The Montreal Protocol was achieved twenty years ago. This was the first major international agreement on an envi­ronmental issue of global concern. According to the agreement, major industrial nations agreed to phase out the manufacture of chlorofluorocarbons, chemicals used in cooling systems (re­frigerators) and other important industrial applications.

As time has passed however, this environmental success story seems to have turned to ashes. Questions abound. Was such drastic action justified at the time? Armed with more re­cent information, would we pursue a similar course today? Was anything really achieved? The story of research on atmos­pheric ozone is certainly a cautionary tale of how not to react to perceived environmental crises.

It was in 1974 that chemists Mario Molina and Sherwood Rowland of the University of California, first proposed the the­ory that chlorofluorocarbons (CFCs) would break down in the upper atmosphere (stratosphere) thereby releasing chlorine atoms which could break down ozone gas into ordinary oxy­gen. TIME magazine, in an article May 17, 1993, conceded that scientists had to confirm that CFCs did in fact attack ozone. Nevertheless, declared the TIME article, governments should have acted a lot faster than they did. The article asks rhetori­cally:

Did the world really act as fast as possible to meet the threat? The answer, unfortunately, is no. The eventual rescue operation was the last chapter in a long saga of confusion, wishful thinking, indecision and delay

Alternatively, some people at the time insisted that world­wide action was premature. In retrospect, it now appears that the latter group of naysayers was correct. The scientific com­munity really had little in the way of data. Nevertheless there were plenty of dire warnings about what might happen.

The sky is falling ... apart!⤒🔗

It was the discovery in 1985 of a large area of much lower ozone levels in the sky over Antarctica which really caught the world's attention. Such an "ozone hole" in the Antarctic sky has since appeared each spring and ozone levels soon bounce up­ward again, but scientists worry that a significant amount of ozone is being lost every year in the sky over this southern, very cold continent. More recently, an ozone hole over the Arctic was also found during very cold springs in the northern hemisphere.

A United Nations conference in Vienna in 1985 was con­vened to search for an international response to the ozone problem. The reason for concern about ozone levels is that this gas filters out harmful ultraviolet radiation which comes from the sun. Ultraviolet radiation has the ability to break down genetic information (DNA) in cells, and cause cancer and cataracts.

The Vienna conference failed to achieve a consensus. But the Montreal conference, which met two years later, approved the freezing of CFC production worldwide, initially at 1986 lev­els with a subsequent phased reduction over ten years. Thus the Montreal Protocol was achieved in 1987 and ratified two years later in 1989.

New findings←⤒🔗

A retrospective article, written in the June 11, 1993 issue of the journal Science, admitted that there were no actual docu­mented negative effects from reduced ozone levels. There had, in fact, been no increase in dangerous UV light discovered in the USA. On the contrary, the data, if anything, suggested a slight decrease in UV light. The concern was over what might happen in the future. Thus the Science writer declared:

The gap between the present danger of ozone depletion — little or none that can be attributed to rising ultraviolet radiation at the Earth's surface — and the possible danger in the future, had not the Montreal Protocol been passed, provided plenty of room for a wide range of opinions as to how much concern is warranted.

The 1993 Science article also mentioned that the current scientific understanding of global ozone behaviour was "fraught with uncertainty." That admission certainly came to mind when a news item about ozone chemistry appeared in the journal Na­ture September 27, 2007. It was impossible to miss the title: "Chemists poke hole in ozone theory" The opening paragraph declared that new experimental results "threaten to shatter es­tablished theories of ozone chemistry" and if the data are con­firmed, "scientists will have to rethink their understanding of how ozone holes are formed."

According to the 1974 theory of Molina and Rowland, sunlight in the highest levels of earth's atmosphere (upper stratosphere) breaks down CFCs and releases very reactive atoms (or radicals) of chlorine gas (one half a chlorine gas molecule). Unlike most molecules in the air close to sea level, CFCs arrive intact in the stratosphere because they are so resis­tant to chemical change. However even these molecules suc­cumb to the effects of strong sunlight in the outer atmosphere. The reactive chlorine then steals an atom of oxygen from ozone. This leaves oxygen gas (O₂) instead of ozone (O₃). The chlorine oxygen combination then combines with another such combination to form dichlorine peroxide (Cl₂O₂). The sun then causes that molecule to break down too, releasing more re­active chlorine which can again attack more ozone.

That was the theory. What chemists have more recently done, is to measure how fast that reaction proceeds under con­ditions which are realistic for the upper atmosphere. Guess what! The measurements indicate that the reaction proceeds al­most ten times more slowly than had been expected. The im­plications for the result were only evident when a scientist from the Alfred Wegener Institute of Polar and Marine Research in Potsdam, Germany inserted the new reaction rate into com­puter models for ozone depletion.

It would be an understatement to say that the result was a shock. It now appears that 60% of the ozone destruction at the poles comes from an unknown mechanism! Markus Rex, the atmospheric scientist involved, thus declared:

"If the measure­ments are correct we can basically no longer say we under­stand how ozone holes come into being."

Nature Sept. 27/07 p. 382

It seems ironic that the institute that Markus Rex repre­sents, is named for Alfred Wegener, whom North American scientists vilified for forty years over his theories about conti­nental drift. European scientists do seem to be more free to question current science dogma than are North American sci­entists. Nevertheless Markus Rex did declare his support for the Montreal Protocol and current views that CFCs are the main culprit in the ozone problem.

In view of the recent chemical studies, it makes sense that the Montreal Protocol does not seem to have led, at least yet, to any improvement in ozone levels in the outer atmos­phere. An article (the cover story) published in Nature May 4, 2006, was entitled "The search for signs of recovery of the ozone layer." The article declares that there are a lot of factors which can influence ozone levels in the upper atmosphere. Thus we need long term data to see any trends. Indeed the authors Elizabeth Weatherhead and Signe Andersen declare:

The analyses of ozone records and conclusions regarding re­covery, in the short or long term, are sensitive to many con­current changes in the atmosphere. Because of high natural variability in ozone levels, total column ozone fluctuates over timescales of a few years. These fluctuations can obscure long-term changes and offer false indications of recovery. The separation of long term change in ozone concentrations from natural variability is our current challenge.

The authors compared annual ozone averages at four lati­tudes from 1980 to 2005. What they found was "considerable variability that cannot be attributed to concentrations of ozone-depleting substances." The authors found that storms on the sun, which follow an eleven-year cycle, and volcanic eruptions, both had an influence on ozone levels. In the early years of the controversy, many scientists denied that these processes had any significant effect on ozone levels. At the end of their arti­cle, the two authors conclude:

Considerably longer data series and improved understanding of atmospheric processes and their effects on ozone are needed to estimate future ozone lev­els with confidence.

Lesson to be learned←⤒🔗

Before the Montreal Protocol was ratified, many concerned citizens and some scientists declared that the rush into world­wide action was premature. Long-term studies would have been the prudent response in order to ensure that the CFCs were really to blame. After all, if there really was a problem that should be addressed, the smart procedure would be to correctly identify what the problem is. However, as a result of the Mon­treal Protocol, some compounds which were important for re­frigeration, aerosols and fire retardants among other uses, have been replaced by less efficient, more expensive compounds.

In the case of the ozone story, society will manage with the new situation. However a similar controversy involving carbon dioxide emissions, promises to have a much greater im­pact on all our lives. If there are any lessons to be learned from the ozone story, it is to proceed slowly. Collect information on natural variation and long-term changes. Listen to the critics as well as the prominent "experts." Thus the title of this article comes from a seventeenth century proverb: "Marry in haste, re­pent at leisure." Our modern version translates into "Mandate (a protocol) in haste, repent at leisure." This is an important concept that should never be forgotten.