Monday, August 02, 2021

The risk of a “methane bomb”

 As predicted, the warming of Russia's tundra and permafrost is releasing methane gas, a more potent greenhouse gas than CO2.

Satellite data indicated that fossil methane gas leaked from rock formations known to be large hydrocarbon reservoirs after the heatwave, which peaked at 6C above normal temperatures. Previous observations of leaks have been from permafrost soil or under shallow seas.  Emissions of the potent greenhouse gas are currently relatively small but climate scientists say further research is urgently needed.

The risk of a “methane bomb” – a rapid eruption of huge volumes of methane causing cataclysmic global heating – is minimal in the coming years. There is little evidence of significantly rising methane emissions from the Arctic and no sign of such a bomb in periods that were even hotter than today over the last 130,000 years. However, if the climate crisis worsens and temperatures continue to rise, large methane releases remain a possibility in the long term and must be better understood.

Methane is 84 times more powerful in trapping heat than carbon dioxide over a 20-year period and has caused about 30% of global heating to date. Its concentration in the atmosphere is now at two and a half times pre-industrial levels and continuing to rise, but most of this has come from fossil fuel exploitation, cattle, rice paddies and waste dumpsMethane releases have been considered a possible climate tipping point, in which emissions of the gas cause further warming, which in turn drives even more releases.

Prof Nikolaus Froitzheim, at Rhenish Friedrich Wilhelm University of Bonn, Germany, and who led the Siberian research, said: “We observed a significant increase in methane concentration starting last summer. This remained over the winter, so there must have been a steady steady flow of methane from the ground. At the moment, these anomalies are not of a very big magnitude, but it shows there is something going on that was not observed before and the carbon stock of fossil gas is large." He continued, “We don’t know how dangerous methane releases are, because we don’t know how fast the gas can be released. It’s very important to know more about it,” Froitzheim said. 

If, at some point in the future, large global temperature rises lead to a big volume being released, the researcher added,  “This methane would be the difference between catastrophe and apocalypse.”

The study concluded with the suggestion that “permafrost thaw does not only release microbial methane from formerly frozen soils but also, and potentially in much higher amounts, fossil methane from reservoirs below. As a result, the permafrost–methane feedback may be much more dangerous than suggested by studies accounting for microbial methane alone.”

Climate crisis: Siberian heatwave led to new methane emissions, study says | Climate change | The Guardian

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