We often hear about how global climate change is impacting the environment—for example, how rising average temperatures and changes in weather patterns are impacting coastlines and agriculture—but the health effects of climate change are less often discussed. However, there is no doubt that environmental exposures affect a person's health, and therefore a changing climate will mean both direct and indirect health consequences.

Human health can be affected directly by weather and climate. For example, extreme heat can cause heat exhaustion or heat stroke, and severe storms, such as hurricanes or tornadoes, can cause injury or death. However, the environmental consequences of climate change will also have a wide range of indirect effects on human health.

Vectorborne and zoonotic diseases (VBZD) are diseases that can be transmitted from animals to humans, either by vectors (such as mosquitoes or ticks) or by contact with infected animals. Environmental factors such as temperature, precipitation, humidity, vegetation, and predators affect the animal vectors and hosts of VBZD, thereby influencing the range and incidence of the diseases. As ecosystems are altered by climate change, VBZD patterns will change as well. For example, diseases such as malaria and dengue fever that were limited to tropical areas may expand in range, as previously cooler regions become more suitable habitats for the vectors that transmit them. The movement of people and changes in agriculture can also play a role in changes in the distribution of VBZD.

Climate change will also increase human exposure to contaminants that can affect development, such as those that damage the nervous or hormonal systems. In particular, harmful chemicals in storage or hazardous waste sites can be released by flooding from rising sea levels and extreme weather events. Melting ice sheets and warmer temperatures that expand ocean water are already causing sea levels to rise, and there have been trends of more extreme weather events and unusually high rainfall in some areas. During the 2010 floods in Pakistan, the powerful force of floods destroyed storage areas and released into the environment large amounts of chemicals, including pesticides that had been stockpiled in low-lying areas.

As people continue to study the potential effects of climate change and learn from disasters such as the floods in Pakistan, they are becoming better equipped to protect public health. Strategies such as limiting breeding grounds for mosquitoes, developing better health monitoring systems, and reducing production of harmful chemicals can help safeguard human health. In addition, overpopulation has been recognized as a serious environmental problem that is tied to climate change. If there were fewer people, there would be less pollution and less climate change. Scientists and policy-makers alike are working to find ways to help humans sustainably inhabit the planet.

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