Review of “Global Emissions and Abundances of Chemically and Radiatively Important Trace Gases from the AGAGE Network”, by Luke M. Western et al.

General comments:

This manuscript provides the first systematic description of the methodology used by the AGAGE network to invert global emissions and mole fraction trends for 42 key trace gases based on a 12-box model, along with the release of a long-term updated dataset. This work fills a methodological transparency gap in the field of trace gas emission inversion and is of significant value for ozone layer assessments (WMO), climate change research (IPCC), and policy compliance (Montreal Protocol). The dataset is of high quality, with comprehensive compound coverage, and has been permanently archived through Zenodo (DOI: 10.5281/zenodo.15372480), aligning with the data-driven focus of the ESSD journal. Minor revisions are recommended before conditional acceptance, addressing the following specific issues.

First major comment:

Why didn’t the authors use MALTA, recently developed by Western et al. (2024), for the emission estimations in this paper? What are the differences in emission estimates for each compound between MALTA and the 12-box model? Does this mean that MALTA will not be used for this type of global emission estimation?

Second comment:

Do researchers still need to contact the principal investigators (PIs) of the measurement stations if they cite this paper to use the global mole fractions or emission estimates? Please clarify in the paper.

Third comment:

Each AGAGE baseline station is not located at the geometric center of its corresponding surface box in the 12-box model. This spatial mismatch could lead to representational errors, especially for species with regional emission gradients or temporal variability. How do the authors account for this spatial mismatch? And how does it affect the derived global mean mole fractions and the resulting emission estimates?

Specific comments:

• The document mentions the use of various instruments such as GC-MD, ADS, and Medusa GC-MS during different periods. However, the description of data continuity validation during instrument transitions (e.g., from ADS to Medusa) is insufficient. It is recommended to supplement the results of comparisons between different instruments during overlapping observation periods, quantify the range of deviations, and especially clarify the long-term consistency of methane observations between the GC-MD and CRDS systems (beyond the mentioned ratio of 1.0001±0007). Additionally, the impact of calibration scale conversion on historical data should be addressed.
• Section 7.1 mentions that “interannual repetition of meteorological data could lead to emission interannual variability errors,” but the impact of this issue has not been assessed. It is suggested to add a sensitivity test (e.g., comparing results using interannual varying meteorological fields) or cite Rigby et al. (2008) to quantify the uncertainty range.
• The transport parameters and loss processes (such as OH reactions and stratospheric losses) in the 12-box model are based on the latest literature (Burkholder and Hodnebrog, 2023), and the parameterization scheme is reasonable. The attention given to the prior emission independence in the Bayesian inversion framework (to avoid self-cycling of AGAGE data) is commendable. However, the prior assumption for some compounds (e.g., CFC-13, assumed to be 1/7 of CFC-115) lacks direct validation. It is recommended to include a sensitivity analysis to address this.

Technical corrections:

• The term “Semihemispheric” is inconsistently spelled (Section 5 vs. Section 4.1 “Semi-hemispheric”). The manuscript should standardize this term as “semihemispheric” following AGAGE conventions.
• Saunois et al. (2025) has been officially published (ESSD, 2025); citation information should be updated (volume, issue, pages).
• Line 43-44: For the sentence “g., ?Mühle et al., 2009”, it seems like there is an issue with the citation, as the question mark (?) is likely a placeholder or an error. It should be checked and corrected.
• Line 70-71: The original sentence “Oregon (45°N, 124°W°W)” contains an error with the extra “°W”.
• The hyphen used to connect years is inconsistent throughout the text; some instances use “–”while others use “-”. For example, in Line 195 and Line 199, it should be unified to “–” throughout the entire manuscript.

Conclusion

This manuscript provides a comprehensive and authoritative methodological framework for trace gas emission research, with high scientific rigor and valuable data. After addressing the recommended revisions to methodological details and improving the presentation of results, the work will significantly enhance the community’s understanding of halogenated greenhouse gases and ozone-depleting substances.

Western et al. provided a comprehensive description of the AGAGE measurements, and the 12-box model that have been traditionally used to derive observations-based global emissions for critical ozone depleting gases, their replacement gases, and major greenhouse gases.  The author team has done a great job in assembling the key information into a nice and comprehensive paper that steps from instrumentation, acquired observations, to emissions derivation. This paper is highly informative and, when published, will benefits the scientific community greatly.  I strongly support the paper to be published in ESSD, but I have a few comments which should be addressed before the paper is accepted for final publication.

1. Introduction section. While these listed gases (in Table 1) might be obvious to the authors and folks in the community why they are important and why measured, this isn’t necessary clear to the general readers outside the ODS community.  To many, it reads like a long list of chemical compounds, mostly synthetic. It would be very helpful if you can add a paragraph describe these gases in groups, if possible, add the connection between groups.  For example, major greenhouse gases, CFCs, HCFCs, HFCs, PFCs, and HFCs are ozone-friendly alternatives to CFCs and HCFCs, etc.  This way, it helps the readers to understand why they are the target gases measured by AGAGE.

2. Table 4. I would suggest the authors consider include an additional column of the tropospheric OH lifetime for all listed gases that derived with the 12-box model, in addition to the OHa and OHe/r values. This would be useful information in addition to the derived global emissions and can be compared with results from other published literature.

3. Section 4.2 A priori emissions. It is very nice to see the authors spend a tremendous amount of effort in gathering all possible bottom-up emissions and assemble into an a priori emissions inventory. I noticed that in the data availability section, only AGAGE-derived data sets are made available. I would strongly recommend that authors consider adding the a priori emissions into the data record as well, if possible.

4. Minor comments:

• Isn’t it more accurate to say “have been measuring” instead of “have measured”?
• L52-53. “AGAGE measurements are combined with the 12-box model and an inverse method to produce the derived products presented here”. This sentence is out of place. It should be moved to a later section. May be section 3?
• “have been used have been selected”? you only need one, either used or selected.
• Is it possible to include in the supplementary a list of other sites (that are not included in this paper) and the related details?  Some readers might find those information valuable, if in the future this becomes the AGAGE-goto paper?
• L112, L125 & L134. You should use southern and northern hemisphere consistently, either all start with upper cases or all with lower cases.
• L235 & L242. Consider change “a priori set of emission estimates” to “a priori emissions”.  It is a bit redundant as you also use an estimate of emissions right after this.
• L243-L244. I don’t think you need this sentence.  It is a bit hand-waving and unnecessary.  Just end with “available bottom-up estimates” in the previous sentence is adequate.