After a team of scientists from the British Antarctic Survey announced a significant disappearance of ozone in the stratosphere above Antarctica, a massive research effort was launched that ultimately linked the ozone hole with increases in atmospheric concentrations of chlorofluorocarbons.
On May 16, 1985, a group of scientists from the British Antarctic Survey led by Joseph Charles Farman published a research paper presenting the results of several years of measurements of stratospheric ozone above Halley Bay in Antarctica. In that paper, the researchers noted that the total amount of ozone in early spring had decreased by almost 50 percent during the previous ten years. This discovery of an “ozone hole” above Antarctica led to a massive research effort that ultimately linked formation of the ozone hole to increases in atmospheric concentrations of chlorofluorocarbons (CFCs).
The first reliable method for measuring ozone in the atmosphere was developed by G. M. B. Dobson, a British physicist, in 1926. The Dobson spectrophotometer
In 1957, as part of the International Geophysical Year
In the late 1950’s, scientists began to consider the possibility of measuring atmospheric ozone using Earth-orbiting satellites. Donald F. Heath, a physicist at the National Aeronautics and Space Administration
In 1975, F. Sherwood Rowland
In the mid-1970’s, a more dramatic decrease in total ozone began to be observed at Halley Bay during the Antarctic spring. By 1981, a 20 percent decrease in total ozone during the spring was measured, far larger than any changes previously seen. Farman at first suspected that the instrument used to make the ozone measurements was malfunctioning. When a new instrument arrived in Halley Bay in October, 1982, however, it gave results in agreement with those previously found.
The members of the British research group were still hesitant to publish their observations. In particular, they were concerned that there had been no report of ozone depletion in the Antarctic from satellite observations. Given that the Nimbus 7 satellite had been carrying out measurements of global ozone concentrations since 1978, it should have detected the decrease in total ozone found by the British team. As no such observation had been announced, the British team members were still worried that their measurements might be in error.
When the team observed even larger decreases in total ozone in 1983 and 1984, Farman decided to publish the results of the measurements made at Halley Bay. By this time, a second observation base, located a thousand miles away on Argentine Island, had also detected a decrease in total ozone during the Antarctic spring, suggesting that the Halley Bay observations were correct.
The research paper on springtime ozone depletion in the Antarctic by Farman and his colleagues appeared in the British journal Nature on May 16, 1985. This represented the first published report on what came to be known as the ozone hole.
The observation of large-scale seasonal disappearance of ozone above Antarctica by Farman and his colleagues came as a shock to the scientific community. Although predictions of ozone depletion as a result of increases in concentrations of CFCs had been common for ten years, no one had predicted the loss of ozone seen by the British researchers at Halley Bay. The discovery of the ozone hole also renewed the interest of the public and environmental groups in the effects of manufactured chemicals on Earth’s atmosphere; such interest had declined following the 1978 ban on the use of CFCs in aerosol products.
One puzzle that was quickly solved was why satellite observations of atmospheric ozone had not previously identified loss of ozone above Antarctica. The Nimbus 7 satellite had in fact found decreases in total ozone above Antarctica similar to those observed above Halley Bay. Donald Heath, Arlin J. Krueger, and the other NASA researchers responsible for analyzing the satellite data had hesitated to report their observations, both because of the possibility that their data might be incorrect and because of previous criticism of the quality of satellite measurements of atmospheric ozone. After reviewing the satellite data, a team of researchers led by NASA scientists Krueger and Richard Stolarski
Once scientists became convinced of the reality of the ozone hole, the debate shifted to trying to explain the origins of its formation. Because the British researchers at Halley Bay had found that the decrease in ozone above Antarctica was accompanied by increases in observed amounts of atmospheric CFCs, theories initially focused on a simple chemical explanation for the ozone hole. The decreases in ozone above Antarctica, however, far exceeded the values of 5 to 10 percent predicted by most computer models of the atmosphere, suggesting that processes not accounted for in the models were needed to explain the observed ozone depletion.
Susan Solomon, a scientist at the National Oceanographic and Atmospheric Administration (NOAA), in collaboration with other scientists, including F. Sherwood Rowland, suggested that chemical reactions occurring on ice crystals formed in the stratosphere above Antarctica during winter resulted in the production of large amounts of ozone-destroying compounds, which in turn led to massive destruction of ozone in the spring. Such chemical reactions had not previously been considered in calculations of ozone destruction. Similar explanations for the observed seasonal loss of ozone were soon expounded by other atmospheric scientists.
Several nonchemical explanations for the ozone hole were also developed. Linwood Callis,
The hole in the ozone layer over Antarctica, as measured in 1987.
To evaluate the competing theories for the formation of the ozone hole, Robert Watson,
To provide additional information on the ozone hole, a second research expedition (NOZE-2) was sent to the Southern Hemisphere in September, 1987. This study included both ground-based observations at McMurdo Station and airborne measurements using a high-altitude aircraft called the ER-2, a civilian version of the U-2 spy plane. The ER-2 made a total of twelve flights over Antarctica, during which several of the key effects predicted by chemical models of the ozone hole were detected. These results, combined with additional ground-based observations at McMurdo Station, confirmed that the observed ozone depletion over Antarctica was a consequence of the release of CFCs in the lower atmosphere.
At the same time atmospheric measurements were providing direct evidence in favor of the chemical explanation for the ozone hole, laboratory experiments were giving additional details on the specific chemical reactions involved. Mario J. Molina, one of the authors of the original theory on ozone destruction by CFCs, identified a new set of chemical reactions involving products formed from the breakdown of CFCs and determined the rates at which these reactions occurred. He found that in the conditions present over Antarctica during early spring, these processes would combine to give the large-scale destruction of ozone that had been observed. When these new reactions were included in computer models of the atmosphere, the results from the models were in agreement with the experimental observations for the rate of ozone depletion.
The ozone hole over Antarctica in 1998, from satellite imagery.
The major industrial manufacturers of CFCs, who had provided some of the financial support for NOZE-1 research, altered their long-standing opposition to restrictions on the use and manufacture of CFCs in the light of the new evidence linking CFCs to ozone destruction. In September, 1986, the Alliance for Responsible CFC Policy,
The discovery of the ozone hole and its link to the release of CFCs in the atmosphere also led to the imposition of new restrictions on the production and use of CFCs and other ozone-destroying compounds. Multinational agreements, such as the 1987 Montreal Protocol
The discovery of the ozone hole above Antarctica dramatically demonstrated that human activities have the potential to alter the environment in unexpected and dangerous ways. The discovery led directly to efforts to prevent future large-scale modification of the global environment, including international agreements aimed at reducing the use of ozone-depleting substances. These efforts resulted in a commensurate stabilization of ozone depletion, leading some scientists to speculate that natural ozone production will replenish the atmosphere by the mid-twenty-first century.
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Bailey, Ronald. Ecoscam: The False Prophets of Ecological Apocalypse. New York: St. Martin’s Press, 1993. Argues that concerns about humankind’s effects on the environment are overstated. Chapter 8 is devoted to discussion of the ozone hole and related issues. -
Cagin, Seth, and Philip Dray. Between Earth and Sky: How CFCs Changed Our World and Endangered the Ozone Layer. New York: Pantheon Books, 1993. Presents a thorough account of the history of CFCs, from their development to the controversy over their effects on stratospheric ozone. Chapters 16-21 discuss the discovery of the ozone hole and subsequent events. Includes excellent bibliography. -
Cogan, Douglas C. Stones in a Glass House: CFCs and Ozone Depletion. Washington, D.C.: Investor Responsibility Research Center, 1988. Excellent source of statistical information on the production and uses of CFCs and the effects of CFCs on stratospheric ozone. Chapter 3 reviews the events that led to the discovery of the ozone hole and examines the results of subsequent scientific studies. -
Fisher, David E. Fire and Ice: The Greenhouse Effect, Ozone Depletion, and Nuclear Winter. New York: Harper & Row, 1990. Focuses on global changes in the atmosphere and provides a brief discussion of events related to the ozone hole. -
Gillespie, Alexander. Climate Change, Ozone Depletion, and Air Pollution: Legal Commentaries Within the Context of Science and Policy. Boston: M. Nijhoff, 2006. Extensive legal analysis of the chemical threat to the ozone layer, synthesizing scientific knowledge on the subject with policy analysis. Includes bibliographic references and index. -
Gribbin, John. The Hole in the Sky. Rev. ed. New York: Bantam Books, 1993. Provides an introduction to the topic of the ozone layer and its problems. Describes the discovery of the Antarctic ozone hole. Includes bibliographic references and index. -
Parson, Edward A. Protecting the Ozone Layer: Science and Strategy. New York: Oxford University Press, 2003. Comprehensive technical discussion of efforts to protect the ozone layer undertaken through international cooperation. Chapter 2 is devoted to a review of early stratospheric science and the emergence of concerns about CFCs. Includes notes, references, and index. -
Roan, Sharon. Ozone Crisis: The Fifteen-Year Evolution of a Sudden Global Emergency. New York: John Wiley & Sons, 1989. Presents a history of the scientific and political events associated with the debate over the effect of CFCs on stratospheric ozone. Chapters 8-16 discuss the discovery and investigation of the ozone hole and the subsequent regulation of ozone-destroying chemicals.
Rowland and Molina Theorize That Freon Causes Ozone Depletion
Clean Air Act Is Revised
Chlorofluorocarbons Are Banned in the United States
United Nations Creates a Panel to Study Climate Change
U.N. Agreement Protects Ozone Layer
U.S. Congress Approves More Clean Air Act Amendments