Saving the shield



Saving the shield



MARIO J. MOLINA

describes the success of the Montreal Protocol
in protecting the Earth's endangered ozone layer





diving whale

There has been enormous scientific and technological progress this century, particularly in industrial countries. The quality of life has increased in many ways - average life expectancy, for example, has more than doubled in these past 100 years. On the other hand, it is now clear that the degradation of the environment is an unintended consequence of this progress. People first started altering the surface of this planet thousands of years ago, when they began to establish settled communities and develop an agriculture that required ploughing, irrigation and the clearing of forests. In the past, most environmental problems were local or regional. But, in recent years we have come to recognize that the impact of human activity on the environment has reached global proportions. The problems are now affecting the entire planet because they occur so often and in so many places. Another set of problems comes about as a result of global-scale changes in the chemical composition of the atmosphere that cause environmental effects far from the source of contamination.

The 'greenhouse' effect is one example. Emissions from the burning of fossil fuels have led to a major increase in the amounts of carbon dioxide in the atmosphere - and the amounts of other gases such as methane, nitrous oxides and chlorofluorocarbons (CFCs) have increased as well. All these gases trap infrared radiation, affecting the Earth's energy balance. The scientific community generally agrees that this effect may significantly alter the rainfall and temperature patterns worldwide during the 21st century. Natural variations in climate already have enormous impact on our lives, so the prospect that human activities might trigger undesirable changes in climate has led to widespread agreement that we urgently need to improve our capability to understand the Earth's system and predict climate so as to inform the public and policy makers. This has emerged as one of the greatest challenges for the 21st century that we face in the natural sciences.



Unprecedented agreement

Perhaps the best understood global environmental issue involves CFCs and the ozone layer. CFCs are extremely inert chemical compounds and were developed as replacements for toxic refrigerants, such as ammonia and sulphur dioxide. But, their very inertness allows them to reach the stratosphere, where high-energy ultraviolet radiation breaks them down to chlorine atoms, which in turn combine with ozone, thus depleting the ozone layer that protects life on Earth from harmful solar ultraviolet radiation. The CFCs are released predominately in the Northern Hemisphere, yet the most striking effects of their release occur over the South Pole - far remote from the sources.

There are two important lessons to be learned from the CFC-ozone depletion phenomenon: first, that people are clearly capable of perturbing the environment on a truly global scale; and second, that people are also capable of solving such global-scale problems.

The CFC problem is largely under control, thanks to the Montreal Protocol on Substances that Deplete the Ozone Layer - an unprecedented international agreement negotiated under the auspices of UNEP. Formulating the Montreal Protocol required the participation of scientists, industry representatives, policy makers and environmentalists: it is a very important precedent demonstrating how all these different sectors of society can work together and can be very productive functioning collaboratively rather than adversarially. The Protocol also established a new way of addressing environmental problems: the original agreement was negotiated on the basis of the ozone depletion theory - which predicts that human-made CFCs would deplete the stratospheric ozone layer - rather than on direct unambiguous observation of noticeable damage to the ozone layer from CFCs.

In another important precedent, the Protocol includes procedures for periodic revisions of its terms: as new scientific evidence of globally occurring ozone depletion became available, the agreement was modified and strengthened - first in 1990 in London, and then again in 1992 in Copenhagen - leading to a complete ban on the production of CFCs by industrialized countries by the end of 1995. The agreement also attempts to make the phase-outs fair for the developing countries: the revised agreement establishes the Multilateral Fund - provided by developed nations - to help developing countries adopt and develop 'ozone-friendly' technologies.

The scientific evidence behind the CFC-ozone depletion issue is very strong indeed: there is little doubt that stratospheric ozone has been decreasing in recent years - particularly at high latitudes - and it is well established that this is a consequence of the release of industrial compounds, mainly CFCs. It is also clear that ozone depletion causes ultraviolet radiation levels to increase at the Earth's surfaces - though much remains to be learned about the overall impact of these increased levels on the biosphere. Despite this incomplete knowledge, the decision to call for a worldwide CFC ban is well justified. The ozone layer is a very large natural system that provides an essential life-support function: the amount of solar energy absorbed by atmospheric ozone is more than ten times larger than the total amount of energy utilized by humankind. Scientific research has provided several crucial examples of ecological systems that are very sensitive to the level of ultraviolet radiation, such as certain fish larvae, amphibian eggs, and soy bean crops, etc. There are effects on humans themselves: excessive exposure to UV radiation is linked, for example, to higher incidence of skin cancer, eye cataracts and weakened immunity. There is also a basic understanding of these effects down to the molecular and biochemical level, in terms of damage to the DNA molecule.



Decisive action

Atmospheric scientists estimate that if the global production of CFCs had continued unrestricted, globally averaged ozone depletion would have been close to 10 per cent by the year 2000, instead of the 4 per cent measured today, and the damage would have been much more dramatic in subsequent decades, particularly at high latitudes. We are indeed fortunate that much of the basic scientific research in stratospheric chemistry was in place when the ozone hole was discovered in 1985, thus allowing the policy makers to take decisive action to protect the ozone layer. Ozone depletion is expected to reverse and recover measurably towards the beginning of the next century. And, of course, society still enjoys the benefits of refrigeration, air conditioning, plastic foams, aerosol cans, etc. - but now with new, CFC-free technologies.

My own experience with the CFC-ozone depletion phenomenon prompts me to believe that we can meet the challenge presented by global environmental issues in the 21st century. My optimism stems from observations of major changes in people's attitudes about environmental problems when considering that the health of the entire planet is at stake. We must change our view of the world and adopt new ways of thinking. The quality of life of future generations will be based to a large extent on our ability to deal intelligently with these global problems.

One of the key steps in any rational approach to addressing global environmental issues is to promote internationalism - a widespread understanding that all our human problems are interconnected. Regional and international cooperation will be essential to the solution of environmental problems, and UNEP has shown us the way to achieve it successfully.

Professor Mario Molina, joint winner of the 1995 Nobel Prize for Chemistry for his work on ozone depletion, is Professor of Atmospheric Chemistry at the Massachusetts Institute of Technology, Cambridge, United States.


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