A diagram of the greenhouse effect. Energy flows between space, the atmosphere, and Earth's surface. Energy exchanges are written in watts per square meter (W/m²).

Greenhouse gas reflects radiation that the Earth emits, preventing it from escaping into space. This occurrence is known as the "greenhouse effect".

Many greenhouse gases are natural, with water vapor being the most common and responsible for most of the greenhouse effect on Earth. Other significant greenhouse gases include carbon dioxide, methane, nitrous oxide, chlorofluorocarbon (CFCs) and ozone.