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The Link Between Climate Change and Human Health: Understanding the Risks


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In 1998, Hurricane Mitch dropped six feet of rain on Central America in three days. In its wake, the incidence of malaria, dengue fever, cholera, and leptospirosis soared. In 2000, rain and three cyclonesinundated Mozambique for six weeks, and the incidence of malaria rose fivefold. In 2003, a summer heat wave in Europe killed tens of thousands of people, wilted crops, set forests ablaze, and melted 10 percent of the Alpine glacial mass.

This summer’s blistering heat wave was unprecedented with regard to intensity, duration, and geographic extent. More than 200 U.S. cities registered new record high temperatures. In Phoenix, Arizona, sustained temperatures above 100°F (38°C) for 39 consecutive days, including a week above 110°F (43°C), took a harsh toll on the homeless. Then came Hurricane Katrina, gathering steam from the heated Gulf of Mexico and causing devastation in coastal communities. These sorts of extreme weather events reflect massive and ongoing changes in our climate to which biologic systems on all continents are reacting. So concluded the United Nations Intergovernmental Panel on Climate Change,1 a collaboration of more than 2000 scientists from 100 countries. In 2001, the panel concluded that humans are playing a major role in causing these changes, largely through deforestation and the combustion of fossil fuels that produce heat-trapping gases such as carbon dioxide.

Food and Water Insecurity

Changes in temperature and rainfall patterns are also impacting food and water security. Droughts and heat waves can lead to crop failures and food shortages, while floods and storms can contaminate water supplies. These changes can lead to malnutrition, dehydration, and the spread of waterborne illnesses.

Vector-borne Diseases

Climate change is also increasing the risk of vector-borne diseases, like malaria and dengue fever. As temperatures rise, the geographic range of disease-carrying insects expands, and these insects are able to survive in new areas. In addition, changing rainfall patterns can create new breeding sites for mosquitoes and other disease vectors. These diseases can cause serious health problems, and are particularly dangerous for children and pregnant women.

Mental Health

Finally, climate change is taking a toll on our mental health. The stress and anxiety of living with the threat of extreme weather events, food and water insecurity, and other climate-related risks can lead to depression, post-traumatic stress disorder (PTSD), and other mental health problems. In addition, the loss of homes, communities, and cultural traditions due to climate change can be deeply traumatic.


Climate change is a complex and urgent problem that requires immediate action. By understanding the ways in which climate change impacts human health, we can work together to protect ourselves and our communities. This may involve reducing our greenhouse gas emissions, developing new technologies to adapt to a changing climate, and strengthening our healthcare systems to better respond to climate-related health risks. Ultimately, it will take a global effort to address this issue and protect the health and wellbeing of people around the world.

Aaron Bernstein, MD, MPH

Aaron Bernstein is the Interim Director of The Center for Climate, Health, and the Global Environment, a pediatrician at Boston Children’s Hospital, and an Assistant Professor of Pediatrics.

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