Comment - Energy and Climate Change
US emissions down by David Flint.
You may have seen reports that US greenhouse gas (GHG) emissions fell 3.8% last year; they were all over the
media for a while. The fall since 2005 is said to be 12%. The main factor driving the fall is a switch from
coal to natural gas due, in turn, to the availability of cheap gas from fracking (shale gas) though the
recession has also contributed.
That's good news - but nothing like as good as it looks.
The emissions numbers count gas burnt but ignore gas lost during extraction and transfer to users
(Wall Street Journal 18/4/13)
Since natural gas is mainly methane and
methane is much worse for the climate
it takes only a little methane leakage to offset that saving in CO2 emissions.
To see how much we have to set a timescale and I choose 20 years because that is the critical period for
addressing climate change. If we have not solved it well within that period it will be a lost cause.
Because methane is such a potent greenhouse gas there will only be a saving of greenhouse gas emissions
relative to coal
if leakage is less than 0.7%. In 2011 Robert Howarth and co-workers at Cornell University estimated the leakage
in the US at 3.6% to 7.9%, exclusive of accidents. They conclude that switching from coal to shale gas will
increase the greenhouse effect of this fuel use by a factor of 1.2 to 2 over 20 years! The effect over 100
years is roughly zero.
Suppose that half of the apparent fall in greenhouse gas emissions was due to a switch from coal to shale gas
(which is plausible). Then the 12% reduction in CO2 would imply that the reduction in total greenhouse gas
emissions has been somewhere between 5% and nothing.
The switch from coal to shale gas is not a solution to the problem of climate change and has no part to play
unless the leakage can be very greatly reduced and the other environmental effects eliminated.
Nor is that the end of the bad news - unlike the policy-driven reductions we seek the US reduction is
price-driven and is therefore not locked in. Specifically:
Finally, low gas prices in the US have led the US to export the coal it would otherwise have burnt - mostly
- Part of the GHG reduction is due to the recession and will likely be reversed as the recession ends.
- Natural gas prices have been rising so US users have begun to switch back to coal.
Fossil fuels are a global market and local price falls will only increase fuel usage. We can only reduce
GHG emissions if we raise the price of fossil fuel.
Nasty but necessary.
First published in the EGP members newsletter, October 2013
Published and promoted
by Bill Linton for Enfield Green Party, both at 39A Fox Lane, London N13