Inside the race to prepare cities for extreme heat — Phys.org

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Inside the race to prepare cities for extreme heat — Phys.org | AIPROPX

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Add as preferred source A sea of corrugated metal roofs stretches into the distance across an informal settlement in Makassar, Indonesia.

Around 40% of the industrial hub's population dwells in these makeshift communities, where a lack of basic municipal services and air conditioning leaves residents routinely exposed to temperatures above 90 degrees Fahrenheit.

In the coming months, a couple dozen roofs in the settlement will stand out with bright new coats of highly reflective white paint. They are part of a Stanford Doerr School of Sustainability project testing one of the simplest, cheapest tools available for lowering sweltering temperatures inside homes by as much as 5 degrees Fahrenheit.

"Those few degrees can make a big difference," said Rishee Jain, a leader of the Makassar project and an associate professor of civil and environmental engineering at Stanford.

Lowering the temperature by even a few degrees on the hottest days matters because of the limits of our physiology. When it's too hot and humid for evaporating sweat to keep us cool and maintain our core temperature, the heart, kidneys and other organs work harder to compensate.

The strain can exacerbate conditions such as cardiovascular disease, diabetes and asthma, and prolonged exposure can prove deadly even for the young and healthy. Furthermore, during heat waves, people have trouble sleeping, leaving them susceptible to illness; in Makassar specifically, heat waves correlate with surges in work absenteeism and cases of dengue fever.

"Big interventions can take decades to bring into place, and we don't have that time. People are suffering from heat events now," said John Openshaw, a Stanford assistant professor of medicine who is leading the white-roofs project team with Jain. "We really need to start thinking about the interventions that we can implement quickly."

Driven largely by climate change, heat waves are rapidly increasing in duration and frequency worldwide, with some regions now enduring 50 more heat-stress days annually than in 1950 . In major U.S. cities, heat wave frequency has tripled from two events per year to six. The summer of 2026 has brought dangerous heat waves to broad swaths of India, South America, North America and Europe, the world's fastest-warming continent.

Jain and Openshaw are among a growing number of researchers seeking ways to better cool individual buildings and entire cities, where dark asphalt and impervious building materials trap heat and can drive temperatures far hotter than in nearby rural areas. The work is part of a broader push at the Doerr School of Sustainability to help people and communities adapt to growing extremes, from record wildfires and droughts to historic floods and hurricanes.

"As global warming continues to unfold, we can expect accelerating occurrence of the most extreme events, particularly for heat waves but also for extreme wet events and other extremes," said climate scientist Noah Diffenbaugh, the William Wrigley Professor and Kimmelman Family Senior Fellow in the Doerr School of Sustainability.

Many human and natural systems buckle under those same extremes. "One of the real challenges is how we leapfrog ahead to be prepared for even more extreme conditions than we're facing now, even if the world is successful at decarbonization and curbing global warming," Diffenbaugh said.

The need to adapt extends to places with historically mild climates such as San Francisco, London and Paris, where few homes have air conditioning and most buildings were designed to retain heat.

"These are not places you think about for urban heat, and they're not equipped for it," said Gregory Deierlein, the John A. Blume Professor in the School of Engineering.

Deierlein and colleagues are exploring ways to help cities better prepare for nature's slings and arrows. Because most large cities face more than one serious threat at once, the researchers are looking for practical solutions to improve public health and safety in the face of multiple hazards.

"Many types of natural disasters are becoming more common and more extreme, causing greater damage and becoming more unpredictable. Understanding where and how hazards happen will help us better prepare," said Marshall Burke, a Stanford professor of environmental social sciences who studies air pollution and wildfire smoke, and economic impacts from climate change.

In San Francisco, Deierlein and colleagues are working with the city's Office of Resilience and Capital Planning to develop tools that simulate how buildings and the people inside them would fare in earthquakes, heat waves and other events across a range of plausible scenarios. From there, the team plans to model potential solutions, principally through updated building codes for new construction and retrofits for existing structures.

"We're taking an assessment, looking at vulnerabilities and quantifying those vulnerabilities to prioritize actions that the city can take in terms of policies or programs," said Deierlein, who is a professor of civil and environmental engineering, a joint department of the Doerr School of Sustainability and the School of Engineering.

The team has conducted pilot studies in several San Francisco neighborhoods, including Chinatown, where small apartments in older, seismically vulnerable buildings house many residents over age 65, a group that's also most at risk in a heat wave .

Wherever possible, the strategy is to bundle solutions rather than deal with vulnerabilities piecemeal. "By understanding a building's multiple vulnerabilities, like seismic and heat, we can think about vulnerabilities collectively to see if there's any intersection that makes it more feasible for the city to address ...