Hot weather is poised to kill many more Americans every year if current trends hold, recent research suggests. It estimates that the U.S. could see 200,000 temperature-related deaths annually by the end of the century in a bad but possible climate scenario—about five times the number of deaths seen today. We might still be able to significantly reduce the death toll by making cities more heat-adapted, though, particularly in the Northern U.S.
The study was conducted by researchers at Texas A&M University and the University of Illinois at Chicago, and published last month in the journal GeoHealth. Based on data collected from over 100 middle-to-large cities, the authors created models for what could happen to temperature-related deaths in the U.S. under a variety of different climate projections. They focused primarily on a future where global average warming reached 3 degrees Celsius above pre-industrial levels by 2100: a not-quite-worst-case scenario that we might be on track to meet without aggressive actions to limit greenhouse gas emissions or other drastic solutions.
In the U.S. nowadays, most temperature-related deaths are caused by exposure to the cold, not the heat. So it’s likely that some deaths would be prevented by generally warmer winters and offset the increased deaths caused by hotter summers, at least up until a certain point. The authors estimated that this turning point would be reached in a future where the world became 3 degrees Celsius hotter. After that, the number of added deaths would depend on how well people and cities adapted to the climate.
During the last decade, there were about 45,800 temperature-related deaths annually in the U.S. between 2011 and 2020, the authors found. In a scenario where the world became 3 degrees Celsius hotter and there was little adaptation in response, about 200,000 temperature-related deaths would happen every year, they predicted.
Most of this projected increase is tied to a growing and aging population, the authors calculated, rather than the direct effects of climate change alone (elderly people, in particular, are much more vulnerable to extreme heat). However, climate change will dramatically alter the way that many cities experience the seasons. In southern states where summer temperatures are already very high, many areas have plenty of infrastructure to help people cool off, such as air-conditioning. But as these same temperatures become commonplace in the Northern U.S., poorly prepared cities are expected to see many more deaths, the authors say.
“We find that in the future, temperature-related deaths are going to increase in the northern U.S., mostly due to an increase in heat-related deaths,” said lead author Jangho Lee, a climate scientist at the University of Illinois at Chicago, in a statement provided to the American Geophysical Union, publishers of the study. “That’s because southern cities, like Phoenix or Houston, are already very well adapted to heat, whereas northern cities are not.”
Even with a growing and older U.S. population, a large chunk of these deaths are still preventable under a 3-degree Celsius future, the authors note. They estimated that about 28% of deaths could be averted if Northern cities became as well-adapted as those in the South by 2100 (amounting to 144,000 deaths total a year). Of course, that’s a goal much easier said than done.
“Ultimately, no one knows how effectively we will adapt to the warmer temperatures of the coming century. However, the investments society has made to make cities like Houston or Phoenix livable in a hot climate are massive and it is far from assured that we will make similar investments in other cities as the climate warms,” the authors wrote.