Reply to “Reply to ‘Comment on “Hydrocarbon Emissions Characterization in the Colorado Front Range – A Pilot Study”’

Accepted for publication in Journal of Geophysical Research – Atmospheres via Council on Foreign Relations ‘Energy Climate and Security’ blog / by Michael A. Levi

[From the author’s blog] …Last fall, JGR published my critique of a highly publicized study (also published in JGR) from a team at NOAA. The study had claimed massive leakage rates for methane from natural gas production. Methane is a potent warming gas; the results, if correct, were a bombshell. My critique was simple: the original study had made unsupportable assumptions; if you removed those and instead used more of the data that the NOAA team had collected, you found implied methane leakage rates far lower than what the NOAA team had estimated…

A couple months after my critique appeared, JGR published a NOAA-team response. The response claimed to a find fatal flaw in my paper and doubled down on their original claim that their data revealed methane leakage well above accepted estimates. Because the NOAA response had been accepted so late, I wasn’t given an opportunity to defend my paper at the time. Soon after, a similar team of researchers announced preliminary (pre-review) results from another study, claiming even more massive methane leakage in Utah. These once again attracted considerable attention…

I quickly submitted a new note to JGR that made these points. It spent a couple months bouncing around in peer review because – and I find this kind of amazing – someone had found an additional flaw in the NOAA paper that I had not critiqued, and insisted that I needed to tackle it. My reply, including the additional requested critique (I swear I wasn’t trying to pick another fight), was finally accepted a few weeks ago.

The paper in press is here for JGR subscribers; you can download a preprint here. In it, I defend my paper from one NOAA-team criticism, but accept that their critique of the data set (“flashing profiles”) that they introduced and relied on may be correct. I then explained the consequences of that for both their analysis and mine. Here’s my bottom line from the newest paper:

“One can only conclude that either the flashing profiles are reasonably representative – in which case Petron et al [2012a] have presented no reason to question the results in Levi [2012] – or the flashing profiles are unrepresentative, in which case neither Petron et al. [2012] nor Levi [2012] have any basis to report reliable estimates of fugitive methane emissions. In either case, the results reported in Petron et al. [2012] are without foundation. Since the flashing profiles of condensate tanks in the area under study have likely changed since Petron et al. [2012] collected their data in 2008 (Petron et al [2012a]), this part of the debate is unlikely to be resolved definitively. Debate and observations should focus on rigorously understanding what is happening today through multiple observational and analytical methods. Several data collection efforts that could enable this are currently underway [EPA, 2012].”

I hope that we can do just that: focus on serious measurements that are underway while putting this flawed study behind us.


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