Medium- and Long-Term Prediction of Airport Carbon Emissions under Uncertain Conditions Based on the LEAP Model

Round 1

Reviewer 1 Report

The subject of paper is a current for the global warming issues. However it needs major revision;

1- The abstract does not reflect to results. İt needs revision with adding a quantative results of study.

2- At the end of the introduction section, "in this paper.....", the originality of this paper and the differences from the literature should be stated. 

3- Furthermore, at the end of intro section, "the rest of the paper...." this paragragh can be removed.

4-In the result and discussion section, the discussions are not enough to understand the results. It should be discussed and compared with the results published in the literature. 

5- Uncertainty of the results needs to be discussed, especially in the context of the main findings. 

6- In addition to the main findings, the Conclusions section should indicate research gaps and research directions identified as the results of research presented. 

7- The policy recommendation should be dicussed with the existing policy.

Author Response

Dear Reviewer,

Thank you very much for your time involved in reviewing the manuscript and your very encouraging comments on the merits.

To facilitate this discussion, we first retype your comments in italic font and then present our responses to the comments.

Comment 1:

1- The abstract does not reflect to results. İt needs revision with adding a quantative results of study .

Response 1:

Thanks for your great suggestion on improving the accessibility of our manuscript. We have added quantitative results of carbon emission prediction in the abstract. (Page 1, Lines 20-23)

Comment 2:

2- At the end of the introduction section, "in this paper.....", the originality of this paper and the differences from the literature should be stated. 

Response 2:

Thanks for your suggestion. We have added quantitative results of study in the introducton. (Page 3, Lines 136-137)

Comment 3:

3- Furthermore, at the end of intro section, "the rest of the paper...." this paragragh can be removed .

Response 3:

Thanks for your suggestion. We have moved this paragraph.

Comment 4:

4-In the result and discussion section, the discussions are not enough to understand the results. It should be discussed and compared with the results published in the literature .

Response 4:

Thanks for your great suggestion on improving the accessibility of our manuscript.

In section 3.1, We have compared the results with Airports Council International's projections and added descriptions. (Page 16, Lines 449-451)

In section 3.2, to our best knowledge, there is no similar study has predicted the activity levels of these source. Since the activity levels of these emission sources are determined by airport throughput, we confirm the accuracy of airport throughput forecasts to ensure the accuracy of activity level forecasts.

In section 3.3, since there are few studies on the prediction of airport carbon emissions, we have chosen Hu's study on airports in China as a comparison and added relevant descriptions. (Page 18, Lines 522-528)

In section 3.4, we have compared the results of other studies and analyzed the reasons for the differences. (Page 19, Lines 545-554)

In section 3.5, as the existing studies have basically only considered aircraft as a source of emissions, and airlines bear most of the responsibility for aircraft emissions, there is no study to assign the abatement responsibility to other objects such as airports and air traffic management bureaus. Therefore, this study is the first to assign the responsibility of emission reduction to airport stakeholders. To show the innovation of our analysis, we highlight it in line 558.

Comment 5:

5- Uncertainty of the results needs to be discussed, especially in the context of the main findings .

Response 5:

Thanks for your great suggestion on improving the accessibility of our manuscript. We have increased the discussion on the carbon emission prediction results of three uncertain factors: social economy, epidemic development and emission reduction measures. (Page 18, Lines 505-521)

Comment 6:

6- In addition to the main findings, the Conclusions section should indicate research gaps and research directions identified as the results of research presented .

Response 6:

Thanks for your great suggestion on improving the accessibility of our manuscript. We have increased the research gaps and future research directions at the end of this study. (Page 22, Lines 619-634)

Comment 7:

7- The policy recommendation should be discussed with the existing policy .

Response 7:

Thanks for your suggestion. We have discussed it with the context of existing policies and measures. (Page 21, Lines 601-6004 and  Lines 607-609)

We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.

Sincerely,

The Authors

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript deals with a study devoted to prediction of airport carbon emissions based on LEAP model. Some key sources have been tracked and their controbutions is defined and predicted in the case-study of Guangzhou Bairyun International Airport (CAN). The results are interesting for science and technology community. The manuscript is well organized and described. Some Minor revisions are suggested:

1. Prediction data of LEAP model versus real measured data (2005-2020) of carbon emissions in the CAN airport should be provided to estimate the accuracy of model. Any comment on this ?

2. Minor editing and revisions are the correct numbering of sections. As an example, at page 12 "2.2.4 Scenario setting Module" is not coorect. Please, amend it.

After these Revisions, the manuscript should be publishable.

Minor editing of English is suggested before publication.

Author Response

Dear Reviewer,

Thank you very much for your time involved in reviewing the manuscript and your very encouraging comments on the merits.

To facilitate this discussion, we first retype your comments in italic font and then present our responses to the comments.

Comment 1:

Prediction data of LEAP model versus real measured data (2005-2020) of carbon emissions in the CAN airport should be provided to estimate the accuracy of model. Any comment on this?

Response 1:

Thank you for the detailed review. To the best of our knowledge, CAN has not carried out carbon emission accounting, so we cannot know the real historical data. Some authors have calculated the carbon emissions of airports of similar scale using the emissions and dispersion modeling system, which is an elaborate simulation model. After comparison, the carbon emissions calculated in this study are within a reasonable range. We have supplemented the relevant description in the main text. (Page 18, Lines 488-491)

Comment 2:

Minor editing and revisions are the correct numbering of sections. As an example, at page 12 "2.2.4 Scenario setting Module" is not correct. Please, amend it.

Response 2:

Thank you for the detailed review. We have carefully and thoroughly proofread the manuscript to correct all the numbering of sections.

We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.

Sincerely,

The Authors

Author Response File: Author Response.docx

Reviewer 3 Report

The main question addressed by the researcher is the medium and long term prediction of Airport Carbon Emission during landing and take off in China. The topic is relevant for the field of Aircraft industry and civil aviation authorities to control carbon emission during landing and take off and novel in terms of controlling these emissions. It adds substantial knowledge in the field of aircraft carbon emission and how to control it with comprehensive literature review and adopting the LEAP model methodology. Appropriate references and conclusion supported by results but needs to explain the simulation technique used during simulation.  

The manuscript is very well written and supported by literature and mathematical model based on LEAP with its solution through simulation. It is necessary to define the software used for the simulation.  

It require some minor grammatical corrections as "In first line of abstract is written "As important hubs......." which needs to be corrected and so on. 

Author Response

Dear Reviewer,

Thank you very much for your time involved in reviewing the manuscript and your very encouraging comments on the merits.

To facilitate this discussion, we first retype your comments in italic font and then present our responses to the comments.

Comment 1:

It is necessary to define the software used for the simulation. 

Response 1:

Thanks for your great suggestion on improving the accessibility of our manuscript.  We have added the definition of the leap model to the text. (Page 5, Lines 184-191)

Comment 2:

It require some minor grammatical corrections as "In first line of abstract is written "As important hubs......." which needs to be corrected and so on.

Response 2:

Thank you for the detailed review. We have carefully and thoroughly proofread the manuscript to correct all the grammar and typos.

We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.

Sincerely,

The Authors

Author Response File: Author Response.docx

Reviewer 4 Report

Please refer to the attached file

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you very much for your time involved in reviewing the manuscript and your very encouraging comments on the merits.

We have reviewed the full text, corrected grammar and formatting errors, and supplemented references to articles and formulas. We will now respond to the content-related suggestions for modification one by one. To facilitate this discussion, we first retype your comments in italic font and then present our responses to the comments.

Comment 1:

1. Page 1, Lines 13-14: Please explain more about ‘….due to a variety of uncertainties.’ Please give examples of variety of uncertainties mentioned.

Response 1:

Thank you for the detailed review. We have added examples of variety of uncertainties to the abstract. (Page 1, Lines 14-15)

Comment 4:

4. Page 1, Lines 19-20: Please elaborate clearly the means of ‘…all uncertain scenarios..’ mentioned.

Response 4:

Thanks for your great suggestion. We have supplemented the process of building uncertain scenarios, thus explaining the meaning of uncertain scenarios. (Page 1, Lines 15-16)

Comment 5:

5. Page 1: At the end of abstract, please highlight the significant of this study to related industries.

Response 5:

Thanks for your great suggestion. We have added the importance of this study for carbon peaking in the civil aviation industry. (Page 1, Lines 24-26)

Comment 7:

7. Page 1, Lines 33-38: ‘resulting carbon emissions …… goal will be tight, difficult and heavy.’ Please highlight the data regarding the current (or most recent) carbon emissions values and the corresponding increase from the previous period. Authors should present this information with data rather than simply mentioning carbon emission growth without referencing any data.

Response 7:

Thanks for your great suggestion.  We have added the airport's 2019 carbon emissions for reference. Since there is no carbon emission forecast study for the entire Chinese airports, we supplement the forecast results of Airports Council International on airport traffic volume. The development trend of traffic volume can reflect the development trend of carbon emission to a certain extent.

Comment 14:

14. Page 3, Lines 103-104: Please specify ‘…the third model…’ mentioned in the sentence. What the third model referred in this sentence.

Response 14:

Thank you for the detailed review. We have added an explanation of the third model corresponding to the above.  (Page 3, Lines 92-93)

Comment 19:

19. Page 3, Lines 110-122: At the end of this paragraph, please highlight the significant of this study to related industries.

Response 19:

Thanks for your great suggestion. We have added the importance of this study for carbon peaking in the civil aviation industry. (Page 3, Lines 134-137)

Comment 20:

20. Page 3, Lines 123-128: Suggest to remove this paragraph

Response 20:

Thanks for your great suggestion. We have moved this paragraph.

Comment 21:

21. Page 3, Lines 131-132: Unclear statement ‘…with many sources and complex composition.’ Please elaborate the mean of many sources and complex composition.

Response 21:

Thanks for your great suggestion. We have elaborated the mean of many sources and complex composition and given examples.  (Page 3, Lines 140-145)

Comment 24:

24. Page 3, Lines 134-135: ‘AE, APU, GSE and GAV’. Please take note, for the 1st time appear in this manuscript, authors should write full name followed by abbreviation/symbol in a bracket. Please check the whole manuscript and please do correction accordingly.

Response 24:

Thanks for your suggestion. On page 3, lines 126-128, we gave the abbreviations of the four emission sources' AE, APU, GSE and GAV ' in the introduction section. To make sure there are no such problems, we have checked the whole manuscript.

Comment 40:

40. Page 9, Line 298: Please add appropriate citation for this statement ‘…with importance degree >0.1’. Based on what? Referred to?

Response 40:

We agree with your opinion that there should be a basis for judging the degree of importance. We have added citations and rephrased the passage and hope that it is now clear. (Page 9, Lines 312-313)

Comment 41:

41. Page 10, Lines 300-301: Please add appropriate citation for this statement ‘…an importance level > 0.1’. Based on what? Referred to?

Response 41:

We agree with your opinion that there should be a basis for judging the degree of importance. We have added a literature reference to the analysis of passenger throughput in the previous sentence and clarified our presentation. (Page 9, Lines 312-313)

Comment 46:

46. Page 11, Lines 346-347: as shown in Table A.1 and A.2.??? Where is Table A.1 and Table A.2? Please check carefully and please do correction accordingly.

Response 46:

We apologize for not clearly stating these two tables in the appendix, we have moved original Table A.1 and A.2. from the appendix to the main text and hope that it is now clear. (Page 9, Lines 361-363)

Comment 54:

54. Pages 15-16, Lines 427-440 (Section 3.1): Please compare findings from this study to findings reported by previous researchers. Is it inline? Contradict? Better?. Please discuss critically.

Response 54:

Thanks for your great suggestion on improving the accessibility of our manuscript. We have compared the results with Airports Council International's projections and added descriptions. (Page 16, Lines 449-451)

Comment 55:

55. Pages 16-17, Lines 441-465 (Section 3.2): Please compare findings from this study to findings reported by previous researchers. Is it inline? Contradict? Better?. Please discuss critically.

Response 55:

Thanks for your great suggestion.  To our best knowledge, there is no similar study has predicted the activity levels of these source. Since the activity levels of these emission sources are determined by airport throughput, we confirm the accuracy of airport throughput forecasts to ensure the accuracy of activity level forecasts.

Comment 57:

57. Pages 17-18, Lines 466-480 (Section 3.3): Please compare findings from this study to findings reported by previous researchers. Is it inline? Contradict? B.etter?. Please discuss critically.

Response 57:

We agree with you that carbon emissions projections should be compared. Since there are few studies on the prediction of airport carbon emissions, we have chosen Hu's study on airports in China as a comparison and added relevant descriptions. (Page 18, Lines 522-528)

Comment 59:

59. Pages 18-19, Lines 482-496 (Section 3.4): Please compare findings from this study to findings reported by previous researchers. Is it inline? Contradict? Better?. Please discuss critically.

Response 59:

Thanks for your great suggestion.  We have compared the results of other studies and analyzed the reasons for the differences. (Page 19, Lines 545-554)

Comment 61:

61. Pages 19-20, Lines 497-517 (Section 3.5): Please compare findings from this study to findings reported by previous researchers. Is it inline? Contradict? Better?. Please discuss critically.

Response 61:

We agree with your suggestion. However, as the existing studies have basically only considered aircraft as a source of emissions, and airlines bear most of the responsibility for aircraft emissions, there is no study to assign the abatement responsibility to other objects such as airports and air traffic management bureaus. Therefore, this study is the first to assign the responsibility of emission reduction to airport stakeholders. To show the innovation of our analysis, we highlight it in line 558.

Comment 68:

68. At the end of this section, in 1 paragraph, please add the significant of findings from this study to the related industries and academician, followed by suggestion for future works.

Response 68:

Thanks for your great suggestion on improving the accessibility of our manuscript. We have supplemented the research value of this paper on carbon peaking in the civil aviation industry, and increased the shortcomings and future research directions of this study.

We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will find this revised version satisfactory.

Sincerely,

The Authors

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

All the comments were answered. It can be accepted.