China passed the United States as the No. 1 carbon dioxide emitter about six years ago and "the gap is widening, it's huge," said Appalachian State University professor Gregg Marland, who helps track worldwide emissions for the U.S. Energy Department.
When developed countries around the world in 1997 agreed to limit their greenhouse gas emissions, developing countries, including China, were exempted.
U.S. Energy Department statistics say that China gets 70 percent of its energy from coal, compared with 20 percent in the United States. China is also a world leader in the production of cement, a process that also causes greenhouse emissions.
Associated Press writer Louise Watt in Beijing contributed to this report.
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