Health Impacts of Climate Change

Climate change refers to a broad range of long-term changes in average weather patterns that have come to define Earth’s local, regional and global climates. These include shifts in heat waves, droughts, floods and wildfires; rising sea levels; and increased air pollution. Climate change is caused by humans and is expected to worsen unless action is taken.

Temperature changes, whether warming or cooling, are the most visible and measurable aspect of climate change. However, other impacts are also becoming apparent. For example, changes in ocean acidity can alter marine life while rising sea levels can affect coastal communities by putting them at risk of storm surges, high tides and flooding.

Many of these effects are linked to human activities, including burning fossil fuels for energy and land clearing. These emissions release carbon dioxide and other greenhouse gases into the atmosphere, causing temperatures to rise. The climate system is extremely complicated, and natural factors like solar output, volcanic activity and wind patterns have affected temperatures in the past. But the current rate of warming is unequivocally a result of human activity.

The ocean — the planet’s biggest absorber of energy — is responding to climate change by warming, becoming more acidic and losing salt. The water is also expanding, which is pushing sea levels higher. These changes have already had major impacts on people.

Heat waves, droughts, wildfires and heavy rainfall are more frequent and intense as Earth’s climate warms. These events can increase the spread of infectious diseases like malaria and foodborne illnesses that result from contaminated water. As the climate changes, the geographic distribution of “vector” organisms — such as mosquitoes — that transmit these diseases from person to person, may also shift.

Climate change threatens the health of all humans — but certain populations are at greater risk than others. This includes older adults, those with chronic diseases and mobility challenges, those living in rural areas, indigenous populations, Black and other people of color, low-income countries and communities, and women and girls. They are more likely to experience the health impacts of climate change due to their heightened physiological sensitivities, greater exposures and limited capacity to take protective actions. They are also at greater risk of the economic costs and inequalities resulting from climate change. Taking effective action to mitigate climate change will require explicit attention to the social determinants of health and how they shape conditions for people around the world to thrive.

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