Introduction to Climate Change
7. Ozone Depletion
As of August 2000, the Montreal Protocol had been ratified by 175 countries, including virtually all industrialized countries and most developing countries. While the Protocol and its amendments have not eliminated the dangers of ozone depletion, they have established national commitments that will lessen the threat in years to come. The most important precedent in international law for the management of global environmental harms, the Montreal Protocol provides a useful model for other long term environmental challenges such as global warming. The difficulties diplomats faced during the negotiation of the Protocol are much the same-genuine scientific uncertainty over the scale of harm, a sharply divided international community, potentially high transition costs, and a global problem requiring a global solution. . The Protocol was thus the first treaty to address fully the global nature of a set of pollutants.
A. The Science And Economics Of Ozone Depletion
The stratospheric ozone layer blankets the earth in a protective shield that
effectively protects life on earth from the sun's harmful ultraviolet radiation
(UV-B). Since 1974, scientists have suspected that an important group of man
made chemicals, including most notably chlorofluorocarbons (CFCs), could break
down ozone molecules in the upper atmosphere. Over time, the role of CFCs and
other ozone depleting substances (ODSs) in reducing the ozone layer has been
confirmed. As a direct result of ozone layer depletion, increased UV-B strikes
the earth's surface. This increase in UV-B has a potentially serious impact
on human health and animals, including causing skin cancers and cataracts, damaging
human immune systems, disrupting the food cycle of the ocean, and reducing the
productivity of important agricultural crops and other plants.
The earth's atmosphere is divided into several different layers, defined by
the variation of temperature with altitude. The lowest layer is the troposphere,
extending to approximately 12 km above the earth. Immediately above the troposphere
is the stratosphere, extending from 12 km to 50 km. The troposphere is very
turbulent, affected strongly by the different characteristics of the earth's
surface, whereas the stratosphere is relatively stable.
Ozone (O3) is a simple molecule of three oxygen atoms. Ozone occurs naturally
as a trace element of the atmosphere. According to a UNEP report, "If all
the ozone in the atmosphere from ground level to a height of some 60 km could
be assembled at the earth's surface, it would comprise a layer of gas only about
3 mm thick, weighing some 3000 million tonnes." Although ozone occurs throughout
the troposphere and stratosphere, the highest concentration of ozone occurs
in the middle of the stratosphere, in a region commonly called the "ozone
Ozone, although a relatively small part of the atmosphere, performs a critical function. It absorbs certain frequencies of harmful UV-B radiation emitted from the sun. In the stratosphere, as ozone molecules absorb the incoming UV-B radiation, the energy blasts them apart. An equilibrium is maintained, however, by a series of chemical reactions that create ozone as a counterbalance to the ozone destroyed through absorption of UV-B radiation. It is this delicate balance that has been disrupted by the introduction of increased levels of CFCs and related substances, for now more ozone is destroyed than created.
Much of the early publicity over ozone depletion centered around the recurring
Antarctic "ozone hole." Ozone depletion is worst in Antarctica because
the ozone destroying reaction catalyzed by ODSs occurs fastest on the surface
of atmospheric micro ice crystals. These ice crystals are most common in the
coldest areas, for example on polar stratospheric clouds over Antarctica in
the winter. Nonetheless, during the past decade, measurements of actual ozone
loss have been made over all parts of the planet, with the exception of the
The European Commission reported that the Arctic stratosphere may have lost up to 60% of its ozone during the 1999-2000 winter and that the average ozone concentrations over Europe were 15% less than those of the early 1970s. And NASA reported the ozone hole over Antarctic was three times the size of the United States, the largest it has ever been. All other things being equal, scientists generally estimate that every 1% decline in the ozone layer produces a 2% increase in UV-B radiation at the earth's surface.
B. Impacts of UV-B On Human Health And The Environment
Increases in UV-B radiation lead to increased skin cancers, cataracts and sunburns. UNEP's 1998 Assessment predicts that, even if countries fully comply with the ozone agreements, incidences of skin cancer will continue to increase until 2060.
UV-B has been demonstrated to suppress the immune systems in humans with respect to some diseases. Unlike sunburns and skin cancers, the immuno suppression impacts of UV-B affects humans of all skin color pigmentation. There is great uncertainty in quantifying the likely impacts of ozone depletion on immune systems, though recent studies have shown that the most sensitive 5% of individuals in a population of white Caucasians suffer significant inhibition of their cellular immunity against a bacterial infection when they are exposed to sunlight for 90 minutes around noon.
- Aquatic Ecosystems And Wildlife
Increases in UV-B can reduce the growth of marine phytoplankton, which is the base of the ocean food chain and produces at least as much biomass as all terrestrial ecosystems combined. UV-B also damages midge larvae, the base of many fresh water ecosystems. Amphibians and fish are also particularly vulnerable to UV-B.
- Materials Damage
C. The Economics Of Ozone Depleting Substances
Many compounds containing chlorine are released into the environment, but most do not reach the stratosphere because they are water soluble and are "absorbed" into clouds. CFCs and the other human made ODSs share two important qualities: they are chemically stable and insoluble in water. These qualities have made CFCs and other ODSs very valuable to industry for a wide range of uses, even as they make it possible to cause ozone depletion.
There are many kinds of CFCs, each with specific qualities and applications. Traditionally, major uses of CFCs have included air conditioning, refrigeration, foams, foam packaging, aerosol propellants, cleaning of electronics, and degreasing of parts. The Alliance for a Responsible CFC Policy, an industry group made up of ODS manufacturers, estimated in 1986 that CFC products were worth more than $20 billion and created over 250,000 jobs in the U.S. alone.
Other ODSs are also commercially valuable chemicals. Halons, for example, are widely used in fire extinguishers, carbon tetrachloride and methyl chloroform are used as cleaning agents, and methyl bromide is a popular agricultural pesticide used to control a wide variety of pests on over 100 crops.
D. The Vienna Convention For The Protection Of The Ozone Layer
Attended by 43 nations (of which 16 were developing countries) and three industry
groups, negotiations over the Vienna Convention produced the first international
agreement to address CFCs.
The result of these initial negotiations, the Vienna Convention for the Protection of the Ozone Layer, was signed by 20 countries. Rather than controls on CFC consumption or production, the Convention called for countries to take "appropriate measures" to protect the ozone layer and established an international mechanism for research, monitoring and exchange of information. At the end of the meeting, despite objections by the European Community, a non binding resolution was passed calling for the next meeting to work toward a legally binding protocol addressing controls. Nonetheless, with the Vienna Convention's failure to establish controls on production or consumption, the future of CFCs still seemed bright.
E. The Montreal Protocol On Substances That Deplete The Ozone Layer
In 1985, two months after negotiations ended over the Vienna Convention, British scientists announced an "ozone hole" in the Antarctic, triggering enormous public interest in ozone depletion.
The negotiations in Montreal could not have shown a greater contrast to the
small affair two years earlier in Vienna. With over 60 countries participating
(more than half from developing countries), many industrial and environmental
groups, and wide media coverage, the world's attention focused on Ozone depletion.
In the Vienna Convention, no chemicals had been identified or regulated as
ODSs. The Protocol, however, not only froze production and consumption levels
of CFCs upon ratification (CFCs 11, 12, 113, 114, 115) and of halons three years
later (Halons 1211, 1301, 2402), but also set in place a reduction schedule
for CFCs. By 1998, a 50% reduction in CFC consumption was to be achieved. Because
monitoring consumption of ODS was thought infeasible, a surrogate formula was
adopted defining a country's consumption of CFCs or halons as: consumption =
production + imports - exports.
If the Protocol's only teeth were scheduled phase outs of controlled substances,
countries would have a strong incentive not to sign in order to gain the newly
freed market share for themselves. To avoid this free rider behavior and as
an incentive for countries to join, the Protocol provided tough trade measures.
Regarding imports, parties to the Protocol are prohibited from importing from
non parties either controlled substances or certain products containing controlled
substances. These products include domestic, commercial and vehicle air conditioners,
refrigerators, and portable fire extinguishers. The parties also decided to
ban the import of products produced with controlled substances. While parties
agreed on a list of products containing controlled substances, they had difficulty
in drawing up a similar list for products produced with controlled substances
and, as a result, left it to each party to draw up its own list of products.
The country of origin can avoid these onerous restrictions only if it demonstrates
full compliance with the Protocol's reduction schedules.
Regarding exports, parties must similarly ban the export of controlled substances
to non parties unless the country of destination can demonstrate full compliance
with the Protocol's reduction schedules. Exports to non parties that are in
compliance are not counted as exports in the country's consumption calculation,
so they must be offset by an equal reduction in production or imports.
With 24 nations signing in Montreal, the Protocol was universally hailed as a diplomatic triumph. Starting from low or no expectations in Vienna, within eighteen months strict international controls had been negotiated that would be refined and changed over time with the benefit of more knowledge. This structured evolution marked a new feature of international environmental law and showed great foresight. Not only have the parties met regularly since 1987, but every time parties have sought to tighten reduction schedules and bring new compounds under control.