The Urban Resources Initiative, a YSE affiliate, plants trees in New Haven communities based on data from a new study that found that underserved communities experienced higher overall temperatures. Photo: Ian Christmann
People of Color Exposed to More Extremely Hot Days
A new study by Yale School of the Environment researchers found that communities of color in the U.S. face more heat exposure and have fewer cooling options than predominantly white communities and those disparities are increasing.
People of color in the U.S. are disproportionately exposed to extreme urban heat. Yet, most studies on urban heat have focused on large cities and urban centers at a fixed point in time. Less is known about how heat exposure changes over time, especially in smaller metropolitan areas. A new study by Yale School of the Environment researchers examines how increasing urban heat is affecting low-income and people of color communities.
“In the current literature, there are a lot of studies showing that underserved communities, such as communities of color and low-income communities, are disproportionately affected by climate change. However, there’s still a large knowledge gap on how the urban heat disparity is changing; how underserved communities are affected by the change in urban heat; and how the adaptation capability of those communities is changing,” said Shijuan Chen, the study’s lead author and a postdoctoral associate at YSE.
The key takeaway is that because environmental justice communities are disproportionately affected by increasing temperature, we need to prioritize the underserved communities when developing climate adaptation strategies.”
Shijuan ChenPostdoctoral Associate at YSE
The study showed that underserved communities experienced higher overall temperatures, more sweltering days, and more significant increases in heat exposure over a 30-year period. For example, from 2003 to 2020, communities in Connecticut in which the majority are people of color have experienced about 35 more extremely hot days than have communities with a majority white population.
In the study, which was published innpj Urban Sustainability, the research team focused on the 10 largest cities in the state of Connecticut — Bridgeport, Stamford, New Haven, Hartford, Waterbury, Norwalk, Danbury, New Britain, Hamden, and Manchester. The study’s authors, including Chen and Karen Seto, the Frederick C. Hixon Professor of Geography and Urbanization Science at YSE, used U.S. census data from 1990, 2000, 2010, and 2020, land use parcel data, building-level property assessment data, satellite data, airborne data, and OpenStreetMap (OSM) data, in their research. They found that communities of color face greater heat exposure and fewer adaptation resources compared to predominantly white neighborhoods.
“As we looked at a 30-year time period, we were able to understand that not only are low-income communities and communities with a majority of people of color in Connecticut more exposed to urban heat islands today, that disparity is increasing over time,” said Katie Lund ’24 MEM, one of the study’s authors.
Inequity of tree cover between predominantly POC and predominantly white communities. (a) The mean tree cover in predominantly POC communities is 15% lower than in predominantly white communities (p < 0.001); (b) Communities with higher POC percentage have lower tree cover (p < 0.001).
[Figure 10 from Chen, S., Lund, K., Murphy-Dunning, C. et al. More extremely hot days, more heat exposure and fewer cooling options for people of color in Connecticut, U.S.. npj Urban Sustain 4, 47 (2024)]
Chen noted that because the research team looked at a longer time span, it was clear disparities are also increasing, and the accumulative effect cannot be ignored.
“The key takeaway is that because environmental justice communities are disproportionately affected by increasing temperature, we need to prioritize the underserved communities when developing climate adaptation strategies,” she said.
One challenge, according to Chen, was finding the air conditioning (AC) ownership rate. The state of Connecticut didn’t publish new data on AC access until they were halfway through the study.
Heat vulnerable communities face additional challenges due to lower air conditioning ownership rates and lower urban tree cover, both critical tools for mitigating the impact of extreme heat. The researchers found that hotter communities have lower AC ownership rates. For example, the mean AC ownership rate in communities in which the majority are people of color was 23% lower than in white neighborhoods. Similarly, tree canopy cover was significantly lower in predominantly people of color communities, limiting outdoor cooling options.
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The research team noted that the disparities have persisted and even widened in recent decades.
“A lot of times, when we think about planning decisions that have made certain communities more vulnerable, we think, ‘Well, that happened 30 years ago, and we’re making it better now.’ The benefit of our study is that we could show that even though some environmental justice efforts have advanced, disparities in heat exposure are still increasing. That’s important,” Lund said.
The research team also found that increasing tree canopy and improving access to home air conditioning are essential to addressing these disparities and enhancing resilience to climate change.
They are now working with the Urban Resources Initiative (URI), a program of YSE, as well as a nonprofit guided by a local board of directors, to help identify communities to prioritize for tree planting.
“The Seto Lab team developed spatially explicit data depicting communities most vulnerable to increasing heat that allowed URI to strategically target tree planting to be more impactful,” said Colleen Murphy-Dunning, director of URI and the Hixon Center for Urban Sustainability.
