File Name: global warming and ozone layer depletion .zip
- Ozone Layer
- Unfinished business after five decades of ozone-layer science and policy
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The thinning is most pronounced in the polar regions, especially over Antarctica. The Montreal Protocol , ratified in , was the first of several comprehensive international agreements enacted to halt the production and use of ozone-depleting chemicals.
Emissions were increasing rapidly until the s. Since then the world has achieved rapid progress: the near-elimination of ozone-depleting substances and the trend towards recovery of the ozone layer are arguably among the most successful international environmental collaborations to date. In this entry we present the data on ozone layer depletion, signs of recovery, emissions of ozone-depleting substances, international agreement and collaboration, and the consequences of ozone layer depletion.
It is formed of three oxygen atoms giving it the chemical formula, O 3. This reactivity is significant in its interactions described in the entry below : the ozone layer can be depleted and broken down through its interaction with man-made compounds in the upper atmosphere. We can differentiate this profile into two key zones:. The impact of ozone in the troposphere as a local air pollutant is instead covered in our entry on Air Pollution. These gases, emitted at the surface, are distributed globally through the lower atmosphere through wind transport patterns.
From there, they can be transported into the upper atmosphere stratosphere where they can form highly reactive chlorine or bromine gases in the presence of ultraviolet UV sunlight.
Reactive halogen gases can then destroy stratospheric ozone, resulting in depletion of the ozone layer. Individual ozone-depleting substances are not equal in their impact on depletion.
Some gases, per tonne, have a significantly higher potential for ozone depletion than others. ODP measures the relative impact on ozone depletion per tonne of gas. Ozone-depleting substances chlorines and bromines can be emitted from natural and anthropogenic man-made sources. In the chart we see emissions of ozone-depleting substances from onwards. This is measured in tonnes of chlorofluorocarbonequivalents CFC 11 equivalents. Shown in the chart 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 section above we provide data on global emissions of ozone-depleting substances. In the chart 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 In the chart we see the quantity of ODS consumption by country. This is measured in tonnes of ozone-depleting substances all weighted relative to their depleting potential.
By clicking on a country on the map, you can view a time-series of how its national consumption has changed over this period. The trends in consumption above have been aggregated to total consumption of ODS. This quantifies the aggregate of a number of substances.
In the chart 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. 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 the chart we see the evolution of global parties signing on to the Vienna Convention.
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.
The Montreal Protocol is an international protocol to the Vienna Convention, agreed in before entering into force in Its purpose was to phase-out reduce and eventually eliminate the use of man-made ozone-depleting substances for protection of the ozone layer.
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. In the chart 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.
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. 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.
In the chart we see average stratospheric ozone concentrations in the Southern Hemisphere where ozone depletion has been most severe from to 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.
Has the fall of stratospheric ozone concentrations been reflected in an ozone hole? In the chart we see the maximum and mean ozone hole area over Antarctica, measured in square kilometres km 2. Like gas concentrations, ozone hole area is monitored daily by NASA via satellite instruments. Full recovery is, however, expected to take until at least the second half is this century as described in the entry below. The Ozone Layer has recently shown early signs of recovery. However, full recovery of stratospheric ozone concentrations to historical levels is projected to take many more decades.
In the charts 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.
The data presented is measured relative to concentrations in where is equal to 0. 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. Antarctica, where ozone depletion has been most severe due to very low temperatures is expected to recover much more slowly.
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. Montzka et al. 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 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. 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.
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 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. Why is this the case? An important condition for ozone depletion is very cold atmospheric temperatures.
This factor alone explains the concentration of ozone depletion at the poles rather than at lower latitudes. Ozone depletion has been most severe over Antarctica because it provides the unique temperature and chemical conditions for effective ozone destruction by halogen gases. This occurs for only months in Arctic regions, but across 5 to 6 months in Antarctica through winter and early spring. The liquid and solid particles in PSCs allow highly reactive chlorine gas to be formed when halogen gases and sunlight are present.
This highly reactive chlorine gas is then very effective in breaking down stratospheric ozone. It is these unique conditions through the winter and early spring that result in high ozone destruction over Antarctica.
As discussed earlier in this entry , stratospheric ozone plays a fundamental role in protecting surface lifeforms from exposure to harmful levels of UV-B radiation.
In the figure we show the average percentage change in UV irradiation reach the surface in relative to levels in
Unfinished business after five decades of ozone-layer science and policy
Published Jul 16, Updated Jul 27, Global warming is caused primarily by putting too much carbon dioxide into the atmosphere when coal, oil, and natural gas are burned to generate electricity or to run our cars. Carbon dioxide spreads around the planet like a blanket, and is one of the main gases responsible for the absorption of infrared radiation felt as heat , which comprises the bulk of solar energy. Ozone depletion occurs when chlorofluorocarbons CFCs and halons—gases formerly found in aerosol spray cans and refrigerants—are released into the atmosphere see details below. Ozone sits in the upper atmosphere and absorbs ultraviolet radiaton, another type of solar energy that's harmful to humans, animals and plants.
The atmosphere displays modes of variability whose structures exhibit a strong longitudinally symmetric annular component that extends from the surface to the stratosphere in middle and high latitudes of both hemispheres. The pattern of climate trends during the past few decades is marked by rapid cooling and ozone depletion in the polar lower stratosphere of both hemispheres, coupled with an increasing strength of the wintertime westerly polar vortex and a poleward shift of the westerly wind belt at the earth's surface. Annular modes of variability are fundamentally a result of internal dynamical feedbacks within the climate system, and as such can show a large response to rather modest external forcing. The dynamics and thermodynamics of these modes are such that strong synergistic interactions between stratospheric ozone depletion and greenhouse warming are possible. These interactions may be responsible for the pronounced changes in tropospheric and stratospheric climate observed during the past few decades. If these trends continue, they could have important implications for the climate of the 21st century. Aclearly recognizable but unexpected pattern of trends over the past 30 years has recently emerged in global climate records.
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She had just been looking at the record of average surface temperatures of the Earth. The year was the warmest since reliable temperature records have been kept, and the twentieth year in a row in which the average global surface temperature was higher than the year average. The next year, , was the fifth warmest on record; the six warmest years on record have occurred in the last decade. If the global warming trend continues, the results could be depressing indeed: melting polar ice along with thermal expansion of the oceans could raise the sea level, flooding coastal cities, and many agricultural landscapes could dry out, becoming deserts.
Emissions were increasing rapidly until the s. Since then the world has achieved rapid progress: the near-elimination of ozone-depleting substances and the trend towards recovery of the ozone layer are arguably among the most successful international environmental collaborations to date. In this entry we present the data on ozone layer depletion, signs of recovery, emissions of ozone-depleting substances, international agreement and collaboration, and the consequences of ozone layer depletion. It is formed of three oxygen atoms giving it the chemical formula, O 3. This reactivity is significant in its interactions described in the entry below : the ozone layer can be depleted and broken down through its interaction with man-made compounds in the upper atmosphere.
Ты уверена, что мы должны его беспокоить. - Я не собираюсь его беспокоить, - сказала Мидж, протягивая ему трубку.
Much done, but much unfinished
Что. Этого не может. Он заперт внизу. - Нет. Он вырвался оттуда.
Поликарбонатная крыша еще была цела, но под ее прозрачной оболочкой бушевало пламя. Внутри клубились тучи черного дыма. Все трое как завороженные смотрели на это зрелище, не лишенное какой-то потусторонней величественности. Фонтейн словно окаменел.
Затаив дыхание, она вглядывалась в экран. КОД ОШИБКИ 22 Сьюзан вздохнула с облегчением. Это была хорошая весть: проверка показала код ошибки, и это означало, что Следопыт исправен.
Вы полагаете, что Северная Дакота может быть где-то. - Возможно. - Стратмор пожал плечами. - Имея партнера в Америке, Танкадо мог разделить два ключа географически.
Так я тебе докажу.
Танкадо предложил бесценный математический метод, но зашифровал. Зашифровал, используя этот самый метод. - Сейф Бигглмана, - протянула Сьюзан. Стратмор кивнул.