Australian Greens Leader Senator Christine Milne said she was alarmed by reports that the Climate Change Authority will only recommend reducing emissions by 15 per cent by 2020.
"This does not reflect the urgency of the climate science and nor is it fair in the global sense," Senator Milne said.
"In 2007, the Intergovernmental Panel on Climate Change said that rich nations should reduce emissions by 25-40 per cent by 2020. This should have been the Authority's starting point not 15 per cent.
"With the science getting worse and time running out we need to go harder.
"I am urging the Climate Change Authority to do what it was set up to do and be guided by the science not the politics.
"The Climate Change Authority was established to depoliticise the fraught process of setting emission targets and long-term carbon budgets and to take the science and fairness seriously.
"It is up to the Authority to ensure Australia contributes enough to global efforts to reduce emissions.
"If the rich nations like Australia don't contribute fairly, there will be no new effective global climate treaty in 2015.
"A target in the range of 25-40 per cent is affordable. It will barely slow economic growth, particularly now that carbon prices are likely to be lower than previously anticipated.
"If we don't significantly reduce our emissions in the next few years we will blow our carbon budget.
"As the Climate Commission has made clear, we are now in the critical decade to cut the pollution that drives global warming.
"Only the Greens can be trusted to stand up for real action on global warming."