As permafrost melts in polar regions, the process is releasing carbon dioxide, methane and other greenhouse gases into the air. This release could accelerate a rise in average global temperatures.

Permafrost consists of mosses, grasses and soil that remains frozen year-round in the coldest regions of the world. It covers roughly 24 percent of the land area of the Northern Hemisphere, storing 1.5 trillion tons of carbon. That storehouse is twice as great as all the carbon dioxide in the atmosphere today.

As temperatures rise, mosses released from melting permafrost decay, releasing methane into the atmosphere. Areas frozen year-round for thousands of years have started to melt, as average global temperatures rise.

"Most of the current permafrost formed during or since the last ice age and can extend down to depths of more than [2,300 feet] in parts of northern Siberia and Canada. Permafrost includes the contents of the ground before it was frozen, such as bedrock, gravel, silt and organic material," the United Nations Environment Programme (UNEP) wrote in its own study of permafrost. 

Jeff Chanton of Florida State University led a study examining the release of greenhouse gases from melting permafrost. 

"We've known for a while now that permafrost is thawing. But what we've found is that the associated changes in plant community composition in the polar regions could lead to way more carbon being released into the atmosphere as methane," Suzanne Hodgkins, lead author of the paper, said.

Chanton estimated that if all the polar permafrost were to melt, the amount of methane in the atmosphere would be five times current levels. All plants release carbon into the atmosphere as they decay.

Increased production of methane from decaying moss can "cause shifts... toward faster decomposition with an increasing proportion of carbon released as [methane]. This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures," researchers wrote in the article announcing their findings.

Methane is 33 times more effective than carbon dioxide at trapping heat from the sun, leading to global warming. 

Chanton and his team traveled to Sweden several times during the study to examine areas where permafrost is starting to melt, exposing ancient moss. Researchers participating in the study came from the United States, Australia, and Europe. 

The Department of Energy funded the study with a $400,000 grant, according to a press release announcing the findings. 

"The world is getting warmer, and the additional release of gas would only add to our problems," Chanton said.

Study of the release of greenhouse gases from melting permafrost was profiled in the Proceedings of the National Academy of Sciences.