Al Gore says his Nobel Peace Prize is an “honour” and a chance to “elevate global consciousness” about the threat posed by climate change.
The former US vice-president was awarded the prestigious prize jointly with the UN’s Intergovernmental Panel on Climate Change (IPCC).
The White House congratulated Mr Gore but said it would not change its policies on global warming.
Mr Gore’s film on climate change, An Inconvenient Truth, won an Oscar.
He said he accepted the Nobel award on behalf of scientists – like those in the IPCC – who had worked tirelessly for years to get the message about global warming out.
“This is the most dangerous challenge we’ve ever faced,” he said, speaking in Palo Alto, California.
“I will be doing everything I can to try to understand how to best use the honour and recognition of this award as a way of speeding up the change in awareness, and the change in urgency.
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.
Mr Gore, 59, 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.
He said he would donate his half of the $1.5m prize money to the Alliance for Climate Protection.
Front-runner for the Democrat presidential nomination, Hillary Clinton, sent a message of congratulations, as did her husband, Mr Gore’s former boss, ex-president Bill Clinton.
“His dedication and tireless work have been instrumental in raising international awareness about global warming,” Ms Clinton said of Mr Gore in a message on her website.
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.
But the president was not about to adopt a more “Gore-style” approach to the global warming issue, said the spokesman.
Mr Gore’s win 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.
Mr Gore’s 2006 documentary film was an unlikely box-office hit and won two Oscars.
But this week it was criticised by a British judge for containing nine errors, and for being alarmist.
The IPCC, established in 1988, is tasked with providing policymakers with neutral summaries of the latest expertise on climate change.