Articles | Volume 25, issue 18
https://doi.org/10.5194/acp-25-10661-2025
© Author(s) 2025. This work is distributed under the Creative Commons Attribution 4.0 License.
Sectoral contributions of high-emitting methane point sources from major US onshore oil and gas producing basins using airborne measurements from MethaneAIR
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- Final revised paper (published on 17 Sep 2025)
- Supplement to the final revised paper
- Preprint (discussion started on 17 Dec 2024)
- Supplement to the preprint
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Status: closed
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor
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RC1: 'Comment on egusphere-2024-3865', Anonymous Referee #1, 11 Feb 2025
- AC1: 'Reply on RC1', Jack Warren, 02 Apr 2025
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RC2: 'Comment on egusphere-2024-3865', Anonymous Referee #2, 12 Feb 2025
- AC2: 'Reply on RC2', Jack Warren, 02 Apr 2025
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AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload
AR by Jack Warren on behalf of the Authors (02 Apr 2025)
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ED: Referee Nomination & Report Request started (09 Apr 2025) by Steven Brown
RR by Anonymous Referee #2 (24 Apr 2025)
RR by Anonymous Referee #1 (28 Apr 2025)
ED: Publish subject to minor revisions (review by editor) (29 Apr 2025) by Steven Brown
AR by Jack Warren on behalf of the Authors (17 May 2025)
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ED: Publish as is (25 May 2025) by Steven Brown
AR by Jack Warren on behalf of the Authors (12 Jun 2025)
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This study describes the results from MethaneAir airborne campaigns across multiple basins in the U.S., with emphasis purely on attributed point sources above the MethaneAir detection limit. The study clearly presents the algorithms, the attribution, the results, and performs inter comparisons with other studies. I have a few comments that need to be addressed before I can recommend for publication.
1. Although this study represents (to the authors' knowledge) the largest airborne methane survey performed over onshore oil&gas in the U.S., it wasn't entirely clear what new learning was gained from such effort.
- (1a) One possibility is in their section on repeat sampling in Haynesville, where they show that point source frequency is possibly stable.
- (1b) Another possibility is that non-oil&gas point sources make up an equal fraction of emissions as oil&gas point sources. That is very interesting, but the authors need to address detection limit issues if that's the central thrust of the paper. For example, certainly there are a lot of oil&gas point sources not detected by MethaneAir that were there (hence the need to filter results for comparison with Cusworth et al., 2022). For other sectors, if the general distribution of emissions is higher than the MethaneAir detection limit (e.g., underground coal vents), then those would be readily detected while some oil&gas sources wouldn't be detected, hence over-inflating the non-OG contribution to point sources.
In any event, a presentation of this dataset itself is interesting, but some clarity on the general scientific questions this study is answering would be helpful to contextualize the results.
2. Line 85. A more recent MethaneAir paper cites 33-38 ppb for MethaneAir precision in the Permian Basin and Arizona. Why is there a discrepancy? Is 17-20 ppb consistent with what you calculated in this study? It would be nice to know the background standard deviation in each of the regions you surveyed as it contextualized the distributions of detections in this manuscript.
3. Lines 108-114. The DI and clumping technique you describe for plume detection uses many hard-coded values (e.g., 600-m pixel squares, 12 pixel clumps, etc.). Is this approach exactly the same as what was summarized in El Abbadi et al., 2024? In other words, how sensitive is the algorithm to these assumptions?
4. Related to comment #2 - by selecting 600m windows, you are making a prior assumption on plume size which then could bias your detection algorithm. Put another way, if you assumed 100-m windows (i.e., smaller plume sizes), would this result in more plume detections? Have you tested this?
5. Line 261-264. This is conjecture. I don't think that conclusion is defensible without citation or actual operational data.
6. Line 353 and elsewhere. You cite the detection limit for MethaneAir to be ~200 kg/h repeatedly throughout the text, but then restrict most inter comparison to emissions above 550 kg/h. Other studies name this specifically with a probability of detection or an effective detection limit. You've shown in this study that effectively the detection limit for methane air is 550 kg/h, so it would be more accurate to update every mention of ~200 kg/h to "200-550 kg/h."