Almost a Quarter of U.S. Population Vulnerable to Rising Heat

New Community Resilience Estimates For Heat Identify Areas Socially Vulnerable to Extreme Heat

July 11, 2023

Written by:

Benjamin Gurrentz and R. Chase Sawyer

Almost 1 in 4 people in the United States are socially vulnerable and have low resilience to extreme heat exposure, according to new U.S. Census Bureau data.

The Community Resilience Estimates (CRE) for Heat, an experimental data product released in April, measures the capacity of individuals and households in a community to withstand the stress of exposure to extreme heat based on their social characteristics.

When accounting for additional housing and transportation characteristics, more people in the United States are socially vulnerable or less resilient to rising heat temperatures.

The standard CRE measures social vulnerability that inhibits community resilience while the CRE for Heat adjusts certain risk factors like quality of housing, transportation modes and financial hardship to gauge social vulnerability specifically to extreme heat exposure.

The tool produces national, state, county and census tract (neighborhood equivalent) estimates using individual and household data from the 2019 American Community Survey (ACS) restricted microdata and the Census Bureau’s Population Estimates Program (PEP).

The experimental climate-focused data product was developed with Arizona State University’s Knowledge Exchange for Resilience (KER). The product was released at a joint Census Bureau-KER climate resilience symposium in Washington, D.C.

“This collaboration is an example of how we can leverage data and innovation to identify and address social inequalities and improve the resilience of communities in the face of climate change,” said Patricia Solís, KER’s executive director.

CRE for Heat Findings

CRE for Heat suggests greater social vulnerability and geographic variation compared to the standard CRE.

When measuring social vulnerability to heat exposure, the proportion of individuals with three or more risk factors increases from 21.6% in the standard CRE to 23.8% in CRE for Heat.

Similarly, the share with 0 risk factors decreases from 34.6% in the standard CRE to 31.7% in CRE for Heat.

In other words, when accounting for additional housing and transportation characteristics, more people in the United States are socially vulnerable or less resilient to rising heat temperatures.

Figure 1. Share of U.S. Population Socially Vulnerable to a Disaster, Extreme Heat: 2019

There were also differences in the number of areas flagged as statistically higher or lower than the national rate.

The CRE for Heat shows that 24.3% of counties have a greater proportion of individuals with three or more risk factors than the national rate — much higher than the 13.2% in the standard CRE.

Figure 2. Greater Share of U.S. Counties More/Less Vulnerable to Extreme Heat Than to Other Disasters?

At the same time, 4.6% of counties had a lower proportion of individuals with high risk (3+ risk factors) compared to the national rate, higher than the 1.8% in the standard CRE. This suggests the additional heat exposure risk factors produce greater distinctions across U.S. counties.

Figure 3. U.S. Counties More/Less Socially Vulnerable Than Nation to Extreme Heat: 2019

How CRE for Heat Came About

The first CRE was published as an experimental data product in June 2020 to provide information about the COVID-19 pandemic. It was also published to garner feedback from data users and stakeholders on the quality and usefulness of such a product.

KER reached out to the CRE team to further discuss the product and was particularly interested in how the CRE could be leveraged for measuring social vulnerability to heat exposure.

In consultation with KER, the CRE modified three of the 10 risk factors to adjust for social vulnerability to heat exposure.

While the standard CRE simply had a unit level crowding measure (0.75 people or more per room), CRE for heat has a housing-quality exposure indicator that also accounts for structure type or where people live (mobile home, boat, RV, or other).

Also, the original CRE has an indicator for no household vehicle but the CRE for Heat’s transportation exposure indicator also contains commute type (public transportation, walking, biking or other nonpersonal vehicle method).

Finally, while the CRE simply had a poverty indicator, the CRE for Heat’s financial hardship indicator also includes whether the household’s housing costs are greater than 50%.

Even though the number of risk factors didn’t change in the CRE for Heat, some characteristics or conditions like transportation modes were added. A person only needs to meet one of the conditions to receive a risk factor flag. For example, if a household does not have unit-level crowding but lives in a mobile home, it will be flagged for having a housing quality risk. If the household meets both conditions, it’s only flagged once.

Factors That Put Communities at Risk if Hit by a Disaster/Extreme Heat

It is important to note that CRE for Heat does not measure which areas are warmer than others or which areas are more likely to experience future heat waves. Instead, it identifies which areas exhibit low resilience if faced with extreme heat.

This new product comes with the same goals as the original CRE. Its publication should provide a new useful data source about a pressing topic and allow data users and stakeholders to provide feedback on potential enhancements.

Benjamin Gurrentz is a survey statistician in the Census Bureau’s Small Area Modeling and Development Branch – Social, Economic, and Housing Statistics Division.

R. Chase Sawyer is the technical lead for Modeled Data Product Development in Small Area and Longitudinal Estimates – Social, Economic, and Housing Statistics Division.