Ozone Depletion
Ozone Depletion

Like global warming, depletion of the ozone layer raises complex problems of cause and effect that have led to international disagreements over coordinated efforts to reverse the problem. Unlike global warming, however, ozone depletion has actually been successfully controlled by international cooperation, perhaps providing a model for other efforts at global environmental protection.

Ozone is an invisible, poisonous gas molecule (O3) that exists in trace (minimal) amounts in the stratosphere (6-30 miles above the earth). It makes life on earth possible by shielding the planet from 95-99 percent of the sun’s harmful ultra-violet (UV) rays, which can cause skin cancer, degenerative eye damage, and suppressed immune response. Rodents subjected to UV irradiation are more likely to die from viruses such as malaria, influenza, and herpes. In addition, increased UV radiation upsets the balance of ecosystems and disrupts many chemical and physical processes that occur in nature’s cycle.

For example, elevated UV levels have been shown to compromise the aquatic food chain, alter plant-insect interactions, change the growth patterns of fungi, and slightly reduce the productivity of agricultural plants.

Basic natural cycles involving nitrogen, sulfur, carbon dioxide, and decomposition of biological matter are also affected. Also, increased UV radiation in the lower atmosphere, or troposphere, helps cause photochemical smog. Finally, solar rays augment and interact with the global warming trend.

According to the U.S. National Aeronautics and Space Administration (NASA), from 1978-1991 there was a net decrease in global ozone of 3 percent per decade, and “every 1 percent decrease in the earth’s ozone shield is projected to increase the amount of UV light exposure to the lower atmosphere by 2 percent” (Sparling, 2011). UNEP has reported that since measurements started in the early 1980s, the ozone layer over Antarctica—the world’s most vulnerable region because of the extreme cold and presence of polar stratospheric clouds—has steadily eroded. This resulted in ” ozone holes” over land.

The ozone hole in the South Pole grew to about five billion acres in the early 1990s and, at times, increased to seven billion acres. In 2001, the ozone layer had thinned up to 30 percent at the North Pole and 5-30 percent in Europe and other high latitudes. In 2007, the ozone loss tired at 27.7 million tons, surprisingly less than in 2006, which saw a record loss of 40 million tons.

At its maximum size, in 2006, the ozone hole in the Antarctic zone reached 27 million square kilometers. This is about 2000 square kilometers larger than North America. In 2009, at its maximum size, the ozone hole reached 24 million square kilometers, decreasing from the previous year and still smaller than the 2006 record size, according to images collected by the NASA Aura satellite (Nasa, 2011). By the end of 2012 the ozone hole area was reduced to 18 million square kilometers, the lowest levels seen in over a decade (Ozone Watch, 2012).

The main cause of ozone depletion is emissions from man-made sources of halocarbons, most notably chlorofluorocarbons (CFCs). Discovered in the early 20th century, these “wonder gases” were renowned for their industrial properties and used in a wide range of applications, including refrigerators, air conditioners, aerosol spray cans, solvents, foams, and fire extinguishers. The downside of these gases is that they linger in the atmosphere—50, 65, 100, or as long as 1,700 years—and thus cause long-lasting environmental damage. The chlorine in CFC interacts chemically with ozone and breaks it up into constituent molecules of oxygen, reducing the capability of the ozone layer to block UV rays (Clark, 2011).

The international response to the ozone threat has been perhaps the most successful of all global environmental efforts. In 1985, The Convention for the Protection of the Ozone Layer (known as the Vienna Convention) committed countries to take “appropriate measures…to protect human health and the environment against adverse effects resulting or likely to result from human activities which modify or are likely to modify the Ozone Layer” (Vienna Convention, 1985). At that point, scientific understanding of ozone depletion was still limited, so specific measures were not put in place, but countries were willing to recognize the problem and agree in principle to combat it.

As scientists developed precise knowledge of how ozone depletion occurs and started finding definitive proof of an ozone hole, the parties to the Vienna Convention were more inclined to take specific action and thus negotiated the Montreal Protocol on Substances that Deplete the Ozone Layer. Completed in 1987 and with 197 parties and the EU as of May 20113 the Montreal Protocol established tough guidelines for reducing usage of ozone-depleting substances while allowing leeway for the economic growth of developing countries and changes based on scientific advances.

Under an amendment process, the Montreal Protocol can be updated to reflect better understanding of the ozone problem without having to re-negotiate the whole agreement, so that the agreement is flexible yet steadfast. This process has resulted in four subsequent amendments: in London (1990), Copenhagen (1992), Montreal (1997), and Beijing (1999). In March 2007, the U.S. submitted an amendment to speed the elimination of ozone-depleting substances.

Like the effort to stop global warming, the drive to end ozone depletion was based on the principle that rich countries could better afford to implement environmental protection than poor countries. The Montreal Protocol therefore established separate phase-out schedules for the two groups, granting developing countries a grace period. Now, of the 96 ozone-depleting chemicals controlled by the protocol, developed countries have already phased out use of most of them and are far along in eliminating the rest. Developing countries are still in the primary process of phasing out CFCs and other gases called halons, but are expected to make substantial progress on these and other substances in the next decade.

Klaus Toepfer, executive director of UNEP, insists that continued leadership by the rich countries will be needed to eliminate ozone depletion permanently. Developing countries, such as India, China, and Brazil, received $470 million from 2006-2008 to help to cut back on their production and consumption of ozone-depleting substances (UNEP, 2008).

Since 1990, $2.4 billion of assistance from the Montreal Protocol’s Multilateral Fund has underwritten over 6,000 projects to reduce usage of ozone-depleting substances in 148 developing countries. The resulting reductions total 230,768 tons in production and 175,864 tons in consumption (UNEP, 2008). Toepfer has commented that, “To maintain this momentum, the donor countries must continue supporting developing countries in their transition to ozone-friendly technologies… [T]he partnership between developed and developing countries must remain strong and effective.” The Fund’s replenished budget for the 2012-2014 period is currently $450 million.

So far, the Montreal Protocol has yielded impressive results. Between 1986 and 2006, annual worldwide consumption of CFCs declined from 1.1 million tons to 35,000 tons. UNEP projects that if not for the Montreal Protocol, by the year 2050 ozone depletion would have risen 50-70 percent, roughly ten times worse than current levels. Instead, the ozone layer is expected to reach a low point in the next few years and gradually recover to its normal state by 2050. (UNEP, 2008). Since its peak in 2006 the ozone hole has both expanded and diminished but overall trends seem to indicate a trend back to its normal state.

Source: Ozone Watch

This success in turning back ozone depletion may provide a model for other efforts to combat global environmental problems. The Vienna Convention and Montreal Protocol succeeded because rich countries first took the lead and made the effort credible, and only then asked less developed countries to follow suit.

Also, governments were able to work with industry to develop alternative technologies and chemicals to replace CFCs and other ozone-depleting chemicals. Finally, countries embraced a “precautionary principle” of acting to protect the environment despite a lack of conclusive scientific evidence, and then tightened and modified their policies as further scientific research warranted.

As we have seen with global warming, however, and will see with other environmental problems, consensus on finding solutions to environmental problems is not easy to find. The split between rich and poor nations and between economic development and environmental protection often cannot be bridged. Similarly, some nations are more supportive of the precautionary principle than others.


Next: Pollution