October 24, 2008

Scientists Find Greenhouse Gas 4 Times Higher Than Estimated

New measurements released on Thursday show that levels of a powerful greenhouse gas are four times as high as previously thought.

Scientists say about 5,400 metric tons of nitrogen trifluoride are in the atmosphere, with amounts increasing by about 11 percent per year.

Nitrogen trifluoride, a colorless, odorless, nonflammable gas, is used to etch silicon wafers and in some lasers.

Nitrogen trifluoride is 17,000 times more effective at warming the atmosphere than an equal mass of carbon dioxide, although it does not yet contribute much to global warming.

Researchers from the Scripps Institution of Oceanography in La Jolla, California, said it had not been possible to accurately measure this gas before.

Estimates in 2006 had put levels of the gas at less than 1,200 metric tons.

Study leader Ray Weiss and colleagues said they analyzed air samples gathered over the past 30 years under the NASA-funded Advanced Global Atmospheric Gases Experiment.

Weiss said nitrogen trifluoride needs to be regulated, as carbon dioxide is.

"From a climate perspective, there is a need to add nitrogen trifluoride to the suite of greenhouse gases whose production is inventoried and whose emissions are regulated under the Kyoto Protocol, thus providing meaningful incentives for its wise use," he said.

Nitrogen trifluoride is being used more commonly and Michael Prather, an atmospheric chemist at the University of California at Irvine, predicted that more would be found in the atmosphere.

Prather said it is now shown to be an important greenhouse gas. "Now we need to get hard numbers on how much is flowing through the system, from production to disposal," said Prather, who was not involved with the Scripps study.

In response to the growing use of the gas and concerns that its emissions are not well known, scientists recently have recommended adding it to the list of greenhouse gases regulated by Kyoto.


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