the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 Mar 2026
CAMS-REG-UNC-v8.1: A detailed uncertainty product for the gridded CAMS-REG-v8.1 emission inventory
Abstract. Independent verification of greenhouse gas emission reductions and trends in air pollution levels is receiving increasing attention. Atmospheric observations can provide such a constraint on emission estimates through inverse modelling, which requires a detailed quantification of uncertainties in prior emission inventories, observations and chemical transport models. This paper describes a detailed methodology to quantify uncertainties in a state-of-the-art European emission inventory: CAMS-REG. Uncertainties are estimated for all input data used to create the emission inventory and propagated to the final product. This results in separate uncertainty estimates for country-level emissions per sector and uncertainties in the spatial allocation of those emissions. Ideally, the gridded emission uncertainties should add up to the country-level emission uncertainties and for this purpose an optimization procedure was developed (only for countries with detailed emission reporting). This results in (scaled) gridded emission uncertainties and spatial error correlation lengths, which are included in the final dataset. The gridded uncertainty maps show large differences between pollutants and countries, representing the variability in input data and their reliability. CO2 shows the smallest gridded (optimized) uncertainties, with a median relative standard deviation of 15 % (interquartile range: 9 % – 25 %). The largest gridded (optimized) uncertainties are found for NMVOC: 45 % (38 % – 58 %). This work follows up from previous efforts and details the first comprehensive emission uncertainty dataset for Europe. The data are available from Zenodo: https://doi.org/10.5281/zenodo.18400810 (Super et al., 2026).
- Preprint
(1541 KB) - Metadata XML
-
Supplement
(28 KB) - BibTeX
- EndNote
Status: final response (author comments only)
- RC1: 'Comment on essd-2026-77', Anonymous Referee #1, 27 Apr 2026
-
RC2: 'Comment on essd-2026-77', Anonymous Referee #2, 12 May 2026
The manuscript is very well written, clear, concise, and interesting to read, and the resulting uncertainty estimates for gridded CAMS-REG emission inventories represent a useful and relevant product for the community.
I provide below a few general comments and suggestions that I hope will help further strengthen the manuscript.
General comments
- The manuscript would benefit from a clearer explanation of how the present work relates to preceding studies. Which assumptions are retained across versions, and which have been modified? A concise overview table or a dediacated section could be helpful in clarifying these differences.
- For users familiar with previous versions, a more direct one-to-one comparison would also be valuable. In particular, it would be interesting to understand how the estimated uncertainties are affected by the differences in the approaches between versions.
- The optimization approach plays a central role in "correcting" the prior gridded uncertainties. While I consider the approach itself to be sound and innovative, it may carry a risk of compensating, in some cases, for errors or biases in the prior gridded uncertainty data. It would be useful if the authors could reflect on this potential limitation in the discussion section.
Specific comments
- The authors might consider complementing the boxplots with violin plots. This would provide additional information on the shape of the distributions, including skewness or potential multimodality. This would be particularly interesting for Figure 4, where the boxplots for several sectors appear to be rather skewed.
- Table 3 is not fully clear and is not discussed in sufficient detail in the text. On first reading, I was confused because I assumed that the two columns referred to the same set of countries, and therefore wondered why the non-optimized CO2 values were higher than the optimized values, even though Figure 6 shows scaling factors mostly below 1. However, if I understand correctly, the two columns refer to distinct groups of countries. This should be clarified in the table caption and/or the main text.
- Figure 5: I find the logarithmic colour scale, especially for the relative uncertainties, somewhat difficult to read. Adding more tick labels could improve readability, for example at 0.2, 0.4, ....
Technical corrections
- add hyperlinks to references
- Line 358 typo: if -> is
Citation: https://doi.org/10.5194/essd-2026-77-RC2
Data sets
CAMS-REG-UNC-v8.1: A detailed uncertainty product for the gridded CAMS-REG-v8.1 emission inventory I. Super et al. https://doi.org/10.5281/zenodo.18400810
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 159 | 65 | 16 | 240 | 16 | 16 | 20 |
- HTML: 159
- PDF: 65
- XML: 16
- Total: 240
- Supplement: 16
- BibTeX: 16
- EndNote: 20
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
This paper presents a methodology to quantify uncertainties in the CAMS-REG European emission inventory, providing both country-level and gridded uncertainty estimates for greenhouse gases and air pollutants to support inverse modelling and emission verification.
The paper is interesting, well written, and cover a much needed aspect of emission inventories preparation.
However, I have some points I would like to see covered and improved before possible publication
- Table 1: why is this table only available for CO2 and CH4? Could you extend this to cover also air pollutants?
- Table 2: please better explain how these values are derived
- section 2.3. I re-read few times this section, but I have to say it's quite complex, and I would like to see this improved, for better clarity. I.e., could you describe the steps in a workflow/graph? There are some efforts in this direction (as Figure 2) but this section 2.3 should be improved, as it is the core of the paper, and at the moment is quite complex to follow
- similar to section 2.3, also section 2.4 should be improved, for better clarity
- Figure 2: also I found this Figure complex, and I cannot easily link it to the rest of the text...could you please improve its readability?
- Table 3 shows optimized and non-optimized uncertainties. To my knowledge, the optimized uncertainties values you get are quite low...are these values strongly affected by the uncertainties values you use as input, and if yes, did you implement a proper sensitivity analysis? Also, as these optimized values are quite small...are there other uncertainty source that should be considered and are not considered in your modelling, to fully define emission uncertainties? please specify
- Section 5 (data availability)... I checked the provided data...I think, to facilitate their use, on top of the usual CAMS-REG format for the data, one should provide a gridded uncertainty data (or at least a python code to convert the CAMS-REG format to a more simple gridded uncertainties field).