Australia must move away from its reliance on coal, says the United Nations' top climate negotiator Christiana Figueres.
The executive secretary of the UN's Framework Convention on Climate Change spoke to delegates at the Australian Emissions Reduction Summit in Melbourne on Wednesday.
She said peak global emissions had to be reached within the next 10 years so the reduction could begin and climate neutrality could begin in the second half of the century.
In her first major interview since her arrival, Ms Figueres told the ABC that Australia had no option other than to gradually step back from coal.
"As we look into the future - not overnight - but over time there does need to be an economic diversification view that is not going to rely fully on coal," she said.
"I think Australia will have to look at a gradual transition and a broader resource base for its exports, mainly because the demand for coal is already decreasing and will continue to decrease."
Ms Figueres will be in charge of getting a global emissions reduction agreement in Paris in December.
She said while Australia emitted only 1.3 per cent of global emissions, it had a unique responsibility.
"Australia is the 13th largest emitter in the world and among all industrialised countries it is the highest per capita emitter," she said.
But she conceded emission reductions would come at an economic cost.
'Nobody can tell you how to do it'
"It is not easy to bring down the emissions in Australia because of the natural resource base that is here.
"[That's] the extraordinary coal reserves that are in Australia that have been the backbone of the prosperity and growth of Australia."
Delegates at the Melbourne emissions reduction summit have spent two days debating the best way for the nation to reduce emissions.
Australia's current target is to reduce greenhouse gas emissions to 5 per cent below 2000 levels by 2020.
However, Australia's post-2020 targets are up for discussion.
The Government is expected to announce those targets in early July.
Ms Figueres told the summit it was "very important" to have an Australian voice in the lead up to the Paris negotiations.
"You represent a huge potential to lead the world into a very healthy economic diversification path," she said.
"You haven't figured out yet how to do it, but, my friends, that is your homework."
And she stopped short of recommending set targets for Australia.
"That is not a question that I can answer for you.
"That is a question that Australia, jointly in collaboration across sectors, across political parties, across states, across territories ... has to come up with.
"Nobody can tell you what to do."
Ms Figueres also tweeted a photo of herself with AGL boss Andrew Vesey.
Last month AGL announced plans to stop investing in coal-fired power, saying it would shut its coal-fuelled power stations by 2050.