Professor Garnaut will announce his 2020 emissions target on Friday.
There is intense speculation over whether he will opt for a tough or a soft target. His decision will influence how much everyone will pay under emissions trading.
Wednesday, Prof Garnaut declined to say what his target would be.
"I'll be talking on Friday about that," he said after delivering a speech in Canberra.
Prof Garnaut said his target would be "very soundly based" and would take into account both economic and environmental points of view.
He is advising state and federal governments on what Australia should do about climate change.