Methane leaks could negate climate benefits of US natural gas boom: report

Suzanne Goldenberg, US environment correspondent, Tuesday 4 June 2013 16.38 BST


Reduction in carbon emissions triggered by America’s shift from coal to gas is being offset by a sharp rise in methane.


“Some 29% of America’s electricity came from natural gas last year – compared to just 14% a decade ago, the report said. But it comes at a high cost to the local environment, because of the risks to air and water quality posed by hydraulic fracturing.


There is also a growing body of evidence that the release of methane gas from well sites and pipelines is far higher than previously thought.


Methane is a far more powerful gas than carbon dioxide, even though it does not persist in the atmosphere for a shorter period.”



Sky:  Most media articles emphasize that methane does not persist very long in the atmosphere.  But what they don’t follow up with is the fact that methane breaks down in to components that contain CO2.  Please note the references and quotes below.  Although methane only persists in the troposphere around 8.5 years and in the atmosphere around 12 years, it is 20 to 25 times more effective as a greenhouse gas than CO2. CO2 persists between 100 and 500 years. As I have mentioned above, methane breaks down both in the troposphere and in the atmosphere into CO2 and water vapour; these are the two major greenhouse gases.  Unfortunately, the hydroxyl radical that facilitates the breakdown is depleted gradually.  As it depletes, then obviously, methane will gradually become more prominent as a greenhouse gas yet still breakdown into CO2 and water vapour.  This is what may be seen as a “double whammy” in the greenhouse effect on global warming. To be more precise one must include that although water vapour is a positive factor for warming, if it increases cloud cover, then the greenhouse gas effect is diminished because clouds serve as a reflective component and thus consist of a negative factor.


“There is a bit of hope in all of this information. An equal amount of methane as compared to an equal amount of CO2 has an effect on global warming of 20 times greater than CO2. Carbon Dioxide (CO2) will stay in our atmosphere for around 100 years. With a half life of 7 years Methane last around 10 years in our atmosphere. It is estimated that 60% of global methane emissions are related to human activities.  Some scientists believe that these green house gases are as significant as or greater than CO2 emissions from cars.”


The atmospheric concentration of methane is thought to have increased by a factor of 2.5 since

pre-industrial times, reaching 1745 ppb in 1998.1 This rate of increase far exceeds that of carbon

dioxide, concentrations of which are only 30% higher than in pre-industrial times. In fact,

information is sufficient for the IPCC to assert that the current methane concentration has not

been exceeded in the last 420,000 years.1



“The most effective sink of atmospheric methane is the hydroxyl radical in the troposphere, or the lowest portion of Earth’s atmosphere. As methane rises into the air, it reacts with the hydroxyl radical to create water vapor and carbon dioxide. The lifespan of methane in the atmosphere was estimated at 9.6 years as of 2001; however, increasing emissions of methane over time reduce the concentration of the hydroxyl radical in the atmosphere. With less OH˚ to react with, the lifespan of methane could also increase, resulting in greater concentrations of atmospheric methane.

Even if it is not destroyed in the troposphere, methane can usually only last 12 years before it is eventually destroyed in Earth’s next atmospheric layer: the stratosphere. Destruction in the stratosphere occurs the same way that it does in the troposphere: methane is oxidized to produce carbon dioxide and water vapor.”


“The duration period for carbon dioxide molecules in the atmosphere is somewhere between 100 and 500 years. Obviously, not all carbon dioxide molecules will stay in the atmosphere that long, but on average the duration may be around 200-300 years. Some scientists believe that it could be longer than that, others believe that the duration is shorter. Presently, there is some uncertainty in those figures.”