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Science, Evolution, and Creationism, by the National Academies, focuses on teaching evolution in today's classrooms. Check out the other publications in our online store.
Shown here are four representations chemists use for methane. In the colored models, carbon is light gray and hydrogen is white.
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Windows to the Universe original artwork by Randy Russell.

Methane - CH4

Methane is gas that is found in small quantities in Earth's atmosphere. Methane is the simplest hydrocarbon, consisting of one carbon atom and four hydrogen atoms. Methane is a powerful greenhouse gas.

Methane is flammable, and is used as a fuel worldwide. It is a principal component of natural gas. Burning methane in the presence of oxygen releases carbon dioxide and water vapor:

CH4 + 2 O2 → CO2 + 2 H2O

Although the concentration of methane in Earth's atmosphere is small (around 1.8 parts per million), it is an important greenhouse gas because it is such a potent heat absorber. The concentration of methane in our atmosphere has risen by about 150% since 1750, apparently largely due to human activities. Methane accounts for about 20% of the heating effects by all of the greenhouse gases combined. Both natural and human sources supply methane to Earth's atmosphere.

Major natural sources of methane include emissions from wetlands and oceans, and from the digestive processes of termites. Sources related to human activities include rice production, landfills, raising cattle and other ruminant animals (cow burps!), and energy generation.

Last modified February 8, 2006 by Randy Russell.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF