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Encyclopedia > Ozone depletion
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Global monthly average total ozone amount
Global monthly average total ozone amount

Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since the late 1970s; and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. The latter phenomenon is commonly referred to as the ozone hole. In addition to this well-known stratospheric ozone depletion, there are also tropospheric ozone depletion events, which occur near the surface in polar regions during spring. Air pollution Pollution is the introduction of pollutants (whether chemical substances, or energy such as noise, heat, or light) into the environment to such a point that its effects become harmful to human health, other living organisms, or the environment. ... Air pollution is the modification of the natural characteristics of the atmosphere by a chemical, particulate matter, or biological agent. ... The term acid rain is commonly used to mean the deposition of acidic components in rain, snow, fog, dew, or dry particles. ... An air quality measurement station in Edinburgh, Scotland The Air Quality Index (AQI) is a standardized indicator of the air quality in a given location. ... Atmospheric dispersion modeling is performed with computer programs that use mathematical equations and algorithms to simulate how pollutants in the ambient atmosphere disperse in the atmosphere. ... Tetrafluoroethane (a haloalkane) is a clear liquid which boils well below room temperature (as seen here) and can be extracted from common canned air canisters by simply inverting them during use. ... Global dimming is the gradual reduction in the amount of global direct irradiance at the Earths surface that was observed for several decades after the start of systematic measurements in 1950s. ... Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ... Haze is an atmospheric phenomenon where dust, smoke and other pollutant particles obscure the normal clarity of the sky. ... Indoor Air Quality (IAQ) deals with the content of interior air that could affect health and comfort of building occupants. ... Particulates, alternatively referred to as particulate matter (PM), aerosols or fine particles, are tiny particles of solid or liquid suspended in a gas. ... For other uses, see Smog (disambiguation). ... Raw sewage and industrial waste flows into the U.S. from Mexico as the New River passes from Mexicali, Baja California to Calexico, California Water pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater caused by human activities, which can be harmful to organisms and... Eutrophication, strictly speaking, means an increase in chemical nutrients -- typically compounds containing nitrogen or phosphorus -- in an ecosystem. ... It has been suggested that Anoxic sea water, Oxygen minimum zone, and Hypoxic zone be merged into this article or section. ... Pumping of highly toxic (dark black) sludge, much seeps back into the ocean in the form of particles. ... Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s Ocean acidification is the name given to the ongoing decrease in the pH of the Earths oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. ... A beach after an oil spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment due to human activity, and is a form of pollution. ... Ship pollution is the pollution of water by shipping! It is a problem that has been accelerating as trade has become increasingly globalized. ... Runoff flowing into a stormwater drain Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle[1][2]. Runoff that occurs on surfaces before reaching a channel is also called overland flow. ... Thermal pollution is a temperature change in natural water bodies caused by human influence. ... Wastewater is any water that has been adversely affected in quality by anthropogenic influence. ... Waterborne diseases are caused by pathogenic microorganisms which are directly transmitted when contaminated drinking water is consumed. ... Water quality is the physical, chemical and biological characteristics of water, characterized through the methods of hydrometry. ... Standing water redirects here. ... Excavation of leaking underground storage tank causing soil contamination Soil pollution comprises the pollution of soils with materials, mostly chemicals, that are out of place or are present at concentrations higher than normal which may have adverse effects on humans or other organisms. ... Bioremediation can be defined as any process that uses microorganisms, fungi, green plants or their enzymes to return the environment altered by contaminants to its original condition. ... An herbicide is used to kill unwanted plants. ... A pesticide is a substance or mixture of substances used for preventing, controlling, or lessening the damage caused by a pest. ... The radiation warning symbol (trefoil). ... This article about actinides in the environment is about the sources, environmental behaviour and effects of actinides in the environment. ... The environmental radioactivity page is devoted to the subject of radioactive materials in man and his environment. ... 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Lantana invasion of abandoned citrus plantation; Moshav Sdey Hemed, Israel The term invasive species refers to a subset of introduced species or non-indigenous species that are rapidly expanding outside of their native range. ... This time exposure photo of New York City shows sky glow, one form of light pollution. ... Noise pollution (or environmental noise in technical venues) is displeasing human or machine created sound that disrupts the environment. ... Radio spectrum pollution is the straying of waves in the radio and electromagnetic spectrums outside their allocations that cause problems for some activities. ... Visual pollution is the term given to unattractive visual elements of a vista, a landscape, or any other thing that a person might want to look at. ... The largest Antarctic ozone hole recorded as of September 2006 For other similarly-named agreements, see Montreal Convention (disambiguation). ... Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution Concerning the Control of Emissions of Nitrogen Oxides or Their Transboundary Fluxes, opened for signature on 31 October 1988 and entered into force on 14 February 1991, was to provide for the control or reduction of nitrogen oxides and... The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing greenhouse gases that cause climate change. ... note - abbreviated as Air Pollution opened for signature - 13 November 1979 entered into force - 16 March 1983 objective - to protect the human environment against air pollution and to gradually reduce and prevent air pollution, including long-range transboundary air pollution parties - (48) Armenia, Austria, Belarus, Belgium, Bosnia and Herzegovina, Bulgaria... This list is incomplete; you can help by expanding it. ... The Department for Environment, Food and Rural Affairs (Defra) is the United Kingdom government department responsible for environmental protection, food production and standards, agriculture, fisheries and rural communities in England. ... EPA redirects here. ... Global Atmosphere Watchs logo The Global Atmosphere Watch (GAW) is a worldwide system established by the World Meteorological Organization – a United Nations agency – to monitor trends in the Earths atmosphere. ... Greenpeace protest against Esso / Exxon Mobil. ... The National Ambient Air Quality Standards (NAAQS) are standards established by the United States Environmental Protection Agency that apply for outdoor air throughout the country. ... Environmental science is the study of the interactions among the physical, chemical and biological components of the environment; with a focus on pollution and degradation of the environment related to human activities; and the impact on biodiversity and sustainability from local and global development. ... This article is about the natural environment. ... Image File history File links TOMS_Global_Ozone_65N-65S.png Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ozone layer Ozone depletion User:SEWilco/Images ... Image File history File links TOMS_Global_Ozone_65N-65S.png Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Ozone layer Ozone depletion User:SEWilco/Images ... For other uses, see Ozone (disambiguation). ... This article is about Earth as a planet. ... Atmosphere diagram showing stratosphere. ... Chemical mechanism of the bromine explosion. ...


The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the most important process in both trends is catalytic destruction of ozone by atomic chlorine and bromine.[1] The main source of these halogen atoms in the stratosphere is photodissociation of chlorofluorocarbon (CFC) compounds, commonly called freons, and of bromofluorocarbon compounds known as halons. These compounds are transported into the stratosphere after being emitted at the surface. Both ozone depletion mechanisms strengthened as emissions of CFCs and halons increased. In chemistry and biology, catalysis (in Greek meaning to annul) is the acceleration of the rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... This article is about the chemical series. ... Photodissociation is the breakup of molecules caused by exposure to photons. ... For other uses, see CFC (disambiguation). ... Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant. ... The haloalkanes (also known as Halogenoalkanes) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide. ...


CFCs and other contributory substances are commonly referred to as ozone-depleting substances (ODS). Since the ozone layer prevents most harmful UVB wavelengths (270–315 nm) of ultraviolet light (UV light) from passing through the Earth's atmosphere, observed and projected decreases in ozone have generated worldwide concern leading to adoption of the Montreal Protocol banning the production of CFCs and halons as well as related ozone depleting chemicals such as carbon tetrachloride and trichloroethane. It is suspected that a variety of biological consequences such as increases in skin cancer, damage to plants, and reduction of plankton populations in the ocean's photic zone may result from the increased UV exposure due to ozone depletion.[citation needed] For other uses, see Ultraviolet (disambiguation). ... Air redirects here. ... The largest Antarctic ozone hole recorded as of September 2006 For other similarly-named agreements, see Montreal Convention (disambiguation). ... R-phrases , , , , S-phrases , , , , , Flash point Non flammable Supplementary data page Structure and properties n, εr, etc. ... The chemical compound 1,1,1-trichloroethane is a chlorinated hydrocarbon that was until recently widely used as an industrial solvent. ... Skin cancer is a malignant growth on the skin which can have many causes. ... This article is about the real-life under-sea organisms. ... The photic zone is the depth of the water, whether in a lake or an ocean, that is exposed to sufficient sunlight for photosynthesis to occur. ...

Contents

Ozone cycle overview

Three forms (or allotropes) of oxygen are involved in the ozone-oxygen cycle: Oxygen atoms (O or atomic oxygen), oxygen gas (O2 or diatomic oxygen), and ozone gas (O3 or triatomic oxygen). Ozone is formed in the stratosphere when oxygen molecules photodissociate after absorbing an ultraviolet photon whose wavelength is shorter than 240 nm. This produces two oxygen atoms. The atomic oxygen then combines with O2 to create O3. Ozone molecules absorb UV light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom then joins up with an oxygen molecule to regenerate ozone. This is a continuing process which terminates when an oxygen atom "recombines" with an ozone molecule to make two O2 molecules: O + O3 → 2 O2 Allotropy (Gr. ... Ozone-oxygen cycle in the ozone layer. ... This article is about the chemical element and its most stable form, or dioxygen. ... For other uses, see Ozone (disambiguation). ... Photodissociation is the breakup of molecules caused by exposure to photons. ... For other uses, see Ultraviolet (disambiguation). ...


The overall amount of ozone in the stratosphere is determined by a balance between photochemical production and recombination.


Ozone can be destroyed by a number of free radical catalysts, the most important of which are the hydroxyl radical (OH·), the nitric oxide radical (NO·) and atomic chlorine (Cl·) and bromine (Br·). All of these have both natural and anthropogenic (manmade) sources; at the present time, most of the OH· and NO· in the stratosphere is of natural origin, but human activity has dramatically increased the high in oxygen chlorine and bromine. These elements are found in certain stable organic compounds, especially chlorofluorocarbons (CFCs), which may find their way to the stratosphere without being destroyed in the troposphere due to their low reactivity. Once in the stratosphere, the Cl and Br atoms are liberated from the parent compounds by the action of ultraviolet light, e.g. ('h' is Planck's constant, 'ν' is frequency of electromagnetic radiation) In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... Hydroxide is a functional group consisting of oxygen and hydrogen: -O−H It has a charge of 1-. The term hydroxyl group is used when the functional group -OH is counted as a substituent of an organic compound. ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Bromo redirects here. ... For other uses, see CFC (disambiguation). ... Atmosphere diagram showing stratosphere. ... A commemoration plaque for Max Planck on his discovery of Plancks constant, in front of Humboldt University, Berlin. ... For other uses, see Frequency (disambiguation). ... This box:      Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. ...


CFCl3 + hν → CFCl2 + Cl


The Cl and Br atoms can then destroy ozone molecules through a variety of catalytic cycles. In the simplest example of such a cycle,[2] a chlorine atom reacts with an ozone molecule, taking an oxygen atom with it (forming ClO) and leaving a normal oxygen molecule. A free oxygen atom then takes away the oxygen from the ClO, and the final result is an oxygen molecule and a chlorine atom, which then reinitiates the cycle. The chemical shorthand for these gas-phase reactions is: Catalyst redirects here. ...


Cl + O3 → ClO + O2


ClO + O → Cl + O2


The net reaction is: O3 + O → 2 O2, the "recombination" reaction given above.


The overall effect is to increase the rate of recombination, leading to an overall decrease in the amount of ozone. For this particular mechanism to operate there must be a source of O atoms, which is primarily the photo dissociation of O3; thus this mechanism is only important in the upper stratosphere where such atoms are abundant. More complicated mechanisms have been discovered that lead to ozone destruction in the lower stratosphere as well.


A single chlorine atom would keep on destroying ozone for up to two years (the time scale for transport back down to the troposphere) were it not for reactions that remove them from this cycle by forming reservoir species such as hydrogen chloride (HCl) and chlorine nitrate (ClONO2). On a per atom basis, bromine is even more efficient than chlorine at destroying ozone, but there is much less bromine in the atmosphere at present. As a result, both chlorine and bromine contribute significantly to the overall ozone depletion. Laboratory studies have shown that fluorine and iodine atoms participate in analogous catalytic cycles. However, in the Earth's stratosphere, fluorine atoms react rapidly with water and methane to form strongly-bound HF, while organic molecules which contain iodine react so rapidly in the lower atmosphere that they do not reach the stratosphere in significant quantities. Furthermore, a single chlorine atom is able to react with 100,000 ozone molecules. This fact plus the amount of chlorine released into the atmosphere by chlorofluorocarbons(CFCs) yearly demonstrates how dangerous CFCs are to the environment. [3] R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Chlorine nitrate is an important atmospheric gas present in the stratosphere. ... R-phrases , S-phrases , , , , Flash point nonflammable Related Compounds Other anions Hydrochloric acid Hydrobromic acid Hydroiodic acid Related compounds Hydrogen fluoride fluorosilicic acid Supplementary data page Structure and properties n, εr, etc. ...


Quantitative understanding of the chemical ozone loss process

New research on the breakdown of a key molecule in these ozone-depleting chemicals, dichlorine peroxide (Cl2O2), calls into question the completeness of present atmospheric models of polar ozone depletion. Specifically, chemists at NASA's Jet Propulsion Laboratory in Pasadena, California, found in 2007 that the temperatures, and the spectrum and intensity of radiation present in the stratosphere created conditions insufficient to allow the rate of chemical-breakdown required to release chlorine radicals in the volume necessary to explain observed rates of ozone depletion. Instead, laboratory tests, designed to be the most accurate reflection of stratospheric conditions to date, showed the decay of the crucial molecule almost a magnitude lower than previously thought[4].[5][6]


Observations on ozone layer depletion

The most pronounced decrease in ozone has been in the lower stratosphere. However, the ozone hole is most usually measured not in terms of ozone concentrations at these levels (which are typically of a few parts per million) but by reduction in the total column ozone, above a point on the Earth's surface, which is normally expressed in Dobson units, abbreviated as "DU". Marked decreases in column ozone in the Antarctic spring and early summer compared to the early 1970s and before have been observed using instruments such as the Total Ozone Mapping Spectrometer (TOMS).[7] Atmosphere diagram showing stratosphere. ... Dobson units (DU) are the standard way to express ozone amounts in the atmosphere. ... Greek ἀνταρκτικός, opposite the arctic) is a continent surrounding the Earths South Pole. ... Categories: Stub ...

Lowest value of ozone measured by TOMS each year in the ozone hole
Lowest value of ozone measured by TOMS each year in the ozone hole

Reductions of up to 70% in the ozone column observed in the austral (southern hemispheric) spring over Antarctica and first reported in 1985 (Farman et al 1985) are continuing.[8] Through the 1990s, total column ozone in September and October have continued to be 40–50% lower than pre-ozone-hole values. In the Arctic the amount lost is more variable year-to-year than in the Antarctic. The greatest declines, up to 30%, are in the winter and spring, when the stratosphere is colder. Download high resolution version (792x611, 99 KB)This image shows the lowest value of ozone measured by TOMS each year in the ozone hole. ... Download high resolution version (792x611, 99 KB)This image shows the lowest value of ozone measured by TOMS each year in the ozone hole. ... Categories: Stub ... For the ships, see USS Arctic, SS Arctic, MV Arctic The red line indicates the 10°C isotherm in July, sometimes used to define the Arctic region border Artificially coloured topographical map of the Arctic region The Arctic is the region around the Earths North Pole, opposite the Antarctic...


Reactions that take place on polar stratospheric clouds (PSCs) play an important role in enhancing ozone depletion.[9] PSCs form more readily in the extreme cold of Antarctic stratosphere. This is why ozone holes first formed, and are deeper, over Antarctica. Early models failed to take PSCs into account and predicted a gradual global depletion, which is why the sudden Antarctic ozone hole was such a surprise to many scientists.[citation needed]


In middle latitudes it is preferable to speak of ozone depletion rather than holes. Declines are about 3% below pre-1980 values for 35–60°N and about 6% for 35–60°S. In the tropics, there are no significant trends.[citation needed]


Ozone depletion also explains much of the observed reduction in stratospheric and upper tropospheric temperatures.[10][11] The source of the warmth of the stratosphere is the absorption of UV radiation by ozone, hence reduced ozone leads to cooling. Some stratospheric cooling is also predicted from increases in greenhouse gases such as CO2; however the ozone-induced cooling appears to be dominant.[citation needed] Atmosphere diagram showing the mesosphere and other layers. ... Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...


Predictions of ozone levels remain difficult. The World Meteorological Organization Global Ozone Research and Monitoring Project - Report No. 44 comes out strongly in favor for the Montreal Protocol, but notes that a UNEP 1994 Assessment overestimated ozone loss for the 1994–1997 period. Klaus Töpfer, UNEP Exec. ...


Chemicals in the atmosphere

CFCs in the atmosphere

Chlorofluorocarbons (CFCs) were invented by Thomas Midgley in the 1920s. They were used in air conditioning/cooling units, as aerosol spray propellants prior to the 1980s, and in the cleaning processes of delicate electronic equipment. They also occur as by-products of some chemical processes. No significant natural sources have ever been identified for these compounds — their presence in the atmosphere is due almost entirely to human manufacture. As mentioned in the ozone cycle overview above, when such ozone-depleting chemicals reach the stratosphere, they are dissociated by ultraviolet light to release chlorine atoms. The chlorine atoms act as a catalyst, and each can break down tens of thousands of ozone molecules before being removed from the stratosphere. Given the longevity of CFC molecules, recovery times are measured in decades. It is calculated that a CFC molecule takes an average of 15 years to go from the ground level up to the upper atmosphere, and it can stay there for about a century, destroying up to one hundred thousand ozone molecules during that time.[12] For other uses, see CFC (disambiguation). ... Thomas Midgley, Jr. ... Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ... Aerosol spray can Aerosol spray is a type of canister that sprays an aerosol when its button is pressed or held down. ... It has been suggested that this article or section be merged into Catalysis. ...


Verification of observations

Scientists have been increasingly able to attribute the observed ozone depletion to the increase of anthropogenic halogen compounds from CFCs by the use of complex chemistry transport models and their validation against observational data (e.g. SLIMCAT, CLaMS). These models work by combining satellite measurements of chemical concentrations and meteorological fields with chemical reaction rate constants obtained in lab experiments. They are able to identify not only the key chemical reactions but also the transport processes which bring CFC photolysis products into contact with ozone. This article is about the chemical series. ... Categories: Pages needing attention | Animal stubs ... Photodissociation is the breakup of molecules caused by exposure to photons. ...


The ozone hole and its causes

Image of the largest Antarctic ozone hole ever recorded (September 2006).
Image of the largest Antarctic ozone hole ever recorded (September 2006).

The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent ozone levels have dropped to as low as 33% of their pre-1975 values. The ozone hole occurs during the Antarctic spring, from September to early December, as strong westerly winds start to circulate around the continent and create an atmospheric container. Within this polar vortex, over 50% of the lower stratospheric ozone is destroyed during the Antarctic spring.[13] Image File history File links Size of this preview: 600 × 600 pixelsFull resolution (716 × 716 pixel, file size: 409 KB, MIME type: image/png) From September 21-30, 2006 the average area of the ozone hole was the largest ever observed, at 10. ... Image File history File links Size of this preview: 600 × 600 pixelsFull resolution (716 × 716 pixel, file size: 409 KB, MIME type: image/png) From September 21-30, 2006 the average area of the ozone hole was the largest ever observed, at 10. ... The polar vortex is a persistent, large-scale cyclone located near the Earths poles, in the middle and upper troposphere and the stratosphere. ...


As explained above, the overall cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons). In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction. The Cl-catalyzed ozone depletion can take place in the gas phase, but it is dramatically enhanced in the presence of polar stratospheric clouds (PSCs).[14] Polar stratospheric clouds (PSCs), also known as nacreous clouds, are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 metres (50,000–80,000 ft). ...


These polar stratospheric clouds form during winter, in the extreme cold. Polar winters are dark, consisting of 3 months without solar radiation (sunlight). Not only lack of sunlight contributes to a decrease in temperature but also the polar vortex traps and chills air. Temperatures hover around or below -80 °C. These low temperatures form cloud particles and are composed of either nitric acid (Type I PSC) or ice (Type II PSC). Both types provide surfaces for chemical reactions that lead to ozone destruction.[citation needed] The polar vortex is a persistent, large-scale cyclone located near the Earths poles, in the middle and upper troposphere and the stratosphere. ...


The photochemical processes involved are complex but well understood. The key observation is that, ordinarily, most of the chlorine in the stratosphere resides in stable "reservoir" compounds, primarily hydrogen chloride (HCl) and chlorine nitrate (ClONO2). During the Antarctic winter and spring, however, reactions on the surface of the polar stratospheric cloud particles convert these "reservoir" compounds into reactive free radicals (Cl and ClO). The clouds can also remove NO2 from the atmosphere by converting it to nitric acid, which prevents the newly formed ClO from being converted back into ClONO2. Photochemistry is the study of the interaction of light and chemicals. ...


The role of sunlight in ozone depletion is the reason why the Antarctic ozone depletion is greatest during spring. During winter, even though PSCs are at their most abundant, there is no light over the pole to drive the chemical reactions. During the spring, however, the sun comes out, providing energy to drive photochemical reactions, and melt the polar stratospheric clouds, releasing the trapped compounds.[citation needed]


Most of the ozone that is destroyed is in the lower stratosphere, in contrast to the much smaller ozone depletion through homogeneous gas phase reactions, which occurs primarily in the upper stratosphere.[citation needed]


Warming temperatures near the end of spring break up the vortex around mid-December. As warm, ozone-rich air flows in from lower latitudes, the PSCs are destroyed, the ozone depletion process shuts down, and the ozone hole heals.[citation needed]


Interest in ozone layer depletion

While the effect of the Antarctic ozone hole in decreasing the global ozone is relatively small, estimated at about 4% per decade, the hole has generated a great deal of interest because:

  • The decrease in the ozone layer was predicted in the early 1980s to be roughly 7% over a sixty-year period.[citation needed]
  • The sudden recognition in 1985 that there was a substantial "hole" was widely reported in the press. The especially rapid ozone depletion in Antarctica had previously been dismissed as a measurement error.[citation needed]
  • Many[citation needed] were worried that ozone holes might start to appear over other areas of the globe but to date the only other large-scale depletion is a smaller ozone "dimple" observed during the Arctic spring over the North Pole. Ozone at middle latitudes has declined, but by a much smaller extent (about 4–5% decrease).
  • If the conditions became more severe (cooler stratospheric temperatures, more stratospheric clouds, more active chlorine), then global ozone may decrease at a much greater pace. Standard global warming theory predicts that the stratosphere will cool.[citation needed]
  • When the Antarctic ozone hole breaks up, the ozone-depleted air drifts out into nearby areas. Decreases in the ozone level of up to 10% have been reported in New Zealand in the month following the break-up of the Antarctic ozone hole.

Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ...

Consequences of ozone layer depletion

Since the ozone layer absorbs UVB ultraviolet light from the Sun, ozone layer depletion is expected to increase surface UVB levels, which could lead to damage, including increases in skin cancer. This was the reason for the Montreal Protocol. Although decreases in stratospheric ozone are well-tied to CFCs and there are good theoretical reasons to believe that decreases in ozone will lead to increases in surface UVB, there is no direct observational evidence linking ozone depletion to higher incidence of skin cancer in human beings. This is partly due to the fact that UVA, which has also been implicated in some forms of skin cancer, is not absorbed by ozone, and it is nearly impossible to control statistics for lifestyle changes in the populace. Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Skin cancer is a malignant growth on the skin which can have many causes. ... Uva is a three-letter abbreviation with multiple meanings, as described below: Uva Province in Sri Lanka Uva is a parish in the Portuguese municipality of Vimioso Ultraviolet-A rays (UV-A) Ultraviolet Light Absorber University of Virginia (UVa), in the United States Universiteit van Amsterdam (UvA), one of the...


Increased UV

Ozone, while a minority constituent in the earth's atmosphere, is responsible for most of the absorption of UVB radiation. The amount of UVB radiation that penetrates through the ozone layer decreases exponentially with the slant-path thickness/density of the layer. Correspondingly, a decrease in atmospheric ozone is expected to give rise to significantly increased levels of UVB near the surface. A quantity is said to be subject to exponential decay if it decreases at a rate proportional to its value. ...


Increases in surface UVB due to the ozone hole can be partially inferred by radiative transfer model calculations, but cannot be calculated from direct measurements because of the lack of reliable historical (pre-ozone-hole) surface UV data, although more recent surface UV observation measurement programmes exist (e.g. at Lauder, New Zealand).[15] Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... The equation of radiative transfer describes the propagation of electromagnetic radiation through an atmosphere which is itself emitting radiation, absorbing radiation and scattering radiation. ...


Because it is this same UV radiation that creates ozone in the ozone layer from O2 (regular oxygen) in the first place, a reduction in stratospheric ozone would actually tend to increase photochemical production of ozone at lower levels (in the troposphere), although the overall observed trends in total column ozone still show a decrease, largely because ozone produced lower down has a naturally shorter photochemical lifetime, so it is destroyed before the concentrations could reach a level which would compensate for the ozone reduction higher up.[citation needed] Atmosphere diagram showing the mesosphere and other layers. ...


Biological effects of increased UV and microwave radiation from a depleted ozone layer

The main public concern regarding the ozone hole has been the effects of surface UV on human health. So far, ozone depletion in most locations has been typically a few percent and, as noted above, no direct evidence of health damage is available in most latitudes. Were the high levels of depletion seen in the ozone hole ever to be common across the globe, the effects could be substantially more dramatic. As the ozone hole over Antarctica has in some instances grown so large as to reach southern parts of Australia and New Zealand, environmentalists have been concerned that the increase in surface UV could be significant.[citation needed]


The public and scientific awareness of Ozone's ability to absorb dangerous frequencies in the ultraviolet band of light, specifically the Ultraviolet B band and its significance of removing harmful radiation in the precise frequencies that cause destruction of DNA molecules precludes the little known knowledge that Ozone has an important role in preventing a significant portion of very high energy microwaves from striking and affecting life on the earth. Ozone uses the mechanism of energy absorption via molecular rotational energy absorption of the ozone molecule rather than the UV electronic absorption mechanism. This frequency lies in the 9.077 um and the 14 um band. This band is little known because of the fact that there is little equipment that can produce these ultra high energetic microwave frequencies in the laboratory, so it is difficult to test effects on living matter in this range. Recently military microwave weaponry known as the "pain beam" was developed near this frequency. It specifically irritates human nerves. If the Ozone layer becomes significantly depleted, it is not clearly understood what the health effects would be to the living organisms, both people and plant. There is a significant amount of solar energy that is absobed by ozone in this high energy microwave frequency range. The unknown consequences of transmittance into the ecosystem would be open ended. Interestingly, water does not sufficiently absorb the suns energy in this band of energy, and the effects of the sun's full output of these microwaves would be directed to all living on the earth if the ozone layer were compromised. The spectrum frequencies assure us that the effects would be noted regardless of cloud cover, since water does not absorb much in this frequency range.


Effects of ozone layer depletion on Humans

UVB (the higher energy UV radiation absorbed by ozone) is generally accepted to be a contributory factor to skin cancer. In addition, increased surface UV leads to increased tropospheric ozone, which is a health risk to humans.[citation needed] The increased surface UV also represents an increase in the vitamin D synthetic capacity of the sunlight.[16] Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... Skin cancer is a malignant growth on the skin which can have many causes. ... Vitamin D is a fat soluble vitamin that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. ...


The cancer preventive effects of vitamin D represent a possible beneficial effect of ozone depletion.[7][8] In terms of health costs, the possible benefits of increased UV irradiance may outweigh the burden. [9]


1. Basal and Squamous Cell Carcinomas -- The most common forms of skin cancer in humans, basal and squamous cell carcinomas, have been strongly linked to UVB exposure. The mechanism by which UVB induces these cancers is well understood — absorption of UVB radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcription errors when the DNA replicates. These cancers are relatively mild and rarely fatal, although the treatment of squamous cell carcinoma sometimes requires extensive reconstructive surgery. By combining epidemiological data with results of animal studies, scientists have estimated that a one percent decrease in stratospheric ozone would increase the incidence of these cancers by 2%.[17] Basal cell carcinoma (BCC) is the most common skin cancer. ... Biopsy of a highly differentiated squamous cell carcinoma of the mouth. ... Sucrose, or common table sugar, is composed of glucose and fructose. ...


2. Malignant Melanoma -- Another form of skin cancer, malignant melanoma, is much less common but far more dangerous, being lethal in about 15% - 20% of the cases diagnosed. The relationship between malignant melanoma and ultraviolet exposure is not yet well understood, but it appears that both UVB and UVA are involved. Experiments on fish suggest that 90 to 95% of malignant melanomas may be due to UVA and visible radiation[18] whereas experiments on opossums suggest a larger role for UVB.[17] Because of this uncertainty, it is difficult to estimate the impact of ozone depletion on melanoma incidence. One study showed that a 10% increase in UVB radiation was associated with a 19% increase in melanomas for men and 16% for women.[19] A study of people in Punta Arenas, at the southern tip of Chile, showed a 56% increase in melanoma and a 46% increase in nonmelanoma skin cancer over a period of seven years, along with decreased ozone and increased UVB levels.[20] City of Punta Arenas Punta Arenas in Tierra del Fuego Sunrise view of the Strait of magellan Punta Arenas is the main city on the Strait of Magellan and the capital of the Región de Magallanes y la Antártica Chilena, Chile, and depending on the definition of city...


3. Cortical Cataracts -- Studies are suggestive of an association between ocular cortical cataracts and UV-B exposure, using crude approximations of exposure and various cataract assessment techniques. A detailed assessment of ocular exposure to UV-B was carried out in a study on Chesapeake Bay Watermen, where increases in average annual ocular exposure were associated with increasing risk of cortical opacity [21]. In this highly exposed group of predominantly white males, the evidence linking cortical opacities to sunlight exposure was the strongest to date. However, subsequent data from a population-based study in Beaver Dam, WI suggested the risk may be confined to men. In the Beaver Dam study, the exposures among women were lower than exposures among men, and no association was seen.[22] Moreover, there were no data linking sunlight exposure to risk of cataract in African Americans, although other eye diseases have different prevalences among the different racial groups, and cortical opacity appears to be higher in African Americans compared with whites.[23][24] Cataract is also used to mean a waterfall or where the flow of a river changes dramatically. ...


4. Increased Tropospheric Ozone -- Increased surface UV leads to increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties. At this time, ozone at ground level is produced mainly by the action of UV radiation on combustion gases from vehicle exhausts.[citation needed] The troposphere is the lowermost portion of Earths atmosphere and the one in which most weather phenomena occur. ... ed|other uses|reduction}} Illustration of a redox reaction Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... This article is about the chemical reaction combustion. ...


Effects on Crops

An increase of UV radiation would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are sensitive to UV light and they would be affected by its increase.[25] For other uses, see Rice (disambiguation). ... Orders The taxonomy is currently under revision. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ...


Effects on Plankton

Research has shown a widespread extinction of plankton 2 million years ago that coincided with a nearby supernova. There is a difference in the orientation and motility of planktons when excess of UV rays reach earth. Researchers speculate that the extinction was caused by a significant weakening of the ozone layer at that time when the radiation from the supernova produced nitrogen oxides that catalyzed the destruction of ozone (plankton are particularly susceptible to effects of UV light, and are vitally important to marine food webs).[26] This article is about the real-life under-sea organisms. ... For other uses, see Supernova (disambiguation). ... // The term nitrogen oxide typically refers to any binary compound of oxygen and nitrogen, or to a mixture of such compounds: Nitric oxide (NO), nitrogen(II) oxide Nitrogen dioxide (NO2), nitrogen(IV) oxide Nitrous oxide (N2O), nitrogen (I) oxide Dinitrogen trioxide (N2O3), nitrogen(II, IV) oxide Dinitrogen tetroxide (N2O4), nitrogen... Catalyst redirects here. ... Figure 1. ...


Public policy in response to the ozone hole

The full extent of the damage that CFCs have caused to the ozone layer is not known and will not be known for decades; however, marked decreases in column ozone have already been observed (as explained above).


After a 1976 report by the U.S. National Academy of Sciences concluded that credible scientific evidence supported the ozone depletion hypothesis, a few countries, including the United States, Canada, Sweden, and Norway, moved to eliminate the use of CFCs in aerosol spray cans. At the time this was widely regarded as a first step towards a more comprehensive regulation policy, but progress in this direction slowed in subsequent years, due to a combination of political factors (continued resistance from the halocarbon industry and a general change in attitude towards environmental regulation during the first two years of the Reagan administration) and scientific developments (subsequent National Academy assessments which indicated that the first estimates of the magnitude of ozone depletion had been overly large). The European Community rejected proposals to ban CFCs in aerosol sprays while even in the U.S., CFCs continued to be used as refrigerants and for cleaning circuit boards. Worldwide CFC production fell sharply after the U.S. aerosol ban, but by 1986 had returned nearly to its 1976 level. In 1980, DuPont closed down its research program into halocarbon alternatives. President Harding and the National Academy of Sciences at the White House, Washington, DC, April 1921 The National Academy of Sciences (NAS) is a corporation in the United States whose members serve pro bono as advisers to the nation on science, engineering, and medicine. ... Dupont, DuPont, Du Pont, or du Pont may refer to: // E.I. du Pont de Nemours and Company (DuPont), the worlds second largest chemical company Du Pont Motors Gilbert Dupont, a French stock brokerage part of retail banking network Crédit du Nord ST Dupont, a French manufacturer of...


The US Government's attitude began to change again in 1983, when William Ruckelshaus replaced Anne M. Burford as Administrator of the United States Environmental Protection Agency. Under Ruckelshaus and his successor, Lee Thomas, the EPA pushed for an international approach to halocarbon regulations. In 1985 20 nations, including most of the major CFC producers, signed the Vienna Convention which established a framework for negotiating international regulations on ozone-depleting substances. That same year, the discovery of the Antarctic ozone hole was announced, causing a revival in public attention to the issue. In 1987, representatives from 43 nations signed the Montreal Protocol. Meanwhile, the halocarbon industry shifted its position and started supporting a protocol to limit CFC production. The reasons for this were in part explained by "Dr. Mostafa Tolba, former head of the UN Environment Programme, who was quoted in the June 30, 1990 edition of The New Scientist, '...the chemical industry supported the Montreal Protocol in 1987 because it set up a worldwide schedule for phasing out CFCs, which [were] no longer protected by patents. This provided companies with an equal opportunity to market new, more profitable compounds.'"[27] William Doyle Ruckelshaus (born July 24, 1932) is an attorney and civil servant in the United States. ... Anne M. Burford (21 April 1942–18 July 2004) was the first female Administrator of the Environmental Protection Agency, serving under President Ronald Reagan. ... EPA redirects here. ... The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer from depletion by phasing out the production of a number of substances believed to be responsible for ozone depletion. ... is the 181st day of the year (182nd in leap years) in the Gregorian calendar. ... This article is about the year. ... New Scientist is a weekly international science magazine covering recent developments in science and technology for a general English-speaking audience. ...


At Montreal, the participants agreed to freeze production of CFCs at 1986 levels and to reduce production by 50% by 1999. After a series of scientific expeditions to the Antarctic produced convincing evidence that the ozone hole was indeed caused by chlorine and bromine from manmade organohalogens, the Montreal Protocol was strengthened at a 1990 meeting in London. The participants agreed to phase out CFCs and halons entirely (aside from a very small amount marked for certain "essential" uses, such as asthma inhalers) by 2000. At a 1992 meeting in Copenhagen, the phase out date was moved up to 1996. It has been suggested that this article or section be merged into Metered-dose inhaler. ...


To some extent, CFCs have been replaced by the less damaging hydro-chloro-fluoro-carbons (HCFCs), although concerns remain regarding HCFCs also. In some applications, hydro-fluoro-carbons (HFCs) have been used to replace CFCs. HFCs, which contain no chlorine or bromine, do not contribute at all to ozone depletion although they are potent greenhouse gases. The best known of these compounds is probably HFC-134a (R-134a), which in the United States has largely replaced CFC-12 (R-12) in automobile air conditioners. In laboratory analytics (a former "essential" use) the ozone depleting substances can be replaced with various other solvents.[28] Hydrochlorofluorocarbons (HCFCs) is one of a class of fluorocarbon compounds that are used primarily as chlorofluorocarbon (CFC) substitutes. ... HFC may stand for: Hydrofluorocarbon Hybrid Fibre Coaxial Highly Flamible Cow Cow is a communist from Romania who cant tell the difference between a pound and a euro. ... 1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane or R-134a, is a refrigerant that has zero ozone depletion potential and thermodynamic properties similar to R-12. ... R-phrases S-phrases , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Dichlorodifluoromethane (R-12), usually sold under the brand name Freon-12, is a chlorofluorocarbon halomethane, commonly known as CFC, used as a refrigerant and...


Ozone Diplomacy, by Richard Benedick (Harvard University Press, 1991) gives a detailed account of the negotiation process that led to the Montreal Protocol. Pielke and Betsill provide an extensive review of early US government responses to the emerging science of ozone depletion by CFCs.


Current events and future prospects of ozone depletion

Ozone-depleting gas trends
Ozone-depleting gas trends

Since the adoption and strengthening of the Montreal Protocol has led to reductions in the emissions of CFCs, atmospheric concentrations of the most significant compounds have been declining. These substances are being gradually removed from the atmosphere. By 2015, the Antarctic ozone hole would have reduced by only 1 million km² out of 25 (Newman et al., 2004); complete recovery of the Antarctic ozone layer will not occur until the year 2050 or later. Work has suggested that a detectable (and statistically significant) recovery will not occur until around 2024, with ozone levels recovering to 1980 levels by around 2068.[29] Download high resolution version (1139x1577, 23 KB)CFC gas trends and equivalent chlorine effect. ... Download high resolution version (1139x1577, 23 KB)CFC gas trends and equivalent chlorine effect. ...


There is a slight caveat to this, however. Global warming from CO2 is expected to cool the stratosphere.[citation needed] This, in turn, would lead to a relative increase in ozone depletion and the frequency of ozone holes. The effect may not be linear; ozone holes form because of polar stratospheric clouds; the formation of polar stratospheric clouds has a temperature threshold above which they will not form; cooling of the Arctic stratosphere might lead to Antarctic-ozone-hole-like conditions. But at the moment this is not clear. Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ...


Even though the stratosphere as a whole is cooling, high-latitude areas may become increasingly predisposed to springtime stratospheric warming events as weather patterns change in response to higher greenhouse gas loading.[citation needed] This would cause PSCs to disappear earlier in the season, and may explain why Antarctic ozone hole seasons have tended to end somewhat earlier since 2000 as compared with the most prolonged ozone holes of the 1990s. Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ...


The decrease in ozone-depleting chemicals has also been significantly affected by a decrease in bromine-containing chemicals. The data suggest that substantial natural sources exist for atmospheric methyl bromide (CH3Br).[30] Bromo redirects here. ... The chemical compound bromomethane is an organic halogen compound with formula BrCH3. ...


The 2004 ozone hole ended in November 2004, daily minimum stratospheric temperatures in the Antarctic lower stratosphere increased to levels that are too warm for the formation of polar stratospheric clouds (PSCs) about 2 to 3 weeks earlier than in most recent years.[31]


The Arctic winter of 2005 was extremely cold in the stratosphere; PSCs were abundant over many high-latitude areas until dissipated by a big warming event, which started in the upper stratosphere during February and spread throughout the Arctic stratosphere in March. The size of the Arctic area of anomalously low total ozone in 2004-2005 was larger than in any year since 1997. The predominance of anomalously low total ozone values in the Arctic region in the winter of 2004-2005 is attributed to the very low stratospheric temperatures and meteorological conditions favorable for ozone destruction along with the continued presence of ozone destroying chemicals in the stratosphere.[32]


A 2005 IPCC summary of ozone issues observed that observations and model calculations suggest that the global average amount of ozone depletion has now approximately stabilized. Although considerable variability in ozone is expected from year to year, including in polar regions where depletion is largest, the ozone layer is expected to begin to recover in coming decades due to declining ozone-depleting substance concentrations, assuming full compliance with the Montreal Protocol.[33] IPCC is science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the risk of human-induced climate change. The Panel is open to all...


Temperatures during the Arctic winter of 2006 stayed fairly close to the long-term average until late January, with minimum readings frequently cold enough to produce PSCs. During the last week of January, however, a major warming event sent temperatures well above normal — much too warm to support PSCs. By the time temperatures dropped back to near normal in March, the seasonal norm was well above the PSC threshold.[34] Preliminary satellite instrument-generated ozone maps show seasonal ozone buildup slightly below the long-term means for the Northern Hemisphere as a whole, although some high ozone events have occurred.[35] During March 2006, the Arctic stratosphere poleward of 60 degrees North Latitude was free of anomalously low ozone areas except during the three-day period from March 17 to 19 when the total ozone cover fell below 300 DU over part of the North Atlantic region from Greenland to Scandinavia.[36] is the 76th day of the year (77th in leap years) in the Gregorian calendar. ...


The area where total column ozone is less than 220 DU (the accepted definition of the boundary of the ozone hole) was relatively small until around 20 August 2006. Since then the ozone hole area increased rapidly, peaking at 29 million km² September 24. In October 2006, NASA reported that the year's ozone hole set a new area record with a daily average of 26 million km² between 7 September and 13 October 2006; total ozone thicknesses fell as low as 85 DU on October 8. The two factors combined, 2006 sees the worst level of depletion in recorded ozone history. The depletion is attributed to the temperatures above the Antarctic reaching the lowest recording since comprehensive records began in 1979.[37][38] is the 232nd day of the year (233rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 267th day of the year (268th in leap years) in the Gregorian calendar. ... For other uses, see NASA (disambiguation). ... is the 250th day of the year (251st in leap years) in the Gregorian calendar. ... is the 286th day of the year (287th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 281st day of the year (282nd in leap years) in the Gregorian calendar. ...


The Antarctic ozone hole is expected to continue for decades. Ozone concentrations in the lower stratosphere over Antarctica will increase by 5%–10% by 2020 and return to pre-1980 levels by about 2060–2075, 10–25 years later than predicted in earlier assessments. This is because of revised estimates of atmospheric concentrations of Ozone Depleting Substances — and a larger predicted future usage in developing countries. Another factor which may aggravate ozone depletion is the draw-down of nitrogen oxides from above the stratosphere due to changing wind patterns.[39]


History of the research

The basic physical and chemical processes that lead to the formation of an ozone layer in the earth's stratosphere were discovered by Sydney Chapman in 1930. These are discussed in the article Ozone-oxygen cycle — briefly, short-wavelength UV radiation splits an oxygen (O2) molecule into two oxygen (O) atoms, which then combine with other oxygen molecules to form ozone. Ozone is removed when an oxygen atom and an ozone molecule "recombine" to form two oxygen molecules, i.e. O + O3 → 2O2. In the 1950s, David Bates and Marcel Nicolet presented evidence that various free radicals, in particular hydroxyl (OH) and nitric oxide (NO), could catalyze this recombination reaction, reducing the overall amount of ozone. These free radicals were known to be present in the stratosphere, and so were regarded as part of the natural balance – it was estimated that in their absence, the ozone layer would be about twice as thick as it currently is. Sir Sydney Chapman (politician) Sydney Chapman (astronomer) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Ozone-oxygen cycle in the ozone layer. ...


In 1970 Prof. Paul Crutzen pointed out that emissions of nitrous oxide (N2O), a stable, long-lived gas produced by soil bacteria, from the earth's surface could affect the amount of nitric oxide (NO) in the stratosphere. Crutzen showed that nitrous oxide lives long enough to reach the stratosphere, where it is converted into NO. Crutzen then noted that increasing use of fertilizers might have led to an increase in nitrous oxide emissions over the natural background, which would in turn result in an increase in the amount of NO in the stratosphere. Thus human activity could have an impact on the stratospheric ozone layer. In the following year, Crutzen and (independently) Harold Johnston suggested that NO emissions from supersonic aircraft, which fly in the lower stratosphere, could also deplete the ozone layer. Paul J. Crutzen (December 3rd, 1933 - ) is a Dutch nobel prize winning atmospheric chemist. ... Fertilizers are chemicals given to plants with the intention of promoting growth; they are usually applied either via the soil or by foliar spraying. ... A United States Navy F/A-18E/F Super Hornet in transonic flight. ... Flying machine redirects here. ...


The Rowland-Molina hypothesis

In 1974 Frank Sherwood Rowland, Chemistry Professor at the University of California at Irvine, and his postdoctoral associate Mario J. Molina suggested that long-lived organic halogen compounds, such as CFCs, might behave in a similar fashion as Crutzen had proposed for nitrous oxide. James Lovelock (most popularly known as the creator of the Gaia hypothesis) had recently discovered, during a cruise in the South Atlantic in 1971, that almost all of the CFC compounds manufactured since their invention in 1930 were still present in the atmosphere. Molina and Rowland concluded that, like N2O, the CFCs would reach the stratosphere where they would be dissociated by UV light, releasing Cl atoms. (A year earlier, Richard Stolarski and Ralph Cicerone at the University of Michigan had shown that Cl is even more efficient than NO at catalyzing the destruction of ozone. Similar conclusions were reached by Michael McElroy and Steven Wofsy at Harvard University. Neither group, however, had realized that CFC's were a potentially large source of stratospheric chlorine — instead, they had been investigating the possible effects of HCl emissions from the Space Shuttle, which are very much smaller.) Frank Sherwood Rowland (born June 28, 1927) is a Nobel laureate and a professor of chemistry at the University of California, Irvine. ... Mario José Molina Henríquez (born March 19, 1943) was awarded the 1995 Nobel Prize in Chemistry for his role in elucidating the threat to the Earths ozone layer of chlorofluorocarbon gases (or CFCs). ... CFC, cfc, or Cfc may stand for: Chlorofluorocarbon : a class of chemical compounds known to inflict great damage to the ozone layer. ... Dr. James Ephraim Lovelock, CH, CBE, FRS (born 26 July 1919) is an independent scientist, author, researcher, environmentalist, and futurologist who lives in Cornwall, in the south west of Great Britain. ... For other uses, see Gaia. ... Ralph J. Cicerone is an American atmospheric scientist, a former chancellor of UC Irvine, and currently president of the National Academy of Sciences. ...


The Rowland-Molina hypothesis was strongly disputed by representatives of the aerosol and halocarbon industries. The Chair of the Board of DuPont was quoted as saying that ozone depletion theory is "a science fiction tale...a load of rubbish...utter nonsense".[27] Robert Abplanalp, the President of Precision Valve Corporation (and inventor of the first practical aerosol spray can valve), wrote to the Chancellor of UC Irvine to complain about Rowland's public statements (Roan, p 56.) Nevertheless, within three years most of the basic assumptions made by Rowland and Molina were confirmed by laboratory measurements and by direct observation in the stratosphere. The concentrations of the source gases (CFC's and related compounds) and the chlorine reservoir species (HCl and ClONO2) were measured throughout the stratosphere, and demonstrated that CFCs were indeed the major source of stratospheric chlorine, and that nearly all of the CFCs emitted would eventually reach the stratosphere. Even more convincing was the measurement, by James G. Anderson and collaborators, of chlorine monoxide (ClO) in the stratosphere. ClO is produced by the reaction of Cl with ozone — its observation thus demonstrated that Cl radicals not only were present in the stratosphere but also were actually involved in destroying ozone. McElroy and Wofsy extended the work of Rowland and Molina by showing that Bromine atoms were even more effective catalysts for ozone loss than chlorine atoms and argued that the brominated organic compounds known as halons, widely used in fire extinguishers, were a potentially large source of stratospheric bromine. In 1976 the U.S. National Academy of Sciences released a report which concluded that the ozone depletion hypothesis was strongly supported by the scientific evidence. Scientists calculated that if CFC production continued to increase at the going rate of 10% per year until 1990 and then remain steady, CFCs would cause a global ozone loss of 5 to 7% by 1995, and a 30 to 50% loss by 2050. In response the United States, Canada, Sweden and Norway banned the use of CFCs in aerosol spray cans in 1978. However, subsequent research, summarized by the National Academy in reports issued between 1979 and 1984, appeared to show that the earlier estimates of global ozone loss had been too large.[citation needed] Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms: fluorine, chlorine, bromine or iodine. ... Dupont, DuPont, Du Pont, or du Pont may refer to: // E.I. du Pont de Nemours and Company (DuPont), the worlds second largest chemical company Du Pont Motors Gilbert Dupont, a French stock brokerage part of retail banking network Crédit du Nord ST Dupont, a French manufacturer of... Robert Henry (Bob) Abplanalp (April 4, 1922, New York, New York - August 30, 2003, Bronxville, New York) was a Swiss-American inventor who invented the aerosol valve[1], the founder of Precision Valve Corporation and a political activist. ... The University of California, Irvine is a public, coeducational university situated in suburban Irvine, California. ... Halon 1211 and Halon 1301 are special-purpose fire extiguishing agents that were banned by the Montreal Protocol. ...


The Ozone Hole

The discovery of the Antarctic "ozone hole" by British Antarctic Survey scientists Farman, Gardiner and Shanklin (announced in a paper in Nature in May 1985) came as a shock to the scientific community, because the observed decline in polar ozone was far larger than anyone had anticipated.[citation needed] Satellite measurements showing massive depletion of ozone around the south pole were becoming available at the same time. However, these were initially rejected as unreasonable by data quality control algorithms (they were filtered out as errors since the values were unexpectedly low); the ozone hole was detected only in satellite data when the raw data was reprocessed following evidence of ozone depletion in in situ observations. When the software was rerun without the flags, the ozone hole was seen as far back as 1976.[40] BAS headquarters The British Antarctic Survey (BAS), formerly the Falkland Islands Dependencies Survey (FIDS), is an institute of the Natural Environment Research Council, and has, for the last fifty years, undertaken the majority of Britains scientific research on and around the Antarctic continent. ... Nature is a prominent scientific journal, first published on 4 November 1869. ... For other uses, see South Pole (disambiguation). ...


Susan Solomon, an atmospheric chemist at the National Oceanic and Atmospheric Administration (NOAA), proposed that chemical reactions on polar stratospheric clouds (PSCs) in the cold Antarctic stratosphere caused a massive, though localized and seasonal, increase in the amount of chlorine present in active, ozone-destroying forms. The polar stratospheric clouds in Antarctica are only formed when there are very low temperatures, as low as -80 degrees C, and early spring conditions. In such conditions the ice crystals of the cloud provide a suitable surface for conversion of unreactive chlorine compounds into reactive chlorine compounds which can deplete ozone easily. Susan Solomon (born 1956 in Chicago)[1] is an atmospheric chemist working for the National Oceanic and Atmospheric Administration. ... Polar stratospheric clouds (PSCs), also known as nacreous clouds, are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 metres (50,000–80,000 ft). ... For other uses, see Celsius (disambiguation). ...


Moreover the polar vortex formed over Antarctica is very tight and the reaction which occurs on the surface of the cloud crystals is far different from when it occurs in atmosphere. These conditions have led to ozone hole formation in Antarctica. This hypothesis was decisively confirmed, first by laboratory measurements and subsequently by direct measurements, from the ground and from high-altitude airplanes, of very high concentrations of chlorine monoxide (ClO) in the Antarctic stratosphere.[citation needed]


Alternative hypotheses, which had attributed the ozone hole to variations in solar UV radiation or to changes in atmospheric circulation patterns, were also tested and shown to be untenable.[citation needed]


Meanwhile, analysis of ozone measurements from the worldwide network of ground-based Dobson spectrophotometers led an international panel to conclude that the ozone layer was in fact being depleted, at all latitudes outside of the tropics.[citation needed] These trends were confirmed by satellite measurements. As a consequence, the major halocarbon producing nations agreed to phase out production of CFCs, halons, and related compounds, a process that was completed in 1996. Crutzen, Molina, and Rowland were awarded the 1995 Nobel Prize in Chemistry for their work on stratospheric ozone.


Since 1981 the United Nations Environment Programme has sponsored a series of reports on scientific assessment of ozone depletion. The most recent is from 2007 where satellite measurements have shown the hole in the ozone layer is recovering and is now the smallest it has been for about a decade[10]. Klaus Töpfer, former UNEP Exec. ... Scientific Assessment of Ozone Depletion is a sequence of reports sponsored by WMO/UNEP. The most recent is the 2002 report. ...


Controversy regarding ozone science and policy

That ozone depletion takes place is not seriously disputed in the scientific community.[41] There is a consensus among atmospheric physicists and chemists that the scientific understanding has now reached a level where countermeasures to control CFC emissions are justified, although the decision is ultimately one for policy-makers.


Despite this consensus, the science behind ozone depletion remains complex, and some who oppose the enforcement of countermeasures point to some of the uncertainties. For example, although increased UVB has been shown to constitute a melanoma risk, it has been difficult for statistical studies to establish a direct link between ozone depletion and increased rates of melanoma. Although melanomas did increase significantly during the period 1970–1990, it is difficult to separate reliably the effect of ozone depletion from the effect of changes in lifestyle factors (e.g., increasing rates of air travel).


Ozone depletion and global warming

Although they are often interlinked in the mass media, the connection between global warming and ozone depletion is not strong. There are four areas of linkage: Popular press redirects here; note that the University of Wisconsin Press publishes under the imprint The Popular Press. Mass media is a term used to denote a section of the media specifically envisioned and designed to reach a very large audience such as the population of a nation state. ...

  • The same CO2 radiative forcing that produces near-surface global warming is expected to cool the stratosphere.[citation needed] This cooling, in turn, is expected to produce a relative increase in polar ozone (O3) depletion and the frequency of ozone holes.
Radiative forcing from various greenhouse gases and other sources
Radiative forcing from various greenhouse gases and other sources
  • Conversely, ozone depletion represents a radiative forcing of the climate system. There are two opposing effects: Reduced ozone causes the stratosphere to absorb less solar radiation, thus cooling the stratosphere while warming the troposphere; the resulting colder stratosphere emits less long-wave radiation downward, thus cooling the troposphere. Overall, the cooling dominates; the IPCC concludes that "observed stratospheric O3 losses over the past two decades have caused a negative forcing of the surface-troposphere system"[42] of about −0.15 ± 0.10 watts per square meter (W/m²).[43]
  • One of the strongest predictions of the greenhouse effect theory is that the stratosphere will cool.[citation needed] Although this cooling has been observed, it is not trivial to separate the effects of changes in the concentration of greenhouse gases and ozone depletion since both will lead to cooling. However, this can be done by numerical stratospheric modeling. Results from the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory show that above 20 km (12.4 miles), the greenhouse gases dominate the cooling.[44]
  • Ozone depleting chemicals are also greenhouse gases. The increases in concentrations of these chemicals have produced 0.34 ± 0.03 W/m² of radiative forcing, corresponding to about 14% of the total radiative forcing from increases in the concentrations of well-mixed greenhouse gases.[43]
  • The long term modeling of the process, its measurement, study, design of theories and testing take decades to both document, gain wide acceptance, and ultimately become the dominant paradigm. Several theories about the destruction of ozone, were hyphtosized in the 1980s, published in the late 1990s, and are currently being proven. Dr Drew Schindell, and Dr Paul Newman, NASA Goddard, proposed a theory in the late 1990s, using a SGI Origin 2000 supercomputer, that modeled ozone destruction, accounted for 78% of the ozone destroyed. Further refinement of that model, accounted for 89% of the ozone destroyed, but pushed back the estimated recovery of the ozone hole from 75 years to 150 years. (An important part of that model is the lack of staratospheric flight due to depletion of fossil fuels. )

Atmosphere diagram showing stratosphere. ... For other uses, see Ozone (disambiguation). ... Image File history File links Radiative-forcings. ... Image File history File links Radiative-forcings. ... The generalised concept of radiative forcing in climate science is any change in the radiation (heat) entering the climate system or changes in radiatively active gases. ... Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ... Atmosphere diagram showing the mesosphere and other layers. ... For other uses, see Ozone (disambiguation). ... For other uses, see Watt (disambiguation). ... Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ... The National Oceanic and Atmospheric Administration (NOAA) is a scientific agency of the United States Department of Commerce focused on the conditions of the oceans and the atmosphere. ... The Geophysical Fluid Dynamics Laboratory (GFDL) is a laboratory in the National Oceanic and Atmospheric Administration (NOAA)/Office of Oceanic and Atmospheric Research (OAR). ...

Misconceptions about ozone depletion

A few of the more common misunderstandings about ozone depletion are addressed briefly here; more detailed discussions can be found in the ozone-depletion FAQ.


CFCs are "too heavy" to reach the stratosphere

It is sometimes stated that since CFC molecules are much heavier than nitrogen or oxygen, they cannot reach the stratosphere in significant quantities.[45] But atmospheric gases are not sorted by weight; the forces of wind (turbulence) are strong enough to fully intermix gases in the atmosphere. CFCs are heavier than air, but just like argon, krypton and other heavy gases with a long lifetime, they are uniformly distributed throughout the turbosphere and reach the upper atmosphere.[46] General Name, symbol, number argon, Ar, 18 Chemical series noble gases Group, period, block 18, 3, p Appearance colorless Standard atomic weight 39. ... For other uses, see Krypton (disambiguation). ... The turbosphere (or homosphere) is that portion of the atmosphere that is sufficiently well-stirred by atmospheric motion that long-lived gases are well-mixed and do not appreciably separate by weight. ...


Man-made chlorine is insignificant compared to natural sources

Another objection occasionally voiced is that It is generally agreed that natural sources of tropospheric chlorine (volcanoes, ocean spray, etc.) are four to five orders of magnitude larger than man-made sources. While strictly true, tropospheric chlorine is irrelevant; it is stratospheric chlorine that matters to ozone depletion. Chlorine from ocean spray is soluble and thus is washed out by rainfall before it reaches the stratosphere. CFCs, in contrast, are insoluble and long-lived, which allows them to reach the stratosphere. Even in the lower atmosphere there is more chlorine present in the form of CFCs and related haloalkanes than there is in HCl from salt spray, and in the stratosphere the halocarbons dominate overwhelmingly.[47] Only one of these halocarbons, methyl chloride, has a predominantly natural source, and it is responsible for about 20 percent of the chlorine in the stratosphere; the remaining 80% comes from manmade compounds. Tetrafluoroethane (a haloalkane) is a clear liquid which boils well below room temperature (as seen here) and can be extracted from common canned air canisters by simply inverting them during use. ...


Very large volcanic eruptions can inject HCl directly into the stratosphere, but direct measurements[48] have shown that their contribution is small compared to that of chlorine from CFCs. A similar erroneous assertion is that soluble halogen compounds from the volcanic plume of Mount Erebus on Ross Island, Antarctica are a major contributor to the Antarctic ozone hole.[citation needed] Mount Erebus in Antarctica is the southernmost active volcano on Earth. ...


An ozone hole was first observed in 1956

G.M.B. Dobson (Exploring the Atmosphere, 2nd Edition, Oxford, 1968) mentioned that when springtime ozone levels over Halley Bay were first measured, he was surprised to find that they were ~320 DU, about 150 DU below spring levels, ~450 DU, in the Arctic. These, however, were the pre-ozone hole normal climatological values. What Dobson describes is essentially the baseline from which the ozone hole is measured: actual ozone hole values are in the 150–100 DU range. Gordon Miller Bourne Dobson FRS (25 February 1889 - 11 March 1976) was a British physicist and meteorologist who did important work on ozone. ... Halley 5, Winter 1999 Halley Research Station, located at , on the Brunt Ice Shelf floating on the Weddell Sea in Antarctica is a British research facility dedicated to the study of the Earths atmosphere. ...


The discrepancy between the Arctic and Antarctic noted by Dobson was primarily a matter of timing: during the Arctic spring ozone levels rose smoothly, peaking in April, whereas in the Antarctic they stayed approximately constant during early spring, rising abruptly in November when the polar vortex broke down.


The behavior seen in the Antarctic ozone hole is completely different. Instead of staying constant, early springtime ozone levels suddenly drop from their already low winter values, by as much as 50%, and normal values are not reached again until December.[49]


If the theory were correct, the ozone hole should be above the sources of CFCs

CFCs are well mixed in the troposphere and the stratosphere. The reason the ozone hole occurs above Antarctica is not because there are more CFCs there but because the low temperatures allow polar stratospheric clouds to form.[50] There have been anomalous discoveries of significant, serious, localized "holes" above other parts of the globe.[51] Atmosphere diagram showing the mesosphere and other layers. ... Atmosphere diagram showing stratosphere. ...


The "ozone hole" is a hole in the ozone layer

When the "ozone hole" forms, essentially all of the ozone in the lower stratosphere is destroyed. The upper stratosphere is much less affected, however, so that the overall amount of ozone over the continent declines by 50 percent or more. The ozone hole does not go all the way through the layer; on the other hand, it is not a uniform 'thinning' of the layer either. It's a "hole" in the sense of "a hole in the ground", a depression, not in the sense of "a hole in the windshield."


World Ozone Day

In 1994, the United Nations General Assembly voted to designate September 16 as "World Ozone Day", to commemorate the signing of the Montreal Protocol on that date in 1987. Spanish president in the General Assembly in New York Org type: Principal Organ Acronyms: GA, UNGA Head: President of the UN General Assembly As of 18 September 2007 Srgjan Kerim former Yugoslav Republic of Macedonia Status: Active Established: 1945 Website: www. ... is the 259th day of the year (260th in leap years) in the Gregorian calendar. ... The largest Antarctic ozone hole recorded as of September 2006 For other similarly-named agreements, see Montreal Convention (disambiguation). ...


See also

Ozone-oxygen cycle in the ozone layer. ... The largest Antarctic ozone hole recorded as of September 2006 For other similarly-named agreements, see Montreal Convention (disambiguation). ... Scientific Assessment of Ozone Depletion is a sequence of reports sponsored by WMO/UNEP. The most recent is the 2002 report. ... For other uses, see CFC (disambiguation). ... Melanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye (see uveal melanoma). ... Skin cancer is a malignant growth on the skin which can have many causes. ... Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ... For other uses, see Ultraviolet (disambiguation). ... Categories: Pages needing attention | Animal stubs ... Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ... Ross Ice Shelf An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. ... The atmospheric window refers to those parts of the electromagnetic spectrum that are, with the earths atmosphere in its natural state, not absorbed at all. ...

References

  1. ^ Part III. The Science of the Ozone Hole. Retrieved on 2007-03-05.
  2. ^ Stratospheric ozone: an electronic textbook, Chapter 5, Section 4.2.8, [1]
  3. ^ Stratospheric Ozone Depletion by Chlorofluorocarbons (Nobel Lecture) - Encyclopedia of Earth
  4. ^ Nature
  5. ^ http://pubs.acs.org/cgi-bin/abstract.cgi/jpcafh/2007/111/i20/abs/jp067660w.html
  6. ^ http://www.wmo.ch/pages/publications/bulletin/ozone_en.html
  7. ^ The Ozone Hole Tour: Part II. Recent Ozone Depletion
  8. ^ World Meteorological Organization (WMO)
  9. ^ U.S. EPA: Ozone Depletion
  10. ^ Climate Change 2001: The Scientific Basis
  11. ^ [2]
  12. ^ http://www.encyclopedia.com/doc/1E1-chlorofl.html
  13. ^ Antarctic Ozone Hole
  14. ^ Antarctic ozone-depletion FAQ, section 7
  15. ^ [3]
  16. ^ http://www.informaworld.com/smpp/content~content=a723976621~db=all
  17. ^ a b http://www.gcrio.org/CONSEQUENCES/summer95/impacts.html Consequences (vol. 1, No. 2) - Impacts of a Projected Depletion of the Ozone Layer
  18. ^ Wavelengths effective in induction of malignant me...[Proc Natl Acad Sci U S A. 1993] - PubMed Result
  19. ^ Fears et al, Cancer Res. 2002, 62(14):3992–6
  20. ^ Abarca, Jaime F. & Casiccia, Claudio C. (2002) Skin cancer and ultraviolet-B radiation under the Antarctic ozone hole: southern Chile, 1987-2000. Photodermatology, Photoimmunology & Photomedicine 18 (6), 294–302 [4]
  21. ^ JAMA - Sunlight Exposure and Risk of Lens Opacities in a Population-Based Study: The Salisbury Eye Evaluation Project, August 26, 1998, West et al. 280 (8): 714
  22. ^ Ultraviolet light exposure and lens opacities: the Beaver Dam Eye Study. - Cruickshanks et al. 82 (12): 1658 - American Journal of Public Health
  23. ^ Racial differences in lens opacities: the Salisbury Eye Evaluation (SEE) project
  24. ^ Prevalence of lens opacities in the Barbados Eye S...[Arch Ophthalmol. 1997] - PubMed Result
  25. ^ R. P. Sinha; S. C. Singh and D.-P. Häder (1999). "Photoecophysiology of cyanobacteria". Journal of Photochemistry and Photobiology 3: 91–101. 
  26. ^ NewsFactor Network
  27. ^ a b http://archive.greenpeace.org/ozone/greenfreeze/moral97/6dupont.html
  28. ^ Use of Ozone Depleting Substances in Laboratories. TemaNord 516/2003. [5]
  29. ^ Newman, P. A., Nash, E. R., Kawa, S. R., Montzka, S. A. and Schauffler, S. M (2006). "When will the Antarctic ozone hole recover?". Geophysical Research Letters 33: L12814. doi:10.1029/2005GL025232. 
  30. ^ World Meteorological Organization (WMO)
  31. ^ World Meteorological Organization (WMO)
  32. ^ CPC - Stratosphere: Winter Bulletins
  33. ^ [6]
  34. ^ Available Annual NCEP data
  35. ^ Select ozone maps, individual sources
  36. ^ Index of /products/stratosphere/sbuv2to/archive/nh
  37. ^ Ozone Hole Watch
  38. ^ http://www.theregister.co.uk/2006/10/03/ozone_depletion
  39. ^ CNW Group | CANADIAN SPACE AGENCY | Canada's SCISAT satellite explains 2006 ozone-layer depletion
  40. ^ Ozone Depletion, History and politics accessed November 18, 2007.
  41. ^ ozone hole: Definition and Much More from Answers.com
  42. ^ Climate Change 2001: Working Group I: The Scientific Basis. Intergovernmental Panel on Climate Change Work Group I Chapter 6.4 (2001). Retrieved on 2007-03-04.
  43. ^ a b (2005). "IPCC/TEAP Special Report on Safeguarding the Ozone Layer and the Global Climate System: Issues Related to Hydrofluorocarbons and Perfluorocarbons (summary for policy makers)" (PDF). International Panel on Climate Change and Technology and Economic Assessment Panel. Retrieved on 2007-03-04.
  44. ^ The Relative Roles of Ozone and Other Greenhouse Gases in Climate Change in the Stratosphere. Geophysical Fluid Dynamics Laboratory (2007-02-29). Retrieved on 2007-03-04.
  45. ^ Phoenix - News - FREON EASY
  46. ^ FAQ, part I, section 1.3.
  47. ^ ozone-depletion FAQ, Part II, section 4.3
  48. ^ ozone-depletion FAQ, Part II, section 4.4
  49. ^ ozone-depletion FAQ, Part III, section 6
  50. ^ ozone-depletion FAQ, Antarctic
  51. ^ ozone hole: Definition and Much More from Answers.com

Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... This article is about the day. ... is the 238th day of the year (239th in leap years) in the Gregorian calendar. ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... is the 322nd day of the year (323rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... IPCC is the science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), to evaluate the risk of climate change brought on by humans, based mainly on... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the risk of human-induced climate change. The Panel is open to all members of the WMO and UNEP. Its... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... February 29 is a day added into a leap year of the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 63rd day of the year (64th in leap years) in the Gregorian calendar. ...

Nontechnical books

  • Dotto, Lydia and Schiff, Harold (1978). The Ozone War. Doubleday. ISBN 0-385-12927-0
  • Roan, Sharon (1990). Ozone Crisis, the 15 Year Evolution of a Sudden Global Emergency. Wiley. ISBN 0-471-52823-4
  • Cagin, Seth and Dray, Phillip (1993). Between Earth and Sky: How CFCs Changed Our World and Endangered the Ozone Layer. Pantheon. ISBN 0-679-42052-5

Books on public policy issues

  • Benedick, Richard E. (1991). Ozone Diplomacy. Harvard University Press. ISBN 0-674-65001-8 (Ambassador Benedick was the Chief U.S. Negotiator at the meetings that resulted in the Montreal Protocol.)
  • Litfin, Karen T. (1994). Ozone Discourses. Columbia University Press. ISBN 0-231-08137-5

Research articles

  • Newman, P. A., Kawa, S. R. and Nash, E. R. (2004). "On the size of the Antarctic ozone hole?". Geophysical Research Letters 31: L12814. doi:10.1029/2004GL020596. 
  • E. C. Weatherhead, S. B. Andersen (2006). "The search for signs of recovery of the ozone layer". Nature 441: 39-45. doi:10.1038/nature04746. 

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

External links

  • The Ozone Hole
    • Ozone Hole 2007
    • History Of The Ozone Hole
  • Lessons from the Montreal Protocol from the Encyclopedia of Earth
  • NASA
    • New News About Ozone Recovery
    • 20 questions on Ozone
    • Ozone Hole Watch (Images, Data, and Information Updated Daily)
    • Ozone Resource Page
  • NOAA
    • Stratospheric Ozone Webpage
    • Stratospheric ozone depletion (Antarctic, Arctic, and global)
    • NOAA's Ozone and Water Vapor Group
    • Scientific Assessment of Ozone Depletion: 1998 - by WMO, UNEP and NOAA
  • The Ozone Tour at the Centre for Atmospheric Science, University of Cambridge
  • The Ozone Depletion Story at the Natural Resources Defense Council
  • The Nobel Prize in Chemistry 1995 - includes links to biographies of Crutzen, Molina, and Rowland and to their Nobel Lectures.
  • Stratospheric Ozone Depletion by Chlorofluorocarbons (Nobel Lecture) - Article by Nobel laureate Rowland at the Encyclopedia of Earth
  • Ozone Depletion - a resource for both adults and schools
  • Impacts of a Projected Depletion of the Ozone Layer
  • The Skeptics vs. the Ozone Hole
  • 1991 Science News Article about Emergency Ozone Hole Repair
  • No Quick Fix for the Ozone Hole - An improved computer model predicts the recovery won't occur until 2068

The World Meteorological Organization (WMO) is an intergovernmental organization with a membership of 187 Member States and Territories. ... Klaus Töpfer, UNEP Exec. ... The National Oceanic and Atmospheric Administration (NOAA) is a scientific agency of the United States Department of Commerce focused on the conditions of the oceans and the atmosphere. ... The Natural Resources Defense Council (NRDC) [1] is a leftist, New York City-based, non-profit, non-partisan environmental advocacy group, with offices in Washington, D.C., San Francisco, and Los Angeles. ... Paul J. Crutzen (December 3rd, 1933 - ) is a Dutch nobel prize winning atmospheric chemist. ... Mario José Molina Henríquez (born March 19, 1943) was awarded the 1995 Nobel Prize in Chemistry for his role in elucidating the threat to the Earths ozone layer of chlorofluorocarbon gases (or CFCs). ... Frank Sherwood Rowland (born June 28, 1927) is a Nobel laureate and a professor of chemistry at the University of California, Irvine. ... Frank Sherwood Rowland (born June 28, 1927) is a Nobel laureate and a professor of chemistry at the University of California, Irvine. ... // Introduction The Encyclopedia of Earth is an electronic reference about the Earth, its natural environments, and their interaction with society. ... Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 450,000 years For current global climate change, see Global warming. ... The temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. ... Instrumental global surface temperature measurements; see also [http://www. ... Comparison of ground based (blue) and satellite based (red: UAH; green: RSS) records of temperature variations since 1979. ... The temperature record of the past 1000 years describes the reconstruction of temperature for the last 1000 years on the Northern Hemisphere. ... The website of the National Oceanic and Atmospheric Administration contains detailed data of the annual land and ocean temperature since 1880. ... This article is devoted to temperature changes in Earths environment as determined from geologic evidence on multi-million to billion (109) year time scales. ... National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. ... Look up anthropogenic in Wiktionary, the free dictionary. ... In common with many other forms of transport, aircraft engines emit polluting gases, contribute to global warming, and cause noise pollution. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO2 concentration. ... Global dimming is the gradual reduction in the amount of global direct irradiance at the Earths surface that was observed for several decades after the start of systematic measurements in 1950s. ... Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. ... A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ... Top: Increasing atmospheric levels as measured in the atmosphere and ice cores. ... The Keeling Curve is a graph measuring the increase in the levels of carbon dioxide in the atmosphere since 1958. ... Land Use, Land-Use Change and Forestry (LULUCF) is a term often used in climate change topics. ... Tokyo, a case of Urban Heat Island. ... For other uses, see Albedo (disambiguation). ... Cloud forcing (sometimes described as cloud radiative forcing) is the difference between the radiation budget components for average cloud conditions and cloud-free conditions. ... A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator. ... Global cooling in general can refer to a cooling of the Earth. ... Chart of ocean surface temperature anomaly [°C] during the last strong El Niño in December 1997 El Niño and La Niña (also written in English as El Nino and La Nina) are major temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. ... Milankovitch cycles are the collective effect of changes in the Earths movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković. The eccentricity, axial tilt, and precession of the Earths orbit vary in several patterns, resulting in 100,000 year ice age cycles of the... Orbital forcing, or Milankovitch theory, describes the effect on climate of slow changes in the tilt of the Earths axis and shape of the orbit. ... The generalised concept of radiative forcing in climate science is any change in the radiation (heat) entering the climate system or changes in radiatively active gases. ... 400 year history of sunspot numbers. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface, and ice. ... General Circulation Models (GCMs) are a class of computer-driven models for weather forecasting and predicting climate change, where they are commonly called Global Climate Models. ... The politics of global warming looks at the current political issues relating to global warming, as well as the historical rise of global warming as a political issue. ... UNFCCC logo. ... IPCC is the science authority for the UNFCCC The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), to evaluate the risk of climate change brought on by humans, based mainly on... The global warming controversy is a dispute regarding the nature and consequences of global warming. ... This article lists scientists and former scientists who have stated disagreement with one or more of the principal conclusions of the mainstream scientific assessment of global warming. ... This page is non-encyclopedic and represents the editorial views of notably biased publications, such as Newsweek and Mother Jones. ... Graphical description of risks and impacts from global warming from the Third Assessment Report of the Intergovernmental Panel on Climate Change. ... This article or section does not cite any references or sources. ... Fields outside Benambra, Victoria, Australia suffering from drought conditions A drought is an extended period of months or years when a region notes a deficiency in its water supply. ... As recent estimates of the rate of global warming have increased, so have the financial estimates of the damage costs. ... Chart of ocean surface temperature anomaly [°C] during the last strong El Niño in December 1997 El Niño and La Niña (also written in English as El Nino and La Nina) are major temperature fluctuations in surface waters of the tropical Eastern Pacific Ocean. ... A view down the Whitechuck Glacier in North Cascades National Park in 1973 The same view as seen in 2006, where this branch of glacier retreated 1. ... The extinction risk of climate change -- that is, the expected number of species expected to become extinct due to the effects of global warming -- has been estimated in a 2004 Nature study to be between 15 and 37 percent of known species by 2050. ... Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s Ocean acidification is the name given to the ongoing decrease in the pH of the Earths oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. ... Sea level measurements from 23 long tide gauge records in geologically stable environments show a rise of around 20 centimeters per century (2 mm/year). ... Shutdown or slowdown of the thermohaline circulation is a possible effect of global warming. ... Global carbon dioxide emissions 1800–2000 Global average surface temperature 1850 to 2006 Mitigation of global warming involves taking actions aimed at reducing the extent of global warming. ... The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing greenhouse gases that cause climate change. ... CDM directs here. ... Joint implementation (JI) is an arrangement under the Kyoto Protocol allowing industrialised countries with a greenhouse gas reduction commitment (so-called Annex 1 countries) to invest in emission reducing projects in another industrialised country as an alternative to emission reductions in their own countries. ... The European Climate Change Programme (ECCP) was launched in June 2000 by the European Unions European Commission. ... The United Kingdoms Climate Change Programme was launched in November 2000 by the British government in response to its commitment agreed at the 1992 United Nations Conference on Environment and Development (UNCED). ... Crude oil prices, 1994-2007 (not adjusted for inflation) In 2005 the government of Sweden announced their intention to make Sweden the first country to break its dependence on petroleum, natural gas and other ‘fossil raw materials’ by 2020. ... Emissions trading (or cap and trade) is an administrative approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants. ... Emissions trading schemes (also known as ‘cap and trade’ schemes) are one of the policy instruments available for reducing carbon dioxide (CO2) and other greenhouse gases. ... A carbon tax is a tax on energy sources which emit carbon dioxide into the atmosphere. ... Until recently, most carbon offsets were commonly done by planting trees. ... This article deals with carbon credits for international trading. ... A carbon dioxide (CO2) sink is a carbon dioxide reservoir that is increasing in size, and is the opposite of a carbon dioxide source. The main natural sinks are (1) the oceans and (2) plants and other organisms that use photosynthesis to remove carbon from the atmosphere by incorporating it... For the physical concepts, see conservation of energy and energy efficiency. ... Efficient energy use, sometimes simply called energy efficiency, is using less energy to provide the same level of energy service. ... Renewable energy effectively utilizes natural resources such as sunlight, wind, tides and geothermal heat, which are naturally replenished. ... Renewable energy commercialization involves three generations of technologies dating back more than 100 years. ... // Renewable energy development covers the advancement, capacity growth, and use of renewable energy sources by humans. ... The soft energy path is an energy use and development strategy delineated and promoted by some energy experts and activists, such as Amory Lovins and Tom Bender; in Canada, David Suzuki has been a very prominent (if less specialized) proponent. ... The G8 Climate Change Roundtable was formed in January 2005 at the World Economic Forum in Davos. ... The issue of human-caused, or anthropogenic, climate change (global warming) is becoming a central focus of the Green movement. ... Adaptation to global warming covers all actions aimed at reducing the negative effects of global warming. ... This article is about structures for water impoundment. ... The Seven Rila Lakes in Rila, Bulgaria are typical representatives of lakes with glacial origin A glacial lake is a lake with origins in a melted glacier. ... Irrigation is the artificial application of water to the soil usually for assisting in growing crops. ... A rainwater tank is a water tank which is used to collect and store rainwater runoff, typically from rooftops. ... Sustainable development is a socio-ecological process characterized by the fulfilment of human needs while maintaining the quality of the natural environment indefinitely. ... A tornado in central Oklahoma. ... Global carbon dioxide emissions 1800–2000 Global average surface temperature 1850 to 2006 Avoiding Dangerous Climate Change: A Scientific Symposium on Stabilisation of Greenhouse Gases was a 2005 international conference that redefined the link between atmospheric greenhouse gas concentration, and the 2°C (3. ... LADSS or Land Allocation Decision Support System, is an agricultural land use planning tool being developed at The Macaulay Institute. ... This article serves as a glossary of the most common terms and how they are used. ...


  Results from FactBites:
 
Ozone depletion - Wikipedia, the free encyclopedia (5967 words)
Ozone is formed in the stratosphere when oxygen molecules photodissociate after absorbing an ultraviolet photon whose wavelength is shorter than 240 nm.
Most of the ozone that is destroyed is in the lower stratosphere, in contrast to the much smaller ozone depletion through homogeneous gas phase reactions, which occurs primarily in the upper stratosphere.
Because of this uncertainty, it is difficult to estimate the impact of ozone depletion on melanoma incidence.
Ozone depletion :: Emerging Environmental Issues :: United Nations System-Wide EARTHWATCH (1196 words)
Major ozone layer losses are now occurring over the northern hemisphere as well, with serious losses since the winter of 1991-92 and a record hole in 1996 lasting two months that doubled carcinogenic ultraviolet rays over an area covering Scandinavia and extending from Greenland to Western Siberia (WMO, 1996).
Ozone losses in the stratosphere may have caused part of the observed cooling of the lower stratosphere in the polar and upper middle latitudes (about 0.6 degrees centigrade per decade since 1979).
The increase of ozone in the troposphere since pre-industrial times is estimated to have contributed 10 % to 20 % of the warming due to the increase in long-lived greenhouse gases during the same period.
  More results at FactBites »

 
 

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