Siberian wetlands may be releasing more methane due to prolonged above normal temperatures. Photo: Weiting Liu.
After almost a decade of close to zero growth in atmospheric contcentration, methane (a gas 25 times more potent than carbon dioxide, and responsible for about 20% of global warming since the industrial revolution) levels have begun to rise again, scientists are reporting.
One suspected cause of the increase is additional methane being released from high northern latitudes, due to a year long warm spell in Siberia causing more methane than normal to be released from wetlands in the region. However, this would not account for similar emission increases in the Southern Hemisphere.
Whatever the cause, the news is not good for global warming, according to Dr Paul Fraser of the Commonwealth Scientific and Industrial Research Organisation:Global Warming May Further Accelerate
Over recent years, the growth of important greenhouse gases, namely methane and the CFCs, had slowed. This tended to offset the increasing growth rate of carbon dioxide that results mainly from large increases in the consumption of fossil fuels, particularly in the developing world. Now that methane levels have resumed their growth, global warming may accelerate. (Science Codex)
Methane Is Second Most Important Greenhouse Gas
Pre-industrial methane levels were about 700 parts per billion; these have risen to about 1773 parts per billion today. Though the 2007 concentration increase was only an additional 10 parts per billion, Matthew Rigby of MIT says that is a significant jump for such a short period of time. Rigby added,
The thing that’s really surprising is that it’s coming after a period of very level emissions. The worry is that we just don’t understand the methane cycle that well. (Reuters)
Emitted Methane Balanced by Atmospheric, Soil Absorption
Typical sources of methane emission include wetlands, rice fields, cattle, forest and grass fires, natural gas leakage and use, and coal mines. Dr Fraser describes the how the balance between methane emission and absorption has apparently been upset,
This fragile balance has resulted in little growth of methane in the atmosphere. Apparently some sources have been increasing, such as from fossil fuel use, cattle, and rice, while others have been decreasing, particularly natural tropical wetlands. However, over the past year, the total sources have overwhelmed the total sinks, and methane has again started to rise.(Science Codex)
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