How does the greenhouse effect work on Earth?

On Earth, solar radiation passes through the atmosphere and strikes the surface. As it is reflected back up, some solar radiation is trapped by gases in the atmosphere, including carbon dioxide, methane, chlorofluorocarbons (CFCs), and water vapor, resulting in the gradual increase of Earth's temperature. The rest of the radiation escapes back into space.

Human activity is largely responsible for the buildup of greenhouse gases in Earth's atmosphere, and hence Earth's gradual warming. For instance, the burning of fossil fuels (such as coal, oil, and natural gas) and forest fires add carbon dioxide to the atmosphere. Methane buildup comes from the use of pesticides and fertilizers in agriculture. Large amounts of water vapor are released from various industries. And CFCs are released by some aerosol cans and coolants in refrigerators and air conditioners.