Over millions of years, the Earth’s climate has always changed, naturally and gradually. Climate is the typical weather conditions in a region over a long time—30 years or more.

Scientists have been observing Earth for a long time. They use satellites and other instruments to collect many types of information about our land, atmosphere, ocean, and ice. This information tells us that Earth's climate is getting warmer.

The Earth is warming much faster now than it has over human history. Some human activities -- burning fossil fuels like coal for example -- upsets the balance of greenhouse gases in the atmosphere as they trap the Sun’s heat around the Earth. As a result, the global climate is becoming warmer.

Because of this warming, scientists expect more severe weather including heat waves, hurricanes, and drought. These weather events can harm health, damage natural resources, destroy homes, and affect how we live.

Climate change can affect more than weather patterns. It can affect crops, farm animals, wild plants and animals, and people’s health.

Climate change can also affect people through changes in the quality of air, water, and food. A drought can hurt crops and lead to food shortages or decrease the quality of food grown. It can increase the areas where disease-carrying insects can live and reproduce, which may lead to more disease outbreaks. Some people around the world may be forced to change where they live or how they earn a living because of long-time drought, increased flooding, or extreme temperatures.

NIEHS studies the effects of climate change on human health, and what they learn will help everyone make good decisions for the future.

Some content courtesy of the National Library of Medicine and NASA Climate Kids.