Methane—a potent greenhouse gas that could be released in vast quantities as climate change melts Arctic permafrost—has received quite a bit of media attention in the last month. But the coverage has caused a bit of confusion about where the methane is coming from—land or sea—and which source has scientists most worried.

The first round of stories, in early December, followed the publication in the journal Nature of an analysis by forty-one scientists associated with the Permafrost Carbon Network, which found that the amount of organic carbon stored in the perennially frozen ground is 1.7-5.2 times larger than previous estimates. If released, they said, the resultant carbon dioxide and methane could play a much larger role in climate change than deforestation:

“We calculate that permafrost thaw will release the same order of magnitude of carbon as deforestation if current rates of deforestation continue,” the group wrote. “But because these emissions include significant quantities of methane, the overall effect on climate could be 2.5 times larger.”

Methane has about twenty-five times more global-warming potential than carbon dioxide over a 100-year period, and although the scientists acknowledged that it “remains highly uncertain” how much the greenhouse gases emanating from the Arctic will actually accelerate climate change, they stressed that thawing permafrost is “cause for serious concern.” Journalists such as the Associated Press’s Seth Borenstein and Time’s Bryan Walsh did a good job conveying that message, but the Knight Science Journalism Tracker’s Charlie Petit pointed out that they stumbled over one important detail.

Both reporters referred to methane and carbon dioxide being “trapped” in Arctic permafrost, but that’s not quite accurate (Borenstein explained this in the bottom half of his piece; Walsh didn’t). What’s trapped in the permafrost—on land, at least—is organic carbon in the form of ancient, frozen plant and animal matter. As the permafrost thaws, microbes decompose the plant and animal matter and produce methane and/or carbon dioxide depending on local conditions, such as the amount of oxygen present.

This seemingly nitpicking detail is important, because in areas along the Arctic seafloor, methane is trapped in the permafrost in the form of methane hydrates (also referred to as methane clathrates)—basically, methane-laced ice that forms only under high pressures and low temperatures. The second pulse of news stories about Arctic-methane this month focused on this type of deposit, which is found in relatively shallow waters along the coasts of Siberia, Canada, and Alaska.

It resulted from a scoop that Steve Connor—science editor at The Independent, a British paper—picked up while attending the American Geophysical Union’s annual meeting in December to receive an award for outstanding news reporting. The news was that the head of a Russian research team who had been studying the seabed along Russia’s northern coast had spotted “dramatic and unprecedented plumes of methane … bubbling to the surface.”

The team had published a study in 2010 describing significant “methane venting” in the area—which results when permafrost along the seafloor thaws due to the global-warming abetted retreat of insulating sea ice along the surface—but new data the group collected over the summer suggested it had underestimated the amount being vented. This methane also has the potential to accelerate climate change, but critics quickly started poking holes in Connor’s article.

The Knight Science Journalism Tracker’s Petit, who was also at the geophysical union’s meeting to receive an award (for sustained achievement in science journalism), wrote a post explaining how Connor broke away from the press pack at the meeting, and complimenting him for so doing. But “speaking of bubbling methane,” Petit observed, “I am bubbling with methane questions that this story raises.”

First and foremost, Petit wanted to know more about the source of gas. “One or two sentences on what this methane is and whether it is distinct from the kind feared from thawing, terrestrial permafrost would have answered the question,” he wrote.

Indeed, the distinction is important because the level of worry among scientists differs depending on the source—by land or by sea—of the permafrost emissions. Following Connor’s article, Andrew Revkin, who writes the New York Times Dot Earth blog, argued that:

If you read the Independent of Britain, you’d certainly be thinking the worst. The newspaper has led the charge in fomenting worry over the gas emissions, with portentous, and remarkably similar, stories in 2008 and this week.

If you read geophysical journals and survey scientists tracking past and future methane emissions, you get an entirely different picture.

Curtis Brainard writes on science and environment reporting. Follow him on Twitter @cbrainard.