Statistical Analysis and Modeling of the CO₂ Series Emitted by Thirty European Countries

Round 1

Reviewer 1 Report

I have gone through the manuscript entitled "Statistical analysis and modeling of the CO2 series emitted in the European Countries" and found promising to accepted as such. In my opinion, manuscript has high merit to publish. 

Author Response

Dear Reviewer,

Thank you for your appreciation.

Reviewer 2 Report

This is an interesting topic and within the scope of the journal. However, a critical issue is that the author did not propose the significance of the research well. What are the policy implications of these results? What kind of suggestions can we get from analyzing a large amount of data?

Overall, this draft has a good readability. The author needs to check the language to ensure the correct expression.

Author Response

Dear Reviewer,

Thank you for the valuable suggestions and time spent reviewing the article. Please find below, in Italics, the answers to your comments. 

This is an interesting topic and within the scope of the journal. However, a critical issue is that the author did not propose the significance of the research well. What are the policy implications of these results? What kind of suggestions can we get from analysing a large amount of data?

Thank you for the suggestions.

We added the significance of the research in the Introduction and mostly in the Results and Discussion. We also added comparisons with different approaches proposed by another reviewer.

The policy implications are presented in the context of the international documents related to climate change and the necessity of the reducing the CO2 emissions.

We also added comments on the benefit and difficulties of using large amount of data for such an analysis as ours.

Please see the part in red in the manuscript.

Comments on the Quality of English Language

Overall, this draft has a good readability. The author needs to check the language to ensure the correct expression.

We checked the manuscript for English and typos.

Reviewer 3 Report

See attached CO2_Europe.pdf

Comments for author File: Comments.pdf

Author Response

Please see the attached document.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript has been revised according to the comments.

Author Response

Thank you fro the appreciation.

Reviewer 3 Report

The reviewer noted improvements in the manuscripts. Several of his comments have been taken into account, but some problems remain. The author suggested that two time series (RegS and TempS) provided complete information on temporal and spatial changes in CO2 for thirty European countries. The reviewer recommended the use of three time series for RegS, which are derived from the cluster analysis in section 3.2.1. In the revised manuscript, the author still maintains that one series based on the cluster with the largest number of stations is sufficient to show the specificity of CO2 emissions across the entire sample of 30 stations. In fact, the author's calculations presented in Tables 5 and 6 confirm the use of three time series (one for Germany, second for ES+FR+IT+PL+NL (for MAPE_av_III case), and third for other the counties). For example, taking results for Poland  (PL), we have MAPE_c of 87.3 (Table 5) but only 10.63 for MAPE_c_III (Table 6). It means that cluster III is better representative for this station than cluster II. Obviously the "Germany" cluster is the worst representative of PL. The reviewer does not agree that the differences between the three regional series (Fig. 5) mean that Cluster III and the 'Germany' cluster are bad, as discussed in the revised manuscript (l.350-352). These three time series accurately show the structure of the temporal and spatial variability of CO2 for 30 stations. Furthermore, we can conclude that there are differences between the temporal variability of CO2 emissions in the clusters. In Germany, for example, a steady decline is observed between 1990 and 2021, but in Cluster III the decline started around 2008. What happens in Cluster II is difficult to see using the Y-axis scale in Figure 5.

The use of Temps is problematic. Figure 9 shows that Temps is the mean CO2 emission values calculated separately for 30 stations obtained by averaging the yearly means for the period 1998-2013. How can a trend be calculated from Temps, as stated in the abstract (l. 17-18). In its current form, Temps does not provide any additional information on CO2 variability for the whole sample. Figure 9 shows that there are stations with high, medium and low CO2 emissions when only data from 1998 to 2013 is considered. Such a pattern can be inferred earlier from Fig. 5. Therefore, section 3.2.2 can be excluded from the main text without losing information on CO2 variability for 30 stations. This means that any results relating to Temps should be removed from the manuscript. In fact, the current structure of the manuscript supports this suggestion, as the key Temps pattern (Fig. 9) is never discussed in the text.

The recommendation to the author is to improve the sections of the manuscript on RegS and Temps, i.e. to include the results for the three clusters as equally valid (section 3.2.1) and to delete section 3.2.2. The abstract and introduction should also be amended accordingly.

Author Response

Please see the attached document concerning the answers to your comments.

We followed your recommendations.

Author Response File: Author Response.pdf