The more socially vulnerable a community is, the less resistance its residents have to extreme heat exposure.
Using Hamilton County as an example, that would be the unsurprising conclusion from information in a new U.S. Census Bureau tool, Community Resilience Estimates for Heat, an experimental data product the agency released in April.
We say "unsurprising" because if a community is socially vulnerable, its residents already may be dealing with hardships in housing, food, transportation and finances, most of which lead directly to the potential for low resistance to extreme heat exposure.
We suspect the Census Bureau release is another way for the federal government to warn us about what it believes are the perils of climate change, but the information graciously did not include that overused term.
But to narrow the findings, the data show that Hamilton County has a greater percentage of people with three or more risk factors for low resilience to heat exposure than the other three counties in Tennessee with a similar population.
Here, 23.22% of people have three or more risk factors, while 21.31% of Knox County residents, 19.67% of Montgomery County (Clarksville) residents and 18.08% of Rutherford County (Murfreesboro) residents do.
Among the state's two other most populous counties, Hamilton comes in behind Shelby County (27% with residents with three or more risk factors) but in front of Davidson County (22.49%).
Narrowing the data further, the most vulnerable Hamilton County census tract for extreme heat exposure is East Lake, where 50.74% of its residents have three or more risk factors.
Behind East Lake, in order, are census tracts roughly encompassing Bushtown/Orchard Knob, Southside, Alton Park, Glenwood, Eastdale, Westside, North Brainerd, East Ridge (roughly between North Moore Road and Interstate 75) and North Hixson (near the Sequoyah Nuclear Plant).
With the exception of North Hixson, the other census tracts have a majority of Black or Hispanic residents or a large number of them. And in most, the poverty rate and median household income are significantly below the average in Chattanooga.
For instance, in East Lake, the most vulnerable county census tract for extreme heat exposure, the poverty rate of 47.4% is more than double the 17.6% rate for Chattanooga, and the median household income of $26,705 is about half the $50,437 amount in Chattanooga. In educational attainment, 65.7% are high school graduates, about three-quarters of the 89% rate in Chattanooga.
As to the county census tracts where risk for extreme heat exposure is lowest, they're not necessarily the areas where the median household income is the highest.
The tract with the highest percentage of residents with no risk factors is Walden on Signal Mountain (62.34% have no risk factors for extreme heat exposure), followed by Lakesite, Riverview, Harrison Point on Lake Chickamauga, Red Bank/Hixson, Snowhill, Lookout Mountain and Middle Valley.
In the Walden area census tract where the biggest percentage of people have the fewest risk factors, the median individual income is nearly $45,000, and the poverty rate is about 3.5%.
In other words, most of the people with no risk factors likely have access to good medical care, have no or few transportation problems, have a secure roof over their heads and have the financial wherewithal to cool the area under that roof.
The Census Bureau report, on the United States as a whole, says nearly one in four people are socially vulnerable and have low resilience to extreme heat exposure.
The data, it says, was developed with Arizona State University's Knowledge Exchange for Resilience, which brings community and academic researchers together to share insights, discover opportunities, and implement solutions for social, economic and environmental resilience.
What the Census Bureau release does not say, but which the data provide, is the margin for error in the measurements for resilience to heat exposure.
While we're used to the margin of error for, say, presidential polls being around plus or minus 3%, the margin of error for the resilience estimates in Hamilton County ranges from 9.44% to 13.1%. So, in essence, almost all of the estimates could be off a tenth. When discussing climate science, and potential decision-making over such science, that's a lot.
Indeed, the Census Bureau does refer to the data tool as "experimental" and warns that it "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."
Still, parts of the United States have experienced record heat this summer, while others haven't. Chattanooga, for instance, for the period from March through June, was about 1.7 degrees below normal.
Fortunately, the Census Bureau heat estimates show what those who deal with the poor and marginalized on a daily basis already understand — if they lack housing, transportation and financial means, they're also likely to be vulnerable to extreme heat.