Prime Minister Malcolm Turnbull has promised to spend "at least" $1 billion helping vulnerable nations cope with climate change at major climate talks in Paris.

But the money isn't new.

Like the $200 million pledged for a global climate fund at similar talks in Peru last year, the additional $800 million will be redirected from the existing foreign aid budget.

Mr Turnbull announced the five-year funding during his national statement alongside around 150 other world leaders on the first day of the United Nations climate change conference.

"The impacts of global warming are already being felt and will continue to be so even after we reach global net zero emissions," he told the UN Summit on Monday.

The prime minister also formally announced Australia's plan to double clean energy technology investment as part of a multi-country initiative known as Mission Innovation.

The 20 involved countries, including the United States, China and India, represent 80 per cent of global clean energy research and development budgets.

As part of the plan, Australian government investment in clean energy research and development will increase to about $200 million by 2020.

The government will also join a handful of developed nations to ratify the second phase of the Kyoto Protocol.

"I think it's a very important statement," Mr Turnbull told reporters in Paris.

While ratification sends a signal of Australia's commitment to emissions targets, it will also allow the government to access carry-over or "surplus" emissions from exceeding the first commitments.

"It has important advantages for Australia too," Mr Turnbull said.

Finance is a hot topic at the UN talks, with some predicting the fate of an agreement could depend on the size of the ask to entice poorer nations to sign on.

There's been growing pressure on Australia to pledge additional money, with international 'friends' stumping up large contributions.

Under the new leadership of Prime Minister Justin Trudeau, Canada pledged $2.65 billion over five years, while Japan committed to mobilising $10.6 billion in private and public funds by 2020. While Mr Turnbull is standing firm on Australia's 2030 emissions reduction targets of 26 to 28 per cent on 2005 levels, he indicated flexibility to increase it over time.

"Our agreement here in Paris must provide a common platform for action, the dynamism to build ambition and a robust and transparent reporting system," he said.

Part of that dynamism is a push by the Australian delegation for five-yearly reviews, which would force countries to assess their efforts and adjust accordingly.

A draft report released by the Climate Change Authority on Monday found Australia should consider an emissions trading scheme in order to reach its 2030 target.

Mr Turnbull has no plans to change Australia's direct action policy and Environment Minister Greg Hunt dismissed the report as an "options paper" that didn't draw any conclusions.

However, the government will review its domestic policies in 2017 and Mr Turnbull emphasised the real possibility of purchasing international credits in a bid to cut emissions cheaply.

"It's certainly something we'll be looking at with a very open mind," he said.

Opposition Leader Bill Shorten, who is also attending the summit, accused the prime minister of "playing it safe" and "doing very little" while in Paris.

"He's keeping the right wing of his party happy," he told reporters on Monday.

He dismissed the billion dollar commitment to climate finance as "accounting tricks" that purely shifted money around within the foreign aid budget.

"If the government is simply robbing Peter to pay Paul ... it's not really helping them at all, it's no net change," he said.

Greens senator Larissa Waters, who is also in Paris to keep tabs on Australian negotiators, agrees.

"Ripping money out of foreign aid and repackaging it as climate financing is pretty insulting, especially as the rest of the world has recognised the urgent need to give more," she told AAP.

The Climate Institute welcomed the finance pledge as encouraging but said it fell short of the $1.5 billion per year estimated as Australia's fair contribution.