Review Reports - Mortality Burden of Heatwaves in Sydney, Australia Is Exacerbated by the Urban Heat Island and Climate Change: Can Tree Cover Help Mitigate the Health Impacts?

Round 1

Reviewer 1 Report

Specific suggestions for revision are as follows:

1.Line79-89 The author describes the specific research content of this study in this part. But it doesn't say what scientific question did the study solve? In other words, what makes this work different from previous work? Because I find from the description of research method in this article that the author has carried out this research by referring to one person's working method for many times. So would the author please make it clear in the last part of the introduction?

2.Line91-108 Although the study area of this paper is a famous place. However, it does not make the reader clear about the specific location of the research area. Whether the location of the study area can be described in space. As with most studies, visualize the location and partition of the study area on a map.

3.Line224-242 Separate the results from the method description section. I might think you want to better illustrate the assessment of the correlation between vegetation cover and UHI. But in my opinion, line 224-235 is analyzing the results of this part. Would you please consider whether the content of this section is appropriate?

4. Can you beautify Picture 3?

5. Why didn't I see the conclusion of the study? In other words, I suggest you distinguish conclusions from discussions.

Author Response

Q1.Line79-89 The author describes the specific research content of this study in this part. But it doesn't say what scientific question did the study solve? In other words, what makes this work different from previous work? Because I find from the description of research method in this article that the author has carried out this research by referring to one person's working method for many times. So would the author please make it clear in the last part of the introduction?

A1. We appreciate this comment and agree that the introduction failed to make the study question clear. Please see the change to the final paragraph of the introduction, lines 78-83 now state:

“This study addresses current and future avoidable excessive heat exposures in Australia’s most populous city by comparing human health risks under various scenarios relating to climate change, urban heat and urban vegetation. Specifically, we statistically related temperature increases with attributable deaths using health impact assessment methods [22–24] and compared the mortality burden of heatwaves during the period 2006–2018 with that under a counterfactual scenario of no UHI-driven heat excesses.”

Q2.Line91-108 Although the study area of this paper is a famous place. However, it does not make the reader clear about the specific location of the research area. Whether the location of the study area can be described in space. As with most studies, visualize the location and partition of the study area on a map.

A2. We agree with the reviewer that the study area should be shown on a map. We have added a new Figure 1 which shows the study area and the partitioning of climate zones.

Q3.Line224-242 Separate the results from the method description section. I might think you want to better illustrate the assessment of the correlation between vegetation cover and UHI. But in my opinion, line 224-235 is analyzing the results of this part. Would you please consider whether the content of this section is appropriate?

A3. We apologise for the confusion relating to the correlation of vegetation cover and UHI. We address this using the findings from a previous study to firstly adjust land surface temperature (LST) measurements to better represent the air temperature excesses associated with the UHI. The confusion arises from the dominance of vegetation cover as a covariate in the correlation of LST with air temperatures. We now clarify this (for Reviewer 1 major comment) in lines 209-213 (see above).

Q4. Can you beautify Picture 3?

A4. Thanks for the suggestion, we have revised the figure (now re-labelled Figure 4) to improve it’s appearance.

Q5. Why didn't I see the conclusion of the study? In other words, I suggest you distinguish conclusions from discussions.

A5. To address this comment we have reworked the final paragraph of the discussion section to better conclude the article. See lines 399-406.

Reviewer 2 Report

review report (Atmosphere 2022)
Tittle: Mortality burden of heatwaves in Sydney Australia is exacer bated by the urban heat island and climate change: can tree 3
cover help mitigate the health impacts?

General:
In the paper under review, high resolution satellite observations of UHI air temperature excesses and green cover were jointly applied to address associated effects on heat related human mortality. It presents a result: tree canopy can reduce urban heat and more tree planting could mitigate increases in heat wave induced deaths with global warming. The story is interesting and welcome by many readers. Hence I suggest to accept to publish 。

Major comments:
I think that more detailed verification of relationship between LST and Tmax should be provided.

minor comments:
Line 164 and similars: RRik should be edited as RR_{ik}, in which _{ik} is subscript.

Author Response

Q1. Major comment: I think that more detailed verification of relationship between LST and Tmax should be provided.
A1. Thank you for this constructive comment. We have addressed it by adding the following sentence to lines 209–213:

“Maximum LST and maximum air temperatures (Tmax) differ in urbanised areas, primarily because in full sun many urban land surfaces, due to their physical, thermal and reflective properties, are heated more than the air. Herein, we made adjustments for the relationship between these measures according to vegetation cover as described below.”

Q2. minor comment: Line 164 and similars: RRik should be edited as RR_{ik}, in which _{ik} is subscript.

A2. We have made this correction.

Reviewer 3 Report

I was kindly asked to review the manuscript: Mortality burden of heatwaves in Sydney Australia is exacerbated by the urban heat island and climate change: can tree cover help mitigate the health impacts? Such study is highly relevant as it could add to the scientific body of knowledge and address a pressing public health issue, but I would encourage them to consider the following:

The abstract needs more of a ‘hook’ to engage the reader and establish the novelty of the analysis in the scientific literature. I recommend them to focus on the conclusions of the study.
The introduction section should be reorganized, provide additional information related to the methods followed in previous studies.
Methods:
- Please, provide a better description of the study area.
- Authors should describe the completeness of data. Do they have missing data?
- Could the authors provide more information on the control the validity of the results?

The discussion is disorganized, please split it into multiple small paragraphs each discussing a separate idea. There is plenty of ideas mixed in the same paragraph but very loosely linked.

Author Response

Q1 The abstract needs more of a ‘hook’ to engage the reader and establish the novelty of the analysis in the scientific literature. I recommend them to focus on the conclusions of the study.

A1 This is a very helpful comment that will improve the impact of our study. Hence, we have added the following text to the abstract: “numbers of heatwave days could increase 4-fold under the most extreme climate change scenario.”

Q2. The introduction section should be reorganized, provide additional information related to the methods followed in previous studies.

A2. We agree with the reviewer that the introduction was poorly organised. We have restructured the content and now refer to similar health impact assessment methods that were reported previously on lines 69-77.

Q3. Methods:

Q3.1 Please, provide a better description of the study area.

A3.1 We have improved the description of the study area by making explicit the distinctions between climate zones of the Sydney Greater Metropolitan Area. See lines 94-96: “Six regions (Sydney East, Sydney West, Gosford, Wyong, Newcastle and Wollongong: based on the classification defined in Khalaj et al. [25]) were distinguished from each other using a variance partitioning model for data from Sydney weather stations over the period 1998–2006 and are shown in Figure 1.”

Figure 1 is now a map of the study region to further improve the description.

Q3.2 Authors should describe the completeness of data. Do they have missing data?

A3.1 There were no missing exposure or outcome data in this study.

Q3.3 Could the authors provide more information on the control the validity of the results?

A3.3 We performed various sensitivity assessments to validate the results. With reference to heat attributable mortality, we made comparisons with results generated on the basis of 2-day rolling means of Tmax using a risk estimate derived by Wilson et al. (2013). We also performed assessments of the cooling effects of all vegetation, grass and shrubs only and tree cover only.

Q4. The discussion is disorganized, please split it into multiple small paragraphs each discussing a separate idea. There is plenty of ideas mixed in the same paragraph but very loosely linked.

A4. We thank the reviewer for this suggestion and agree that the structure of the original discussion was suboptimal. We have restructured for clarity and conciseness and coherence of ideas. We believe that the changes have significantly improved the manuscript.