Received yesterday on U.S. CO2 emissions lowest in 20 years: that's good and bad: natural gas is methane, after all. -jsq
Yet another comprehensive article. I might also add that one of the major down-falls (if not the most significant) of large-scale conversions to natural gas is the resources lifecycle methane emissions.
As your readers likely know, Methane is about twenty times as 'potent' a greenhouse gas as Carbon Dioxide. That is to say, it is far more efficient at trapping heat then Co2. So, less methane has a far greater impact on climate disruption then more Co2.
Natural Gas, from the point of combustion, releases about half the amount of Co2 released from burning coal, and about 30% of what's released in burning oil. To keep the benefits of reduced Co2 levels when switching from coal to natural gas, natural gas wells and transport lines must leak less then 2% of methane into the atmosphere. Recent research from Cornell is showing that Fracking wells are regularly releasing more then 4%, and often as much as 8% —far exceeding the 2% threshold— and thus making Natural Gas a far more dangerous resource for climate stability.
Tom Zeller Jr. wrote for the NYTimes 11 April 2011, Studies Say Natural Gas Has Its Own Problems