A worldwide concert series to raise awareness about the dangers of global warming got underway Saturday in both Sydney and Tokyo.

The daylong "Live Earth" concerts opened in Sydney, with a traditional welcome ceremony by Australian Aboriginal dancers. Former U.S. Vice President Al Gore delivered greetings to the Sydney audience by video, then appeared as a hologram (a computer-generated image) to the Tokyo concert-goers.

More than 150 of the world's most popular musical acts will perform in concerts scattered across in seven continents, including Antarctica. The performers include Shakira, the Black-Eyed Peas, Yusuf Islam - the British musician and singer originally known as Cat Stevens - Metallica, Madonna and the Red Hot Chili Peppers.

Organizers say they hope their message about climate change will reach two billion people - those attending the concerts and others taking part through radio, television and the Internet.

Gore says he hopes the concerts will jump-start "an unprecedented and sustained global movement" against climate change. He has become one of the world's most visible activists campaigning for action to stop global warming.

The "Live Earth" concerts also have drawn some criticism from some who say that flying celebrities - many of whom are accustomed to luxurious lifestyles - all around the globe is more likely to result in a net increase in global warming.

Some information for this report was provided by AP and Reuters.