Natural Gas is routinely thought to be better than Coal in terms of emissions footprint. Burning natural gas primarily creates carbon dioxide and water vapor (though the precise natural gas combustion products is more complex than that). Carbon dioxide and water vapor seems pretty safe because those are things our bodies exhale on every breath. The carbon dioxide is a concern, as that is carbon which did not formerly exist in the ecosphere but had been sequestered millions of years ago. However recent research points to an unacknowledged problem with natural gas - leakage.
An Energy Collective article by David Lewis quotes Dr. Robert Howarth claiming that "gas has a greater climate impact than coal."
Dr. Howarth is quoted saying "I believe they are severely underestimating the methane leakage".
The work of Dr. Drew Shindell, a senior climate scientist at NASA G.I.S.S. who published new data on methane in October 2009. Paper in Science: http://www.sciencemag.org/content/326/5953/716.full and press release: http://www.giss.nasa.gov/research/news/20091029/
The work of Dr. Shindell's group was unable to be included in the IPCC’s AR4 because the discoveries were made after the May 2006 cutoff date.
"What happens is that as you put more methane into the atmosphere, it competes for oxidants such as hydroxyl with sulphur dioxide… More methane means less sulphate, which is reflective and thus has a cooling effect. Calculations of GWP [a way to calculate climate impact] including these gas-aerosol linkages thus substantially increase the value for methane." wrote Shindell in his article. Shindell says “although our calculations are more complete than previous studies”, he knows he hasn’t accounted for everything. But the nature of what's not known is data that increases the measurements.
Howarth's second point was that most severely underestimate leakage of natural gas. Recall that natural gas is methane, and that methane is a nasty very potent greenhouse gas.
http://www.youtube.com/watch?v=iW6Fw8bLIu0 - video showing methane leakage
Methane is easy to detect - get an IR camera.
It's said there is widespread ignoring of evidence of leakage. DOE ignores accidents, and that the DOE only studied plants the industry wanted them to study. Chemosphere 35: 1365-1390 "Direct Measurement of fugitive emissions of hydrocarbons from a refinery" Journal of the Air and Waste Management Association 58: 1047-1056
Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Natural Gas Industry. August 2009. Prepared by the URS Corp. for the American Petroleum Institute (API). API, Washington D.C.
"Substitution of natural gas for coal: Climatic effects of utility sector emissions." Climatic Change 54: 107-139
"The atmospheric cycling of radiomethane and the ‘fossil fraction’ of the methane source" Atmospheric Chem. & Physics 7: 2141-2149 (2007)
