Rising Temperatures and Human Health

Growing up in Vermont, my family did not have an air conditioner. On the few hot and humid nights during the summer my parents would pull out the box fan. It was uncomfortable, but it never lasted very long before temperatures came back down. Most people I knew lived like this, and many still do. However, rising temperatures are making it more difficult to get through the summer months without cooling. From 1895 to 2015, the average annual temperature in Vermont increased by 2.6°F (or 0.2°F per decade). This change is actually most apparent in the winter months: winter (December-February) has experienced an increase of 0.64°F per decade, while summer temperatures have risen 0.15°F per decade.

Climate change is causing rising temperatures. The 10 warmest years on record have all occurred since 2005, and 7 of the 10 have occurred just since 2014. Temperature change is not happening evenly across the globe–the northeast region of the country is the fastest-warming area of the contiguous United States and is warming at a rate 50% greater than the global average. Vermonters are already feeling changes on the ground, and these changes are affecting our health. 

The heat index is a measure of how hot it really feels when relative humidity is factored into the actual air temperature. For example, if the air temperature is 90°F and the relative humidity is 65%, the heat index – how hot it feels – is 103°F. The National Oceanic and Atmospheric Administration’s (NOAA) heat index shows the likelihood of heat disorders with prolonged exposure and/or strenuous activity. Exposure to high temperatures, especially when combined with high humidity, limits the body’s ability to thermoregulate, or keep its internal temperature within healthy boundaries. When our bodies fail to thermoregulate, this causes heat-related illness including heat cramps, heat exhaustion, and heat stroke. Exposure to extreme heat can also amplify existing conditions.

Some populations are at greater risk of death from exposure to extreme heat, including the sick, elderly, disabled, homeless and displaced, children, and outdoor/manual laborers. Low-income people are also more at risk because they are often concentrated in urban heat islands, which occur when cities replace natural vegetation with concrete, pavement, buildings, and other surfaces that absorb heat. Low-income people are also less likely to be able to afford to an air conditioner or heat pump. In the US, it is well-documented that environmental burdens are overwhelmingly placed on low-income communities and communities of color. This means that risk of heat-related illness is a good example of an environmental justice issue, where low-income people and/or people of color are disproportionately at risk of climate-related ills.

Warmer weather does not only cause heat-related illness, but also increases the risk of a host of other health risks to humans. Ticks love warm weather, and climate change is making Vermont winters shorter and warmer. Ticks are not active when the temperature falls below freezing so, as winters warm, tick activity increases and the season when they are active lengthens. This means more opportunities for humans and other animals to come into contact with them. This warmer weather also means that mosquitos are active earlier in the spring and later into the fall. Warmer weather also causes waterbodies like lakes and ponds to become warmer and more stratified, meaning the shallower layers are much warmer and do not mix with cooler layers below. This causes cyanobacteria (blue-green algae) blooms, which release toxins harmful to humans and animals. 

When we think about climate change we often think about the possible future effects, which can make it easy to miss the effects of climate change that are already here in plain sight. Increased temperatures are one of those effects that we are all dealing with, and that will be more and more important in the coming decades. Temperature change is a dangerous reminder that we must act now on climate, or suffer the consequences.

The Heat Index shows how the ambient air temperature feels hotter with higher humidity.  (Credit: National Weather Service/National Oceanic and Atmospheric Administration)

What you can do:

  • Take measures to keep your home cool in summer, including weatherizing your home by adding insulation and making your home more energy efficient. This will help keep your home cool in the summer, since there will be more of a barrier to the heat.
  • Invest in shades for your windows, particularly for southern-facing windows. Blackout thermal shades are best, and can be used in the winter to keep heat in, but less-expensive alternatives will also help.
  • Consider switching your ac unit out for a heat pump. Heat pumps use electricity to cool and dehumidify in the summer and to heat the house in the winter. Heat pumps are much more efficient than air conditioners.


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