PDF | On Jan 1, , Md Safiuddin and others published Global ozone depletion: causes, effects and preventive measures. 𝗣𝗗𝗙 | There are many situations where human activities have significant effects on the environment. Ozone layer damage is one of them. Ozone layer damage is one of them. The objective of this paper is to review the origin, causes, mechanisms and bio effects of ozone layer depletion as well as.
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Ozone depletion - Wikipedia, the free encyclopedia kaz-news.info publication_files/pdf) provide an extensive review of. Scientific indices representing the relative effects of different gases upon ozone depletion and climate forcing are presented. Several scenarios for future. University of Santo Tomas College of Education Clarissa J. Te November 11, 4E2/4BSM Social Dimensions Ozone Depletion: A Global Issue Brought By .
Ozone is produced naturally in the atmosphere. Few only knows that Earth has its own natural sunscreen that shields it from the sun's ultraviolet radiation.
It's known as the ozone layer.
It is a fragile band of gases beginning 15 kilometers above the planet, and reaching up to the kilometer level. The ozone layer is a vital component in the history of life on earth. Hundreds of millions of years ago, only single cell organisms existed on Earth and at that time, the planet lacked the oxygen that we need to live. But as these organisms evolved, they began to release tiny amounts of oxygen through photosynthesis and over a period of millions of years, this led to the creation of the ozone layer.
The ozone layer lies in the stratosphere, in the upper level of our atmosphere. The ozone in it is spread very sparsely. The stratospheric ozone layer sometimes gets confused with the ozone lying near the earth's surface, known as "ground-level ozone. Stratospheric ozone filters out most of the sun's potentially harmful shortwave ultraviolet UV radiation. This ozone has become depleted, due to the release of such ozone-depleting substances as chlorofluorocarbons CFCs. In , a group of scientists made an unsettling discovery: The depletion appeared during the southern hemisphere's spring October and November and then filled in.
The highest latitudes — the north and south poles — experience the greatest amount of ozone loss, during their spring. Ozone depletion is most pronounced in the Antarctic. But ozone depletion, to a lesser degree, now occurs in the mid-latitudes. The Ozone Hole in Antartic Ozone is first thought to have been identified in by Christian Schonbein, a Swiss chemist who was actually looking at electrical discharges.
Ozone can easily be produced by a high voltage electrical arc such as a spark plug or an arc welder. They carried out the first measurements of ozone in Europe and in , GMB Dobson, a lecturer in meteorology at Oxford University decided to follow their example. Dobson went on to research ozone for the next 40 years and was involved in the setting up of special stations around the globe to measure ozone.
Frustrated by the equipment available to measure it, he also designed his own instrument. In the s, British physicist, Sidney Chapman, produced a theory explaining how ozone is created and destroyed in the stratosphere and this process became known as Chapman Reactions.
He established that when oxygen molecules in the stratosphere are hit by radiation from the sun, they can split into two oxygen atoms. When one of these separated atoms becomes attached to a complete oxygen molecule, it becomes ozone O3.
At that time, the Ozone Layer was taken for granted. And very soon afterwards, they confirmed that mankind had been unwittingly damaging the Ozone Layer —and putting the whole environment at risk - for at least half-a-century, through the use of man-made chemicals known as ODS — Ozone Depleting Substances. These chemicals are called "ozone-depleting substances" ODS. ODS are very stable, nontoxic and environmentally safe in the lower atmosphere, which is why they became so popular in the first place.
However, their very stability allows them to float up, intact, to the stratosphere. Once there, they are broken apart by the intense ultraviolet light, releasing chlorine and bromine. Chlorine and bromine demolish ozone at an alarming rate, by stripping an atom from the ozone molecule. A single molecule of chlorine can break apart thousands of molecules of ozone. ODS have a long lifetime in our atmosphere — up to several centuries.
Their application is quite limited: But the problem with halons is they can destroy up to 10 times as much ozone as CFCs can. HFCs do not deplete ozone, but they are strong greenhouse gases. CFCs are even more powerful contributors to global climate change, though, so HFCs are still the better option until even safer substitutes are discovered.
When stratospheric ozone is depleted, more UV rays reach the earth. Exposure to higher amounts of UV radiation could have serious impacts on human beings, animals and plants.
What does this mean for life on earth?
Even the smallest reduction in stratospheric ozone can have a noticeable impact by increasing the amount of UV radiation that reaches the planet. If this ozone becomes depleted, then more UV rays will reach the earth. It can bring harm to human health through the form of skin cancers, sunburns and premature aging of the skin; cataracts, blindness and other eye diseases because UV radiation can damage several parts of the eye, including the lens, cornea, retina and conjunctiva; and weakening of the human immune system immunosuppression.
UV radiation can also have an adverse impacts on agriculture, forestry, natural ecosystems and on raw materials like wood, plastic, rubber, fabrics and many construction materials that can have an economic impact to the world and can badly damage the marine life yielding to the loss of biodiversity in our oceans, rivers and lakes could reduce fish yields for commercial and sport fisheries.
Under the Montreal Protocol, the federal government is responsible for controlling the import, manufacture, use, sale and export of ODS.
The government must pass the Ozone Depleting Substances Regulation to control ODS stored in products and equipment, and encourage consumers and industry to use more environmentally safe alternatives.
In the implementation of the regulation, there are classes made to categorize different ODS. Class I lists all CFCs and halons, as well as methyl chloroform and carbon tetrachloride. Class I substances are considered to have the most significant impact on ozone layer depletion.
Ozone depletion became a global issue when it became a unrelenting concern for everyone when it suddenly became a threat to survival of mankind. We may not see it in our naked eye but we can feel it effects. Temperatures are fluctuating. Droughts, typhoons and floods are keep on happening.
Sea levels are said to be rising. Why is it happening? Most of us will pin point at the occurrence of Global Warming as a result of ozone depletion. Nowadays, this two words are becoming common and almost everyone heard a lot about it and yet, it seem that other people still need more convincing.
This global issue has been one of the most prioritized agenda of various number of environmentalists, climate scientists, and governments worldwide in their conferences and meetings.
Despite the growing evidence indicating that our world may be in danger, there are still some people and interest groups that claims that global warming is a hoax and it is just a conditioning. Since then, ozone depletion had brought global warming, it is put under trial and has become a case of where a lot of arguments are being presented in the hearing.
Even there is now a scientific consensus about this matter, some people still don't think that global warming is happening. So, whether we understand it or not, the concern people showed and proposed evidences supporting that what is happening is real and is continuously arising.
Different environmental protocols and policies are being planned, implemented and evaluated to save Earth. The government of each country help prevent further Ozone Depletion through laws and by attending world conferences like UN. Every nation of the world have taken a crucial step in joining together to halt the production and use of ozone-destroying chemicals. But how ordinary people like us can help in restoring the ozone layer.
So, here are some ways in which we can contribute to protecting the ozone layer and our precious Earth. Consumption fell by more than 60 percent by ; 80 percent by ; and by percent by This is measured in tonnes of ozone-depleting substances all weighted relative to their depleting potential.
Using the 'play' button on the map below allows you to view changes across the world since By clicking on a country on the map, you can view a time-series of how its national consumption has changed over this period. This quantifies the aggregate of a number of substances. In the chart below we see the breakdown of consumption by substance.
Note that, as with other measures throughout this entry, each substance has been weighted by its potential to destroy ozone. By using the "change country" button in the interactive chart you can view consumption patterns of individual substances by country or region.
By checking the 'relative' box you can also view percentage share of a given substance to total ODS consumption. However, it's also interesting to note the relative decline and change in the quantity of individual substances.
Throughout the s and first half of the s, chlorofluorocarbons CFCs dominated global consumption accounting for 60 percent, reducing to 50 percent. However, through the s we have seen a rising dominance of hydrochlorofluorocarbons HCFCs ; in HCFCs accounted for 94 percent of global consumption. This replacement was therefore been an important reduction strategy particularly where the complete phase-out of ozone depleting substances was not readily available.
Chlorofluorocarbons CFCs have almost been completely phased out, declining from over , tonnes in to tonnes in In the Vienna Convention for the Protection of the Ozone Layer was adopted and entered into force in In its first year there were only 29 parties signed to the agreement.
Ozone Depletion : Introduction (leaflet)
This rapidly increased in the years to follow, reaching parties by In , the Vienna Convention became the first of any Convention to achieve universal ratification. The Vienna Convention, despite not mandating parties to take concrete actions on ozone protection laid the foundations for adoption of The Montreal Protocol. Using the 'play' button and timeline in the chart below we can observe how the Montreal Protocol was adopted across the world since The Protocol has now reached universal ratification, with South Sudan as the final signatory in Since its first draft in , the Montreal Protocol has undergone numerous amendments of increasing ambition and reduction targets.
As shown in following section, subsequent amendments were been critical in the Protocol's success in reducing ODS consumption. In the chart below we see various projections of historic and future concentrations of effective chlorine substances i. These are mapped from assumptions of no international protocol, the first Montreal treaty in , followed by subsequent revisions of increasing ambition.
As shown, under the instance of no protocol, it's projected that global ODS emissions and stratospheric concentrations would have continued to increase rapidly in the decades to follow. However, even under the initial Montreal Protocol, and subsequent London amendment, reduction controls and targets would have been too relaxed to have resulted in a reduction in ODS emissions.
A reduction or slowdown in emissions relative to a 'no protocol' scenario would have been achieved but this would be insufficient to lead to an absolute reduction. However, the Copenhagen and its subsequent revisions greatly increased controls and ambition in global commitments, leading to a peak in stratospheric concentrations in the early s and projected declines in the decades to follow.
Ozone layer depletion Stratospheric ozone concentration What impact has man-made ODS emissions had on stratospheric ozone concentrations? In the chart below we see average stratospheric ozone concentrations in the Southern Hemisphere where ozone depletion has been most severe from to An 'Ozone Hole' would approximate to an area where the ozone concentration drops to an average of around Dobson Units.
Below we see that since through to the early s, stratospheric ozone concentrations in the South Hemisphere fell to the concerning 'ozone hole' level of DU. For several decades since the s, concentrations have continued to approximate around or below DU. Over the last few years since , however, ozone concentrations have started to slowly recover. Click to open interactive version Ozone hole area Has the fall of stratospheric ozone concentrations been reflected in an ozone hole?
In the chart below we see the maximum and mean ozone hole area over Antarctica, measured in square kilometres km2. Like gas concentrations, ozone hole area is monitored daily by NASA via satellite instruments. Satellite and data imaging of the Antarctic ozone hole from through to can be viewed at NASA's Goddard Media Centre ; this provides a very visual understanding of the growth of the Antarctic ozone hole over this period.
Click to open interactive version When is the ozone layer expected to recover? The Ozone Layer has recently shown early signs of recovery. In the charts below we profile historic levels and future projections of recovery in two forms: equivalent stratospheric chlorine i.
ODS concentrations, and stratospheric ozone concentrations through to This is measured as the global average, as well as concentrations Antarctic and Artic zones. Note that such projections are given as the median lines from a range of chemistry-climate; true modelled results presented in the Montreal Protocol Scientific Assessment Panel report present the full range of modelled estimates, with notable confidence intervals.
ODS can have a significant lifetime in the atmosphere, for some between 50 and years on average. This means that despite reductions in ODS emissions and eventually complete phase-out of these substances , equivalent stratospheric chlorine ESC concentrations are expected to remain higher than levels through to the end of the century.
However, it's expected that they peaked in the early s and will continue to slowly decline throughout this period. As a global average concentration, it's expected that ozone levels will return to their levels around mid-century.
Antarctica, where ozone depletion has been most severe due to very low temperatures is expected to recover much more slowly. It's projected that Antarctic ozone concentrations will only begin to approach levels by the end of the century.
Click to open interactive version Have countries been misreporting emissions? The story of international cooperation and action on addressing ozone depletion is a positive one: the Vienna Convention was the first Convention to receive universal ratification.
Over the last few decades we have seen a dramatic decline in emissions of ozone-depleting substances. How was an increase in emissions detected? Atmospheric concentrations of CFC have been measured and tracked back to the s via air collection and analysis with automated onsite instrumentation, such as with gas chromatography coupled with electron capture detection GC—ECD.
This allows us to track atmospheric concentrations over time.
Ozone Depletion : Introduction (leaflet)
Using statistics on reported emissions of CFC submitted by parties to the Montreal Protocol, it is possible to construct estimates and projections of what change in atmospheric concentration should occur based on such levels of emissions.The breakdown of ozone in the stratosphere results in reduced absorption of ultraviolet radiation.
What is the Ozone Hole?
The chlorine atoms act as a catalyst , and each can break down tens of thousands of ozone molecules before being removed from the stratosphere. April 22, Main article: Retrieved December 31, The ozone layer lies in the stratosphere, in the upper level of our atmosphere.