Gore, whose film on global warming, "An Inconvenient Truth," won an Academy Award earlier this year, had been widely tipped to win Friday's prize, which expanded the Norwegian committee's interpretation of peacemaking and disarmament efforts that have traditionally been the award's foundations.

"We face a true planetary emergency," Gore said. "The climate crisis is not a political issue, it is a moral and spiritual challenge to all of humanity."

The Nobel committee chairman, Ole Danbolt Mjoes, asserted that the prize was not aimed at the Bush administration, which rejected Kyoto and was widely criticized outside the U.S. for not taking global warming seriously enough.

"We would encourage all countries, including the big countries, to challenge, all of them, to think again and to say what can they do to conquer global warming," Mjoes said. "The bigger the powers, the better that they come in front of this."

Two Gore advisers, speaking on condition of anonymity because they are not authorized to share his thinking, said the award will not make it any more likely that he will seek the presidency in 2008.

If anything, the Peace Prize makes the rough-and-tumble of a presidential race less appealing to Gore, they said, because now he has a huge, international platform to fight global warming and may not want to do anything to diminish it.

One of the advisers said that while Gore is unlikely to rule out a bid in the coming days, the prospects of the former vice president entering the fray in 2008 are "extremely remote."

"Perhaps winning the Nobel and being viewed as a prophet in his own time will be sufficient," said Kenneth Sherrill, a political analyst at Hunter College in New York.

Gore, who was an advocate of stemming climate change and global warning well before his eight years as vice president, called the award meaningful because of his co-winner, calling the U.N.'s Intergovernmental Panel on Climate Change the "world's pre-eminent scientific body devoted to improving our understanding of the climate crisis."

Gore plans to donate his half of the $1.5 million prize money to the Alliance for Climate Protection, a bipartisan nonprofit organization that is devoted to changing public opinion worldwide about the urgency of solving the climate crisis.

In its citation, the committed lauded Gore's "strong commitment, reflected in political activity, lectures, films and books, has strengthened the struggle against climate change. He is probably the single individual who has done most to create greater worldwide understanding of the measures that need to be adopted."

The last American to win the prize, or share it, was former President Carter, who won it 2002.

At the time, then committee chairman Gunnar Berge called the prize "a kick in the leg" to the Bush administration for its threats of war against Iraq. In response, some members of the secretive committee criticized Berge for expressing personal views in the panel's name.

Mjoes, elected to succeed Berge a few months later, referred to that dispute on Friday, saying the committee "has never given a kick in the leg to anyone."

The White House said the prize was not seen as increasing pressure on the administration or showing that President Bush's approach missed the mark.

"Of course he's happy for Vice President Gore," White House spokesman Tony Fratto said. "He's happy for the international panel on climate change scientists who also shared the peace prize. Obviously it's an important recognition."

Fratto said Bush has no plans to call Gore.

In its citation, the committee said that Gore "has for a long time been one of the world's leading environmentalist politicians" and cited his awareness at an early stage "of the climatic challenges the world is facing.

The committee cited the IPCC for its two decades of scientific reports that have "created an ever-broader informed consensus about the connection between human activities and global warming. Thousands of scientists and officials from over 100 countries have collaborated to achieve greater certainty as to the scale of the warming."

It went on to say that because of the panel's efforts, global warming has been increasingly recognized. In the 1980s it "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."

Rajendra Pachauri, the IPCC chairman, said he and Gore really had 2,000 co-laureates — each of the scientists in the U.N. panel's research network.

"This award also thrusts a new responsibility on our shoulders," Pachauri said. "We have to do more, and we have many more miles to go."

But some questioned the prize decision.

"Awarding it to Al Gore cannot be seen as anything other than a political statement. Awarding it to the IPCC is well-founded," said Bjorn Lomborg, author of "The Skeptical Environmentalist.

He criticized Gore's film as having "some very obvious mistakes, like the argument that we're going to see six meters of sea-level rise," he said.

"They (Nobel committee) have a unique platform in getting people's attention on this issue, and I regret they have used it to make a political statement."

In his 1895 will creating the prize, the Swedish industrialist Alfred Nobel said it should be awarded for efforts toward peacemaking and disarmament, and the award now often also recognizes human rights, democracy, elimination of poverty, sharing resources and the environment. Last year, for example, it went to the Bangladeshi economist Muhammad Yunus and his Grameen Bank for pioneering the use of microcredit to spur creation of small businesses in poor nations.

Jan Egeland, a Norwegian peace mediator and former senior U.N. official for humanitarian affairs, called climate change more than an environmental issue.