## 5 Conclusions
### Implications of This Study  
For climate change adaptation, a study area was selected with the ability to spatially implement concepts recommended by the IPCC and WHO. An empirical analysis of the actual cooling effects intended to lower LST was performed. Both UGSs and GBAM zones have been proposed as climate change adaptation methods by the IPCC and WHO. The IPCC described GBAM zones as a solar radiation modification technique that can cool urban areas on a regional scale; therefore, it provides the capacity to mitigate solar radiation in response to global warming. Techniques that affect temperature cooling on a regional scale are effective for cooling extreme high-temperature environments [7]. In this study, the cooling effect of GBAM zones on urban areas impacted by UHI was quantitatively examined with respect to LST. Therefore, this study yielded insights that can support the implementation of GBAM zones as proposed by the IPCC. Because of urbanization, the number of UGSs in cities is insufficient, although this method has been highlighted by the WHO as an important approach for climate change adaptation. Both the IPCC and WHO also recommend close monitoring and evaluation of the effects of such measures on actual urban areas; there is a critical need to reduce temperatures within cities. In the present study, the cooling effects of UGSs were examined under various temporal and spatial conditions. Strong cooling effects of UGSs were identified under various conditions. Therefore, this study provides useful physical information regarding the effective deployment of UGSs. Despite its useful research outcomes, this study had several limitations. First, only LST was used to determine HICS effectiveness. The various metrics for evaluating urban thermal environments include LST (\({}^{\circ}\)C), energy flux (W/m\({}^{2}\)), atmospheric temperature (\({}^{\circ}\)C), and physiological equivalent temperature, as well as the predicted mean vote, which reflects the sensory temperature experienced by humans [51; 5]. The measurement of UHIs considers both surface heat islands (based on LST) and atmospheric heat islands (based on atmospheric temperature) [52; 3]. The LST and atmospheric temperature have similar characteristics, but their reported correlations vary according to measurement time [53]. In contrast to the present study, previous work using physiological equivalent temperature and predicted mean vote (corresponding to sensory temperature) to determine the effect of GBAM zones on pedestrian comfort revealed a negative effect on thermal comfort among urban residents [54]. Therefore, even when the same technique is used in similar studies, results can be conflicting depending on the type of evaluation metrics used. To fully determine HICS effectiveness, future studies should evaluate them using suitable metrics for targets affected by the particular technique implemented. Conceptualization, Y.-IC. and M.-J.L. ; Data curation, Y.-IC. and D.Y. ; Methodology, Y.-IC. and M.-J.L. ; Resources, Y.-IC. and D.Y. ; Visualization, Y.-IC. ; Writing--original draft, Y.-IC. ; Writing--review and editing, M.-J.L. All authors have read and agreed to the published version of the manuscript. This paper is based on the findings of the research project Development of Optimization Techniques for Reducing Heat Wave Considering Urban Environment (2023-014(R)), which was conducted by the Korea Environment Institute (KEI). The study was supported by the grant (2020-MOIS35-001(RS-2020-ND629021)) from the Policy-linked Technology Development Program on Natural Disaster Prevention and Mitigation, funded by Ministry of Interior and Safety (MOIS, Korea). Not applicable. The authors would like to thank the anonymous reviewers for their very competent comments and helpful suggestions. The English in this document has been checked by at least two professional editors, both native speakers of English.