The ozone layer is crucially important to life on planet Earth. Without the ozone layer, only the most primitive of life forms would be able to exist. The ozone layer currently has a hole in it (around Antarctica and the southern continents) that has continued to grow in size since it was first discovered in the early 1980’s. The exact dimensions of the ozone hole vary from year to year and fortunately, the rate of growth is declining. This has been in part due to world-wide efforts to address this most important environmental issue.
Background on the Ozone Layer
According to science writer, Desonie, Earth’s atmosphere is composed of similar atmospheric gases all throughout. The atmosphere is divided into six layers that are defined primarily by the changes of temperature that occur with altitude. The first two layers of Earth’s atmosphere are called the troposphere and the stratosphere.
The troposphere is the layer that is nearest to Earth’s surface. It rises from sea level to about six miles. The stratosphere rises from the top of the troposphere to about thirty miles. This is the layer of the Earth that contains the ozone layer.
The ozone layer lies between nine and nineteen miles from Earth’s surface and was named for its relatively high concentration of ozone molecules. When ozone is found in the troposphere it is considered a pollutant and a greenhouse gas. However, the ozone in the stratosphere protects Earth from the damaging high-energy ultraviolet radiation given off by the sun. These are referred to as UV rays.
The ozone layer is being destroyed by chlorofluorocarbons (CFC’s) as well as by other man-made chemicals which destroy ozone molecules. When the hole in the ozone layer was discovered in 1981 by British scientists it was roughly 900,000 square miles. Since then it has continued to grow in size with the exact size varying from year to year. In 2000, the hole was 11.4 million square miles which Desonie states is more than three times the size of the United States. Thankfully, great strides have been made to make changes that have resulted in the slowing down of the ozone hole rate of growth and it is hoped that with continued efforts the ozone hole itself will also actually begin to decrease in size.
Healing the Ozone Layer Hole
Efforts to address the environmental issue of the ozone layer began in 1973 when graduate student, Mario Molina, did his research on the effects of CFC’s on the ozone layer. His advisor, Sherwood Rowland checked and rechecked his work for errors, but to no avail. Their findings were startling: CFC’s rise to the Earth’s stratosphere and destroy its “fragile ozone shield”. Molina and Rowland won the 1995 Nobel Prize in chemistry for their profound work.
Their findings in the early seventies inspired several countries such as the U.S. and Canada to take action by banning CFC’s in spray cans. Once the actual hole in the ozone layer was discovered, additional countries were spurred on to get involved in efforts to heal the hole in the ozone layer. Desonie points out that many world political leaders began to mobilize around this most important environmental issue.
The Montreal Protocol on Substances that Deplete the Ozone Layer was ratified in 1983 and is an agreement that controls the production and consumption of ozone-depleting substances. This agreement became effective in 1989 and several amendments have been created and signed to increase the number of controlled substances under regulation and to regulate the trade of these substances between developed countries and developing countries. This is important because several developed countries have been guilty of using the black market to sell ozone-depleting substances to developing countries.
The goal of the Montreal Protocol (and its subsequent amendments) is to return the ozone layer to its 1970’s status. The protocol controls 96 substances. The usage of most of the substances has not been frozen, but is rather being phased out. There are different time tables set up for developed countries and those countries that are still developing. For instance, CFC’s were phased out in developed countries in 1995 while developing countries have been given more time to fully phase them out.
Effects of Ozone Layer Loss
Ozone loss contributes to non-melanoma skin cancer which has been linked to accumulated dosages of UV rays. Desonie states that increased UV exposure may also cause immune system suppression in some people reducing their defenses against infectious disease and some cancers. Exposure to UV rays can also affect plant by slowing growth and development and decreasing yields. Damage is actually done to the plant’s genetic code. UV rays even have harmful effects on the planet’s marine ecosystems.
While it is wonderful that the rate of growth of the hole in the ozone layer has decreased over recent decades, thanks to the efforts of countries around the globe, it is still an extremely important environmental issue. Interest in healing the hole in the ozone layer must not dwindle. Stratespheric ozone loss takes a great toll on human health and life as well as on all the other life forms on the planet.
References:
Desonie Ph.D., Dana. (2007). Atmosphere: Air Pollution and Its Effects. New York: Chelsea House.
