No one knows exactly how many people are dying from extreme heat
When officials in Miami-Dade County wanted to figure out how many people there were dying from extreme heat, they turned to Christopher Ueijo. A geographer at Florida State University, Ueijo used temperature data and death records to determine that, between 2015 and 2019, heat killed an average of 34 people a year in the county who wouldn’t have died otherwise. His estimate was more than 10 times higher than the official figures: Over the same time period, Miami-Dade had classified just two deaths as heat-related. About a year later, Ueijo did a second analysis of the same data, this time factoring in the buildup to heat waves’ peaks to capture more of their early and cumulative health impacts. The newer findings, published in May, were wildly different: 600 heat deaths per year. “They are both peer-reviewed studies,” says Jane Gilbert, the chief heat officer for Miami-Dade County who commissioned the two analyses. “I asked [Ueijo] which one I should use and he said it’s somewhere between 34 and 600.” In the space between two, 34 and 600 lies the central challenge of counting fatalities from heat. Officially this year, there have been 63 heat deaths in Thailand, at least 143 in India, at least 172 in Mexico, and more than 1,300 in a single week during the Hajj pilgrimage in Saudi Arabia. But unofficially, these numbers are a fraction of heat’s true toll. They are often the most obvious cases — those where doctors or coroners could confidently draw a line between heat and death — and are much less likely to account for fatalities in which temperatures played an indirect role. Some of this ambiguity has to do with the narrow way heat deaths are tracked, and some with the sheer number of health conditions exacerbated by rising temperatures. But the end result is the same: More people are dying from heat, while academics, medical professionals and government officials struggle to keep track. “Heat’s tricky,” says Este Geraghty, chief medical officer at ESRI, which produces mapping software used by researchers and government officials to track heat impacts. “It’s been called the silent killer, and for good reason.
