Climate change, coupled with escalating population growth, is making big-city life increasingly risky, experts agree.
The combined effects of rising temperatures and residential booms means exposure to deadly heat conditions has tripled since the mid-1980s, according to a Columbia University study in the Proceedings of the National Academy of Sciences released Monday.
As people flock to cities in search of a better life, or at least higher wages, they are often taking up residence in homes made of concrete — material that traps heat and generates an “urban heat island effect” that in some instances can be fatal.
“This is driven by more people who are made disproportionately vulnerable due to lack of protective resources (shade, air conditioning) and more baseline risk (elderly or young children),” David Eisenman, who directs the UCLA Center for Public Health and Disasters and was not involved in the study, said in an email to The Hill.
“Simply put, the more cities heat up and at the same time fill up with persons vulnerable to the effect of heat, the more there will be bad outcomes from heat waves in cities.”
Population growth accounted for two-thirds of heat exposure increase, while warming was responsible for a third — with the most dire impacts concentrated among cities in lower altitudes, according to the new study, titled “Global urban population exposure to extreme heat.”
The worst-hit city was Dhaka, Bangladesh, which saw a surge in exposure due to its “ballooning population” from 1983 to 2016, according to the authors. In the same time frame, about 40 U.S. cities saw increased exposure as well, mostly clustered in Texas and along the Gulf Coast.
“From an absolute temperature point of view, it’s just much hotter in the South of the United States,” said Vivek Shandas, a climate adaptation professor at Portland State University, who noted the high rate of population growth in Southern cities compared to many other parts of the country.
“Without question, Texas is, in my mind, right in the path of a lot of the most intense weather-related extremes that I think we’re going to see going into the future,” Shandas said.
Kevin Lanza, an assistant professor at the University of Texas Health Science Center at Houston School of Public Health, said Texas poses several health risks.
“Texas has a lot of land, a lot of space, geographically,” said Lanza, who serves on a team monitoring urban heat islands in Austin. “It’s primed, culturally and politically, to be growing into a space that has a greater population. You’ve seen this kind of huge move of the West Coast population to places like Austin, Dallas, Houston, and I suspect that’s only going to continue moving forward.”
Lanza’s recent work in Austin has involved installing temperature and humidity sensors in various settings — tree canopies, parking lots and bus shelters — to measure temperature and humidity every five minutes.
Once the city of Austin is equipped with the data, Lanza said he hopes to see officials pinpointing the locations of urban heat islands and determining “how that matches with the different sensitivities and adaptive capacities of the populations living in those spaces.” From there, he added, policymakers can implement urban heat management strategies to best support the health of specific populations.
“An important thing to note is that everyone is affected by heat,” Lanza said. “It’s just that some are affected earlier by heat and disproportionately by heat.”
Across the U.S., urban heat has been an “unequivocal” health and equity issue for the past century, stemming from discriminatory housing policies that prohibited certain populations from getting home loans — which pushed these groups to areas with fewer amenities, Lanza said. With fewer trees and more buildings absorbing sunlight, lower income populations and communities of color have “disproportionately higher exposure to higher ambient temperatures,” he said.
Shandas, the Portland State professor, recalled how he and his 11-year-old son went outside during the height of Portland’s late June heat wave, to measure both air and surface temperatures. They found some walls and roads that hit 160 to 180 degrees Fahrenheit, while air temperatures varied from 99 degrees to 124 degrees depending on the neighborhood.
“So we see this large disparity in who’s getting hit with not just a heat wave and greater exposure,” Shandas said, “but that exposure is very disproportionate across an urban region.”
“We saw people in tents that the surface temperature of those tents were 135 degrees,” he said. “And they were houseless right on the side of the street — right in front of the direct sunlight.”
For Shandas, one way the Columbia study could contribute to ameliorating the crisis would be through a green climate fund “filled up with trillions of dollars of potential mitigation adaptation resources” that’s directed to the places identified by the researchers as most vulnerable to heat-related deaths.
Ideally, he said, such investments would go toward the places where the largest number of lives could be improved. But more immediate, on-the-ground solutions that are already occurring in places like Austin and Massachusetts involve implementing heat-mitigating design plans, as well as building with materials that absorb less heat and prioritizing green spaces, according to Shandas.
“Tailored solutions is kind of where we’re going with a lot of this,” Shandas said. “I do think folks are starting to wake up little by little — and much slower than I would like — but definitely starting to wake up in terms of the potential distribution effects of it, so these actions I think are very hopeful, fundamentally.”