As urban heatwaves become an increasing concern worldwide, Professor Guo Hai, Professor of the Department of Civil and Environmental Engineering, and global researchers have conducted groundbreaking research on the effectiveness of green interventions in cooling urban heat across various regions.

The study, published in the international interdisciplinary journal The Innovation, is the first of its kind to embark on a comprehensive global review of the effectiveness of green-blue-grey infrastructure (GBGI) in air cooling.

The study revealed regional and city-specific variations in the effectiveness of GBGI for mitigating urban heat. GBGI encompasses green infrastructures with lush trees, grass, and hedges; blue infrastructures with water-based features like pools, lakes, and rivers; and grey infrastructures like green walls, facades, and roofs.

Beat the urban heat

In Europe, Asia, North America, and Australia, GBGI manifested in temperature reductions up to 18.9°C, 17.7°C, 12°C, and 9.63°C, respectively. Asian cities demonstrated the most effective means for urban cooling through constructed grey infrastructures like roof gardens and pergolas.

Mainland China cities showcased notable effects of various GBGI features in mitigating urban heat, with the most effective means including botanical gardens, wetlands, green walls, and attenuation ponds exhibiting temperature reductions of up to 10°C, 9.27°C, 8°C, and 7°C, respectively. In Hong Kong, parks, green roofs, and golf courses play substantial roles in cooling urban heat, resulting in temperature reductions of 4.9°C, 4.9°C, and 4.2°C, respectively.

To facilitate GBGI implementation, the research team introduced a nine-stage framework that outlines stages of stakeholder engagement, feasibility studies, design, policy development, implementation, monitoring, evaluation, and eventual upscaling and replication.

Professor Guo stressed the importance of adopting a holistic approach for future GBGI implementation to optimise the multifunctional benefits and effectively address sustainability goals.

The study's GBGI heat mitigation inventory offers valuable insights for policymakers and urban planners worldwide, assisting them in prioritising effective interventions to reduce the risk of urban overheating and promote community resilience.