Researchers have found that methane stored underground for millions of years in the Arctic is seeping out into the atmosphere and threatening to cause adverse climatic changes by raising the levels of greenhouse gas.

The study documented in the recent edition of the journal, Nature Geoscience, mentions that the release of the ancient gas can hasten the process of global warming.

Methane is one of the most important non-CO2 greenhouse gases and is responsible for nearly as much global warming as all other non-CO2 greenhouse gases put together. The gas comes from various sources including wetlands, rice paddies, cow tummies, coal mines, garbage dumps and even termites.

Drew Shindell, at Nasa's Goddard Institute in New York earlier mentioned that the level of methane has "gone up by 150 percent since the pre-industrial period. So that's an enormous increase. CO2, by contrast, has gone up by something like 30 percent."

The BBC reported that although tracking methane to these various sources is not easy, the researchers on the new Arctic project, led by Katey Walter Anthony from the University of Alaska at Fairbanks (UAF), were able to identify long-stored gas by the ratio of different isotopes of carbon in the methane molecules.

With the help of both aerial and ground-based surveys, the researchers found around 150,000 methane seeps in Alaska and Greenland in lakes along the margins of ice cover.

According to the Metro, Methane leaking from hydrocarbon reservoirs is typically trapped by frozen ground and glaciers. But it is increasingly leaking from areas where permafrost and glaciers are melting, say researchers from the University of Alaska. Warming of the Arctic is responsible for the seeps, the researchers told Nature Geoscience magazine.

"We observed most of these cryosphere-cap seeps in lakes along the boundaries of permafrost thaw and in moraines and fjords of retreating glaciers," the researchers mentioned in the study reports, emphasising the point that warming in the Arctic is releasing this long-stored carbon.

While some of these releases are ancient methane, a few other regions are reportedly emitting much younger gas, presumably formed through decay of plant material in the lakes.