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depletion of the ozone layer

Overview of the cycle of ozone
The cycle of the ozone layer
Three forms (or allotropes) oxygen are involved in the cycle of ozone and oxygen: the oxygen atoms (O or atomic oxygen), the oxygen gas (O2 or diatomic oxygen) and ozone (O3 or triatomic oxygen). Ozone is formed in the stratosphere when oxygen molecules absorb photodissociate after an ultraviolet photon whose length wavelength is shorter than 240 nm. This produces two oxygen atoms. Atomic oxygen combines with O2 to create O3. Ozone molecules absorb UV light between 310 and 200 nm, after which the ozone layer breaks down into a molecule of O2 and an oxygen atom. The oxygen atom then binds to a molecule oxygen to regenerate the ozone layer. This is an ongoing process that ends when an oxygen atom Gather with an ozone molecule to two molecules O2 O3 O2 O + 2
Global monthly average total ozone.
The layers of the atmosphere (not to scale)
The total amount of ozone in the stratosphere is determined a balance between photochemical production and recombination.
Ozone can be destroyed by a series of free radical catalysts, the most important are hydroxyl radical (OH), nitric oxide radical (NO), atomic chlorine (Cl) and bromine (Br). All these sources are both natural and anthropogenic, at present, most of the OH and NO in the stratosphere is of natural origin, but human activity has significantly increased the levels of chlorine and bromine. These elements are in some stable organic compounds, especially chlorofluorocarbons (CFCs), which can find its way into the stratosphere without being destroyed in the troposphere due to its low reactivity. Once in the stratosphere, Cl and Br atoms are released from parent compounds by the action of ultraviolet light, for example ("H" is the constant Planck,''is the frequency of electromagnetic radiation)
H + + Cl CFCl3 CFCl2
Cl and Br atoms can destroy ozone molecules through a variety of catalytic cycles. The best example of just such a cycle, a chlorine atom reacts with an ozone molecule, taking one oxygen atom with it (forming ClO) and leaving a normal oxygen molecule. Chlorine monoxide (eg, ClO) can react with a second molecule of ozone (O3 ie) to give one another chlorine atom and two oxygen molecules. The shortcut of chemical reactions in the gas phase is:
Cl + O3 ClO + O2
ClO + Cl + 2 O2 O3
The overall effect is a reduction in the amount of ozone. More complex mechanisms have been discovered that leads to destruction of ozone in the stratosphere also lower.
A single chlorine atom will destroy the ozone layer (and thus a catalyst) to a maximum of two years (the time scale for transport to the bottom of the troposphere) were it not for the reactions that remove them from this cycle the formation of reservoir species such as hydrogen chloride (HCl) and chlorine nitrate (ClONO2). On a per atom basis, bromine is more effective than chlorine to destroy ozone, but is much less bromine in the atmosphere today. As a result, chlorine and bromine contribute significantly to global ozone depletion. Laboratory studies have shown that fluorine and iodine atoms participate in analogous catalytic cycles. However, in Earth's stratosphere, fluorine atoms react rapidly with water and methane to form strongly bound HF, while organic molecules that contain iodine react so quickly in the lower atmosphere does not reach the stratosphere in large quantities. In addition, a chlorine atom is capable of reacting with 100,000 ozone molecules. This, plus the amount of chlorine in the atmosphere by chlorofluorocarbons (CFCs) shows the threat CFC annual environmental.
quantitative understanding of the processes of chemical ozone loss
In 2007, research on the breakdown a key molecule in these chemicals that deplete the ozone layer, peroxide, dichloro (Cl2O2), also known as the ClO dimer, questioned the integrity current atmospheric models of polar ozone depletion. The ClO dimer serves as a reservoir of chlorine in the atmosphere. While chlorine is bound in the dimer not available for the catalytic destruction of ozone layer. Photolysis of the dimer produces two ClO molecules that can participate in the catalytic destruction ozone. chlorine nitrate (ClONO2) Another important molecule is a reservoir.
Chemical Jet Propulsion Laboratory of NASA in Pasadena, California, revalued absorption cross section of ClO dimer for which reported an order of magnitude smaller than previously thought in the region between 300 and 350 nm .. This would reduce absorption coefficient implies that chlorine is much less available for the catalytic destruction of ozone in the stratosphere, since most of it remains locked the ClO dimer.
This result prompted further action by different methods, resulting in sections according to age, more resolve the discrepancy. The first report by Chen et al., A, which used a new method to determine the absorption cross section by observing the loss of dimer in a mass spectrometer as a molecular beam is exposed to a UV laser. . This method has the weakness that can be used at wavelengths where there is intense laser sources.
There was another, more recent study shows that major revisions in the model of the ozone layer are not necessary. In addition to the new measures, Papanastasiou, et al. From the Systems Laboratory of the NOAA Earth seen JPL group not adequately account for uncertainty in the modeling of the cross sections, and if done correctly, the error of JPL estimates include other results, although the mean estimate is much lower. Other studies are ongoing and should be published shortly. Preliminary results Anderson Group at Harvard, presented at the AGU Conference in 2009 supported the higher absorption cross sections. These new experiences, driven by the bottom of the JPL have significantly improved our knowledge of the absorption section and the ClO dimer increased our confidence in models of photochemical destruction of ozone.
Observations on the depletion of the ozone layer
The smaller ozone was pronounced in the lower stratosphere. However, the ozone hole is measured more often not in terms of ozone concentrations at these levels (which are usually a few parts per million), but a reduction in the total ozone column a point above the surface of the Earth, which is usually expressed in Dobson units, abbreviated "FROM". Marked decreases in column ozone over Antarctica spring and summer compared to the 1970s and before have been observed using tools such as Total Ozone Mapping Spectrometer (TOMS).
The value lowest TOMS ozone layer each year measured by the ozone hole.
Discounts up to 70% in the ozone column observed in the austral (southern hemisphere) spring over Antarctica and the first report in 1985 (Farman et al. 1985) are ongoing. During the 1990s, total ozone column in September and October were followed by 4.050% below pre-ozone hole. In the Arctic, the amount lost is more variable in years years in Antarctica. The largest decreases, up to 30% are in winter and spring, when the stratosphere is colder.
The reactions occur in polar stratospheric clouds (PSC) play an important role in strengthening the ozone layer. CSP form more easily in the extreme cold of the Antarctic stratosphere. This is why ozone holes first formed, and are deeper, over Antarctica. Early models did not consider private security and predicts a global exhaustion, which explains why the ozone hole over Antarctica was sudden as a surprise to many scientists. [Edit]
In the middle latitudes, it is better to speak of the destruction of the ozone layer, instead of holes. The cuts are about 3% below pre-1980 values of 3560N and about 6% for 3560. In the tropics, there are no significant trends. [Citation needed]
The Ozone depletion also explains much of the reduction observed in the upper troposphere and stratosphere temperatures. The heat source in the stratosphere is the absorption of UV radiation by ozone, which reduces the ozone layer leads to a cooling. Some stratospheric cooling is also expected increase in emissions of greenhouse gases like CO2, but the cooling of the ozone layer seems to be dominant. [Citation needed]
The predictions of ozone levels remain difficult. The Organization World Meteorological Organization Global Ozone Research and Monitoring Projecteport No. 44 to rule in favor of the Montreal Protocol, but notes that ozone loss UNEP's 1994 assessment for the period 19,941,997 overestimated.
Chemicals in the atmosphere
CFCs in the atmosphere
Chlorofluorocarbons (CFCs) were invented by Thomas Midgley in the 1920s. They have been used in air conditioning and refrigeration units, as aerosol propellants in previous years 1980, and in the process of cleaning sensitive electronic equipment. They are also produced as byproducts of certain chemical processes. No significant natural source is identified for these compounds their presence in the atmosphere is due almost exclusively to the manufacturing rights. As indicated in the cycle of view above the ozone layer, when these chemicals that deplete the ozone layer reached the stratosphere, which are dissociated by ultraviolet light to release chlorine atoms. The chlorine atoms act as catalyst, and each may deteriorate tens of thousands of ozone molecules before being removed from the stratosphere. Given the longevity of CFC molecules, the recovery time measured in decades. It was calculated that a CFC molecule has an average of 15 years to go from ground level to the upper atmosphere and can remain for about a century, until the destruction of one hundred thousand ozone molecules during that period.
Audit observations
The Scientists are increasingly able to attribute the ozone depletion observed that the increase halogenated human (anthropogenic) of CFCs by the use of complex chemical transport models and its validation with observational data (eg SlimCat, clams). These models work by combining satellite measurements of concentrations chemical and meteorological fields with chemical reaction rate constants obtained in laboratory experiments. They are able to identify not only the chemical reactions key, but also offer transport processes CFC photolysis products into contact with the ozone layer.
The ozone hole and its causes
ozone hole in America North in 1984 (abnormally hot to reduce the ozone layer) and 1997 (abnormally cold caused a depletion of the season has increased). Source: NASA
The ozone hole over Antarctica is a region of the Antarctic stratosphere, where ozone levels have declined in recent prices as low as 33% of its pre-1975 values. The ozone hole occurs during the Antarctic spring, between September and December, at first, that strong westerly winds start to circulate around the continent and create a container in the atmosphere. In this polar vortex over 50% of the lowest ozone layer is destroyed during the Antarctic spring.
As explained above, the main cause of depletion of the ozone layer the presence of source container of chlorine gas (primarily CFCs and related halocarbons). In the presence of ultraviolet light, these gases dissociate, releasing chlorine atoms, which then proceed to catalyze ozone destruction. Ozone depletion catalyzed by Cl may occur in the gas phase, but is significantly greater in the presence of polar stratospheric clouds (PSC).
These polar stratospheric clouds form during winter in the extreme cold. Polar winters are dark, composed of three months without solar radiation (sunlight). The lack of sunlight contributes to a decrease in temperature Polar Vortex and traps and chills air. Temperatures are around or below -80 C. These low temperatures form cloud particles and are composed of acid Nitric (type I PSC) or ice (Type II PSC). Both types provide surfaces for chemical reactions that lead to the destruction of the ozone layer. [Citation required]
Photochemical processes are complex, but easy to understand. Key observation is that, generally, most of the chlorine in the stratosphere is in stable "reservoir" compounds, mainly hydrochloric acid (HCl) and chlorine nitrate (ClONO2). During the Antarctic winter and spring without however, reactions on the surface of the particles of polar stratospheric clouds Polar convert these "reservoir" in free radical reactive compounds (Cl and ClO). The clouds can also remove NO2 in the atmosphere by converting nitric acid, which prevents the newly formed ClO become in ClONO2.
The role of sunlight in the ozone layer is the reason for the depletion of the ozone layer over Antarctica is the largest in the spring. During the winter, despite the fact that private security companies are the most abundant, not any light on the center of driving chemical reactions. During the spring, however, the sun rises, power supply to drive photochemical reactions, and melt the polar stratospheric clouds, releasing the trapped compounds. [Edit]
Most of the ozone layer is destroyed, is in the lower stratosphere, unlike ozone depletion much less homogeneous along phase reactions gas, which occurs mainly in the upper stratosphere. [Citation needed]
Warmer temperatures toward the end of spring break the vortex in mid-December. As the hot air rich in ozone from lower latitudes, private security firms are destroyed, the process of impoverishment stops ozone and the ozone hole closes. [Citation needed]
Interest in the ozone layer
While the effect Antarctic hole in ozone loss Ozone is relatively low, estimated at around 4% per decade, the hole has attracted great interest because:
The decrease in the ozone layer was predicted in the 1980s to about 7% over 60 years. [Edit]
Recognition sudden in 1985 there was a large "hole" has been widely reported in the press. The depletion of the ozone layer, particularly rapidly in the Antarctic had already been dismissed as a measurement error. [Citation needed]
Many [Edit] fears that ozone holes might start to appear in other parts of the world, but so far the only loss other large-scale a thin layer of ozone "dimple" observed during the Arctic spring over the North Pole. Midlatitude ozone declined, but at a much lower (decrease of approximately 45%).
If conditions become more severe (lower temperatures in the stratosphere, the stratospheric clouds more active chlorine), then the ozone level world is shrinking at a rate much higher. the standard theory of global warming predicts that the stratosphere cools.
When the Antarctic ozone hole to beat up the ozone layer depleted air moves in nearby areas. The decrease in ozone level of 10% have been reported in New Zealand in the month following the rupture Antarctic ozone hole.
The consequences of depletion of the ozone layer
Since the ozone layer absorbs UVB ultraviolet rays of the sun, loss layer ozone is expected to increase levels of surface UVB rays, which could cause damage, including increases in skin cancer. Is due to the Montreal Protocol. A Although stratospheric ozone depletion are well connected to the CFC and there are good theoretical reasons to believe that decreases in ozone will increase the radiation surface UVB, there is no direct evidence linking the observation of ozone depletion a higher incidence of skin cancer in humans. This is due in part to the fact that the rays UVA has also been implicated in some forms of skin cancer, is not absorbed by ozone, and is almost impossible to control lifestyle changes earlier in the population.
Increased UV
Ozone, while constituting the minority in the Earth's atmosphere, is responsible for the majority of UVB absorption. The amount of UVB radiation penetrates the ozone layer decreases exponentially with oblique path thickness / density of the layer. Consequently, a decrease of ozone in the atmosphere should lead to much higher levels of UVB narrow surface.
The increase in surface UVB due to ozone hole may be partially inferred by calculation radiative transfer model, but can not be calculated from direct measurements because of the lack of reliable historical data (pre-ozone hole) UV surface data, but the latest step programs UV surface observation exist (for example, Lauder, New Zealand).
Because this is the same radiation UV creates ozone in the ozone layer of O2 (oxygen ordinary) first, a reduction of the stratospheric ozone layer, actually tend to increase photochemical production ozone at lower levels (in the troposphere), although the overall trends in total column ozone still show a decline, largely because the ozone generated a photochemical reduction of a shorter natural life, is destroyed before the merger can reach a level that offset the reduction in the ozone layer above of. [Citation needed]
Biological Effects
The main public concern about the ozone hole were the effects of increased ray surface UV and microwave radiation on human health. So far, the ozone layer, in most sites was typically a few percent and, as noted above, no direct evidence of damage to health is available at most latitudes. If high levels of depletion seen in the ozone hole is not common throughout the world, the effects could be much more severe. As the ozone hole over Antarctica has increased in some cases as important to reach regions of southern Australia and New Zealand, environmentalists fear that the increased surface UV could be significant. [Citation needed]
Effects on humans
UVB (the higher energy UV radiation absorbed by ozone) is generally recognized as a contributing factor to skin cancer. In addition, increased surface UV leads to increased tropospheric ozone, which is a risk to human health. [Edit] The increased surface UV also represents an increase of capacity synthesize vitamin D from sunlight.
The cancer preventive effects of vitamin D, which represents a potential beneficial effect of the ozone layer. In terms of costs health, the potential benefits of UV radiation may be greater than the increase of the load.
1. Basal and squamous cell carcinoma – the most common forms skin cancer in humans, basal cell carcinomas and squamous is strongly associated with exposure to UVB rays. The mechanism by which the rays UVB induces these cancers is, of course, the absorption of UVB radiation causes pyrimidine bases in the DNA molecule to form dimers, resulting in errors transcription when DNA replication. These cancers are relatively mild and rarely fatal, although the treatment of squamous cell carcinoma sometimes requires significant reconstructive surgery. By combining epidemiological data and results of animal studies, scientists have estimated that a reduction of one percent of stratospheric ozone could increase the incidence of these cancers by 2%.
2. Malignant melanoma Another form of skin cancer, malignant melanoma, is much less common but far more dangerous, is fatal in about 1520% of cases diagnosed. The relationship between melanoma and ultraviolet exposure, which not well understood, but it appears that both UVB and UVA rays are involved. Experiments on fish suggest that 90-95% of malignant melanomas may be due to UVA experiments visible while in opossums suggest a larger role for UVB rays. Because of this uncertainty, it is difficult to estimate the impact of ozone depletion on the incidence of melanoma. One study showed an increase of 10% of UVB radiation was associated with a 19% increase in melanoma in men and 16% for women. 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, with the layer Ozone decreased and increased UVB rays.
3. Cortical cataracts – Studies suggest an association between ocular cortical cataracts and exposure to UV-B, crude approximations of exposure and various valuation techniques of cataract. A detailed assessment of ocular exposure to UV-B was performed in a study on Chesapeake Bay sailors, where the increase in annual average exposure of the hearing have been associated with an increased risk of cortical opacity. In this group of high exposure predominantly white men, the evidence linking cortical opacities sun exposure is the strongest to date. However, the following data study a population of Beaver Dam, Wisconsin suggested the risk may be limited to men. In the Beaver Dam study, the exposure of women were lower than exposure among men, and the association was not observed. In addition, there was no evidence linking sun exposure with cataract risk in African Americans, although other eye diseases have different prevalence among different racial groups, and cortical opacity appears to be greater in African Americans compared with whites.
4. The tropospheric ozone increase – Increased surface UV leads to increased tropospheric ozone. Ozone at ground level is generally recognized as a health risk, Ozone is toxic because of their strong oxidizing properties. At that time, ozone at ground level is produced mainly by the action of UV radiation on combustion gases of vehicle exhaust gas. [Citation needed]
Effects on crops
Increased UV radiation can be expected to affect cultures. A number of species economically important plants such as rice, depend on cyanobacteria residing on their roots to maintain nitrogen. Cyanobacteria are sensitive to UV light and that would be affected by its increase.
Law and order
Projections NASA Stratospheric ozone, chlorofluorocarbons, if it had not been banned.
The magnitude of the harm they have caused the ozone layer CFCs is not known or not known for decades, but marked decreases in column ozone have been observed (as explained above).
After a 1976 report by the U.S. National Academy of Sciences concluded that credible scientific evidence supported the depletion hypothesis Ozone, a small number of countries including USA, Canada, Sweden and Norway, moved to eliminate CFC use in aerosols. At the time this was widely regarded as a first step towards a broader regulatory policy, but progress in this direction has slowed in subsequent years due to combination of political factors (the resistance after the halocarbon industry and a general change in attitude toward environmental regulation during the first two years of the Reagan administration) and developments in science (following evaluation of the National Academy indicates that the first estimates of the magnitude of destruction ozone layer was too large.) The United States banned the use of CFCs in aerosols in 1978. The European Community rejected the proposed ban on CFCs in aerosols, and the United States, SWC continued to be used as refrigerants and for cleaning circuit. worldwide CFC production declined sharply after the ban aerosol United States, but in 1986, had returned to their 1976 level. In 1980, DuPont closed its research program on alternative halocarbons.
The attitude U.S. Government began to change again 1983, when William Ruckelshaus replaced Anne M. Burford as Administrator of the United States Environmental Protection Agency. Under Ruckelshaus and his successor, Lee Thomas, EPA has promoted an international strategy for the regulation of the halocarbons. In 1985, 20 nations, including most CFC producers major, signed the Vienna Convention for the Protection of the Ozone Layer, which provides a framework for the negotiation of international standards for substances deplete the ozone layer. That same year, the discovery of the ozone hole over Antarctica has been announced, causing a renewed public attention on the subject. In 1987, representatives of 43 nations signed the Montreal Protocol. Meanwhile, Halocarbon industry changed its position and began supporting a protocol to limit production CFC. The reasons for this is partly explained by Dr. Mostafa Tolba, former head of the United Nations Programme on Environment, which was quoted in the June 30, 1990 issue of The New Scientist "… the chemical industry supported the Montreal Protocol in 1987, had to establish a global program to eliminate CFCs, which [were] no longer are protected by patents. This has given companies an equal opportunity in the market for new compounds more efficient. "
In Montreal, the participants agreed to freeze production of CFCs to 1986 levels and reduce production by 50% in 1999. After a series of scientific expeditions in Antarctica presented convincing evidence that the ozone hole has been caused by chlorine and bromine in halogenated organic compounds of human origin, the Montreal Protocol was strengthened in a 1990 held in London. The participants agreed to phase out CFCs and halons entirely (except for a small amount marked for some "essential" uses, such as inhalers for asthma) in 2000. In a 1992 meeting in Copenhagen, the deadline has been moved to 1996.
To some extent, CFCs have been replaced by the less damaging hydro-chloro-fluoro-carbons (HCFCs), although concerns remain regarding HCFCs. In some applications, hydro-fluoro-carbons (HFCs) have been used to replace CFCs. HFCs, which do not contain chlorine or bromine does nothing Although the ozone gas is a powerful greenhouse gas. The best known of these compounds is probably the HFC-134a (R-134a) that the U.S. have largely replaced CFC-12 (R-12) in automotive air conditioners. In the laboratory (a former "core") to use ozone-depleting substances can be replaced by several other solvents.
Ozone Diplomacy by Richard Benedict (Harvard University Press, 1991) realizes detailed negotiation process that led to the Montreal Protocol. Pielke and Betsill a comprehensive overview of the responses of U.S. government early new science of destruction ozone layer, CFCs.
The outlook for the depletion of the ozone layer
Trends of ozone gas.
Since the adoption and strengthening of Protocol Montreal has led to the reduction of CFC emissions, atmospheric concentrations of compounds were the most important down. These substances are gradually atmosphereince removed from peaked in 1994, the effective rate of chlorine (OAT) level in the atmosphere has declined by 10% in 2008. It is estimated that in 2015 the hole Antarctic ozone output is reduced 1 million miles in 25 Al (Newman et al., 2004), complete recovery of the ozone layer over Antarctica occurs 2050 or later. It has been suggested that a detectable (and statistically significant) recovery will not occur until about 2024, with recovery ozone levels to 1980 levels by about 2068. The decrease in the ozone layer of chemicals also been significantly affected by a decrease bromine-containing chemicals. The data suggest that there are considerable natural sources of methyl bromide in the atmosphere (CH3Br) .. Phasing out CFC indicate that nitrous oxide (N2O), which is not covered by the Montreal Protocol, has become the substance rather than ozone-depleting issued and must remain so throughout the 21st century.
2004 ozone hole was completed in November 2004, daily minimum temperatures in the lower stratosphere on stratospheric Antarctica has increased to levels that are too hot for the formation of polar stratospheric clouds (PSC) 2-3 weeks earlier than in most recent years.
Arctic Winter 2005 was very cold in the stratosphere PSC were abundant in high latitude regions of many dissipated by a major world event, which began in the upper stratosphere in February and extended into the Arctic stratosphere in March. Size the Arctic region of abnormally low total ozone in 2004-2005 was higher than in any year since 1997. The prevalence abnormally low total ozone in the Arctic in winter 2004-2005 is attributed to stratospheric temperatures very low and weather conditions favorable for ozone destruction and the continued presence of chemicals that destroy ozone in the stratosphere.
A summary of the IPCC 2005 ozone issues concluded that observations and model calculations indicate that the average amount of ozone is about to plateau. Despite considerable variation in the ozone layer is expected from year to year, including the polar regions where depletion is largest, the ozone layer should begin to recover in coming decades due to decreased levels of ozone substance, provided that full compliance with the Montreal Protocol.
The temperatures during the Arctic winter of 2006 was fairly close to the long-term average until late January, with the minimum measures often cold enough for private security companies. During the last week in January, however, an important event sent temperatures much warmer than normal too hot to support private security. For the temperatures return to normal time around March, the seasonal standard was well above the threshold of CPS. Preliminary maps showing satellite the ozone generated by an instrument of accumulation seasonal ozone layer slightly below the long-term average for the Northern Hemisphere as a whole, although some levels ozone events occurred. In March 2006, the Arctic stratosphere 60 north pole was free of abnormally low ozone areas, except during the period of three days from March 17-19 when the total ozone cover fell below 300 AU in one of the North Atlantic from Greenland to Scandinavia.
The area where total ozone column is less than 220 AU (the accepted definition of the boundary of the ozone hole) has been relatively low until about August 20, 2006. Since then, the area the ozone hole has grown rapidly, reaching a peak of 29 million km on 24 September. In October 2006, NASA said the ozone hole this year Registration has established a new space with a daily average of 26 million miles between 7 October and 13 September 2006, total ozone thickness as low as 85 down the DU 8 October. Both factors in all, 2006 saw the lowest level of depletion of the ozone layer in recorded history. The depletion is attributed to temperatures above Antarctica reach the lowest since record full records began in 1979.
In October 2008, Ecuador's Space Agency released a report titled Hyperion, a study of the past 28 years, data from 10 satellites and ground dozens of instruments around the world among themselves their own, and found that UV radiation reaching equatorial latitudes was much higher than expected, climbing in some densely populated cities to 24 UVI, WHO considers 11mm UV index as an index and a risk great health. The report concluded that the depletion of the ozone layer in the middle latitudes of the planet and is in danger of large populations in these areas. More Later, the CONIDA, the Peruvian Agency for Space Technology, made his own study, which is almost the same facts that the study of Ecuador.
The hole Antarctic ozone is expected to continue for decades. The concentrations of ozone in the lower stratosphere in Antarctica increased by 5% in 2020 and again to previous levels 1980 of about 20,602,075, 1,025 years later than expected in previous assessments. This is because the revised estimates of atmospheric concentrations of substances that deplete the ozone layer and increased use in predicting the future in developing countries. Another factor that may aggravate the depletion of ozone is nitrogen oxide feed above the stratosphere due to changes in wind patterns.
Search History
The basic physical and chemical processes that lead to the formation a layer of ozone in the stratosphere of the Earth have been discovered by Sydney Chapman in 1930. These issues are addressed in the ozone layer and oxygen Article few cycle words, the short wavelength UV radiation splits oxygen (O2) into two molecules of oxygen (O) atoms combine with other oxygen molecules to form ozone. Ozone is removed when the oxygen atom and an ozone molecule "recombine" to form two molecules of oxygen, O3 or O + 2O2. In 1950, Bates David Marcel Nicolet and presented evidence that various free radicals, especially hydroxyl (OH) and nitric oxide (NO), could serve as a catalyst for recombination reaction, this reduces the total amount of ozone. These free radicals are known to be present in the stratosphere, and therefore considered part of natural balance, it was felt that, failing that, the ozone layer would be about twice as thick as it is now.
In 1970, Professor Paul Crutzen that emissions nitrous oxide (N2O), a stable, long-term gas produced by soil bacteria, the surface of the earth could affect the amount of nitric oxide (NO) in the stratosphere. Crutzen showed that nitrous oxide live long enough to reach the stratosphere, where it becomes NO. Crutzen said then that the increased use of fertilizers, could have led to increased emissions of nitrogen oxides on natural background, which in turn lead to increased amount of NO in the stratosphere. Therefore, the activity human could have an impact on the stratospheric ozone layer. The following year, and Crutzen (independent) Harold Johnston suggested that emissions from aircraft NO supersonic flying in the lower stratosphere, could also deplete the ozone layer.
The Rowland-Molina hypothesis
In 1974, Frank Sherwood Rowland, professor of chemistry at the University of California at Irvine, and his postdoctoral associate Mario J. Molina suggests that long-term Organic compounds halogenated, such as CFCs, can behave the same way that Crutzen proposed for nitrous oxide. James Lovelock (more popularly known as the creator of the Gaia hypothesis) was recently discovered during a cruise in the South Atlantic in 1971, almost all CFC compounds made since its invention in 1930 were still present in the atmosphere. Molina and Rowland arrived to the conclusion that, as the N2O, CFCs reach the stratosphere where they are dissociated by UV light releasing Cl atoms (A year earlier, Richard Stolarski and Ralph Cicerone University of Michigan showed that CL is more effective than NO to catalyze ozone destruction. Similar conclusions were reached by Michael McElroy and Steven Wofsy University Harvard. Neither group, however, realized that CFCs were a potential source of stratospheric chlorine Instead, he investigated the possible effects of HCl emissions from the space shuttle, which are much smaller.)
The Rowland-Molina hypothesis was strongly opposed by representatives of aerosols halocarbons and industries. The Chairman of the Board of DuPont has been quoted as saying that the theory of depletion of the ozone layer is "a science fiction tale … a loading … Anything! Absolute. Robert Abplanalp, president of Valve Corporation accuracy (and inventor of the first practice of spray can valve) he wrote to the chancellor of the University of California Irvine to complain about public statements Rowland (Rouen, p 56.) However, within three years most of the cases core made by Rowland and Molina were confirmed by laboratory measurements and by direct observation in the stratosphere. Gas concentrations in the source (CFC and other compounds) and the deposition of chlorine species (HCl and ClONO2) were measured in the stratosphere, and demonstrated that CFCs were indeed the main source of chlorine in the stratosphere, and almost all the CFC issued finally reach the stratosphere. Even more convincing was the measure, by James G. Anderson and his colleagues chlorine monoxide (ClO) in the stratosphere. ClO is produced by the reaction of Cl with ozone and its observation has shown that radicals were present not only Cl in the stratosphere, but actually participated in the destruction of the ozone layer. McElroy and Wofsy extended the work of Rowland and Molina showing that bromine atoms have been even more effective catalysts for the loss of ozone, chlorine atoms and argued that brominated organic compounds known as halons, widely used in fire extinguishers, were a major potential source of bromine in the atmosphere. In 1976, the U.S. National Academy of Sciences published a report concludes that the hypothesis of the ozone layer has been strongly supported by scientific evidence. Scientists have calculated that if CFC production continued to increase at a rate ranging from 10% a year until 1990 and then remain steady, CFCs would result in the overall ozone loss of 5 to 7% in 1995 and a loss of 30-50% in 2050. In response to the United States, Canada and Norway banned the use of CFCs in aerosol sprays in 1978. However, subsequent research, summarized by the National Academy of reports published between 1979 and 1984 suggests that previous estimates of ozone loss at the global level has been too great.
Crutzen, Molina and Rowland were awarded the 1995 Nobel Chemistry Prize for his work on stratospheric ozone.
Ozone Hole
The discovery of the ozone hole over Antarctica for British Antarctic scientists Survey Farman, Gardiner and Shanklin (announced in an article in Nature in May 1985) was a shock to the scientific community, because the observed decrease in the layer polar ozone was much greater than anticipated. [Edit] Satellite measurements show the depletion of ozone around the south pole mass are becoming available at the same time. However, they were initially rejected as unreasonable by data quality control algorithms (which have been filtered out as errors because the values were unexpectedly low) ozone hole was detected only in the satellite data when raw data has been restated following the conclusion that ozone depletion situ observations. Once the software has been broadcast without the flags, the ozone hole has been observed since 1976.
Susan Solomon, atmospheric chemist Administration National Oceanic and Atmospheric Administration (NOAA), proposed that the chemical reactions in polar stratospheric clouds pole (SGP) in the cold Antarctic stratosphere caused a massive increase of well localized and seasonal, the amount of chlorine in the active forms that destroy ozone. Polar stratospheric clouds in Antarctica only form when there is low temperatures, as low as -80 degrees C, and the conditions of spring. Under these conditions, the ice crystals of clouds to provide a suitable surface for the conversion of compounds of chlorine does not react not reactive chlorine compounds, which can deplete the ozone layer easily.
In addition, the polar vortex is formed over Antarctica is very tight and the reaction that occurs on the surface of the crystals in the clouds is very different when it occurs in the atmosphere. These conditions have led to the formation of ozone hole in Antarctica. This hypothesis was decisively confirmed, first by laboratory measurements and subsequently by Direct measurements of the earth and the aircraft at high altitude, very high concentrations of chlorine monoxide (ClO) in the Antarctic stratosphere. [Citation needed]
hypothesis alternative, the ozone hole attributed to variations in solar UV radiation or changes in atmospheric circulation patterns have also been tested and proven be unsustainable. [Citation needed]
Meanwhile, the analysis of ozone measurements of Dobson global network of land has led to an international group concluded that ozone layer was being depleted at all latitudes outside the tropics. [Citation needed] These trends have been confirmed by satellite measurements. Consequently, halocarbons major producing countries agreed to phase out production of CFCs, halons and related compounds, a process that was completed 1996.
Since 1981, United Nations Environment Programme has sponsored a series of reports on scientific assessment of ozone loss. The most recent date of 2007, when Satellite measurements have shown the hole in the ozone layer is recovering and is now smaller than it has been for a decade.
depletion ozone layer and global warming
There are five areas of connection between ozone depletion and global warming:
Radiative forcing gas emissions greenhouse and other sources.
The influence of CO2 forcing itself that produces near-surface global warming is expected to cool the stratosphere. This cooling, in turn, should produce a relative increase in the polar ozone (O3) depletion and the frequency of ozone holes. [Citation needed]
By contrast, ozone depletion represents a radiative forcing of the climate system. There are two opposing effects: Reduced ozone layer in the stratosphere absorb causes except solar radiation, cooling the stratosphere while warming in the troposphere, stratosphere emits less as a result cold downward longwave radiation, thus cooling the troposphere. In general, the cooling dominates, the IPCC concludes that "stratospheric O3 losses observed in the past two decades have resulted a negative forcing of the surface-troposphere system "of approximately 0.15 0.10 watts per square meter (W / m).
One of the strongest predicted effect emissions is that the stratosphere has cooled. Although this cooling has been observed, is not trivial to separate the effects of changes in the concentration of greenhouse gases and depletion of the ozone layer from two lead to a cooling. However, this can be done by numerical modeling stratosphere. The results of the National Oceanic and Atmospheric Administration Geophysical Fluid Dynamics Laboratory show that above 20 km (12.4 miles), greenhouse gases dominate the cooling.
products chemicals that deplete the ozone layer are also greenhouse gas. Increased concentrations of these chemicals have produced 0.34 0.03 W / m of radiative forcing, which corresponds to about 14% of the total radiative forcing increases in the concentrations of greenhouse gases well mixed.
Modeling long-term processes, measurement, the study design and test theories for decades, the paper gain wide acceptance and, ultimately, become the dominant paradigm. Several theories destruction of the ozone layer has been suggested in the 1980s, published in late 1990 and has been proven now. Dr. Drew Schindel, and Dr. Paul Newman, the NASA Goddard, has proposed a theory of the 1990s, using an SGI Origin 2000 supercomputer, which has shaped the destruction of the ozone layer, 78% of the ozone layer destroyed. To refine this model 89% of the ozone layer destroyed, but postponed the estimated recovery of the ozone hole 75 years to 150 years. (A important part of this model is the lack of flights stratosphere due to depletion of fossil fuels.)
Misconceptions about the ozone layer
Some errors common in the depletion of the ozone layer are briefly discussed, more detailed discussions can be found in FAQ depletion of ozone layer.
CFCs are "too heavy "to reach the stratosphere
It is sometimes said that since the CFC molecules are much heavier than nitrogen or oxygen can not reach the stratosphere in large quantities. However, atmospheric gases are not classified by weight, wind (turbulence) are strong enough to mix gases the atmosphere. CFCs are heavier than air, but as argon, krypton and other heavy gases with a long lifetime, spread evenly throughout the turbosphere and reach the upper atmosphere.
man-made chlorine is insignificant compared to natural sources
Another objection is sometimes advanced that is generally accepted that natural sources of tropospheric chlorine (volcanoes, Ocean Spray, etc) are four to five orders of magnitude larger than artificial sources. Although very Indeed, the tropospheric chlorine is not relevant, is stratospheric chlorine that affects the ozone layer. Ocean Spray Chlorine is soluble and therefore is washed by the rain before reached the stratosphere. CFC, however, are insoluble and long term, allowing them to reach the stratosphere. Even in the lower atmosphere is more in this chlorine form of CFCs and related haloalkanes than there is in HCl salt spray, and halocarbons in the stratosphere very widely dominate. One of these halocarbons, chloride methyl has a predominance of natural sources, and is responsible for about 20 percent of chlorine in the stratosphere, and the remaining 80% comes from synthetic compounds.
Very large volcanic eruptions can inject HCl directly into the stratosphere, but direct measurements have shown that their contribution is small compared with that of chlorine of CFCs. A similar statement is incorrect that soluble halogen compounds volcanic plume of Mount Erebus on Ross Island, Antarctica is a major contributor the Antarctic ozone hole. [Citation needed]
An ozone hole was observed in 1956
GMB Dobson (Exploring the Atmosphere, 2nd edition, Oxford, 1968) observed that when spring ozone levels over Halley Bay were first measured in 1956, he was surprised that they were ~ 320 AU, about 150 DU below spring levels, ~ 450 DU, in the Arctic. These, however, were at that time the best known normal climatic values, since no other data of the Antarctic ozone were available. What Dobson describes is essentially the baseline from which the ozone hole is measured: the actual values of the ozone hole are about 150 100 AU.
The difference between the Arctic and Antarctica said Dobson was primarily a matter of time when the ozone layer in the Arctic Last spring gently, with a peak in April, while in Antarctica remained more or less constant in the early spring, increased sharply in November, when the polar vortex broke down.
The behavior seen in the Antarctic ozone hole is completely different. Instead of staying constant, early spring ozone levels drop significantly from their values in winter and low, as long as 50%, and normal values is not reached again until December.
If the theory was correct, the ozone hole should be above the sources of CFC
CFCs are well mixed in the troposphere and the stratosphere. The reason for the hole Antarctic ozone occurs not because there are more but not CFCs, because the low temperatures due to polar vortex allow polar stratospheric clouds to form. Abnormal findings were found significant, serious, localized "holes" above other parts of the world.
The ozone hole is a hole in the ozone layer
When the ozone hole forms, almost all the ozone in the lower stratosphere is destroyed. The upper stratosphere is much less affected, however, that the quantity total ozone over the continent decreases 50 percent or more. The ozone hole does not go all the way through the layer, on the other hand, this is not a uniform 'thinning' of the layer is. This is a "hole" in the sense of "a hole in the earth," which is a depression, not in the sense of a "Hole in the windshield. "
World Ozone Day
In 1994 the UN General Assembly voted to designate September 16 as "World Ozone Day" to commemorate the signing of the Montreal Protocol on that date in 1987.
See also
cycle of ozone and oxygen
Montreal Protocol
"Scientific Assessment of Ozone Depletion" a series of technical reports produced under the auspices of the World Meteorological Organization and the Middle United Nations Environment Programme.
CFC
Melanoma skin cancer
Greenhouse Gases
Ultraviolet
Chemical Lagrangian Model of CLAMS stratosphere
Global warming, ice shelves
Atmospheric window
References
^ Part III. "The science of ozone depletion. Http://www.atm.ch.cam.ac.uk/tour/part3.html. Retrieved on 05/03/2007.
^ "The chlorofluorocarbons (CFCs) are heavier than air, so how do scientists suppose that these chemicals reach the height of the ozone layer to hurt? ". Http: / / www.sciam.com/article.cfm?id=chlorofluorocarbons-cfcs. Retrieved on 08/03/2009.
^ Dobson, R. (2005). "Ozone depletion will increase in the number of cataracts." BMJ 331 (7528): 1292. DOI: 10.1136/bmj.331.7528.1292-d. PMID 16322012. Change
^ Newman, Paul A.. "Chapter 5: Section 4.2.8 Stratospheric Photochemistry CLX catalytic reactions. In Richard Todaro. Stratospheric ozone: an electronic notebook. NASA Goddard Flight Center Atmospheric Chemistry and Dynamics Branch Area. http://www.ccpo.odu.edu/SEES/ozone/class/Chap_5/index.htm. '[]
^ Stratospheric ozone depletion by chlorofluorocarbons (Nobel Conference) ncyclopedia Earth
Schiermeier ^ Q (September 2007). "The poke holes in chemical theory, the ozone layer "([link] dead). Nature 449 (7161): 3823. DOI: 10.1038/449382a. PMID 17898724. http://www.nature.com/news/2007/070924 / full/449382a.html.
^ Francis D. Pope, Jaron C. Hansen, Kyle D. Bayes, R. Randall Friedl, P. Stanley Sander (2007). "Ultraviolet Absorption Spectrum of Chlorine Dioxide" ClOOCl. J. Chem Phys. A 111 (20) 432 232. DOI: 10.1021/jp067660w. PMID 17474723. http://pubs.acs.org/doi/abs/10.1021 / jp067660w.
^ Journal of the Organization Bulletinhe World Weather
^ HY Chen, Lien CY, Lin WY, Lee YT, Lin JJ (May 2009). "UV absorption cross sections ClOOCl are consistent with models of degradation ozone layer. "Science 324 (5928): 7814. DOI: 10.1126/science.1171305. PMID 19423825. Http: / / www.sciencemag.org/cgi/pmidlookup?view long PMID = 19,423,825.
^ Dimitrios K. Papanastasiou, Vasilios C. Papadimitriou, David W. Fahey, James B. Burkholder (2009). "UV absorption spectrum of ClO dimer (Cl2O2) 200 and 420 nm. J. Phys. Chem A 113 (49): 1371113726. DOI: 10.1021/jp9065345. http://pubs.acs.org/doi/abs/10.1021/jp9065345.
^ The Ozone Hole Tour: Part II. Exhaustion recent ozone
^ World Meteorological Organization (WMO)
^ EPA Ozone Depletion:
^ ab "Climate Change 2001: Working Group I: scientific basis. "Intergovernmental Panel on Climate Change Working Group I. 2001. Pp Chapter 6.4 of the stratospheric ozone layer. Http: / / www.grida.no/climate/ipcc_tar/wg1/223.htm.
^
^ Encyclopedia.com: Chlorofluorocarbons
^ Http: / / earthobservatory.nasa.gov / view.php IOTD /? Id = 1771
Ozone hole over Antarctica ^
^ Ozone depletion over Antarctica FAQ, Section 7
^ Climate Change 2001: Group Working Group I: The Scientific Basis. "Intergovernmental Panel on Climate Change Working Group I. 2001. Pp Chapter 9.3.2 Climate change models in the future. http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/351.htm.
^
Orlova Gvozdovskyy I ^ T, E Salkova Terenetskaya I, G Milinevsky (August 2005). "Ozone and solar UV-B radiation: monitoring the ability to synthesize vitamin D in sunlight in Kiev and Antarctica. Int J Remote Sens 26 (16): 35 559. DOI: 10.1080/01431160500076863. http://www.informaworld.com/smpp/content ~ content = ~ Db = A723976621 all.
^ M Norval, AP Cullen, FR Gruijl, et al. (March 2007). "The effects on human health and the depletion of the stratospheric ozone layer and its interactions with climate change. Photochemistry. Photobiol. Science. 6 (3): 23 251. DOI: 10.1039/b700018a10.1039/b700018a (inactive 12/22/2009). PMID 17344960.
^ Schwartz GG, Skinner HG (January 2007). "Kind of vitamin D and cancer: new perspectives ". Curr Opin Clin Nutr Metab Care 10 (1): 611. Doi: 10.1097/MCO.0b013e328011aa60. PMID 17143048. Http://meta.wkhealth.com/pt/pt-core/template- journal / lwwgateway / Media / landingpage.htm? ISSN 1363-1950 = & volume = 10 & topic = 1 & spage = 6.
^ Grant WB, Garland CF, Holick MF (2005). "Comparison of estimated economic burdens due to variations in solar ultraviolet radiation and vitamin D and excess solar UV radiation for the United States. " Photochemistry. Photobiol. 81 (6): 127 686. Doi: 10.1562/2005-01-24-RA-424. PMID 16159309. Http: / / www3.interscience.wiley.com/resolve/openurl? Genre = article & sid = nlm: PubMed & ISSN 0031-8655 = & date = 2005 & volume = 81 & topic = 6 & spage = 1276.
Frank R. ^ Ab Gruijl (Summer 1995). "Impacts http://www.gcrio.org/CONSEQUENCES/summer95/impacts.html projected depletion of the ozone layer. Consequences 1 (2) ..
^ Setlow RB, Grist E, Thompson K, Woodhead AD (July 1993). "Wavelengths effective in induction of malignant melanoma. Proc. Natl. Acad. SCI. USA 90 (14): 666 670. DOI: 10.1073/pnas.90.14.6666. PMID 8341684.
^ Fears TR, Bird CC, Guerry D, et al. (July 2002). "The air flow through ultraviolet radiation and the time for the prediction range half the risk of melanoma. "Cancer Res 62 (14): 39 926. PMID 12124332. Http://cancerres.aacrjournals.org/cgi/pmidlookup?view=long&pmid=12124332.
Covers ^ JF, Casiccia DC (December 2002). "Skin cancer and ultraviolet-B radiation under the Antarctic ozone hole: southern Chile, 1987-2000. Photodermatol Photoimmunol PhotoMOS 18 (6): 294 302. DOI: 10.1034/j.1600-0781.2002.02782.x. PMID 12535025. http://www.blackwell-synergy.com/links/doi/10.1034/j.1600-0781.2002.02782.x/full/.
^ West SK, Duncan DD, Munoz B, et al. (August 1998). "Sun exposure and risk of lens opacities in a study based Labour Project of Salisbury Eye Evaluation. "JAMA 280 (8): 7148. DOI: 10.1001/jama.280.8.714. PMID 9728643. Http: / / jama.ama-assn.org/cgi/content / full/280/8/714.
^ Cruickshanks KJ, Klein BE, Klein R (December 1992). "Exposure to ultraviolet light and cataract: the Beaver Dam Eye Study. I J Public Health 82 (12): 165 862. DOI: 10.2105/AJPH.82.12.1658. PMID 1456342. PMC 1,694,542. http://www.ajph.org/cgi/pmidlookup?view=long&pmid=1456342.
^ West SK, Munoz B, OD Schein, Duncan DD, Rubin GS (December 1998). "Racial differences in lens opacities: the Salisbury Eye Evaluation (View) of the project." Am J Epidemiol. 148 (11): 10 339. PMID 9850124. Http: / / aje.oxfordjournals.org / cgi / pmidlookup? Having long PMID = 9850124.
^ Wu SY Leske MC, Connell AM, Hyman L, Schachat A January (1997). "The prevalence of lens opacities in the Barbados Eye Study. Arch. Ophthalmol. 115 (1): 10 511. PMID 9006434. Http://archopht.ama-assn.org/cgi/pmidlookup?view=long&pmid=9006434.
^ Sinha RP, Singh, SC, and D.-P. Hder (1999). "Photoecophysiology cyanobacteria. Journal of Photochemistry and Photobiology 3: 91 101.
^ Ab http://archive.greenpeace.org/ozone/greenfreeze/moral97/6dupont.html
• Use of ozone-depleting substances in laboratories. 516/2003 TemaNord
^ Newman, PA, Nash, ER, Kawa, SR, Montzka, SA, Schauffler, S. M (2006). "When will the Antarctic ozone hole recover? 33. Geophysical Research Letters: L12814. Doi: 10.1029/2005GL025232.
^ Meteorological Organization Organization World Meteorological Organization (WMO)
^ NOAA A study shows that nitrous oxide emission Ozone Layer Top now, NOAA, August 27, 2009
^ Organization Meteorological Organization (WMO)
CPCtratosphere ^: Winter Bulletins
^
^ The annual NCEP data
^ Select ozone maps, Individual sources
^ Index / products/stratosphere/sbuv2to/archive/nh
^ Ozone Hole Watch
http://www.theregister.co.uk/2006/10/03/ozone_depletion ^
SCISAT ^ CNW Group | Canadian Space Agency | Canada explains the depletion of the ozone layer in 2006
^ Causes and effects of stratospheric ozone reduction: an update. National Academy of Sciences. (1982 and 1983). http://www.nap.edu/openbook.php?isbn=0309032482.
^ Ozone depletion, history and politics accessed November 18, 2007.
Ab ^ Hegerl, Gabriele C., et al .. "Understanding Climate Change" (PDF). Climate Change 2007: The Basis of Physics. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change climate. Intergovernmental Panel on Climate Change. pp. 675. http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter9.pdf. Retrieved from 02/01/2008.
^ Ab (PDF) of the IPCC / TEAP Special Report on Safeguarding the Ozone Layer and the Global Climate System: Issues to hydrofluorocarbons and perfluorocarbons (Summary for Policymakers). Intergovernmental Panel on Climate Change and evaluation techniques and the Economic Group. 2005. http://www.ipcc.ch/press/SPM.pdf. Retrieved on 03/04/2007.
^ "The role of the ozone layer and emissions of greenhouse gases on climate change in the stratosphere. Laboratory of Geophysical Fluid Dynamics. 29/02/2007. http://www.gfdl.noaa.gov/aboutus/milestones/ozone.html. Retrieved on 03/04/2007.
^ Phoenix NewsREON EASY
^ FAQ, Part I, Section 1.3.
^ Ozone depletion FAQ, Part II, Section 4.3
^ Http: / / www.nature.com/nature/journal/v403/n6767/full/403295a0.html
Depletion ^ ozone FAQ, Part II, Section 4.4
^ Ozone depletion FAQ, Part III, Article 6
^ Ozone depletion FAQ, Antarctica
^ Ozone hole: Definition and much more Answers.com
non-technical books
Schiff, Harold, Dotto, Lydia (1978). The war of ozone. Garden City, NY: Doubleday. ISBN 0-385-12927-0.
Roan, Sharon (1989). Ozone Crisis: The evolution of 15 years worldwide a sudden emergency. New York: Wiley. ISBN 0-471-52823-4.
Dray, Philip CAGIN, Seth (1993). Between heaven and earth: how SWC changed our world and endangered the ozone layer. New York: Pantheon Books. ISBN 0-679-42052-5.
Books about public policy issues
Richard Elliot Benedick (1991). Ozone Diplomacy: New Directions in protecting the planet. Cambridge: Harvard University Press. ISBN 0-674-65001-8. (Benedict, Ambassador of the United States has been the main negotiator in meetings that led to the Montreal Protocol.)
Litfin, Karen (1994). Ozone discourses: science and politics of global environmental cooperation. New York: Columbia University Press. ISBN 0-231-08137-5.
Search Articles
Newman PA, Kawa, SR and Nash, ER (2004). "For the size of the Antarctic ozone hole? 31. Geophysical Research Letters: L12814. Doi: 10.1029/2004GL020596.
EC Weatherhead SB, Andersen (2006). "The search for signs of recovery in the ozone layer." Nature 441 (7089): 3945. Doi: 10.1038/nature04746. PMID 16672963.
References
Ozone in the Open Directory Project
UN Chronicle Unlayering ozone layer: Lackland sunscreen
NOAA / LSRS exhaustion Ozone
The NOAA ozone depleting Gas Index
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