An international study has determined that methane levels in the atmosphere have started to rise after almost eight years of near-zero growth.
According to a report in ABC News, the study involved CSIRO, the Massachusetts Institute of Technology (MIT), Scripps Institution of Oceanography and the University of Bristol.
Dr Paul Fraser of the CSIRO, who co-authored the study, said that samples taken from 12 stations across a global network showed a trend upwards in methane levels.
"After seven years (of zero growth), methane has started to rise again to growth rates of the early 1990s," Fraser said.
The chief research scientist in the Division of Marine and Atmospheric Research said that the increase in methane could lead to an acceleration in global warming.
"If methane concentrations continue to grow at the current rate then it will be once again the second-most important greenhouse gas to control after CO2 over the next few decades," he said.
Fraser said that methane accounts for about 20 percent of all greenhouse gases since the industrial revolution.
It is 20 times more potent than carbon dioxide as a greenhouse gas and comes from sources such as natural wetlands, rice fields, fires, coal mines and natural gas reticulation.
Emissions have been balanced over the past decade by natural sinks that absorb the gas and through oxidation into the atmosphere.
According to Fraser, sources of methane have been growing with drainage of tropical wetlands for agricultural use and increased fossil fuel use.
However, the destruction of natural tropical wetlands removes an important sink from the delicate equation.
"The result is in the past year the total sources have overwhelmed the total sinks, and methane has again started to rise," Fraser said.
This imbalance has resulted in several million tonnes of extra methane in the atmosphere, the research paper said.
The study indicated that the rise in methane concentrations is due in part to increased methane releases in the high latitudes of the Northern Hemisphere.
Fraser said that this could be a one-off anomaly due to a very hot Northern Hemisphere summer in 2007 that would have warmed the wetlands of the tundra increasing methane production.
However, if it is a long-term trend then it is a worrying development.
Surprisingly, the researchers found the methane levels rose simultaneously at all measurement locations across the globe.