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A model of the methane moleculeA model of the methane moleculeMethane is a colourless, odourless, flammable gas. It is a compound with the chemical formula CH4 (one atom of carbon and four atoms of hydrogen). It is the main ingredient of natural gas, making up about about 87% by volume. Naturally-occurring methane is found both below ground and under the ocean floor, where the largest reservoir of methane is found. Both natural and human sources release methane into the Earth's atmosphere, where concentration levels, although tiny, are increasing.

Gases contributing to greenhouse gases, 1979–2008Gases contributing to greenhouse gases, 1979–2008

Greenhouse gas

Methane is a greenhouse gas: it traps part of the Sun's heat that is radiated back into space, warming the Earth's surface. Although the presence of methane in the atmosphere is minuscule (around 1.8 parts per million), it is a very effective absorber of heat, 25 times greater than carbon dioxide (CO2). Methane accounts for about 20% of the heating effects by all of the greenhouse gases combined.

Methane was first scientifically identified by the Italian physicist Alessandro Volta in the marshes of Lake Maggiore, on the border between Italy and Switzerland, in 1776. Volta was inspired to search for the gas after reading a description by Benjamin Franklin of mysterious "flammable air". Volta collected the gas rising from the marsh and demonstrated that it could be ignited with an electric spark.

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