But he says there's no debating the existence of global warming.
"The debate among scientists is over," he told co-anchor Harry Smith on The Early Show Wednesday. "There is no more debate. We face a planetary emergency. And the phrase sounds shrill but it is an accurate description of the climate crisis that we have to confront and solve."
Gore's 2000 defeat freed him to spread the word on global warming, an issue he's passionate about.
He stars in a new documentary about it that's generating plenty of buzz.
"An Inconvenient Truth" was the toast of the just-concluded Cannes Film Festival. It's been blowing away many other contenders at the box office on an attendance-per-screen basis.
And bootleg video of Gore's May 13 appearance on "Saturday Night Live" has been downloaded by thousands of Web users.
Gore has taken on the role of road warrior for the environment, going from town to town and nation to nation, emphasizing the scope of what he views as the real and present danger global warming poses to all of us.
"I am Al Gore. I used to be the next president of the United States of America," is a joke he uses to start serious lectures about the issue.
In "An Inconvenient Truth," which is also out in book form, Gore says: "The Arctic is experiencing faster melting. If (the arctic ice) were to go, sea levels worldwide would go up 20 feet." And the World Trade Center memorial site would be under water.
Some say Gore is the latest political "Comeback Kid."
"It started with the 'Saturday Night Live' appearance," says CBS News political analyst Craig Crawford, "then this movie that he's done on global warming. … Al Gore is somewhat vindicated in the minds of a lot of Democratic voters, as George Bush has become so unpopular."
Will Hillary Clinton, widely viewed as the present frontrunner for the Democratic presidential nod in 2008, soon have a former vice president to contend with on the campaign trail?