Cities are getting hotter: 'Thermal Justice' offers a fairer way to adapt

Cities worldwide are experiencing rising temperatures, prompting public health guidance that includes staying hydrated, limiting outdoor activity during peak heat hours, and keeping living spaces cool. These recommendations, as outlined by the WHO Regional Office for Europe, can be reinforced through clear alerts, accessible cooling areas, and protection for workers exposed to the elements.

These measures undoubtedly save lives, yet they also highlight a fundamental inequality: not everyone has the ability to decide when to cease working, afford air conditioning, reach a shaded path, or reside in a home that remains safe at night.

Researchers from ETH Zurich, the Swiss Federal Institute of Aquatic Science and Technology, and other international partners have addressed this issue in a commentary published in Nature Climate Change. They introduce the concept of "Thermal Justice," which applies the principles of environmental justice to heat adaptation. The researchers question whether a measure effectively reduces temperatures, or whether it also ensures that people can sleep, work, move, care for others, and maintain good health during heatwaves.

The Thermal Justice framework entails five key dimensions: distributional equity, recognition of vulnerability, participation, functionality, and ecosystem protection. The framework also highlights thermal displacement—a phenomenon where cooling one area may result in heat-related risks shifting to another. For instance, air conditioning provides indoor protection but generates waste heat outdoors, raises electricity demand, and excludes those unable to afford it.

Urban greening, while offering shade, can lead to increased rents and drive residents toward hotter neighborhoods. Cooling systems that rely on extensive irrigation, energy instability, or neglectful maintenance may effectively address immediate concerns but also create future vulnerabilities.

The researchers argue that a thermally just response to heat must blend emergency protection with structural changes. During heatwaves, cities should prioritize vulnerable and isolated residents, provide accessible public cooling, support worker safety, ensure shaded paths to essential services, and offer affordable indoor cooling.

Between heatwaves, they should undertake renovations to poorly insulated housing, increase durable green and blue infrastructure, adapt vegetation based on water availability, and prevent cooling investments from displacing the people they aim to protect.

Success should be evaluated not merely by the number of warnings issued, cooling centers established, or trees planted, but by whether humans and ecosystems can endure heat stress without relocating the risks elsewhere. The ideas behind this research have also been integrated into a collaborative board game called "Thermal Justice: a serious game." This interactive simulation explores various approaches cities can take to tackle extreme heat—effectively and equitably.