‘Extreme Heat’ Days Triple Since 1980s, and More Are Coming

by Amy Norton
HealthDay reporter

WEDNESDAY, Oct. 13, 2021 (HealthDay News) — A new study suggests that city dwellers around the world are sweating three times as much on “extreme heat” days as their counterparts in the 1980s.

This study is the latest to chart humans’ increasing exposure to dangerously high temperatures. Experts said she’s looked at what’s happening in finer detail than previous research has done — and suggests exposure to extreme heat is more common than thought.

Researchers estimate that 1.7 billion urban dwellers – or roughly one-fifth of the planet – experienced an increasing number of extreme heat days between 1983 and 2016.

These are temperatures that increase the risk of heat illness even for healthy people if they work or exercise outdoors.

For people who live in hot cities, “it’s not news that it’s hot,” said study leader Cascade Tuholsky, a research scientist at the Earth Institute at Columbia University in New York City.

It’s not that urban areas are the only places that feel the heat, said Tuholsky, who was a graduate student at the University of California, Santa Barbara, at the time of the study.

But cities thrive due to a combination of two factors: climate change and the so-called urban heat island effect. This is where the lack of grass and trees and the abundance of concrete and asphalt conspire to trap heat.

In addition, more of the world’s population has moved to urban centers – which Tuholske’s team found was an additional cause of increased exposure to extreme urban heat.

Results recently published in Proceedings of the National Academy of Sciences, It is based on data from more than 13,000 cities around the world. The researchers estimated the residents’ exposure to extremely hot days – defined as a “wet globe” temperature of 30°C (86°F) or higher.

This is a scale that takes into account not only temperature, but also humidity, wind speed, and cloud cover. Gives an idea of ​​what “sense” temperature is for people who go out in the sun.

When the temperature of the humid globe reaches 30 degrees Celsius, a healthy person will begin to feel heat exhaustion after 30 minutes of working or exercising outdoors, according to the US National Weather Service.

“It’s not just the elderly who are infected,” Toholsky noted.

His team estimates that during the study period, people in those urban areas experienced a 200% increase in exposure to extreme heat days. But the effect was not uniform: 25 metropolitan areas accounted for a quarter of the increase in exposure to extreme heat.

The top four places were: Dhaka, Bangladesh; New Delhi, India; Kolkata, India; Bangkok, Thailand.

However, the problem was widespread, with nearly half of urban areas showing an increased population exposure to extreme heat.

The findings underscore the importance of gathering fine details about what city residents are already living with, according to Dr. Mona Sarfati, head of the Climate and Health Program at George Mason University in Fairfax, Virginia.

She said some innovative projects aim to do so. In Miami, for example, researchers have armed “citizen scientists” with heat sensors to track the temperatures they encounter in everyday life. Sarfati noted that the average temperature at one of the bus stops exceeded 100 degrees Fahrenheit.

Sarvati and Toholsky said that while global warming needs to be addressed through broad changes – including less reliance on fossil fuels such as oil and coal – domestic actions are also important.

Sarfati said cities could create more “green spaces,” not only to provide shade but also to help cool the air. Some cities, such as Phoenix, apply a special coating over the asphalt to lower the temperature of paved areas.

Sarfati said local health departments and employers could also do more to spread awareness. She noted a recent study in Texas, where a “heat stress awareness program” was found to reduce heat-related illness among city employees who work outdoors.

“People are not necessarily aware of how quickly they can be exposed to heat,” Sarfati explained.

As with many health conditions, Toholsky said low-income and marginalized people are among the most vulnerable, as they often work outdoors and lack air conditioning and other options to mitigate their exposure to dangerous heat.

He noted that there is a particular concern for people who live in cities around the world that are not simply designed to sustain the large populations they now have.

more information

The World Health Organization has more on climate change and health.

SOURCES: Cascade Tuholske, Ph.D., Postdoctoral Research Scientist, The Earth Institute, Columbia University, New York City; Mona Sarfati, MD, MSc in Public Health, Director of the Climate and Health Program, George Mason University, Fairfax, VA; Proceedings of the National Academy of Sciences, online, Oct 4, 2021


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