A pint-size heat wave last month smothered South Florida with temperatures that felt like 108 degrees, triggering rare heat advisories as humidity levels skyrocketed.
By the end of the century, the region could feel as many as 126 of those days if greenhouse gas emissions continue unabated, according to a study released this month by the Union of Concerned Scientists.
Even with rapid action to stymie global warming, areas from Miami-Dade to Martin County are expected to experience more than a month’s worth of days by 2099 where the heat index, or “feels like” temperature, tops 105.
And the southeast coast of the state isn’t even at the top of the misery measure when it comes to future high temperatures.
Collier and Monroe counties could feel nearly three months each year of 105 heat index days under global warming’s best case scenario.
“The type of heat we will experience in the future is above and beyond what Floridians are used to today,” said Kristy Dahl, senior climate scientist at the Massachusetts-based Union of Concerned Scientists. “If you look at the averages nationwide, Florida as a whole will have the highest number of days with heat indexes above 105 by late century if we do nothing.”
The study evaluates the number of high heat index days based on levels of greenhouse gas mitigation, including if the world meets the Paris Climate Accord standards that would limit future global warming to 3.6 degrees.
While catastrophic events such as hurricanes, floods, droughts and wildfires are being tied to a warming globe, the slow-motion increase in temperatures is something that can affect daily life “more than any other facet of climate change,” the report notes.
Florida Climatologist David Zierden, who reviewed the report, called it useful and said the science is sound.
“It’s all based on climate models,” he said. “It’s the best approach we have.”
Last month’s stifling temperatures were a nuisance to most Floridians who can escape to air conditioning, but they can be life threatening to field workers, roofers and landscapers.
Zierden noted that high school athletics will also be affected as more schools alter practice times to deal with extreme heat.
“I think the public has some idea of how increased heat is bad for the environment but they don’t understand how it affects health directly,” said Ankush Bansal, a Palm Beach County physician and co-chairman of Florida Clinicians for Climate Action. “That’s a bigger gap in the knowledge and a lot of physicians still don’t see the connection.”
Scott Lewis, who owns a West Palm Beach-based landscaping company, said hot days are a double-edge sword for his industry. The heat makes everything grow faster, which increases the workload and puts more stress on people working in the high temperatures.
“The most dangerous days for us are the ones where the normal summer afternoon thundershowers don’t show up to cool things down, and that seems to be happening more and more,” he said.
The heat index is a combination of the temperature and dew point temperature — a measure of the amount of water vapor in the air. Warmer air can hold more water vapor, which inhibits the ability of the body too cool itself because sweat doesn’t evaporate as efficiently as it does in drier air.
“We’re looking at preventative and adaptive strategies when we talk about mitigating greenhouse gas emissions,” said Megan Houston, Palm Beach County’s director of resilience. “Those are things like increasing tree canopy coverage and recommendations on roofing materials.”
Bill Johnson, Palm Beach County’s director of emergency operations, said while future temperature spikes are on his radar, he believes South Florida is better prepared to handle the heat in the short term because most homes have air conditioning.
Still, Dahl said extreme heat can force people to move to cooler areas, either because electricity costs get too high, their quality of life is degraded or, if they work outside, they can’t get enough hours to make a living.
In hotter months, air conditioners can run twice as long as they do in cooler months to keep a home at the same temperature, according to Florida Power & Light. It suggests people keep thermostats at 78 degrees or warmer, clean or replace filters, keep blinds closed and use ceiling fans to reduce cooling costs.
One issue not covered in the report is the warmer overnight temperatures that are increasing in Florida.
Zierden said June was the third warmest on record for the state if average temperatures were considered.
But it was “by far the hottest” on record based on overnight temperatures.
“For sure we are locked into some degree of warming at this point,” Zierden said. “It’s just that the action we take as a global community can reduce the adverse effects to the lesser degree.”
“The Invading Sea” is a collaboration of four South Florida media organizations — the South Florida Sun Sentinel, Miami Herald, Palm Beach Post and WLRN Public Media.