Exactly how often can you stage a once-in-a-lifetime event? That's the challenge Saturday for the organizers of Live Earth, the latest in a long line of huge concerts-for-a-cause. This time the issue is global warming -- which is fitting considering the event isn't generating quite as much heat as hoped.
That's despite all-star lineups with such A-list rock, pop and hip-hop acts as Madonna, the Police, Justin Timberlake, Red Hot Chili Peppers, Kanye West and more than 100 others on stages in eight cities around the world, including East Rutherford, N.J.; London; Johannesburg, South Africa; and Sydney.
Yet snags have developed. The Johannesburg concert has been scaled back after tepid ticket sales, and a show planned for Istanbul was canceled altogether in the face of financial and logistical snags.
In Rio de Janeiro, meanwhile, an anxious government official said the plan to pack a million people onto Copacabana beach for a free concert was too risky, but Thursday a judge lifted an injunction that would have halted that show, sparing Live Earth officials the embarrassment of losing their single largest event.
Among the big issues Live Earth organizers are up against are distinguishing it from the plethora of similar-sounding concerts in recent years and spreading the word in hopes of creating a sense of excitement that reaches around the globe.
Previous concerts have relied heavily on the reach of MTV, which trumpeted Live Aid in 1985 and Live 8 shows in 2005. But MTV is not involved with Live Earth, and Saturday's shows have gotten considerably less advance promotion on U.S. television.
Promoters of Live Earth have said a potential audience of 2 billion people will attend a show or listen in via television, radio or the Internet. That figure, representing nearly a third of the world's population, may be hyperbole, but clearly it's a huge undertaking. Still, many people have heard little or nothing about the show.
Gary Bongiovanni, editor in chief of Pollstar, the U.S. concert industry's leading trade publication, said Thursday that he didn't have much to say about the Live Earth shows, which, in and of itself, says a lot.
"Honestly," Bongiovanni said. "I haven't paid that close attention to it. I don't really have a take on it. But it's a noble cause, and I hope they do well."
There's skepticism even within the music community over an event that organizers concede isn't geared toward specific solutions. Instead, its mission statement revolves around inspiring "a global movement to solve the climate crisis."
"Live Earth doesn't have a final goal," Bob Geldof, who organized Live Aid and Live 8, said in May. "I would only organize [this type of event] if I could go on stage and announce concrete environmental measures from the American presidential candidates, Congress or major corporations.
"They haven't got those guarantees," Geldof said. "So it's just an enormous pop concert, or the umpteenth time that, say, Madonna or Coldplay get up on stage."
In recent years, there has been a parade of all-star concerts-for-causes, including Sept. 11 memorials, benefits for victims of Hurricane Katrina and the tsunami in Southeast Asia, and, just last weekend in London, the benefit concert commemorating the life of Princess Diana.
Many of those concerts were pure fundraisers, and at their conclusion you could look at tote boards to gauge their success. This series of shows has a more amorphous goal, and that doesn't sit well with everyone.
Asked last month about Live Earth, Roger Daltrey of the Who, which is not a participant, moaned: "The last thing the planet needs is a rock concert."
Still, the Live Earth shows have a deep roster of big names stepping up to the microphones.
At the U.S. show, at Giants Stadium in New Jersey, the Police, Kanye West, Roger Waters, the Smashing Pumpkins, Bon Jovi and Alicia Keys will perform, and former Vice President Al Gore will be the host.
At Wembley Stadium in London, the bill is even stronger, with Madonna, Red Hot Chili Peppers, Metallica, Genesis, the Beastie Boys and Justin Timberlake.
A team of scientists will also perform music at a base camp in Antarctica, giving Live Earth a presence on all seven continents.
The two key figures behind Live Earth are Gore, who has become the most prominent name in climate politics, and Kevin Wall, the Emmy-winning producer who also worked with Geldof on the Live 8 shows.
Wall said he came up with the idea for Live Earth after seeing Gore in the Oscar-winning documentary "An Inconvenient Truth." On Thursday, Wall dismissed the criticism by Geldof and said that Live Earth would be "an unprecedented and historic event."
"We all have a lot of respect for Bob Geldof and what he has accomplished -- but frankly, when he said that, he had no idea what we were doing or what we are planning to do," Wall said.