Following are the impacts two regime scenarios would have by 2020 under "practical" and "aspirational" targets set by Garnaut using official Treasury Department modelling. The centre-left government will respond later in 2008.

* Carbon emissions permit price set at A$20 a tonne from 2010, rising by 4 percent a year above inflation until 2013. Market demand will then drive the price.

* The most likely "Practical" scenario sees emissions cuts, accompanied by concerted global action, of 10 percent by 2020, lowering Australian GDP by 1.1 percent and reducing consumption by 1.8 percent. The price of carbon would rise to A$34.50 in present dollar terms.

* The tougher "aspirational" scenario sees emissions cuts of 25 percent by 2020, lowering GDP by 1.6 percent and reducing consumption by 2.4 percent. The price of carbon would rise to A$60 in present dollar terms. Garnaut says this scenario is unlikely given current world sentiment on climate change.

* A third weakest scenario, seen in the event of a collapse of global climate talks on a post-Kyoto climate deal in Copenhagen in 2009, would see unconditional cuts by Australia of 5 percent by 2020. This offer would lower GDP by 1.3 percent and consumption by 1.6 percent. The price of carbon under this scenario would be driven higher because of global trading instability, rising to A$52.60.

(US$1 = A$1.22)

(Reporting by Rob Taylor; Editing by David Fogarty)