How scorching is too scorching?

When temperatures rise in Ahmedabad, bats faint and drop from the branches.

Climate change is pushing temperatures to the upper extremes that many mammals, including humans, can endure. Heatwaves are occurring more often and lasting longer. Residents in the world’s hottest regions — such as Ahmedabad, a city from the 15th century with around 8 million inhabitants in western India — often face struggles for extended periods. Air conditioning is a luxury there.

Although extreme daytime temperatures attract media attention, “being inside, at home, during rest periods can be equally perilous and lethal,” stated Satchit Balsari, associate professor in emergency medicine at Harvard Medical School.

Adapting to this new situation is crucial for survival. However, to evaluate adaptation strategies — for instance, how effective is a white roof in cooling the space beneath? — urban developers need fundamental data. For example, what is the actual temperature in the areas where people live and work? Ahmedabad’s official temperature is recorded at an airport weather station that is exposed to the elements, not in the densely populated urban microclimates where residences and employment are concentrated. How does the human body react to prolonged high temperatures? Or, as Balsari phrased it: “How do you gauge how hot is excessively hot?”

Harvard scholars are collaborating with grassroots authorities in India to compile one of the largest data collections ever recorded on extreme heat and human welfare.

Regions and states throughout India are forming heat action frameworks to lessen the effects on their citizens, although often neglecting informal workers.

The data will enable civil society organizations to advocate for policy solutions, given the absence of accurate figures in India regarding how heat influences labor.

To tackle these inquiries, Harvard researchers are teaming up with community leaders in Ahmedabad to assemble one of the most extensive datasets ever chronicled on extreme heat and human welfare — information that could benefit millions facing increasing temperatures globally. The research team is installing small heat and humidity sensors in the homes and workplaces of hundreds of local women — within urban settings, on the streets, and on farms — while tracking their health with Fitbits and regular assessments over the course of a year.

“This study emerged from an effort to quantify the daily experiences, the temperatures people encounter continuously in their homes, and the implications for their health, heart rate, kidney health, and sleep,” remarked Caroline Buckee, professor of epidemiology at Harvard T.H. Chan School of Public Health.

Policies aimed at counteracting extreme heat typically emphasize the risk of heat stroke, “but there are a multitude of other health repercussions that harm and kill individuals gradually,” she noted.

Balsari and Buckee head a research initiative — backed by the Salata Institute for Climate and Sustainability and aided by the Lakshmi Mittal and Family South Asia Institute — examining the effects of warming microenvironments on the lives and livelihoods of India’s impoverished workers.

“During our initial study, in certain residences we recorded temperatures up to 10 degrees higher than the data from the airport weather station,” stated Balsari. “We recognized that numerous global modeling efforts relied on data at a temporal and spatial scale that may not accurately depict the lived experiences of the millions most vulnerable in South Asia.”

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At one location, their squad recorded a heat index of 137 degrees Fahrenheit — a metric that merges temperature and humidity to represent how hot it feels. “That’s severe, but the reality that these figures exceed 120 F regularly is alarming. In many situations, these levels are uninhabitable,” Balsari remarked.

Fostering resilience with information

Participants in the study are sharecroppers and piece-rate laborers. The data gatherers are local social workers who visit participants biweekly in their residences and workplaces to upload information onto a specialized smartphone application.

Municipalities and regions across India are formulating heat action strategies to lessen the effects on their communities, though they often neglect informal laborers.

This information will empower civil society organizations to advocate for sustainable policy solutions, such as heat action plans that consider their members’ needs, since precise statistics on how heat impacts work are lacking in India.

These groups are already providing a burgeoning array of innovative responses to the heat: affordable financing to paint roofs a heat-reflecting white, purchasing umbrellas to shield market stalls, and installing vents that allow heat to escape concrete homes. Another innovation is parametric heat insurance: Members acquire a policy that compensates a day’s income when temperatures surpass a predetermined level, enabling them to remain home during the harshest heatwaves without having to choose between supporting their families and safeguarding their health.

These insurance policies aim to cover the type of losses experienced last year by Ramila Patini, who sells okra, tomatoes, bottle gourds, and fresh fenugreek from a cart she has navigated around Ahmedabad for 28 years.

Summers have become hotter and extended, she noted, particularly in recent years. “But I still need to operate my business.”

Last May, on one of the numerous days when the temperature soared above 110 F, Patini, 47, fainted and fell, striking her head on the pavement. A passerby called for an ambulance, which transported her to a hospital. “That day my vegetables went bad, resulting in a loss. Additionally, I faced hospital expenses — a double loss,” she recounted.

This year, 250,000 women secured a policy prior to the heat season, which peaks in May.

No respite

After a lethal heatwave in 2010, Ahmedabad implemented a heat action plan, the first in South Asia. It promotes public awareness of the hazards, trains medical personnel to recognize heat stroke, and increases supplies of potable water.

Nonetheless, one of its architects, Dileep Mavalankar from the Indian Institute of Public Health, contended, “there is significant underreporting of heatwave-related fatalities” throughout India, which may be recorded as heart attacks or other emergencies. “The combination of exceedingly high daytime temperatures and warm nights is particularly deadly. It is so scorching that bats are losing consciousness and falling from trees.”

Researchers are placing heat and humidity sensors in the workplaces and homes of hundreds of local women and monitoring their health with Fitbits and regular checkups.

Data collectors visit participants every two weeks to upload information into a smartphone app.

Initial information from the project is confirming concerns about living environments, which remain warm and humid well into the monsoon season.

Initial data from the initiative — known as “Community Heat Adaptation and Treatment Strategies” — is corroborating concerns regarding domestic environments, which stay warm and humid well into the monsoon season.

“The architecture of homes is such that they absorb and retain a significant amount of heat,” said Robert Meade, a postdoctoral research fellow with the Salata cluster. “Consider a street vendor. They work during the hottest time of day. Then they return to overheated homes where they must recuperate, tend to family, and clean — all in a setting that is actually hotter than the outside and does not experience that same cool-down in temperatures noted outside at the airport weather station.”

An adaptation framework

Down a path only wide enough for pedestrians and mopeds, Karunisha Sheik, 55, operates as a seamstress in her one-room home in Ahmedabad.

On the cornflower-blue wall, a white sensor captures the humidity and temperature, around the clock, year-round. A thermometer shows 93 F on a March afternoon.

“My neighbors gossip. They claim the sensor is a camera, that I am under surveillance. But I understand the data is being collected to assist us,” Sheik explains how it “grows hotter each year, so hot I become too weak to work.”

Without local trust in civil society, the Harvard researchers would struggle to reach so many vulnerable women in India’s poorest areas, stated Buckee, the principal investigator.

“Implementing this type of study is extremely challenging. You have hundreds of participants, sensors requiring checks, sensitive data. Regular lab tests are necessary. This level of coordination is simply unattainable in most areas. It is achievable here because our partners are committed to the work and care about uncovering the solutions,” Buckee elaborated.

The research cluster is now expanding — reaching out to other regions of India, distributing Fitbits and sensors in time for peak heat this year. As they compile empirical data to create a foundational understanding of health risks associated with climate change, they are pioneering a fresh type of adaptation model designed by and for workers.

“We view this as a research platform that our partners can utilize to assess their own adaptations, to determine which options are most effective for them,” Buckee concluded.

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