Environmental engineering researcher Lucas Gobatti and a team of scientists at ETH Zurich in Switzerland have proposed a framework called thermal justice to combat urban heat inequalities. The study, published in the scientific journal Nature Climate Change, argues that city heat adaptation must focus on who actually benefits from cooling interventions rather than simply lowering overall municipal temperatures.
The authors noted that while a city could construct a major park, its ability to protect those most in need would remain limited if the facility was located far from vulnerable neighborhoods.
Standard public health advice during heatwaves typically instructs residents to drink water, avoid exercise during peak sunlight hours, and seek shade. However, the ETH Zurich research team pointed out that these simple recommendations rely on an unwritten assumption that every resident has the practical ability to follow them.
In reality, many urban residents cannot choose to stop working at three in the afternoon, afford air conditioning, or live in housing that remains cool overnight. Furthermore, not all commuters can choose a shaded route when traveling to work, medical appointments, or childcare facilities.
Five dimensions of heat inequality
Two people residing in the same city can experience an identical heatwave in vastly different ways based on their living and working conditions. One individual might work from home in an air-conditioned room and commute by private car, while another works outdoors, lives in a poorly insulated dwelling, and relies on public transport across streets lacking tree canopy.
Although the thermometer records the same temperature for both residents, the health and safety risks they face are entirely unequal. To address these disparities, Gobatti's team structured their thermal justice framework around five distinct dimensions.
The first dimension addresses the fair distribution of thermal loads and benefits, examining who bears the heat and who gains access to solutions. The second dimension recognizes that social and structural conditions create specific vulnerabilities rather than occurring by chance.
The third dimension focuses on participation, questioning who holds the power to decide how a city adapts to heat. The fourth dimension assesses whether individuals possess the actual capacity to safely live, work, commute, and care for others during extreme weather events.
The fifth dimension expands the scope to incorporate non-human ecosystems and future generations into justice considerations.
Paradoxes of urban cooling solutions
The research highlights that common cooling interventions, such as planting trees, installing air conditioning, or constructing cooling centers, do not automatically produce fair outcomes. In several instances, cooling solutions can generate secondary problems for vulnerable populations.
Air conditioning provides immediate indoor protection during heatwaves, but individual units vent exhaust heat into outdoor spaces and consume substantial electricity. Depending on how that electricity is generated, the appliances can increase greenhouse gas emissions that fuel global warming, while remaining financially unaffordable for lower-income households.
Urban greening initiatives present similar paradoxes. Planting trees adds shade, lowers local temperatures, and improves thermal comfort, but enhancing a neighborhood can also increase property values and housing costs.
If rents rise, lower-income residents who need green space the most may be forced to relocate to warmer, unshaded districts. Recent scientific literature on nature-based solutions confirms that while these measures can alleviate thermal inequality, they can also reproduce it depending on access and decision-making involvement.
The risk of thermal displacement
The ETH Zurich study labels this phenomenon thermal displacement, defining it as a process where resolving heat in one location or for one group transfers part of the burden to another place, another demographic, or future generations.
Because of thermal displacement, adapting cities to rising heat becomes a complex socio-economic issue rather than a purely technical engineering challenge. Urban planners must analyze who lives and works in high-heat areas, who can afford to leave or protect themselves, and who controls local policy decisions.
The authors highlighted several common urban design flaws, including public water fountains placed in locations inaccessible to elderly residents or people with reduced mobility. Similarly, municipal cooling centers that require a 20-minute walk under direct sunlight offer little practical relief to vulnerable groups.
Official heat alerts also lose effectiveness when recipients lack the personal resources, housing flexibility, or occupational freedom to act on the warnings.
Emergency responses and structural changes
To overcome these barriers, Gobatti's team proposed combining immediate emergency responses with long-term structural changes. During active heatwaves, municipal authorities should prioritize exposed or isolated individuals, guarantee accessible public cooling spaces, protect outdoor workers, and establish shaded transit routes to essential services.
Between heatwaves, cities must undertake structural work to upgrade poorly insulated housing stock and build durable green and blue infrastructure, such as water features. Planners should select urban vegetation that aligns with local water availability to ensure long-term sustainability.
Crucially, municipal investments designed to make neighborhoods more livable must include safeguards to prevent the displacement of existing residents. The authors stated that the goal of climate adaptation should not merely be adding more trees, air conditioning units, or cooling centers, but ensuring those solutions reach those in need without creating new risks elsewhere.
Educational board game on urban resources
To bring these concepts into public policy debates outside academic circles, the ETH Zurich team developed a board game titled Thermal Justice: a serious game.
In the game, players must protect a simulated city from extreme heat while managing limited resources of energy, water, physical space, and money. Participants are forced to decide which neighborhoods and demographics receive cooling solutions under tight constraints.
The board game has been made available through open access in the ETH Zurich research collection.
The researchers concluded that when extreme heat strikes, everyone looks at the same thermometer, but not everyone experiences the same summer.
