Abstract
Increasing urban tree cover is a common strategy to lower urban temperatures and indirectly the building energy demand for air-conditioning (AC). However, urban vegetation leads to increasing humidity with potential negative effects on the AC dehumidification loads in hot-humid climates, an effect that has so far been unexplored. Here, we included a building energy model into the urban ecohydrological model Urban Tethys-Chloris (UT&C-BEM) to quantify the AC energy reduction effects of trees in seven hot cities with varying background humidity. A numerical experiment was performed simulating various urban densities and tree cover scenarios in the city-climates of Riyadh, Phoenix, Dubai, New Delhi, Singapore, Lagos, and Tokyo. The relative contribution of tree shade, air temperature reduction, and humidity increase on the AC energy reduction was further quantified. We found that well-watered trees provide the largest average summer AC energy reduction of −17% in the hot-dry climate (Riyadh, Phoenix). As tree shade is the dominant factor leading to the AC energy reduction in all city-climates, humid cities also show an average summer AC energy reduction ranging from −6% to −9%. However, increasing humidity is affecting AC dehumidification loads, especially under higher ventilation rates in humid climates and in these cities, AC energy reduction is most efficient with up to 40% tree cover. Additionally, we found that trees effectively reduce peak AC energy consumption due to higher shading effects in those hours. These results can inform urban planning strategies to maximize reduction in the AC energy demand using urban trees. © 2025 The Author(s).
| Original language | English |
|---|---|
| Article number | e2024MS004590 |
| Journal | Journal of Advances in Modeling Earth Systems |
| Volume | 17 |
| Issue number | 3 |
| Online published | 5 Mar 2025 |
| DOIs | |
| Publication status | Published - Mar 2025 |
Funding
This research was conducted at the Future Cities Lab Global at Singapore‐ETH Centre. Future Cities Lab Global is supported and funded by the National Research Foundation, Prime Minister's Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme and ETH Zurich (ETHZ), with additional contributions from the National University of Singapore (NUS), Nanyang Technological University (NTU),Singapore and the Singapore University of Technology and Design (SUTD). GM acknowledges support from the SNSF Weave/Lead Agency funding scheme(Grant 213995). YT acknowledges support from the Environment Research and Technology Development Fund (GrantJPMEERF20231007) of the Environmental Restoration and Conservation Agency of Japan and the Japan Society for the Promotion of Science(JSPS) KAKENHI (Grants JP23H01544and JP23H00540). XZ acknowledges a grant from City University of Hong Kong(Project No. 9610684) for partially supporting the research in this paper. We would like to thank the three anonymous reviewers for their time, effort and the detailed review which helped improve the manuscript.
Publisher's Copyright Statement
- This full text is made available under CC-BY 4.0. https://creativecommons.org/licenses/by/4.0/
