China, the world’s biggest source of planet-warming greenhouse gases for most of the past two decades, is seemingly on the verge of bending its emissions curve from years of steep growth into a flat plateau.

The implications for climate change could scarcely be greater. Since China’s emissions surpassed those of the United States in 2006, China’s global share has grown to almost a third — a huge number, even with population differences taken into account.

A recent spate of data from China’s government, as well as reports by energy analysts, have provided positive signs that while China’s emissions may not decrease significantly, they also may not grow. Chinese President Xi Jinping had pledged to reach that turning point by 2030.

"The important thing to understand is that when China’s emissions stop growing, it likely follows that the world’s stop growing, too,” said Dave Jones, global insight director at Ember, an energy think tank.

The biggest factor in the shift is changes to how China produces its electricity. In short, renewable sources are replacing coal, the most polluting fossil fuel.

Last year alone, China installed more solar panels than the United States has in its entire history and connected most of them to its electricity grid.

Almost two-thirds of big wind and solar plants under construction globally are in China, according to a report last week from Global Energy Monitor. That is more than eight times the wind and solar capacity being planned in the United States.

And in May, China generated 53% of its electricity from coal, its lowest share since its government began publishing energy data decades ago, while nearly all the rest of it came from nonfossil-fuel sources. "This indicated that China may have peaked” its emissions, said Belinda Schäpe, a China analyst at the Center for Research on Energy and Clean Air.

However, some observers caution that "peak” was perhaps the wrong word to describe the current trend in China.

"We’ve been talking about whether there’s been a peak for almost a decade,” said Li Shuo, director of the China Climate Hub at the Asia Society Policy Institute. "Peaking assumes persistent emissions decline after it is passed. That’s not an assumption we can or should make.”

Li said it was more likely that China’s emissions would plateau. And he cautioned that while growth in renewable energy was responsible for replacing coal in electricity generation, other factors — such as China’s recent real estate crisis and sluggish post-pandemic economy — have led to less consumption of energy overall, which might skew the data downward, but only temporarily.

"If you look at China’s emissions profile of the past two decades, one particular source was hugely significant: real estate and construction, whose supply chain made up about a third of all emissions,” he said. "That’s cooling off.”

More reliable signs have come from recent policy shifts, he said. In particular, a new ban on permits for steel factories that would use coal to fire their blast furnaces could have far-reaching effects. A huge push toward electric-vehicle production has also dampened demand for oil.

But, ultimately, China’s emissions trajectory will come down to how quickly renewables can displace coal from its electricity mix. While coal’s share has fallen, China is still investing in it as a power source.

China alone accounted for two-thirds of the world’s newly operating coal plants last year. In 2023, new coal-plant construction hit an eight-year high in China. If China were to build all the others it has proposed, it would add the equivalent of one-third of its current operating fleet. Today, China accounts for around 60% of the world’s coal use.

Some of China’s coal build-out is meant to provide a fallback option for when wind and solar generation dips. But China is also investing heavily in pumped-storage hydropower. Pumped hydro is a way to store energy by pumping water uphill to a reservoir during times of low demand for electricity, then releasing it later to generate extra electricity if demand surges.

Those systems could help reduce the demand for coal power during peak times.

Oil and gas are also used in Chinese industry as power sources. But Li cautioned that while both China’s domestic production of petrochemicals was growing as well as its imports of them, the deciding factor in China’s emissions trajectory will be coal’s decline.

In the coming months, China’s government is expected to unveil new commitments to reduce emissions before November’s United Nations-sponsored climate summit, COP29, in Azerbaijan.

"Diplomatic attention is fixated on the question: Has China peaked or not,” Li said. "You could imagine that if the answer is yes, so far ahead of schedule, it might give China more reason to be even more ambitious with its reduction targets.”

This article originally appeared in The New York Times © 2024 The New York Times Company