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Greenhouse gases[edit]

Greenhouse effect schematic showing energy flows between space, the atmosphere, and earth's surface. Energy exchanges are expressed in watts per square meter (W/m2).
This graph is known as the "Keeling Curve" and it shows the long-term increase of atmospheric carbon dioxide (CO2) concentrations from 1958-2008. Monthly CO2 measurements display seasonal oscillations in an upward trend; each year's maximum occurs during the Northern Hemisphere's late spring, and declines during its growing season as plants remove some atmospheric CO2.

The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface. It was proposed by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896.[1]

Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F).[2][C] The major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect; carbon dioxide (CO2), which causes 9–26 percent; methane (CH4), which causes 4–9 percent; and ozone (O3), which causes 3–7 percent.[3][4][5] Clouds also affect the radiation balance, but they are composed of liquid water or ice and so have different effects on radiation from water vapor.

Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO2, methane, tropospheric ozone, CFCs and nitrous oxide. The concentrations of CO2 and methane have increased by 36% and 148% respectively since 1750.[6] These levels are much higher than at any time during the last 800,000 years, the period for which reliable data has been extracted from ice cores.[7][8][9][10] Less direct geological evidence indicates that CO2 values higher than this were last seen about 20 million years ago.[11] Fossil fuel burning has produced about three-quarters of the increase in CO2 from human activity over the past 20 years. The rest of this increase is caused mostly by changes in land-use, particularly deforestation.[12]

Over the last three decades of the 20th century, GDP per capita and population growth were the main drivers of increases in greenhouse gas emissions.[13] CO2 emissions are continuing to rise due to the burning of fossil fuels and land-use change.[14][15]:71 Emissions scenarios, estimates of changes in future emission levels of greenhouse gases, have been projected that depend upon uncertain economic, sociological, technological, and natural developments.[16] In most scenarios, emissions continue to rise over the century, while in a few, emissions are reduced.[17][18] These emission scenarios, combined with carbon cycle modelling, have been used to produce estimates of how atmospheric concentrations of greenhouse gases will change in the future. Using the six IPCC SRES "marker" scenarios, models suggest that by the year 2100, the atmospheric concentration of CO2 could range between 541 and 970 ppm.[19] This is an increase of 90-250% above the concentration in the year 1750. Fossil fuel reserves are sufficient to reach these levels and continue emissions past 2100 if coal, oil sands or methane clathrates are extensively exploited.[20]

The popular media and the public often confuse global warming with the "ozone hole", i.e., the destruction of stratospheric ozone by chlorofluorocarbons.[21][22] Although there are a few areas of linkage, the relationship between the two is not strong. Reduced stratospheric ozone has had a slight cooling influence on surface temperatures, while increased tropospheric ozone has had a somewhat larger warming effect.[23]


  1. ^ Weart, Spencer (2008). "The Carbon Dioxide Greenhouse Effect". The Discovery of Global Warming. American Institute of Physics. Retrieved 21 April 2009.
  2. ^ IPCC (2007). "Chapter 1: Historical Overview of Climate Change Science" (PDF). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC WG1 AR4 Report. IPCC. pp. p97 (PDF page 5 of 36). Retrieved 21 April 2009. To emit 240 W m–2, a surface would have to have a temperature of around −19 °C. This is much colder than the conditions that actually exist at the Earth’s surface (the global mean surface temperature is about 14 °C). Instead, the necessary −19 °C is found at an altitude about 5 km above the surface.CS1 maint: Extra text (link)
  3. ^ Kiehl, J.T.; Trenberth, K.E. (1997). "Earth's Annual Global Mean Energy Budget" (PDF). Bulletin of the American Meteorological Society. 78 (2): 197–208. doi:10.1175/1520-0477(1997)078<0197:EAGMEB>2.0.CO;2. Archived from the original (PDF) on 2008-06-24. Retrieved 21 April 2009.
  4. ^ Schmidt, Gavin (6 Apr 2005). "Water vapour: feedback or forcing?". RealClimate. Retrieved 21 April 2009.
  5. ^ Russell, Randy (May 16, 2007). "The Greenhouse Effect & Greenhouse Gases". University Corporation for Atmospheric Research Windows to the Universe. Retrieved Dec 27, 2009.
  6. ^ EPA (2007). "Recent Climate Change: Atmosphere Changes". Climate Change Science Program. United States Environmental Protection Agency. Retrieved 21 April 2009.
  7. ^ Spahni, Renato (November 2005). "Atmospheric Methane and Nitrous Oxide of the Late Pleistocene from Antarctic Ice Cores". Science. 310 (5752): 1317–1321. doi:10.1126/science.1120132. PMID 16311333. Unknown parameter |coauthors= ignored (|author= suggested) (help); |access-date= requires |url= (help)
  8. ^ Siegenthaler, Urs (November 2005). "Stable Carbon Cycle–Climate Relationship During the Late Pleistocene" (PDF). Science. 310 (5752): 1313–1317. doi:10.1126/science.1120130. PMID 16311332. Retrieved 25 August 2010. Unknown parameter |coauthors= ignored (|author= suggested) (help)
  9. ^ Petit, J. R. (3 June 1999). "Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica" (PDF). Nature. 399 (6735): 429–436. doi:10.1038/20859. Retrieved 27 December 2009. Unknown parameter |coauthors= ignored (|author= suggested) (help)
  10. ^ Lüthi, D.; Le Floch, M.; Bereiter, B.; Blunier, T.; Barnola, J. M.; Siegenthaler, U.; Raynaud, D.; Jouzel, J.; Fischer, H.; Kawamura, K.; Stocker, T. F. (2008). "High-resolution carbon dioxide concentration record 650,000–800,000 years before present". Nature. 453 (7193): 379–382. doi:10.1038/nature06949. PMID 18480821.
  11. ^ Pearson, PN; Palmer, MR (2000). "Atmospheric carbon dioxide concentrations over the past 60 million years". Nature. 406 (6797): 695–699. doi:10.1038/35021000. PMID 10963587. More than one of |author= and |last1= specified (help)
  12. ^ IPCC (2001). "Summary for Policymakers" (PDF). Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. IPCC. Retrieved 21 April 2009.
  13. ^ Rogner et al., 2007. Intensities
  14. ^ Cite error: The named reference nrc2008 was invoked but never defined (see the help page).
  15. ^ World Bank (2010). World Development Report 2010: Development and Climate Change. The International Bank for Reconstruction and Development / The World Bank, 1818 H Street NW, Washington DC 20433. doi:10.1596/978-0-8213-7987-5. ISBN 978-0-8213-7987-5. Retrieved 2010-04-06.
  16. ^ Fisher, B.S., N. Nakicenovic, K. Alfsen, J. Corfee Morlot, F. de la Chesnaye, J.-Ch. Hourcade, K. Jiang, M. Kainuma, E. La Rovere, A. Matysek, A. Rana, K. Riahi, R. Richels, S. Rose, D. van Vuuren, R. Warren (2007). 3.1 Emissions scenarios. In (book chapter): Issues related to mitigation in the long term context. In: Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Inter-governmental Panel on Climate Change (B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds)). Print version: Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. This version: IPCC website. ISBN 978-0-521-70598-1. Retrieved 2010-06-19.CS1 maint: Multiple names: authors list (link)
  17. ^ Morita, T. and J. Robertson (co-ordinating lead authors). A. Adegbulugbe, J. Alcamo, D. Herbert, E.L.L. Rovere, N. Nakicenovic, H. Pitcher, P. Raskin, K. Riahi, A. Sankovski, V. Sokolov, B. de Vries, and D. Zhou (lead authors). K. Jiang, Ton Manders, Y. Matsuoka, S. Mori, A. Rana, R.A. Roehrl, K.E. Rosendahl, and K. Yamaji (contributing authors). M. Chadwick and J. Parikh (review editors) (2001). Emissions and Other Results of the SRES Scenarios. In (book chapter): 2. Greenhouse Gas Emission Mitigation Scenarios and Implications. In: Climate Change 2001: Mitigation. Contribution of Working Group III to the Third Assessment Report of the Intergovernmental Panel on Climate Change (B. Metz, O. Davidson, R. Swart, and J. Pan (eds.)). Print version: Cambridge University Press. This version: GRID-Arendal website. doi:10.2277/0521807697. ISBN 978-0-521-80769-2. Retrieved 2010-06-19.CS1 maint: Multiple names: authors list (link)
  18. ^ Rogner et al., 2007, Figure 1.7
  19. ^ Prentice, I.C. (co-ordinating lead author). G.D. Farquhar, M.J.R. Fasham, M.L. Goulden, M. Heimann, V.J. Jaramillo, H.S. Kheshgi, C. Le Quéré, R.J. Scholes, D.W.R. Wallace (lead authors). D. Archer, M.R. Ashmore, O. Aumont, D. Baker, M. Battle, M. Bender, L.P. Bopp, P. Bousquet, K. Caldeira, P. Ciais, P.M. Cox, W. Cramer, F. Dentener, I.G. Enting, C.B. Field, P. Friedlingstein, E.A. Holland, R.A. Houghton, J.I. House, A. Ishida, A.K. Jain, I.A. Janssens, F. Joos, T. Kaminski, C.D. Keeling, R.F. Keeling, D.W. Kicklighter, K.E. Kohfeld, W. Knorr, R. Law, T. Lenton, K. Lindsay, E. Maier-Reimer, A.C. Manning, R.J. Matear, A.D. McGuire, J.M. Melillo, R. Meyer, M. Mund, J.C. Orr, S. Piper, K. Plattner, P.J. Rayner, S. Sitch, R. Slater, S. Taguchi, P.P. Tans, H.Q. Tian, M.F. Weirig, T. Whorf, A. Yool (contributing authors). L. Pitelka, A. Ramirez Rojas (review editors) (2001). Executive Summary. In (book chapter): 3. The Carbon Cycle and Atmospheric Carbon Dioxide. In: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (J.T. Houghton, Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, C.A. Johnson (eds)). Print version: Cambridge University Press. This version: GRID-Arendal website. ISBN 978-0-521-80767-8. Retrieved 2010-06-19.CS1 maint: Multiple names: authors list (link)
  20. ^ Nakicenovic., N.; et al. (2001). "An Overview of Scenarios: Resource Availability". IPCC Special Report on Emissions Scenarios. IPCC. Retrieved 21 April 2009.CS1 maint: Explicit use of et al. (link)
  21. ^ Newell, P.J., 2000: Climate for change: non-state actors and the global politics of greenhouse. Cambridge University Press, ISBN 0521632501.
  22. ^ "Americans Fail the Climate Quiz", National Public Radio, 3 December 2010.
  23. ^ Shindell, Drew; Faluvegi, Greg; Lacis, Andrew; Hansen, James; Ruedy, Reto; Aguilar, Elliot (2006). "Role of tropospheric ozone increases in 20th-century climate change". Journal of Geophysical Research. 111 (D8): D08302. doi:10.1029/2005JD006348.