Methane Emissions to Increase with Global Warming

The amount of methane released from microorganisms dwelling in lakes and freshwater beds will increase severalfold for each degree Celsius the Earth's temperature rises, according to a new study.

While much attention is given to climate change-linked rises in carbon dioxide, methane is roughtly 30 times more potent as a heat-trapping gas, and as temperatures rise, methane output from freshwater sources - the primary methane emissions source - will will outpace carbon dioxide output.

In freshwater systems, methane is produced as a digestive byproduct of microorganisms that eat organic matter. This process, known as methanogenesis, is a complex amalgamation of temperature, chemical, physical and ecological factors.

Writing in the journal Nature, the scientists suggest that methane emissions from freshwater sources will likely rise with the global temperature. However, the multiple processes that fuel methanogenesis has made it difficult for scientists to account for this phenomenon when creating climate models. Previously, omitted methane emissions from bodies of freshwater such as lakes, swamps, marshes and rice paddies rendered inaccuracies in climate projections.

"The freshwater systems we talk about in our paper are an important component to the climate system," said study co-author Cristian Gudasz from Princeton University. "There is more and more evidence that they have a contribution to the methane emissions. Methane produced from natural or manmade freshwater systems will increase with temperature."

Gudasz and his colleagues analyzed nearly 1,600 temperature and methane-emissions measurements from 127 freshwater ecosystems around the world.

The common theme running through the analysis is that methane generation thrives in high temperatures.

The scientists learned that the state of methane emissions at a 0 degree Celsius scenario would rise 57 times higher when the temperature hit 30 degrees Celsius.

"We all want to make predictions about greenhouse gas emissions and their impact on global warming," Gudasz said. "Looking across these scales and constraining them as we have in this paper will allow us to make better predictions."