The Abbott government's 2030 carbon emissions reduction goal is "weak" and it is time for Australia to show "real leadership" on the issue of global warming, says Heather Zichal, a former top climate adviser to US President Barack Obama.
The government this week set a target for reducing Australia's greenhouse gas emissions by 26 to 28 per cent on 2005 levels by 2030, a goal Environment Minister Greg Hunt described on Friday as "strong and deeply credible". 
But Ms Zichal, who was President Obama's chief adviser on climate and energy until late 2013, said the 2030 target is "being derided as weak [and] out of reach if Australia doesn't put new policies in place".
"The same is true for their 2020 targets," she said. "We need to see some real leadership."
Both the Coalition and Labor have agreed on a 2020 goal that will see 2005-level emissions trimmed by about 13 per cent.
The targets may get harder to reach if emissions from the power sector continue to rebound. An annualised jump of 2 million tonnes in   June and   July from the National Electricity Market was the biggest in about 11 years, business consultancy group Pitt & Sherry said earlier this month.
The government has said it can achieve both the 2020 and 2030 goals without restoring a price on carbon, which it scrapped in   July last year. Instead, it will rely mostly on its four-year $2.55 billion Emissions Reduction Fund to pay directly for carbon abatement, with the cost dropping to $200 million a year up until 2030. 
Opposition Leader Bill Shorten said on Friday that a Labor government would scrap the fund, describing the Direct Action policy "as a waste of money built on one counter-productive idea: giving great wads of taxpayer cash to big polluters to keep polluting".
"The government's emissions reduction target puts Australia at the back of the pack in the lead-up to Paris and yet we have the highest emissions per person in the developed world," Mr Shorten said.
Mr Hunt has said that Australia's growing population means per-capita emissions will need to drop by about 50 per cent to hit the 2030 target.
Ms Zichal last year said that Australia risked being sidelined in its relationship with the US if it did not contribute its fair share to combat climate change.
The French government, which will host the global climate summit in Paris starting at the end of   November, welcomed Australia's 2030 target as an improvement: "This demonstrates progress in relation to previously stated objectives by the Australian government."
Some overseas think tanks, though, have been more critical.
"Australia's discouraging 2030 climate target is at odds with the severe risks the country faces from climate impacts, such as droughts and wildfires," David Waskow???, International Climate Director at the World Resources Institute, said. "The proposal stands in contrast with the more credible commitments made by the European Union, the United States and others thus far."
Bob Ward, policy director at the London School of Economics' Grantham Research Institute, said Australia - and other nations - would have to raise their targets if the planet is to have a chance to avoid two degrees of warming compared with pre-industrial times. Temperatures have risen about 1 degree so far.
"There are some serious doubts about the credibility of Australia's submission and its ability to deliver, as Prime Minister Tony Abbott has explicitly ruled out any form of carbon pricing, or other comparable measures, to reduce the country's emissions," Mr Ward said.
"The International Monetary Fund has estimated that Australia will this year spend about $US30 billion, or nearly 2 per cent of its GDP, on implicit subsidies for the pollution and other problems created by fossil fuels," he said. "A strong carbon price would remove the subsidy for the greenhouse gas pollution that drives climate change."
With Nicole Hasham