his own Oscar-winning documentary film "An Inconvenient Truth" to warn of the dangers and urge action against it.

"He is probably the single individual who has done most to create greater worldwide understanding of the measures that need to be adopted," the Nobel committee said. "The IPCC has created an ever-broader informed consensus about the connection between human activities and global warming."

The committee said the case for action to stop global warming has been made convincingly by science.

"Whereas in the 1980s global warming seemed to be merely an interesting hypothesis, the 1990s produced firmer evidence in its support. "In the last few years, the connections have become even clearer and the consequences still more apparent."

The debate on global warming has focused partly on the certainty of the science, and some skeptics say that observed climate changes are within the range of natural variations.

PRESSURE FOR BALI DEAL

The award was seen raising pressure on the world to agree a new deal to combat global warming at a UN climate conference in Bali, Indonesia in December. Gore and the IPCC will collect their prize in Oslo on Dec. 10, while it is under way.

UN Secretary General Ban Ki-moon said the award underscores the urgency and significance that the international community has attached to global warming.

"This says there is an unprecedented momentum in the world to take necessary action," he said in an interview with Reuters Television in Washington, adding the combined work of the UN body and the former vice president would send a credible message to the Bali climate meeting.

Congratulations poured in from world leaders, including British Prime Minister Gordon Brown and German Chancellor Angela Merkel.

But Gore's critics said the award was wrong.

"Al Gore doesn't understand the science behind climate change or he deliberately misrepresents it," said Joseph Bast, whose Chicago-based Heartland Institute has run newspaper ads challenging Gore to debates on global warming.

Czech President Vaclav Klaus was surprised at the award because the relationship between Gore's work and world peace was "unclear and indistinct," his spokesman said.

It was the second Nobel peace prize for a leading US Democrat during the presidency of Republican Bush, who rejected the 1997 Kyoto Protocol setting limits on industrial nations' greenhouse gas emissions -- a pact supported by Gore.