Greenhouse effect

This article is about the atmospheric phenomenon causing planetary warming. For the general heating or cooling of Earth's surface, see Earth's energy budget. For other uses, see Greenhouse (disambiguation).

Energy flows down from the sun and up from the Earth and its atmosphere. When greenhouse gases absorb radiation emitted by Earth's surface, they prevent that radiation from escaping into space, causing surface temperatures to rise by about 33 °C (59 °F).

The greenhouse effect occurs when greenhouse gases in a planet's atmosphere insulate the planet from losing heat to space, raising its surface temperature. Surface heating can happen from an internal heat source as in the case of Jupiter, or from its host star as in the case of the Earth. In the case of Earth, the Sun emits shortwave radiation (sunlight) that passes through greenhouse gases to heat the Earth's surface. In response, the Earth's surface emits longwave radiation that is mostly absorbed by greenhouse gases. The absorption of longwave radiation prevents it from reaching space, reducing the rate at which the Earth can cool off.

Without the greenhouse effect, the Earth's average surface temperature would be as cold as −18 °C (−0.4 °F).[1][2] This is of course much less than the 20th century average of about 14 °C (57 °F).[3][4] In addition to naturally present greenhouse gases, burning of fossil fuels has increased amounts of carbon dioxide and methane in the atmosphere.[5][6] As a result, global warming of about 1.2 °C (2.2 °F) has occurred since the Industrial Revolution,[7] with the global average surface temperature increasing at a rate of 0.18 °C (0.32 °F) per decade since 1981.[8]

All objects with a temperature above absolute zero emit thermal radiation. The wavelengths of thermal radiation emitted by the Sun and Earth differ because their surface temperatures are different. The Sun has a surface temperature of 5,500 °C (9,900 °F), so it emits most of its energy as shortwave radiation in near-infrared and visible wavelengths (as sunlight). In contrast, Earth's surface has a much lower temperature, so it emits longwave radiation at mid- and far-infrared wavelengths.[6] A gas is a greenhouse gas if it absorbs longwave radiation. Earth's atmosphere absorbs only 23% of incoming shortwave radiation, but absorbs 90% of the longwave radiation emitted by the surface,[9] thus accumulating energy and warming the Earth's surface.

The existence of the greenhouse effect, while not named as such, was proposed as early as 1824 by Joseph Fourier.[10] The argument and the evidence were further strengthened by Claude Pouillet in 1827 and 1838. In 1856 Eunice Newton Foote demonstrated that the warming effect of the sun is greater for air with water vapour than for dry air, and the effect is even greater with carbon dioxide.[11][12] The term greenhouse was first applied to this phenomenon by Nils Gustaf Ekholm in 1901.[13][14]

  1. ^ "Solar Radiation and the Earth's Energy Balance". The Climate System – EESC 2100 Spring 2007. Columbia University. Archived from the original on 4 November 2004. Retrieved 15 October 2010.
  2. ^ Le Treut H, Somerville R, Cubasch U, Ding Y, Mauritzen C, Mokssit A, Peterson T, Prather M (2007). "Historical Overview of Climate Change Science" (PDF). In Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL (eds.). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK and New York, NY: Cambridge University Press. p. 97. Archived from the original (PDF) on 26 November 2018. Retrieved 25 March 2014.
  3. ^ "The Elusive Absolute Surface Air Temperature (SAT)". Goddard Institute for Space Studies. NOAA. Archived from the original on 5 September 2015. Retrieved 3 September 2008.
  4. ^ "Yearly average temperature". Climate Change Tracker.
  5. ^ Cite error: The named reference ipcc-AR4WG1 was invoked but never defined (see the help page).
  6. ^ a b Rebecca, Lindsey (14 January 2009). "Climate and Earth's Energy Budget : Feature Articles". earthobservatory.nasa.gov. Archived from the original on 21 January 2021. Retrieved 14 December 2020.
  7. ^ Fox, Alex. "Atmospheric Carbon Dioxide Reaches New High Despite Pandemic Emissions Reduction". Smithsonian Magazine. Archived from the original on 10 June 2021. Retrieved 22 June 2021.
  8. ^ Lindsey, Rebecca; Dahlman, Luann. "Climate Change: Global Temperature". NOAA Climate.gov.
  9. ^ "What is Earth's Energy Budget? Five Questions with a Guy Who Knows". NASA.gov. 10 April 2017. Retrieved 24 April 2023.
  10. ^ Fourier, J. (1824). "Remarques Generales sur les Temperatures Du Globe Terrestre et des Espaces Planetaires". Annales de Chimie et de Physique (in French). 27: 136–167. Archived from the original on 2 August 2020. Retrieved 8 June 2020.
  11. ^ Foote, Eunice (November 1856). Circumstances affecting the Heat of the Sun's Rays. Vol. 22. pp. 382–383. Archived from the original on 30 September 2020. Retrieved 31 January 2016. {{cite book}}: |work= ignored (help)
  12. ^ Huddleston, Amara (17 July 2019). "Happy 200th birthday to Eunice Foote, hidden climate science pioneer". NOAA Climate.gov. Archived from the original on 30 September 2020. Retrieved 8 October 2019.
  13. ^ Easterbrook, Steve (18 August 2015). "Who first coined the term "Greenhouse Effect"?". Serendipity. Archived from the original on 13 November 2015. Retrieved 11 November 2015.
  14. ^ Ekholm N (1901). "On The Variations Of The Climate Of The Geological And Historical Past And Their Causes". Quarterly Journal of the Royal Meteorological Society. 27 (117): 1–62. Bibcode:1901QJRMS..27....1E. doi:10.1002/qj.49702711702.