Human industries and their output—oil fields, smokestacks, and cars—are usually thought of as the largest contributors to greenhouse gases. But humans are not the only source of emissions. Microorganisms in the ocean floor have been producing methane, a greenhouse gas 25 times more effective at warming the planet than carbon dioxide, since long before humans evolved. In fact, microorganisms in the seafloor produce 45 teragrams of methane per year, about 10% of the total amount of methane on earth that reaches the atmosphere each year.
While the amount of methane produced by microorganisms in the ocean floor is small relative to the amount produced by humans, it is no less important in driving climate change. And unlike human contributions to climate change, methane emissions from the ocean are not that well understood. This poses a problem for scientists using models to predict how the earth’s climate will change over coming centuries. Multiple small errors in a larger model can ultimately add up and lead to important differences in the model’s predictive capacity.