At a time when there is still debate in the United States among the public and politicians about the link between climate change and the greenhouse gases expelled into the atmosphere by the activities of human beings, the author looks back to an argument from another era about a man-made pollutant and a dangerous atmospheric problem. In many ways, today’s controversy over the causes of climate change and what to do about it are reminiscent of the debate over the link between chlorofluorocarbons (CFCs) and the thinning of the ozone layer over 30 years ago, when the vast majority of scientists who studied the CFC problem were on one side, and industry and lobbyists were on the other. This stalemate was finally resolved only after the discovery of the ozone hole over Antarctica and the irrefutable evidence linking the ozone hole to CFCs. Only then did the major manufacturers of CFCs begin to get on board. In the end, an international agreement was signed to control CFC production, substitutes for the compounds were found and marketed by manufacturers, and the ozone hole stopped growing—and it now shows signs of repairing itself, if slowly. This collaboration has been hailed as a landmark that may have implications for how the current debate in this country will eventually play out. But was that the whole story?

The good news is that the ozone hole over the Antarctic has stopped growing,1 thanks to the world’s first global environmental treaty, the Montreal Protocol on Substances that Deplete the Ozone Layer, and its amendments (United Nations, 1987). The amount of long-lived, human-made chlorofluorocarbons (CFCs) in the atmosphere—the cause of the hole—is decreasing all over the globe, at a rate and in a manner in line with expectations.2 A crisis was averted (Douglass et al., 2014). Yet for about a decade after Mario Molina and Sherwood Rowland published their 1974 journal article describing the chemical link between CFCs and stratospheric ozone, the fate of the Montreal Protocol was far from certain, right up to the moment when the Antarctic ozone hole was reported by Joseph Farman and his colleagues in 1985.

The scientific basis for the link between CFCs and the depletion of ozone in the stratosphere—the layer located between 10 and 50 kilometers above the ground, just above the layer where humans live and weather happens—rested initially on the hypothesis that CFCs were spreading throughout the atmosphere and delivering chlorine to the stratosphere. The reasoning was that while CFCs were stable compounds close to the ground, once they reached the stratosphere they were bombarded by ultraviolet (UV) radiation from the sun, causing them to break apart into free chlorine atoms. These atoms in turn would attack atmospheric ozone and convert it into chlorine monoxide and oxygen. The chlorine monoxide would then attack oxygen atoms that would otherwise have become ozone; thus, the free-floating chlorine was acting as a catalyst—something that promoted reactions without itself being consumed in the process. In this manner, it kept destroying ozone until the free chlorine finally encountered something that would cause it to react to form a harmless chlorine-containing molecule. This meant that before a chlorine atom was bound up in a more inert form, it could cause up to 100,000 molecules of ozone to break down.

In this view of total ozone over Antarctica, the purple and blue colors are where there is the least ozone, and the yellows and reds are where there is more ozone. Before the ozone hole, this view was a red donut around a green center

To make matters worse, the CFCs have a long atmospheric lifetime and are only slowly removed by natural processes. Meanwhile, more CFCs—and hence more chlorine atoms—were continually being pumped in by humankind, because substances containing CFCs were frequently used as the coolant gases in refrigerants and air conditioners, as well as the propellants in aerosols, spray foams, and the products used by the electronics industry to clean computer parts.

Implications Researchers quickly realized that ozone depletion could be a serious problem because ozone is a vital ingredient in the upper atmosphere. Its presence acts as a shield, blocking the majority of harmful UV rays coming from the sun from reaching the ground. In the words of one college textbook, Environmental Science: If the full amount of ultraviolet radiation falling on the stratosphere came through to the Earth’s surface, it is doubtful that any life could survive; plants and animals alike would be simply ‘cooked.’ Even the small amount (less than 1 percent) that does come through is responsible for all the sunburns and the more than 200,000 cases of skin cancer per year in the United States, as well as untold damage to plant crops and other life forms. (Nebel and Wright, 1993: 375) At the higher latitudes in both hemispheres, including the northern United States—where humans and ecosystems have gotten used to a thicker ozone shield—the effects of UV rays could be even more pronounced.3 Testing this CFC hypothesis took time, because new models of chemical mechanisms had to be developed. The reaction chemistry had to be studied systematically in laboratory experiments, and highly sensitive instruments to measure the atmospheric chemicals had to be developed, tested, calibrated, and deployed. Early on, research devoted to testing the hypothesis received significant funding not only from NASA and other government agencies but also from the Chemical Manufacturers Association, and scientific progress was rapid. Almost immediately, interest in Molina and Rowland’s hypothesis spilled beyond the realm of pure science into the public discourse, the boardrooms of CFC manufacturers, and the halls of Congress. A prosaic fact clouded the conversation: For most people, chlorine was an ingredient used in swimming pools, so the idea of chlorine reacting with molecules in the stratosphere to decrease ozone was a stretch for the public imagination. To further complicate the discussion, while ozone is beneficial in the upper atmosphere, excessive amounts of it can be harmful closer to the ground, making breathing more difficult and damaging crops, trees, and other vegetation; ozone is a prime ingredient in urban smog (Environmental Protection Agency, 2003). The idea that the same molecule can be “good” in the high atmosphere and “bad” at ground level is an illustration of the old adage that a pollutant is a chemical in the wrong place. (Fun fact: Ozone is the sharp, pungent smell detected on the beach after a thunderstorm. The word “ozone” even has its origins in the Greek verb that means “to smell.”) If the CFC–ozone depletion hypothesis was correct and the consequences of ozone loss were as dire as projected, then the only ethically defensible action would be the elimination of the manufacturing and distribution of all CFCs—a step that would likely require government mandates, harm the profits of CFC manufacturers, and affect the lives of billions of users. Consequently, there was much opposition, as the first wave of evidence of the impact of CFCs on stratospheric ozone began to come in from atmospheric scientists and chemists. As research continued, the weight of evidence began to shift among scientists toward support for the CFC-initiated stratospheric ozone depletion hypothesis, along with the inevitable conclusion that skin cancer rates and other damage would increase. Some of the scientists who carried out this seminal research decided to become advocates for action to mitigate the likely harm from a depleted ozone layer. These scientist-advocates were subjected to intense criticism. This criticism took several forms. The scientific discourse provided counter-evidence, located flaws, and searched for unresolved issues in the evidence that supported the hypothesis, thus acting as a form of peer review and improving the quality of the science. In the world of business marketing, criticism was designed primarily to protect or expand corporate profits by putting pressure on government representatives to prevent or delay action. But in the field of politics, criticism served ideological and political agendas. The most effective tactics used to prevent action to protect the ozone layer were the same ones that are typically used whenever science meets profits and politics today (Oreskes and Conway, 2010).

Strategy and tactics These tactics have been reported often but are worth repeating here. CFC manufacturers, users, and their government representatives initiated public relations campaigns designed not to illuminate but to obscure, to throw doubt on the hypothesis and the weight of scientific evidence, and to otherwise convince lawmakers and the public that the data were too uncertain to act upon. A few scientists who had not conducted research or published in the field were paid by industry and special-interest groups to uphold a contrarian view. They challenged the findings with disproven hypotheses and debated those scientists who did have expertise in the field of stratospheric chemistry in high-profile forums. When results inevitably began to refute their views, or whenever their own work was proven wrong or rejected for publication, these “contrarian” scientists, government representatives, and industry spokesmen then changed tactics, to denigrate the entire peer-review process. As evidence mounted that CFCs were harmful, the contrarians turned to arguing that acting unilaterally would cause dire economic consequences and loss of competitive advantage for the United States. They claimed that actions to protect the ozone layer would cause immoral harms to citizens of developing nations by denying them access to cheap refrigeration. Any new scientific result that was even slightly contrary to the CFC–ozone depletion hypothesis was trumpeted as implying that the entire body of evidence was flawed. In some cases, the contrarians attacked the competence and integrity of the stratospheric ozone scientists, especially those engaged in any advocacy, claiming that they were motivated by the desire for large research grants and fame, or that they were afraid to come to different conclusions from those of their peers. If all else failed, the contrarians even questioned if the scientist-advocates wanted to bring down the modern way of life. These fights were often carried out in public. A common tactic of contrarian scientists was to bring up seemingly reasonable scientific points and challenge stratospheric ozone scientists to answer them. Certainly these questions needed to be answered, and usually a stratospheric ozone scientist would put together a list of answers and send them to the contrarian scientist who requested them. Let me give a few examples of the most frequently asked questions: “CFCs are heavier than air, so how can they get into the stratosphere?” “How can CFCs, which are thousands of times less abundant than ozone, destroy more than a thousandth of the ozone?” “Doesn’t the chlorine in the stratosphere come from volcanoes and other natural sources?” It often seemed that soon after these questions were answered one-by-one, the contrarian scientists would return to the beginning of the list and ask the same questions all over again. Eventually, the triennial World Meteorological Organization and United Nations Environment Programme Scientific Assessment of Ozone Depletion reports included a special section called “Twenty Questions and Answers about the Ozone Layer” (Earth System Research Laboratory, 2010). Answers were carefully written and vetted by scientists active in the field before being published. (For the record, the short answers are: “Heavy” gases such as CFCs are well mixed throughout the atmosphere and transported to the upper atmosphere by natural air motions such as convection and winds; the chlorine in a CFC acts as a catalyst, causing the breakdown of hundreds of thousands of ozone molecules without being consumed itself, so a single chlorine atom has an impact well above its number; and most of the chlorine in the stratosphere comes from CFCs, less than a fifth comes from natural sources, and only a few percent from volcanoes.4)

Ebb and flow of research Criticism of the link between CFCs and stratospheric ozone loss had mixed success. Those who bothered to carefully examine the evidence usually came away convinced that the weight of evidence favored the hypothesis and its consequences. But as a result of the conflicting information, public and congressional opinions were mixed, shifting toward or away from aggressive regulatory action depending upon the strength of media campaigns, science news, and differing political views. The most aggressive criticism occurred in the first decade after the Molina and Rowland (1974) paper. By 1984, evidence substantiating the hypothesis had been accumulated in models, laboratory experiments, and atmospheric measurements. Some of the strongest evidence rested on measurements of chlorine monoxide in the stratosphere, which was known to come from CFCs and is the main actor in the chlorine catalytic cycle, and on the statistically significant but difficult-to-discern stratospheric ozone depletion trend that was partly masked by day-to-day, episodic, and seasonal variability. Extensive research also probed the links between stratospheric ozone loss and increased ultraviolet (UV) sunlight at Earth’s surface, and between UV exposure and rates of skin cancer—but neither link was established by cause-and-effect observations firmly enough to satisfy the contrarians. This progress in the science—or the lack thereof—was mirrored in the situation with mitigation. The United States, Canada, Norway, and Sweden had banned the use of CFCs in aerosol sprays in 1978, but few other countries had followed their lead. CFC production even began increasing again, as industry found other uses for the gases, in products such as blown foam building insulation. At about the same time, DuPont and other CFC makers began studying alternatives, particularly the more ozone-friendly hydrochlorofluorocarbons (HCFCs), but their interest in alternatives waxed and waned depending on how tough they thought the regulatory actions would be. The efforts by scientist-advocates, nongovernmental organizations, and some government officials to achieve a CFC ban continued to build momentum, eventually leading to the drafting of the Montreal Protocol which was based on the scientific evidence as it existed in 1984. However, a stalemate had occurred, and real progress in both the science and the policy was meandering forward with an uncertain outcome. What was needed was a breakthrough.

A game changer In 1985 came an event so unexpected and dramatic that the link between CFCs and stratospheric ozone loss was irrefutable. Joseph Farman and his colleagues at the British Antarctic Survey published their observations of growing springtime stratospheric ozone losses that had become evident in their data starting in the early 1980s (Farman et al., 1985). The discovery of the Antarctic ozone hole caught even the stratospheric ozone scientists by surprise; among other things, NASA satellites had found a hole in the ozone layer over the Antarctic that was so great that the computers’ algorithms initially flagged the data as errors. (They were programmed to automatically treat any figure that showed a drop of 30 percent or more as bad data possibly caused by an instrument error;5 meanwhile, an area over the Antarctic the size of North America experienced a drop of 50 percent below normal.) This was not the slow, gradual decline that was anticipated, nor was it uniformly spread over the globe as originally anticipated (Nebel and Wright, 1993). With the situation much, much worse than expected, and more concentrated in one geographic region, it was obvious that the original Molina and Rowland hypothesis needed to be refined, at least for nontemperate regions. Their catalytic mechanism operated as predicted throughout most of the stratosphere in the mid-latitudes but could not operate in the weak solar light of the polar spring. In addition, the rapid ozone loss observed in the Antarctic was occurring in the lower stratosphere, not the upper stratosphere as predicted by the models. To explain the amount, timing, and location of the Antarctic ozone hole, some meteorologists—scientists who study atmospheric motions—claimed that it was due to air motions bringing ozone-poor air up from below the stratosphere. Meanwhile, atmospheric chemists studying the polar stratospheric clouds that form in the cold polar vortex—whirlpool-like winds that circle the poles in the lower stratosphere—showed that the abundant inert chlorine from CFCs was reacting on these clouds, producing highly reactive chlorine compounds that could take part in an ozone-destroying catalytic cycle different from the one proposed initially by Molina and Rowland. In a nutshell, these scientists found that the reactions were taking these inert, chlorine-containing chemicals and shifting all of them to reactive forms. With the addition of a little weak UV light, that was all that was needed to destroy a lot of ozone very fast. This was significant, because outside of the polar vortex more than 95 percent of the chlorine is in inert forms, which means that less than 5 percent is reactive. (In addition, stratospheric air at the poles is isolated from other regions during the long winter months, when strong winds encircle the region, restricting the motion of air into or out of the polar stratosphere. This meant that the chlorine had plenty of time to work on ozone molecules in a confined geographic region.) Even while details were being worked out, the Antarctic ozone hole’s discovery caused DuPont to realize that further regulation was likely, and the company convinced other CFC manufacturers and users to support international regulation for a gradual reduction in CFC production (Maxwell and Briscoe, 1997). This shift was announced in September 1986. However, despite the growing political and public pressure, the CFC industry and its government representatives still publicly balked at a CFC ban, arguing that the science did not justify an immediate ban. Meanwhile, measurement campaigns, or scientific projects to measure the amount of ozone loss, were quickly mobilized. The first was a ground-based remote sensing campaign in Antarctica in 1986, followed by an airborne survey using high-altitude NASA ER-2 aircraft in 1987. The rapidity of the response was possible only because government agencies had invested in developing their stratospheric measurement capability, and only a few new instruments were needed for the observations that would answer the key Antarctic ozone hole questions. The 1986 campaign eliminated the dynamical and nonchlorine chemical hypotheses and provided strong evidence for the role of abundant chlorine. The 1987 campaign provided the ultimate smoking gun needed to link CFCs to the Antarctic ozone hole with measurements showing the agent of ozone destruction, chlorine monoxide, increasing dramatically while ozone dropped precipitously as the ER-2 aircraft crossed into the Antarctic stratospheric polar vortex. Since then, a slew of data from more aircraft campaigns, ground-based remote sensors, and satellites have confirmed and tightened the link between CFCs and the Antarctic ozone hole. An even greater body of research demonstrated similar but less dramatic ozone loss in the Arctic springtime polar lower stratosphere and, now, widespread nontropical ozone loss.

The first steps toward mitigation In September 1988, a second event as significant as the Antarctic ozone hole occurred: Richard Heckert (see Miller, 2010), chief executive officer of DuPont—the largest CFC manufacturer—began supporting action to eliminate the manufacture and use of CFCs (Maxwell and Briscoe, 1997). At the same time, he insisted that CFCs should not be banned immediately but be phased out more gradually, as the production of the new HCFCs and the equipment to use them became available. There is much speculation as to why Heckert changed positions, but projections of DuPont’s CFC market share and profits were trending down. Certainly, he would know that his company had already developed and patented the HCFC alternatives, and that these could give DuPont a huge competitive advantage over companies producing the older CFCs, for which DuPont’s patent had expired a few years earlier. At the same time, by supporting regulations, DuPont could have more influence in developing those regulations and promote itself as being environmentally responsible. No matter what DuPont’s motivation, however, the shift signaled an end to the industry’s public relations campaign against the CFC–ozone depletion science, even if it did not stop DuPont’s campaign for a CFC regulation schedule that would optimize profits. Other CFC manufacturers had little recourse but to fall in line. This support by the major CFC manufacturers and users proved to be important for negotiating an international CFC ban. Those who remained opposed to a CFC ban—contrarian scientists, government officials, congressional representatives, and media pundits—howled that DuPont had sold out (Maduro, 1989). Likely, DuPont’s shift had as much to do with the diminished criticism of the science as did the solid evidence supporting the CFC link to the Antarctic ozone hole. This is not to say that all criticism stopped; it didn’t, and it actually continues to this day whenever a new stratospheric ozone finding is reported in the press. However, without corporate sponsorship, the critics dwindled to a few contrarian scientists who haven’t moved on to the issue of climate change, some government representatives, and some prominent media pundits. Much of the public still has concerns about damage to the ozone layer, but the CFC–stratospheric ozone issue is not a priority6 and is considered to be solved by many—even if that may be premature, as merely stabilizing a problem is not the same as fixing it, and there are environmental problems with CFC replacements.7 Nevertheless, models predict that the ozone level will return to 1980 levels sometime between the years 2050 and 2070 (Douglass et al., 2014). The Montreal Protocol was signed in 1987, ratified by the United States and most other nations in 1988, and went into effect in January 1989; it has now been ratified by every nation. Technically, the Montreal Protocol was based on evidence that existed before the link was established between CFCs and the Antarctic ozone hole because the scientific results were either being prepared for publication or undergoing peer review and thus embargoed from public release. However, the word had spread widely regarding the scientific results from the 1986 and 1987 campaigns, and thus ozone hole science was likely a factor in the ratification of the Montreal Protocol. The original terms of the Montreal Protocol called for only a 50-percent reduction in CFC production, which would have been insufficient to reverse the course of devastating stratospheric ozone destruction (Newman et al., 2009). The brilliance of the Montreal Protocol was that it included provisions allowing for revisions based on the evolving scientific knowledge. With mounting evidence of ozone loss in the Arctic polar stratosphere, later amendments to the protocol led to the outright ban on CFCs and put the atmosphere on a track where the stratospheric ozone loss would be reversed and then projected to end several decades into the future. Not long after, abundances of CFCs began to reach their peaks in the troposphere and the stratosphere, and now there is evidence that the Antarctic ozone hole is no longer growing. Despite this success, constant vigilance is needed to ensure that the ozone layer continues to heal, humans do nothing else that might jeopardize this process, and there are no more surprises.

Lessons learned It is often said that the lessons from the CFC–stratospheric ozone loss issue should be applied to the greenhouse gas–climate change problem. This statement is often followed by the comment that climate change is considerably more complicated. The latter comment is true, in a sense. For instance, most CFCs were manufactured by just a few corporations, while greenhouse gases come from many producers of energy. To make matters worse, the greenhouse gas–climate change issue is playing out in a hyper-partisan, highly politicized, and media-saturated world that simply did not exist in the 1970s and 1980s. But while the problem is more complicated and the hysteria—mostly by contrarians—is greater, the solution is the same: getting a relatively few corporate leaders, or leaders of governments controlling their energy sectors, to see greenhouse gas reduction as an opportunity to gain market share and profits, and a way to avoid liability should the climate change too radically and unexpectedly. This comment bears repeating: Greenhouse gas reduction is an opportunity to gain market share and profits, and a way to avoid liability. Today’s greenhouse gas–climate change problem has many parallels to the CFC–stratospheric ozone loss debate of 30 years ago. The vast majority of scientists who study the problem say that the weight of evidence shows that human activities are driving climate change. A few contrarians, businesses, and political and media pundits say otherwise. The majority of the public is confused by the conflicting messages and has low interest. The greenhouse gas producers, their lobbyists, and the governments that control their energy sectors are stalling, saying that the science is too unsettled and more proof is needed that humans are responsible. At the same time, corporations are examining new technologies and trying to find ways to achieve a competitive advantage and profits. The ozone hole case suggests that nothing will likely happen until a dominant energy producer—or a consortium of dominant energy producers—develops profitable proprietary alternatives to fossil fuels and other greenhouse gas–emitting processes. Then, they will change positions to support regulations to drastically reduce greenhouse gas emissions, with the purpose of giving themselves a competitive advantage and significant profits. Public awareness and energy conservation are important, and the public’s and government representatives’ opinions can put pressure on corporate profits. But it really doesn’t matter what the public or government representatives want or believe; short-term and long-term corporate profits will drive any decision to greatly limit greenhouse gas emissions. It is possible that an unknown climate tipping point looms on the horizon, one that is vastly more devastating and longer-lasting than any other human-made environmental disaster. Let’s hope that enough individuals at the helms of greenhouse gas-producing corporations and energy sector-controlling governments aggressively pursue ways to achieve competitive advantages and then change their positions on greenhouse gas emissions, before climate change causes its equivalent of the Antarctic ozone hole.

Acknowledgements This article was improved by the comments and edits of Professor Darin Toohey of the University of Colorado at Boulder, USA (http://www.colorado.edu/envs/people/darin-toohey), who has worked for decades in stratospheric ozone research.

Editor’s note The tactics regarding CFCs and the hole in the ozone layer parallel today’s situation regarding research into increasing levels of carbon in the atmosphere and the greenhouse effect. Please see the companion article by Michael Mann in this issue.

Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Notes 1

For more details, see http://ozonewatch.gsfc.nasa.gov. 2

The different sampling programs that were used, and the figures that they came up with, can be found at http://www.esrl.noaa.gov/gmd/hats/combined/CFC12.html. 3

This is also true of the high latitudes of the southern hemisphere. In fact, in southern Australia—whose next landfall is Antarctica—there are constant public service messages to beachgoers to cover up and smear themselves with sunblock. Sun protection and melanoma are taken very seriously in a land where many inhabitants emigrated from places with the fair skin of high European latitudes; visitors are often surprised to see that the standard grade-school uniform down under includes a hat with a long cloth (aka a “havelock”) that covers the back of the neck, making a group of children on their way to elementary school look like a troop of small French Foreign Legionnaires. 4

For more detail, see the most recent edition of “Twenty Questions and Answers about the Ozone Layer,” available at: http://www.esrl.noaa.gov/csd/assessments/ozone/2010/twentyquestions. 5

See http://ase.tufts.edu/cosmos/view_chapter.asp?id=20&page=2. 6

A Gallup poll looked at how Americans rank a variety of environmental concerns, including water pollution, toxic waste, air pollution, acid rain, and damage to the Earth’s ozone layer, among others. Worries about water pollution topped the list, followed by air pollution; damage to the ozone layer ranked third, and acid rain ranked tenth. More details are available at: http://www.gallup.com/poll/22492/Water-Pollution-Tops-Americans-Environmental-Concerns.aspx. 7

Among other things, some substitutes for CFCs are potent greenhouse gases; see http://www.sciencedaily.com/releases/2012/02/120224110737.htm.