China has clearly overtaken the United States as the world’s leading emitter of carbon dioxide, the main heat-trapping gas produced by human activity, 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.”