Methane is a simple compound made of carbon and hydroge. This gas comes from ordinary sources, like cattle herds and garbage dumps. On a planetary scale it also has a significant impact on climate. As it builds up in the atmosphere, it traps energy from the sun like a layer of insulation. Carbon dioxide does much the same thing-it causes global warming by trapping heat. But as experts struggle to curtail global climate change, a decrease of atmospheric methane might be easier to achieve than proportional drops in carbon dioxide, affording an alternate scenario to policy makers.
Methane is second only to carbon dioxide in contributing to global warming. It is a naturally occurring gas, a product of a variety of biological processes. But in terms of climate change, it is the unnatural concentration of the gas from human induced factors that has researchers concerned. In the case of garbage disposal, methane enters the atmosphere as a byproduct of decomposition. As anaerobic bacteria break down polymers and other carbon based garbage, like the banana peel shown here, methane gets produced as a waste gas. As it enters the atmosphere, it reduces the Earth's ability to cool by absorbing more reflected heat from the planet than would otherwise occur. Other sources of methane production include rice cultivation, industrial production, and cattle herds.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 22.214.171.124.0