20,555
edits
Changes
Jump to navigation
Jump to search
SW: add section
'''Methane''' (CH<sub>4</sub>) is a potent greenhouse gas with a high global warming potential 72 times that of carbon dioxide (averaged over 20 years) or 25 times that of carbon dioxide (averaged over 100 years), according to the [[Intergovernmental Panel on Climate Change]] (IPCC)'s Third Assessment Report. Methane in the atmosphere is eventually oxidized, producing [[carbon dioxide]] and water. This breakdown accounts for the decline in the global warming potential of methane over longer periods of time.<ref>Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)[http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html "Climate Change 2007: Working Group I: The Physical Science Basis: 2.10.2 Direct Global Warming Potentials"], ''IPCC Fourth Assessment Report: Climate Change 2007'', Cambridge University Press, 2007.</ref>
The [[global warming]] potential of methane was estimated at 21 times that of carbon dioxide, averaged over 100 years, in the IPCC Second Assessment Report, and the 21 figure is currently used for regulatory purposes in the United States.<ref>[http://epa.gov/methane/scientific.html "Methane,"] U.S. Environmental Protection Agency information page, accessed July 2010</ref> Critics note that, when compared based on immediate effects, any methane released today is at least 56 times more heat-trapping than a molecule of carbon dioxide.<ref>Jason Mark, [http://www.earthisland.org/journal/index.php/elist/eListRead/methanes_contribution_to_global_warming_is_worse_than_you_thought/ "Methane’s Contribution to Global Warming is Worse than You Thought,"] Earth Island Journal, August 20, 2012.</ref>
Methane is both a [[greenhouse gas]] and a contributor to background levels of [[ozone]]. Tropospheric ozone is a significant greenhouse gas and the primary constituent of photochemical [[smog]].<ref>[http://www.oar.noaa.gov/spotlite/2006/spot_methane.html "Linking climate and air pollution: Methane emission controls yield a double dividend"] NOAA, accessed November 2010.</ref>
