Australian Greens Leader Bob Brown has welcomed Professor Ross Garnaut's support for the Greens proposal for an interim carbon tax until the nation finalises its carbon emissions reduction strategy.

Professor Garnaut called the proposal ‘another politically practical way forward'.

Senator Brown and Greens climate spokesperson Senator Christine Milne wrote to Prime Minister Rudd last week flagging the $23 per tonne carbon tax, to begin this July and apply only to the 1000 worst polluters in Australia.

Australian Greens Leader Bob Brown says that, after the Copenhagen collapse, next year's federal election will be a referendum on global warming.

"The 2010 poll is shaping up as a vote for or against Australia taking a lead in fixing global warming below 1.5 degrees. That means a 2020 target of reducing the nation's greenhouse gas emissions by 40 percent over 1990 levels and, in doing so, taking action for the rest of this threatened world to follow," Senator Brown said.

Australian Greens Leader Bob Brown has today called on the Minister for Climate Change Penny Wong to confirm that she has altered the government's greenhouse target goal posts.

Minister Wong told ABC Radio this morning: "If the world is prepared to be more ambitious so are we."

"The government has previously refused to lift its targets beyond 25% as called for by scientists and the Greens," Senator Brown said.