CHAMPAIGN, Ill. -- Achieving a reduction in greenhouse-gas emissions that is large enough to mitigate the effects of global warming can be a daunting task. As reported in the Oct. 29 issue of Science, a team of atmospheric scientists, economists and emissions experts has found that by including methane in abatement strategies, the costs of meeting U.S. emission-reduction targets could be lowered.
"In our study, we assessed the potential cost savings of introducing an additional greenhouse gas, methane, into a carbon dioxide emission-reduction strategy," said Katharine Hayhoe, a researcher in atmospheric sciences at the University of Illinois and the lead author of the Science paper. "We estimate that for short-term targets, methane can offset carbon dioxide reductions and reduce U.S. abatement costs by more than 25 percent compared to strategies involving carbon dioxide alone."
The recent Kyoto Protocol calls for a 7 percent reduction in U.S. greenhouse-gas emissions by the budget period 2008-2012, Hayhoe said. As yet, the United States has not agreed to the terms of the protocol. However, using the latest carbon dioxide and methane abatement costs for the United States, the researchers showed that a joint control strategy could meet the protocol's target and timetable at a lower overall cost when compared with previous estimates that account for carbon dioxide only.
There are five major sources of man-made methane in the United States -- landfills, coal mining, livestock, manure systems and the production and transmission of natural gas. A significant amount of these emissions can be reduced through the use of currently available, economically justified and easily verified options. Such options include capturing the methane and recovering the cost of the emission-reduction technology by selling the gas or using it to displace other energy inputs.
"Most of these methane abatement technologies can be quickly implemented," said Atul Jain, a U. of I. atmospheric scientist. "Methane emission reductions are most effective for smaller reduction targets, where mitigation technologies with low or zero net costs account for much of the abatement."
Because of its short atmospheric response time of about 12 years, methane concentrations will respond quickly to emission reductions, producing an immediate and significant impact on climate change, Jain said. In contrast, the effect of reductions in carbon dioxide emissions, which are slowly removed from the atmosphere over 50-200 years, will not be seen for some time.
"Methane is the second-most important greenhouse gas. Together, methane and other non-carbon dioxide gases are currently responsible for about 40 percent of the global warming problem," said Don Wuebbles, a U. of I. professor of atmospheric sciences. "However, reducing carbon dioxide emissions is still the primary means of achieving significant long-term mitigation of climate change."
Collaborators on the study included Hugh Pitcher and Chris MacCracken of the Pacific Northwest National Laboratory, Reid Harvey and Dina Kruger of the U.S. Environmental Protection Agency, and Michael Gibbs of the ICF Kaiser Consulting Group.
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