Basic Information

Human Health
All living creatures depend on the ecosystem for health and well being. Earth has for millennia provided dependable sources of food, water, and other natural resources. Until recently, a relatively stable and predictable climate has provided the physical safety and comfort necessary for life to flourish. By changing the composition of the atmosphere, humans almost certainly impact the ecosystem's ability to support life as it now exists.

Scientists have only begun to study climate change impacts on human health, and many of the findings remain unclear.1 Scientists do know that some impacts will be beneficial. Milder winters, for example, could result in fewer deaths during the coldest months in temperate climates. In tropical and sub-tropical regions, extremely high temperatures could reduce the viability of disease-carrying mosquito populations.2

Overall, however, scientists believe climate change impacts on human health will be largely negative. Impacts will vary across regions, and communities already burdened by resource shortages, disease, and disability will face the most severe health impacts. Rural tribes that lack transportation and healthcare infrastructure, for example, will confront some of the most difficult challenges.

Health officials expect vector-borne diseases-those passed by insects, rodents, and other host carriers-to pose one of the biggest threats to human health.3 Disease-carrying mosquitoes require stagnant water and warm, human conditions to thrive-conditions that will be enhanced by warmer temperatures more-frequent storms. Rodents and ticks in temperate climates will proliferate after mild winters and spread illnesses such as Lyme disease and tick-borne encephalitis.4 Deadly hantavirus pulmonary syndrome could increase; carrier mice proliferate after both mild winters and heavy snowpack.5 Higher levels of spring runoff lead to increased food sources for mice. The 1993 hantavirus outbreak on the Navajo Reservation was linked to heavy snow and rainfall, which helped the rodent population expand to ten times its normal numbers.6 Under flooding conditions, increased rodent-human interactions are shown to increase rates of leptospirosis, tularaemia, and viral haemorrhagic disease.7

Annually, diarrhoeal diseases cause about 4% of all deaths and 5% of disabilities worldwide.8 This symptom of infection caused by a host of bacterial, viral, and parasitic organisms burgeons during both floods and droughts. Communities living without consistent access to clean water are especially vulnerable.

Extreme events such as heat waves and cold snaps may become more deadly as the climate shifts. Although varying by region, scientists predict an overall increase in heat related mortality as summertime temperatures increase.9 People with pre-existing conditions and the very young, old, or frail will be most at-risk. Scientists also expect an increase in deaths, disease and injury from other extreme events such as fires and hurricanes.10

A higher rate of crop failure will likely increase malnutrition, especially for children in developing countries. Regional famines may also swell. Extreme events could cause water shortages, leading to dehydration, decreased access to potable water, and a host of associated complications.11

Air quality will likely be degraded under climate change, especially in urban areas where greenhouse gas emissions are most intense. Concentrations of ground-level ozone, a primary component of urban smog, are rising in most areas. Forest fires and windblown dust from desertification will also negatively affect air quality. Also, studies have shown that allergies caused by pollen will worsen as the seasons warm.12

The changing climate may also result in the demoralization of entire communities as the land changes and resources grow scarce. Tribes, still dealing with the consequences Euro-American incursions into the Americas, will be forced once again to adapt to a changing world. Alaska Natives in coastal villages have already been forced to leave their ancestral homelands to relocate inland as sea levels rise. Traditional hunting practices are affected as sea ice becomes too unstable for travel and the timing of animal migration changes. The ranges of plants used for food, medicinal, spiritual, and other purposes are changing. Agricultural lifestyles will evolve as traditional foods can no longer be cultivated. Tribal cultural practices may become impossible to continue, and tribes will once again be forced to adapt to cultural practices and philosophies imposed on them largely by others.

For more information about climate change and human health, visit the World Health Organization's Climate Change and Human Health page at:

For more information on climate change and children's health, visit the U.S. Environmental Protection Agency's Create a New Climate for Action: Do Your Part for Climate Change and Children's Health page at:

  1. McMichael, A.J., et al. (2003). Climate change and human health: Risks and responses. Geneva, Switzerland: World Health Organization.

  2. Confalonieri, U., et al. (2007). Human health. In Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Parry, M.L., Canziani, O.F., Palutikof, J.P., van der Linden, P.J., & Hanson, C.E. (Eds.). Cambridge, UK: Cambridge University Press, 391-431.

  3. Githeko, A., Lindsay, S., Confalonieri, U. & Patz, J. (2000). Climate change and vector-borne diseases: a regional analysis. Bulletin of the World Health Organization, 78(9), pp. 1136-1148.

  4. McMichael, A.J., et al. (2003).

  5. McKenzie, J. (1997). Climate security and the national interest: The links among climate change, air pollution, and energy security. Washington, DC: World Resources Institute. Retrieved July 1, 2009 from

  6. Ibid.

  7. Confalonieri, U., et al. (2007).

  8. World Health Organization. (2009). Water related diseases. Retrieved July 1, 2009 from

  9. McMichael, A.J., et al. (2003).

  10. World Health Organization. (2005). Climate and health. Retrieved July 1, 2009 from

  11. Confalonieri, U., et al. (2007).

  12. Ibid.