40th Agenda

40th Session Issues

Depletion of the Ozone Layer

by
Isabel Gutierrez

Man made chemicals, primarily chlorofluorocarbons (CFCs), travel to the upper atmosphere where they catalyze the breakdown of the protective ozone layer. Scientists have warned that even if action is taken ctickly, ozone depletion can be reduced, but not reversed for at least 100 years.

Background

Ozone is composed of three oxygen molecules and. is produced naturally by sunlight. At ground level ozone is a pollutant, but in the upper stratosphere (a segment of atmosphere extending approximately 9 miles to 30 miles above the earth's surface) it forms a layer that protects the earth from the sun's harmful ultraviolet radiation. Although ozone composes a small part of the atmosphere's total mass, it absorbs more than 99% of the sun's ultraviolet radiation.

In small doses, ultraviolet radiation can produce sunburn and has been shown to cause skin cancer in laboratory animals. In greater amounts, however A this radiation can "break apart" important biological chemicals, including DNA. A 1% depletion in the ozone layer allows 2% more ultraviolet radiation to reach the earth's surface. Scientists predict that this would raise the incidence of skin cancer by 4% to 5%.

Increased ultraviolet radiation will also cause an increase in cases of cataracts, suppress human and aniinal immune systems, damage fish larvae, kill off micro-organisms on the ocean floor that serve as food for larger marine life, give some crops 'sunburn", decrease crop yield, and damage man made products such as paints and plastic.

Chlorofluorocarbons CFC's have been shown to contribute to the greenhouse effect (see Issue on Greenhouse Effect). This would result in a partial melting of the ice caps, a rise in sea levels, the disruption of current weather patterns and the decline of agricultural productivity.

Chlorofluorocarbons

Chlorofluorocarbons (CFC's), and chemicals like it, do not bond easily with other chemicals. This makes them nontoxic and ideal for use in manufacturing processes. Because CFCs are so unreactive, they do not decompose in the lower atmosphere as most chemicals do. Instead, they travel up to the stratosphere where the ozone layer exists. There they are broken down by ultraviolet radiation and release chlorine atoms. These chlorine atoms react chemically with ozone molecules and catalyze their breakdown into oxygen molecules. CFCs are used for a variety of purposes. They have been in use for many years and were initially chosen for production because of their great chemical stability. CFC- 11 is used as an aerosol propellant (except in the United States and a few other countries that banned their use for this purpose) and as a blowing agent for foam insulation. CFC-12 is a widely used refrigerant and CFC-113 is used as a solvent in the electronics industry.

After CFC's are emitted, it takes ten years for them to reach the stratosphere. Once there, they can continue to destroy ozone molecules for 75 to 100 years, depending on their type. Most continue for about 100 years with each CFC molecule destroying approximately 100,000 ozone molecules. Compounding this is a process called "banking". Since not all CFCs are emitted at the time of manufacture, some CFCs may take 15 years or more to escape from products such as refrigerators and foam insulation. As a result, CFCs produced today will affect the ozone layer for a century or more."

The United States and Britain are currently developing substitutes for CFCS. Dupont, one of the world's leading producers of CFCs, announced that it now has two possible substitutes for CFCs used as cleaning agents by electronics companies. These account for about 20% of world consumption. Dupont has also stated that it now has good substitute prospects for all major CFC markets.

Other Harmful Chemicals

In addition to CFCs, other chemicals have been shown to destroy the ozone layer. These are methyl chloroform, halon 1211 and 1301, and carbon tetrachloride. Methyl chloroform is used as a cleaner for electronic and metal parts. Halon 1211 and 1301 are used as fire extinguishing agents. Carbon tetrachloride is commonly used in Europe, the Soviet Union and much of the third world as a solvent and is also used in the U.S. as an ingredient in CFCs. Alone, it has a greater potential for destroying ozone than CFCs.

The use of CFCs and halons has been growing steadily since the 1970's. Since then, CFCs have shown an average annual growth rate of 5% to 7% and halons a growth rate of 20%.ls Furthermore, a World Meteorological Organization (WMO) study showed that there is widespread use of carbon tetrachloride in developing countries. Environmentalists say that its use should be discontinued since carbon tetrachloride can be replaced easily and its high toxicity makes it dangerous to both water quality and worker health.

History

Early in 1974 Sherwood Roland and Mario J. Molina of the University of California, Irvine warned that CFCs had the potential to deplete the ozone layer. This was the first warning issued, and since that time, more scientists have agreed with that conclusion and issued their own warnings. The discovery that CFCs destroy ozone molecules caused some controversy and eventually led to the ban of CFCs in aerosols by the United States, Canada and some Scandinavian countries in 1978. However, these countries continued to use CFCs for other purposes. Efforts to ban their use completely were unsuccessful. It was found that chemicals that could destroy ozone on their own, when combined with chlorine, would actually impede the chlorine's ability to destroy ozone molecules. These "interference reactions" were thought to reduce the destruction of ozone molecules. This information led many scientists to believe that the destruction to the ozone layer by CFCs would be minimal. Scientists began developing models to predict and monitor the effects of CFCs and other chemicals on the ozone layer. The theory was that these "interference reactions' would be able to offset the effects of CFCs and therefore, no further cuts were made.

In 1985, scientists from the British Antarctic Survey found that the ozone level above Antarctica had decreased drastically. This discovery prompted the scientific community to reopen the ozone depletion debate. They discovered that the ozone hole over Antarctica had been reoccurring every spring since the 1970's. Scientists have concluded that the ozone level above Antarctica is now about 50% less than in October 1979. The ozone hole above Antarctica is now larger than the size of the U.S.

Normally, the chemical process that destroys ozone in the stratosphere takes place gradually. However, in the case of the Antarctic hole, scientists have discovered that a similar, but much faster process exists. This process makes use of the solar stratospheric clouds (PSC) that form over Antarctica in the winter months.

During the Antarctic winter, the air in the stratosphere becomes very cold and small ice clouds begin to form. CFCs in the stratosphere then condense on the surface of ice particles within these clouds. As a result, when spring arrives and the sun's rays hit the clouds, the CFCs are able to destroy ozone at an unprecedented rate. This period continues until the sun warms up the clouds and causes them to disperse.

Scientists are concerned because these polar stratospheric clouds form over the Arctic as well. They worry that the same chemistry that caused the Antarctic hole may work over the Arctic. The Arctic has experienced a drop of 6% in wintertime levels of ozone since 1970 and the gradual process of ozone depletion can account for only a third of this loss. In addition, scientists now find that there are enough ozone depleting chemicals in the stratosphere over the Arctic to destroy the ozone layer at the rate of 1% a day if conditions are right.

After the discovery of the Antarctic ozone hole, scientists began monitoring ozone levels globally to determine if worldwide decreases could be detected. An international team made up of more than 100 scientists worked for 16 months analyzing all the data available to determine if world-wide ozone depletion existed. On March 15, 1988 they reported that the ozone layer over the Northern Hemisphere had been depleted three times faster than predicted .

The depiction was reported as being as much as 3% in the latitudes spanning much of the U.S., Canada, Western Europe, the Soviet Union, China and Japan and 6% over parts of Alaska and Scandinavia in the winter months. These figures were shocking, since CFC models predicted the same amount of depletion to occur, but over a 70 year period. These figures exemplify the extent to which ozone depletion had been under estimated.

International Action

The discovery of the Antarctic ozone hole made it clear that international regulation of ozone depleting chemicals was necessary. After nearly five years of negotiations, the Montreal Protocol was adopted in September 1987. The treaty was developed with the guidance of the United Nations Environment Program (UNEP) and went into effect January 1989. This new treaty requires signatory countries to reduce their CFC production and consumption by 50% by the year 1999 and also requires a freeze on the use of halons to 1986 levels. Developing countries, such as China, India, and most nations in South America and Africa, are allowed an added ten years to meet these requirements. In the meantime, they are allowed to increase their per capita use so they may continue with planned development. (Western per capita consumption of CFCs is said to be 100 times higher than this).

Industrialized countries are permitted to increase CFC production by as much as 15% provided they export to developing countries. In addition, the Soviet Union is permitted to complete CFC production plants under construction. As a result, under the Montreal Protocol, CFC production will actually grow by as much as 15% in the coming decade making the actual decrease only 35%.

Scientists now say that this 35% reduction will not be enough to curtail further ozone depletion. The Montreal Protocol was created without the incorporation of the 1988 international team's findings. As a result, it was based on 1986 figures that showed a 1% decrease in ozone, rather than the 3% decrease that was found over the Northern Hemisphere. They say that even if all CFC use were stopped today, the ozone layer would continue to be depleted for the next twenty years.

Because of their great stability, 40% of the CFCs now in the air will still be there in the year 2100. The Airborne Arctic Stratospheric Experiment issued a statement saying that even if the Montreal Protocol received worldwide cooperation, chlorine and bromine in the atmosphere would still increase by a factor of 2 by the year 2500. These findings were supported by Canadian scientists. Additionally, Mostafa Tolba, executive director of UNEP has estimated that there will be a decrease in ozone of at least 2% during the next century.

Fortunately, the accord does allow for the reevaluation of the current timetable if new information is discovered. Because of current findings, many countries are going beyond The Montreal Protocol. The twelve nation European Community met in Brussels in March and adopted a plan to stop all production and use of CFCs by the year 2000. They have agreed to cut CFC production to 85% as soon as possible and gradually phase out all production by the end of the century.

Soon after, an international environmental conference was held in London. This conference was sponsored by the United Kingdom in conjunction with UNEP and was attended by representatives from 124 countries. It was designed to cultivate support for a plan to strengthen the Montreal Protocol and to gain new signatories for the treaty.

In May, the signatories to the Montreal Protocol met in Helsinki for the first time since the Protocol's inception. They adopted a declaration calling for a complete phase out of CFC's by the year 2,000 and for a ban on the use of halons as soon as feasible. The declaration also calls for provisions to assist developing countries through funding and transfer of technology. These countries also showed support for the elimination of other harmful chlorine containing chemicals, such as methyl chloroform and carbon tetrachloride. Analysis presented at the conference showed that a ban on CFCs alone will not be sufficient to eliminate the buildup of chlorine in the stratosphere.

One of the main problems facing the regulation of CFCs is that they are used extensively in manufacturing processes. Developing countries fear that their restriction will hinder their ability to continue planned development. Industrialized nations are concerned that as they phase out CFCs, developing countries will "take up the slack". In a recent study, Irving Mintzer, a research scientist with World Resources Institute, stated that if only four developing countries (China, India, Indonesia, and Brazil) increase their consumption of CFCs to the levels allowed by the Montreal Protocol, CFC production on a worldwide basis would double from the 1986 base level.

China and India, the world's two most populated developing countries, have been hesitant to sign the Montreal Protocol and have asked for an international fund to be set up to help them change over to more expensive, but environmentally safe chemicals. They ask that this fund be financed by main producers and consumers of CFCs and also be used to promote research into CFC alternatives and to provide free transfer of technology to developing countries which comply with the Montreal Protocol. Although the two countries currently account for only 10% of the world market, their potential for growth is great. Without their support, the protocol would have very little effect.

Currently, less than 10% of the 1.2 billion Chinese population have refrigerators. China has built twelve CFC plants in an effort to provide its population with refrigerators and raise the the standard of living in that country. India, meanwhile, has stated that it will not accept that foreign assistance for the environment be increased at the expense of other aid. Another obstacle to CFC regulation has been the general disagreement among scientists as to the extent of ozone depletion. Part of the problem is that they have relied on models to predict ozone depletion from manmade chemicals. The models attempt to reduce the earth's climate to a set of grids and numbers based on the physical laws of motion and thermodynamics. These models are not always accurate. Before the Antarctic ozone hole was discovered, climate models had not factored in the presence of ice clouds (PSCS) in the Antarctic stratosphere. Most scientists agree that manmade chemicals are destroying the ozone, but they disagree on the severity.

United Nations Involvement

The United Nation 's Environment Program initiated work in 1981 aimed at the elaboration of a global framework for the protection of the ozone layer. After several years of negotiations, the Vienna Convention for the Protection of the Ozone Layer was adopted in March 1985. The convention provides for international cooperation in research, monitoring, and exchange of data. This was the first time that the international community had recognized a need for action on an environmental problem before actual damages were recorded. Agreement was not reached at that time, however, on concrete measures to control ozone depleting chemicals. Instead, a process was launched to improve understanding of the nature and impacts of ozone depiction and to narrow differences in various countries' approaches to the problem. This process included: two UNEP workshops, in Rome in May 1986 and in Leesburg, Virginia in September 1986, on key economic and conceptual issues related to the control of ozone-depleting chemicals; an international conference in June 1986, cosponsored by the U.S. Government and the UNEP, on the effects of ozone depletion and climate change; and detailed assessments by the international scientific community of atmospheric science and the effects of ozone depletion. A highlight was the publication of a document on atmospheric ozone, prepared by 150 scientists coordinated by Dr. Robert Watson of NASA, under the sponsorship of NASA, the UNEP, the World Meteorological Organization, the European Commission, NOAA (National Oceanic and Atmospheric Administration), FAA (Federal Aviation Administration) and the German Federal Ministry for Research and Technology.

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