Maps provided by the National Oceanic and Atmospheric Administration illustrate urban heat islands in Baltimore, Maryland, and Washington, D.C.
Maps provided by the National Oceanic and Atmospheric Administration illustrate urban heat islands in Baltimore, Maryland, and Washington, D.C. Credit: NOAA / Courtesy

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On another white-hot day in Kansas City, about 60 people spent Friday driving up and down streets registering the temperature and humidity every second.

The goal? To know in granular detail what intuition tells us more generally: that some places in cities are hotter than others — possibly as much as 20 degrees, according to the National Oceanic and Atmospheric Administration. 

In 2017, in an attempt to demonstrate and understand that temperature differential, the agency began providing funds to cities to gather weather data. Grants this year went to nine cities including Kansas City and two communities in Indiana: Richmond and Clarksville. About 30 other cities, including Detroit and Cincinnati, have gathered this data since the initiative began.

There’s some evidence that Kansas City has a worse-than-average urban heat problem. When it comes to the temperature difference between a city and the nearby countryside, Kansas City ranked seventh among 60 cities measured in a 2014 report by Climate Central. On a typical summer day, Climate Central estimated that Kansas City on average was 4.6 degrees hotter than surrounding rural land.

The question now: Which parts of the city are the very hottest?

A coalition of partners led by a University of Missouri-Kansas City researcher gathered the measurements and will now create a map combining tens of thousands of temperature and humidity measurements with a satellite map, allowing them to quickly learn the conditions in a given location.

“We want to show how humans have impacted the weather,” said Fengpeng Sun, an assistant professor of earth and environmental sciences at the university who is leading the project. “This is not natural.”

His primary goal is to educate Kansas City residents “that climate change is happening in our neighborhood, not just in the Arctic.”

The results also could direct corrective action more specifically to the neighborhoods most in need.

“It could very well show us that the temperature is spiking in a particular area of Kansas City,” said Kristin Riott, executive director of Bridging the Gap, a nonprofit whose mission includes tree planting. “If we went there and found out it didn’t have enough tree cover, we could plant more trees.”

Expanding the urban forest is one of the “lowest-hanging-fruit solutions for protecting occupants from climate change,” Riott said. “Every city in America is worried about its tree canopy.”

As extreme heat events become more frequent due to human-caused climate change, the risks intensify for urban communities.

“People who need green space most for cooling and other benefits, including social distancing during the pandemic and to decrease the amount of flooding on their streets during extreme rainfall, have the least,” said Timon McPhearson, director of the Urban Systems Lab at The New School in New York City.

Racism meets climate change

In 1995, Chicago suffered a sustained heatwave that killed more than 700 people, primarily in the city’s Black communities on the South and West sides — areas that have experienced decades of underinvestment in large part due to racist housing practices.

Formally established in the 1930s by the Home Owners’ Loan Corporation, redlining assigned “risk grades” to various communities — largely based on race. The name “redlining” reflects the fact that so-called hazardous neighborhoods — inhabited by BIPOC populations along with Jewish and Catholic residents — were outlined in red on loan corporation maps.

Redlining has traditionally been associated with the refusal to approve mortgage applications, as well as disinvestment of essential services such as grocery stores and banks, and an absence of amenities in affected areas. However, many redlined areas also have large expanses of pavement and hardscape. These areas often suffer from a scant tree canopy and a scarcity of green space in comparison with more affluent and predominantly White communities.

The disparities are often stark. A June 2021 opinion article in the New York Times, citing a number of sources including Earth Define and American Community Survey, reported that trees and green spaces covered an average of more than 34% in White neighborhoods, compared with less than 20% green space in BIPOC communities. 

The overlap between heat islands and redlined communities is more than a coincidence, according to Juan Declet-Barreto, a senior scientist at the Union of Concerned Scientists: 

“All of these things are intertwined. But I don’t think it was intentional in the sense that people conspired to say, ‘Let’s make these neighborhoods hotter.’ I think it was more a systematic denial of the good life to people of color. And redlining and land surface temperatures that are higher in those neighborhoods are just one indicator of that,” Declet-Barreto said. “You can see that these things go hand in hand with food deserts, for example, with the lack of schools, with the lack of a solid tax base that pays for services that many of us take for granted.

“People with lower incomes, people without a social safety net, people who have to get on a bus or ride a bike and go to work instead of driving their air-conditioned vehicle to their air-conditioned office, are generally going to be more exposed and are going to have worse health outcomes.”

The case for planting trees

In Scorched: Extreme Heat and Real Estate, a 2019 report from the Urban Land Institute, co-authors Elizabeth Foster and Katharine Burgess address a number of heat adaptation strategies, including green infrastructure solutions. 

There is also a business case to be made for incorporating green infrastructure, such as planting trees, as part of an overall heat mitigation and urban resilience strategy, according to Foster.

“Extreme heat is a dangerous hazard all by itself, but it also worsens other hazards. Really high temperatures stress utility infrastructure just when demand is highest. People tend to turn on their air conditioners and blast them all day long,” leading to a risk of widespread power outages.

“There are quite a number of market opportunities in increasing resilience, both at the offset and the market level,” Foster said. “When you implement green infrastructure, rain gardens or drought-tolerant vegetation or trees, that not only decreases or helps mitigate extreme heat or flood risk, but it also creates a really valuable social amenity.”

Low-income households pay a disproportionate amount of their income for energy costs in comparison with more affluent residents. They also often live in energy-inefficient homes or apartments without air conditioning, making it even more difficult to deal with excessive heat. Disinvested neighborhoods should be prioritized for planting urban trees as a means of mitigating this disparity, according to Declet-Barreto.

“A uniform application is not going to address the inequities that are already built into the city. You may end up putting a whole bunch of trees in neighborhoods where people don’t need the trees because they can pay for air conditioning in their homes. You need to consider the needs of the most vulnerable, which are typically the persons with lower income in any given city. And that should be a guiding principle,” Declet-Barreto said.

Enhancing tree canopies is an excellent strategy for mitigating heat island effects, according to the Environmental Protection Agency. But simply planting trees is not sufficient. Quality and maintenance must be prioritized as a matter of policy, especially in disinvested neighborhoods. Heat mitigation policies must also address the effects of decades of redlining, segregation and disinvestment for BIPOC communities. 

However, the majority of funding still flows toward wealthier, predominantly White neighborhoods. This is because municipal parks budgets are often inadequate to maintain park quality — which leaves local conservancy groups to pick up the slack. While affluent neighborhoods often enthusiastically take up this challenge, it is rarely possible for low-income neighborhoods to do so, McPhearson said.

“The challenge that we face is we have decades of that legacy in place that make it so you can’t change the status quo overnight,” McPhearson said “We have to change the systemic structures that are in place. When we’re talking about heat, it’s not just that low-income and minority communities have less access to green space. It’s that they have lower quality housing. It’s that they have streets that may have also been built out in ways that makes it hard to put new street trees in.

“And so, it means that those buildings need to be retrofitted with increased insulation. It means that they need to have green roofs installed, which are very expensive, even if they’re very effective. They need to have air conditioning subsidized because maybe they can’t afford them. So, we’re trying to at the same time deal with the current rise of heat and heat exposure and decades of racist planning that created the risk in the first place.” 

Community solutions

For his research in Kansas City, Sun identified 80 square miles in older and more developed parts of the city that include many of the zip codes where incomes generally are lower and socioeconomic challenges greater. He made it a point to include zip codes with residents with documented lower life expectancy.

In those areas, Sun said, “The concern is, ‘What is causing that? And what can we do to improve that?’”

Tru Keshia Smith grew up and now lives in one of those neighborhoods where, she said, “the sun is just going to shine.” She said street trees are lacking or, in many cases, damaged. Although the neighborhood has parks, she said they need more trees; she was at one of them recently and noticed that people were “bumped up against what trees were available.”

Smith, who is the program director for Bridging the Gap, has volunteered to take heat and humidity measurements for Sun’s project.

“I am very fond of the community I live in,” she said. “It’s very important to make sure that communities that look like me can also be part of the solution. I feel I should be part of the process.”

Audrey Henderson

Audrey Henderson is an independent writer and researcher based in the greater Chicago area with advanced degrees in sociology and law from Northwestern University. She specializes in sustainability in the built environment, culture and arts related to policy and related topics. Her work has been featured in Wallpaper magazine, the Chicago Reader, Chicago Architect magazine, Next City, Transitions Abroad, Belt Magazine and other consumer and trade publications.

Karen Uhlenhuth

Karen spent most of her career reporting for the Kansas City Star, focusing at various times on local and regional news, and features. More recently, she was employed as a researcher and writer for a bioethics center at a children’s hospital in Kansas City. Karen covers Iowa, Missouri, Kansas, Nebraska, North Dakota and South Dakota.