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May 09, · The ozone layer, which only makes up percent of Earth’s atmosphere, is getting thinner and thinner all the time. “Ozone holes” are popular names for areas of damage to the ozone layer. This is inaccurate. Ozone layer damage is more like a really thin patch than a hole. The ozone layer is thinnest near the poles. "The ozone layer" refers to the ozone within stratosphere, where over 90% of the earth's ozone resides. Ozone is an irritating, corrosive, colorless gas with a smell something like burning electrical wiring. In fact, ozone is easily produced by any high-voltage electrical arc (spark plugs, Van de Graaff generators, Tesla coils, arc welders).
In the stratosphere the temperature of the atmosphere rises with increasing height, a phenomenon created by the absorption of solar radiation by the ozone layer. In the midlatitudes the peak concentrations of how to disassemble acer aspire one netbook occur at altitudes from 20 to 25 km about 12 to 16 miles. Peak concentrations are found at altitudes from 26 to 28 km about 16 to 17 miles in the tropics and from about 12 to 20 km about 7 to 12 miles toward the poles.
The lower height of the peak-concentration region in the high latitudes largely results from poleward and downward atmospheric transport processes that occur in the middle and high latitudes and the reduced height of the tropopause the transition region between the troposphere and stratosphere. Near-surface ozone often results from interactions between certain pollutants such as nitrogen oxides and volatile organic compoundsstrong sunlight majes, and hot weather.
It is one of the primary ingredients laywr photochemical smoga phenomenon that plagues many urban and suburban areas around the world, especially during the summer months.
The production of ozone in the stratosphere results primarily from the breaking of the chemical bonds within oxygen molecules O 2 by high-energy solar photons. This process, called photodissociationresults in the release of single oxygen atoms, which later join with intact oxygen molecules to form ozone. Scientists believe that the formation of the ozone layer played an important role in the development of life on Earth by screening out lethal levels of UVB radiation ultraviolet radiation with wavelengths between and nanometres and thus facilitating the migration of life-forms from the oceans to land.
The amount of ozone in the stratosphere varies naturally throughout the year as a result of chemical processes that create and destroy ozone molecules and as a result of winds and other transport processes that move ozone molecules around the planet. Over the course of several decades, however, human activities substantially altered the ozone layer.
Ozone depletionthe global decrease in stratospheric ozone observed since the s, is most pronounced in polar regionsand it is well correlated teh the increase of chlorine and bromine in the stratosphere.
Those chemicals, once ozonee by UV radiation from the chlorofluorocarbons CFCs and other halocarbons carbon-halogen compounds that contain them, destroy ozone by stripping away single oxygen atoms from ozone molecules. Depletion is so extensive mqkes so-called ozone holes regions of zoone reduced ozone coverage form over the poles during the onset of their respective spring seasons.
The largest such hole—which has spanned more than Lauer Montreal Protocol has been a success, with some 99 percent of the ozone-depleting chemicals regulated by the treaty having been phased out since its adoption in Compliance with international treaties that phased out the production and delivery of many ozone-depleting chemicals, combined with upper stratospheric cooling due to increased carbon dioxideis thought to have contributed to the shrinking of the ozone holes over the poles and to slightly higher stratospheric ozone levels overall.
Continued reductions in how to pre order advanced warfare loading are expected to result in smaller ozone holes above Antarctica after However, some scientists noted that gains in stratospheric ozone levels have only occurred in the upper stratospherewhat is a process associate declines in ozone concentrations in the lower stratosphere outpacing increases in the mqkes stratosphere.
Ozone layer. Additional What country is bohemia today. Print print Print. Table Of Contents.
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer makez the appropriate style manual or other sources if you have any questions. Facebook Twitter. Give Feedback External Websites. Let whar know if you have suggestions to improve this article requires login. External Websites. Donald Wuebbles Harry E. See Article History. The layers of Earth's atmosphere, with a yellow line makkes the air temperature at various heights.
Ozone damage on the leaf of an English walnut Juglans regia. Changes in the size of the ozone hole from October to October Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now. Antarctic ozone hole, September 17, Two bar graphs depicting the fhe ozone hole maakes and the minimum ozone coverage in Dobson units of the Southern Hemisphere ozone hole, — Researchers launching a balloon carrying an ozonesonde, an instrument that measures ozone in the atmosphere, at Amundsen-Scott South Pole Makea in Antarctica.
Learn More in these what makes the ozone layer Britannica articles:. Sunlight causes nitric oxide to react chemically with ozone O 3thereby converting the ozone to molecular oxygen O 2.
Equally important as an absorber in the how to make hair moisturizer wavelengths is water laysr. A secondary absorber in the infrared range is carbon…. History at your fingertips. Sign up here to see what happened On This Dayevery day in your inbox! Email address. By signing up, you agree to our Privacy Notice. Be on the lookout for your Britannica ozonw to get trusted stories delivered right to your inbox.
Location in Earth’s atmosphere
The Earth's ozone layer ozone layer The region of the stratosphere containing the bulk of atmospheric ozone. The ozone layer lies approximately kilometers ( miles) above the Earth's surface, in . Most of the remaining ozone occurs in the troposphere, the layer of the atmosphere that extends from Earth’s surface up to the stratosphere. Near-surface ozone often results from interactions between certain pollutants (such as nitrogen oxides and volatile organic compounds), strong sunlight, and hot weather. The ozone layer is found in the upper regions of the stratosphere where it protects the earth from the harmful ultraviolet rays of the sun. These radiations can cause skin cancer in humans. The ultraviolet rays split the oxygen molecule into free oxygen atoms, these free oxygen atoms combine with the oxygen molecule to form ozone.
The Earth's ozone layer ozone layer The region of the stratosphere containing the bulk of atmospheric ozone.
The ozone layer lies approximately kilometers miles above the Earth's surface, in the stratosphere. Depletion of this layer by ozone depleting substances ODS will lead to higher UVB levels, which in turn will cause increased skin cancers and cataracts and potential damage to some marine organisms, plants, and plastics. Less ozone-layer protection from ultraviolet UV light UV Ultraviolet radiation is a portion of the electromagnetic spectrum with wavelengths shorter than visible light.
UVA is not absorbed by ozone. UVB is mostly absorbed by ozone, although some reaches the Earth. UVC is completely absorbed by ozone and normal oxygen. Scientific Assessment of Ozone Depletion: Exit. The Earth's atmosphere is composed of several layers. The lowest layer, the troposphere troposphere The region of the atmosphere closest to the Earth.
The troposphere extends from the surface up to about 10 km in altitude, although this height varies with latitude. Almost all weather takes place in the troposphere. Everest, the highest mountain on Earth, is only 8. Temperatures decrease with altitude in the troposphere. As warm air rises, it cools, falling back to Earth. This process, known as convection, means there are huge air movements that mix the troposphere very efficiently.
Virtually all human activities occur in the troposphere. Everest, the tallest mountain on the planet, is only about 5. The next layer, the stratosphere stratosphere The region of the atmosphere above the troposphere. The stratosphere extends from about 10km to about 50km in altitude.
Commercial airlines fly in the lower stratosphere. The stratosphere gets warmer at higher altitudes. In fact, this warming is caused by ozone absorbing ultraviolet radiation.
Warm air remains in the upper stratosphere, and cool air remains lower, so there is much less vertical mixing in this region than in the troposphere.
Most commercial airplanes fly in the lower part of the stratosphere. Health and Environmental Effects of Ozone Depletion. Ozone Layer Research and Technical Resources. Information for Students about the Ozone Layer. Addressing Ozone Layer Depletion. Adapting to a Changed Ozone Layer. Phasing Out Ozone-Depleting Substances.
Managing Refrigerant Emissions. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 9 to 18 miles 15 to 30 km above the Earth's surface see the figure below. Ozone is a molecule that contains three oxygen atoms. At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount has remained relatively stable during the decades that it has been measured.
Source: Figure Q from Michaela I. Hegglin Lead Author , David W. Montzka, and Eric R. The ozone layer in the stratosphere absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface.
UVB is a kind of ultraviolet light from the sun and sun lamps that has several harmful effects. It is a cause of melanoma and other types of skin cancer. It has also been linked to damage to some materials, crops, and marine organisms. The ozone layer protects the Earth against most UVB coming from the sun. It is always important to protect oneself against UVB, even in the absence of ozone depletion, by wearing hats, sunglasses, and sunscreen.
However, these precautions will become more important as ozone depletion worsens. UVB has been linked to many harmful effects , including skin cancers, cataracts, and harm to some crops and marine life.
Scientists have established records spanning several decades that detail normal ozone levels during natural cycles. Ozone concentrations in the atmosphere vary naturally with sunspots, seasons, and latitude. These processes are well understood and predictable. Each natural reduction in ozone levels has been followed by a recovery. Beginning in the s, however, scientific evidence showed that the ozone shield was being depleted well beyond natural processes.
When chlorine and bromine atoms come into contact with ozone in the stratosphere, they destroy ozone molecules. One chlorine atom can destroy over , ozone molecules before it is removed from the stratosphere.
Ozone can be destroyed more quickly than it is naturally created. Some compounds release chlorine or bromine when they are exposed to intense UV light in the stratosphere. These compounds contribute to ozone depletion, and are called ozone-depleting substances ODS ODS A compound that contributes to stratospheric ozone depletion. ODS include chlorofluorocarbons CFCs , hydrochlorofluorocarbons HCFCs , halons, methyl bromide, carbon tetrachloride, hydrobromofluorocarbons, chlorobromomethane, and methyl chloroform.
ODS are generally very stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere. When they break down, they release chlorine or bromine atoms, which then deplete ozone.
ODS that release chlorine include chlorofluorocarbons chlorofluorocarbons Gases covered under the Montreal Protocol and used for refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. Since they are not destroyed in the lower atmosphere, CFCs drift into the upper atmosphere where, given suitable conditions, they break down ozone.
These gases are being replaced by other compounds: hydrochlorofluorocarbons, an interim replacement for CFCs that are also covered under the Montreal Protocol, and hydrofluorocarbons, which are covered under the Kyoto Protocol.
All these substances are also greenhouse gases. See hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, ozone depleting substance. CFCs , hydrochlorofluorocarbons hydrochlorofluorocarbons Compounds containing hydrogen, fluorine, chlorine, and carbon atoms.
Although ozone depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons CFCs. They have been introduced as temporary replacements for CFCs and are also greenhouse gases.
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. Not all chlorine and bromine sources contribute to ozone layer depletion. For example, researchers have found that chlorine from swimming pools, industrial plants, sea salt, and volcanoes does not reach the stratosphere.
In contrast, ODS are very stable and do not dissolve in rain. Thus, there are no natural processes that remove the ODS from the lower atmosphere.