Since 1900, the average temperature on Earth has risen by about 2 degrees Fahrenheit. Most of the increase has occurred over the past 50 years, and temperatures are continuing to rise sharply. Without intervention to slow the pace of climate change, temperatures are on track to increase by an additional 7 degrees F by the year 2100 (NASEM, 2025).
This warming trend is driven in large part by the combustion of fossil fuels—coal, oil, and natural gas—which account for over 75% of all greenhouse gas (GHG) emissions. These emissions form a heat-trapping “blanket” in the Earth’s atmosphere, causing global temperatures to rise at unprecedented rates (UN, 2025). This is rapidly changing the environment in ways that affect human health.
Major climate change hazards currently affecting people’s health in the United States include air pollution, vector-borne and fungal diseases; extreme weather; wildfires; and extreme heat. These threats affect different populations differently depending on exposure and vulnerability.
Several of these hazards may be experienced at once, increasing the severity of outcomes. Hazards affect people differently but can exacerbate underlying medical conditions for many. Some health impacts may be acute, such as heat illness from extreme temperatures or asthma events from nearby wildfire smoke. Other impacts may be more chronic, such as mental health conditions. Extreme weather events, including floods, droughts, and storms, can cause injury, death, or displacement; impact employment; disrupt access to health care; and result in long-term physical and mental impacts. Health hazards are expected to increase in coming years in frequency, intensity, and extent.
The tables below contain key facts about the health impacts of five major climate change hazards affecting health in the United States today.