A Florida State University oceanographer is pointing out another environmental threat from the Gulf oil spill that has been little discussed until now: the potential for tons of methane, a powerful greenhouse gas, to make its way into the Earth’s atmosphere, thereby increasing the rate of global warming.

Jeff Chanton is the John Widmer Winchester Professor of Oceanography in the university’s new Department of Earth, Ocean and Atmospheric Science. In an interview published June 16 on the popular website The Huffington Post, he was quick to point out that the immediate short-term threat to the ecosystem in the Gulf, is, of course, the oil itself. But, he added, “Methane is undeniably bubbling out with this oil and escaping to the atmosphere. This will exacerbate the greenhouse effect.”

In the article, environmental blogger Jennifer Grayson writes that methane is what triggered the explosion that caused the Deepwater Horizon to burn and sink in the first place. That explosion unleashed a torrent of crude into the Gulf of Mexico that has now surpassed the Exxon Valdez as the worst oil spill in U.S. history. The gas also is still being released along with the oil: According to BP scientists, the mixture spewing from the ocean floor is about 40 percent natural gas (read: mostly methane) and 60 percent petroleum compounds.

Methane is a greenhouse gas that is 23 times more powerful than carbon dioxide. According to the U.S. Environmental Protection Agency, methane concentrations in the atmosphere have more than doubled over the past two centuries, mostly due to human activity.

How much the methane being released from the Deepwater Horizon site will affect global warming isn’t clear. But based on Chanton’s recent research looking at natural oil seeps on the sea floor, he estimates that anywhere from 10 percent to 50 percent of the methane released might make its way into the air. This, he says, is because the oil actually forms a protective coating around the methane bubbles, allowing the gas to escape to the surface instead of being dissolved in seawater and consumed by bacteria.

“We looked at several sites this past summer, and at one of the sites, the natural seep was very oily,” Chanton said. “At the site that was very oily, we did find elevated methane concentrations in the atmosphere over the site. But another site that was more shallow, where the bubbles were not oily, we didn’t see that. So the oil helps the methane get to the surface by kind of armoring the bubbles and then they don’t dissolve as much.”