Why heat is the defining climate challenge for cities

At COP30 in Belém this November, cooling and extreme heat was high on the global agenda. For the first time, governments put forward concrete steps to scale up sustainable cooling, strengthen heat-health systems, and support cities already struggling with rising temperatures.

Ep. 17: Why heat is the defining climate challenge for cities
Listen to the podcast or read the transcript in the source article webpage

The Global Cooling Pledge at COP30 has now gained new momentum, moving into its implementation phase, signalling that the global governments finally recognize heat not as a seasonal inconvenience, but as a major climate and development risk.

The shift is timely as the signs of a heating world is becoming even more apparent: record-breaking heatwaves in Europe, dangerously warm nights spreading in cities across continents, and millions of people in Asia working and living in conditions no longer fit for human comfort.

In the latest episode of Environment and Policy in Asia podcast, SEI Asia’s Charmaine Caparas, Andreas Hoy, climatologist at SEI Tallinn, and Winston Chow, Co-Chair of IPCC Working Group II and Professor of Urban Climate at Singapore Management University, unpack the harsh climate realities unfolding in streets, homes and neighbourhoods from Tallinn to Singapore to Manila.

Heat in cities is the poster child of climate disruption. You get a double whammy: global warming on one hand, and on the other, the way cities themselves trap and amplify heat.

Winston Chow

Winston explains how global warming and urbanization amplify each other: forests and open land give way to concrete, asphalt and steel; air-conditioners push heat outdoors; and, traffic, industry and dense development trap warmth long after sunset. The result is a pattern familiar to many city dwellers: heat that doesn’t wait for summer, and nights that never truly cool.

Risks and key adaptation options in select cities across Asia. Graphic: IPCC Sixth Assessment Report.

Andreas’ observations from Europe show just how destabilising this can be. Southern Europe saw temperatures above 46°C this year, while the Arctic Circle experienced an unprecedented period of continuous days with25°C and higher. Those numbers may seem modest to people in Bangkok or Kuala Lumpur, but in places built for cold winters and dark nights, the impacts are severe. Homes designed to retain heat in winter now trap it in summer. Elderly people struggle to recover overnight. And despite two decades of lessons since the deadly 2003 heatwave in parts of Europe, the capacity to protect vulnerable groups remains uneven across the region.

The inequality of heat

In Asia, the vulnerability looks different but is driven by the same underlying inequalities. Outdoor workers, residents of informal settlements and low-income communities are consistently the most exposed to heat. Winston notes that in many fast-growing cities across South and Southeast Asia, Africa and Latin America, millions of people– from construction workers to street vendors- make their living outdoors. Rising temperatures and longer heatwaves mean chronic exposure, with limited options for rest, shade or cooling.

Across both regions, the parallels are clear: heat risk has less to do with latitude and more to do with access. Trees, green spaces, ventilation, safer housing, early warnings and healthcare all determine who suffers most.

Designing cool cities

The episode highlights promising examples of what heat-resilient cities can look like—and how closely these align with the COP30’s global push for more accessible – and less polluting – cooling solutions to address deadly heatwaves are becoming lived realities across regions.

In Pärnu, Estonia, Andreas’ team integrates climate data with social information, like age, income, health and mobility, to identify which neighbourhoods need cooling interventions first, while a 14-kilometre “pollinator highway” in Tallinn acts as a living green corridor that naturally cools the surrounding districts.

Andreas and team install sensors at the Tallinn pollinator highway. Photo: Anette Parksepp / SEI Tallinn.

Winston points to Singapore’s long-term planning: orienting buildings to catch prevailing winds, staggering tower heights to pull cooler air down to street level, and using traditional design principles—like raised housing that once allowed breezes to flow—to inform modern public housing. Through the Cooling Singapore project, his team is also building a “digital urban climate twin” to test how different design choices affect heat.

The future of heat governance: science meets policy

Despite the progress, both experts stress that technology alone won’t solve the heat crisis. So what will?

Andreas argues that cities still treat heat as a temporary emergency rather than a structural challenge that must shape zoning, building design, public health systems and long-term investment. Winston puts it plainly: ignoring heat risks carries economic consequences—from reduced productivity to residents and businesses choosing to relocate.

We often treat heat as a short-term emergency. But heat is a structural risk — it needs to be built into how we plan cities, design buildings, and organize health systems.

Their shared message is simple: the world already knows what works. Green spaces, blue infrastructure, climate-smart building codes, early warning systems, inclusive heat action plans. The gap is not in knowledge but in implementation and in recognising that cooling is a public good, not a luxury.

COP30’s heightened focus on cooling provides an important political push. But it is cities and communities that will determine whether those promises translate into cooler, safer, more liveable places.