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In the hydrosphere, ultraviolet radiation is penetrating to depths never previously seen, while the lithosphere's volcanoes periodically spew sulfates and chlorine into the atmosphere. At the same time, in the realm of humans (the anthrosphere), manmade chemicals are continually being introduced into the other spheres. Are these events happening in isolation, or are they interrelated? The answer to this question is important to the future of the entire Earth system.

Ozone is a very important gas, because stratospheric ozone absorbs most harmful ultraviolet radiation, preventing it from reaching Earth's surface. In the 1970s, researchers began to think that human activity could affect the ozone, even though they were focusing on the exhaust from supersonic airplanes and the space shuttle. However, after studying other possible causes for ozone depletion, the international community came to a consensus that certain manmade chemical compounds called chlorofluorocarbons (CFCs), were largely responsible for the ozone loss. As a result, the Montreal Protocol was adopted in 1987, calling for the worldwide elimination of CFCs and other ozone-destroying substances. So far, the Montreal Protocol has been signed by more than 160 nations. Image: Courtesy of NASA

The Protocol has been updated several times, most recently in 1995. Since knowledge of the ozone depletion problem continues to increase rapidly, the director of the United Nations Environment Programme (UNEP) plans another update.

Nevertheless, there are still many (including some vocal scientists) who would like to abandon the Montreal Protocol. Some think a causal relationship has not been proved, while others contend that enforcement of the Montreal Protocol is too costly. In fact, in 1996, legislation was introduced in the US Senate that would have ended United States compliance. On the other side, however, there is concern that the Montreal Protocol is too lax on its control of some substances. The director is aware of this but is also concerned about developing countries and countries that have not yet signed the protocol. As a result, your group has been called upon to act as consultants to review the many issues that surround ozone depletion.

Your role is to evaluate the current status of the Montreal Protocol and determine if it adequately considers the interrelationship of Earth's spheres. To do this, you must investigate how an event in one sphere may have an effect in a second sphere, which may, in turn, affect a third sphere. You should determine if there is a need to revise the Protocol. In any event, you must be well prepared to defend your recommendations.

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