Cuts in power sector emissions are unlikely to be maintained, while those from the transport sector will continue to climb in the absence of mandatory standards, according to analysis by The Australia Institute.
A separate report by the institute also found Australia's Paris climate goals to be "grossly inadequate".
At the end of March, carbon emissions from electricity generation were down more than 12 per cent compared with mid-2011, with almost the entire drop made up by brown coal-fired power stations.
The closure of Victoria's Hazelwood power plant in March 2017 removed Australia's most carbon-intensive power station.
"From now on … electricity emissions will fall much more slowly" if not remain flat, Hugh Saddler, an energy analyst and author of the report, said.
"Total energy combustion emissions may well start to increase, as they were doing up to the beginning of 2017 [prior to the Hazelwood closure]."
In the most recent government greenhouse gas data, electricity generation emissions fell 3.1 per cent in 2017, the only sector to record a drop.
Total emissions rose 1.5 per cent last year and are on course to notch a fourth consecutive year of growth. That's a trend at odds with Australia's pledge to cut carbon pollution 26-28 per cent from 2005 levels by 2030, particularly in the absence of policies to curb fossil-fuel use and looser curbs on land clearing.
In the transport sector – Australia's second-largest source of emissions after power generation – diesel now accounts for more than half the pollution, and is responsible for all its continuing growth, Dr Saddler said in the National Energy Emissions Audit.
Burning diesel typically emits 17 per cent more greenhouse gas than the same amount of petrol, offsetting its higher efficiency.
"Unless the Australian government takes action on emissions standards, we will continue to drive up emissions in the transport sector with one of the least efficient, highest-emission motor vehicle fleets in the world," said Dr Saddler.
"Australia's average fleet efficiency hasn't changed for years and years," he said. Most other wealthy nations had such controls, while emerging giants India and China had them.
Fairfax Media approached Josh Frydenberg, environment and energy minister, for comment.
Mr Frydenberg has said previously Australia's per capita reduction targets were among the highest for any nation, that the country would likely easily achieve its climate targets.
In a separate report out Tuesday, however, The Australia Institute took aim at Australia's international commitments, saying the country was not doing its "fair share" to combat climate change.
Applying several approaches used widely to assess nations' contribution, the institute found the government's Paris pledge to be "grossly inadequate".
“Whether you assess the fairness of a countrys emissions reduction target by population, economic cost, or a combination, our analysis shows Australias reduction target is unambitious, unfair and irresponsible,” Richie Merzian, director of the institutes Climate & Energy Program, said.
Given Australia's per capita emissions are among the highest in the world, its ambitions should also be high, with a national 2030 reduction target of 45-63 per cent to be fair, the report said. Labor's target is 45 per cent.
To have a mid-probability of meeting the Paris goal of keeping global warming to well below 2 degrees – compared with about 1 degree to date since pre-industrial times – the world can emit only a further 1040 gigatonnes of carbon-dioxide equivalent, the report noted.
According to Australia's population, the country's fair share of that total would be about 3392 million tonnes – an amount that would be taken up in about six years of current annual emissions.
Getting international co-operation on emissions, though, may be come more difficult in the short term, at least.
US President Donald Trump exited the G7 leaders summit over the weekend in Canada early, avoiding discussions on tackling climate change. The US signalled a year ago that it would pull out of the Paris accord.
The other six nations – Canada, France, Germany, Italy, Japan and Britain – all pledged to implement the climate agreement, but the US only promised to "work closely with other countries to help them access and use fossil fuels more cleanly and efficiently", according to a report by Inside Climate News.
Peter Hannam is Environment Editor at The Sydney Morning Herald. He covers broad environmental issues ranging from climate change to renewable energy for Fairfax Media.
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