The principle behind the greenhouse effect involves the trapping of heat in a planet's atmosphere. Solar radiation passes through the atmosphere, warming the Earth's surface. This heat is then re-radiated as infrared radiation, which is absorbed by greenhouse gases such as carbon dioxide and methane. These gases act like a blanket, preventing the heat from escaping back into space and consequently raising the Earth's average temperature. This effect is essential for maintaining life as it supports a stable climate, but excess greenhouse gases can lead to global warming and climate change.