Climate variability refers to the fluctuations of climate above or below a long-term average.  It is not as noticeable as weather variability because climate variability happens over long periods of time, seasons or years instead of days.  We use these long-term averages to serve as a baseline to compare current weather and climate data, helping us situate current observations within a broader context. It is important to understand what is normal climate in order to understand current observations.

Climate change refers to longer-term changes in the climate or average weather conditions. Unlike climate variability, climate change is slow and gradual (e.g. changes over many decades). Climate variability is observable in the overall trends in climate change, as relatively more years are much hotter or than previous years.

Both climate variability and climate change can directly and indirectly impact human health.  For example, variations and changes in temperature directly impact the incidence of heat-related illness. Changes in vector habitats associated with climate variability and change indirectly impact human health, as the parameters of contact change between humans and the vectors for disease.

Climate influences health in the Carolinas in many different ways. For example:

  • Temperature
    • rising temperatures
    • Increases in heat-related illness
  • Extreme Weather Events
    • longer and more frequent heat waves
    • increased heavy rain and flooding
    • more severe impact on vulnerable populations
    • increased water-borne illness
  • Air Quality
    • deterioration of air quality
    • increased length and severity of allergy seasons
    • increases in respiratory illness
  • Changes in Vector Habitat
    • Increased length of warm seasons
    • Changes in precipitation regime
    • Expanded range of vector habitat
    • Increased cases of vector-borne disease

It is important to distinguish between people’s vulnerability versus exposure to climate events.  Often the severity of a climate impact depends upon both of these factors.  Vulnerability refers to the predisposition to suffer adverse effects when exposed to a climate event.  Vulnerability is rooted in many factors, such as social, economic, demographic, and geographic factors.  For example, an individual’s vulnerability to heat-related illness depends upon their acclimatization to the heat, their age, and weight, among other variables.  This vulnerability would not vary if they were exposed to the same level of heat in one location or another (a rural or an urban area, for example).

Exposure refers to the degree of contact with a climate event.  Increasing magnitude and frequency of extreme events, such as hurricanes or high heat days, increases an individual’s exposure thereby increasing the risk of adverse health effects. While exposure and vulnerability often work together to influence the impact of a climate event, it is not necessary to be both highly exposed and vulnerable to be impacted by a climate event.  For example, an otherwise healthy person exposed to high temperatures may suffer from heat-related illness even though he or she would not be considered “vulnerable.”.

Yes, the average annual temperature is increasing across the Carolinas when compared to historical climate conditions.  However, there will continue to be year-to-year fluctuations in temperature due to the natural variability in weather patters that affect the Carolinas. Some years may be relatively warmer or cooler than others, but the long-term trend indicates a steady rise in average annual temperature.  in addition, temperatures are not rising at an equal rate during all times of year. The greatest increases have been observed in the winter and summer seasons, while spring and fall have only seen a slight increase through time.
While extreme weather and climate events have always occurred across the Carolinas, there has been a pronounced uptick in these events during recent years.  As Earth’s average temperature continues to slowly increase, the global climate system (i.e., the atmosphere, oceans, ice caps) has begun to change in subtle, but very important, ways. These changes operating on the global scale also affect climate conditions on the regional-to-local scale, including the Carolinas. Perhaps the most noticeable impact across the Carolinas is the increase in days with unseasonably warm temperatures, particularly during the nighttime hours.  Heavy rainfall events are becoming more frequent because a warmer atmosphere, on average, can hold a greater amount of water vapor. Droughts and wildfire activity appear to be increasing in both frequency and intensity, as periods of little to no rainfall are more persistent under stagnant weather patterns.  Other events, such as tornado outbreaks and hurricanes, may also become more common and/or extreme in the future.
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