Methane is one of the most potent greenhouse gases, second only to carbon dioxide in its ability to absorb thermal radiation. ... Data suggest that the United States may be responsible for half of global methane increase in the past decade.
Although we often focus on CO2 as the main greenhouse gas causing global warming, we should also be aware that the concentration of methane is rising because of man's activities. This is a particular concern since methane has a global warming potential about 80 times that of CO2 over a 20 year period. If even 4% of the methane produced is lost to the atmosphere, it will negate any advantages of replacing coal-fired power plants with natural gas plants.