Climate Warming at European Airports: Human Factors and Infrastructure Planning

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents a timely and well-structured analysis of projected thermal stress and temperature-related operational risks at European airports, with a particular emphasis on human factors and infrastructure planning. The topic is highly relevant to both the aviation and climate-impact communities, and the paper is generally well written, technically sound, and supported by an extensive and up-to-date literature base.

Recommendations for minor revisions:

1. The use of Humidex as the primary thermal comfort indicator is reasonable and clearly explained. However, given the aviation and occupational health focus of the paper, the justification could be strengthened by a more explicit comparison with alternatives such as WBGT or UTCI in the main text rather than relegated largely to the appendix. While data availability constraints are acknowledged, a clearer discussion of how this choice may bias or limit conclusions would improve transparency.
2. The reduction from 30 airports to a 9-site ensemble using k-means clustering is methodologically sound and clearly motivated but the implications of this dimensional reduction deserve further discussion. Namely, the extent to which major hubs versus secondary or regional airports are represented, and how sensitive the conclusions may be to the specific centroid selections, should be addressed, even briefly.
3. The manuscript would benefit from a short schematic or summary table linking each climate metric (Humidex, degree days, flash point exceedance, heatwaves) to specific operational or planning implications.
4. Some figures are information-dense. Minor adjustments like increasing font sizes and improving colour contrast would enhance readability.
5. A brief outlook on how these methods could be extended beyond Europe would broaden the paper’s appeal.

To conclude, the manuscript is scientifically sound and addresses an important gap at the intersection of climate change, human factors, and airport infrastructure. Addressing the minor revisions above would further strengthen its impact and clarity.

 

Author Response

Please see attached PDF.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study provides a significant examination of climate effects on European aviation, successfully converting CMIP6 meteorological data into practical metrics such as Humidex and degree days. But the use of Humidex for outdoor settings and the physical interpretation of fuel safety limits need a lot of work to make sure they are technically correct.

--Using Humidex makes it easier to do the math, but it makes it much harder to evaluate "Human Factors" for ground staff (like marshallers) who are directly exposed to sunlight. The authors need to talk about this limitation or explain why they didn't use established outdoor metrics like WBGT or UTCI because Humidex doesn't take into account radiative load and wind.

--The talk about the 38C flash point suggests that there is an immediate safety risk when the air temperature goes above this value4444. This doesn't take into account how stored fuel keeps its heat. The text needs to be changed to make it clear that this is a warning level for rules or operations, not a direct sign of the risk of bulk fuel ignition.

Figure 8(j) shows that Madrid has a clear bimodal temperature distribution under SSP5-8.55. Although mentioned in the text, there is no physical or meteorological rationale offered for this transition. To put this finding in context, there needs to be a short discussion of the underlying mechanism (for example, changes in circulation).

--There is a clear LaTeX compilation error in the standard error formula in the caption for Figure 8 that needs to be fixed.

--Figure 8 does not say how to choose the bandwidth for the Gaussian Kernel Density Estimates (KDE). Please include this in the methodology so that others can repeat it.

--Düsseldorf and Munich are both in the "Continental Influence" group. A short note saying that these places are often in Oceanic/Transition zones on standard Köppen maps would make climate science more accurate.

Comments on the Quality of English Language

This study provides a significant examination of climate effects on European aviation, successfully converting CMIP6 meteorological data into practical metrics such as Humidex and degree days. But the use of Humidex for outdoor settings and the physical interpretation of fuel safety limits need a lot of work to make sure they are technically correct.

--Using Humidex makes it easier to do the math, but it makes it much harder to evaluate "Human Factors" for ground staff (like marshallers) who are directly exposed to sunlight. The authors need to talk about this limitation or explain why they didn't use established outdoor metrics like WBGT or UTCI because Humidex doesn't take into account radiative load and wind.

--The talk about the 38C flash point suggests that there is an immediate safety risk when the air temperature goes above this value4444. This doesn't take into account how stored fuel keeps its heat. The text needs to be changed to make it clear that this is a warning level for rules or operations, not a direct sign of the risk of bulk fuel ignition.

Figure 8(j) shows that Madrid has a clear bimodal temperature distribution under SSP5-8.55. Although mentioned in the text, there is no physical or meteorological rationale offered for this transition. To put this finding in context, there needs to be a short discussion of the underlying mechanism (for example, changes in circulation).

--There is a clear LaTeX compilation error in the standard error formula in the caption for Figure 8 that needs to be fixed.

--Figure 8 does not say how to choose the bandwidth for the Gaussian Kernel Density Estimates (KDE). Please include this in the methodology so that others can repeat it.

--Düsseldorf and Munich are both in the "Continental Influence" group. A short note saying that these places are often in Oceanic/Transition zones on standard Köppen maps would make climate science more accurate.

Author Response

Please see attached PDF.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

No note, just no note. There are two metrics I have for acceptance, the first is the most common, I will cite it. The second, this is the first time it has been this good, that metric is, I learnt something, in this case a lot.

The framing is appropriate for Aerospace, and the contribution is incremental but valuable, particularly in how it integrates human factors, infrastructure planning, and climate metrics in an aviation-specific context rather than treating airports as generic urban assets.

There are no methodological flaws that would justify revision. The choices of Humidex, degree days, and percentile-based heatwave definitions are explicitly justified, limitations are acknowledged (e.g., wind, latent heat, economic quantification). The figures are clear, interpretable, and do real analytical work rather than serving as decorative outputs.

The only points I would characterise as optional, not required, are editorial in nature... (i) a brief signposting paragraph at the end of the Introduction clarifying the logical flow of the paper and in particular Sections 2–3 for non-climate specialists, and (ii) a short sentence in the Conclusions explicitly flagging airport operators and regulators as the primary audience.

Author Response

Please see attached PDF.

Author Response File: Author Response.pdf