Permafrost in the soil and methane hydrates deep in the ocean are large reservoirs of ancient carbon. As soil and ocean temperatures rise, the reservoirs have the potential to break down, releasing enormous quantities of the potent greenhouse gas methane. But would this methane actually make it to the atmosphere?

Researchers at the University of Rochester—including Michael Dyonisius, a graduate student in the lab of Vasilii Petrenko, professor of earth and environmental sciences—and their collaborators studied methane emissions from a period in Earth’s history partly analogous to the warming of Earth today. Their research, published in Science, indicates that even if methane is released from these large natural stores in response to warming, very little actually reaches the atmosphere.

“One of our take-home points is that we need to be more concerned about the anthropogenic emissions—those originating from human activities—than the natural feedbacks,” Dyonisius says.

What are methane hydrates and permafrost?

When plants die, they decompose into carbon-based organic matter in the soil. In extremely cold conditions, the carbon in the organic matter freezes and becomes trapped instead of being emitted into the atmosphere. This forms permafrost, soil that has been continuously frozen—even during the summer—for more than one year. Permafrost is mostly found on land, mainly in Siberia, Alaska, and Northern Canada.

Along with organic carbon, there is also an abundance of water ice in permafrost. When the permafrost thaws in rising temperatures, the ice melts and the underlying soil becomes waterlogged, helping to create low-oxygen conditions—the perfect environment for microbes in the soil to consume the carbon and produce methane.

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