Professor Garnaut has been addressing a full town hall in Paddington, Sydney where he is presenting his draft climate change report.
The G8 countries have agreed to aim for a 50 per cent cut in global greenhouse gas emissions by 2050.
Despite some observers criticising a lack of commitment in the agreement, Professor Garnaut says the move represents real progress.
"The Japanese Prime Minister set out to get a commitment from the G8 leaders that they would aim towards a 50 per cent reduction in greenhouse emissions," he said.
Professor Garnaut points out that the 50 per cent goal was for the world as a whole, not just the G8 countries, and the world's major countries need to aim for bigger reductions down the track.
In relation to the 50 per cent global cuts ambition, "The Japanese Prime Minister got that agreement," he said.
