NEW research finding agriculture and not fossil fuels is the major cause of rising methane levels in the atmosphere over the last decade.
Research conducted by New Zealand’s National Institute of Water and Atmospheric Research (NIWA) concluded that increasing levels of methane since 2007 were most likely due to agricultural practices, and not fossil fuel production as previously thought.
In a paper published online in the prestigious international journal Science, NIWA scientists ruled out fossil fuel production as the major cause in the rise of methane levels in the atmosphere since 2007.
The research, led by NIWA atmospheric scientist Hinrich Schaefer, has concluded that increasing levels of methane in the atmosphere are most likely due to agricultural practices.
Methane is a greenhouse gas and believed to be one of the major contributors to climate change.
The amount of methane in the earth’s atmosphere is estimated to have increased by about 150% since 1750.
NIWA scientists first noticed trends occurring in the data collected at NIWA’s clean air monitoring stations at Baring Head in Wellington and Arrival Heights in Antarctica.
With only Southern Hemisphere data to go on, the scientists began to collaborate with the University of Colorado in the US, and Heidelberg University in Germany whose scientists were taking similar measurements in a number of locations across the world.
“We wanted to put all the data together, then calculate the global average for each year and look at how that has changed over time,” Dr Schaefer said.
Between 1999 and 2006 scientists observed a plateau in the amount of methane in the atmosphere. The amount had been steadily increasing since pre-industrial times but then levelled out for about seven years, most likely due to the economic collapse in the Soviet Union.
After 2006 it began to rise again and continues to do so.
The scientists can distinguish three different types of methane emissions from the burning of organic material, such as forest fires; burning hydrocarbons; and from methane formed by microbes which come from a variety of sources such as wetlands, rice paddies and livestock.
Dr Schaefer said it was surprising to see that methane from fossil fuels has not increased given from 2006 at that time the US started hydraulic fracturing to unlock shale oil and gas, the economy in Asia picked up again and coal mining increased around the world.
Previously published studies had determined that the methane originated from an area that includes South East Asia, China and India – regions that are dominated by rice production and agriculture.
“From that analysis we think the most likely source is agriculture,” he said.
“If we want to mitigate climate change, methane is an important gas to deal with. If we want to reduce methane levels this research shows us that the big process we have to look at is agriculture.”
He warned that increasing temperatures could also lead to more natural methane being produced from wetlands, the permafrost and ice-like structures in ocean sediments.
“Which means that global warming could result in more methane being produced from these natural sources. You could have a situation where humans are causing global warming which causes natural methane sources to emit more methane, contributing to further warming,” Dr Schaefer said.
However, Dr Schaefer stressed it would be wrong to conclude that the study gives fossil fuel a clean bill.