Gore invited the crowd at the city's Aussie stadium, to take Live Earth's seven-point pledge to reduce their personal environmental impact and support policies to reduce greenhouse gas emissions.
The series began on Sydney on Saturday with an Aboriginal group dancing and singing a traditional welcome.
Concerts took place at Tokyo, Johannesburg, Shanghai, Hamburg, London, Washington DC, New Jersey and Rio de Janeiro.
The opening of the Sydney concert was followed by a video greeting from Al Gore, the former US vice-president and environmental campaigner, who inspired the event.
"Thank you for coming today and thank you for being the very first to launch this movement to help solve the climate crisis. Enjoy the show," he said.
The relatively unknown funk group, Blue King Brown, took the stage shortly afterward, the first official band on the global bill.
Global line up
The worldwide line up included Madonna, Metallica, the Police, Kanye West, the Pussycat Dolls and the Black Eyed Peas.
Problems and changes to the series continued right down to the last minute.
A ninth concert, in the US capital, was only added on Friday, while the Rio event was nearly stopped by a judge who feared for the safety of the 700,000 expected to attend the free concert in Copacabana.
|Organisers estimate that two billion people |
watched live broadcasts of the event [AFP]
Critics say Live Earth lacked achievable goals, and that bringing in jet-setting rock stars in fuel-guzzling aeroplanes to plug in amplifier stacks and crank up the sound may have sent out mixed messages about energy conservation.
The organisers of the Hamburg concert were criticised by environmental campaigners Greenpeace because DaimlerChrysler, the car manufacturer, was chosen as a sponsor.
Organisers say the concerts were as green as possible, with a record of energy use being kept.
Proceeds from ticket sales will go towards distributing power-efficient light bulbs and other measures that will offset the greenhouse gas emissions from the shows.
Many of the concerts were powered with renewable energy, the stages designed to be recycled and fans encouraged to use public transport to reach the venues.
In London, all the burger boxes were made of sugar cane and reed pulp, making them fully biodegradable, and all cooking oil from the concession stands was to be converted into biodiesel.
Scores of short films and public service announcements were aired giving the audiences tips about how to conserve energy and reduce their environmental impact.