Emissions of methane in Europe inferred by total column measurements

Wunch, Debra; Jones, Dylan B. A.; Toon, Geoffrey C.; Deutscher, Nicholas M.; Hase, Frank; Notholt, Justus; Sussmann, Ralf; Warneke, Thorsten; Kuenen, Jeroen; Denier van der Gon, Hugo; Fisher, Jenny A.; Maasakkers, Joannes D.

doi:https://doi.org/10.5194/acp-19-3963-2019

Articles | Volume 19, issue 6

https://doi.org/10.5194/acp-19-3963-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-19-3963-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 6

Research article

|

28 Mar 2019

Research article |

| 28 Mar 2019

Emissions of methane in Europe inferred by total column measurements

Debra Wunch, Dylan B. A. Jones, Geoffrey C. Toon, Nicholas M. Deutscher, Frank Hase, Justus Notholt, Ralf Sussmann, Thorsten Warneke, Jeroen Kuenen, Hugo Denier van der Gon, Jenny A. Fisher, and Joannes D. Maasakkers

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Final revised paper (published on 28 Mar 2019)
Preprint (discussion started on 07 May 2018)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Assumptions need to be verified.', Anonymous Referee #1, 04 Jun 2018
RC2: 'Review of “Emissions of methane in Europe inferred by total column measurements”', Anonymous Referee #2, 23 Jul 2018
AC1: 'Response to referees', Debra Wunch, 01 Feb 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Debra Wunch on behalf of the Authors (01 Feb 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Feb 2019) by William Lahoz (deceased)

RR by Anonymous Referee #1 (15 Feb 2019)

Suggestions for revision or reasons for rejection

The authors considered my concerns from round 1 of review. Concern 1 (quantitative assessment of CO error propagation) is now covered in sufficient detail.

Concerns 2 (spatial and termporal correlation of CO and CH4 emissions) and 3 (representativeness of station-gradients for the region) are addressed by a modelling study for the year 2010. The outcome of the modeling as reported is surprising (to me). It appears sufficient to put 5 sun-viewing spectrometers (in a more or less uncoordinated way) across Europe to estimate annual area-wide CH4 emissions with an error of 2%. I.e. the errors coming from imperfect representativeness and imperfect correlation of sources are negligible. CO lifetime issues are not addressed by the modelling study but they are argued to be negligible.

On the monthly and seasonal scale, the modelling indicates that the emission estimates are far off the truth (Fig. 4). The phases of the CH4 emissions seasonal cycle are even opposite in the true model and in the estimates. Differences generally amount to 20%. The errors cancel when aggregating over the whole year.

I do not understand these opposing results for the yearly and the sub-yearly time-scales. Is the seemingly great performance for annual emission estimates fortuitous? Is the year 2010 representative? Does the model analysis actually show that the station-gradients are sensitive to/representative for European emissions? Would it be thinkable that, for a full year, they are sensitive to the global / hemispheric scale (e.g. through the general atmospheric growth rate) and it happens that (e.g. for this particular year) the „European growth rate“ is just the same as the global/hemispheric one?

The manuscript would benefit from some more detailed discussion along the above questions.

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RR by Anonymous Referee #2 (04 Mar 2019)

ED: Publish subject to minor revisions (review by editor) (06 Mar 2019) by William Lahoz (deceased)

AR by Debra Wunch on behalf of the Authors (15 Mar 2019) Author's response Manuscript

ED: Publish subject to technical corrections (17 Mar 2019) by William Lahoz (deceased)

AR by Debra Wunch on behalf of the Authors (18 Mar 2019) Manuscript

Short summary

We used five atmospheric observatories in Europe measuring total column dry-air mole fractions of methane and carbon monoxide to infer methane emissions in the area between the observatories. We find that the methane emissions are overestimated by the state-of-the-art inventories, and that this is likely due, at least in part, to the inventory disaggregation. We find that there is significant uncertainty in the carbon monoxide inventories that requires further investigation.