(By Walter Gibbs and Sarah Lyall) - Former Vice President Al Gore, who emerged from his loss in the muddled 2000 presidential election to devote himself to his passion as an environmental crusader, was awarded the 2007 Nobel Peace Prize on Friday, sharing it with the Intergovernmental Panel on Climate Change, a United Nations network of scientists.

The Norwegian Nobel Committee praised both “for their efforts to build up and disseminate greater knowledge about man-made climate change.”

The prize is a vindication for Mr. Gore, whose cautionary film about the consequences of climate change, “An Inconvenient Truth,” won the 2007 Academy Award for best documentary, even as conservatives in the United States denounced it as alarmist and exaggerated.

“I will accept this award on behalf of all the people that have been working so long and so hard to try to get the message out about this planetary emergency,” Mr. Gore said Friday in Palo Alto, Calif., standing with his wife, Tipper, and four members of the United Nations climate panel. “I’m going back to work right now,” he said.

The award was also a validation for the United Nations panel, which in its early days was vilified by those who disputed the scientific case for a human role in climate change. In New Delhi, the Indian climatologist who heads the panel, Rajendra K. Pachauri, said that science had won out over skepticism.

Mr. Gore, a vociferous opponent of the Bush administration on a range of issues, including the Iraq war, is the second Democratic politician to win the peace prize this decade. Former President Jimmy Carter won in 2002.

Mr. Carter, himself a critic of Mr. Bush, was 78 when he won the prize. But Mr. Gore is just 59 and an active presence in American politics, if only as a large thorn in Mr. Bush’s side — and in the side of Democrats worried that he might challenge them for the 2008 Democratic presidential nomination. Mr. Gore, who lost the 2000 election to Mr. Bush, has regularly said that he will not run for president again. But Friday’s announcement touched off renewed interest in his plans.

Tony Fratto, a White House spokesman, did not go overboard in his praise. “Of course we’re happy for Vice President Gore and the I.P.C.C. for receiving this recognition,” he said.

In Oslo, Ole Danbolt Mjoes, chairman of the peace committee, was asked whether the award could be seen as criticism of the Bush administration, which did not subscribe to the Kyoto treaty to cap greenhouse gases. He replied that the Nobel was not meant to be a “kick in the leg to anyone” — the Norwegian expression for “kick in the teeth.”

“We would encourage all countries, including the big countries, and challenge them to think again and to say what they can do to conquer global warming,” Dr. Mjoes said in Oslo.

The four other members of the peace committee generally refuse to comment on the thinking behind the award, which in recent years has moved toward issues at a degree of remove from armed conflict, like social justice, poverty remediation and environmentalism. But in a telephone interview, Berge Furre, one of the four, said, “I hope this will have an effect on the attitudes of Americans as well as people in other countries.”

In its formal citation, the Nobel committee called Mr. Gore “probably the single individual who has done most to create greater worldwide understanding of the measures that need to be adopted.” It praised the United Nations panel, which is made up of 2,000 scientists and is considered the world’s leading authority on climate change, for creating “an ever-broader informed consensus about the connection between human activities and global warming.”

While the world’s major environmental groups all praised Mr. Gore for his role in raising public awareness, they praised the panel for, in the words of Greenpeace International, “meticulous scientific work.”

The two approaches both play a part, scientists said Friday. The Nobel Prize “is honoring the science and the publicity, and they’re necessarily different,” said Spencer R. Weart, a historian at the American Institute of Physics.

Mr. Gore, who announced he would give his portion of the $1.5 million prize money to the nonprofit organization he founded last year, the Alliance for Climate Protection, said he was honored to share the prize with the panel, calling it “the world’s pre-eminent scientific body devoted to improving our understanding of the climate crisis.”

Mr. Pachauri said, “The message that it sends is that the Nobel Prize committee realized the value of knowledge in tackling the problem of climate change.” He said the award was an acknowledgment of the panel’s “impartial and objective assessment of climate change.”

The climate panel, established in 1988, has issued a series of increasingly grim reports in the last two decades assessing issues surrounding climate change. It is expected to issue another report in the next few months, before the United Nations Climate Change Conference in Indonesia on Dec. 3. Some 180 countries are scheduled to begin negotiations there on a successor to the Kyoto Protocol, which expires in 2012.

Hans Joachim Schellnhuber, the climate adviser to Chancellor Angela Merkel of Germany and a leading contributor to the United Nations panel’s reports, said they were the result of “a painstaking process of self-interrogation.”

The committee acts at “about the highest level of complexity you can manage in such a scientific assessment,” Dr. Schellnhuber said in a telephone interview from Milan.

For a scientist, he said, taking part on the climate change panel entails considerable sacrifices. “It drives you absolutely crazy,” Dr. Schellnhuber said. “You fly to distant places; you stay up all night negotiating; you listen to hundreds of sometimes silly interventions. You go through so many mundane things to produce the big picture.”

The Nobel prizes are meant to be apolitical, and are awarded independently of one another. (The peace prize is awarded in Oslo, while the others are awarded by various academies in Sweden.) But a number of recent winners have expressed their opposition to Bush administration policies.

The 2005 literature winner, the British playwright Harold Pinter, turned his Nobel address into a blistering indictment of American foreign policy since the Second World War. A co-winner of the peace prize that year, Mohamed ElBaradei, the director of the International Atomic Energy Agency, made no secret of his opposition to the American invasion of Iraq and has angered the Bush administration by his measured methods for trying to rein in nuclear proliferation, particularly in Iran.

In its citation on Friday, the Norwegian Nobel Committee said the United Nations panel and Mr. Gore had focused “on the processes and decisions that appear to be necessary to protect the world’s future climate, and thereby reduce the future threat to the security of mankind.”

It concluded, “Action is necessary now, before climate change moves beyond man’s control.”

Walter Gibbs reported from Oslo, and Sarah Lyall from London. Reporting was contributed by Jesse McKinley from Palo Alto, Calif., Somini Sengupta from New Delhi, Mark Landler from Frankfurt, David Rampe from Paris, and Andrew C. Revkin from New York.