The climate of Earth is constantly changing. These changes affect everything that lives here, including humans and the natural world. Climate change is caused by increasing human-made emissions of heat-trapping greenhouse gases into the atmosphere. The emissions warm the planet, disrupting our usual weather patterns, and affecting our ecosystems and habitats.
Climate change is happening faster than ever before. It is already causing harm to wildlife and humans, and it threatens the services we all rely on, such as clean air, water, food production, and more. It can also cause dangerous conditions like wildfires and hurricanes.
Scientists agree that the global warming we are experiencing is caused by human activities, such as burning fossil fuels (coal, oil, and gas), deforestation, and agricultural and land-use changes. These activities increase the amount of ‘heat-trapping’ greenhouse gases in the atmosphere, mainly carbon dioxide. The warming that is occurring today has not occurred in thousands of years, and it cannot be explained by natural causes alone.
The most important factor in driving climate change is the concentration of carbon dioxide in the atmosphere. When coal, oil, and gas are burned, they release a large amount of carbon dioxide into the atmosphere. This carbon dioxide traps the sun’s heat, just as a greenhouse does, warming the planet. Scientists know that the CO2 in our atmosphere has increased since 1880 because the ratio of carbon isotopes — which shows where the carbon originated — has changed. This evidence proves that human-caused fossil fuel emissions have been the primary driver of climate change.
Continuing to emit greenhouse gases will lead to even greater increases in global temperature, and the impacts of this warming are being felt around the globe. The warming is already causing glaciers and ice sheets to melt, river and lake ice to break up earlier, and ocean temperatures to rise. These effects are expected to continue and intensify.
Human health is also at risk from climate change. For example, warmer temperatures mean more extreme weather events, such as heavy rainfall and flooding, which can negatively impact people’s health and wellbeing.
Warmer temperatures also mean more frequent and longer-lasting heat waves. These are particularly dangerous for some populations, such as children, pregnant women, and older adults, who are at higher risk of heat-related deaths.
In addition, climate change may make some types of diseases more likely. These include infectious and parasitic diseases transmitted by mosquitoes, which thrive in warmer environments. It is important to protect ourselves from these threats by avoiding exposure to harmful pollutants, such as particulate matter from wildfire smoke.
CDC is working to reduce the health risks of climate change, especially for vulnerable groups. Learn more about how the climate is affecting the health of our nation and what you can do to help. For more information about how climate change disproportionately affects some communities, visit CDC’s webpage on justice, equity, diversity and inclusion in climate adaptation planning. This site also provides resources to help communities plan for and respond to climate change.