Environmentalists have welcomed the pledge by China’s leader, Xi Jinping, to speed up reductions in emissions in the world’s top-polluting nation and reach carbon neutrality by 2060.

The ambitious goal, which surprised many experts, could help significantly slow global warming. They warned, however, that Mr. Xi had offered almost no detail, raising doubts about the viability of targets that remain years in the future.

Here’s what to know about the pledge:

Xi’s pledge is a tectonic shift in policy, not yet practice

China has long argued that as a developing economy it should not have to share the same burden of curbing emissions as developed nations whose pollution went unchecked for decades. China is now pledging to lead by example, setting itself goals befitting a country that aspires to be a superpower.

Under the Paris climate deal reached in 2015, China pledged that its emissions would peak around 2030. Mr. Xi promised on Tuesday to move up that timetable, though he did not provide specifics. The bigger surprise, analysts said, was Mr. Xi’s pledge to reach "carbon neutrality" — meaning China’s net carbon emissions will reach zero — by 2060.

More than 60 other countries have pledged carbon neutrality by 2050, a consensus deadline that scientists believe must be met to have a reasonable chance of averting the worst climate catastrophe. Those countries are small compared to China, which now produces 28 percent of the world’s emissions. Even if its target is a decade later, China is now on record setting the goal for the first time.

"I think it is potentially enormous — stressing both words," Lauri Myllyvirta, lead analyst at the Center for Research on Energy and Clean Air, said in a telephone interview from Helsinki, Finland.

China would need to reverse recent emissions trends

There are plenty of reasons for caution. In recent years, analysts have warned about worrisome trends in the country’s commitment to fight global warming in the face of economic slowdowns.

Coal consumption, which had declined from 2013 to 2017, driven in part by a push to improve China’s notorious air quality, began to rise again in recent years as the economy faced economic headwinds and the government sought to stimulate industrial growth.

The rise was interrupted by the Covid-19 shutdown, but China’s economy is recovering more quickly than others. Research by Mr. Myllyvirta has shown that by May, carbon dioxide emissions from energy production, cement making and other industrial uses were 4 percent higher than the year before. China also granted more construction permits for coal-fired power plants in the first six months of 2020 than it had each year in 2018 and 2019.

Mr. Xi, in laying out his country’s plans in a speech at the United Nations, did not detail how China would meet the targets. Li Shuo, a policy adviser for Greenpeace China, said that the lack of specificity was probably intended to leave the Communist Party leadership flexibility in the short term to pursue an economic rebound following the pandemic.

The government’s next five-year plan, to be released soon, will be a key document, detailing the necessary economic, industrial and environmental changes that will be necessary.

"They really need to roll up their sleeves from today to capture the level of ambition we heard last night in our daily practices," Mr. Li said in a telephone interview from Beijing, referring to Mr. Xi’s U.N. speech.

The impact could affect all 1.4 billion people in China

Mr. Li said the carbon neutrality pledge required a complete transformation of the Chinese economy.

"Think about it: The way we eat, the way we consume energy, the way we produce our food, the way we commute to work will need to be completely rearranged," he said.

While China clings to industries that are consumers of coal, it has also emerged as a leader in clean energy technologies, including solar panels and wind turbines. It is the world’s largest manufacturer of electric cars and buses. That could leave the government well positioned to make a transition away from fossil fuels, provided the political commitment is there.

China could also ramp up its ambitions to build nuclear power plants to replace coal-fired plants, though that would prompt other environmental and safety questions.

Wang Wenbin, a spokesman for the Ministry of Foreign Affairs, touted the growth of renewable energy, saying China’s capacity now accounted for 30 percent of the world’s total. Meeting the new goals "reflects China’s willingness to work with other countries to build a vigorous, clean and beautiful world and its responsibility to build a community with a shared future for mankind," he said on Wednesday.

Mr. Xi has previously pledged to increase government support for new technologies, while doing more to fight pollution, protect natural resources and expand the country’s national park networks.

Preserving the Communist Party’s power remains his first priority, but pollution and other environmental threats are increasingly seen as threats to the party’s standing. That was evident in this summer’s devastating floods on the Yangtze River and its tributaries in central China.

"Humankind can no longer afford to ignore the repeated warnings of nature," Mr. Xi said on Tuesday, addressing the General Assembly by video.

China has come under pressure to fight climate change

Mr. Xi’s China is generally impervious to criticisms of its domestic policies, but his government has faced pressure to do more on the warming climate. China’s commitments were raised last week when he met with leaders of the European Union, which had threatened to impose carbon tariffs if China did not reduce its emissions.

The Europeans pressed China to reach peak emissions by 2025, as most European nations have vowed to do. While Mr. Xi stopped short of that, his pledges to move the target before 2030 and to set carbon neutrality as a goal for the first time stood in stark contrast to President Trump’s climate skepticism, which was punctuated by the U.S. withdrawal from the Paris agreement.

Pledging to do more on the climate could at least counterbalance the rising anger China faces in Europe and beyond over its record of oppression in Xinjiang and Tibet, its territorial conflicts in the Himalayas and the South China Sea, military threats toward Taiwan and a sweeping crackdown on Hong Kong’s autonomy.

"The Europeans will be closely watching how serious Xi is, but it was a very clever and well-timed move," Janka Oertel, director of the Asia Program at the European Council on Foreign Relations, said.