"Times like these demand action," said former Vice President Al Gore, speaking to the sold-out crowd of about 52,000 in New Jersey's Giants Stadium.
With other shows in London, Sydney, Tokyo, Kyoto, Shanghai, Hamburg, Johannesburg, Rio de Janeiro and even a performance by a band of scientists at a research station in Antarctica organizers promised the biggest musical event ever staged, dwarfing the Live Aid and Live 8 concerts. Organizers estimate 2 billion people heard Live Earth's music in person, on TV or on the Internet.
Live Earth venues featured aboriginal elders, chimpanzee calls from scientist Jane Goodall, a holographic Gore and more than 100 of the biggest names in music including Bon Jovi, Linkin Park and the Beastie Boys.
One of the day's musical highlights was at the New Jersey show, where Keith Urban and Alicia Keys performed a fiery rendition of The Rolling Stones' "Gimme Shelter," with Keys belting out her part with a ferocity that would make Merry Clayton proud while Urban wailed on his guitar.
Photos: Rockin' Live In Jersey Photos: Live Earth In London
Theirs was not the only socially-conscious song from the 1970s to be dusted off for a celebrity duet. At the London concert, John Legend and Corrine Bailey Rae sang Marvin Gaye's "Mercy Mercy Me (The Ecology)" which Keys also performed in her solo set in New York.
Then there was the "concert" from Antarctica which featured just one band: Nunatak. Described on their Web site as the British Antarctic Survey's Rothera Research Station's "house band," the 5 members are all scientists investigating climate change and evolutional biology on the Antarctic Peninsula.
The concerts are backed by Gore, whose campaign to force global warming onto the international political stage inspired the event. At concerts around the world, musicians and celebrities encouraged fans and one another to take little steps, such as not leaving electrical devices plugged in when not in use, or changing to low-energy light bulbs.
At the London show, the stadium's nonessential lights were turned off before the closing act Madonna came onstage, leaving the venue dark except for the glow of exit lights and the flashes of cameras.
2"Let's hope the concerts that are happening around the world are not just about entertainment, but about starting a revolution," said Madonna, who sang a song she wrote for Live Earth called "Hey You."
The Beastie Boys wore their feelings on their sleeves, performing a furious set of their hits in tailored green suits and shades when they took the stage at Wembley Stadium.
"Let's all try to do our parts and see if we can get it together," Beastie Boy Adam Yauch told the crowd.
In New Jersey, rocker Melissa Etheridge pounded out her song "I Need to Wake Up," which was featured in Gore's documentary, "An Inconvenient Truth," and won an Oscar for best song this year.
Gore later introduced Bon Jovi, which hails from the Garden State, telling the crowd that the band was one of the first to volunteer its musical services when the concert was announced. Band members didn't make any environmental statements during their five-song set, but that didn't seem to matter to their cheering fans.
Gore also made a live video appearance from Washington to open the first show on the other side of the world in Sydney, Australia, and a few hours later appeared onstage in Tokyo as a hologram.
"I would like to ask each and every one of you to answer the call," Gore said.
Many of the celebrities and musicians — if they mentioned global warming at all — focused on what everyday citizens could do to help out and stayed away from partisan politics. Among them was actress Cameron Diaz, who told the New Jersey crowd that this day "is not about gloom and doom. It's a celebration."
"I'm getting solar panels, using sheep's wool insulation, it's all kind of reclaimed wooden stuff," singer K.T. Tunstall tells CBS News correspondent Michelle Miller. "But most of the time I'm on the road and so that's really where I really need to focus my energy when it comes to green stuff."
Musician Dave Matthews says it's all about the little things, like bringing your own mug to your favorite coffee shop.
"It's not like we're gonna save the planet but we might as well grab at some straws before we all go down, you know," he told Miller.
One of the exceptions was environmental activist Robert F. Kennedy Jr., who called on attendees to "get rid of all those rotten politicians we have in Washington, D.C."
Organizers promised the huge shows were made green by using recycled goods, shuttling some concertgoers from distant parking lots in bio-diesel buses and using biofuels for generators.
Critics have faulted the Live Earth concerts for lacking clear-cut, achievable goals, and for lauding rock stars whose jet-setting, high-consumption lifestyles can often send a different, less environmentally friendly message.
Photos: Live Earth Preps
In London, after fans went home, the stadium's floor was covered with discarded plastic cups and litter.
Many of the musicians acknowledged that they weren't rock stars when it came to the environment but said it was important to start a discussion about climate change.
"If you want to peg me as not being entirely eco-friendly, you'll win," said John Mayer, speaking to reporters after his set. "I also think it's very difficult to judge the success of a movement. ... You can't find out by 9 o'clock this evening how much awareness was raised. ... What you're really talking about is the placement of an idea at a rock show."
At other shows around the globe, an estimated 50,000 people grooved through a set by singer-guitarist Jack Johnson, while country stars Garth Brooks and Tricia Yearwood opened the Washington concert and Linkin Park entertained fans at a Tokyo concert.
3On Rio's Copacabana Beach, thousands gathered as the sun set to hear Lenny Kravitz, Macy Gray, Pharrell Williams and Brazilian superstar Jorge Ben Jor. And in Johannesburg, the concert ended with the artists and audience clapping out SOS in morse code a reference to the evening's theme of answering the call to save the planet.
The shows appeared to come off without major hitches despite some 11th-hour activity. The concert in Washington was added Friday, and a Brazilian judge rejected a last-minute bid to shut down South America's concert after a prosecutor had argued safety could not be guaranteed for an audience of 700,000.
At the New Jersey concert, the crowd was dotted with people who heeded the call to wear green. Many said they were already taking steps at home to lead a little more green lifestyle, and felt the concert wasn't just about music.
"Personally, I think it makes people more aware," said Sherry Ramsey, 44, who came to the concert with her husband by plane and train. "It was mass transit all the way here."