Methane and Other Gases: A Range of Greenhouse Gases Contribute to Climate Change

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Methane, nitrous oxide and other greenhouse gases are more efficient at warming the atmosphere than carbon dioxide, but are present in much smaller quantities, and their overall contribution to global warming is less.

Methane is about 20 times more effective than carbon dioxide at trapping heat in the atmosphere. As its average atmospheric lifetime is 12 years, a reduction in emissions would have a rapid effect. Methane is produced by rice cultivation, coal mining, energy production and the rearing of livestock. In the industrial world, landfill sites are a major contributor. It's also produced in the natural environment, as bacteria break down organic material in anaerobic conditions.

Nitrous oxide is 300 times more effective than carbon dioxide at trapping heat in the atmosphere. The great majority of emissions are from agriculture--nitrogen-based fertilisers and livestock manure--with additional releases in waste, industrial processes and energy use.

Manufactured gases such as halocarbons--including chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs)--and compounds such as sulfur hexafluoride (S[F.sub.6]) have long lifetimes in the atmosphere. Sulfur hexafluoride is used as an insulator for circuit breakers and to stop oxidation of molten magnesium during processing. HFCs are used in refrigeration units, in place of CFCs.

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Reproduced from The Atlas of Climate Change by Kirstin Dow and Thomas E Downing (Earthscan 2007) copyright [c] Myriad Editions Limited / www.MyriadEditions.com

Methane hydrates

A vast amount of methane (an estimated 20 million trillion cubic metres worldwide) is trapped in permafrost ice and undersea sediments in a form known as methane hydrates or clathrates. …