A Sino-US breakthrough on reducing carbon emissions proves a global deal on climate change is achievable, US President Barack Obama said Saturday, as campaigners hailed new momentum in long-stalled talks.
Announcing a $3 billion contribution to a UN-backed climate change mitigation fund, Obama said the China-US deal showed the way forward.
"If China and the US can agree on this, then the world can agree on this -- we can get this done," he said in a speech on the sidelines of the G20 summit in Brisbane.
The UN and environmental campaigners welcomed the funding pledge, saying it confirmed global warming is now central to the world political agenda following the surprise deal between Washington and Beijing earlier this week to curb their greenhouse emissions.
Climate experts conceded that Republican opposition meant Obama could struggle to fulfil his $3 billion commitment, but said he was fuelling momentum for change in an area where talks have faltered since the historic Kyoto Protocol of 1997.
"You can sense the energy lifting in this critical conversation across the planet -- the game has changed," Greenpeace Australia chief executive David Ritter told AFP.
"A global deal has become more likely, no question. Climate is now front and centre for the US, it's front and centre for China, that means it's front and centre for all of us. It's now up to all governments to build on these huge steps forward."
- 'Leapfrog' dirty development -
Obama outlined his pledge to the Green Climate Fund (GCF) in a speech at the University of Queensland, telling the Australian audience he wanted his grandchildren to be able to visit the country's famed Great Barrier Reef "50 years from now".
He said the fund would help developing nations cope with climate-related issues such as rising seas while also backing environmentally friendly infrastructure projects.
"(It will) let them leapfrog some of the dirty industries that powered our development and go straight to a clean energy economy," he said.
Obama's announcement stymied efforts by G20 host Tony Abbott -- who questions the science of man-made climate change -- to reduce the issue to the margins of the Brisbane summit.
"I know there has been a healthy debate in this country about it," the American leader said, adding that "change is uncomfortable and difficult".
UN Secretary General Ban Ki-moon described climate change as "the defining issue of our times" and urged other G20 leaders to contribute to the GCF, which will hold a donors' meeting in Berlin on November 20.
"The transition towards a low-carbon, climate-resilient future is accelerating," Ban, who will host talks in Paris in December next year aimed at reaching a global agreement, said in Brisbane.
"I urge other leaders and major economies, especially at the G20, to come forward with contributions that will sustain this momentum."
- 'Clear message' -
The GCF is designed to help poorer countries invest in green technologies and build up their defences against rising sea levels and increasingly extreme weather patterns.
"To see the US put $3 billion into the fund is further evidence that they're determined to see a global deal done by next year," said Tim Flannery of the Sydney-based Climate Council.
"It's a clear message to the world that the US has moved on this issue and it expects the rest of the world to move."
France and Germany have already pledged $1 billion each, with Japan reportedly set to announce a $1.5 billion donation this weekend in Brisbane.
UN climate chief Christiana Figueres has called for an initial capitalisation of $10 billion by the end of the year.
However, Republican James Inhofe, regarded as the chief climate change sceptic in the US Congress, signalled Obama would struggle to get the funds through the legislature, particularly after his position was weakened in recent mid-term elections.
"President Obama’s pledge to give unelected bureaucrats at the UN $3 billion for climate change initiatives is an unfortunate decision to not listen to voters in this most recent election cycle," Inhofe said.
Michael Levi from the US-based Council of Foreign Relations said the US-China deal was a step forward but warned against getting carried away, saying it amounted only to "incremental" change.