Natural gas is being hailed as a clean fuel and a bridge to a world where much less carbon is emitted to the atmosphere. It does burn cleaner than oil or coal (roughly 30% less carbon dioxide than oil and 50% than coal) and other pollutants are lower. But a problem is half as much as coal is still far too high - it may be fine for short term replacement for coal, but creating new infrastructure that uses it is a problem as power plants tend to last for five or more decades.
I said may be fine. It turns out there is a fly in the ointment. While burning natural gas is cleaner, not all of it is burned. Some escapes to the atmosphere. Natural gas is mostly methane which happens to be a much more powerful greenhouse gas than carbon dioxide. It varies with the type of coal burned, but if natural gas leakage is greater than about four percent the end result is greater green house gas emissions than coal.
Leakage exists, but it is poorly monitored. Estimates are in the two to three percent range for the US - meaning natural gas may be worse for global warming than burning oil. Some measurements have been very high - figures in the high single digits have been recorded at some fracking sites, but it should be stressed very little has been done in the form of actual measurements.
NPR recently profiled atmospheric scientist Ira Leifer who made a trek taking some measurements. Great stuff, but we need an instrumented infrastructure measuring this. My guess is there are industry and political pressures that would make the expense difficult. The next best thing would be solid amateur measurements - inexpensive instruments that could be easily calibrated would be a nice development. Then again a few percent waste is money that just blows away...
