Comment on “Hydrocarbon Emissions Characterization in the Colorado Front Range : a Pilot Study”

Journal of Geophysical Research-Atmospheres (in press) via the Council on Foreign Relations’ Michael Levi blog (full-text article — link to summarizing blog post is below)

In February 2012, the first and only paper to record actual methane emissions (not estimates based on surveys or modeling) over actual natural gas operations employing hydraulic fracturing recorded leakages of 2.3 – 7.7% of their gross annual production with an average loss of 4%.  In his commentary, Michael Levi describes how the mostly NOAA team miscalculated with “great data”.

[From blog post] The ongoing fight over whether shale gas operations are leaking dangerous amounts of methane – a question that many have called critical to determining whether shale gas is good or bad – has suffered from a paucity of data. That’s why a much talked about study, authored by thirty scientists (mostly from NOAA) and published in early February, made such big waves: it was the first (and remains the only) study to estimate shockingly high emissions based on actual observations in the field (data was collected in Colorado in 2008).

In a new paper in press at the Journal of Geophysical Research (preprint here), the same journal that published the NOAA results, I explain why the NOAA estimates are unsupportable. (Short version: great data; wrong interpretation.) I then exploit some data that the NOAA team reported but did not use in their calculations to re-estimate methane leakage rates. I find methane leakage rates that are most likely between 1 and 2 percent, very similar to what previous careful estimates have consistently indicated, but far lower than the rates — as high as 7.7 percent — that the NOAA study claimed.

I might try to explain the technical issues involved in the analysis in a future blog post. (Summary: The original paper relied on a critical but flawed assumption; my paper does away with it.) For now, though, I want to focus on the big picture. It’s summed up in the figure below, which is taken from my paper…

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