China, the world’s largest greenhouse-gas polluter, is heading to Glasgow climate talks next week with a bold agenda: For the first time, it promises to take major steps to wean itself off fossil fuels, committing to net-zero emissions before 2060.

But in the coming decade, the country says, its carbon emissions will continue to rise, peaking sometime before 2030.

China’s climate pledges are bumping up against realities on the ground. The world’s No. 2 economy is so large and still growing so quickly that it might not be technically possible, let alone politically palatable, for the country’s leaders to move faster.

Earlier this year, Beijing pushed a range of measures to discourage the use of coal and control emissions. In late August, China’s top climate and energy official, Vice Premier Han Zheng, convened an online meeting of provincial leaders in Beijing, where he admonished them to “resolutely curb the blind development” of high-emissions projects like coal plants.

A month later, amid escalating coal shortages and power outages, Mr. Han told leaders of state-owned energy companies that although those curbs were still important, the priority was to get coal-power generators cranking again. “Increase coal supplies by any means necessary,” he told the closed-door gathering, according to two people familiar with the discussion and a summary of the meeting seen by The Wall Street Journal.

Coal powers around 56% of the country’s industry-heavy economy, a major reason China accounts for more than a quarter of the planet’s carbon emissions.

World coal consumptionSource: International Energy AgencyNote: 1 petajoule=1 quadrillion joules
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Chinese provincial governments approved 24 domestic coal plants in the first half of 2021, according to tallies of Chinese data by the environmental group Greenpeace. Chinese localities have around 104 gigawatts in top-priority coal-power capacity planned—more than what’s currently installed in coal-hungry Japan and Russia combined—although not all of that will come online and some older plants may be closed, offsetting the net increase.

Environmentalists and many governments want China to move faster. To reach the goal championed by advanced economies of limiting temperature increases to 1.5 degrees Celsius this century, global greenhouse-gas emissions in 2030 have to be reduced to around 25 billion metric tons, from about 52 billion in 2019, according to an assessment by the U.N. Environment Program. China alone currently generates around 14 billion metric tons of greenhouse gases a year. If that number stays largely unchanged in 2030, the country would account for more than half the world’s theoretically allowable emissions.

That means the rest of the world would have to work harder if China doesn’t do more, U.S. climate envoy John Kerry said at a July speech in London, noting that hitting carbon goals in that case would likely be “impossible to achieve.”

Chinese policy makers say they are planning to make up for slower climate progress before 2030 by a rapid carbon-emissions decline of as much as 10% a year over the subsequent two decades—a faster pace than anywhere in the developed world has managed so far.

China’s central government wants to be a global leader in new-energy technologies like batteries and solar power and show its people it is working to confront the country’s broader environmental problems.

“Achieving our carbon peaking and neutrality goal requires extremely arduous efforts from China,” the country’s climate envoy, Xie Zhenhua, said in an August videoconference with the Our Hong Kong Foundation, a think tank. He and other Chinese leaders say the country will be able to meet its existing targets, but moving faster is too much to ask.

The root conflict is that China just needs a lot more energy to achieve its goals of growing its economy and meeting the energy demands of its increasingly affluent population of 1.4 billion people.

Climate activists say they believe Beijing is serious about cutting coal consumption, but worry that local officials have struggled to kick the habit. Coal mining supports the economies of some of China’s poorest regions, providing millions of jobs. Some steps that officials have taken to reduce coal use in their own backyards have only succeeded in moving the problem elsewhere, eliminating some of the net gains in emissions.

Getting enough energy in a way that achieves Beijing’s 2060 net-zero emissions target will require investments of as much as $2 trillion a year until 2060, UBS Group estimates, including a more than tripling of its current world-leading pace of renewable-energy installations. Adding to the challenge is that China can’t easily pivot away from coal until it has enough other alternatives to ensure users have reliable power.

Achieving China’s new carbon-neutral goals will require the country “to almost rebuild the way the economy has been structured,” UBS said.

Coal’s importance to China’s economy has been on vivid display in recent weeks, as the worst electricity shortfalls in more than a decade have rippled across the country, closing factories and threatening global supply chains.

The problems started emerging earlier this year, as demand for Chinese exports during the pandemic pushed factories to increase production of electronics, car parts and a host of other goods.