The concerts span nine cities -- including London; Shanghai; Johannesburg, South Africa; and Hamburg, Germany -- and will feature about 150 acts, the BBC reported.

Among the acts taking part are superstars Madonna and The Police.

The Sydney event was kicked off with a traditional aboriginal welcome before the creator of Live Earth, former U.S. Vice President Al Gore, appeared on a video screen to launch the concerts worldwide.

He described the concert kickoff as the start of a three-year campaign to try to "heal the planet."

Live Earth organizers said nearly 2 billion people will have access to the concerts through TV, radio and the Internet.