Despite widespread concern about climate change, annual carbon dioxide emissions from burning fossil fuels and manufacturing cement have grown 38 percent since 1992, from 6.1 billion tons of carbon to 8.5 billion tons in 2007.
At the same time, the source of emissions has shifted dramatically as energy use has been growing slowly in many developed countries but more quickly in some developing countries, most notably in rapidly developing Asian countries such as China and India.
"The United States was the largest emitter of CO2 in 1992, followed in order by China, Russia, Japan and India," said Gregg Marland of ORNL's Environmental Sciences Division.
"The most recent estimates suggest that India passed Japan in 2002, China became the largest emitter in 2006, and India is poised to pass Russia to become the third largest emitter, probably this year," he added.
The new estimates of CO2 emissions are based on energy data through 2005 from the United Nations, cement data through 2005 from the US Geological Survey, energy data for 2006 and 2007 from BP, and extrapolations by Marland, Gregg and co-authors Tom Boden and Bob Andres of ORNL.
Burning fossil fuels and manufacturing cement, along with deforestation, are the most important human-related sources of carbon dioxide emissions to the atmosphere, according to the researchers. The cement data take into account the breakdown of limestone to produce lime. Researchers also note that the new CO2 data include minor downward revisions of estimates for recent years, but the trends have not changed.