Scientists Predict That Florida Will Have the Most Dangerous Heat Index in 30 Years

Climate scientists predict that low-lying coastal cities will experience destructive flooding from rising oceans as a result of climate change by mid century.  While that image of neighborhoods underwater is alarming, especially to Florida’s vulnerable coastal population, one of the most dangerous, but little talked about, effects of climate change will be the adverse effects on health from sharply rising temperatures. In the coming decades, soaring temperatures combined with Florida’s naturally high levels of humidity, will threaten the health of Floridians more than in any other state.

A recent article in Harvard Health Publishing explains that when the body’s temperature increases to 105 degrees, and there are no steps to reduce that elevated temperature, proteins around cells in the body, especially in the brain, are destroyed.  That can lead to neurological changes, “damage to internal organs, heart muscle cells, blood vessels and even death.”

The human body has a natural cooling system. When it’s hot outside, the body starts to perspire and when the perspiration on the skin evaporates, the body is cooled.  When the humidity is too high, evaporation of perspiration is reduced or eliminated and the body can’t regulate its own temperature.

In hot, dry states like Arizona and New Mexico, soaring temperatures, even hotter than Florida, are not as dangerous to health because drier conditions allow sweat to evaporate and the body to cool down. Not so in Florida’s hot, muggy climate. 

Scientists combine 2 factors, temperature and humidity, to calculate the “heat index” or “apparent temperature,” how hot the body actually feels. If the “heat index” exceeds 104 degrees, there is a real risk of heat stroke.  The most vulnerable are the young and old, but people of all ages are at risk, especially those who work outside such as in construction and on farms.

When the air temperature is 90 degrees and relative humidity at 70 percent, the heat index reaches the dangerous 105-degree level.  If the temperature is 86 degrees and the relative humidity is 90 percent, this critical danger zone is reached. And rising temperatures allow the air to hold more moisture. At 100 degrees and a relative humidity of 55 percent, the heat index is at a deadly level of 124 degrees.  

How much have global temperatures already increased from the emission of heat trapping greenhouse gases, mostly carbon dioxide, during the last century?   About 1.8 degrees, but this average global surface temperature includes the oceans that comprise 71% of the earth’s surface.  The continents as land masses heat more quickly than the oceans.  In the past half-century temperatures in the contiguous 48 states have increased an average of 2 degrees but there are significant regional variations.  According to Climate Central, the greatest increase in temperatures in the US since 1970 have been in Texas and the West.  During that period, Boise’s temperature increased by 5.3 degrees, Las Vegas by 5.3 degrees and McAllen, Texas by 5.1 degrees.  Burlington, Vermont saw an increase of 4.1 degrees since 1970 and Eerie, Pennsylvania by 4 degrees.  Florida’s average temperatures have increased by 2 degrees since 1970, less than a lot of other states. But Florida’s high humidity will create a much higher heat index than other states.

Because emissions of greenhouse gases are increasing at 1.5 percent a year, temperatures will continue to rise over decades and centuries. Emissions of carbon dioxide, the most potent greenhouse gas, rose twice as fast after 1970 than in the entire one hundred years before 1970.  There is more carbon dioxide in the atmosphere than anytime in the last two million years.  Carbon dioxide persists in the atmosphere for hundreds, even thousands of years.  If today all carbon emissions from human activity miraculously stopped, the existing carbon in the atmosphere that has accumulated since the 1800s  would continue to heat the planet for millennia, though not at a rate as fast as if emissions continue with business as usual. 

 How much do climate scientists predict that temperatures in the US will rise in the coming decades? By 2050 McAllen, Texas will experience 28 days out of the year with temperatures above 100 degrees.  Raleigh will have 23. Miami will have 46 days with temperatures over 100 degrees.  13 Florida cities are expected to see 100 plus temperatures days each year by 2050. 

Estimating the number of days that the heat index will exceed the dangerous heat index of 104 degrees by 2050, Florida’s cities dominate the list. This is not just from high temperatures, but the critical additional component of Florida’s high humidity.     

Topping Florida’s cities is Punta Gorda, on Florida’s Southwest coast, that will have 132 days per year with a dangerous heat index above 104 degrees by 2050. In second place is Miami-Ft. Lauderdale-Miami Beach that will see 128 days of the year above 104 degrees.  Tampa-St. Pete will have 119, Orlando 109 and Jacksonville, ninety-seven.  Sharing the high humidity along the Gulf, New Orleans will experience 95 days above 104 degrees. Valdosta, Georgia, will have 93 days a year of heat index above 104 degrees.

Climate change will bring many devastating effects during this century, including a significant reduction of agricultural production from extreme droughts and floods, to melting polar caps and rising seas. Many areas of the country will see sharply rising temperatures, but Florida will experience the twin evils of both flooded coasts and a very dangerous heat index.  

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