Ozone layer
The ozone layer or ozone shield is a region of
The ozone layer was discovered in 1913 by French physicists
The ozone layer absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light (from about 200
In 1985, atmospheric research revealed that the ozone layer was being depleted by chemicals released by industry, mainly
Venus also has a thin ozone layer at an altitude of 100 kilometers above the planet's surface.[5]
Sources
The
About 90 percent of the ozone in the atmosphere is contained in the stratosphere. Ozone concentrations are greatest between about 20 and 40 kilometres (66,000 and 131,000 ft), where they range from about 2 to 8 parts per million. If all of the ozone were compressed to the pressure of the air at sea level, it would be only 3 millimetres (1⁄8 inch) thick.[6]
Ultraviolet light
Although the concentration of the ozone in the ozone layer is very small, it is vitally important to life because it absorbs biologically harmful ultraviolet (UV) radiation coming from the Sun. Extremely short or vacuum UV (10–100 nm) is screened out by nitrogen. UV radiation capable of penetrating nitrogen is divided into three categories, based on its wavelength; these are referred to as UV-A (400–315 nm),
UV-C, which is very harmful to all living things, is entirely screened out by a combination of dioxygen (< 200 nm) and ozone (> about 200 nm) by around 35 kilometres (115,000 ft) altitude. UV-B radiation can be harmful to the skin and is the main cause of
Ozone is transparent to most UV-A, so most of this longer-wavelength UV radiation reaches the surface, and it constitutes most of the UV reaching the Earth. This type of UV radiation is significantly less harmful to DNA, although it may still potentially cause physical damage, premature aging of the skin, indirect genetic damage, and skin cancer.[8]
Distribution in the stratosphere
This section needs additional citations for verification. (February 2013) |
The thickness of the ozone layer varies worldwide and is generally thinner near the equator and thicker near the poles.[9] Thickness refers to how much ozone is in a column over a given area and varies from season to season. The reasons for these variations are due to atmospheric circulation patterns and solar intensity.[10]
The majority of ozone is produced over the
Research has found that the ozone levels in the United States are highest in the spring months of April and May and lowest in October. While the total amount of ozone increases moving from the tropics to higher latitudes, the concentrations are greater in high northern latitudes than in high southern latitudes, with spring ozone columns in high northern latitudes occasionally exceeding 600 DU and averaging 450 DU whereas 400 DU constituted a usual maximum in the Antarctic before anthropogenic ozone depletion. This difference occurred naturally because of the weaker polar vortex and stronger Brewer–Dobson circulation in the northern hemisphere owing to that hemisphere’s large mountain ranges and greater contrasts between land and ocean temperatures.
Depletion
The ozone layer can be depleted by
The breakdown of ozone in the stratosphere results in reduced absorption of ultraviolet radiation. Consequently, unabsorbed and dangerous ultraviolet radiation is able to reach the Earth's surface at a higher intensity. Ozone levels have dropped by a worldwide average of about 4 percent since the late 1970s. For approximately 5 percent of the Earth's surface, around the north and south poles, much larger seasonal declines have been seen, and are described as "ozone holes". "Ozone holes" are actually patches in the ozone layer in which the ozone is thinner. The thinnest parts of the ozone are at the
Regulation attempts have included but not have been limited to the Clean Air Act implemented by the United States Environmental Protection Agency. The Clean Air Act introduced the requirement of National Ambient Air Quality Standards (NAAQS) with ozone pollutions being one of six criteria pollutants. This regulation has proven to be effective since counties, cities and tribal regions must abide by these standards and the EPA also provides assistance for each region to regulate contaminants.[15] Effective presentation of information has also proven to be important in order to educate the general population of the existence and regulation of ozone depletion and contaminants. A scientific paper was written by Sheldon Ungar in which the author explores and studies how information about the depletion of the ozone, climate change and various related topics. The ozone case was communicated to lay persons "with easy-to-understand bridging metaphors derived from the popular culture" and related to "immediate risks with everyday relevance".[16] The specific metaphors used in the discussion (ozone shield, ozone hole) proved quite useful and, compared to global climate change, the ozone case was much more seen as a "hot issue" and imminent risk. Lay people were cautious about a depletion of the ozone layer and the risks of skin cancer.
"Bad" ozone can cause adverse health risks respiratory effects (difficulty breathing) and is proven to be an aggravator of respiratory illnesses such as asthma, COPD and emphysema.[17] That is why many countries have set in place regulations to improve "good" ozone and prevent the increase of "bad" ozone in urban or residential areas. In terms of ozone protection (the preservation of "good" ozone) the European Union has strict guidelines on what products are allowed to be bought, distributed or used in specific areas.[18] With effective regulation, the ozone is expected to heal over time.[19]
In 1978, the United States, Canada and
On August 2, 2003, scientists announced that the global depletion of the ozone layer may be slowing down because of the international regulation of ozone-depleting substances. In a study organized by the American Geophysical Union, three satellites and three ground stations confirmed that the upper-atmosphere ozone-depletion rate slowed significantly during the previous decade. Some breakdown can be expected to continue because of ODSs used by nations which have not banned them, and because of gases which are already in the stratosphere. Some ODSs, including CFCs, have very long atmospheric lifetimes, ranging from 50 to over 100 years. It has been estimated that the ozone layer will recover to 1980 levels near the middle of the 21st century.[24] A gradual trend toward "healing" was reported in 2016.[25]
Compounds containing
The residual effects of CFCs accumulating within the atmosphere lead to a concentration gradient between the atmosphere and the ocean. This organohalogen compound is able to dissolve into the ocean's surface waters and is able to act as a time-dependent tracer. This tracer helps scientists study ocean circulation by tracing biological, physical and chemical pathways.[27]
Implications for astronomy
As ozone in the atmosphere prevents most energetic ultraviolet radiation reaching the surface of the Earth, astronomical data in these wavelengths have to be gathered from satellites orbiting above the atmosphere and ozone layer. Most of the light from young hot stars is in the ultraviolet and so study of these wavelengths is important for studying the origins of galaxies. The Galaxy Evolution Explorer, GALEX, is an orbiting ultraviolet space telescope launched on April 28, 2003, which operated until early 2012.[28]
-
This GALEX image of the Cygnus Loop nebula could not have been taken from the surface of the Earth because the ozone layer blocks the ultra-violet radiation emitted by the nebula.
See also
- Cambrian explosion
- Nuclear winter
- Oxygen
- United Nations Environment Programme
- Short-lived climate pollutants
References
- ^ "Ozone Basics". NOAA. March 20, 2008. Archived from the original on November 21, 2017. Retrieved January 29, 2007.
- S2CID 128994884.
- ^ "Ozone layer". Retrieved September 23, 2007.
- ^ An Interview with Lee Thomas, EPA's 6th Administrator. Video, Transcript (see p13). April 19, 2012.
- ^ SPACE.com staff (October 11, 2011). "Scientists discover Ozone Layer on Venus". SPACE.com. Purch. Retrieved October 3, 2015.
- ^ "NASA Facts Archive". Retrieved June 9, 2011.
- PMID 14664632. Archived from the original(PDF) on June 17, 2012. Retrieved March 14, 2015.
- S2CID 22224492.
- ^ ISBN 9788131303962. Retrieved January 12, 2016.
- ^ "Nasa Ozone Watch: Ozone facts". ozonewatch.gsfc.nasa.gov. Retrieved September 16, 2021.
- hdl:1721.1/99159.
- ^ "Halocarbons and Other Gases". Emissions of Greenhouse Gases in the United States 1996. Energy Information Administration. 1997. Archived from the original on June 29, 2008. Retrieved June 24, 2008.
- ^ "NOAA Study Shows Nitrous Oxide Now Top Ozone-Depleting Emission". NOAA. August 27, 2009. Retrieved November 8, 2011.
- ^ "ozone layer | National Geographic Society". education.nationalgeographic.org. Retrieved May 30, 2022.
- ^ US EPA, OAR (December 14, 2016). "Ozone Implementation Regulatory Actions". www.epa.gov. Retrieved May 30, 2022.
- S2CID 7089937.
- PMID 31736954.
- ^ "Ozone Regulation". ec.europa.eu. Retrieved May 30, 2022.
- ^ US EPA, OAR (July 15, 2015). "International Treaties and Cooperation about the Protection of the Stratospheric Ozone Layer". www.epa.gov. Retrieved May 30, 2022.
- ^ Morrisette, Peter M. (1989). "The Evolution of Policy Responses to Stratospheric Ozone Depletion". Natural Resources Journal. 29: 793–820. Retrieved April 20, 2010.
- ^ An Interview with Lee Thomas, EPA's 6th Administrator. Video, Transcript (see p15). April 19, 2012.
- ^ "Amendments to the Montreal Protocol". EPA. August 19, 2010. Retrieved March 28, 2011.
- ^ "Brief Questions and Answers on Ozone Depletion". EPA. June 28, 2006. Retrieved November 8, 2011.
- ^ "Stratospheric Ozone and Surface Ultraviolet Radiation" (PDF). Scientific Assessment of Ozone Depletion: 2010. WMO. 2011. Retrieved March 14, 2015.
- PMID 27365314.
- ^ "Ozone Depletion Glossary". EPA. Retrieved September 3, 2008.
- PMID 21329203. Archived from the original(PDF) on February 10, 2015.
- ^ "ozone layer". National Geographic Society. May 9, 2011. Retrieved September 16, 2021.
Further reading
- Science
- S2CID 129725437.
- Andersen, S.O.; Sarma, K.M.; Sinclair, L. (2012). Protecting the Ozone Layer: The United Nations History. Taylor & Francis. ISBN 978-1-84977-226-6.
- elected officials matters more than their partyaffiliation.... Change can happen – but not on its own. We need to drive it." (p. 76.)
- United Nations Environment Programme (2010). Environmental Effects of Ozone Depletion and its Interactions with Climate Change: 2010 Assessment. Nairobi: UNEP.
- Velders, G. J. M.; Fahey, D. W.; Daniel, J. S.; McFarland, M.; Andersen, S. O. (2009). "The large contribution of projected HFC emissions to future climate forcing". Proceedings of the National Academy of Sciences. 106 (27): 10949–10954. S2CID 3743609.
- Velders, Guus J.M.; Andersen, Stephen O.; Daniel, John S.; Fahey, David W.; McFarland, Mack (2007). "The Importance of the Montreal Protocol in Protecting Climate". Proceedings of the National Academy of Sciences of the United States of America. 104 (12): 4814–4819. PMID 17360370.
- Policy
- Zaelke, Durwood; Borgford-Parnell, Nathan (2015). "The importance of phasing down hydrofluorocarbons and other short-lived climate pollutants". Journal of Environmental Studies and Sciences. 5 (2): 169–175. S2CID 128974741.
- Xu, Y.; Zaelke, D.; Velders, G. J. M.; Ramanathan, V. (2013). "The role of HFCS in mitigating 21st century climate change". Atmospheric Chemistry and Physics. 13 (12): 6083–6089. .
- Molina, M.; Zaelke, D.; Sarma, K. M.; Andersen, S. O.; Ramanathan, V.; Kaniaru, D. (2009). "Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions". Proceedings of the National Academy of Sciences. 106 (49): 20616–20621. S2CID 13240115.
- Anderson, S. O.; Sarma, M. K.; Taddonio, K. (2007). Technology Transfer for the Ozone Layer: Lessons for Climate Change. London: Earthscan. ISBN 9781849772846.
- Benedick, Richard Elliot; World Wildlife Fund (U.S.); Institute for the Study of Diplomacy. Georgetown University. (1998). Ozone Diplomacy: New Directions in Safeguarding the Planet (2nd ed.). Harvard University Press. ISBN 978-0-674-65003-9. (Ambassador Benedick was the Chief U.S. Negotiator at the meetings that resulted in the Montreal Protocol.)
- Chasek, P. S.; Downie, David L.; Brown, J. W. (2013). Global Environmental Politics (6th ed.). Boulder: Westview Press. ISBN 9780813348971.
- Grundmann, Reiner (2001). Transnational Environmental Policy: Reconstructing Ozone. Psychology Press. ISBN 978-0-415-22423-9.
- Parson, E. (2003). Protecting the Ozone Layer: Science and Strategy. Oxford: Oxford University Press. ISBN 9780190288716.
External links
- Stratospheric ozone: an electronic textbook
- Ozone Layer Info
- The CAMS stratospheric ozone service delivers maps, datasets and validation reports about the past and current state of the ozone layer.
- Ozone layer at Curlie