Premier Li Keqiang yesterday unveiled the hotly-awaited climate promises in Paris, which will host UN talks at the end of the year tasked with producing a global pact on curbing climate change.
"China's carbon dioxide emission will peak by around 2030 and China will work hard to achieve the target at an even earlier date," Li's office said in a statement as he lunched with President Francois Hollande on the first day of a three-day visit.
After that announcement officials stressed that the wording was crucial, and that "around" could mean before or after the date.
China is widely expected to meet the goal, with some analysts predicting emissions will peak years earlier.
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Wang Tao, a resident scholar on energy and climate at the Carnegie-Tsinghua Center for Global Policy in Beijing, said of Li's declaration: "It's not a significant leap forward from what China announced last year during Obama's visit.
"I wish China could do more, along with other countries, in tackling climate change."
China also aims for non-fossil fuels to grow to a 20 per cent share of primary energy consumption -- a promise that was also made at the time of Obama's visit.
In addition Beijing is pledging to cut its "carbon intensity" -- carbon dioxide emissions per unit of GDP -- by 60-65 per cent over 2005 levels by 2030.
Its climate change plan is part of, but subordinate to, the larger goal of transforming the economy, Wang said.
Other analysts hoped more could be done to stem the effects of warming the planet, saying China was already on track to fulfil many of its goals.