Coal to gas: the influence of methane leakage |
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| Authors: | Tom M L Wigley |
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| Institution: | (1) National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80307-3000, USA;(2) University of Adelaide, Adelaide, South Australia, Australia |
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| Abstract: | Carbon dioxide (CO2) emissions from fossil fuel combustion may be reduced by using natural gas rather than coal to produce energy. Gas produces
approximately half the amount of CO2 per unit of primary energy compared with coal. Here we consider a scenario where a fraction of coal usage is replaced by
natural gas (i.e., methane, CH4) over a given time period, and where a percentage of the gas production is assumed to leak into the atmosphere. The additional
CH4 from leakage adds to the radiative forcing of the climate system, offsetting the reduction in CO2 forcing that accompanies the transition from coal to gas. We also consider the effects of: methane leakage from coal mining;
changes in radiative forcing due to changes in the emissions of sulfur dioxide and carbonaceous aerosols; and differences
in the efficiency of electricity production between coal- and gas-fired power generation. On balance, these factors more than
offset the reduction in warming due to reduced CO2 emissions. When gas replaces coal there is additional warming out to 2,050 with an assumed leakage rate of 0%, and out to
2,140 if the leakage rate is as high as 10%. The overall effects on global-mean temperature over the 21st century, however,
are small. |
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