London: Methane, the second most common
greenhouse gas from human activities after carbon dioxide, is
bubbling out from the frozen Arctic much faster than expected
and could stoke global warming, scientists have warned.
A study by researchers from the University of Fairbanks
in Alaska showed that methane, trapped in the permafrost --
soil at or below the freezing point of water for two or more
years -- over time and now 8 million tonnes of it is seeping
out every year due to rising temperatures.
According to co-author of the study Natalia Shakhova,
"Release of just a small fraction of the methane held in East
Siberian Arctic Shelf sediments could trigger abrupt climate
"Subsea permafrost is losing its ability to be an
"The amount of methane currently coming out of the East
Siberian Arctic Shelf is comparable to the amount coming out
of the entire world`s oceans," she wrote in journal Science.
Shakhova said there was an `urgent need` to monitor the
region for possible future changes since permafrost traps vast
amounts of methane, the Daily Mail reported.
According to Martin Heimann from the Max Planck Institute
there is, however, no proof they are increasing. "These leaks
could have been occurring all the time since the last Ice Age
10,000 years ago."
The release of eight million tonnes of methane a year was
"negligible" compared to global emissions of about 440 million
tonnes, he said.
Around 60 per cent of methane now comes from human
activities like landfills, cattle rearing or rice paddies.
Natural sources such as wetlands make up the rest, along
with poorly understood sources such as the oceans, wildfires
At present, methane concentrations in the Arctic average
about 1.85 parts per million -- highest in last 400,000 years,
the scientists said.
Historically, it has ranged between 0.3 and 0.4 parts per
million in cool periods to 0.6 to 0.7 in warm ones.