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“Global temperatures and the frequency and intensity of heatwaves will rise in the 21st century” – World Health Organization


We all know that local risks to human health are broadly linked to climate – the risk of frostbite is greater in the Arctic than it is in Florida. In both cases, the regional climate is the cause. So it stands to reason that Florida’s rising temperatures may bring new or increased risks to human health. (No frostbite though.)

While human health is strongly influenced by environmental factors, with many processes interacting, climate changes are also coinciding with other major trends, such as urbanization and an aging population. This makes it difficult to isolate the relationship between climate change and specific health effects. However, we can project trends in human health that are linked to Florida’s warming climate.

Getting Hotter

The relationship between temperature and human health is well understood. The Florida Department of Health states unequivocally “Extreme heat events cause more deaths each year than hurricanes, lightning, tornadoes, earthquakes, and floods combined.” A major study estimated that the record hot summer of 2003 led to 70,000 premature deaths in Europe, primarily in large cities.

Senior citizens are particularly vulnerable to heat-related illnesses and death. Florida’s 65+ age group numbered 4.4 million in 2018, out of a total population of 21.3 million. Others at risk include young children, people with pre-existing conditions, outdoor workers and low-income households with little or no access to air conditioning.

The indirect health effects of climate warming are less obvious. Tossing and turning on really hot nights? Sleep disturbance is a risk factor for cardiovascular disease. Higher temperatures even have economic impacts through reduced worker productivity. A recent French report predicted that by 2050 climate warming would negatively affect the health and productivity of workers in the majority of business sectors.

It’s Not the Heat, It’s the Humidity

Florida residents know all too well that the air temperature is less important than the heat index – the compound effect of temperature and relative humidity on how hot it feels to you and me. To give you an idea of the magnitude of the effect – if the air temperature is 96 degrees, and the relative humidity is 65%, the heat index is 121 degrees. It gets worse – the heat index calculation assumes you are in the shade with a light breeze. Move into direct sun and the index can be as much as 15 degrees higher. The National Weather Service will issue an Extreme Heat Warning when the heat index is forecast to be 105 degrees or higher for at least two consecutive days.

How Bad Could It Get?

The answer is – really bad. A 2019 study by the Union of Concerned Scientists compared Florida’s historical record against climate warming temperature trends assuming a “business as usual” approach to greenhouse gas emissions. The results are startling:

  • Historically, Florida experienced an annual average of 125 days with a heat index over 90 degrees. Climate warming will drive the average to 166 days by 2050 and 186 days by 2100.
  • Up to now, Florida has recorded an average of 25 days per year with a heat index over 100 degrees. This will increase dramatically to an average of 105 days per year by 2050, and 141 by the end of the century.
  • By 2100, the study estimates that 17.6 million people will be exposed to a heat index above the National Weather Service 105 degree warning level for 30 days or more every year.

Is there a way out?

Yes and no. Much like Disney’s Sorcerer’s Apprentice, we have set in motion a climate changing process that will continue even if we stop greenhouse gas emissions completely tomorrow. So, we need to face the fact that warming will continue for decades, perhaps centuries, whatever we do.

However, international actions to reduce greenhouse gas emissions can have a positive effect, potentially limiting or even eliminating some of the worst impacts of climate warming. At the same time, we can take adaptation measures to protect vulnerable populations from dangerous temperature extremes.

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