THE PROTECTOR - OZONE LAYER

In 1998, in recognition of the Protocol's unique accomplishments, the General Asembly in its Resolution 49/114 named 16 September as the International day for the Preservation of the Ozone Layer. Since that time, the Parties have used this day to celebrate the signing of the Montreal Protocol, and the significant environmental and health benefits that this amazing treaty has yielded.
The Montreal Protocol is celebrating its 25th Anniversary this year.

Q. What is ozone and where is it in the atmosphere? Ozone is a gas that is naturally present in our atmosphere. Each ozone molecule contains three atoms of oxygen and is denoted chemically as O3. Ozone is found primarily in two regions of the atmosphere. About 10% of atmospheric ozone is in the troposphere, the region closest to Earth (from the surface to about 10–16 kilometers (6–10 miles)). The remaining ozone (about 90%) resides in the stratosphere between the top of the troposphere and about 50 kilometers (31 miles) altitude. The large amount of ozone in the stratosphere is often referred to as the “ozone layer.

Q. How is ozone formed in the atmosphere?
Ozone is formed throughout the atmosphere in multistep chemical processes that require sunlight. In the stratosphere, the process begins with an oxygen molecule (O2) being broken apart by ultraviolet radiation from the Sun. In the lower atmosphere (troposphere), ozone is formed by a different set of chemical reactions that involve naturally occurring gases and those from pollution sources.

Q. Why do we care about atmospheric ozone? 
Ozone in the stratosphere absorbs a large part of the Sun’s biologically harmful ultraviolet radiation. Stratospheric ozone is considered “good” ozone because of this beneficial role. In contrast, ozone formed at Earth’s surface in excess of natural amounts is considered “bad” ozone because it is harmful to humans, plants, and animals. Natural ozone near the surface and in the lower atmosphere plays an important beneficial role in chemically removing pollutants from the atmosphere.
Q. How is total ozone distributed over the globe?
The distribution of total ozone over the Earth varies with location on timescales that range from daily to seasonal. The variations are caused by large-scale movements of stratospheric air and the chemical production and destruction of ozone. Total ozone is generally lowest at the equator and highest in polar regions.
Q. How is ozone measured in the atmosphere? 
The amount of ozone in the atmosphere is measured by instruments on the ground and carried aloft on balloons, aircraft, and satellites. Some instruments measure ozone locally by continuously drawing air samples into a small detection chamber. Other instruments measure ozone remotely over long distances by using ozone’s unique optical absorption or emission properties.
Q. What are the principal steps in stratospheric ozone depletion caused by human activities?
The initial step in the depletion of stratospheric ozone by human activities is the emission, at Earth’s surface, of gases containing chlorine and bromine. Most of these gases accumulate in the lower atmosphere because they are unreactive and do not dissolve readily in rain or snow. Natural air motions transport these accumulated gases to the stratosphere, where they are converted to more reactive gases. Some of these gases then participate in reactions that destroy ozone. Finally, when air returns to the lower atmosphere, these reactive chlorine and bromine gases are removed from Earth’s atmosphere by rain and snow.
Q. What emissions from human activities lead to ozone depletion? 
Certain industrial processes and consumer products result in the emission of ozone-depleting substances (ODSs) to the atmosphere. ODSs are manufactured halogen source gases that are controlled worldwide by the Montreal Protocol. These gases bring chlorine and bromine atoms to the stratosphere, where they destroy ozone in chemical reactions. Important examples are the chlorofluorocarbons (CFCs), once used in almost all refrigeration and air conditioning systems, and the halons, which were used in fire extinguishers. Current ODS abundances in the atmosphere are known directly from air sample measurements.

 The debate over the existence of an ozone problem breeds media coverage. However, the real story is not whether stratospheric ozone levels are decreasing, but what those decreases may mean for life on earth. As the percentage of ozone in the atmosphere decreases, the amount of UV-B radiation reaching the surface increases. It's the UV-B radiation, not the ozone itself that concerns scientists, because the invisible wavelengths are linked to skin cancers and other biological damage.
Measuring UV-B is tricky. Levels are affected by time of day, day of the year, latitude, weather conditions, and the amount of ozone aloft. UV is the part of the electromagnetic spectrum made up of wavelengths between 280 and 400 nanometers (billionths of a meter). Most of this is UV-A light, only mildly associated with sunburn and DNA damage and relatively benign to most plant life. But the ill effects increase more than a thousandfold in the shorter wavelengths referred to as UV-B. Below 300 nanometers, the rays are sparse but very damaging; near 315 nanometers they're more numerous but much less destructive. Close to 310 nanometers lies the middle ground, where the number and impact of rays combine to cause the greatest harm to humans and plants. Engineers face enormous challenges when designing instruments that can measure individual wavelengths, yet such precision is necessary to determine the amount of dangerous light entering the atmosphere.
The Story of the Ozone Hole
Although often referred to as the ozone 'hole', it is really not a hole but rather a thinning of the ozone layer in the stratosphere. We will use the term 'hole' in reference to the seasonal thinning of the ozone layer.
The appearance of a hole in the earth's ozone layer over Antarctica, first detected in 1976, was so unexpected that scientists didn't pay attention to what their instruments were telling them; they thought their instruments were malfunctioning. When that explanation proved to be erroneous, they decided they were simply recording natural variations in the amount of ozone. It wasn't until 1985 that scientists were certain they were seeing a major problem.

Why did it take scientists so long to solve this mystery? To begin with, observations that challenge preconceived ideas don't always get taken seriously, even in science. Two decades ago scientists did not suspect the importance of the chemical processes that rapidly destroy ozone in the Antarctic stratosphere. When they saw dramatic fluctuations in ozone levels, they assumed their instruments were in error, or that whatever was happening was due to natural processes like sunspot activity or volcanic eruptions.

They didn't realize that chlorine was the main culprit and that most of the chlorine in the stratosphere comes from human activity. The largest source is a class of chemical compounds known as chlorofluorocarbons (CFCs).

Because of their chemical stability, low toxicity, and valuable physical properties, these chemicals, versatile and stable in the lower atmosphere, at least, have been extensively used since the 1960s as refrigerants, industrial cleaning solvents, propellants in aerosol spray cans, and to make Styrofoam.

At the turn of the century, chlorine levels in the stratosphere were much lower than at present. As the use of CFCs has increased, however, so has their concentration in the atmosphere. Scientists could detect 100 parts per trillion (ppt) of CFC-12 in the atmosphere by the 1960s, 200 ppt by 1975, and more than 400 ppt by 1987. By 1990, they detected more than 750 ppt of CFC-11 and CFC-12, the two most destructive and persistent CFCs.

Once in the atmosphere, CFCs drift slowly upward to the stratosphere, where they are broken up by ultraviolet radiation, releasing the chlorine that catalytically destroys ozone. In the graphic below, the destructive cycle of a chlorine atom is shown.

1. UV radiation breaks off a chlorine atom from a CFC molecule.
2. The chlorine atom attacks an ozone molecule (), breaking it apart and destroying the ozone.
3. The result is an ordinary oxygen molecule () and a chlorine monoxide molecule (ClO).
4. The chlorine monoxide molecule (ClO) is attacked by a free oxygen atom releasing the chlorine atom and forming an ordinary oxygen molecule ().
5. The chlorine atom is now free to attack and destroy another ozone molecule (). One chlorine atom can repeat this destructive cycle thousands of times.

The following animation shows the destruction of an ozone molecule by a chlorine atom.

Since 1974 scientists have known that chlorine can destroy ozone, but no one thought the destruction would be very rapid. Events over the Antarctic region proved them wrong. The ozone hole story began at Halley Bay in Antarctica, where British scientists had been measuring ozone in the atmosphere since 1957. In 1976 they detected a 10% drop in ozone levels during September, October, and November—the Antarctic spring. Since ozone concentrations over this region often vary from season to season, the researchers weren't concerned, even as the springtime declines occurred repeatedly. It wasn't until their instruments registered record low levels of ozone in 1983 that they realized something important was happening. By then, record springtime ozone declines had occurred during seven of the previous eight years.

Within two years, scientists determined that the ozone hole over Antarctica occurs when high levels of chlorine catalytically destroy ozone. The high levels of active chlorine are formed in the cold, dark winter stratosphere when reactions on the surface of icy cloud particles release chlorine from harmless (to ozone) chemical compounds into an active form that reacts with ozone. When the sunlight returns to the polar region in the austral spring, the active chlorine rapidly begins to destroy ozone. The extremely cold ice clouds can form over both poles during winter, but they are more common over the Antarctic region. During winter, atmospheric circulation creates a whirlpool, or vortex, of air above both poles. Very low temperatures occur inside a polar vortex, which is isolated from the rest of the atmosphere. The extreme cold fosters the formation of ice clouds during the winter and paves the way for the destruction of ozone when the light returns during spring. Scientists documented this mechanism in a series of field experiments in 1987. The graphic below compares the ozone averages (measured in Dobson Units) over Antarctica for the periods 1970-72, 1979, and 1992-95.

The Arctic region is typically spared the worst of the ozone destruction because its vortex normally breaks down several weeks before the sun returns, dissipating the ice clouds. The larger percentage of land masses in the northern latitudes, particularly mountains, prevents an excessive build-up of ice clouds. Geography isn't always enough to dissipate the vortex, however. The North Pole's vortex was unusually strong and long-lived during the winter of 1992-1993, for example. When sunlight appeared, it drove down Arctic ozone levels well into March. Because there is more ozone over the North Pole to begin with, this decline didn't create a hole. However, it did send ozone-depleted air over populated areas of the Northern Hemisphere when the vortex broke up.

The loss of ozone over populous regions underscores the importance of following up on the 1987 Montreal Protocol. This agreement, now signed by more than 70 countries, set goals of reducing CFC production by 20% (relative to 1986 levels) by 1993 and by 50% by 1998. These targets have since been strengthened to call for the elimination of the most dangerous CFCs by 1996 and for regulation of other ozone-depleting chemicals. The United States and other nations are well on their way to meeting these goals. In 1993, global CFC production was already down 40% compared to 1986 levels. That's fortunate, since the CFCs already in circulation will continue to pose a threat to the earth's ozone layer for another hundred years. There is good news to this story. The graph below shows the skyrocketing path of CFC-11 from the 1950s until the mid-1990s. Recent measurements have shown a clear decline in CFC-11.

     your duty for this mother earth 

… YOUR CONSUMPTION

The first step to reducing your impact on the environment, is reducing the amounts of resources you consume and use. Think twice before you buy or use anything. Do you really need it? By reducing your consumption you will also decrease the amount of waste you produce.

… YOUR WASTE

There are also many other ways to reduce your waste. The opportunities are nearly endless. Here are just a few ideas.

Think before you print or photocopy! Print and copy as little as possible. Edit on screen, not on paper. Use e-mail to minimize paper use. Send and store documents like necessary papers and business proposals electronically instead of on paper. When you must print or copy, do it double-sided. Circulate documents instead of making an individual copy for everyone. Change the margins on your Word documents. The default margins on the documents you print are 1.25 inches on all sides. Simply changing the margins to 0.75 inches will reduce the amount of paper you use by almost 5 percent.

… YOUR ENERGY CONSUMPTION

There are so many ways of optimizing your energy consumption

Turn off unused or unneeded lights. Use natural lighting instead of electric lighting whenever possible. If you have a desk lamp, make sure it uses fluorescent bulbs (instead of incandescent bulbs). Dress appropriate to the season Select cold water for washing clothes Keep windows and doors closed in heated and air-conditioned areas. Turn off computers when they are not in use. Turn off printers, especially laser printers, unless printing. Don’t use power strips to turn on all computers and desk equipment at once. When purchasing computers and peripherals, buy low wattage equipment Minimize use of screen savers and instead enable power management features Purchase only energy-efficient products Move your refrigerator. Leaving space between your refrigerator and the wall increases air circulation around the condenser coils, allowing the fridge to operate more efficiently.

… YOUR OIL CONSUMPTION AND POLLUTION

Drive Efficiently -  If you must drive, buck the trend toward more wasteful vehicles and drive a fuel efficient car, i.e. one which gets more miles per gallon, and don’t drive it more than you really need to!   Park your car in the shade. Gas evaporates from your fuel tank more quickly when you park in the sun. Parking in the shade lowers the temperature in your gas tank by up to 7 degrees, significantly reducing fuel evaporation.

REUSE

Plastic containers can become food storage, paper can become wrapping paper. The ways in which to reuse things are unlimited. All you need is to be creative. If being creative is not your thing, here are some other ideas:

Reuse envelopes by placing a new label over the old address. Designate a box for scrap paper and use it for printing all drafts or unofficial documents. Reuse plastic bags or better get a reusable canvas bags.

RECYCLE

When buying any type of product, see if it is available with post consumer recycled content.

Wrap presents in gift bags. Once you tear the wrapping paper off a holiday gift it ends up in the recycle bin, but gift bags can be used over and over again. Production of recycled paper uses only half the water and 3/4 of the energy than new paper Every ton of recycled paper saves almost 400 gallons of oil, three cubic yards of landfill space and seventeen trees.  If you recycle soda cans, the energy used and air pollution created, is 95 percent less than if the cans were produced from raw materials.  You could operate a TV set for an estimated three hours with the energy saved by recycling just one aluminum can

Thinking green means being aware of our interconnectedness with the world and reflecting on the unintended damage we cause nature in the daily course of our lives. Thinking green leads to acting green - taking corrective action to make environmental responsibility a reality.

"Every person is the right person to act. Every moment is the right moment to begin". THE Time to Act is Now!

              

                                                                                                

                                                             
                                                                     thank you 





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