A new study has found that agricultural practices, and not fossil fuel production, is to blame for the rise in methane levels in the atmosphere since 2007. A greenhouse gas, methane is a major contributor to climate change.
The study, led NIWA atmospheric scientist Hinrich Schaefer, is considered a breakthrough in understanding the causes of climate change because it rules out fossil fuel production as the major cause behind the rise in methane levels since 2007. Methane in the earth’s atmosphere has increased by about 150 per cent since 1750.
According to a news release, the amount of methane in the atmosphere had been steadily increasing since pre-industrial times but then levelled out between 1996 and 2006. In 2007 it began to rise and continues to do so.
To understand why, a team of scientists from New Zealand, the US and Germany took methane measurements in a number of locations across the world. According to Dr. Schaefer, the scientists could distinguish three different types of methane emissions: one comes from burning organic materials (such as forest fires), a second from fossil fuel production, and a third is formed by microbes from a variety of sources including wetlands, rice paddies and livestock.
When analysing the measurements, the scientists were surprised to rule out fossil fuel production as the culprit behind the rise in methane since 2007. Even though that year coincides with the onset of fracking in the US, increased coal mining and the upswing in the Asian economy, the methane emissions in the atmosphere did not correspond to the type from fossil fuel production.
“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,” explains Dr. Schaefer.
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.”
The findings are important because methane plays an important role in climate change – which means that it is necessary to look at agriculture if we want to reduce methane levels.
But as Dr. Schaefer stressed, it would be wrong to let fossil fuels off the hook. “If fossil fuel production picks up again that may change the situation dramatically.”