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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."


About the Researcher :

1. Ronald G. Prinn
Professor of Atmospheric Science,
Department of Earth, Atmospheric and Planetary Sciences (EAPS);
Director, Center for Global Change Science (CGCS);
Co-Director of the Joint Program on the Science and Policy of Global Change (JPSPGC)
Massachusetts Institute of Technology, Cambridge MA 02139, U.S.A.

Professor Prinn's research interests incorporate the chemistry, dynamics, and physics of the atmospheres of the Earth and other planets, and the chemical evolution of atmospheres. He has been a faculty member at MIT since 1971, and headed the MIT Department of Earth, Atmospheric and Planetary Sciences from 1998 to 2003. He is currently involved in a wide range of projects in atmospheric chemistry and biogeochemistry, climate science, and integrated assessment of science and policy regarding climate change. He leads the Advanced Global Atmospheric Gases Experiment (AGAGE), in which the rates of change of the concentrations of the trace gases involved in the greenhouse effect and ozone depletion have been measured continuously over the globe for the past three decades. He is pioneering the use of inverse methods, which use such measurements and three-dimensional models to determine trace gas emissions and understand atmospheric chemical processes, especially those processes involving the oxidation capacity of the atmosphere. He is also working extensively with social scientists to link the science, economics and policy aspects of global change. He has co-led the development of a unique integrated global system model coupling economics, climate physics and chemistry, and land and ocean ecosystems, which is used to estimate uncertainty in climate predictions and analyze proposed climate policies. He has made significant contributions to the development of national and international scientific research programs in global change. He served as one of the Lead Authors in the Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC) published in 2007. He has served as Chairman for Atmospheric and Hydrospheric Sciences of the American Association for the Advancement of Science (AAAS), and has chaired the Steering Committees for the IGBP/IAMAP International Global Atmospheric Chemistry Project, the U.S. National Research Council (NRC) Committee on Earth Sciences, and the U.S. Global Tropospheric Chemistry Program. He has been a member of the Steering Committees of the International Geosphere-Biosphere Program (IGBP), and the NASA Network for Detection of Atmospheric Composition Change, and a member of the IAMAP International Commission on Atmospheric Chemistry and Global Pollution, the NRC Space Science Board, the NRC Committee for the International Geosphere-Biosphere Program, the NASA Space Science and Applications Advisory Committee, and the NASA Earth System Sciences Committee. He has twice testified to the United States Congress on climate change science and its implications for policy. He is a Fellow of the American Geophysical Union (AGU), a recipient of AGU's Macelwane Medal, and a Fellow of the AAAS. He has published some 200 peer-reviewed scientific papers, co-authored Planets and their Atmospheres: Origin and Evolution (Academic Press), and edited or co-edited Global Atmospheric-Biospheric Chemistry (Plenum), Atmospheric Chemistry in a Changing World (Springer), and Inverse Methods in Global Biogeochemical Cycles (AGU). Education: Sc.D., 1971, MIT; M.S., 1968, B.S., 1967, University of Auckland, New Zealand.

Contact Information of Prinn:

Email: rprinn@mit.edu
Phone: (617) 253-2452
Office: Bldg. 54-1312A

2. Dr. Jin Huang

Research Scientist, Center for Global Change Science
 

Affiliation(s):

MIT Center for Global Change Science;
Advanced Global Atmospheric Gases Experiment

Education:

Ph.D., Atmospheric Science, Massachusetts Institute of Technology, 2000
M.S., Atmospheric Environment, Nanjing University, Nanjing, China, 1993
B.S., Atmospheric Environment, Nanjing University, Nanjing, China, 1991

Research Interests:

Dr. Huang's research involves modeling the atmospheric lifetime and transport of various greenhouse and ozone depleting gases, and the optimal estimation of trace gas emissions using inverse methods including Kalman filtering. Her recent work has focused on estimating the regional distributions of nitrous oxide, and investigation of the possible polar sources of methyl chloroform. She is also investigating the possible causes of global trends in the sources and sinks of the hydroxyl radical, OH. She is an active participant of the Advanced Global Atmospheric Gases Experiment (AGAGE).

Contact Information of Huang:

Office:54-1414
Phone:617-253-6783
Email: jhuang@mit.edu
Homepage: http://paoc.mit.edu/paoc/people/person.asp?position=Researcher&who=jhuang