A new study (embargoed) from Cornell in the journal Climate Change suggests natural gas emissions tracked over the lifecyle of a well *may* make coal a cleaner option than methane in the short and long run ...

Methane and the Greenhouse-Gas Footprint of Natural Gas from Shale Formations
Robert W. Howarth1*, Renee Santoro1, and Anthony Ingraffea2
1. Department of Ecology & Evolutionary Biology, Cornell University, Ithaca, NY 14853 USA. 1. School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853 USA.Abstract:

ABSTRACT: We evaluate the greenhouse gas footprint of natural gas obtained by high-volume
hydraulic fracturing from shale formations, focusing on methane emissions. Natural gas
is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas
production escapes to the atmosphere in venting and leaks over the life-time of a well.
These methane emissions are at least 30% more than and perhaps more than twice as
great as those from conventional gas. The higher emissions from shale gas occur at the
time wells are hydraulically fractured -- as methane escapes from flow-back return fluids
-- and during drill out following the fracturing. Methane is a powerful greenhouse gas,
with a global warming potential that is far greater than that of carbon dioxide, particularly
over the time horizon of the first few decades following emission. Methane contributes
substantially to the greenhouse gas footprint of shale gas on shorter time scales,
dominating it on a 20-year time horizon. The footprint for shale gas is greater than that
for conventional gas or oil when viewed on any time horizon, but particularly so over 20
years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps
more than twice as great on the 20-year horizon and is comparable when compared over
100 years.

Source:  http://thehill.com/blogs/e2-wire/677-e2-wire/155101-report-gas-from-fracking-...

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