Cause of ozone depletion cfcs were present in aerosols, used in industrial processes longlived in the atmosphere make it to the stratosphere converted to reactive clbr catalytic process that destroys ozone figure q81 from. Phasing out hcfc refrigerants to protect the ozone layer. Like many lines of scientific inquiry, research leading to the prediction and discovery of global ozone depletion and the damaging effects of cfcs followed a path full of twists and turns. Exploring earths atmosphere like many lines of scientific inquiry, research leading to the prediction and discovery of global ozone depletion and the damaging effects of cfcs followed. In 1975, two different groups of scientists sent cfc measuring tools up in airplanes and balloons. Hence, these chemicals are known as ozone depleting substances odss. Chlorofluorocarbons cfcs have been found to be the main cause of ozone depletion and have many health impacts. In the chart we see emissions of ozonedepleting substances from 1960 onwards. The 1974 rowlandmolina hypothesis was that cfcs in the stratosphere when bombarded by uv radiation could result in chlorine radicals that could destroy large numbers of ozone molecules and lead to ozone layer depletion. He and rowland formed a hypothesis about their fate, which suggested that cfcs would deplete the ozone layer. The molecules of chlorofluorocarbons in the stratosphere are broken down by the ultraviolet radiations and release chlorine atoms.
In the natural situation ozone is continuously being. Explain the greenhouse effect and its potential harmful effects. Generally, we find thinning or depletion of the ozone layer to the extent of ozone hole creation over the southern pole i. The montreal protocol led to a global phaseout of most substances that deplete the ozone layer, such as chlorofluorocarbons cfcs. Ozone protects living organisms by absorbing harmful ultraviolet radiation uvb from the sun. Cfc substitutes since their ozone depleting effect is only about 10% that of cfcs. For example, chlorofluorocarbons cfcs, once used in almost all refrigeration and air conditioning systems, eventually reach the stratosphere, where they are broken apart to release ozone depleting chlorine atoms. Human production of chlorinecontaining chemicals, such as chlorofluorocarbons cfcs, has added an additional factor that destroys ozone. Working successfully together pioneering work in the 1970s by scientists mario molina, sherwood rowland and paul crutzen unearthed the problem of ozone depletion by manmade chemicals. Ozone layer depletion cause, effects, and solutions. The saga of cfcs, ozone depletion, and climate change. Emissions of cfcs account for about 80% of total stratospheric ozone depletion.
What emissions from human activities lead to ozone. Stratospheric ozone depletion find, read and cite all the research you. All the while, surprised by the discovery of the ozone hole, government agencies scurried to better understand ozone depletion, and organized the national ozone experiment noze in 1986. The interactive effects between the stratospheric ozone layer, solar ultraviolet uv radiation, and climate change are presented within the. Since the ozone layer prevents most harmful uvb wavelengths 280315 nm of ultraviolet light uv light from passing through the earths atmosphere, observed. The ozone destroyed by manmade emissions is comparable or more than the amount destroyed by natural processes. Chronology of chlorofluorocarbons and ozone using the handout, students place major events from the development and use ofrefrigerants.
The response to the ozone crisis by dupont, the inventor of cfcs and the largest producer of ozone depleting chemicals in the world is a prime example of the 3d corporate strategy. Conversion project approved by the 41st executive committee in december. This process leads to stratospheric ozone depletion figure 1. In chemical reactions, the activities relate to cfcs and stratospheric ozone. Ozonedepleting substances ozone layer protection us epa.
The thinning or reduction of ozone depletion is most prominent in the polar regions, especially over antarctica. The latter phenomenon is referred to as the ozone hole. One of the easiest ways to reduce damages caused to the ozone layers by limiting the use of vehicles. Protecting the ozone layer and reducing global warming undp. Rowland in 1974 studies further reviled about 7% of ozone layer would be. Stratospheric ozone depletion by chlorofluorocarbons. The severe depletion of the ozone layer in any particular area is called ozone hole. Hence, the level of cfcs should drop off at the highest altitudes. All that complacency vanished, however, after scientists discovered a large hole in the ozone layer.
When the scientists reported their findings in 1974, cfcs were in wide. While other nations canada and the scandinavian countries were. The only important destruction process for cfcs is ultraviolet photolysis in the stratosphere, with the release of atomic chlorine. Stratospheric ozone depletion noaa earth system research. The ozone layer, situated in the stratosphere about 15 to 30 km above the earths surface. The ozone layer in the stratosphere absorbs a large part of the harmful uv radiation coming from the sun.
Chlorofluorocarbons cfcs and other halogenated ozone depleting substances ods are mainly responsible for manmade chemical ozone depletion. But ozone depletion and climate change are linked in many other ways as well,particularly through. What emissions from human activities lead to ozone depletion. Various odss, however, accelerate the destruction processes, resulting in lowerthannormal ozone levels. Cfc molecules are extremely stable, and they do not dissolve in rain. The ozone depletion potential odp is the ratio of the impact on ozone of a chemical compared to the impact of a similar mass of chlorofluorocarbon cfc 11. The ozone depletion process begins when cfcs chlorofluorocarbons and other ozone depleting substances ods are emitted into the atmosphere. The mechanism of the ozone layer depleted by cfcs was identified. In 1985, the observation of an ozone hole in the antarctic pole provided proof that the ozone layer was depleting. Environmental effects of stratospheric ozone depletion, uv radiation. Stratospheric ozone depletion b ch lorofiluorocarbons manmade chlorofluorocarbons cfcs such as cci2f2 and cci3f are inert in the lower atmosphere and can survive for a hundred years or more without reaction. Defined in this manner, odp is a useful measure of the potential for each com. The total amount of effective halogens chlorine and bromine in the stratosphere can be calculated and are known as the equivalent effective stratospheric chlorine eesc. The main reasons for the ozone hole are chlorofluorocarbons, carbon tetrachloride, methyl bromide and hydrochlorofluorocarbons.
These gases bring chlorine and bromine to the stratosphere, which cause depletion of the ozone layer. The evolution of stratospheric ozone depletion policy can best be understood as a twostage process. The models suggested that, if the hypotheses were correct and the ozone was being destroyed by cfcs, cfcs would be broken down at high elevations. A happy sideeffect of the gradual ban of these products is. Ozone depleting chemicals odc excise tax audit techniques guide. Includes the handout, student activities and answer guide. Cfcs are molecules made up of chlorine, fluorine and carbon. The ozone layer is being destroyed by cfcs and other substances. This is measured in tonnes of chlorofluorocarbon11equivalents cfc11. The evolution of policy responses to stratospheric ozone. No, ozone depletion itself is not the principal cause of global climate change. Jun 09, 1989 the problem is, the ozone depletion scare is a hoax, and this wellorchestrated and financed campaign to phase out and ban the production of cfcs, some of the most useful chemicals ever known to man, is taking place despite the fact that there is no scientific evidence whatsoever to prove that cfcs are depleting the ozone layer. Stratospheric ozone destruction is an essentially separate process from green house gas ghg accumulation in the lower atmosphere see figure 8. Ozone layer depletion is the gradual thinning of the earths ozone layer in the upper atmosphere caused due to the release of chemical.
The ozone depletion phenomenon the ozone depletion. Wmo world meteorological organization, scientific assessment of. Ozone depletion potentials ozone depletion potentials odps provide a rel ative measure of the expected impact on ozone per unit mass emission of a gas as compared to that expected from the same mass emission of cfc 11 integrated over time wuebbles, 1983. Ozone depletion progressing globally except in the tropical zone. Ozone depletion has also been detected outside the antarctic. A challenge for international environmental law and policy. Ozone depletion is a concern because stratospheric ozone is. This project strengthened the understanding of how human emissions of cfcs were leading to unnaturallyhigh levels of chlorine in the stratosphere, leading to. Intl geophysical year worldwide network of ozone stations created 1974. After taking that action, we pretty much forgot about ozone depletion and cfcs for 10 years. One commonly used measure of a compounds ozone destroying capacity is its ozone depletion potential odp.
Advocacy and science are mixed together and need to be separated. Due to the depletion of the ozone layer by cfcs ozone hole is formed in that region. This in turn would lead to more uv radiation reaching the earth. Cfcs and ozone depletion nature and community mother. Protecting the ozone layer and reducing global warming. Phaseout of cfcs in the manufacture of pharmaceutical. Ozone depletion as a national issue during stage i of the process of formulating stratospheric ozone policy in the early and mid1970s, cfc induced stratospheric ozone depletion emerged as a major environmental and political issue primarily in the united states. Satellite data indicate a global reduction in ozone of about. Cfcs, halons, and hcfcsdestroy the ozone layer, and have created an ozone hole over the south pole. Chlorofluorocarbons or cfcs are the main cause of ozone layer depletion. The appearance of the antarctic ozone hole gave cre dence to the theoretical predictions that cfcs and some brominecontaining chemicals e. Pdf on jan 1, 2008, jozef syktus and others published atmosphere. Skeptics vs ozone hole lunar and planetary laboratory.
Changes in ozone and climate are directly linked because ozone absorbs solar radiation and is also a greenhouse gas. Chapte r ozone depletion potentials, global warming. What is ozone depletion burning issues free pdf download. Montreal protocol on substances that deplete the ozone layer, the united states committed to a collaborative, international effort to regulate and phase out ozone depleting substances. Air pollution, climate change, and ozone depletion. The odp is the ratio of the impact on ozone of a chemical compared to the impact of a similar mass of cfc 11. A significant number of chemical species were clearly involved in the interaction of cfcs and ozone in. The average concentration of ozone in the atmosphere is 300 dobson units.
Understand the difference between groundlevel and stratospheric ozone 2. An additional sciencerelated concept is the perception of chemicals as positive or negative. The chairman of dupont commented that the ozone depletion theory was a science fiction tale. It has been estimated that one molecule of cfc can cause the loss of 00 ozone molecules. Chlorofluorocarbons and ozone wiley online library. If there is a real connection between cfcs, ozone depletion and increased surface uv leading to more cancer cases lets document the science. Download twenty questions and answers about the ozone layer pdf 2. Cfcs were a common aerosol propellant in spray cans and were also used as refrigerants, solvents, and foamblowing agents. What is ozone depletion burning issues free pdf download the ozone layer is a region in the earths stratosphere that contains high concentrations of ozone and protects the earth from the harmful ultraviolet radiations of the sun. The ozone layer, cfcs and global warming objectives subjects. The ozone depletion factor reflects the potential ozone depletion that results from one kilogram of a given chemical compared to the ozone depletion that results from one kilogram of cfc 11 trichlorofluoromethane.
Cfc molecules are extremely stable, and they do not 10. Ozone and chlorine monoxide clo, for example, have been observed extensively with a variety of instruments. A gas with a larger odp destroys more ozone over its atmospheric lifetime. Chlorofluorocarbons and ozone depletion answer guide. The stratospheric ozone layer forms a thin shield in the upper atmosphere, protecting life on earth from the suns ultraviolet uv rays. Evidence shows that the main causes of ozone depletion are the releases of manufactured chlorine and brominebased chemicals such as chlorofluorocarbons cfcs, halons and hydrochlorofluorocarbons hcfcs into the atmosphere. Molina and rowland first suggested that cfcs might play a role in depleting ozone in the stratosphere, the region of the atmosphere at altitudes from about 12 to 50 km. Ozone depletion the ozone depletion process begins when cfcs chlorofluorocarbons and other ozone depleting substances ods are emitted into the atmosphere. In addition to their nobel prize winning work showing that. The odp is the ratio of the impact on ozone of a chemical compared to the impact of a similar mass of cfc. Both types of ozone depletion were observed to increase as emissions of halocarbons increased. Doc depletion of the stratospheric ozone layer ozone. Because of a growing concern over stratospheric ozone depletion and its attendant dangers, a ban was imposed on the use of cfcs in aerosolspray dispensers in the late 1970s by the united states, canada, and the scandinavian countries. Hfcs are currently being developed as cfc substitute that do not damage the ozone layer.
In the 1980s, scientists observed a thinning of the ozone layer over antarctica, and people began thinking of it as an ozone hole. Most questions and answers are updates of those presented in previous ozone assessments, while others have been added or. Cfcs break down the earths ozone layer, rowland and molina were key in convinc ing scientists. Stratospheric ozone depletion, ultraviolet radiation and. Ozone is regularly monitored above the uk to determine the level of ozone loss. In their paper, they estimated that if cfc use was banned immediately, ozone loss would go on for years. The ozone layer acts like a shield in the upper atmosphere the stratosphere, to protect life on earth from harmful ultra violet uv radiation. Pdf ozone depletion by chlorofluorocarbons cfcs was first proposed by molina and rowland in their 1974 nature paper. The aerosol industry also launched a pr blitz, issuing a press release stating that the ozone destruction by cfcs was a theory, and not fact. Column ozone is the total amount of ozone between the earths surface and space, or mathematically, it is the vertical integral of ozone concentration moleculescubic cm. On june 30, 1975 a du pont advertisement in the new york times read. We need to reduce the overlap between the article and ozone depletion and cfc. The odp is calculated relative to cfc 11, section ii. Achievements in stratospheric ozone protection us epa.
The first stage involves the emergence of stratospheric ozone depletion as a domestic issue in the united states and several other countries in the 1970s, while the second stage focuses on its transformation to an international. Protection against depletion of stratospheric ozone by chlorofluorocarbons. It covers substances with a high ozone depleting potential, cfcs and the 1st generation of cfc. Ozone depletion consists of two related events observed since the late 1970s. Investigators did not set our to determine whether human activity affects our environment nor did they know much about chemical pollutants. These are released by solvents, spray aerosols, refrigerators, airconditioners, etc. Clo is a highly reactive gas that is involved in catalytic ozone destruction cycles throughout the stratosphere see q9. Cfcs and other contributory substances are referred to as ozone depleting substances ods. Hfcs, pfcs and sf6 are not ozone depleting substances, however, compared to co2, they have a. Mount pinatubo aerosols, chlorofluorocarbons, and ozone. The following table is reproduced from irc section 4682b.
Additional research has shown that ozone depletion occurs. There are also springtime polar tropospheric ozone depletion. If cfc production continued, however, ozone loss would be even greater. It provides a useful basis for estimating the ozone depletion potential of various chemicals relative to cfc 11, which has an odp of 1. For each ods, this page provides the compounds atmospheric lifetime, ozone depletion potential ozone depletion potentiala number that refers to the amount of ozone depletion caused by a substance. In 1990, 93 nations agreed, as part of the montreal protocol established 1987, to end production of ozone depleting chemicals by the end of the 20th century. Chlorofluorocarbons and ozone depletion american chemical. In history, the activities highlight the process of change connected with the use of refrigerants throughout history.
Implications of ozone depletion and the montreal protocol s is depletion of the ozone layer the principal 18 cause of global climate change. Evolution of policy responses to stratospheric ozone depletion. The increase of ultraviolet light due to depletion of the ozone layer will not only. Chlorofluorocarbons and ozone depletion at the university of california, irvine, f. Ozone depleting substances european commission europa eu. Pdf what would have happened to the ozone layer if.
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