Exposure to extreme heat and humidity in urban areas has tripled since the 1980s

Photo (c) Marc Bruxelle - Getty Images

Experts say significant population growth is one contributing factor

A new study conducted by researchers from the Earth Institute at Columbia University found that extreme heat and humidity levels in cities around the globe have increased significantly since the 1980s. 

Their work revealed that these heat conditions have tripled in recent decades due to substantial population growth in urban areas and rising global temperatures.

“This has broad effects,” said researcher Cascade Tuholske. “It increases morbidity and mortality. It impacts people’s ability to work, and results in lower economic output. It exacerbates pre-existing health conditions.”  

Identifying trends in heat patterns

To get an idea of the temperature trends over the last four decades, the researchers analyzed ground thermometer readings and infrared satellite imagery from 1983 to 2016. They then looked at population data from Columbia’s Center for International Earth Science Information Network. 

In 1983, there were 40 billion person-days of extreme heat and humidity. By 2016, that number jumped to just under 120 billion. In this study, extreme heat was categorized as 106 degrees Fahrenheit or higher. 

While population growth and rising global temperatures were the two primary reasons this increase occurred, the researchers found that the former was more significant than the latter; population growth was responsible for two-thirds of the uptick in extreme heat exposure. 

Which areas have been affected the most?

In the U.S., the researchers identified 40 cities that have experienced the brunt of these heat waves. The findings suggested that some cases were caused by population growth -- like in Las Vegas and Charleston, South Carolina -- while others were due to intense heat -- like in Baton Rouge, Louisiana, and Gulfport, Mississippi. 

The study also showed that the combination of the two factors contributed to more days of extreme heat in some places around the U.S. This was the case in many cities across Texas, including Austin, San Antonio, and Dallas-Fort Worth, as well as in Pensacola and other cities in Florida. 

Moving forward, the researchers hope that these findings can help community leaders better serve consumers in large cities who are consistently impacted by extreme heat. 

This research “could serve as a starting point for identifying ways to address local heat issues,” said researcher Kristina Dahl. “This study shows that it will take considerable, conscientious investments to ensure that cities remain livable in the face of a warming climate.” 

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