Garnaut says we should cut our emissions to 10% of our year 2000 levels, and achieve that by 2020. That's part of a global target to limit atmospheric gas concentrations to 550 ppm. That means a 25% cut in our emissions which would slice 1.6% of our economy by 2020.
That means no Barrier Reef. 450 ppm would be in Australia's interest as it would lead to far less damage to the environment. China would have to agree to binding emissions targets from 2012 but there's no chance of China agreeing to this.