Review Reports - Renewable Energy Consumption and Carbon Emissions—Testing Nonlinearity for Highly Carbon Emitting Countries

Round 1

Reviewer 1 Report

Although the paper seems to study a topic of interest for the readers of Sustainability, it has several drawbacks that make it, as currently presented, inadmissible for a journal publication:

* The abstract can be rewritten to be more meaningful should clarify what is exactly proposed (the technical contribution) and how the proposed approach is validated;

*Literature review techniques have to be strengthened by including the issues in the current system and how the author proposes to overcome the same.

*In the references in the Introduction section, the authors cite some works. However, they have not indicated the advantage or disadvantage and their relations to this paper. It's a little confusing.

*Quality of Figures is so important too. Please provide some high-resolution figures. The comparison of different methods using clear graphs should be explained.

* The way to present bibliographic references in Sustainability has a different presentation. Perform correction;

*Carry out a correction in lines 189 and 190 in term ?̂??=;

*Results need more explanations. Additional analysis is required in each experiment to show its main purpose. More extensive simulations and more figures are needed.

*The authors should add more details about the implementation of the code to perform the analysis and the library involved in this task.

* Discuss the future works concerning the research state of progress and its limitations.

Author Response

Compliance to Comments

Manuscript title: Renewable Energy Consumption and Carbon Emissions – Testing Nonlinearity for Highly Carbon Emitting Countries.

Authors acknowledge the reviewer’s valuable comments which have provided basis for the upgradation of the manuscript. Authors have tried best of their ability to incorporate the comments.

Reviewer 1

Although the paper seems to study a topic of interest for the readers of Sustainability, it has several drawbacks that make it, as currently presented, inadmissible for a journal publication:

* The abstract can be rewritten to be more meaningful should clarify what is exactly proposed (the technical contribution) and how the proposed approach is validated;

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The abstract has been updated based on the guidance provided all reviewers.

*Literature review techniques have to be strengthened by including the issues in the current system and how the author proposes to overcome the same.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The literature has been updated, several new discussions added in introduction and literature review.

*In the references in the Introduction section, the authors cite some works. However, they have not indicated the advantage or disadvantage and their relations to this paper. It's a little confusing.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The write-up has been revisited based on the guidelines provided in other comments

*Quality of Figures is so important too. Please provide some high-resolution figures. The comparison of different methods using clear graphs should be explained.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. High resolution pictures are added and their discussions in literature is updated

* The way to present bibliographic references in Sustainability has a different presentation. Perform correction;

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The template of sustainability has been used, the presentation of references have been corrected now there are easier to read.

*Carry out a correction in lines 189 and 190 in term ?̂??=;

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The equation has been removed as it is redundant based on guidelines provided by other reviewers

*Results need more explanations. Additional analysis is required in each experiment to show its main purpose. More extensive simulations and more figures are needed.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The interpretations are updated based on the change in variables and their discussions are updated with the connection to cleaner production

*The authors should add more details about the implementation of the code to perform the analysis and the library involved in this task.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The details of the statistical software utilized is added in the methods with references.

* Discuss the future works concerning the research state of progress and its limitations.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. Study limitations and future works are added at the end of the study.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript addresses the analysis of renewable energy and consumption and carbon emissions

Comments

In my opinion, the manuscript should be deeply revised before the final acceptance. Since the topic is important, but the goals are not achieved due to a very close and difficult to follow implementation. Therefore, the main issues to improve are:

1)The section empirical model is too confused. In Equations 1 to 4 the same ENV variable is defined with four possible equations? In line 129 ins mention figure 1b, and it should be 2b.

2) Equations 5 to 8 have the same using the same variable ENVit obtained from different expressions. How is it possible to sum so different variables?

3) The Procedural Outline is not easy to follow with no evident relation with the eqs. 11 to 14. All the sections need a deep explanation about to use the equations and the value of variables.

4) Table 1 appears with values and is not possible to understand from where they came and for which county is applicable. Moreover, table 2 and table 3 are not understandable. What is model 1 to 4 in table 3 ?

5) Table 4 and 5 have the same problem. The values are with no meaning and without information about which country they concern.

6) Figures 2 to 5 have no explanation or comments on the text.

7) Finally, the conclusions are in general quite a set of commonplace and without nothing new. There is no mention or advice about the path to each country.

Author Response

Compliance to Comments

Manuscript title: Renewable Energy Consumption and Carbon Emissions – Testing Nonlinearity for Highly Carbon Emitting Countries.

Authors acknowledge the reviewer’s valuable comments which have provided basis for the upgradation of the manuscript. Authors have tried best of their ability to incorporate the comments.

Reviewer 2

1)The section empirical model is too confused. In Equations 1 to 4 the same ENV variable is defined with four possible equations? In line 129 ins mention figure 1b, and it should be 2b.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The justification for same ENV variable in equation 1 to 4 is added and the figure numbers are corrected

2) Equations 5 to 8 have the same using the same variable ENVit obtained from different expressions. How is it possible to sum so different variables?

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. This study has instrumentalized the sustainable energy using for proxies, overall renewable energy and three sub forms of renewable energy in order to see how the transition towards green energy is related to CO2 emissions. Hence it led to development of four equations. Discussion added below figure 2

3) The Procedural Outline is not easy to follow with no evident relation with the eqs. 11 to 14. All the sections need a deep explanation about to use the equations and the value of variables.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The discussion of the equations are updated based on the guidelines provided by reviewers in section 4.3

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The discussion of table 1, 2 and 3 are added in terms of their source, and their interpretation criterions. The model 1 to 4 in table 3 are also elaborated as they correspond to equation 1 to 4.

5) Table 4 and 5 have the same problem. The values are with no meaning and without information about which country they concern.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. They are panel data statistics. The idea behind use of panel data is to firstly form generalizable theoretical base then assess the heterogeneities (country specific). They provide one value of the panel data, so it is not related to any country. Their interpretation criterion is added for table 4 and 5.

6) Figures 2 to 5 have no explanation or comments on the text.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The explanation of the figures are added at appropriate places with references

7) Finally, the conclusions are in general quite a set of commonplace and without nothing new. There is no mention or advice about the path to each country.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The conclusion is updated and country specific effects are discussed. In the results

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript presents essential issues of the influence of renewable energy consumption (Hydro, Solar and Wind) on carbon dioxide emission in ten most polluted countries over the period 1991-2018. Authors have investigated the nonlinear relationship between three sub-indices of the RES and CO₂ emissions (the second-degree polynomial function) by means of the panel ARDL-PMG approach. Additionally, some control variables have been incorporated into the model in order to explain the air pollution emission level in analysed countries, namely real GDP per capita, forest land area, non-resident and resident patent applications. All the empirical research leading to the identification of the nature and strength of the relationships between the renewable energy consumption, economic development, technological progress and carbon dioxide emissions are very important for establishing the targets of energy and environmental policies in particular countries, as well as they may be helpful in achievements the Sustainable Development Goals.

However, there are several issues which should be addressed and need to be more precisely described.

Abstract:

Decomposition of renewable energy sources into the "Wind, Solar and Hydropower" does not enable for the description of the non-linear relationship between the RES consumption and CO₂ emissions (lines 13-14). It should be explained what econometric methods has been used in this study. The variables used in empirical analysis should be precisely determined (see "forest" and "innovations" in lines 16-17).

Introduction:

The problem of low-emission transformation of economies, which has been outlined in the introduction, has been greatly simplified (e.g. line 80). Extremely important issues concerning the economic, environmental and technical conditions of the development of renewable energy sources in the analyzed countries have been omitted. Do the studied countries differ in terms of these determinants? What are the costs of building the new RES installations and what funds are used to finance such investments in individual countries? What is the structure of the RES in individual countries and what factors influence it?

Literature Review:

I suggest changing the way of referring to the literature - the current form of superscripts at the beginning of sentences makes it very difficult to read the manuscript. I suggest organizing and supplementing the literature review with information on the scope of the statistical sample (which countries were studied and in what period), the statistical and econometric methods, which will enable to show why the research results are inconsistent. The problem of interdependencies between energy consumption (conventional and green), economic growth and CO₂ emissions should be particularly carefully presented, as it is important from the point of view of the topic of the paper and its contribution to the existing literature. In particular, the aspects of modeling asymmetric and non-linear relationships among analyzed variables have been omitted in the literature review.

Empirical model:

I suggest joining the Section 3.1 Theoretical Background with part of the Section 3.2, that has been devoted to the econometric modeling.

Why is only the impact of RES on CO₂ emissions expressed in the form of a second-degree polynomial, while a linear relationship between economic growth and air pollution emissions is assumed? The extensive literature on the subject indicates the non-linear and asymmetric nature of this relationship.

Why has the empirical research not taken into account the consumption of energy from conventional sources, since this factor has an significant impact on CO₂ emissions? Moreover, the effect of reducing CO₂ emissions as a result of increasing RES consumption will be lasted and enable to achieve the Sustainable Development Goals, if it is accompanied by a decrease in the consumption of conventional energy.

FAS and INN variables should also be converted per capita so that the impact of technological innovation and afforestation on air pollutant emissions can be compared in countries that significantly differs from each other in terms of the area and population size.

I suggest replacing equations (1) - (4) by one general mathematical formula for which the description of the variables will indicate at different sub-indices of the renewable energy consumption used in modeling. The same remark applies to equations (5) - (8), (11) - (14), and (15) - (18). The more so because when copying the first equation, the Authors repeated the same errors in the writing of subsequent equations.

Eq. (5) - (8): why is the random component indexed only over time and not over time and objects (panel data)? I suggest adding to the parameters’ description β₁ – β₅ their expected signs, according to the assumptions made in the theoretical background section.

Sections 4.1 and 4.2: the description of panel unit root test and panel cointegration tests should be supplemented with the sets of hypotheses, explanation the symbols used in the equations (statistics and their distribution), discussion about the cross-section dependencies effect. Eq. (10) is incorrect.

Eq. (11) - (14): there is no subscript "i" in order to emphasize the spatial nature of the sample, what does the factor “ΔECG_t-j*ECG_t-j” mean? (lines 204, 209, 214, 219) Why in equations (12) - (14) the REC factor was introduced instead of the decomposed sub-index of renewable energy consumption? (lines 210, 215, 220)

Eq. (15) - (18): It is need to improve the indexation of variables and parameters, explain the meanings of “μ_it” and add the assumption about it. Why do all the variables are the same maximum lag?

Analysis and Discussion of Results:

Interpretations of all parameters in Section 5 should be supplemented with the assumption of ceteris paribus.

The assumption of white noise properties for the random component has not been verified (see line 68).

It is not clear what criteria were implemented for choosing the optimum lag in ARDL approach. Table 5: lack of residuals' diagnostic tests, that could indicate an appropriate specification of the short-run equation. Insignificance of the most of energy-related parameters also raises a question if the determined specifications are correct.

Moreover, it is worth commenting whether the threshold value for renewable energy consumption and its sub-indices is located inside analysed sample or not (see Figures 2-5). If not, it is possible to achieve this value in the near future?

Implication for cleaner production based development and conclusion:

Based on empirical results it is not clearly proved that solar (wind) energy consumption and CO₂ emissions are well described by the second-degree polynomial (see suggestions referring to the previous sections).

It is also difficult to agree with the statement that wind energy and hydroelectricity consumption will contribute to increasing CO₂ emissions in the future. Authors did not justify this conclusion with any arguments concerning, e.g. the technology of generating these kinds of energy.

The conclusion that "economic growth is harming the environment" (line 358) should be supported by more advanced empirical research, that will take into consideration asymmetric and nonlinear relationship between income and environmental degradation.

Recommendations for cleaner production and environmental policy should be based on in-depth analyses, which will also be related to environmental conditions and technological possibilities of wind, solar and hydroelectricity production in individual countries.

I recommend the professional verification of the language correctness of the text (e.g. line 142 “pane data”; lines 329-330; Table 3. “Padroni” or “Dicky-Fullet”), the careful correction of mathematical equations and descriptions to them.

Author Response

Compliance to Comments

Manuscript title: Renewable Energy Consumption and Carbon Emissions – Testing Nonlinearity for Highly Carbon Emitting Countries.

Authors acknowledge the reviewer’s valuable comments which have provided basis for the upgradation of the manuscript. Authors have tried best of their ability to incorporate the comments.

Reviewer 3

This manuscript presents essential issues of the influence of renewable energy consumption (Hydro, Solar and Wind) on carbon dioxide emission in ten most polluted countries over the period 1991-2018. Authors have investigated the nonlinear relationship between three sub-indices of the RES and CO emissions (the second-degree polynomial function) by means of the panel ARDL-PMG approach. Additionally, some control variables have been incorporated into the model in order to explain the air pollution emission level in analysed countries, namely real GDP per capita, forest land area, non-resident and resident patent applications. All the empirical research leading to the identification of the nature and strength of the relationships between the renewable energy consumption, economic development, technological progress and carbon dioxide emissions are very important for establishing the targets of energy and environmental policies in particular countries, as well as they may be helpful in achievements the Sustainable Development Goals.

However, there are several issues which should be addressed and need to be more precisely described.

Abstract:

Decomposition of renewable energy sources into the "Wind, Solar and Hydropower" does not enable for the description of the non-linear relationship between the RES consumption and CO emissions (lines 13- 14). It should be explained what econometric methods has been used in this study. The variables used in empirical analysis should be precisely determined (see "forest" and "innovations" in lines 16-17).

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The abstracted is improved based on guidelines and the corrections are done in the abstract at the mentioned places

Introduction:

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The references for the issues in transition toward renewable energy are added. Since it is a panel data model, it has started with generalizable base and then estimated the heterogeneous effects (country level) from the model.

Literature Review:

I suggest changing the way of referring to the literature - the current form of superscripts at the beginning of sentences makes it very difficult to read the manuscript. I suggest organizing and supplementing the literature review with information on the scope of the statistical sample (which countries were studied and in what period), the statistical and econometric methods, which will enable to show why the research results are inconsistent. The problem of interdependencies between energy consumption (conventional and green), economic growth and CO emissions should be particularly carefully presented, as it is important from the point of view of the topic of the paper and its contribution to the existing literature. In particular, the aspects of modeling asymmetric and non-linear relationships among analyzed variables have been omitted in the literature review.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The writing style of literature review has been updated. Since there is a dearth of studies which have explored the similar dimension, there are a few studies which can be used for comparison or refutation. These studies are discussed in the conclusion portion. Asymmetric effects and non linear effects are different dimensions of analysis. Since asymmetric effects are not in the scope of this study, hence they are not discussed. The asymmetric effects are commonly used then the IVs tend to increase and decrease more often. Since in our case we are aiming to increase renewable energy so the effect of reducing renewable energy intentionally is not complying to the theory to achieve sustainability.

Empirical model:

I suggest joining the Section 3.1 Theoretical Background with part of the Section 3.2, that has been devoted to the econometric modeling.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. Based on suggestions both sections have been updated and integrated to the aims of the study.

Why is only the impact of RES on CO emissions expressed in the form of a second-degree polynomial, while a linear relationship between economic growth and air pollution emissions is assumed? The extensive literature on the subject indicates the non-linear and asymmetric nature of this relationship.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. This study has assumed that the other variables are linear as the major source of economic growth to CO2 is the intensity of fossil energy. Since this study is used renewable energy as percent of total. So using polynomial will create problem of collinearity

Why has the empirical research not taken into account the consumption of energy from conventional sources, since this factor has an significant impact on CO emissions? Moreover, the effect of reducing CO emissions as a result of increasing RES consumption will be lasted and enable to achieve the Sustainable Development Goals, if it is accompanied by a decrease in the consumption of conventional energy.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. Since the data of renewable energy is in the form of proportion of total energy hence if it is increasing, then definitely the fossil energy is decreasing. So the outcome of the renewable energy is equal to the outcome of decreasing fossil energy.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The model has been re-estimated using the FAS and INN in per capita forms. The results, interpretations and implications are updated too. The effects of renewable energy are more resembling the theory. The changes are incorporated throughout the document.

I suggest replacing equations (1) - (4) by one general mathematical formula for which the description of the variables will indicate at different subindices of the renewable energy consumption used in modeling. The same remark applies to equations (5) - (8), (11) - (14), and (15) - (18). The more so because when copying the first equation, the Authors repeated the same errors in the writing of subsequent equations.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The equations are reduced and the discussion has been updated in the explanation related to the equations,

Eq. (5) - (8): why is the random component indexed only over time and not over time and objects (panel data)? I suggest adding to the parameters’ description β – β their expected signs, according to the assumptions made in the theoretical background section.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. Since it is PMG model which is used in the study, the short run will vary over time. The derivations are adjusted

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The hypothesis are added. The references of the original studies related to the test are added in citation for future references so equation 10 is not needed.

Eq. (11) - (14): there is no subscript "i" in order to emphasize the spatial nature of the sample, what does the factor “ΔECG *ECG ” mean? (lines 204, 209, 214, 219) Why in equations (12) - (14) the REC factor was introduced instead of the decomposed sub-index of renewable energy consumption? (lines 210, 215, 220)

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The subscript has been added with the variables in short run and the short run coefficients as per PMG model the typo *ECG has been removed in all equations. The equation 12 to 14 the REC is corrected with appropriate decomposed sub-index name of energy consumption.

Eq. (15) - (18): It is need to improve the indexation of variables and parameters, explain the meanings of “μ ” and add the assumption about it. Why do all the variables are the same maximum lag?

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The variables are updated as per suggestions, the parameter discussions are added. Since the sample is not long enough the PMG model is not converging with higher lags. This study has used smallest lag order possible to estimate the model. The post regression diagnostics also ensured that there is no need to add more lags to absorb any fluctuations.

Analysis and Discussion of Results:

Interpretations of all parameters in Section 5 should be supplemented with the assumption of ceteris paribus.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The term is added in all interpretations

The assumption of white noise properties for the random component has not been verified (see line 68).

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. That regression equation is the simple least square version, in order to validate the assumption, the panel ARDL model has been used whose diagnostics verified the assumptions.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The discussion of the optimal lag terms are added in the estimations. The discussion of the diagnostics is added

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. Since the new estimated model have changed the model coefficients, now other than the overall renewable energy consumption none of the energy source is changing signs across the sample as per the model. For the case of renewable energy the cutoff value is laying between the minimum and maximum value of the data.

Implication for cleaner production based development and conclusion:

Based on empirical results it is not clearly proved that solar (wind) energy consumption and CO emissions are well described by the second-degree polynomial (see suggestions referring to the previous sections).

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. Based on the suggestions by the reviewer the results have been changed, now the sign of second degree polynomial of solar and wind have changed to negative. However, we have added the potential justification for the positive effect of wind and solar energy on CO₂ are added in introduction. The major reason is the recyclability of the materials which are used in solar and wind energy equipment production.

It is also difficult to agree with the statement that wind energy and hydroelectricity consumption will contribute to increasing CO emissions in the future. Authors did not justify this conclusion with any arguments concerning, e.g. the technology of generating these kinds of energy.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The updated results do not state them. However, for the debate the reasons are mentioned in introduction. They come from use of materials and logistics

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The statement is based on the estimation results. Since it is the controlling factor not the primary focus of the study, hence its further investigation is suggested in future studies

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. Table for the current level of disaggregated energy consumption have been discussed in the study in table 2. Further these were related with the outcomes to provide country specific effects.

Response: Thank you very much for your valuable comments. Following is the summary response to the changes done in the document. The document has been proofread, the pointed corrections are done

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors made the requested changes.

Author Response

Thank you for your value able comments

Author Response File: Author Response.pdf

Reviewer 2 Report

I'm satisfied with the improvements made in the issues mentioned in comments to authors (1- 6) , however, the point 7) "Finally, the conclusions are in general quite a set of commonplace and without nothing new. There is no mention or advice about the path to each country" was not answered or the manuscript improved in that direction. The paragraph added by the authors is not enough.

Author Response

Thank you for your value able comments

Author Response File: Author Response.pdf

Reviewer 3 Report

I really appreciate the effort made by the authors to correct the paper. However, I have still found some inconclusive statements and mistakes that should be improved.

1) Introduction:

As the authors stated among study's objectives there was a formulating the proposition of a suitable policy, keeping in view the importance of renewable energy consumption in analysed countries (Introduction section). For this reason, the very general description should be supplemented with a short explanation of the economic, technological and environmental conditions for the development of the RES in the studied countries (similarities and differences).

2) Literature review and empirical model:

It is difficult to agree that "Asymmetric effects and non-linear effects are different dimensions of analysis".

What are the economic determinants for the production of renewable energy? Has the effect of reducing the RES consumption been observed in the analysed countries during the recession? Non-linear and asymmetric relationships between CO2, RES and GDP emissions are described in the literature, and this problem also applies to the subject of this paper. The authors should explain why they omitted the problem of nonlinear relationship between economic growth and CO2 emissions and RES.

The response “this study has assumed that the other variables are linear as the major source of economic growth to CO2 is the intensity of fossil energy. Since this study is used renewable energy as percent of total” does not address all issues of low-carbon economic transformation in these countries (e.g. renewable energy development costs, availability of external sources of financing for RES investments, especially during the recession phase).

3) Please explain the inconsistencies in the description of the variables:

“these energy indicators are presented in the form of % of total” (line 148) and “REC is the renewable energy consumption (Million tons per capita oil equivalent)” (lines 166-170). Mathematical formulas (5)-(8) and the second description of variables indicate that REC, WEC, SEC, HEC were modelled as level of energy consumption per capita, not the % of total energy consumption.

4) Analysis and Discussion of Results:

“As a 1% increase in renewable energy consumption increases carbon emission by 0.109%, whereas a 1% increase in a square of renewable energy consumption impedes carbon emanation by 0.0.82%, ceteris paribus” - this interpretation refers to the REC variable expressed in units of energy consumption per capita, and not the share of REC consumption in total energy consumption. This remark applies to all interpretations in the paper.

“if the selected countries increase their renewable energy consumption beyond 1.93% of total energy, their CO2 emissions will fall” - estimated threshold value is extremely low comparing to the energy and climate policy targets e.g. The Europe 2020 Strategy - "increasing the share of renewable energy sources (RES) in total energy consumption up to 20% in 2020”. It is needed in-depth discussion.

“Hydro energy consumption has a negative while the square of hydro energy consumption is insignificant” – such results pointed out the incorrect specification of the model, model should be re-estimated for only linear term of HEC.

"Here we can see that overall renewable energy (in figure 3) follows the negative portion of inverted U shape relationship, hydro energy (in figure 5) is showing an inverse relationship." -

-how should the negative values for CO2 emissions be interpreted in Figures 3-5?

- figure 5 shows a linear relationship between CO2 emissions and HEC consumption - the model specification with a square term of HEC is incorrect,

- in graphs 4 and 6, the threshold value for the consumption of WEC and SEC can be seen, previously the authors claimed that there was no such value (line 308).

"Table 2 shows that countries like Indonesia and Russia must adapt the Germany model of higher wind energy consumption. And South Korea must adapt hydro energy learning from the hydro energy consumption dominant countries" - please justify these conclusions with reference to the figures in Table 2 and environmental conditions in these countries.

5) Please read the manuscript carefully and update all conclusions to the new model estimation results - U shaped curve is not observed now (lines 19-20, lines 390-392; lines 420-432). It is not true that "solar or wind energy consumptions initially reduces carbon emissions but later increases it" (this is not consistent with the results in Table 5 and Figures 3-6).

Author Response

Thank you for your value able comments

Author Response File: Author Response.pdf