Potent greenhouse gas more common than estimated: study

Yahoo News 23 Oct 08;

WASHINGTON (AFP) – A potent greenhouse gas many thousands of times more effective at warming the world's atmosphere than carbon dioxide (CO2) is four times more prevalent than previously thought, according to a study released Thursday.

Researchers using a new NASA-funded measurement network discovered there was 4,200 metric tons of the gas nitrogen trifluoride in the atmosphere in 2006, not 1,200 tons as previously estimated for that year.

In 2008 there are 5,400 metric tons of the gas in the atmosphere, an average of an 11 percent tonnage increase per year, said Ray Weiss, head of the research team from the Scripps Institution of Oceanography in La Jolla, California.

Nitrogen trifluoride, which could not be detected in the atmosphere using previous techniques, is 17,000 times more potent as a global warming agent than a similar mass of CO2.

Emissions of nitrogen trifluoride, which is one of several gases used during the manufacture of liquid crystal flat-panel TV displays and electronic microcircuits, were previously considered so low that the gas was not thought to be a significant potential contributor to global warming.

As such the gas was not covered by the Kyoto Protocol, the 1997 agreement to reduce greenhouse gas emissions signed by 182 countries, but not by some industrialized nations including the United States.

"Accurately measuring small amounts of nitrogen trifluoride in air has proven to be a very difficult experimental problem, and we are very pleased to have succeeded in this effort," Weiss said.

The study, published in the October 31 edition of the American Geophysical Union's Geophysical Research Letters, notes that together with the gas being more potent than CO2 at trapping solar heat within the atmosphere, it also survives in the atmosphere around five times longer than CO2.

At present, however, current nitrogen trifluoride emissions contribute only around 0.15 percent of the total global warming effect caused by human-produced CO2 emissions.

Greenhouse Gas Four Times More Than Thought – Study
PlanetArk 24 Oct 08;

WASHINGTON - Levels of a powerful greenhouse gas are four times as high as previously thought, according to new measurements released on Thursday.

New analytical techniques show that about 5,400 metric tons of nitrogen trifluoride are in the atmosphere, with amounts increasing by about 11 percent per year.

Ray Weiss of the Scripps Institution of Oceanography in La Jolla, California, and colleagues said it had not been possible to accurately measure this gas before.

They said 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.

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

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

Writing in Geophysical Research Letters, 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.

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

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

(Reporting by Maggie Fox, editing by Philip Barbara)