Sydney and Tokyo have begun a worldwide sequence of Live Earth concerts aimed at raising awareness of climate change.
A total of 150 artists will be performing in nine cities, including London and Washington, over 24 hours.
Among the biggest names on stage are Madonna, Red Hot Chili Peppers, Metallica, The Police and Garth Brooks.
Live Earth is organised by former US Vice-President Al Gore, who called the concerts a “global response” to a global problem.
The Sydney event kicked off with a traditional aboriginal welcome and Al Gore appeared on video screens to launch the worldwide initiative.
Australian politician and former Midnight Oil frontman Peter Garrett also made an appearance, saying it was up to citizens of developed nations to push for action to reduce pollution.
“Your voice matters, make it heard,” he said.
The Sydney line-up featured Crowded House, performing songs from their new album Time On Earth, as well as Jack Johnson and Australian actress Toni Collette with her band The Finish.
The Tokyo concert was opened by the band Genki Rockets at the Makuhari Messe hall, east of the Japanese capital.
Mr Gore appeared as a hologram in front of the crowd, saying: “Now is the time to begin to heal the planet”.
Japanese singer Ayaka urged people to do what they could, saying: “We can start helping by doing something small. I started to carry my own eco-bag so I don’t have to use plastic grocery bags, and use my own chopsticks instead of disposable ones,” the Associated Press reported.
The next concert to get underway is in Johannesburg, and then later on in London, where Madonna, Duran Duran and the Beastie Boys will play.
Country couple Garth Brooks and Trisha Yearwood will be among the artists performing on The Mall in Washington DC.
However there has also been scepticism about the value of the concerts from some quarters.
Critics say that flying rock stars in on aeroplanes and using a great deal of electricity to power several concerts sends out mixed messages about energy conservation.
“What would be great is if these pop stars – now they realise the damage we are all doing to the climate – look very carefully at their own actions and make some changes themselves,” said John Buckley, managing director of the organisation Carbon Footprint.
Bob Geldof, who organised the Live Aid and Live8 charity concerts, has described the event as lacking a “final goal” and claimed most people already knew about the hazards of global warming.
Organisers have insisted they were keeping the concerts as green as possible.
Proceeds from ticket sales are going to distribute power-efficient light bulbs and other measures which will offset the shows’ greenhouse gas emissions.
Doubts had been cast over whether the Rio de Janeiro gig would go ahead because of concerns about safety on Copacabana Beach, but organisers persuaded a judge that adequate measures were in place.
However, the Turkish event – in Istanbul – was shelved, owing to insufficient sponsorship and lack of time.
Live Earth will also broadcast two songs performed in sub-zero conditions in Antarctica by Nunatak, a rock group made up of five members of the British Antarctic Survey.
They have recorded their contribution in front of 17 colleagues against a backdrop of icebergs.