The concentration of methane in the atmosphere has been increasing for more than a decade and now appears to be accelerating. The rising concentration is worldwide, but is more pronounced in the tropics and northern mid-latitudes. What has caused this increase is not yet well understood. It is almost certainly due to rising emissions of the gas, but a decline in the ability of atmospheric oxidative mechanisms to breakdown methane is also possible.
What is alarming is that this increase in emissions was not anticipated in the preparation of the greenhouse gas emissions scenarios that are compliant with the targets of the Paris Agreement.
A research article just published by the American Geophysical Union paints a disturbing picture of the impact on global warming if atmospheric concentrations of methane continue to rise. At present rates, the additional global warming impact of the methane may significantly negate or even reverse progress in reducing global CO2 emissions. This effect may fatally undermine efforts to meet the target of the 2015 UN Paris Agreement on climate change to limit warming to no more than 2°C.
But strangely, the source of the rising levels of this powerful greenhouse gas is something of a mystery.
Where’s it coming from?
Methane is emitted from both anthropogenic sources (primarily the oil and gas industry and large-scale cattle production) and from natural sources such as wetlands. The table below shows the range of annual emissions from both groups of sources.
By far the largest source of emissions of methane is from wetlands. Emissions from the oil and gas industries and from livestock are about equal in second place.
The article in the American Geophysical Union offers three possible explanations for the global increase in atmospheric levels of methane:
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