Mr Conroy, the assistant shadow minister on climate change, estimates that Australian carbon emissions would be much lower today if the Greens had voted for the Carbon Pollution Reduction Scheme rather than rejecting it and bringing in a short-lived carbon price two years later.
“That was a massive error of political judgment,” he says of the way Ms Milne and four other Greens, including former leader Bob Brown, joined with the Coalition.
“It has had disastrous and long-lasting consequences for Australia’s ability to respond effectively to climate change.
“Australia’s annual emissions are now projected by the Department of the Environment and Energy to climb to 540 million tonnes in 2020 and to keep rising to 563 million tonnes by 2030.
“By contrast, under the CPRS, Australia’s emissions would have been reduced to 459 million tonnes in 2020.
“That is 81 million tonnes lower than now projected, or more than all of the fugitive emissions from the Australian coal mining, and oil and gas production industries combined.”
Mr Conroy will raise the issue in a speech on Monday at an energy conference at the Australian National University.
His key argument is that CPRS was due to commence with a target to reduce emissions by 5 per cent by 2020 compared to the levels of 2000 but would have “ratcheted up” over time.
As prime minister at the time of the vote, Kevin Rudd had pledged a range of 5 to 25 per cent in cuts by 2020, with mechanisms to review the target.
When the foregone emissions are added to produce a cumulative tally, Mr Conroy estimates Australia would have prevented 218 million tonnes of emissions between 2010 and 2020, beyond the actual outcomes of the last decade.
An emission cut of 81 million tonnes is greater than the annual emissions from all of Victoria’s coal-fired power stations as well as the Hazelwood station closed two years ago and the Liddell and Vales Point stations in NSW.
Labor is yet to decide the emission target it will take to the next election, but Mr Conroy’s speech emphasises the need for action, in contrast with fellow frontbencher Joel Fitzgibbon, who has argued for Labor to accept the government’s target.
Ms Milne said the CPRS would have set a low price on carbon emissions that did “absolutely nothing” to transition from fossil fuels.
She said the Greens were right to hold out instead for the carbon price agreed with Julia Gillard as prime minister in 2010. This was dismantled after Tony Abbott led the Coalition to victory at the 2013 election with a pledge to repeal the “carbon tax”.
“Not one environment group supported the CPRS in its final form,” Ms Milne said.
“The CPRS was bad legislation because it locked in failure as an emissions trading scheme.”
In a rejection of Mr Conroy’s argument, Ms Milne judged the CPRS by its “weak” target of 5 per cent and did not consider its target would have been raised over time.
The CPRS bill was rejected by the Senate by 42 to 31 votes when Labor could only gain the support of two Liberals, Sue Boyce and Judith Troeth, but not the five Greens.
Ms Troeth said she would “do it again tomorrow” if given the chance to vote for the CPRS.
“At the time I believed that, with the agreement of both the major parties, it was the best opportunity to get legislated agreement on this issue, and would remove it from the emotive basket of issues where it still is today,” she said.
“Far more learned commentators than I have said in the 10 years since that it was the best chance Australia has had to put a reasoned and logical basis to the question of how we deal with it, and I can only agree with them.”
David Crowe is chief political correspondent for The Sydney Morning Herald and The Age.