A royal commission into the nuclear fuel cycle has opened in Adelaide, with the first witness warning of Australia's need to catch up with other countries on tackling greenhouse gas emissions.

University of Melbourne Professor Ross Garnaut told the commission that human activity and the release of carbon dioxide and other carbon compounds into the atmosphere were changing the world's climate and Australia must respond.

Professor Garnaut warned Australia would need to make very significant changes to catch up with global efforts already underway to reduce greenhouse emissions.

"It is clear what Australia's pathway will need to be if we are to do our fair share in the global effort to ... reduce total emissions by about 95 per cent by the middle of the century," he said.

Professor Garnaut said Australia could become a competitive supplier of low-emission energy and "win back" its position as a low-energy country.

"If we play our cards right through sound policy, we will again be a country in which the world seeks to undertake energy-intensive processes," he said.

"The world's economy will rapidly increase demand for a lot of processes that draw on raw materials."

Professor Garnaut said there would be strong moves into nuclear energy production in China and India.

He said China was now shifting from its polluting behaviours and significant global reductions in greenhouse gas emissions could be achievable.

Garnaut sounds economic warning

Professor Garnaut said if global emissions reduction targets were not reached there would be a risk of "serious damage to global economic activity and political stability".

He told the inquiry Australians rated climate change as a very important issue and that would help drive policy change.

China's changing energy demands must affect Australia's decision-making, Professor Garnaut argues. ( David Gray: Reuters )

"If governments are not contributing their fair share to a global effort, then enough Australians care deeply about that for that to put pressure on outcomes," he said.

"I expect a ratcheting up of the Australian effort. We won't catch up with the international effort overnight but I don't think there's much doubt about the direction we'll be moving in the next decade or two."

Professor Garnaut said completely decarbonising the electricity system — that is generating power from low-emissions sources — would be the most cost-effective way for Australia to reduce its carbon emissions by up to 95 per cent by the middle of this century.

"Electricity is our largest source of emissions, but it's easier and cheaper to decarbonise electricity than some other forms of economic activity and so to get down to 90 per cent [overall] you would really have to do 100 per cent of electricity," he said.

Professor Garnaut described Australia as a "superpower of the fossil energy world" as its economic growth focused on those industries.

He said that was now starting to change, in part due to China's changing energy demands.

"Since 2011 you've had fundamental change in the Chinese model of economic growth, away from heavy reliance on growth in demand for fossil fuels," he told the commission.

"It was Chinese environmental policy that had a huge impact on Australia, in fact a much bigger impact than any change Australian policy would have."

Australia can be low energy cost leader: Garnaut

Professor Garnaut said Australia could achieve huge competitive advantages from low-emission energy resources.

"Australia is much richer in high-grade uranium oxide, the basis of nuclear energy, relative to other developed countries than it is in gas or coal," he said.

"Australia also has exceptional opportunities in biomass of various forms so in the low-carbon economy of the future, the low-carbon world economy, Australia can win back the advantage that it once held as a low energy-cost country."

Kevin Scarce says his inquiry is not an adversarial contest about nuclear issues. ( ABC News )

Royal commissioner Kevin Scarce, a former state governor, is examining the potential to expand South Australia's nuclear industry.

He said the public sessions of his investigation would draw on a wide range of expertise and experience.

"Doing so will allow me to understand the reasons why the potential activities the commission has been asked to consider might present either a risk or an opportunity," he said.

"The goal is to identify areas of consensus of opinion or view and in the event of differences of opinion to understand the reasons why.

"All this activity is directed at forming a rational and coherent basis for our report to government."

Mr Scarce promised he would carefully consider all the evidence presented to the commission.

"This is not an adversarial contest. The purpose of the public session is not a trial between competing cases, nor is any witness on trial. There is no score to be kept, the issues are just too important for that sort of approach," he said.

"I also ask those who are interested not to jump to conclusions. As with any inquiry, new issues will arise and some will fall away. It will be important to consider the evidence as a whole."

Royal commission considering specific role SA might have

When Premier Jay Weatherill announced the inquiry back in February, he said it would be a first for Australia.

It is looking specifically at South Australia's involvement in mining, enrichment, energy and storage phases of the nuclear fuel cycle.

There are expected to be about 30 public hearing days between now and the middle of December.

The early investigations are expected to deal with climate change, energy policy, the national electricity market, geology and hydrogeology.

Professor Garnaut previously did a study on climate change and policy responses for federal, state and territory governments.

Other key witnesses during the early stages of the royal commission include ClimateWorks Australia chief executive Anna Skarbek, University of Queensland professor John Quiggin and the University of Adelaide's Professor Graham Nathan.

Later in the year, witnesses will be called on other topics more specific to the nuclear fuel cycle, including on lessons learned from past activities in the state and the threat posed to humans and the environment by radiation.