Prime Minister Malcolm Turnbull says he is “optimistic” about the chances of a global agreement being reached at next week’s climate change talks in Paris.

Global leaders are set to descend on the French capital to try to achieve a legally binding agreement aimed at keeping global warming below 2 degrees Celsius.

Similar meetings have failed to result in agreement but Mr Turnbull hopes Paris will be different.

• Slim majority of Aussies reject climate change
• Beyond Abbott: climate villains who need to go
• Perth engineer claims huge climate change discovery

“I am optimistic… and I notice that the French president is very optimistic,” he told ABC‘s 7:30.

Meanwhile, Opposition Leader Bill Shorten will today pledge to work towards carbon neutrality in Australia by 2050, meaning every tonne of pollution would need to be offset.

By Mr Shorten’s own admission, planning to achieve it by 2050 is an ambitious goal.

In a speech to the Lowy Institute in Sydney, Mr Shorten will say it could be done by making more use of biofuels and gas and improved land management.

He will also make an announcement about baseline emissions targets.

“The Climate Change Authority recommended a baseline emissions reduction of 45 per cent by 2030, on 2005 levels,” Mr Shorten will say.

“Today, I announce Labor will use the Climate Change Authority’s recommendation of a 45 per cent reduction as the basis for our consultations with industry, employers, unions and the community.”

Mr Shorten’s also promising a review of his party’s long-term climate change goals every five years.