Global carbon dioxide emissions from the energy sector stalled in 2014, the first time in 40 years during a period of economic growth, the International Energy Agency says.
By far the main culprit in global warming, carbon dioxide emissions stood at 32.3 billion tonnes in 2014, unchanged from the previous year, the IEA said.
"This is both a very welcome surprise and a significant one," IEA chief economist Fatih Birol said.
"It provides much-needed momentum to negotiators preparing to forge a global climate deal in Paris in December: for the first time, greenhouse gas emissions are decoupling from economic growth," he said in a statement.
"The preliminary IEA data suggest that efforts to mitigate climate change may be having a more pronounced effect on emissions than had previously been thought," it added.
The slowdown came thanks to "changing patterns of energy consumption in China and OECD countries", said the statement.
China, the world's top CO2 emitter, used more renewable energy in 2014 such as hydropower, solar and wind, while it burned less coal, the IEA said.
OECD countries, which include the United States and several European nations, intensified efforts to become more energy-efficient and use more renewable sources, it added.
In the 40 years since the Paris-based IEA was set up in the wake of the 1973 oil crisis, there have only been three other times when emissions stalled or fell.
"All were associated with global economic weakness: the early 1980s, 1992 and 2009. In 2014, however, the global economy expanded by 3 per cent," said the 29-member organisation.
Economist Birol said: "This gives me even more hope that humankind will be able to work together to combat climate change, the most important threat facing us today."
But the IEA said the world could not afford to slacken.
"The latest data on emissions are indeed encouraging, but this is no time for complacency - and certainly not the time to use this positive news as an excuse to stall further action," said IEA Executive Director Maria van der Hoeven.
A key climate change conference will be held in Paris in December.
Tasked with trying to limit the rise in global temperatures to two degrees Celsius over pre-Industrial Revolution levels, countries have until March 31 to announce their commitment to cutting greenhouse gas emissions.
The EU has formally adopted a 40 per cent cut in emissions by 2030, while the United States has announced plans to slash 26 to 28 per cent of its emissions in 2025 compared to their level in 2005.