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Fifty-six million years ago, one of the world’s greatest mass extinctions rocked the planet as temperatures soared and greenhouse gases flooded both the air and the sea. The cause of this sharp spike in greenhouse gas concentrations, some researchers say, was a sudden release of methane from rocky stores deep below the ocean waves. And though other researchers call this idea into question, the presumed threat of stored methane means that any discussion of methane can devolve into end-of-the world anxiety.

Take the discussion around this new study, published in Nature by Southern Methodist University professor Matthew Hornbach and lead by graduate student Benjamin Phrampus. The study found that substantial stores of frozen methane gas, deep within the sea floor off the eastern coast of the United States, are melting. The thaw was “probably caused solely by warming of the ocean over the past few thousands years,” Juergen Mienert writes in Nature. Long-term shifts in the temperature or location of the Gulf Stream have been going on for around 5,000 years, the study suggests, and these changes are destabilizing 2.5 gigatonnes of methane hydrate—a methane gas molecule trapped in a cage of frozen water.

The worry here is that if sea water temperatures rise and these frozen stores thaw, they will liberate methane, a potent greenhouse gas, into the atmosphere. As NBC News’ Miguel Llanos writes: “[S]ince methane is even more potent than carbon dioxide as a global warming gas, the researchers said, any large-scale release could have significant climate impacts.” A boost to the greenhouse effect could cause more warming, causing more hydrates to thaw, which in turn could send climate change spiraling out of control. But whether the finding is a portend of climate doom, as Llanos implies, however, is not so certain.

The United States Geological Survey says that though methane hydrate stores are common along the world’s coastlines, “recent research indicates that most of the world’s gas hydrate deposits should remain stable for the next few thousand years. Of the hydrates likely to become unstable, few are likely to release methane that could reach the atmosphere and intensify global warming.” For methane gas to make it from the sea floor to the air (where it could have an effect on climate change) it would need to bubble up through the water, a feat that sees large amounts of the methane gas dissolve in the cold ocean water and never make it to the surface.

In Nature, Virginia Gewin says:

Whether that methane would make it to the atmosphere and worsen global warming is unclear, but scientists think that it is unlikely. “We don’t need to worry about any huge blow of methane into the atmosphere,” says Carolyn Ruppel, a geophysicist at the US Geological Survey in Woods Hole, Massachusetts.

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