As our planet warms, we’re seeing an alarming rise in heat-related deaths in the U.S., according to a recent study that analyzed federal data dating back to 1999.
In 2023, more Americans succumbed to heat than in any other year recorded over the past two decades. This unfortunate milestone aligns with 2023 being the hottest year globally, a troubling sign of the ongoing impact of climate change.
The study, featured in the American Medical Association’s journal JAMA, found that 2,325 people died from heat-related causes in 2023. Researchers believe this number might actually be an undercount. Despite adjustments for an aging and growing U.S. population, the death toll remains alarming.
“The trajectory we’re on with warming and climate change is beginning to manifest in higher death rates,” said Jeffrey Howard, a public health associate professor at the University of Texas at San Antonio and lead author of the study. “This increase is something we hadn’t measured before.”
Howard, along with colleagues from the Uniformed Services University of the Health Sciences in Maryland and Pennsylvania State University, examined death certificates from 1999 to 2023, noting when heat was listed as a primary or contributing cause of death.
Deaths remained relatively stable until around 2016, when the number began to climb, resembling a “hockey stick” trend. This term has often been used to describe rapid, alarming increases in global temperatures.
According to the research, human fatalities seem to follow this worrying trend. The key indicator is the age-adjusted death rate per 100,000 people. This rate has dramatically increased from the early 2000s, across all ages and population sizes.
In 2022, the adjusted death rate was 0.47 with 1,722 deaths. The following year saw 603 additional deaths, raising the adjusted rate to 0.63 – the highest ever recorded.
However, deaths weren’t evenly distributed across the nation. Howard noted that most occurred in traditionally hot states like Arizona, California, Nevada, and Texas.
The study’s limitations highlight variations in how local governments classify heat-related deaths, possibly leading to an undercount. Increased awareness about heat’s fatal risks could also skew numbers. The study didn’t specify vulnerable groups like those without air conditioning, outdoor workers, and people with underlying health issues, all of whom face higher risks of heat-related illnesses or death.
“Heat is often termed the silent killer,” said Sameed Khatana, an assistant professor of medicine at the University of Pennsylvania and cardiologist at the Philadelphia VA Medical Center, who specializes in heat death reporting.
Khatana pointed out that officials are becoming more aware of heat factors when documenting deaths. “There’s growing recognition of nuances highlighted in research over the past few decades,” he said.
Researchers, including Khatana, have previously advocated for better methods of reporting heat deaths.
Ashley Ward, director of the Heat Policy Innovation Hub at Duke University, stressed the need for uniform standards in recognizing heat as a contributing factor in deaths. “Counties across the country handle this differently. We need guidelines for determining when heat plays a role.”
The researchers in the latest study urged local officials to consider expanding access to cooling centers, hydration stations, and air-conditioned buildings.
In 2024, summer temperatures continue to soar. While it’s too soon to compare death tolls, the recent heat waves across the U.S. are concerning.
For instance, Phoenix recently set a record for the most consecutive days above 100 degrees. Mark O’Malley, a meteorologist at the National Weather Service in Phoenix, noted that Sunday marked the 91st day in a row with temperatures exceeding 100 degrees at Sky Harbor Airport.
This past July was the warmest on record in California and New Hampshire, and among the top 10 warmest in 19 other states, reports the National Oceanic and Atmospheric Administration (NOAA).
Globally, three consecutive days in late July were the hottest ever recorded, surpassing previous records set in the same month last year. According to NOAA, there’s a 77% chance this year will be the warmest on record.
“Overall,” Howard said, “it seems like things are worsening rather than improving.”
