the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Apr 2023
The Emissions Model Intercomparison Project (Emissions-MIP): quantifying model sensitivity to emission characteristics
Hamza Ahsan
Hailong Wang
Jingbo Wu
Mingxuan Wu
Steven J. Smith
Susanne Bauer
Harrison Suchyta
Dirk Olivié
Gunnar Myhre
Hitoshi Matsui
Huisheng Bian
Jean-François Lamarque
Ken Carslaw
Larry Horowitz
Leighton Regayre
Mian Chin
Michael Schulz
Ragnhild Bieltvedt Skeie
Toshihiko Takemura
Vaishali Naik
Abstract. Anthropogenic emissions of aerosols and precursor compounds are known to significantly affect the energy balance of the Earth-atmosphere system, alter the formation of clouds and precipitation, and have substantial impact on human health and the environment. Global models are an essential tool for examining the impacts of these emissions. In this study, we examine the sensitivity of model results to the assumed height of SO2 injection, seasonality of SO2 and BC emissions, and the assumed fraction of SO2 emissions that is injected into the atmosphere as SO4 in 11 climate and chemistry models, including both chemical transport models and the atmospheric component of Earth system models. We find a large variation in atmospheric lifetime across models for SO2, SO4, and BC, with a particularly large relative variation for SO2, which indicates that fundamental aspects of atmospheric sulfur chemistry remain uncertain. Of the perturbations examined in this study, the assumed height of SO2 injection had the largest overall impacts, particularly on global mean net radiative flux (maximum difference of -0.35 W m-2), SO2 lifetime over northern hemisphere land (maximum difference of 0.8 days), surface SO2 concentration (up to 59 % decrease), and surface sulfate concentration (up to 23 % increase). Emitting SO2 at height consistently increased SO2 and SO4 column burdens and shortwave cooling, with varying magnitudes, but had inconsistent effects across models on the sign of the change in implied cloud forcing. The assumed SO4 emission fraction also had a significant impact on net radiative flux and surface sulfate concentration. Because these properties are not standardized across models this is a source of inter-model diversity typically neglected in model intercomparisons. These results imply a need to assure that anthropogenic emission injection height and SO4 emission fraction are accurately and consistently represented in global models.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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Supplement
(1130 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
hiddensource of inter-model variability and may be leading to bias in some climate model results.
Hamza Ahsan et al.
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-604, useful but some parts too short', Anonymous Referee #1, 16 Jun 2023
General comments
By applying 11 models the paper shows that calculated radiative forcing by tropospheric sulfate and black carbon aerosol is very sensitive to the altitude distribution of the emissions, and also in less extent, to the share of sulfate in the emissions and simplications in the models.
It should be published in ACP or maybe GMD after minor revisions.
Specific comments
Line 23: Define "BC" as "black carbon particles" where it occurs first.
Line 24 and later: Don't use "SO4" as abbreviation for sulfate without definition, at least not in the abstract. I suppose everywhere the particulate phase is meant and not gaseous H2SO4.
Table 1 and corresponding text in section 2.1: More information should be provided on "Endogenous oxidants, Endogenous DMS emissions". Which oxidants? For DMS effects on SO2 it matters if methylsulfonic acid as oxidation product is considered or not. Characteristics of the aerosol module important for the optical properties and hygroscopicity should be mentioned like e.g. interaction between BC and sulfate (aging, coating or external mixture), modal or sectional size distribution. This is important regarding the discussion in the conclusions.
Line 141ff: Refer to Table 2. From the discussion before it would have been better also to include emissions above 400m (discussed in conclusions).
Line 163: Gaseous? Sulfate precursor?
Figures 1 and S3: The selection of frames appears to be incomplete. In the supplement at least also the lifetime of sulfate for NH land should be provided.
Line 241f: This might be shortened because of a similar statement in line 215f.
Figure 2 and line 245ff: In the supplement should be a figure corresponding to panel a and b for Arctic BC lifetime which has to be mentioned in text.
Line 269: Here also the data of panel d of Figure 3 should be discussed since they are in the abstract and conclusions (refer at least to line 308ff, rearrange?).
Line 272: There appears to be a number missing (-1.06?) or the language is confusing. It would be also more convenient for the reader to provide the relating equation(s) of the forcing quantities (e.g. ERF=ARI+ACI) in section 3.2 for clarity. Is the comparison present to preindustrial only for sulfate plus BC? In the reference (Szopa et al., 2021) it includes also OC and maybe ammonia. Caution, there is an inconsistency between their Fig. 6.12 and the numbers in its caption. It is also somehow inconsistent with Fig. 7.5 (other time for present) but not Fig. 7.6 in Forster et al. (2021), which is in the reference list but not cited. The paragraph or the whole section 3.2 has to be revised regarding the relations between the quantities shown in Figure 3 and the ones in the IPCC-report.
Line 281: Is there a problem with too short spinup for GEOS?
Line 488 or later: Add something like "This implies also that emission inventories should contain emissions at different altitudes typical for the source categories (power, industry, road traffic, shipping...)".
Technical corrections
Table 1, column 3: Add "latitute x longitude" after "Resolution". Is the order for GISS consistent? "MATRIX" and the corresponding reference should be connected by a superscript or symbol.
Lines 223, 383, 421: Better skip "error" here.
Line 282: Cite Table 3 for the definition of the variables.
Line 361: Refer to Figure S1 for definition of regions.
Line 397: Refer to Figure 3c.
Line 707ff: Put the Forster reference to alphabetical order. The citation of the book is inconsistent with line 775ff.Citation: https://doi.org/10.5194/egusphere-2023-604-RC1 -
RC2: 'Comment on egusphere-2023-604', Anonymous Referee #2, 22 Jun 2023
In this study, the authors investigated the sensitivity of model outcomes to various factors, including the assumed height of SO2 injection, seasonality of SO2 and BC emissions, and the assumed fraction of SO2 emissions transformed into SO4 in 11 climate and chemistry models. The results revealed significant variations in the atmospheric lifetime of SO2, SO4, and BC across different models, underlining the importance of accurately accounting for anthropogenic emission injection height and SO4 emission fraction in global models. This paper is rightfully within the scope of ACP, however, I noticed several issues in this manuscript that cannot be passed over to be published. I suggested that the authors should consider the following comments.
General comments:
In Section 3.1 and 3.2, apart from showing results of reference scenario, authors also display perturbation results. These results have some similarities with the following contents in Section 3.3, 3.4 and 3.5. Therefore, I suggest reorganizing these results to enhance clarity and coherence. Effects of perturbations on BC are discussed in Section 3.4 and 3.5, but missed in Section 3.3, authors had better to add related results to make it comprehensive. The Conclusions section can be more concise to improve the readability.
Furthermore, it would be beneficial if the authors incorporated observations to evaluate the performance of different models under the reference scenario. Additionally, including figures depicting the global distribution of air pollutants would be valuable in illustrating the spatial patterns of SO2, SO4, and BC influenced by various emission characteristics. These additions would enhance the study's comprehensiveness and provide a visual representation of the findings.
Specific comments:
Section 2.3: This section can be combined into Introduction. There are too many repetitions with contents in Introduction.
Line 213: Are there any supporting materials for the method?
Line 216: What is DMS short for?
Line 259: Why did you investigate the perturbations on the radiative flux at the top of the atmosphere? You need to clarify whether it is upwelling or downwelling radiative flux.
Line 259-260: Why does a positive change denote a heating effect? You also have to clarify the heating effect on what.
Line 272: (2019-1750) here is ambiguous.
Figure 3: It is very difficult to understand the meaning of labels of y-axis.
Section 3.3: I suggest authors reorganize this section, because there are some repeated discussions, such as the impacts of emission height on SO2 and SO4.
Line 304-305: Can you explain why does SO2 emitted at height result in decreased SO2 deposition and an increase in oxidation to sulfate?
Citation: https://doi.org/10.5194/egusphere-2023-604-RC2 -
AC1: 'Author response to referee comments - egusphere-2023-604', Hamza Ahsan, 07 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-604/egusphere-2023-604-AC1-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-604, useful but some parts too short', Anonymous Referee #1, 16 Jun 2023
General comments
By applying 11 models the paper shows that calculated radiative forcing by tropospheric sulfate and black carbon aerosol is very sensitive to the altitude distribution of the emissions, and also in less extent, to the share of sulfate in the emissions and simplications in the models.
It should be published in ACP or maybe GMD after minor revisions.
Specific comments
Line 23: Define "BC" as "black carbon particles" where it occurs first.
Line 24 and later: Don't use "SO4" as abbreviation for sulfate without definition, at least not in the abstract. I suppose everywhere the particulate phase is meant and not gaseous H2SO4.
Table 1 and corresponding text in section 2.1: More information should be provided on "Endogenous oxidants, Endogenous DMS emissions". Which oxidants? For DMS effects on SO2 it matters if methylsulfonic acid as oxidation product is considered or not. Characteristics of the aerosol module important for the optical properties and hygroscopicity should be mentioned like e.g. interaction between BC and sulfate (aging, coating or external mixture), modal or sectional size distribution. This is important regarding the discussion in the conclusions.
Line 141ff: Refer to Table 2. From the discussion before it would have been better also to include emissions above 400m (discussed in conclusions).
Line 163: Gaseous? Sulfate precursor?
Figures 1 and S3: The selection of frames appears to be incomplete. In the supplement at least also the lifetime of sulfate for NH land should be provided.
Line 241f: This might be shortened because of a similar statement in line 215f.
Figure 2 and line 245ff: In the supplement should be a figure corresponding to panel a and b for Arctic BC lifetime which has to be mentioned in text.
Line 269: Here also the data of panel d of Figure 3 should be discussed since they are in the abstract and conclusions (refer at least to line 308ff, rearrange?).
Line 272: There appears to be a number missing (-1.06?) or the language is confusing. It would be also more convenient for the reader to provide the relating equation(s) of the forcing quantities (e.g. ERF=ARI+ACI) in section 3.2 for clarity. Is the comparison present to preindustrial only for sulfate plus BC? In the reference (Szopa et al., 2021) it includes also OC and maybe ammonia. Caution, there is an inconsistency between their Fig. 6.12 and the numbers in its caption. It is also somehow inconsistent with Fig. 7.5 (other time for present) but not Fig. 7.6 in Forster et al. (2021), which is in the reference list but not cited. The paragraph or the whole section 3.2 has to be revised regarding the relations between the quantities shown in Figure 3 and the ones in the IPCC-report.
Line 281: Is there a problem with too short spinup for GEOS?
Line 488 or later: Add something like "This implies also that emission inventories should contain emissions at different altitudes typical for the source categories (power, industry, road traffic, shipping...)".
Technical corrections
Table 1, column 3: Add "latitute x longitude" after "Resolution". Is the order for GISS consistent? "MATRIX" and the corresponding reference should be connected by a superscript or symbol.
Lines 223, 383, 421: Better skip "error" here.
Line 282: Cite Table 3 for the definition of the variables.
Line 361: Refer to Figure S1 for definition of regions.
Line 397: Refer to Figure 3c.
Line 707ff: Put the Forster reference to alphabetical order. The citation of the book is inconsistent with line 775ff.Citation: https://doi.org/10.5194/egusphere-2023-604-RC1 -
RC2: 'Comment on egusphere-2023-604', Anonymous Referee #2, 22 Jun 2023
In this study, the authors investigated the sensitivity of model outcomes to various factors, including the assumed height of SO2 injection, seasonality of SO2 and BC emissions, and the assumed fraction of SO2 emissions transformed into SO4 in 11 climate and chemistry models. The results revealed significant variations in the atmospheric lifetime of SO2, SO4, and BC across different models, underlining the importance of accurately accounting for anthropogenic emission injection height and SO4 emission fraction in global models. This paper is rightfully within the scope of ACP, however, I noticed several issues in this manuscript that cannot be passed over to be published. I suggested that the authors should consider the following comments.
General comments:
In Section 3.1 and 3.2, apart from showing results of reference scenario, authors also display perturbation results. These results have some similarities with the following contents in Section 3.3, 3.4 and 3.5. Therefore, I suggest reorganizing these results to enhance clarity and coherence. Effects of perturbations on BC are discussed in Section 3.4 and 3.5, but missed in Section 3.3, authors had better to add related results to make it comprehensive. The Conclusions section can be more concise to improve the readability.
Furthermore, it would be beneficial if the authors incorporated observations to evaluate the performance of different models under the reference scenario. Additionally, including figures depicting the global distribution of air pollutants would be valuable in illustrating the spatial patterns of SO2, SO4, and BC influenced by various emission characteristics. These additions would enhance the study's comprehensiveness and provide a visual representation of the findings.
Specific comments:
Section 2.3: This section can be combined into Introduction. There are too many repetitions with contents in Introduction.
Line 213: Are there any supporting materials for the method?
Line 216: What is DMS short for?
Line 259: Why did you investigate the perturbations on the radiative flux at the top of the atmosphere? You need to clarify whether it is upwelling or downwelling radiative flux.
Line 259-260: Why does a positive change denote a heating effect? You also have to clarify the heating effect on what.
Line 272: (2019-1750) here is ambiguous.
Figure 3: It is very difficult to understand the meaning of labels of y-axis.
Section 3.3: I suggest authors reorganize this section, because there are some repeated discussions, such as the impacts of emission height on SO2 and SO4.
Line 304-305: Can you explain why does SO2 emitted at height result in decreased SO2 deposition and an increase in oxidation to sulfate?
Citation: https://doi.org/10.5194/egusphere-2023-604-RC2 -
AC1: 'Author response to referee comments - egusphere-2023-604', Hamza Ahsan, 07 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-604/egusphere-2023-604-AC1-supplement.pdf
Peer review completion
Journal article(s) based on this preprint
hiddensource of inter-model variability and may be leading to bias in some climate model results.
Hamza Ahsan et al.
Data sets
CMIP6 historical anthropogenic emissions data Hamza Ahsan, Steven J. Smith https://doi.org/10.25584/DataHub/1769948
Emissions-MIP climate model results (ESMValTool) Hamza Ahsan, Harrison Suchyta, Steven J. Smith https://doi.org/10.5281/zenodo.7765075
Hamza Ahsan et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(961 KB) - Metadata XML
-
Supplement
(1130 KB) - BibTeX
- EndNote
- Final revised paper