On the Issues of NO_x as Greenhouse Gases: An Ongoing Discussion…

Round 1

Reviewer 1 Report

This article contains good ideas about discussing the effect of nitrogen oxides on the environment, and their role in the global greenhouse, I have no negative comments

Author Response

Thank you very much for your efforts to prepare the review of our paper. Thank you also that you recognize our paper as valuable work.

Reviewer 2 Report

Dear Authors

Topic of the paper good and presentation is also good but acceptance of the MS some correction are required (see attached file)

Comments for author File: Comments.pdf

Author Response

Thank you for your comments. We followed your comments provided in the attached files.  All your suggestions were taken into account and the manuscript was revised according to your comments. The section titles were revised and changed. The additional section “Methodology” was added. The abstract and conclusions were revised.

Reviewer 3 Report

Comments for Autors
1) Page 1, line 22, rename “Nomenclature” to Abbreviations and move it to the end of the article before References.
2) Page 3,5,6,7 and 10, / subsections 4.1., 4.2. and chapters 3, 4, and 5 are called the same - "NOx environmental impact"/ rename them according to their content,
3) Page 8, Table 1., is unnecessarily on 3 pages - edit it and correct the element indexes to: CO2, NO2, O3, CH4, SO2,
4) Page 11, line 370, correct or explain the sentence: [12][12][12][12][12]10b[12]Based on this assumption, the impact of 370 NOx on the GHE compared to CO2 can be described by the coefficient %GHGNOx (8).
5) Page 11, Table 2., is unnecessarily on 3 pages: edit it and correct the element indexes to: CO2, and the description of Table 2. in bold Table 2., (as directed by MDPI Applied Sciences),
6) Page 15, line 513, description of Table 3. in bold Table 3., (as directed by MDPI Applied Sciences),
7) Page 15, line 544, description of Table 4. in bold Table 4., (as directed by MDPI Applied Sciences),
8) Page 16, line 557, description of Table 5. in bold Table 5., (as directed by MDPI Applied Sciences),
9) Page 17, References, correct numbering and font style (as directed by MDPI Applied Sciences),
10) It would be more appropriate to maintain the structure of the article according to the requirements of MDPI Applied Sciences: 1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusions
11) In chapter 7.Conclusions, briefly add the science of your research, benefits, practical application, recommendations for practice and perspectives in the continuation of research or tests.

Author Response

Dear Reviewer,

Thank you very much for your great efforts to prepare the review of our paper. The specific response is presented below.

• Page 1, line 22, rename “Nomenclature” to Abbreviations and move it to the end of the article before References.

“Nomenclature” was moved to the end of the manuscript, according to your suggestion.

• Page 3,5,6,7 and 10, / subsections 4.1., 4.2. and chapters 3, 4, and 5 are called the same - "NOx environmental impact"/ rename them according to their content,

The titles of sections were revised. This mistake occurred during the final editing of the manuscript.

• Page 8, Table 1., is unnecessarily on 3 pages - edit it and correct the element indexes to CO2, NO2, O3, CH4, SO2,

The table was edited by the change of column width. In the final form, the length of the

• Page 11, line 370, correct or explain the sentence: [12][12][12][12][12]10b[12]Based on this assumption, the impact of 370 NOx on the GHE compared to CO2 can be described by the coefficient %GHGNOx (8).

This sentence was revised. The part “[12][12][12][12][12]10b[12]” came from the error of citation software.

• Page 11, Table 2., is unnecessarily on 3 pages: edit it and correct the element indexes to: CO2, and the description of Table 2. in bold Table 2., (as directed by MDPI Applied Sciences),

The table was edited according to your suggestions

• Page 15, line 513, description of Table 3. in bold Table 3., (as directed by MDPI Applied Sciences),

The description of Table 3 was revised.

• Page 15, line 544, description of Table 4. in bold Table 4., (as directed by MDPI Applied Sciences),

The description of Table 4 was revised.

• Page 16, line 557, description of Table 5. in bold Table 5., (as directed by MDPI Applied Sciences),

The description of Table 4 was revised.

• Page 17, References, correct numbering and font style (as directed by MDPI Applied Sciences),

The numbering and font style was corrected

10) It would be more appropriate to maintain the structure of the article according to the requirements of MDPI Applied Sciences: 1. Introduction

2. Materials and Methods
3. Results
4. Discussion
5. Conclusions

We would like to explain that our paper, as a review, has a specific structure. We would like to ask for your understanding of our point.

• In chapter 7. Conclusions, briefly add the science of your research, benefits, practical application, recommendations for practice, and perspectives in the continuation of research or tests.

We add the following sentence:

Our research has a beneficial value to the scientific community because our paper collects and clarifies opinions regarding the impact of NO_x on GHE. Thus, from a practical point of view, this paper can be useful for scientists as well as for policymakers.

Reviewer 4 Report

In this paper, Janusz Andrzej Lasek and Radosław Lajnert discussed NOx as a greenhouse gas and its impact. Generally, it is a very interesting paper. It is well-written with clear writing. I recommend this paper be published after several modifications. Below are my points:

Major points:

(1) The author discusses NOx as a greenhouse gas. The ideas are very new. Normally we think of carbon dioxide as a major greenhouse gas. What is the environmental impact of NOx, comparing the environmental impact of carbon dioxide? If the author can make a clear comparison, it will help the readers.

(2) In the discussion part, the author can give some suggestions to the policymakers, to help the policymakers to understand the situation and solve the problem. It will also provide a good impact on this paper.

Minor points:

(1) Line 94-95: The URL (www.canada.ca/en/environment-climate-change/services/environmental-indicators/progress-towards-canada-greenhouse-gas-emissions-reduction-target.html) is error 404 and I cannot find the page. Please check again carefully. 

(2) Line 194: Please check again on the "in units of Wm-2kg-1year" and make sure it is correct.

(3) Line 528. "These results were also presented (required values only) in Fig. 5." ... I cannot find Fig. 5 in the paper if I am correct.

(4) Line 544: Please check the number again in Table 4. Especially to the row of "Biomass/RDF (10%) co-firing".

(5) Line 591-594: "I (Janusz Lasek) give special thanks to my Wife with love and all my family for kindly support. I (Janusz Lasek) give special thanks to prof. Jeffrey Chi-Sheng Wu (National Taiwan University) who inspired me..." Normally, "Wife" should be "wife" and "prof. Jeffrey Chi-Sheng Wu" should be "Prof. Jeffrey Chi-Sheng Wu".

Author Response

Dear Reviewer,

Thank you very much for your great efforts to prepare the review of our paper. The specific response is presented below.

In this paper, Janusz Andrzej Lasek and Radosław Lajnert discussed NOx as a greenhouse gas and its impact. Generally, it is a very interesting paper. It is well-written with clear writing. I recommend this paper be published after several modifications. Below are my points:

Response: Thank you for your efforts to review our paper and you recognized it as a valuable work.

Major points:

• The author discusses NOx as a greenhouse gas. The ideas are very new. Normally we think of carbon dioxide as a major greenhouse gas. What is the environmental impact of NOx, comparing the environmental impact of carbon dioxide? If the author can make a clear comparison, it will help the readers.

As we tried explained, such impact of NOx on GHE is not unequivocal and it depends on the different conditions and different parameters such as the location of the NOx source, time, concentration of other compounds in the atmosphere (such as CO and CH4), and prevailing atmospheric conditions. Thus, the same level of NOx emissions might lead to different regional climate impacts. It sounds like magic but indeed, the double effect of NO_x on the global climate (positive and negative radiative forcing response) is possible, placing these compounds in warming or cooling gases, depending on conditions.

(2) In the discussion part, the author can give some suggestions to the policymakers, to help the policymakers to understand the situation and solve the problem. It will also provide a good impact on this paper.

Thank you very much for this comment. If the policy is considered and we take into account the impact of NO_x on GHE from stationary, surface sources, maybe it would be better to stay at the current “status quo”. Let us explain, why we are thinking about that. On the one side, some emissions of NO_x should be recorded in the emission policy, thus, the emitting units (e.g. power plants, industrial furnaces, etc.) should pay extra money for the equivalent of GHG emission. Nevertheless, from the opposite side, some units can prove that their emission has a negative effect (i.e. cooling) on GHE. Thus, they should try to count this emission as avoided emission that could decrease of real CO₂ emissions. Then, it could create a very complicated situation from a legislative point of view. As we present in the paper, the impact of NO_x from stationary sources on GHE is very low but the situation is different when we consider aircraft emissions. This impact can be huge in these cases. 

Minor points:

(1) Line 94-95: The URL (www.canada.ca/en/environment-climate-change/services/environmental-indicators/progress-towards-canada-greenhouse-gas-emissions-reduction-target.html) is error 404 and I cannot find the page. Please check again carefully. 

We remove these URL addresses and added the address https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:52018DC0773&from=EN.

(2) Line 194: Please check again on the "in units of Wm-2kg-1year" and make sure it is correct.

We check again this unit. It is consistent with the paper provided by Fuglestvedt and co-workers (Fuglestvedt, J.S., Shine, K.P., Berntsen, T., Cook, J., Lee, D.S., Stenke, A., Skeie, R.B., Velders, G.J.M., Waitz, I.A. Transport impacts on atmosphere and climate: Metrics. Atmospheric Environment, (2010) 44 4648-4677.)

• Line 528. "These results were also presented (required values only) in Fig. 5." ... I cannot find Fig. 5 in the paper if I am correct.

Thank you. It was corrected into “ in Fig. 4”.

(4) Line 544: Please check the number again in Table 4. Especially to the row of "Biomass/RDF (10%) co-firing".

We carefully revised Table 4 and put appropriate values.

(5) Line 591-594: "I (Janusz Lasek) give special thanks to my Wife with love and all my family for the kind support. I (Janusz Lasek) give special thanks to prof. Jeffrey Chi-Sheng Wu (National Taiwan University) who inspired me..." Normally, "Wife" should be "wife" and "prof. Jeffrey Chi-Sheng Wu" should be "Prof. Jeffrey Chi-Sheng Wu".

It was changed according to your suggestion. It was related to habits. In our country, for persons of special meaning, we use the title with a capital letter

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Paper is modified as per the suggestions of the the reviewers.now Ms is looking good and upto date. 

Reviewer 3 Report

I agree to publish the article in a modified form.