New Greenhouse Gas: MIT Researchers Identify Potent New Greenhouse Gas

New Gas: MIT Researchers Identify Potent New Greenhouse Gas
March 11, 2009

http://blogs.wsj.com/environmentalcapital/2009/03/11/new-gas-mit-researchers-identify-potent-new-greenhouse-gas/
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The unintended law of consequences strikes again. The 20-year old campaign to save the ozone layer has led to the widespread industrial use of a greenhouse gas 4,800 times more potent than carbon dioxide.

The 1987 Montreal Protocol was established to limit emissions of chlorofluorocarbons and other gases that deplete the ozone layer, the big worry in the 1980s. One of the targeted compounds was methyl bromide, which was widely used in fumigation to kill weevils and mice and other pests that threaten food supplies. Methyl bromide was phased out in 2005.

Dow Chemical´s AgroSciences unit came to the rescue, dusting off research on an old compound called sulfuryl fluoride, which has now become the standard fumigant.

Just one problem, say researchers at MIT: Sulfuryl fluoride lasts a lot longer in the atmosphere than expected and is a more potent greenhouse gas than carbon dioxide. The good news is that the concentration of Dow´s new fumigant in the atmosphere is still tiny. The researchers will publish their findings, which were compiled with the help of Dow AgroSciences, tomorrow in the Journal of Geophysical Research.

When Dow was pressing for EPA approval of sulfuryl fluoride in 2002 (eventually given in 2004), it didn´t think the new compound presented any global warming threat. In a technical bulletin published then, Dow said:

The relatively small amounts of sulfuryl fluoride released are calculated to have virtually no impact on the global atmosphere. Standard atmospheric modelling indicates that sulfuryl fluoride will have an insignificant contribution to global warming because of the low sulfuryl fluoride to carbon dioxide ratio (< ;0.0001).

The new findings may cause dismay for an industry that just finished complying with one environmental imperative only to find that the cure might have been worse than the disease. But at least the new findings come soon enough to make changes without too much pain, said Ron Prinn, director of MIT´s Center for Global Change Science and a co-author on the new paper. It´s "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," he said in a statement.

And making the first switch from methly bromide to sulfuryl fluoride hasn´t exactly kneecaped the fumigation business-the new compound is cheaper and more effective than what it replaced, meaning the environmental imperative also carried business benefits.

The whole imbroglio does underscore how tough it is to foresee the consequences of wide-reaching environmental regulations. The Montreal Protocol proved very effective at curbing ozone-killing emissions. It also proved surprisingly effective-five times more than the Kyoto Protocol-at reducing emissions of known greenhouse gases, which it wasn´t even meant to do.

But saving the ozone layer may slightly exacerbate some aspects of global warming, the Intergovernmental Panel on Climate Change found. Some ozone-depleting gases lead to warming, and some-like methyl bromide in particular-help cool temperatures.