“Of all the multitude of threats facing the global environment, none are greater than the changes taking place in the very atmosphere of the planet. In recent years, painstaking scientific work has demonstrated that man-made chemicals are destroying the ozone layer which shields all life from the lethal ultraviolet rays of the sun. Scientists are also now agreed that pollution is warming the world’s climate, threatening to bring about changes unparalleled in the history of human civilisation, raising sea levels and devastating food production worldwide. In 1988 the World Conference on the Changing Atmosphere reported that these dangers rank second only to nuclear war.”

Foreword by Dr Mostafa Tolba, Executive Director, UNEP (1975 – 1992) in Action on Ozone, UNEP, 1989.

An accident revolutionises cooling
For over half a century, the chemicals that were doing most of the damage to the ozone layer were regarded as miracle substances, uniquely useful to both industry and consumers and harmless to human beings and the environment alike. Inert and immensely stable, neither flammable nor poisonous, easy to store and cheap to produce, these chlorofluorocarbons (CFCs) seemed designed for the modern world. They do no damage whatsoever to land, sea or the air we breathe, they neither react with other substances in the biosphere nor dissolve to pollute the rain.

Not surprisingly, they became more and more widespread. Invented by accident in 1928, they were first developed as the working fluid for refrigerators. From 1950, they were used as propellants in aerosol cans, providing the power behind a wide range of sprays. The computer revolution proved their usefulness as solvents because they cleaned delicate circuitry without damaging its plastic mountings, and the fast-food revolution enlisted them to blow foam for polystyrene cups and food cartons. At the time about 30 per cent of world CFC production was used in fridges, freezers and air conditioners, about 25 per cent in spray cans, another 25 per cent in blowing foams for various uses from buildings and cars to fast food containers, and the remaining 20 per cent for cleaning and other purposes.

From miracle to environmental catastrophe....
But the high stability of CFCs, making them so useful on earth, enables them to attack the ozone layer. Unchanged, they slowly drift up to the stratosphere, where intense solar ultraviolet radiation servers their chemical bonds, releasing chlorine which strips an atom from the ozone molecule, turning it into oxygen. The chlorine acts as a catalyst, accomplishing this destruction without itself undergoing any permanent change, so it can go on to repeat the process. In this way, every CFC molecule destroys thousands of molecules of ozone, and we were blissfully unaware of the damage we were wreaking.

But in the autumn of 1973 two scientists, Rowland Sherwood and Mario Molina, began investigating the role of CFCs. Realising that all the long-lived CFCs ever released remained in the atmosphere, they decided to discover what happened to them. They soon worked out that the gases would drift unchanged up to the atmosphere and have a catastrophic effect on ozone – so great in fact, that at first, they didn’t believe their own calculations. At the time, their hypothesis, published in 1974, was controversial and for years afterwards it was debated by scientists and challenged by industry. However, they remained steadfast and convinced of their findings.

In the meantime, the United Nations Environment Programme (UNEP) started laying the foundation for international action. In April 1975, the third meeting of its Governing Council backed a programme proposed by the Executive Director, Dr Mostafa Tolba, on risks to the ozone layer and in 1976 the “World Plan of Action on the Ozone Layer” the first international agreement on the issue, was adopted. The plan of action included research into the monitoring of ozone and solar radiation, the assessment of the effect of ozone depletion in human health, ecosystems and the climate, and the development of ways of assessing the costs and benefits of control measures. Adopting the Action Plan was a clear signal and acceptance by the delegates that there was a potential problem, though the extent had yet to be determined.

But progress was slow. UNEP’s coordinating committee in charge of implementing the Action Plan continued to meet regularly and issuing reports throughput the 1970s. It was a difficult time, not least because the means of assessing the effects of CFCs on the ozone layer were still in their infancy. As new research came in, estimates of the likely depletion fluctuated widely from year to year, and the uncertainty was used by some to cast doubt on the while hypothesis of Rowland and Molina. But they and other scientists at the heart of the assessment process remained resolute, standing by their findings and convinced that a global environmental issue was unfolding.

......to global cooperation
The Convention for the Protection of the Ozone Layer, adopted in Vienna in 1985, had nations agree to take “appropriate measures…to protect human health and the environment against adverse effects resulting or likely to result from human activities which modify or are likely to modify the ozone layer.” Twenty nations signed it at the time; most did not rush to ratify it. However, it did set an important precedent: for the first time nations agreed, in principle, to tackle a global environmental problem before its effects were felt, or more importantly perhaps, before it was scientifically proven.

To this day, scientific work to protect the ozone layer continues under the Vienna Convention. Supported by the Convention’s Trust Fund and Ozone Research Managers, scientists around the world monitor the atmosphere to check on levels of ODSs as well as other substances such as hydrofluorocarbons (HFCs) that replaced CFCs. While HFCs are not ozone-depleting, they are potent greenhouse gases affecting our climate.

This continued observation of our atmosphere is crucial to protecting our environment, ensuring countries adhere to their commitments and that any unusual emissions are detected and addressed early.

Excerpt from Action on Ozone, UNEP, 1989.