Greenhouse effect
Warming of the surface and lower atmosphere caused by gases that absorb and emit infrared radiation.
Example
The natural effect makes Earth habitable. Adding greenhouse gases changes the balance of incoming and outgoing energy.
The catch
The mechanism concerns heat radiation, not a literal glass roof.
Related terms
Greenhouse gas, Albedo, Atmospheric lifetime, Carbon budget, Carbon dioxide, Climate change
In more depth
Greenhouse effect, explained.
The greenhouse effect works because the atmosphere lets most incoming sunlight through but absorbs much of the infrared heat the surface sends back out. Greenhouse gases re-emit that heat in all directions. Energy finally escapes to space from higher, colder layers of air, and colder air radiates less.
Adding gas lifts that escape level higher, where it is colder still, so the planet sheds less energy than it receives. That imbalance is the radiative forcing behind current warming. Water vapour supplies the largest share of the natural effect, yet its amount follows temperature. It therefore acts as a climate feedback that amplifies changes started by carbon dioxide and other long-lived gases. The greenhouse effect is often confused with the ozone hole, a separate problem with different chemistry.