Global warming will cause ‘extreme heat belt’ in US, study warns

Note: Shaded counties are those that will have, on average, 0.5 days or more at or above a 125 F° heat index in 2053; Data: First Street Foundation; Map: Axios Visuals

A new study reveals the emergence of an “extreme heat belt” from Texas to Illinois, where the heat index could reach 125°F at least one day a year by 2053.

The big picture: In just 30 years, climate change will make the lower 48 states a much hotter and more precarious place during the summer.

  • The findings come from a hyperlocal analysis of current and future extreme heat events released by the nonprofit on Monday. First Street Foundation.
  • The new report is unique in examining current and future heat risks down to the property level across the country, and joins similar risk analyzes First Street has ended for flooding and wildfires.
  • As average temperatures increase due to human-made greenhouse gas emissions, primarily from the burning of fossil fuels for energy, extreme heat events are expected to increase.
  • This report makes it clear where households will be vulnerable to what would now be considered almost unknown heat indices, which show how the air feels from the combination of air temperature and relative humidity.

Threat level: The report, which is based on First Street’s peer-reviewed thermal modelshows that the number of Americans currently exposed to “extreme heat,” defined as having a maximum heat index greater than 125°F, is just 8 million.

  • However, due to projected warming over the next three decades, that number is expected to jump to 107 million people, a 13-fold increase over 30 years.
  • The developing “extreme heat belt” forms a region of vulnerability from northern Texas to Illinois and includes the cities of St. Louis, Kansas City, Memphis, Tulsa and Chicago.
  • By 2030, some coastal areas in the southeast and mid-Atlantic could also experience days with a heat index above 125°F, the report said.

Enlarge: The report shows a country that will face the effects of increased heat exposure almost everywhere, although there are distinctions based on geography.

  • For example, the study finds that in 2053, the West will have the greatest chance of long durations with “local hot days,” which are days that exceed the temperatures typically experienced for a particular area.
  • The Gulf and Southeast will see the highest risk and longest duration of exposure to so-called “hazardous days,” with a heat index above 100°F, according to the report.

Between the lines: The states likely to see the strongest growth in dangerous days are Texas, Louisiana, Arkansas, Missouri and Florida, according to First Street’s analysis.

  • The counties with the greatest changes in dangerous days between 2023 and 2053 are primarily located in Florida, led by the populated areas of Miami-Dade, Broward, and Palm Beach counties.

  • The report shows how the characteristics of heat waves could change in the near future. Many spots are currently seeing more than 20 consecutive days with heat indices above 100°F. However, by 2053, these streaks could reach 74 consecutive days, the report says.
  • The study also sheds light on the demand for cooling induced by increasingly hot conditions, including cooling-induced increased carbon emissions, which would further exacerbate warming.
  • And Texas, Florida, California, Ohio and Missouri make up the top 5 states with the largest increase in cooling demand-related CO2 emissions by 2053, according to the report.

Meanwhile… The United States is already seeing the clear fingerprints of human-caused global warming on extreme heat events. Last month, for example, the country’s overnight lows were the hottest on record for a month.

  • Unusually warm nighttime temperatures during heat waves increase the public health risk of heat-related illnesses.
  • Additionally, the number of hot temperature records exceeded the number of cold temperature records by a ratio of almost eight to one.

And after: Communities are innovating to reduce the impacts of oppressive heat and implementing better heat action plans, among other climate resilience measures.

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Teresa H. Sadler