Potent Greenhouse Gas More Prevalent than Thought

By Andrea Thompson, Senior Writer

A potent greenhouse gas is at least four times more prevalent in the atmosphere than was previously estimated, a new study reports.

Using new analytical techniques, a research team in California made the first atmospheric measurements of nitrogen trifluoride, which is thousands of times more effective at warming the atmosphere than an equal amount of carbon dioxide (though carbon dioxide is much more prevalent, and therefore still the key greenhouse gas of concern in terms of global warming).

In 2006, the amount of nitrogen trifluoride in the atmosphere, which could not be detected using previous techniques, was estimated at less than 1,322 short tons (1,200 metric tons).

The new research, funded by NASA and detailed in the Oct. 31 issue of the journal Geophysical Research Letters, found that the actual amount was 4,630 short tons (4,200 metric tons) in 2006. Currently, about 5,950 short tons (5,400 metric tons) is estimated to be in the atmosphere. The estimates indicate that the amount of gas in the atmosphere is increasing by about 11 percent per year.

Emissions of nitrogen trifluoride were thought to be so low that the gas was not considered a significant contributor to global warming. It was not covered in the Kyoto Protocol, the 1997 agreement signed by 182 countries to reduce greenhouse gases.

Nitrogen trifluoride is about 17,000 times more powerful at trapping heat than is carbon dioxide, though current emissions of the gas only contribute about 0.04 percent of the total global warming effect contributed by human-produced carbon dioxide emissions.

Nitrogen trifluoride is one of several gases used during the manufacture of liquid crystal flat-panel displays, thin-film photovoltaic cells and microcircuits. Many industries used it as a replacement for perfluorocarbons, another type of potent greenhouse gas, because it was thought that only about 2 percent of the nitrogen trifluoride used escaped into the atmosphere.

Scientists have recently recommended adding nitrogen trifluoride to the list of greenhouse gases regulated by Kyoto in response to its growing use and concerns that its emissions are not well known.

"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," said study leader Ray Weiss of the Scripps Institution of Oceanography in La Jolla, Calif.

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