EAST RUTHERFORD, N.J. -- Live Earth, the confederacy of musicians who performed Saturday on all seven continents to highlight the issues of global climate change, featured superstars such as Madonna and the Police, who entertained crowds in packed stadiums.

Live Earth used the now-familiar template of concerts-for-causes that was shaped largely by Live Aid, the 1985 famine relief shows. But the 24 hours of music circling the globe used the Internet and high-definition camera technologies to create a uniquely 21st century event.

Leading up to the event, though, Live Earth was also criticized by some for being too vague in its cause or for being a promotional tool for its co-founder, environmental activist Al Gore, the former vice president.

The politician was given a rock star's welcome at Giants Stadium in New Jersey, where he was introduced by Oscar-winning actor Leonardo DiCaprio. In London, the Black Eyed Peas' Will.i.am premiered a new pro-Earth song that he said he recorded after an inspirational encounter with Gore at the Grammy Awards in February.

One of the song's lines: "We got a new terror threat: The weather."

The other Live Earth concerts Saturday were in Hamburg, Germany; Sydney, Australia; Tokyo; Shanghai, China; Rio de Janeiro, Brazil; and Johannesburg, South Africa, while many "unofficial" events borrowed the name and cause of the day, such as the Viva Earth show, an R&B and hip-hop concert at the Los Angeles Memorial Coliseum.