The Ozone Layer: Earth's Sunscreen
 Report compiled by Funsho Olamigoke

Ozone-depleting substances usually contain chlorine or bromine

What exactly is the ozone? Ozone is a form of oxygen. Each ozone molecule is made of three oxygen atoms, so its chemical formula is O3 . But unlike oxygen, ozone is a poisonous gas, and an increase in its concentration at ground level is not something that we want. But in the stratosphere, where ozone exists naturally, it blocks out the sun's devastating ultraviolet rays from hitting planet earth and its inhabitants.
 

  A natural balance keeps us well supplied with ozone

Up in the stratosphere, small amounts of ozone are constantly being made by the action of sunlight on oxygen. At the same time, ozone is being broken down by natural processes. The total amount of ozone usually stays constant because its formation and destruction occur at about the same rate. Human activity has recently changed that natural balance, unfortunately. For the ozone layer to continue to shield our Planet from the sun's intense ultraviolet radiation, which it does by absorbing nearly all of the biologically damaging UV radiation from the sun, the ozone itself has to be protected. It isn't as much of what we do to protect it like we ought not to do that exposes it to depletion. Of serious concern here is the fact we all have, one way or another, even in very simple ways contributed to the on-going depletion of the protective ozone layer, such as in the use of a hair spray, insecticides, Freon-12 or 22 (gas for automobile and domestic air conditioners), smoky automobile exhausts, leaded fuel, bush burning, and many more of our day to day substances that otherwise are non-toxic. Of higher sophistication and greater depletion consequences are certain other manufactured substances (such as chlorofluorocarbons and hydro-chlorofluorocarbons) which can destroy stratospheric ozone much faster than it is formed. Many substances other than chlorofluorocarbons are also ozone-depleting. Examples are carbon tetrachloride (used in dry cleaning), and methyl bromide (used as an insecticide for soil fumigation). Ozone-depleting substances are long-lived because it takes them several years to drift up into the stratosphere. When they arrive, they are broken apart by exposure to ultraviolet radiation and that releases the chlorine atoms. These are the real ozone-killers. The chlorine atoms react with ozone, to form oxygen and chlorine monoxide.

Ozone Hole: Antarctica is the worst affected area, probably because the air above it is most isolated from the rest of the atmosphere. Scientists often refer to the part of the atmosphere where ozone is most depleted as the ‘ozone hole’, but it is not really a hole – just a vast region of the upper atmosphere where there is less ozone than elsewhere.

Cosmic conspiracy.
Cosmic rays could be a major contributor to ozone destruction over Antarctica.Cosmic rays may be enlarging the hole in the ozone layer, according to a recent study. Researchers analyzed data from several sources, and found a strong correlation between cosmic ray intensity and ozone depletion. Back in the lab they demonstrated a mechanism by which cosmic rays could cause a buildup of ozone-depleting chlorine inside polar clouds. Their results suggest that the damage done by cosmic rays could be millions of times larger than anyone previously believed and may force atmospheric scientists to reexamine their models of the Antarctic ozone hole.

For just one moment, imagine a very sunny day with the sun scotching and biting real hard at your skin. Then imagine again that the next moment, you have a giant umbrella held over you, most naturally, you feel a lot better even though you are still out there in the sun. In much the same way that the umbrella shields the heat on a hot day, the ozone layer in the stratosphere blocks out the sun’s deadly ultraviolet rays.

Global Concern
An international agreement called the Montreal Protocol limits the production and use of ozone-depleting substances. A slowing down in the rate of ozone loss has been measured, and the concentration of CFCs in the atmosphere is leveling off. The rate at which ozone is being destroyed in the upper stratosphere is slowing, and the levels of ozone-destroying chlorine in that layer of the atmosphere have peaked and are going down, the first clear evidence that a worldwide reduction in chlorofluorocarbon pollution is having the desired effect. If all countries keep to the targets set by the international community in the amendments to the Montreal Protocol, the ozone in the stratosphere should eventually recover.

CFCs, previously used as refrigerants, foam-blowing agents and propellants in spray cans, are now banned worldwide. Their temporary replacements, the hydro-chlorofluorocarbons, are still slightly ozone-depleting, though not to the same extent. HCFCs are also being phased out.
                                                                                                                                              GLOSSARY