Solar radiation from the sun passes through the Earth’s atmosphere largely in the form of visible light. That sunlight heats the Earth, and much of that heat radiates back out towards space in the form of thermal energy. Unlike visible light waves, which pass through the atmosphere largely undisturbed, much of the thermal energy radiating back toward space is absorbed by the Earth’s atmosphere.
This trapping of thermal radiation or heat in the Earth’s atmosphere is called the greenhouse effect. The greenhouse effect makes Earth habitable for humans. If Earth’s atmosphere didn’t trap heat, the planet would be much colder—too cold to sustain human life. Water vapor in the Earth’s atmosphere is a leading cause of the greenhouse effect. “Greenhouse gases,” pollutants including carbon dioxide and methane, trap additional heat. The more these gases build up in the Earth’s atmosphere, the hotter it gets.
“The natural greenhouse effect is vital to supporting life on Earth but like anything, too much of a good thing causes problems,” said Drew Shindell, an earth science professor at Duke University.
— Phil McKenna