[Editors] New greenhouse gas identified

[Elizabeth Thomson]

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New greenhouse gas identified
--Early detection may permit ‘nipping it in the bud’
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For Immediate Release
TUESDAY, MAR. 10, 2009

Contact: Elizabeth A. Thomson, MIT News Office
E: thomson at mit.edu, T: 617-258-5402


CAMBRIDGE, Mass.--A gas used for fumigation has the potential to  
contribute significantly to future greenhouse warming, but because its  
production has not yet reached high levels there is still time to nip  
this potential contributor in the bud, according to an international  
team of researchers.

Scientists at MIT, the Scripps Institution of Oceanography in San  
Diego and other institutions are reporting the results of their study  
of the gas, sulfuryl fluoride, this month in the Journal of  
Geophysical Research. The researchers have measured the levels of the  
gas in the atmosphere, and determined its emissions and lifetime to  
help gauge its potential future effects on climate.

Sulfuryl fluoride was introduced as a replacement for methyl bromide,  
a widely used fumigant that is being phased out under the Montreal  
Protocol because of its ozone-destroying chemistry. Methyl bromide has  
been widely used for insect control in grain-storage facilities, and  
in intensive agriculture in arid lands where drip irrigation is  
combined with covering of the land with plastic sheets to control  
evaporation.

“Such fumigants are very important for controlling pests in the  
agricultural and building sectors,” says Ron Prinn, director of MIT’s  
Center for Global Change Science and a co-author on the new paper. But  
with methyl bromide being phased out, “industry had to find  
alternatives, so sulfuryl fluoride has evolved to fill the role,” he  
says.

Until the new work, nobody knew accurately how long the gas would last  
in the atmosphere after it leaked out of buildings or grain silos.  
“Our analysis has shown that the lifetime is about 36 years, or eight  
times greater than previously thought, with the ocean being its  
dominant sink,” Prinn says. So it would become “a greenhouse gas of  
some importance if the quantity of its use grows as people expect.”  
For now, the gas is only present in the atmosphere in very small  
quantities of about 1.5 parts per trillion, though it is increasing by  
about 5 percent per year. Its newly reported 36-year lifetime, along  
with studies of its infrared-absorbing properties by researchers at  
NOAA, “indicate that, ton for ton, it is about 4,800 times more potent  
a heat-trapping gas than carbon dioxide” says Prinn.

Fortunately, though, “we’ve caught it very early in the game,” says  
Prinn, the TEPCO Professor of Atmospheric Science in MIT’s Department  
of Earth, Atmospheric and Planetary Sciences. The detection was made  
through a NASA-sponsored global research program called the Advanced  
Global Atmospheric Gases Experiment (AGAGE). “In AGAGE, we don’t just  
monitor the big greenhouse gases that everybody’s heard of,” he says.  
“This program is also designed to sniff out potential greenhouse and  
ozone-depleting gases before the industry gets very big.”

The lead author of the research paper is Jens Mühle of Scripps, and  
besides Prinn, the co-authors include Jin Huang, a research scientist  
at MIT’s Center for Global Change Science, Ray Weiss of Scripps, who  
co-directs AGAGE with Prinn, and eight others from Scripps, the  
University of Bristol in the United Kingdom and the Centre for  
Australian Weather and Climate Research.

“Unfortunately, it turns out that sulfuryl fluoride is a greenhouse  
gas with a longer lifetime than previously assumed,” says Mühle. “This  
has to be taken into account before large amounts are emitted into the  
atmosphere.”

Prinn adds that “fumigation is a big industry, and it’s absolutely  
needed to preserve our buildings and food supply.” But identifying the  
greenhouse risks from this particular compound, before many factories  
have been built to produce it in very large amounts, would give the  
industry a chance to find other substitutes at a time when that’s  
still a relatively easy change to implement. “Given human  
inventiveness, there are surely other alternatives out there,” says  
Prinn. He describes this approach as “a new frontier for environmental  
science — to try to head off potential dangers as early as possible,  
rather than wait until it’s a mature industry with lots of capital and  
jobs at stake.”

--END--

Written by David Chandler, MIT News Office
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