Holes in Ozone Layer of Earth

Photograph

By: National Aeronautics and Space Administration (NASA)

Date: September 30, 2002

Source: Corbis

About the Organization: The National Aeronautics and Space Administration, or NASA, is the agency of the U.S. government responsible for exploration of space and the atmosphere immediately around Earth.

INTRODUCTION

The depletion of the ozone layer of Earth's atmosphere refers to the development of a hole in the stratosphere over the south pole of the planet. This hole has been caused by mankind's steady usage of chemicals known as chlorofluorocarbons (CFCs), which pollute the air and have eaten through this protective layer. The purpose of the ozone is to block out the more dangerous rays of the sun, specifically ultraviolet (UV) rays, that would be harmful to life on the planet. UV rays first affect smaller life forms—one-celled organisms, such as plankton—but this creates a domino effect by eliminating the bottom level of the food chain and thereby creating a food shortage for the larger creatures that survive on the one-celled animals. This shortage continues to work its way up, eventually affecting humans. In addition, the thinning of the ozone overall and the gradual filtering of UV rays into the atmosphere affects the average temperature on the planet, the way sun reacts on unprotected skin, and many other aspects of the planet's ecology.

PRIMARY SOURCE

HOLES IN OZONE LAYER OF EARTH

See primary source image.

SIGNIFICANCE

CFCs were initially put into use because, while they had chemical and physical properties that allowed them multiple uses, they were far less toxic to human beings than many of the other chemicals put to similar purposes. As a result, they became primary components of refrigerators and air conditioners as part of the cooling systems, and were used as a propellant for products in aerosol cans. However, in the early 1970s, Dr. Sherwood Rowland and Dr. Mario Molina, both physical chemists, discovered that CFCs were likely to break down within the ozone layer into reactive chlorine atoms, damaging the stratosphere. Although there were attempts to reduce the production of CFCs through the gradual phasing out of aerosol packaging for products, appliances that used CFCs were being marketed at an increased rate around the world. It was not until a large hole was discovered in the ozone over Antarctica that the problem was given the serious attention that it warranted.

Dr. Rowland and Dr. Molina, along with Dr. Paul Crutzen, were awarded the Nobel Prize for Chemistry in 1995 for their work at the University of California at Irvine in illuminating the dangers of CFCs to the ozone layer and the potential ramifications of that ongoing damage. The project was initiated by Dr. Rowland and Dr. Molina as part of a research contract with the Atomic Energy Commission, and began with an interest in how the expenditure of a new chemical compound into the air could potentially alter the atmosphere. Although the chemical had been proven extraordinarily stable, Rowland and Molina believed that was not sufficient reason to assume it was not harmful. They first presented their findings in 1974 at an American Chemical Society meeting, where they detailed not only the environmental ramifications of their research, but the need to enact specific public policies that would serve to combat the threat to the atmosphere. Their discoveries led to the development of an international treaty designed to end the production of CFCs, and to public policies that focus on preserving the quality of the planet's air and water quality, along with the forests and other natural resources.

Difficulties arose when it became clear that, although the science behind Rowland and Molina's findings was sound, there was no apparent evidence that CFCs were in fact damaging the ozone layer. Only in the early 1980s did the problem become visibly apparent. Joe Farman, a member of the British Antarctica survey who had been taking ozone measurements over Halley Bay for more than two decades, discovered that the levels of ozone were suddenly lower during the spring when the light first began to reappear after the long winter. The initial reaction was that the instruments were incorrect, particularly as NASA readings of the ozone over the entire planet had not indicated the problem. However, NASA returned to reexamine the area over Halley Bay and discovered that Farman's findings were indeed accurate. In fact, the ozone had depleted significantly, not just over Halley Bay, but all of Antarctica. Using the Total Ozone Mapping Spectrometer by satellite, color coding clearly delineated the hole that CFCs had created in the ozone layer.

By the mid-1980s, regular studies were in place to record the effects of CFCs on the atmosphere and to try and determine how it would be possible to reverse the damage. Products with CFCs began to be replaced with more ecologically safe technology, and a plan was developed that indicated the decades required in order to return the atmosphere to its pre-1975 ozone quality. The Environmental Protection Agency and other regulating committees joined to ensure that the restoration of the ozone would become a global initiative, and nearly 200 countries ratified the Montreal Protocol on Substances that Deplete the Ozone Layer, an international treaty written in 1987, which served as the basis for the Clean Air Act.

FURTHER RESOURCES

Web sites

"Press Release: The 1995 Nobel Prize in Chemistry." Nobel Prize.org, October 11, 1995. 〈http://nobelprize.org/chemistry/laureates/1995/press.html〉 (accessed March 5, 2006).

Rowland, F. Sherwood, and Mario J. Molina. "The CFC-Ozone Puzzle: Environmental Science in the Global Arena." NCSE Online, December 7, 2000. 〈http://ncseonline.org/NCSEconference/2000conference/Chafee/ChafeeMemorialLecture2000.pdf〉 (accessed March 5, 2006).

"Stratospheric Ozone Depletion." National Aeronautics and Space Administration (NASA). 〈http://www.nas.nasa.gov/About/Education/Ozone〉 (accessed March 5, 2006).

"What Has EPA Done About Ozone Depletion?" U.S. Environmental Protection Agency. 〈http://www.epa.gov/ozone/geninfo/actions.html〉 (accessed March 5, 2006).