Issues with Howarth paper

Open season has opened on Robert Howarth's paper claiming that shale gas emits more GHGs than burning coal; I like CFR's Michael Levi's take:
Howarth’s basic question is an important one: what happens to the claimed emissions benefits of natural gas once you include the methane leaked in its production and transport? Alas, his analysis is based on extremely weak data, and also has a severe methodological flaw (plus some other questionable decisions), all of which means that his bottom line conclusions shouldn’t carry weight. But someone else, with better data and more careful calculations, ought to address this important set of questions that he raises properly.
He cites four main issues; the first three are:
First, the data for leakage from well completions and pipelines, which is where he’s finding most of his methane leaks, is really bad.
Second, Howarth’s gas-to-coal comparisons are all done on a per energy unit basis... Here’s the thing: modern gas power generation technology is a lot more efficient than modern coal generation, so a gigajoule of gas produces a lot more electricity than a gigajoule of coal. The per kWh comparison is the correct one, but Howarth doesn’t do it. This is an unforgivable methodological flaw; correcting for it strongly tilts Howarth’s calculations back toward gas, even if you accept everything else he says.
Third, the problems with gas that Howarth flags have cheap technological fixes (green well completion techniques, better pipeline care), though there may be institutional barriers to implementing them. If we scale up gas and realize we have an emissions problem, there are things we can do. The only technological fix for coal, in contrast, is CCS, which isn’t commercial yet; if we decide we want to fix our coal problem, it’s not clear we have any options.
The fourth is around the time horizon used - a 20-year horizon makes methane look worse than a 100-year horizon, because it decays much faster than CO2. This one is really more of a judgment call than a serious flaw in the paper (at least it is transparent). But well said, Michael Levi - you've earned your RSS feed entry into my closely guarded Google Reader.

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