How is the ozone layer in the stratosphere being depleted?

Answer 1

Ozone Science: The Facts Behind the Phaseout

The Earth's ozone layer protects all life from the sun's harmful radiation, but human activities have damaged this shield. Less protection from ultraviolet light will, over time, lead to higher skin cancer and cataract rates and crop damage. The U.S., in cooperation with over 160 other countries, is phasing out the production of ozone-depleting substances in an effort to safeguard the ozone layer.


I. The Ozone Layer
The Earth's atmosphere is divided into several layers. The lowest region, the troposphere, extends from the Earth's surface up to about 10 kilometers (km) in altitude. Virtually all human activities occur in the troposphere. Mt. Everest, the tallest mountain on the planet, is only about 9 km high. The next layer, the stratosphere, continues from 10 km to about 50 km. Most commercial airline traffic occurs in the lower part of the stratosphere.


in the graph, most atmospheric ozone is concentrated in a layer in the stratosphere, about 15-30 kilometers above the Earth's surface (graph courtesy of World Meteorological Organization, Scientific Assessment of Ozone Depletion: 1998, WMO Global Ozone Research and Monitoring Project - Report No. 44, Geneva, 1998). Ozone is a molecule containing three oxygen atoms. It is blue in color and has a strong odor. Normal oxygen, which we breathe, has two oxygen atoms and is colorless and odorless. Ozone is much less common than normal oxygen. Out of each 10 million air molecules, about 2 million are normal oxygen, but only 3 are ozone.

However, even the small amount of ozone plays a key role in the atmosphere. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface. Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects, including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life.

At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount, however, remains relatively stable. The concentration of the ozone layer can be thought of as a stream's depth at a particular location. Although water is constantly flowing in and out, the depth remains constant.

While ozone concentrations vary naturally with sunspots, the seasons, and latitude, these processes are well understood and predictable. Scientists have established records spanning several decades that detail normal ozone levels during these natural cycles. Each natural reduction in ozone levels has been followed by a recovery. Recently, however, convincing scientific evidence has shown that the ozone shield is being depleted well beyond changes due to natural processes.

II. Ozone Depletion
For over 50 years, chlorofluorocarbons (CFCs) were thought of as miracle substances. They are stable, nonflammable, low in toxicity, and inexpensive to produce. Over time, CFCs found uses as refrigerants, solvents, foam blowing agents, and in other smaller applications. Other chlorine-containing compounds include methyl chloroform, a solvent, and carbon tetrachloride, an industrial chemical. Halons, extremely effective fire extinguishing agents, and methyl bromide, an effective produce and soil fumigant, contain bromine. All of these compounds have atmospheric lifetimes long enough to allow them to be transported by winds into the stratosphere. Because they release chlorine or bromine when they break down, they damage the protective ozone layer. The discussion of the ozone depletion process below focuses on CFCs, but the basic concepts apply to all of the ozone-depleting substances (ODS).

In the early 1970s, researchers began to investigate the effects of various chemicals on the ozone layer, particularly CFCs, which contain chlorine. They also examined the potential impacts of other chlorine sources. Chlorine from swimming pools, industrial plants, sea salt, and volcanoes does not reach the stratosphere. Chlorine compounds from these sources readily combine with water and repeated measurements show that they rain out of the troposphere very quickly. In contrast, CFCs are very stable and do not dissolve in rain. Thus, there are no natural processes that remove the CFCs from the lower atmosphere. Over time, winds drive the CFCs into the stratosphere.

The CFCs are so stable that only exposure to strong UV radiation breaks them down. When that happens, the CFC molecule releases atomic chlorine. One chlorine atom can destroy over 100,000 ozone molecules. The net effect is to destroy ozone faster than it is naturally created. To return to the analogy comparing ozone levels to a stream's depth, CFCs act as a siphon, removing water faster than normal and reducing the depth of the stream.

Large fires and certain types of marine life produce one stable form of chlorine that does reach the stratosphere. However, numerous experiments have shown that CFCs and other widely-used chemicals produce roughly 84% of the chlorine in the stratosphere, while natural sources contribute only 16%.

Large volcanic eruptions can have an indirect effect on ozone levels. Although Mt. Pinatubo's 1991 eruption did not increase stratospheric chlorine concentrations, it did produce large amounts of tiny particles called aerosols (different from consumer products also known as aerosols). These aerosols increase chlorine's effectiveness at destroying ozone. The aerosols only increased depletion because of the presence of CFC - based chlorine. In effect, the aerosols increased the efficiency of the CFC siphon, lowering ozone levels even more than would have otherwise occurred. Unlike long-term ozone depletion, however, this effect is short-lived. The aerosols from Mt. Pinatubo have already disappeared, but satellite, ground-based, and balloon data still show ozone depletion occurring closer to the historic trend.

One example of ozone depletion is the annual ozone "hole" over Antarctica that has occurred during the Antarctic Spring since the early 1980s. Rather than being a literal hole through the layer, the ozone hole is a large area of the stratosphere with extremely low amounts of ozone. Ozone levels fall by over 60% during the worst years.

In addition, research has shown that ozone depletion occurs over the latitudes that include North America, Europe, Asia, and much of Africa, Australia, and South America. Over the U.S., ozone levels have fallen 5-10%, depending on the season. Thus, ozone depletion is a global issue and not just a problem at the South Pole.

Reductions in ozone levels will lead to higher levels of UVB reaching the Earth's surface. The sun's output of UVB does not change; rather, less ozone means less protection, and hence more UVB reaches the Earth. Studies have shown that in the Antarctic, the amount of UVB measured at the surface can double during the annual ozone hole. Another study confirmed the relationship between reduced ozone and increased UVB levels in Canada during the past several years.

Laboratory and epidemiological studies demonstrate that UVB causes nonmelanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to cataracts. All sunlight contains some UVB, even with normal ozone levels. It is always important to limit exposure to the sun. However, ozone depletion will increase the amount of UVB, which will then increase the risk of health effects. Furthermore, UVB harms some crops, plastics and other materials, and certain types of marine life.

For more information, see the Ozone Depletion Process page.

III. The World's Reaction
The initial concern about the ozone layer in the 1970s led to a ban on the use of CFCs as aerosol propellants in several countries, including the U.S. However, production of CFCs and other ozone-depleting substances grew rapidly afterward as new uses were discovered.

Through the 1980s, other uses expanded and the world's nations became increasingly concerned that these chemicals would further harm the ozone layer. In 1985, the Vienna Convention was adopted to formalize international cooperation on this issue. Additional efforts resulted in the signing of the Montreal Protocol in 1987. The original protocol would have reduced the production of CFCs by half by 1998.

After the original Protocol was signed, new measurements showed worse damage to the ozone layer than was originally expected. In 1992, reacting to the latest scientific assessment of the ozone layer, the Parties decided to completely end production of halons by the beginning of 1994 and of CFCs by the beginning of 1996 in developed countries.

Because of measures taken under the Protocol, emissions of ozone-depleting substances are already falling. Based on measurements of total inorganic chlorine in the atmosphere, which stopped increasing in 1997 and 1998, stratospheric chlorine levels have peaked and are no longer increasing. The good news is that the natural ozone production process will heal the ozone layer in about 50 years.

IV. The EPA Global Programs Division
In addition to regulating the end of production of the ozone-depleting substances, the U.S. Environmental Protection Agency (EPA) implements several other programs to protect the ozone layer under Title VI of the Clean Air Act. These programs include refrigerant recycling, product labeling, banning nonessential uses of certain compounds, and reviewing substitutes.
EPA's Stratospheric Ozone Information Hotline responds to inquiries and distributes information about ozone depletion and EPA's programs to protect the ozone layer. Call 1-800-296-1996 to ask questions or to order free copies of the following documents:

Reports to the Nation: Our Ozone Shield
Written by the National Oceanic and Atmospheric Administration (NOAA), this booklet describes the history and science of ozone depletion.

Scientific Assessment of Ozone Depletion: 2002
This is the executive summary of the most recent World Meteorological
Organization and United Nations Environmental Programme assessment. It contains the most up-to-date understanding of ozone depletion and reflects the thinking of over 250 international scientific experts who contributed to its preparation and review.

Answer 2

All those that keep saying that it is ground based chloroflorocarbons is just sensationalist psuedo-science.
It was all about making more money.
Not a single refrigerant has ever gone out of production.
The US government now controls a monopoly on some of these, so they can charge 10 to 20 times what should be market rate.

Here is a real scientific, physics question to answer:

All of the chemical compounds that are blamed on ozone destruction are heavier than air. These chemical compounds have too high a specific gravity to get above the stratosphere on there own.
Meaning, if you spray some of it out here near the ground, it has no way of ever getting even a few thousand feet off the ground.

If you will keep up with current events, you will have read that the naturally occuring ozone hole over Antarctica is slowly closing. Meaning the ozone hole is getting smaller.
WHAT?!?!?!
Where did the new ozone come from????

It's all naturally cyclical.
You puny Humans, get over yourselves. You are not powerful enough to control the Sun or Space weather.

Answer 3

The ozone layer was being actively depleted in the seventies up to the early nineties until the banning of CFC and BFC compounds. But no matter how destructive we are (and believe you me, we can be little devils), we could never deplete the entire layer.

Why?

Have you ever walked outside after a particularly violent lightening storm? That fresh, clean smell in the air is ozone. Oxygen comes in two forms, one is O2, which is what we breath and what makes up nearly 21% of the atmosphere. The other form is O3, or Ozone, which reflects most UVB rays and gives the sky the blue color. It seems to absorb all frequencies of light except for blue. Cool huh?

It's also deadly to breathe. Go figure.

Anywho, every time lightening strikes, or it gets particularly hot somewhere, Ozone is produced at higher levels than are depleted. Actually, gasses from erupting volcanoes and fissures in the crust, also called Mizukus, account for more Ozone depletion and acid rain production than any pollution man has put out.

Feel better? I know I do.

Answer 4

Well... First, the worst thing we humans put into the stratosphere are cfcs (carbon flouro carbons). Those tiny corpuscles found in most aerosol products. The reason why these are so bad, is because they are strong enough to stay in tact for the ride up to the stratosphere, also they are light enough to travel freely. When these cfcs enter the ozone layer they literally take over or destroy the atoms in the ozone layer that protect us from the sun. Years of aerosol usage has depleted a considerable amount of ozone. You add to that the exhaust from gasoline in vehicles, power plants, factories, and more and you get total ozone annihilation. All of these factors work in the same way, on a molecular scale.

Answer 5

Well to put all of the scientific words in a few sentences. Just Far too many motor vehicles emits exhaust which devastates the ozone layer. Don't for get all of the factories, nuclear factories, large industries, car factories, etc.. Last but not least, all of the space shuttles and satellites being sent into space. All of these things (and a whole lot more) contributes to depleting the ozone layer. However, no one is to blame because this is just simply the evolution of us humans. We found ways to revolutionize the way we live such as technology, cars, airplanes, and entertainment, I'm pretty sure that we will find ways to protect ourselves from the harmful ultraviolet rays....I just don't know when.

Answer 6

Large volcanic eruptions can have an indirect effect on ozone levels. Although Mt. Pinatubo's 1991 eruption did not increase stratospheric chlorine concentrations, it did produce large amounts of tiny particles called aerosols (different from consumer products also known as aerosols). These aerosols increase chlorine's effectiveness at destroying ozone. The aerosols only increased depletion because of the presence of CFC - based chlorine. In effect, the aerosols increased the efficiency of the CFC siphon, lowering ozone levels even more than would have otherwise occurred. Unlike long-term ozone depletion, however, this effect is short-lived. The aerosols from Mt. Pinatubo have already disappeared, but satellite, ground-based, and balloon data still show ozone depletion occurring closer to the historic trend.

Answer 7

Ozone is a relatively simple molecule, consisting of three oxygen atoms bound together. Yet it has dramatically different effects depending upon its location. Near Earth's surface, where ozone comes into direct contact with life forms, it primarily displays a destructive side. Because it reacts strongly with other molecules, large concentrations of ozone near the ground prove toxic to living things. At higher altitudes, where 90 percent of our planet's ozone resides, it does a remarkable job of absorbing ultraviolet radiation. In the absence of this gaseous shield in the stratosphere, the harmful radiation has a perfect portal through which to strike Earth.





Although a combination of weather conditions and CFC chemistry conspire to create the thinnest ozone levels in the sky above the South Pole, CFCs are mainly released at northern latitudes--mostly from Europe, Russia, Japan, and North America--and play a leading role in lowering ozone concentrations around the globe.




Worldwide monitoring has shown that stratospheric ozone has declined for at least two decades, with losses of about 10 percent in the winter and spring and 5 percent in the summer and autumn in such diverse locations as Europe, North America, and Australia. Researchers now find depletion over the North Pole as well, and the problem seems to be getting worse each year. According to a United Nations report, the annual dose of harmful ultraviolet radiation striking the northern hemisphere rose by 5 percent during the past decade.

During the past 40 years, the world has seen an alarming increase in the incidence of malignant skin cancer; the rate today is tenfold higher than in the 1950s. Although the entire increase cannot be blamed on ozone loss and increased exposure to ultraviolet radiation, there is evidence of a relationship. Scientists estimate that for each 1 percent decline in ozone levels, humans will suffer as much as a 2 to 3 percent increase in the incidence of certain skin cancers

Answer 8

We should pray about all of these things because sometimes we see too late when we have all faith in science. Years ago almost all sprays used CFCs. Now we know that CFCs deplete the ozone layer. Additionally, we also know that car and truck emissions deplete the ozone layer, but we do not have a quick answer of fixing that. I think in the future we will learn that other practices of today are depleting the ozone layer. You never know!

Answer 9

From all of the carelessness (aerosol, pollution, experiments) and wear and tear that humans are putting it through on top of some of the natural occurances. The depletion of the ozone layer is a slower process than many people realize. However, it is not something that should be ignored.

Answer 10

It isn't really. That's just a scare tactic perpetrated by radical environmentalists. The ozone layer is being constantly replenished by the sun. It goes through periods of thinning when the earth is rotating on it's axis and a portion of the atmosphere receives less sunlight. Then a couple of months later when the sun hits the atmosphere in that area for longer of periods it rebounds and comes back again.

God knew what He was doing when He put this planet together and it's not like it was a big surprise to Him when mankind developed things like flourocarbons. He knows the end from the beginning and has incorporated wonderful mechanisms to keep this planet livable for us until it's time for it to be destroyed and a new earth will be here.

2 Peter 3:7 But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men. 8 But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day. 9 The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. 10 But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up. 11 Seeing then that all these things shall be dissolved, what manner of persons ought ye to be in all holy conversation and godliness, 12 Looking for and hasting unto the coming of the day of God, wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat? 13 Nevertheless we, according to his promise, look for new heavens and a new earth, wherein dwelleth righteousness. 14 Wherefore, beloved, seeing that ye look for such things, be diligent that ye may be found of him in peace, without spot, and blameless.

Answer 11

The term ozone depletion is used to describe two distinct, but related, observations: a slow, steady decline, of about 3% per decade, in the total amount of ozone in the earth's stratosphere during the past twenty years, and a much larger, but seasonal, decrease in stratospheric ozone over the earth's polar regions during the same period. (The latter phenomenon is commonly referred to as the "ozone hole".) The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the proximate cause of both trends is believed to be catalytic destruction of ozone by atomic chlorine and bromine. The primary source of these halogen atoms in the stratosphere is photodissociation of chlorofluorocarbon (CFC) compounds, commonly called freons, and bromofluorocarbon compounds known as Halons, which are transported into the stratosphere after being emitted at the surface. Both ozone depletion mechanisms strengthened as emissions of CFCs and Halons increased.

Since the ozone layer prevents most harmful UVB wavelengths (270- 315 nm) of ultraviolet light from passing through the Earth's atmosphere, observed and projected decreases in ozone have generated worldwide concern, leading to adoption of the Montreal Protocol banning the production of CFCs and halons as well as related ozone depleting chemicals such as carbon tetrachloride and trichloroethane (also known as methyl chloroform). It is suspected that a variety of biological consequences, including, for example, increases in skin cancer, damage to plants, and reduction of plankton populations in the ocean's photic zone, may result from the increased UV exposure due to ozone depletion.