THE OZONE LAYER: ITS DESTRUCTION AND THE ATTEMPT TO SAVE IT
By Larissa Fontaine
3/12/99
It is important to have a protected and safe environment for any organism to survive. On Earth all life forms owe their survival to the atmospheric layer that surrounds the planet and more specifically the ozone molecules in the atmosphere. These molecules constitute less than one thousandth of a percent of the atmosphere yet are crucial to providing usable air and absorbing the ultraviolet rays from the sun to regulate temperature. The gradual depletion of the ozone layer went undetected for many years and while it may seem that it has been a global issue for a long time, it is only in the past 25 years that the ozone layer has even been identified as a problem. The dramatic discovery of the depletion and the drastic measures taken to resolve the issue have progressed quickly, from the diagnosis of the problem to the research of possible solutions to decisive action taken by international governments. Following is a brief overview of the causes of ozone depletion, the dangerous impact of this depletion and the action that has been taken to reverse the damage that has occurred.
The most critical molecules of ozone exist in the upper portion of the atmosphere called the stratosphere. The stratosphere is the section of the atmosphere located between 10km and 50km above the earth. Ozone is created by chemical reactions between oxygen and the sun’s ultraviolet rays, the O2 molecules are split apart and while they are in this volatile state they reattach to other O2 molecules creating O3, ozone. Ozone is also constantly destroyed by natural elements such as seasonal cycles and volcanic eruptions. These creative and destructive forces maintain a steady balance in the atmosphere, or did for billions of years until humans upset the cycle. (See Appendix A for a complete chemical explanation of ozone breakdown.)
There are several components of the gradual destruction of the ozone layer. Methyl bromide, a harmful pesticide used on crops, has caused a dangerous amount of bromine to accumulate in the stratosphere. Bromine undergoes a chemical reaction at this high altitude when it interacts with the sun’s ultraviolet rays, which destroys ozone molecules. The reduction of bromine in the stratosphere alone would dramatically improve the state of the ozone, since bromine has possibly the most instantly destructive effect on ozone molecules.
Research and development of new high speed air travel (Supersonic Transport, SST) was brought to an abrupt halt when it was believed that the effects of the airplanes on the ozone may be incredibly destructive. The aircraft would travel high in the atmosphere at speeds faster than the speed of sound. The high density of harmful chemicals released directly into the high altitude from the exhaust would clearly add to the already extensive destruction of the ozone. The exhaust produced (NO and NO2) reacts with ozone molecules in a destructive manner, breaking apart ozone molecules and increasing ozone depletion. The process of the chemical reaction is relatively simple:
These aircraft were once thought to be the future of air travel. However, the importance of protecting the environment ended all plans of a SST fleet, focusing research efforts down more environment friendly avenues.
Chlorofluorocarbons (CFC’s) are possibly the most well known ozone destroyers. A widely used set of chemicals, they have been discovered to have harmful effects on the ozone and the public has become very well informed about the danger of continued CFC usage. CFC’s are compounds comprised of chlorine, fluorine and carbon atoms. They have ideal properties being nontoxic, noncorrosive and nonflammable and are most commonly known as the aerosol used in spray cans. However, the areas in which they are most overused are as coolants in refrigerators and air conditioners. It was not until 1974 that CFC’s were identified as harmful chemicals after decades of extensive use. Two chemists, F. Sherwood Rowland and Mario Molina, discovered that although CFC’s were stable compounds in the lower atmosphere once they floated into the stratosphere they became extremely unstable. The amount of chlorine atoms that were separated from the CFC molecules dramatically increased the chlorine present in the stratosphere, having huge repercussions for the ozone layer. According to further research each chlorine atom can destroy up to a hundred thousand ozone molecules.
The effects of ozone harming chemicals operate on cycles and heat levels similar to the natural production and destruction of ozone molecules. Over the Antarctic ozone levels drop below normal during the spring and then gradually rise again over the summer. However, in 1985 scientists discovered that the yearly drop in the spring had been increasing, indicating a growing ozone “hole”. The Antarctic is particularly conducive to breaking down ozone for several reasons. The icy climate traps the potentially harmful compounds inside ice particles, ensuring that the compounds remain directly above the Antarctic. The ice also reacts with the chemicals, breaking apart the chlorine and bromine compounds very easily, releasing the destructive elements into the atmosphere. Research expeditions continued, finally resulting in the announcement that ozone levels had dropped not only in the winter and spring but also in the summer, leaving little hope that the initial findings were incorrect. In 1987 ozone levels above Antarctica dropped below half of their normal area and the newly identified ozone hole covered an area the size of the United States.
The effects of ozone depletion are grave. With less of a shield from the sun more ultraviolet rays can penetrate the stratosphere and reach the earth’s surface. This exposure harms plant life as well as increases risks for cataracts and skin cancer. Also, more harmful gases reach the lower atmosphere and add to the temperature increase by creating a greenhouse effect. The depletion of the ozone leads to higher risks for disease and changes the earth’s entire ecosystem. The immediate harmful effects to plant and animal life, combined with the changes in global temperatures and levels of ultraviolet rays reaching the surface, result in a very unstable interaction between lifeforms.
Extensive research has been conducted since identifying the ozone problem to figure out some way to reverse the damage. It is impossible to create ozone, but by reducing the use of harmful agents it is believed that the ozone layer should regulate itself and be able to regain the necessary levels of ozone. The hope is that by reducing the amount of chemicals that destroy ozone, the natural process of creating and dissolving ozone will resume and will eventually regain initial levels. Despite the serious consequences that accompany the ozone depletion there has been one positive result of the ozone crisis. The magnitude of the problem has had an incredibly unifying effect on different countries throughout the world. Never before has nearly every country come together so quickly and agreed on a plan of action that each then proceeded to genuinely attempt to follow.
The depletion of the ozone was first observed in 1974. By 1976 CFC’s had been identified as a serious problem and a possible cause of the ozone depletion. Public awareness was raised and change was demanded. The United States was at this time the world’s largest producer and consumer of CFC’s. The government was pressured by the public to enforce regulatory laws that would reduce production and force companies to decrease their use of CFC’s. Protest groups were also formed that called for boycotts and other decisive action. The U.S. government responded by banning the sale of aerosol cans, which pleased the public interest groups, but many companies continued to use CFC’s in other processes that were not as well publicized. While it appeared that action had been taken against harmful ozone depleting chemicals, other countries continued using aerosol cans as well as other products that utilized CFC’s. And the amount of CFC’s being released into the stratosphere continued to increase.
The continued CFC usage and depletion of ozone levels soon inspired worldwide action and various countries met in Vienna for The Convention for the Protection of the Ozone Layer in 1985. The generalized treaty that was eventually agreed upon was an important step in the process of ending dangerous chemicals. However it was relatively weak in establishing actual legislation. The result of the convention was an agreement to take “appropriate measures… to protect human health and the environment against adverse effects resulting in or likely to result from human activities which modify or are likely to modify the Ozone Layer.”[1] This vague contract did not mention any specific chemicals, such as CFC’s, and named no specific action to be taken. Still, it did set a critical precedent for a worldwide focus on environmental issues. The Montreal Protocol on Substances that Deplete the Ozone Layer in 1987 was an important result of the standards set in Vienna in 1985.
The Montreal Protocol furthered the precedent set by The Vienna Convention. Environmental ministers from 24 countries agreed to take strong decisive action against the use of CFC’s and Halons (includes bromine compounds). The initial treaty stated that by the middle of 1989 countries would hold their production and use of the chemicals at the levels reached in 1986. Then the production and usage would be reduced by fifty percent over the next ten years. The treaty was left open to modification and amendments leaving room for improvements should they be necessary. The original representatives agreed to reconvene in 1989 to reevaluate the situation and examine the action that had been taken and whether it was sufficient.
The intense research that was conducted during the late 1980’s determined a great need for stronger action. If the initial plan was followed, ozone levels would continue to fall and the problem would increase and eventually become even harder to reverse. At the next convention in 1990, government representatives met in London and intensified control provisions. Three more amendments have been made since, in 1992 in Copenhagen, in 1995 in Vienna, and in 1997 in Montreal. Further studies demanded these amendments, bringing new information and more frightening statistics.
The graph below shows the clear decrease in ozone levels just from 1979 through 1993. As shown, the levels in 1991 were in range with the levels from 1979-1990, definitely on the lower end of the spectrum. Then there is a noticeable decrease in 1992 followed by a dramatic decrease in 1993. This decrease occurred after several revisions of The Montreal Protocol when action had been taken and programs had been put into place to decrease ozone destruction. Clearly the amendments made in 1990 and 1992 had not been enough to slow ozone depletion which is what warranted the further amendments.
The ninth meeting of The Montreal Protocol in September of 1997, addressed the current status of the ozone hole and the action being taken. Excess production of CFC’s and Halons has continued in several countries and scientists’ early predictions are feared to be too conservative. Russia’s non-compliance in addition to developing countries’ excess consumption of CFC’s has delayed the peak years for ozone depletion and thus delayed the projection time for ozone recovery. Since 1994 the belief has been that ozone depletion will peak in the late 1990’s and that all use of ozone depleting chemicals will end by 2045. However, the CFC production for 1997 exceeds projection numbers by two hundred percent. This is due primarily to the continued production of CFC-dependent refrigeration and cooling systems in underdeveloped countries and the black market demand in industrialized nations. The high levels of continued CFC production and consumption delays the Protocol’s CFC phase-out plan four years, inflates the numbers that were used to predict other chemical phase-out plans and alters all previous calculations. Some action is being taken but there is little that the Protocol delegates can do other than promote awareness and encourage legislation. One successful accelerated phase-out did occur when industrialized countries agreed to a new methyl bromide phase-out year of 2005, five years sooner than the previous agreement of 2010. However, this progress was not thought to be remarkably aggressive and many of the countries involved are very discouraged at the lack of improvement that is being made. The Montreal Protocol’s complete phase-out schedule is located in Appendix B.
The depletion of the ozone layer is a worldwide problem that threatens the health and survival of all life on earth. The action that is being taken, while conscientious and consistently addressed, is not an aggressive attack of the problem. The Montreal Protocol has not demanded enough of its representatives and production of harmful chemicals has not been reduced or regulated adequately. The problem is a grave one and grave action needs to be taken to prevent the terrible consequences of negligence.
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http://www.unep.org/unep/secretar/ozone.html
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