London: Prince Charles has said putting a price on carbon is a vital part of addressing climate change, setting him on a potential collision course with his hosts during his   November visit to Australia. 
Last year Australia became the first developed nation to repeal a carbon price scheme.
The Prince of Wales, for decades a campaigner for conservation and ecological causes, has emerged as a keen mediator on climate change in the lead-up to   December's COP21 in Paris - the United Nations summit intended to draw up a new global climate change action plan.
On Thursday in London he convened a high-level meeting on deforestation and climate change at Lancaster House, next door to the prince's home and office, Clarence House.
He revealed he has accepted an invitation from French President Francois Hollande to deliver a keynote speech at the opening ceremony of COP21. He previously attended the 2009 COP talks in Copenhagen.
"Paris will be an absolutely crucial milestone in the long overdue international effort to keep to a 2 degree world," Prince Charles told the meeting on Thursday, referring to the climate change "speed limit" set by scientists.
The UN's Intergovernmental Panel on Climate Change found that an average temperature rise of 2 degrees by 2100 would come with increased risk of sea level rise and extreme weather events, but beyond 4 degrees the effects quickly become much more dangerous.
The prince said a "4 degree" rise would be "impossible, I think, to adapt to".
COP21 must "send an unequivocal, long-term signal to the international community, and to global markets, that the transition to a low carbon, sustainable, climate-compatible economy is firmly and irreversibly underway", Prince Charles said.
"A 2 degree world is therefore still, just, if we stretch every sinew - by setting a proper price for carbon - within reach."
The UN's climate chief, Christiana Figueres, said earlier this week that a global carbon price would not be set at the Paris summit - but the world would move towards one in the future.
Around 60 jurisdictions including the European Union already have a carbon trading scheme or tax, and multinationals including big oil companies have called for a global carbon price to spur investment in low-carbon energy.
The prince has previously indicated his support for economic strategies to tackle climate change.
In 2012 the Prince of Wales' Corporate Leaders Group released a "Carbon Price Communique", making the case for setting a price on carbon emissions.
And at a speech in   July this year for the University of Cambridge Institute for Sustainability Leadership (CISL), he said "we will absolutely need a different kind of economy" to avoid dangerous climate change.
The prince is due to speak on climate change on   November 12 in Sydney, at a roundtable discussion hosted by CISL.
The day before he will meet with new Prime Minister Malcolm Turnbull in Canberra.
However it is not clear whether the prince will take the opportunity to urge Mr Turnbull to make a u-turn on the carbon tax.
A Clarence House spokesperson said "we wouldn't go into what might be raised in private meetings".
Mr Turnbull has said the government will review its climate change policies in 2017, but has avoided signalling any return to an emissions trading scheme.