Where is ozone concentrated

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. At the global level we see the trend of declining consumption — as established above — since 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 The rapid decline in emissions of ozone-depleting substances shown above was driven by international agreement to phase out their production.

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 on Substances that Deplete the Ozone Layer is arguably the most successful international treaty to date. 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 Ozone concentrations are measured in Dobson Units DU : this is number of molecules of ozone that would be required to create a layer of pure ozone 0.

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.

Since we see a distinct increase in the Antarctic ozone hole area, reaching a maximum of 30 million km 2 in the early s. However, since the late s, the ozone hole area had approximately stabilised between 20 to 25 million km 2. 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.

When ozone O 3 absorbs UV light, it will split the molecule into one free oxygen atom O 1 and one molecule of oxygen gas O 2. Even low-energy radiation can split ozone. Now look at the ozone layers again and answer some questions. Interactive Lab.

Ozone is a molecule made up of three atoms of oxygen. It works a lot like sunscreen, blocking out harmful ultraviolet UV rays from the sun. In recent years, the amount of ozone in the atmosphere has decreased. So will the Earth, and all of the life on it, get sunburned? Where is good and bad ozone located? The different layers of the atmosphere The atmosphere is divided into regions defined primarily by temperature.

Ozone in the Troposphere Ozone in the troposphere is "bad" for breathing, for contributing to the smog and greenhouse gases created by human activities, and it can also act as a chemical oxidant by ripping off oxygen atoms from other compounds including you, the plants around you, other animals, etc.

View Animation Oxygen gas two molecules of oxygen, or O 2 is present in the atmosphere. See ozone depleting substance. HCFCs , carbon tetrachloride carbon tetrachloride A compound consisting of one carbon atom and four chlorine atoms. Carbon tetrachloride was widely used as a raw material in many industrial uses, including the production of chlorofluorocarbons CFCs , and as a solvent. Solvent use ended when it was discovered to be carcinogenic.

It is also used as a catalyst to deliver chlorine ions to certain processes. Its ozone depletion potential is 1. Methyl chloroform is used as an industrial solvent. Its ozone depletion potential is 0. ODS that release bromine include halons halons Compounds, also known as bromofluorocarbons, that contain bromine, fluorine, and carbon.

They are generally used as fire extinguishing agents and cause ozone depletion. Bromine is many times more effective at destroying stratospheric ozone than chlorine. Methyl Bromide is an effective pesticide used to fumigate soil and many agricultural products. Because it contains bromine, it depletes stratospheric ozone and has an ozone depletion potential of 0. Production of methyl bromide was phased out on December 31, , except for allowable exemptions. In the s, concerns about the effects of ozone-depleting substances ODS ODS A compound that contributes to stratospheric ozone depletion.

Gaseous CFCs can deplete the ozone layer when they slowly rise into the stratosphere, are broken down by strong ultraviolet radiation, release chlorine atoms, and then react with ozone molecules.

See Ozone Depleting Substance. Aerosols are emitted naturally e. There is no connection between particulate aerosols and pressurized products also called aerosols. See below propellants. However, global production of CFCs and other ODS continued to grow rapidly as new uses were found for these chemicals in refrigeration, fire suppression, foam insulation, and other applications.

Some natural processes, such as large volcanic eruptions, can have an indirect effect on ozone levels. For example, Mt. Pinatubo's eruption did not increase stratospheric chlorine concentrations, but it did produce large amounts of tiny particles called aerosols aerosols Small particles or liquid droplets in the atmosphere that can absorb or reflect sunlight depending on their composition.

These aerosols increase chlorine's effectiveness at destroying ozone. The aerosols in the stratosphere create a surface on which CFC-based chlorine can destroy ozone. However, the effect from volcanoes is short-lived. Ozone contributes to what we typically experience as "smog" or haze, which still occurs most frequently in the summertime, but can occur throughout the year in some southern and mountain regions. Although some stratospheric ozone is transported into the troposphere, and some VOC and NOx occur naturally, the majority of ground-level ozone is the result of reactions of man-made VOC and NOx.

Significant sources of VOC are chemical plants, gasoline pumps, oil-based paints, autobody shops, and print shops. Nitrogen oxides result primarily from high temperature combustion. Significant sources are power plants, industrial furnaces and boilers, and motor vehicles.

Many people mistakenly believe that tropospheric ozone concentrations are high only in major urban areas, but high ambient ozone concentrations can and do occur anywhere. It is also formed in smaller cities like Raleigh, NC and Cincinnati, OH, and it is transported hundreds of miles downwind from where it is created to affect ambient air quality in other urban and rural areas.

Where ozone is formed, peak concentrations usually occur during afternoon hours, when sunlight is the most intense. However, areas downwind of major sources of VOC and NOx may experience ozone peaks in the afternoon and evening, after wind has carried ozone and its VOC and NOx precursors many miles from their sources. Thus, high ozone concentrations can occur in remote areas and at various times of day, including during the early evening or night.