The United States and other rich nations are doing less than their fair share to fight climate change under a U.N. accord due in December while China is outperforming, a report by 18 civil society groups said on Monday.
Overall, governments' pledges for curbs on greenhouse gas emissions are not enough to limit a rise in temperatures to 2 degrees Celsius (3.6 Fahrenheit), seen as a threshold for damaging heat waves, downpours and rising sea levels, it said.
"The ambition of all major developed countries falls well short of their fair shares," according to the report by groups including Christian Aid, Oxfam, the International Trade Union Confederation and WWF International.
The study coincides with the start of Oct. 19-23 talks among almost 200 nations in Bonn, Germany, the final U.N. session to prepare a deal due at a summit in December in Paris to limit climate change beyond 2020.
About 150 nations have so far submitted national plans for fighting climate change, as building blocks of a Paris accord. But there is no agreed system to compare each nation's level of ambition.
Monday's report said the rich could afford to shift from fossil fuels to cleaner energies, while helping others, and have more responsibility because they have benefited from burning coal, oil and natural gas since the Industrial Revolution.
By those yardsticks, it estimated that the United States and the European Union had promised about a fifth of their "fair shares" and Japan about a tenth.
By contrast, it found that emerging economies' plans "exceed or broadly meet" their fair share. China was doing more than its fair share, for instance, counting its emissions since 1950, while Brazil was contributing two-thirds.
"Across the board, rich countries are failing to bring the two most important ingredients to the negotiating table - emission cuts and money," said Brandon Wu of ActionAid.
Tasneem Essop, of WWF International, said Paris should set up "mechanisms to allow actions to get stronger and stronger through regular science and equity reviews."
Top emitters Beijing and Washington both say their plans are ambitious. China plans to peak greenhouse gas emissions around 2030 while the United States aims to cut greenhouse emission by 26-28 percent by 2025, from 2005 levels.
On current trends, Monday's report said temperatures were on track to rise by 3 degrees C (5.4F) or more above pre-industrial levels by 2100, well above the agreed maximum of 2C.
(Editing by Gareth Jones)