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 jibticutepo.gq 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 .
Shown in the chart below is the level of natural emissions which has been approximately consistent over this period , and total emissions which is the sum of natural and man-made emissions.
Here we see a clear growth-peak-reduction trend in ozone-depleting emissions, with a rapid rise in emissions increasing more than three-fold from through to the late s, followed by a similarly fast reduction in the decades which followed. By , emissions had returned to levels. This was largely the result of international regulatory agreements and concerted action to phase-out the production and consumption of these substances explored later in this entry.
In the chart below we see the magnitude of global decline in ODS consumption since This data measures the indexed consumption of ODS to the i.
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. 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.
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. In the chart below we see the annual change in percent of measured concentrations of CFC shown as the solid line.
As we see, actual and expected concentration changes map closely over the period up to Since , however, the annual rate of decline in concentrations has fallen almost halved from This is highly inconsistent with the expected rate of change which would have resulted in the case that reported emissions to the Montreal Protocol were correct.
This inconsistency between actual and expected rate of change particularly in the case of a slowdown in concentration decline suggests an increase in global emissions despite reports close to zero since 8.
Click to open interactive version Where are such emissions coming from? It's challenging to definitively attribute emissions sources to a particular geographical location for mixed global gases. However, some additional measurements allowed the authors to provide an informed estimate. Using combined CFC measurements in the Northern and Southern Hemisphere and atmospheric transport models, the authors suggested the likely source of additional CFC emissions was from the Northern Hemisphere.
This was further supported by data from the Mauna Loa Observatory MLO in Hawaii, which also provide measurements of other chemical emissions. In correlating chemical pollution tracers and CFC emissions, the authors suggest there is strong evidence that the source of increased CFC emissions is Eastern Asia.
Montzka et al. How much of an impact will recent emissions of CFC have on ozone layer recovery?
The long-term impact of emissions for the ozone layer will depend on how long continued emissions of CFC persist. In the chart below we show the absolute concentrations of CFC as opposed to the annual rate of change, shown above in terms of actual measurements solid lines, for both hemispheres and projections dashed line. Here you see that despite recent emissions, total concentrations continue to fall but at a notably slower rate than expected.
However this could be minimised to the span of a few years if emissions are now rapidly reduced and return close to zero, as reported within the Ozone Secretariat. Nonetheless, the capacity to identify where atmospheric concentrations and reported emissions are inconsistent is an important step in itself; it makes it clear that our measurement infrastructure does not allow misreporting to go unnoticed.
Although ozone depletion has been a global issue, there is significant differences in distribution of ozone layer depletion across the world. Overall, ozone depletion increases with latitude with low levels of depletion at the equator and tropics, and highest depletion at the poles. Although depletion has occurred over both the Antarctic and Artic poles, Antarctica has experienced the most severe development of the 'ozone hole'.
Why is this the case? An important condition for ozone depletion is very cold atmospheric temperatures. 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.
Ozone Depletion : Introduction (leaflet)
This means most of the ODS we've released over the last 80 years are still making their way to the stratosphere, where they will add to the ozone destruction. Halons brominated fluorocarbons also play a large role. 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.Standard global warming theory predicts that the stratosphere will cool. Over the last few years since , however, ozone concentrations have started to slowly recover.
Archived from the original on January 29, They identify key chemical reactions and transport processes that bring CFC photolysis products into contact with ozone. Stratospheric pollution: u3vltczRw.
From Wikipedia, the free encyclopedia. Working Group I: In the implementation of the regulation, there are classes made to categorize different ODS. Click to open interactive version Ozone hole area Has the fall of stratospheric ozone concentrations been reflected in an ozone hole?
In the s, 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.