Montreal Protocol in transition


caption Image depicting the amount of ozone. The blue and purple colors are where there is the least ozone, and the greens, yellows, and reds are where there is more ozone. (Source: Ozone Watch, NASA)

Even as the negotiators were hammering out the final com­promises in Montreal in September 1987, an unprecedented international scien­tific expedition was under way in Antarctica. Using specially designed equipment placed in balloons, satellites, a DC-8 fly­ing laboratory, and a converted high-altitude U-2 spy aircraft, scientists were tracking stratospheric chemical reactions and measuring minute concentrations of gases. Preliminary results, announced about two weeks after the protocol's sign­ing, indicated high stratospheric chlorine presence and the worst-ever seasonal drop in Antarctic ozone.

Six months later, in March 1988, a joint NASA-NOAA press conference released the Ozone Trends Panel Report, a comprehensive international scientific assessment of all previ­ous air- and ground-based stratospheric trace gas measure­ments, including those from the 1987 Antarctic expedition. The conclusions were stunning: no longer a theory, ozone layer depletion had at last been substantiated by hard evi­dence. The analysis established that between 1969 and 1986, stratospheric ozone over heavily populated regions of the northern hemisphere, including North America, Europe, and the Soviet Union, China, and Japan, had diminished by small but significant amounts. And CFCs and halons were now im­plicated beyond dispute – including responsibility for the ozone collapse over Antarctica.

The new scientific findings were profoundly disquieting. The most alarming implication was that the models on which the Montreal Protocol was based had proven incapable of predicting either the chlorine-induced Antarctic phenomenon or the extent of ozone depletion elsewhere. Most probably, therefore, they were underestimating future ozone losses.

Scientific studies now indicated that if existing atmospheric concentrations of chlorine and bromine were merely stabil­ized, the Antarctic ozone loss would be permanent. In order for ozone levels over Antarctica gradually to recover, and to avoid possibly crossing similar unforeseen thresholds in the future, it would be necessary to restore atmospheric chlorine concentrations (then at three parts per billion and rising) to levels at least as low as those prevailing in the early 1970s, namely, two parts per billion.

The original CFCs and halons would be phased out more rapidly than any of the negotiators at Montreal could have dreamed possible.

Although the work of protecting the ozone layer is still not completely finished, the major challenges have been successfully addressed. The industrialized countries have either phased out, or are in process of phasing out, all of the major ozone-depleting substances as well as the less-damaging transitional chemicals. Developing countries have also accepted phase-out schedules as a great wave of new technologies is being diffused around the world.

Now, the ozone layer is slowly beginning to recover.

Lessons for Science

caption The concentration of ozone varies with altitude. Peak concentrations, an average of 8 molecules of ozone per million molecules in the atmosphere, occur between an altitude of 30 and 35 kilometers. (Source: Ozone Watch, NASA)

Without modern science and technology, the world would have remained unaware of an ozone problem until it was too late. Science became the driv­ing force behind ozone policy, but it was not sufficient for scientists merely to publish their findings. In order for the theories to be taken seriously and lead to concrete policies, scientists had to interact closely with government policy makers and diplomatic negotiators. This meant that they had to leave the familiar atmosphere of their laboratories and assume an unaccustomed shared responsibility for the policy implications of their research. The history of the Montreal Protocol is filled with instances of scientific panels being called upon to analyze and make informed judgments about the effectiveness and consequences of alternative remedial strategies and policy measures.

International scientific consensus was also essential. In effect, a com­munity of scientists from many nations, dedicated to scientific objectivity, experienced through their research a mutual concern for protecting the planet’s ozone layer that transcended divergent national allegiances. The development of an accepted common body of data and analysis was the prerequisite for a political solution among negotiating governments whose initial positions seemed irreconcilable.

In 1984, a remarkable international collaborative research effort was launched by the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA), in cooperation with the WMO, UNEP, the Federal Aviation Administration, the German Ministry for Research and Technology, and the Commission of the European Communities. Approximately 150 scientists of various nationalities worked under U.S. more than a year. The resulting study, Atmospheric Ozone 1985, was the most ambitious analysis of the stratosphere ever undertaken: three volumes containing nearly 1,100 pages of text and eighty-six pages of references. This was followed by even more extensive international studies.

The Montreal Protocol later institutionalized this concept by establishing independent international expert panels to periodically assess scientific, technological, economic, and environmental developments and thereby guide the negotiators in the implementation and revision of the treaty. Over the years, thousands of scientific and industry experts from dozens of countries participated in the effort to learn more about both the dangers and the possible technological solutions. This proved to be a central element in the protocol’s success, facilitating agreement by negotiators on additional controls to protect the ozone layer. In effect, the protocol was deliberately designed to be a dynamic process of narrowing the ranges of uncertainties through continuing focused research, and adjusting the treaty provisions accordingly, rather than being a static one-time solution.

A major lesson from the ozone history is that Nature does not always provide policy makers with convenient early-warning signals of disaster, as exemplified in the case of the Antarctic “ozone hole.” In 1985, British scientists published findings based on balloon measurements of ozone made at Halley Bay in Antarctica. It appeared that stratospheric ozone concentrations during the Antarctic early spring (September-October) were about 40 percent lower than during the 1960s. While the ozone layer recovered toward the end of each spring, the extent of the seasonal ozone collapse, or "ozone hole" (i.e., a por­tion of the stratosphere in which greatly diminished ozone lev­els were measured), had apparently accelerated beginning in 1979.

Total chlorine concentrations had been slowly increasing for decades from its natural level of 0.6 parts per billion,. However, no effect on the ozone layer was evident until the concentration exceeded two parts per billion, which triggered the totally unexpected collapse over Antarctica. In other words, chlorine concentrations had tripled with no impact whatsoever on ozone until they crossed an unanticipated threshold. This nonlinear response has obvious implications for the potential dangers of other types of anthropogenic interference with the planet’s natural cycles and resources.

The British group had actually initially hesitated to publish their findings because they were considered too fantastic. Ironically, it was later discovered that U.S. and Japanese space satellites had not signaled the ozone collapse because, in order not to deluge scientists with unmanageable masses of data, satellite computers were programmed to automatically reject as anomalies any mea­surements so far below the “error” range of existing predictive models!

The role of scientists in the ozone history also provided some useful lessons for the climate change issue. During the 1980s, scientific assessments on climate change appeared regularly, under the aegis of WMO and UNEP, from a small group of largely self-selected scientists called the Advisory Group on Greenhouse Gases. In the summer of 1987, while preparing for the conclusive final negotiation in Montreal, I recommended that the U.S. propose establishing a formalized international assessment body on climate change, similar to what we were doing on the ozone issue. My belief was that findings would be more credible coming from a larger and more diverse group of scientists operating under intergovernmental auspices.

This idea attracted unexpected allies and opponents. Some traditionally anti-environmental officials within the Reagan administration endorsed the concept, anticipating that it would provide governments with more control over the science. In contrast, environmental groups feared that the process would become distorted by politics. My own feeling, grounded in the ozone experience, was that the great majority of scientists were unlikely to allow themselves to be influenced by political, ideological or commercial interests, and that governments for their part would have greater respect for the results of a comprehensive international process of investigation and peer review. The subsequent experience of the Intergovernmental Panel on Climate Change, founded in 1988, has largely confirmed this hope.

Lessons for the Private Sector

The history of the Montreal Protocol also underscored the importance of having sufficient funding for all levels of science, from curiosity-driven basic research to applied engineering solutions. Initially, most research funding came from government sources, in particular NASA and NOAA in connection with their space-related research.

But this was not always the case. In 1985, when the U.K. Government was still strongly opposed to meaningful controls over CFCs, it ceased financing, for obvious political motives, the British scientific mission in Antarctica that had uncovered the “ozone hole.” Significantly, the financial gap was filled by the U.S. Chemical Manufacturers Association; the American chemical companies hoped that controls would not be necessary, but they wanted to resolve the uncertainties – one way or the other.

In general, American industry throughout the ozone negotiations was more pragmatic than ideological. Recognizing the growing scientific consensus, the Alliance for Responsible CFC Policy, a coalition of about 500 producer and user companies, an­nounced its acceptance of international controls in September 1986, three months before the formal negotiation process actually opened. Eight months later, American industry stayed conspicuously aloof from the campaign by anti-environmental elements within the administration to undermine a meaningful treaty, and subsequently fully endorsed President Reagan’s strong position for the climactic September 1987 negotiation in Montreal.

The financial and intellectual resources of the private sector make its involvement and cooperation indispensable, since society ultimately depends primarily on industry to provide technological solutions. Technology is dynamic, and not, as often implied by those who resist change, a static element. If the market is left completely on its own, it may not necessarily bring forth the right technologies at the right time. Although the 1987 ozone proto­col established targets that were initially beyond the reach of best-available technologies, the goals were in fact not unrealistic.

The Montreal Protocol was not, as some opponents charged, a “radical” treaty. On the contrary, it was an expression of faith in the market system. The treaty employed realistic market incentives to encourage technological innovation. The negotiators effectively signaled to the marketplace that research into solutions would now be profitable. Competitive – and collaborative – forces then took over, and solutions were developed much sooner and at considerably lower cost than had earlier been predicted.

The protocol in fact stimulated a virtual technological revolution in the international chemical, telecommunications, pharmaceutical, and numerous other industries. By providing CFC producers and users with the certainty that the CFC market was destined to decline, the treaty unleashed the creative energies and financial resources of the private sector to find alternatives. Following the protocol’s signing, the chemical industry began the race for substitutes. Four months after Montreal, several hundred industry representatives participated in a CFC-substitutes trade fair in Washington.

Some user industries did not wait for the chemical companies to come up with substitutes; such companies as Nortel, IBM and Motorola re-examined their manufacturing processes and found ways to eliminate CFCs. In cooperation with a small Florida company, AT&T announced a new replacement for cleaning electronic circuit boards that was derived from citrus fruit,. Japanese and American importers of electronics parts from Thailand, including AT&T, Ford, Honda, and Toshiba, teamed up with EPA and Japan’s Ministry of Trade and Industry to provide non-CFC technologies to their suppliers. More than 40 multinational companies from eight countries, including Asea Brown Boveri, British Petroleum, Hitachi, and Honeywell, joined to help Viet Nam phase out CFCs.

Lessons for Credibility

Another lesson from the Montreal Protocol’s success was the importance of education: interpreting the continuously evolving and sometimes confusing data and communicating it intelligibly to the public, the media, and political and legislative leaders. This information flow mobilized public support for addressing the potential dangers of a diminishing ozone layer, and thereby promoted political consensus for both funding research and for policy actions. The role of the U.S. Congress was particularly critical in organizing many public hearings on the ozone issue over the years, and in commissioning several important studies by the National Academy of Sciences.

In the 1980s, environmental organizations that favored strong actions to protect the ozone layer generally avoided invoking apocalypse in order to capture media and public attention. As chief U.S. negotiator pressing the official American position for strong controls against the opposition of most of the other major producing and consuming countries, I insisted that our delegation in principle never exaggerate the scientific case: let the science speak for itself, even when it is not completely unambiguous. I wanted to preserve our integrity and not present the opposition with a gratuitous weapon against our position.

When some opponents of controlling CFCs within the U.S. administration tried late in the negotiations to reverse the strong American position (and, incidentally, to dismiss me as chief negotiator), they belittled the science and the dangers, claiming inter alia that the problem could be solved by wearing cowboy hats and sunglasses. The resultant ridicule and backlash from the Congress, scientists, media, public, and the White House itself eventually led to a personal decision by President Reagan reaffirming the U.S. position for strong controls.

Unfortunately, the lesson of scientific integrity appears to have been lost in the debate over climate change that began in the late 1980s. Some environmental groups became overly alarmist in exaggerating the case for global warming following the hot summer of 1988, and, later, by crusading for the Kyoto Protocol as the only conceivable solution. This only engendered a strong counter-reaction from some affected industrial sectors. In addition, when the predicted dire consequences of climate change did not emerge soon, the American public – which in any case is accustomed to natural seasonal weather extremes – became generally apathetic toward possible long-term dangers.

For their part, skeptics of climate change were also not immune to distortion. In an effort to discredit the climate science, opponents repeatedly cite the “Heidelberg Appeal,” released by a nongovernmental group at the United Nations Earth Summit in Johannesburg in 2002, as definitive evidence that most of the scientific community – more than 4000 eminent international scientist signatories, including over 70 Nobel Laureates – rejects the idea that rising anthropogenic carbon dioxide emissions could cause dangerous global climatic consequences. In actuality, the one-page document is a general treatise on the importance of science and contains not a single reference to the climate problem.

Lessons for Government

Some governments allowed commercial self-in­terest to influence their interpretations of the science: uncertainty was used as an excuse for delaying decisions. Some political leaders, particularly those in Europe with substantial chemical industries, were initially prepared to accept speculative long-term environmental risks rather than to impose the tangible near-term costs entailed in limiting products seen as important contributors to a modern standard of living. Short-range politi­cal and economic concerns were, therefore, formidable obstacles to cooperative international action based upon the theory of ozone-depletion.

Other political leaders, however, including President Reagan and the governments of Australia, Austria, Canada, Finland, Denmark, New Zealand, Norway, Sweden and Switzerland, decided to act even while there were still scientific ambiguities, based on a balancing of the risks and costs of delay.

As early as 1977, the U.S. Congress had authorized the Administrator of the Environmental Protection Agency (EPA) in the Clean Air Act to regulate "any substance … which in his judgment may rea­sonably be anticipated to affect the stratosphere, especially ozone in the stratosphere, if such effect may reasonably be anticipated to endanger public health or welfare" (emphasis added). This law attempted to balance the scientific uncertainties with the risks of inaction. And it opted for a low threshold to justify intervention: the government was not obli­gated to prove conclusively that a suspected substance could modify the stratosphere or endanger health and environment. All that was required was a standard of reasonable expecta­tion. As Governor Russell Peterson, a senior advisor to President Nixon, had declared in reference to other potentially harmful chemicals, CFCs, unlike U.S. citizens, would not be considered innocent until proven guilty.

Unfortunately, current tools of economic analysis are not fully adequate for evaluating the costs and risks, and can be deceptive indicators; they are in urgent need of reform. The customary methods of measuring national income do not satisfactorily reflect societal and eco­logical costs – especially those far in the future. Politicians should nevertheless resist the tendency to assign excessive credibility to self-serving economic interests who demand scientific certainty, and who insist that, simply because dangers are remote, they are therefore inconsequential.

By the time the evidence on such issues as ozone layer depletion and climate change is beyond dispute, the damage could be irreversible and it may be too late to avoid serious harm to human life and draconian future costs to society. The signatories at Montreal risked imposing substantial short-run economic dislocations even though the evidence was incomplete. The prudence of their decision was vindicated when the scientific models turned out to have actually underestimated prospective ozone depletion. And, thanks to the ingenuity of private entrepreneurs, the costs of action turned out to be much lower than originally predicted.

Conclusion: Acting Under Uncertainty

The Montreal Protocol was by no means inevitable. Knowl­edgeable observers had long believed it would be impossible to achieve. The ozone negotiators confronted formidable po­litical, economic, and psychological obstacles. The dangers of ozone depletion could touch every nation and all life on earth over periods far beyond politicians' normal time horizons. But although the potential consequences were grave, they could neither be measured nor predicted with certitude when the diplomats began their work.

In the realm of international relations there will always be resistance to change, and there will always be uncertainties. Faced with global environmental threats, governments may need to act while some major questions remain un­resolved. In achieving the Montreal accord, consensus was forged and decisions were made on a balancing of probabilities – and the risks of waiting for more complete evidence were finally deemed to be too great.

“Politics,” stated Lord Kennet during ozone debates in the House of Lords, “is the art of taking good decisions on insufficient evidence.” The success of the Montreal Protocol stands as a beacon of how science can help decision makers to overcome conflicting political and economic interests and reach solutions. The ozone history demonstrates that even in the real world of ambiguity and imperfect knowledge, the international community, with the assistance of science, is capable of undertaking difficult and far-reaching actions for the common good.

Further Reading

  • Andersen, Steven, and K.M. Sarma. 2002. Protecting the Ozone Layer: The United Nations History. Sterling, VA and London: Earthscan. ISBN: 1853839051
  • Barrett, Scott. 2003. Environment and Statecraft – The Strategy of Environmental Treaty-Making. Oxford and New York: Oxford University Press. ISBN: 0199257337
  • Benedick, Richard E. 2001. “Contrasting Approaches: The Ozone Layer, Climate Change, and Resolving the Kyoto Dilemma.” In Global Biogeochemical Cycles in the Climate System, ed. E-D Schulze, et al.,San Diego, London, Tokyo: Academic Press (Harcourt Brace). Max Planck Institute for Biogeochemistry. ISBN: 0126312605
  • Benedick, Richard E. 2001. “Striking a New Deal on Climate Change.” National Academy of Sciences, Issues in Science and Technology, Fall 2001. (See also comments in “Forum,” Winter 2001.)
  • Benedick, Richard E. 1998. Ozone Diplomacy – New Directions in Safeguarding the Planet. Enlarged edition. Cambridge, MA and London: Harvard University Press. ISBN: 0674650034
  • Brack, Duncan. 1996. International Trade and the Montreal Protocol. London: Royal Institute of International Affairs. ISBN: 1853833452
  • Cook, Elizabeth, ed. 1996. Ozone Protection in the United States. Washington, DC: World Resources Institute. ISBN: 1569730881
  • Farman, James, B.G. Gardiner, and J.D. Shanklin. 1985. “Large Losses of Total Ozone in Antarctica Reveal Seasonal Clx/NOx Interaction.” Nature, no. 315.
  • French, Hilary. 1997. “Learning from the Ozone Experience.” In Worldwatch Institute, State of the World 1997. New York: W.W. Norton. ISBN: 039331569X
  • Heidelberg Appeal
  • Lang, Winfried, ed. 1996. The Ozone Treaties and Their Influence on the Building of International Environmental Regimes. Vienna: Oesterreichische aussenpolitische Dokumentation.
  • Le Prestre, Philippe, et al., eds. 1998. Protecting the Ozone Layer: Lessons, Models, and Prospects. Boston, Dordrecht, London: Kluwer Academic Publishers. ISBN: 0792382455
  • Molina, Mario, and F.Sherwood Rowland. 1974. “Stratospheric Chlorine: A Possible Sink for Ozone.“ Nature, no.249.
  • National Oceanic and Atmospheric Administration, NASA, UNEP, and WMO. 1995. Scientific Assessment of Ozone Depletion: 1994. Geneva: WMO. ISBN: 928071449X
  • Parson, Edward. 1993. “Protecting the Ozone Layer.“ In Institutions for the Earth: Sources of Effective International Environmental Protection, ed. P.M. Haas, et al. Cambridge, MA: MIT Press. ISBN: 0262581191
  • Solarski, Richard, and Ralph Cicerone. 1974. “Stratospheric Chlorine: A Possible Sink for Ozone.“ Canadian Journal of Chemistry, no. 52.
  • U.K. House of Lords, Hansard 500 (October 20, 1988): col. 1308.
  • Watson, R.T., F.S. Rowland, and J. Gille, “Ozone Trends Panel Executive Summary,” NASA, Washington, D.C.


Benedick, R. (2007). Montreal Protocol in transition. Retrieved from


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