Greenhouse effect

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without this atmosphere. 

Diagram showing light energy (white arrows) emitted by the sun, warming the earth's surface which then emits the energy as heat (orange arrows), which warms the atmosphere and is then re-emitted as heat by three of the greenhouse gas molecules (water, carbon dioxide, and methane). image: wikipedia

Radiatively active gases (i.e., greenhouse gases) in a planet's atmosphere radiate energy in all directions. Part of this radiation is directed towards the surface, warming it. The intensity of the downward radiation – that is, the strength of the greenhouse effect – will depend on the atmosphere's temperature and on the amount of greenhouse gases that the atmosphere contains.

Earth’s natural greenhouse effect is critical to supporting life, and initially was a precursor to life moving out of the ocean onto land. Human activities, however, mainly the burning of fossil fuels and clearcutting of forests, have accelerated the greenhouse effect and caused global warming. 

The planet Venus experienced runaway greenhouse effect, resulting in an atmosphere which is 96% carbon dioxide, with surface atmospheric pressure roughly the same as found 900 m (3,000 ft) underwater on Earth. Venus may have had water oceans, but they would have boiled off as the mean surface temperature rose to 735 K (462 °C; 863 °F). 

The term "greenhouse effect" continues to see use in scientific circles and the media despite being a slight misnomer, as an atmosphere reduces radiative heat loss while a greenhouse blocks convective heat loss. The result, however, is an increase in temperature in both cases.

source adapted from: Wikipedia contributors. (2020, January 29). Greenhouse effect. In Wikipedia, The Free Encyclopedia. Retrieved 02:35, February 13, 2020, from https://en.wikipedia.org/w/index.php?title=Greenhouse_effect&oldid=938128321