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Climate Change

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California Environmental Health Tracking Program

850 Marina Bay Pkwy, P-3
Richmond, CA 94804

(510) 620-3038
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Last Edited: 4/15/2014

Extreme Weather and Climate Change

As the climate changes, extreme weather events will occur more frequently.  Examples include droughts, which are caused by an extreme lack of precipitation, and floods, which are caused by an extreme abundance of precipitation.  These extreme weather events will impact health in many ways.  For example, changes in water runoff patterns will alter our food and water supplies.  In addition, changes in the weather and water runoff patterns will influence the spread of vector-borne diseases.  Floods can devastate our communities and result in drownings, infections, displacement from one's home, and long-lasting mental health effects.


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How does climate change affect extreme weather events?

Climate change is expected to increase both droughts and flooding.

  • Droughts
    • Droughts can occur during prolonged periods of extreme heat
    • Hardened and parched soils can also contribute to flooding
  • Floods
    • In recent decades, the occurrence of heavy downpours has increased and is expected to continue increasing as temperatures rise
    • Soil dryness, caused by drought and by earlier snowmelt due to rising temperatures, contributes to the risk of flash floods during heavy downpours, because dried soil cannot accept as much water as wet soil

While some areas of California may be experiencing extreme drought, others may be dealing with increased flooding.


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How do extreme weather events impact health?

Extreme weather can impact health in a variety of ways, including:

  • Food-borne illness
    • Changes in water runoff patterns can alter water quality significantly.  For example, floods and heavy rain cause land to erode, increasing the amount of pollutants that build up in the water.  As polluted water runoff enters coastal waters, the risk of contamination to shellfish increases.
    • Heavy rains and floods also contaminate water and food sources with chemicals and pathogens.  For example, a heavy downpour on a farm can displace feces from livestock into areas that contain food crops, including fruits and vegetables.  If these contaminated crops are sold and eaten, people may be at risk for food-borne illness.
  • Malnourishment or food insecurity
    • Severe drought can cause crops to fail, leading to the disruptions in our food supply.
  • Contaminated drinking water
    • Flood waters may contain industrial and household chemicals that can pollute drinking water supplies.  This could introduce contamination into our water systems. 
    • Floods may also disrupt or damage the infrastructure responsible for providing safe drinking water. 
  • Vector-borne diseases
    • Changes in the weather and water runoff patterns may influence the spread of vector-borne diseases
  • Injuries and drownings from floods
  • Mental health effects from devastation and displacement caused by floods

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Who will be most affected?

  • The elderly
  • Children
  • Immuno-compromised individuals
  • Individuals living in low-lying areas
  • Individuals living in poor or urban areas

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Resources on climate change and extreme weather events

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