KEY POINTS:
Tens of thousands of people in Sydney kicked off the event highlighting the problem of climate change.
It began at Aussie Stadium with a traditional Aboriginal welcoming ceremony, followed by a message from former US Vice-President Al Gore who appeared on video screens to formally launch the worldwide initiative.
The global broadcast spanning seven continents, which includes highlights from concerts in the United States, Germany, South Africa, England, Brazil and China as well as Japan and Sydney, was to continue for 24 hours.
Following in the footsteps of the Live Aid and Live 8 Mega-gigs, Live Earth aims to reach up to two billion people through radio, television and the internet, and features acts such as Madonna, Red Hot Chili Peppers, Snow Patrol and Snoop Dogg.
