Carbon dioxide — the greenhouse gas considered most responsible for global warming — has been emitted into the Earth’s atmosphere at a dramatically accelerating pace since 2000, researchers reported Monday.

“Carbon dioxide is rising at a much faster rate than before,” says study co-author Christopher Field, director of the Carnegie Institution’s Department of Global Ecology in California. “In the 1990s, CO{-2} emissions increased by about 1.3% per year. Since 2000, the growth rate has been 3.3% per year.” The researchers calculate that global carbon-dioxide emissions were 35% higher in 2006 than in 1990.

What’s especially troubling, notes lead author Josep Canadell of Australia’s Commonwealth Scientific and Industrial Research Organization, is most climate scenarios used by scientists and policymakers to predict temperature increases are based on the 1.3% rise. Greenhouse gases such as carbon dioxide warm the planet by trapping heat in the atmosphere.

Canadell says that while the Intergovernmental Panel on Climate Change predicts “we will have temperature increases of 3.2 to 7.1 degrees by the end of the century, … we’re well on the way to the higher temperature increase if the emissions keep going up at this rate.”

Higher global temperatures have been predicted to cause rising sea levels, more frequent heat waves and wildfires, and huge losses of ice in the Arctic and Antarctic.

The study was published in this week’s Proceedings of the National Academy of Sciences. It states that carbon released from burning fossil fuels and making cement rose from 7 billion metric tons a year in 2000 to 8.4 billion metric tons in 2006. A metric ton is 2,205 pounds.
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