China's greenhouse gas emissions could start to decline within 10 years, according to a report from the London School of Economics.
This would be five years earlier than expected and would offer a boost towards efforts to protect the climate.
The shift has been partly caused by a massive commitment to renewables. China is the world's top investor in wind and solar power.
It has also been replacing old coal plants with cleaner new stations.
'Under-promise and over-deliver'
Many of the changes in power generation have been prompted by the need to tackle chronic air pollution, but China's leaders are also acutely conscious of their country's particular vulnerability to a heating planet.
The authors of the LSE paper say: "The UN climate change conference in Paris later this year will be more successful if governments everywhere understand the extent of change in China [and] its implications for global emissions."
They say China's actions will stimulate global markets for clean goods and services and harm exporters of coal and certain other raw materials.
President Xi Jinping promised in a bilateral agreement with the US to reduce CO2 emissions by around 2030.
But the LSE authors, Fergus Green and Lord Nicholas Stern, say: "China's international commitment should be seen as a conservative upper limit from a government that prefers to under-promise and over-deliver.
"China's pledge includes a commitment to use 'best efforts' to peak before 2030; we are beginning to see the fruits of China's best efforts."
Counsel against complacency
The paper states: "China's transformation has profound implications for the global economy, and greatly increases the prospects for keeping global greenhouse gas emissions within relatively safe limits."
The authors find that if China's emissions peak by 2025 they would reach between 12.5 and 14 billion tonnes of carbon dioxide equivalent.
They say China's action increases the chances of keeping the world within the 2C (3.6F) temperature increase estimated to give a good chance of avoiding widespread damage to the climate.
But they counsel against complacency: "Whether the world can get on to that pathway in the decade or more after 2020 depends in significant part on China's ability to reduce its emissions at a rapid rate, post-peak, on the actions of other countries in the next two decades, and on global actions over the subsequent decades."
The paper is the latest bad news for coal producers: China might already have peaked in its use of coal, if statistics produced by the Carbon Counter website are to be believed.
The value of coal firms globally has slumped over recent years as nations turn to cleaner fuels like shale gas and increasingly cheap renewables.
Institutional investors are beginning to shun coal too, and last week Norway's pension fund confirmed that as part of a UN-backed campaign it would divest $7.6bn (£5bn) of investments in companies majoring in coal.
Some long-term energy analysts are offering the opinion that a tipping point has been reached. The world, they believe, is inexorably moving away from the fossil fuel era.
Follow Roger Harrabin on Twitter @rharrabin