Farming, not hydraulic fracturing, is responsible for the rise in methane levels in the atmosphere since 2007, according to research from the New Zealand National Institute of Water and Atmospheric Research (NIWA).
The amount of methane, a greenhouse gas and a major contributor to climate change, in the earth’s atmosphere is estimated to have grown by about 150 percent since 1750, according to a March 11 NIWA press statement. Between 1999 and 2006, scientists observed a plateau in the amount of methane in the atmosphere after a steady increase since pre-industrial times. However, methane levels start rising again after 2006, and they continue to grow today.
NIWA scientists first noticed trends occurring in the data gathered at NIWA’s clean air monitoring stations at Baring Head in Wellington, N.Z. and Arrival Heights in Antarctica. With only Southern Hemisphere data to go on, NIWA scientists started working with scientists at U.S.-based University of Colorado and Germany’s Heidelberg University. Scientists at these two schools also were taking similar measurements in a number of locations worldwide.
The scientists sought to determine if there were sources of methane that diminished when the plateau started in 1999, what these sources were, and what had been driving renewed growth in methane since 2006. The scientists gathered the data, then calculated the global average for each year and looked at how that average has changed over time.
“We found we could distinguish three different types of methane emissions,” said Dr. Hinrich Schaefer, an NIWA atmospheric scientist who led the study, in the press statement. One is the burning of organic material, such as forest fires. Another is fossil fuel production, and the third is formed by microbes that comes from a variety of sources such as wetlands, rice paddies and livestock.
The economic collapse of the Soviet Union – which occurred around the time that methane emissions plateaued – caused Soviet oil production to decline dramatically. This factor could be detected in the atmospheric analysis.
Scientists were not surprised to see the decline in Soviet production, but were surprised to see that analysis of data since 2006 rules out fossil fuel production as the source of methane rising again. Around 2006, hydraulic fracturing started to rise in the United States, Asia’s economy picked up again, and coal mining increased. But these changes were not reflected in the atmosphere.
“Our data indicate that the source of the increase was methane produced by bacteria, of which the most likely sources are natural, such as wetlands or agricultural, for example, from rice paddies or livestock,” said Schaefer.
Previous studies also have determined that methane originated from an areas that includes South East Asia, China and India – regions that are dominated by rice production and agriculture. From that analysis, Schaefer said he and other researchers concluded that agriculture was the most likely source of the methane emission growth.
While Schaefer said it would be wrong to conclude that the study gives fossil fuels a clean bill, he noted that the agricultural process is the major process that needs to be examined to reduce methane levels.
Another factor to consider is that naturally produced methane sources are particularly sensitive to changes in climate. Schaefer noted that wetlands produce more methane if there is more rain and the ground is warmer. Thawing permafrost produces methane, and methane is also found in ice-like structures in ocean sediments. This means global warming could result in more methane being produced from these natural resources.
“You could have a situation where humans are causing global warming which causes natural methane sources to emit more methane, contributing to global warming,” Schaefer commented. “We don’t see that, maybe not yet. Our findings at least give us an angle to tackle the problems.”
The research findings were recently published in the international journal Science.
The rise in hydraulic fracturing in the United States expanded U.S. oil and gas production to record levels, but also raised concerns by environmental groups and the Obama administration about the amount of methane released into the air through the fracking process. Last week, the U.S. Environmental Protection Agency said it would expand its methane emissions rules for oil and gas wells. The move is part of a bilateral agreement between the United States and Canada to address climate change by reducing methane emission by 40 to 45 percent below 2012 levels by 2025 from the oil and gas sector. Oil and gas industry trade groups have criticized the EPA’s expansion of regulations, saying that investment in innovative technology has allowed industry to produce more oil and gas while methane emissions have declined.
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