Tall & Urban News

A recent study has been published by the Proceedings of the National Academy of Sciences which highlights an issue rapidly growing cities face: increasing exposure to extreme heat and humidity for their inhabitants. The study was conducted with data collected from 1983 to 2016 for 13,115 cities worldwide. Extreme heat and humidity conditions, classified by being 30 degrees Centigrade on the “wet-bulb globe temperature” scale (roughly 106 degrees Fahrenheit using the “real feel” index) can make it hard to function outside for healthy people and can make those that are unhealthy become very sick and can even cause death.

The study revealed that the number of person-days in which city dwellers in the locations studied were exposed to extreme heat and humidity tripled since the 1980s, going from 40 billion per year in 1983 to 119 billion in 2016. (A person-day is the equivalent of one person's working time for a day.) Because the study did not cover any years past 2016, these numbers did not even include the more recent series of heat waves that hit the United States and Canada this summer which resulted in the deaths of hundreds of people. 

The study showed that there were two main causes for the increase in exposure. The first factor is the increase of population in these cities and the second factor is the actual warming of the city. On average, the first factor accounted for two-thirds of the exposure increase whereas the second factor accounted for a third. However, these proportions varied city-to-city.

This study and similar studies can become a catalyst for implimenting strategies to combat local heat issues. Some strategies known to counteract the urban heat island effect include bringing trees and more vegetation into the city, reducing a city's surface area that has impermeable surfaces like concrete or asphalt, or modifying roofs to include vegetation or lighter colors.

For more on this story, go to News from the Columbia Climate School.