Potent Greenhouse Gas More Common in Atmosphere Than Estimated
- From: baalke@xxxxxxxxxxxxx
- Date: Thu, 23 Oct 2008 15:08:55 -0700 (PDT)
Oct. 23, 2008
Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@xxxxxxxx
Robert Monroe/Mario Aguilera
Scripps Institution of Oceanography, La Jolla, Calif.
858-534-3624
scrippsnews@xxxxxxxx
RELEASE: 08-268
POTENT GREENHOUSE GAS MORE COMMON IN ATMOSPHERE THAN ESTIMATED
WASHINGTON -- New research indicates a powerful greenhouse gas is at
least four times more prevalent in the atmosphere than previously
estimated. The research, based on data from a NASA-funded measurement
network, examined nitrogen trifluoride, which is thousands of times
more effective at warming the atmosphere than an equal mass of carbon
dioxide.
Using new analytical techniques, Ray Weiss of the Scripps Institution
of Oceanography in La Jolla, Calif., led a team of researchers in
making the first atmospheric measurements of nitrogen trifluoride.
The amount of the gas in the atmosphere, which could not be detected
using previous techniques, had been estimated at less than 1,200
metric tons in 2006. The new research shows the actual amount was
4,200 metric tons. In 2008, about 5,400 metric tons of the gas are in
the atmosphere, a quantity that is increasing at a rate of about 11
percent per year.
"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 research
will be published Oct. 31 in the American Geophysical Union's
Geophysical Research Letters.
Emissions of nitrogen trifluoride were thought to be so low that the
gas was not considered a significant potential contributor to global
warming. It was not covered by the Kyoto Protocol, the 1997 agreement
to reduce greenhouse gas emissions signed by 182 countries. The gas
is 17,000 times more potent as a global warming agent than a similar
mass of carbon dioxide. It survives in the atmosphere about five
times longer than carbon dioxide. However, current nitrogen
trifluoride emissions contribute only about 0.15 percent of the total
global warming effect caused by current human-produced carbon dioxide
emissions.
Nitrogen trifluoride is one of several gases used during the
manufacture of liquid crystal flat-panel displays, thin-film solar
cells and microcircuits. Many industries have used the gas in recent
years as an alternative to perfluorocarbons, which also are potent
greenhouse gases, because it was believed that no more than two
percent of the nitrogen trifluoride used in these processes escaped
into the atmosphere.
The Scripps team analyzed air samples gathered during the past 30
years, including samples from the NASA-funded Advanced Global
Atmospheric Gases Experiment network of ground-based stations. The
network was created in the 1970s in response to international
concerns about chemicals depleting the ozone layer. It is supported
by NASA as part of its congressional mandate to monitor
ozone-depleting trace gases, many of which also are greenhouse gases.
Air samples are collected at several stations around the world. The
Scripps team analyzed samples from coastal clean-air stations in
California and Tasmania for this research.
The researchers found concentrations of the gas rose from about 0.02
parts per trillion in 1978 to 0.454 parts per trillion in 2008. The
samples also showed significantly higher concentrations of nitrogen
trifluoride in the Northern Hemisphere than in the Southern
Hemisphere, which the researchers said is consistent with its use
predominantly in that hemisphere. The current observed rate of
increase of nitrogen trifluoride in the atmosphere corresponds to
emissions of about 16 percent of the amount of the gas produced
globally.
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.
"As is often the case in studying atmospheric emissions, this study
shows a significant disagreement between 'bottom-up' emissions
estimates and the actual emissions as determined by measuring their
accumulation in the atmosphere," Weiss said.
For more information about NASA and agency programs, visit:
http://www.nasa.gov
-end-
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