Methane emissions will leap as Earth warms, study finds

Jonathan Marker | Science Recorder | March 27, 2014

Methane emissions will leap as Earth warms, study finds

The researchers’ findings suggest that methane emissions from freshwater systems will likely rise with the global temperature.

A new study announced by researchers at Princeton University found that, while carbon dioxide has been touted as the top dog of greenhouse gases, methane is approximately 30 times more potent as a heat-trapping atmospheric gas.

The new study appears in the latest issue of the journal Nature, which indicates that for each degree the Earth’s temperature increases, the amount of methane entering the atmosphere from microorganisms in lake sediment and freshwater wetlands will spike several times.  The rise in temperature will lead to a relative increase of methane emissions that will outpace that of carbon dioxide from these sources.

According to Cristian Gudasz, a visiting postdoctoral research associate in Princeton’s Department of Ecology and Evolutionary Biology and coauthor of the Nature study, the findings compress the complex and varied process by which methane, presently the third most prevalent greenhouse gas after carbon dioxide and water vapor, enters the atmosphere into a measurement scientists can use.

In freshwater systems, methane is produced as microorganisms digest organic matter in a process known as “methanogenesis.”  According to the U.S. Geological Survey, this process occurs from the interactions of a range of temperature, chemical, physical and ecological factors that enable bacteria to convert methanogenic substrates into methane and carbon dioxide.

Gudasz said that the researchers’ findings suggest that methane emissions from freshwater systems will likely rise with the global temperature.  However, not knowing the degree of methane input from such a widely dispersed ecosystem that includes lakes, swamps, marshes and rice paddies leaves a hole in climate projections.

To supply a simple and accurate way for climate modelers to account for methanogenesis, Gudasz and his colleagues analyzed almost 1,600 measurements of temperature and methane emissions from 127 freshwater ecosystems around the world.

The common effect? Freshwater methane generation thrives on high temperatures.  Methane emissions at 0 degrees Celsius would rise 57 times higher when the temperature reached 30 degrees Celsius, the researchers report.  The researchers’ results translated to a temperature dependence of 0.96 electron volts (eV), which is an indication of the temperature-sensitivity of the methane-emitting ecosystems.


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