On one level this is a very nice systematic study of the GWP due to emissions of carbonyl fluoride. It is very clearly written and well presented.  To my knowledge, no other paper has presented a GWP for CF2O emissions, and so this part of the paper is clearly original and worthy of publication. The overall conclusion that the GWP is very low, is likely robust for all conditions.

Unfortunately, the paper has a significant flaw. It fails to connect with the previous literature and so confuses what is already known about CF2O with what is original in this paper.  In places it also presents information (e.g. on CH2O) that is not relevant to the paper and I believe it can be significantly shortened while retaining the key messages.

I recommend that the paper needs a major revision to clearly separate out what is already known about CF2O, the extent to which the new observations and calculations support/challenge what is already in the earlier literature, and what is truly original. The paper also lacks any uncertainty budget for the measurements and often presents values with an inappropriate level of precision.

Major comments

1. I am not an atmospheric chemist, but it did not take me long to search for and identify several papers on CF2O atmospheric chemistry that appear directly relevant to this work – these include https://doi.org/10.1021/acs.jpca.9b00899 https://doi.org/10.1007/BF00696901, https://doi.org/10.1016/j.cplett.2004.08.022 and https://doi.org/10.1021/j100033a023. Even the CF2O Wikipedia page presents a structure for the CF2O molecule which is very close to the structure presented here as if it is new science. Other databases such as Pubchem and NIST seem to contain well-established information on CF2O.
2. I do work in the area of radiative transfer. There is existing data of absorption cross-sections (see the supplementary data of Hodnebrog et al. (2020) (already referred to in the paper) and Thornhill et al. https://doi.org/10.1029/2024JD040912, for the source of this data). There is also line-by-line data for the major CF2O bands, readily available on the HITRAN database HITRANonline (it is Gas ID 29). It is essential that the new measurements in this paper are compared with this earlier work and any differences (and possible reasons for the differences) are discussed. The present paper even lacks a discussion of the integrated cross-section, leaving the reader to guess how the measurements compare with the previous literature. I believe this is also essential.
3. In addition, both Hodnebrog (in their supplementary information) and Thornhill already present the radiative efficiency for a constant CF2O profile (0.123 and 0.126 W/sq.m/ppb respectively) (although Thornhill’s reason for focusing on CF2O is not the same as in this paper). This needs to be acknowledged and some comparison of the new value – which is about 17% higher than these two studies – is necessary, with some possible explanations for this quite large difference.
4. There is a lack of discussion of uncertainties, for example on the absorption cross-section and radiative efficiency and, in my view, results are presented with an inappropriate level of precision (e.g., 4 decimal places in the case of RE). Generic estimates of uncertainties (and the source of uncertainties) for this class of gases are available in the two Hodnebrog Rev. Geophys. papers, and I assume similar generic estimates are available for reaction rates.

Other comments – those that start with * are particularly important.

18: “kinetic decay” – in atmospheric science it is more common to call this the e-folding lifetime

*32-34: This definition is incomplete – it is the time-integrated radiative forcing of a 1 kg pulse emission at time t=0 compared to the same mass emission of CO2

58-61: Very minor, but I am not sure this text is needed. The ACS is the prime property.

77: No explanation is given for the lower wavenumber (649 cm-1) lower limit. Presumably determined by the infrared detector?

*79: No source is given for these CO2 reference values and the specification of a single lifetime for CO2 is inappropriate for reasons explained in all the IPCC WG1 assessments. I recommend that the authors simply adopt and cite the IPCC AR6 AGWP(100) for CO2 which is in the supplementary information for https://doi.org/10.1017/9781009157896.009 at https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter07_SM.pdf

88: “potent” – do you mean in terms of radiative efficiency?

91: “emphasize the need” – this isn’t quite accurate. These protocols, amendments and agreements were posed in terms of CO2-equivalence (and hence why GWP-100 is widely used to provide that equivalence). They did not specifically focus on the need to reduce emissions of particular gases, but provided signatories with the option of doing so. It can also be noted that the Kigali Amendment to the Montreal Protocol https://ozone.unep.org/treaties/montreal-protocol/amendments/kigali-amendment-2016-amendment-montreal-protocol-agreed is perhaps also relevant, although not specifically relevant to the gases mentioned on line 85.

98: “moderately toxic” – all references that I looked at seem to say it is highly toxic. I am not in a position to judge.

110: The wavenumber range of the measurements needs to be stated. Presumably this is determined by the detector?

*157-163: Although quite interesting, no motivation is given for presenting these DFT calculations. Why are they needed, when you have measurements and, in terms of integrated cross-sections, how do they compare with the measurements? If it is to allow attribution of bands to specific modes of vibration, that is interesting, but I think this has already been established in the earlier literature – for example, see the papers that are referred to by the HITRAN database for CF2O. So, again, more references to the older literature are necessary and the text can be shortened so that it doesn’t appear as if the results presented here are original.

*168-181: Again, this section is presented without any references to earlier work, implying that this is new knowledge. As noted above, the molecular structure presented here is very little different to the CF2O entry on Wikipedia. I am not sure why the authors choose to compare with formaldehyde. This seems to lengthen the paper unnecessarily and can be removed.

Figure 2a: Although I believe Figure 2a is not necessary, note that the angles in the figure and in the caption are slightly different. There is also no need, in my view, to repeat information that is in the figure in the caption.

*Figures 2b and 3b: the authors need to revisit how that they handle the low wavenumber noise in the FTIR spectra. The fact that the noise sends the ACS negative is completely unphysical but it is not recommended that these are set to zero whilst retaining positive noise, as this introduces a bias. Many studies simply exclude regions between bands (i.e. set the ACS to zero) where the signal to noise ratio is too low.

184-189: Some of this discussion repeats information provided already in Section 2.

*190-204: Again results are presented without a single reference to previous work in this area. See my comment on 157-163 for where some of earlier papers can be found.

*183: This section needs to report the integrated absorption cross-section and to discuss uncertainties in the final value.

*217: Is 4 decimal places justified? How does this value compare with previous literature and what are possible reasons for the difference? And what is the estimated uncertainty in the IAC and RE.

*218: “measurable contribution to RF”. Without estimates or measurements of the abundance of C2FO it is not possible to make this statement, and I doubt if the RF can be measured as it is so small. The statement should either be better justified, or the authors should stick to RE, which is what they calculate and present.

*221-273: Again there is not a single reference to the older literature in the whole of this section, and so the impression is given that this is all new. I believe that the reactions given in Scheme 1 are already well established.

226: “negligible”. I am not sure what this means. Its presence is very clear in Figure 4a, but the reader is not told this.

*Table 2: Some values are quoted to 6 significant figures  (see also other tables in the paper) without any accompanying uncertainty estimate.

*225: More care is needed about such statements as “typical outdoor conditions”. While they may be correct for near-surface conditions where the measurements were made, they may not be appropriate elsewhere. Despite the short lifetimes found in this study, it may be possible for convection to transport some surface emitted C2FO to reach high altitudes and hence lower humidities.  Similarly, emissions in high latitudes may not experience such moist conditions. The authors could simply point out that these lifetimes are appropriate to the conditions in which measurements are made, but they may not be appropriate for all locations.  

*275: The reader should be reminded that these estimates of RE and GWP use the assumption that CF2O is well-mixed, which is highly unlikely given the short lifetime. Although not fully appropriate to the destruction processes for CF2O, the Hodnebrog papers present simple methods to adjust the RE (and hence GWP) for gas lifetime. Consequently, the values presented here are likely overestimates. In addition, it should  be noted that the GWP for very short lived species  is dependent on both the location and time of year of the emissions. A short statement on this may be useful.

299-291: This statement is not correct for the AGWP of CO2.

Supplementary Material: I feel that all the information concerning COH2 should be removed, as its relevance to this study is never established. It is also presented without any reference to the older literature which is extensive for this molecule.

I do wonder if this paper is more appropriate for AMT.  Regardless, there are some significant flaws that need to be addressed before this can be considered for publication.

1. It is unusual that the authors provide no discussion or even recognition of COF₂ present in the atmosphere as a degradation product of halogen species such as CFC-12 and HCFC-22.  There have been studies of this, e.g. https://doi.org/10.5194/acp-14-11915-2014.

Presumably this upper atmosphere COF2 contributes to the RE and GWP, but has not been considered.

2. I would like to see a rationale for why new measurements of COF₂ were needed, and why they are better than previous spectroscopic measurements.  There are spectroscopic data for this molecule in the HITRAN database in the form of line parameters.  There are existing cross sections in the literature, e.g. in the PNNL database.  Comparisons need to be made.

There is no uncertainty evaluation for the new COF₂ ACS.  What is the pathlength uncertainty?  How accurate is the COF₂ composition of the gas cylinder mixture?  What contribution does the dilution make to the error budget?  What about COF₂ adsorption on the walls of the sample cell?

3. What is the purpose of the DFT calculation of COF₂?  The comparison with the ACS is poor.  I don't understand the rationale here.  Unless this calculation is intrinsic to the RE/GWP calculations, I don't think its inclusion is warranted for an atmospheric journal.