Last week, I came across a Morning Edition Story talking about the results of a study they conducted in partnership with Boston University about heat deaths across the country. They wondered whether the Centers for Disease Control was undercounting heat-related deaths in their published mortality data.
The reason they suspected this might be true is because heat can be a factor for other causes of death that get reported. For example, an abnormally hot day might induce a heart attack in someone. While their cause of death was the heart attack, we can say that had that person had better access to cooling resources, they would not have died from that heart attack.
It is similar to how we talk about the avoidable deaths from smoking. When we say that people die because of their cigarette smoking, we often attribute some other cause (cancer, heart disease, etc.) to their smoking behavior. Had that person not smoked, we suspect they would not have otherwise developed these fatal diseases.
This new research suggests that across the country as a whole, actual heat related deaths are as high as five times the reported figure by the CDC.
To come to this conclusion, the researchers developed a model which looked at weekly temperature data along with weekly mortality data at the county level. They measured the impact that unusually hot weeks (relative to a county’s average temperature to account for differences in acclimatization) impacted mortality rates at the county level. The article is light on specific modeling details, but they note that they intend to publish more detailed results in an academic journal in the near future.
This kind of approach was also used to measure the mortality impact of the COVID-19 pandemic. Researchers measured the number of excess deaths that occurred because of the pandemic relative to the number we would have expected under normal conditions.
One detail about this model that really highlights the scope of the problem is that there are some counties which actually report higher heat-related death counts than the model estimates. One example they highlight is Maricopa County Arizona, where Phoenix is.
Health officials in Maricopa County have made a concerted effort to better understand the impact that temperature has on local mortality rates. The result of their efforts is that they report more than double the number of heat related deaths than the model estimates.
This highlights the fact that these estimates are averages across the whole country. I’ve written before about the problems with point estimates, and while I expect the final results of this work to go into more detail about the variation in these estimates policymakers should be aware that their jurisdiction might not look exactly like these results.
Counties that have experienced the effects of climate change more harshly or those with more at-risk populations might experience even worse effects than those estimated in this report, while the inverse may be true for more stable or healthier counties.
Understanding the full range of heat-related impacts is important for policymakers and analysts because it will change the way we value certain impacts. If we believe that more people are dying because of their exposure to heat, then policies that work to reduce that exposure may end up saving more lives than we might otherwise expect. It can also impact our valuation of climate impacts. If heat is more deadly than we previously believed, then a hotter world is a more dangerous world for its residents.
