On 9 December 2025, Prof. John D. SPENGLER from Harvard University delivered a PAIR Seminar titled “If you think it is hot now – just wait a few years”. The seminar explored innovative approaches to cooling neighbourhoods, saving lives, and strengthening local economies. The event attracted over 70 in-person participants and an online audience of more than 13,000 across various social media platforms.
Prof. Spengler began his presentation by highlighting warnings from experts regarding the climate crisis and global warming. He emphasised that transitioning from fossil fuels—such as coal, oil and natural gas—to renewable energy, including wind, solar and other green alternatives, is a key solution to these challenges.
Using the analogy of the Earth as a patient visiting a doctor, Prof. Spengler described how his team and collaborators monitor the planet’s vital signs. This includes measuring ground and sea temperatures; collecting fluid samples from seas, lakes, rivers and water pipes; and monitoring moisture and relative humidity. The findings indicate that a significant portion of the world’s population will experience, for the first time in human history, prolonged exposures to uncompensable extreme moist heat.
As urban heat islands contribute to increased heat-related mortality, Prof. Spengler warned that the widespread use of air-conditioning, dark surfaces and high glaze materials are among the main culprits. To address these issues, he advocated for the adoption of smart surfaces, such as trees, solar panels, bioswales, urban meadows, porous pavements, reflective pavements and cool roofs.
Prof. Spengler went on to share recent collaborations with industry partners and universities on smart surface projects. He asserted that smart surfaces offer cost-effective and scalable tools for climate adaptation, and that global urban adoption of current reflective surface technologies could reduce up to 78 gigatonnes of carbon dioxide equivalent (CO2e). Smart surfaces can also cool cities by up to 5°F, providing a powerful, systemic public health intervention. These measures help protect outdoor workers, reduce electricity costs for families and businesses, and sustain economic activities such as tourism, construction and recreation. Furthermore, under-invested, low-income communities and communities of colour are typically 10–15°F hotter than wealthier areas; smart surfaces can help redress these inequalities.
Prof. Spengler emphasised the importance of working together with young people and the wider community to create a cooler world. The objectives are to assess the accrued health benefits and costs for cities adopting extreme heat mitigation strategies, as well as to examine differential impacts and benefits through the lens of environmental justice.
Following the presentation was a lively question-and-answer session moderated by Prof. CHEN Qingyan, Director of PAIR. Both the on-site and online audiences engaged in a productive discussion with Prof. Spengler.
Please click here for an online review.
| Topics | PAIR Seminars |
|---|---|
| Research Units | PolyU Academy for Interdisciplinary Research |
Prof. John D. SPENGLER
Akira Yamaguchi Professor of Environmental Health and Human Habitation
T.H. Chan School of Public Health
Harvard University, USA
Prof. John (Jack) Spengler, Akira Yamaguchi Professor of Environmental Health and Human Habitation, at the Harvard T.H. Chan School of Public Health, has over 40 years’ experience in environmental health and exposure science, characterising the exposure to and effects of contaminants in outdoor and indoor environments. Through studies of homes, office buildings, schools, and transit systems Spengler has investigated design, materials, maintenance, and behaviours that mitigate exposures to harmful contaminants. During the SARS CoV-2 pandemic, his team examined transmission and mitigation of airborne viruses in schools, airplanes, airports, and buses. Recent studies have looked at health and the built environment and the wellbeing benefits of exposure to Nature. Spengler’s current teaching and research are focused on climate change and sustainability challenges. Recognising the health risk of extreme heat, Spengler’s group is collaborating with the Smart Surface Coalition, assisting cities in the US and India to implement cost-effective strategies to mitigate the adverse effects heat waves.
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