Former Vice President Al Gore formally endorsed Sen. Barack Obama, D-Il., on stage before 20,000 people at a rally Monday night in Detroit, MI, reports ABC News.

"The outcome of this election will affect the future of this planet," Gore said at Detroit's Joe Louis Arena. "We've got to have new leadership. Not only a new president, but new policies."

Last evening was the first time the prominent Democrat, Nobel Peace Prize winner, and climate change crusader publicly backed the presumptive Democratic nominee.

In a 15-minute speech, the 2000 Democratic presidential candidate called the primary an "historic contest," and heaped praise upon the Illinois senator for his opposition to the Iraq war in 2002. Gore, a superdelegate, was markedly absent during the primary battle between Obama and Sen. Hillary Clinton.

Obama returned Gore's favor with some compliments of his own:
“So Washington, which is always the last to hear the news, may not have listened to Al Gore 30 years ago, but America and the world are listening now, and when I am president I will be counting on Al Gore to help me lead the fight to achieve for a clean energy future here in America and around the globe,” said the nominee.

Some in the poltical arena, including Democratic strategist and former Clinton aide James Carville, have tossed Gore's name into Obama's running mate hat. The notion, however, seems unlikely, as Gore is likely to decline the position.

"I haven't ruled out the idea of getting back into the political process at some point in the future," Gore said last winter. "Don't expect to. But if I did get back, it would be as a candidate for president, not in any other position."