China has clearly overtaken the United States as the world’s leading emitter of carbon dioxide, the main heat-trapping gas, a new study has found, its emissions increasing 8 percent in 2007. The Chinese increase accounted for two-thirds of the growth in the year’s global greenhouse gas emissions, the study found.

The report, released Friday by the Netherlands Environmental Assessment Agency, found that in 2007 China’s emissions were 14 percent higher than those of the United States. In the previous year’s annual study, the researchers found for the first time that China had become the world’s leading emitter, with carbon emissions 7 percent higher by volume than the United States in 2006.

Many experts had been skeptical of the earlier study, whose results were less clear-cut than those released Friday. The International Energy Agency had continued to say only that China was projected to overtake the United States by the end of 2007. Now there is little doubt.

“The difference had grown to a 14 percent difference, and that’s indeed quite large,” said Jos Olivier, a senior scientist at the Dutch agency. “It’s now so large that it’s quite a robust conclusion.”

China’s emissions are most likely to continue growing substantially for years to come because they are tied to the country’s strong economic growth and its particular mix of industry and power sources, the researchers said.

China is heavily dependent on coal and has seen its most rapid growth in some of the world’s most heavily polluting industrial sectors: cement, aluminum and plate glass.

Twenty percent of China’s emissions come from its cement kilns, essential for its construction boom and likely to be working overtime this year amid preparations for the Olympics and rebuilding after last month’s devastating earthquake.

The Dutch agency’s findings were based on recently published information on cement production and on energy use from the oil company BP.

The United States still has a vast lead in carbon dioxide emissions per person. The average American is responsible for 19.4 tons. Average emissions per person in Russia are 11.8 tons; in the European Union, 8.6 tons; China, 5.1 tons; and India, 1.8 tons.

Experts said the new data underscored the importance of getting China to sign on to any new global climate agreement. Neither China nor the United States participated in the current treaty to limit emissions, the Kyoto Protocol, which expires in 2012 and will be replaced by a new agreement to be signed in Copenhagen at the end of 2009.

On Friday in Bonn, Germany, 2,000 world leaders concluded two weeks of negotiations on what kind of agreement should replace the Kyoto Protocol. United Nations leaders told them to “pick up the pace.”

“With a little more than a year to go to Copenhagen, the challenge to come to that agreement remains daunting,” said Yvo de Boer, executive secretary of the United Nations Framework Convention on Climate Change. Late last year, a United Nations panel of scientific experts warned that the world had only a few years to reverse a growing emissions trend in order to avoid severe consequences of global warming, from a large rise in sea level to species death.

“Everyone recognizes that we’re only going to get to an answer by addressing issues in all countries, including China,” Mr. de Boer said.

Still, he added that China had been “acting progressively on environmental policy” in the past year, developing plans to shut down highly polluting small- and medium-size industries and to find more alternative energy, for example.

Orville Schell, director of the Center on U.S.-China Relations at the Asia Society in New York, said the Dutch study “was something of a harbinger of things to come, namely, of China’s uncontested pre-eminence in this world of rapidly growing greenhouse gas emissions.”

The Asia Society has started a bilateral climate change initiative that includes groups like the Pew Center on Global Climate Change and involves leaders in both countries, including Al Gore.

“There cannot be a solution to the global climate change questions without China being integrally involved,” Mr. Schell said. But he added that Chinese leaders would not become more engaged unless the United States also made new commitments.

The Dutch researchers said there were some signs that China’s rapid emissions trajectory would be somewhat blunted this year, although they still predicted rapid growth. Its emissions rose 8 percent in 2007, compared with more than 11 percent annually for the previous two years.

In comparison, emissions in the original 15 European Union member states fell 2 percent in 2007, though Dr. Olivier, at the Dutch agency, cautioned that this drop was at least partly attributable to a warm winter that reduced the need for heating.

But with high oil and gas prices this year, other forces favor emissions growth in the future. High oil prices have created a resurgence in interest in coal-fired power plants for industry, which are heavily polluting.

Eighty percent of the world’s coal demand comes from China, according to the International Energy Agency, which advises industrialized nations on energy policy. But the United States is also a major user of coal to power its industry.

“It is crucial for countries like China and the United States to explore technologies to deal with that,” said Mr. de Boer, referring specifically to projects that would pump emissions underground instead of into the atmosphere.