CC 2.0 Tim Evanson
As an ever-increasing number of countries consider
exploiting their shale gas resources, and researchers scramble to
understand what a production boom could mean for the climate, two
new pieces of research appear to come to opposite conclusions.
What is the climate impact of shale gas?
Since gas has about half
the emissions of coal when it's burned for electricity, it
has been touted as
a 'bridging fuel' for countries seeking to decarbonise
their economies to use as a stop gap on the way to a low carbon
But as we've
explored before, scientists are struggling to establish the
full impact of increased shale gas production on the climate, due
to methane that escapes during the extraction process - known as
fugitive methane emissions.
Two papers released this month examine what the actual climate
impact of natural gas is. At first glance they seem to show
opposite things. The graph on the left, taken from a paper by
Robert Howarth appears
to show natural gas electricity generation emissions - the towering
left bar - can be much higher than coal's. The second graph,
Heath et al, appears to show the opposite - that coal's
generation emissions (on the left) are much higher than those from
both conventional and shale gas.
Both papers examine the 'lifecycle emissions' of the fuels: the
amount of gas emitted from extraction to combustion. So why is
there such a large discrepancy between two papers?