Methane and Carbon Dioxide Global Warming Potential

40 times.  Methane releases are 40 times more potent in terms of warming than CO2.  “As catastrophic as all this is, [Kevin Schaefer [kevin.schaefer@nsidc.org], a scientist at the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado] acknowledges his study underestimates what is likely to happen. The model does not measure methane releases, which are 40 times as potent in terms of warming as carbon.  Methane could have a big impact on temperatures in the short term, he says.  ‘There would be a lot of methane emissions. We're working on estimating those right now,’ he said.  The model also does not include emissions from the large region of underwater permafrost.  IPS previously reported that an estimated eight million tonnes of methane emissions are bubbling to the surface from the shallow East Siberian Arctic shelf every year.  If just one percent of the Arctic undersea methane (also called methane hydrates) reaches the atmosphere, it could quadruple the amount of methane currently in the atmosphere, Vladimir Romanovsky of the University of Alaska in Fairbanks previously told IPS.”  (Stephen Leahy, “Permafrost Melt Soon Irreversible Without Major Fossil Fuel Cuts,” IPS, Uxbridge, Canada, February 17, 2011 reporting findings in Kevin Schaefer, Tingjun Zhang, Lori Bruhwiler, Andrew P. Barrett, Amount and timing of permafrost carbon release in response to climate warming, Tellus B, 2011; DOI: 10.1111/j.1600-0889.2011.00527.x, article first published online on February 15, 2011)

30 times.  Number of times more potent methane is than CO2 in terms of heat-trapping potential. “Methane is a greenhouse gas more than 30 times more potent than carbon dioxide.”  How does methane compare to carbon dioxide?  (“Methane Releases From Arctic Shelf May Be Much Larger and Faster Than Anticipated,” Press Release 10-036, National Science Foundation, March 4, 2010)

25 times.  Methane GWP potency compared to carbon dioxide over a 100 year period.  “Methane is a relatively potent greenhouse gas. Compared with carbon dioxide, it has a high global warming potential of 72 (calculated over a period of 20 years) or 25 (for a time period of 100 years).  (Intergovernmental Panel on Climate Change - IPCC - "Climate Change 2007:  The Physical Science Basis - Summary for Policymakers," Fourth Assessment Report, Working Group 1, Chapter 2, IPCC Secretariat, Geneva, Switzerland, February 2007, p. 212)

23 times.  Methane has about 23 times the global warming potential of carbon dioxide when it is released into the atmosphere.  “Methane (CH4) . . . is the simplest hydrocarbon, and is the primary component of the natural gas that we burn for energy. Methane is also an important greenhouse gas, it has about 23 times the global warming potential of carbon dioxide when it is released into the atmosphere. There are many sources of methane. Some methane comes from human activities, for example, landfills, rice cultivation, and ruminant farm animals (like cows) are all large methane sources. Other large methane sources, like the ocean and wetlands, are natural.” (Monica Heintz, University of California, Santa Barbara, “Methane in the Ocean,” Ocean Explorer, ,” National Oceanic and Atmospheric Administration, Washington, DC, revised August 25, 2010)

20 Times.  Global warming potential of methane compared to carbon dioxide.    “In the ongoing debate over global warming, climatologists usually peg carbon dioxide as the most dangerous of the atmosphere's heat- trapping gases. But methane, a greenhouse gas 20 times more potent than carbon dioxide, might be even more problematic. According to Tessa Hill, a geologist at the University of California, Davis, more methane is released into the atmosphere from ocean deposits during periods of warming than previously thought.  This expelled methane increases temperatures and releases more methane, creating a positive feedback loop.” (Elizabeth Svoboda, “Global Warming Feedback Loop Caused by Methane, Scientists Say,” National Geographic News, August 29, 2006 reporting findings in Tessa M. Hill - tmhill@ucdavis.edu, J. P. Kennett, D. L. Valentine, Z. Yang, C. M. Reddy, R. K. Nelson, R. J. Behl, C. Robert, and L. Beaufort, “Climatically driven emissions of hydrocarbons from marine sediments during deglaciation,” published online before print August 30, 2006, doi: 10.1073/pnas.0601304103 and published in print Proceedings of the National Academy of Sciences PNAS vol. 103 no. 37 13570-13574, September 12, 2006, pp. 13570–13574)

Video of Kirk R. Smith making the above PowerPoint presentation, Carbon on Steroids: The Untold Story of Methane, Climate, and Health, California Air Resources Board, Sacramento, California, November 10, 2008.  How does methane compare to carbon dioxide?