Ozone Layer Depletion: Introduction

Are we damaging our protective blanket?

Sunlight contains some ultraviolet light, and when we expose ourselves to too much of it, we get a sunburn. Over time, too much exposure to ultraviolet light can lead to cataracts and skin cancer. The earth has a layer in the upper atmosphere, consisting mostly of ozone gas, that filters out most of the ultraviolet in the sun's radiation. Recently there has been scientific evidence that we have been releasing gases that damage this layer. Our country and others have reacted by invoking legislation that should eliminate these contaminants from the atmosphere.

What does the Ozone Layer do?

• Ozone absorbs 99% of the harmful ultraviolet (UV) radiation.

Without the Ozone Layer

• Most of the harmful UV radiation will penetrate the atmosphere.

What Causes Ozone Depletion?

• Chlorofluorocarbons (CFC's) produced in the lower atmosphere put chlorine into the stratosphere.
• CFC's are very useful, and very large amounts were produced over the past 30 years.
• CFC production grew from 150,000 tons in 1960 to over 800,000 tons in 1974.

http://core.ecu.edu/phys/spraguem/environment/ozone/o3_01.html
This page is a supplement to Mark Sprague's Physics and the Environment, Phys 1050(1), class at East Carolina University.

All About Ozone

Ozone is a relatively simple molecule, consisting of three oxygen atoms bound together. Yet it has dramatically different effects depending upon its location. Near Earth's surface, where ozone comes into direct contact with life forms, it primarily displays a destructive side. Because it reacts strongly with other molecules, large concentrations of ozone near the ground prove toxic to living things. At higher altitudes, where 90 percent of our planet's ozone resides, it does a remarkable job of absorbing ultraviolet radiation. In the absence of this gaseous shield in the stratosphere, the harmful radiation has a perfect portal through which to strike Earth.

Stratospheric ozone occupies the region of the atmosphere between 10 and 50 kilometers from the earth's surface and provides a shield against damaging ultraviolet radiation.

http://www4.nationalacademies.org/beyond/beyonddiscovery.nsf/web/ozone3

A concerted global effort has been made to protect the earth's ozone layer — our planet's fragile sunscreen.

Production of the industrial chemicals which once posed a major threat to the ozone layer has been greatly reduced, and levels of some of these chemicals are now beginning to decline in the lower atmosphere.

The ozone layer is expected to eventually recover, if all nations maintain their efforts to reduce ozone-destroying chemicals. However, it will probably be more than a decade before we begin to see definite signs of a recovery, and at least the year 2050 before any substantial recovery occurs. At present, the layer is still thinning, especially at the earth's poles. The "hole" over the Antarctic is continuing to grow and considerable depletions are occurring in the Arctic.

Mid-latitude areas, such as southern Canada and the U.S., are also still experiencing ozone thinning.

Canada has played a key role in protecting the ozone layer. Our nation was instrumental in the development of the Montreal Protocol, the international agreement to reduce ozone-destroying chemicals. Canada is also a leader in the scientific research which guides international action to protect our fragile skies.

Yet, we still have much to do - we must find ways to reduce the use of the remaining industrial chemicals that continue to damage the ozone layer, and to guard against any new threats. Scientists need to learn more about ozone depletion, and how other stresses on the environment, such as climate change, are affecting the upper atmosphere.

http://www.msc-smc.ec.gc.ca/cd/factsheets/ozone/index_e.cfm

Stratospheric Ozone Depletion

This is a resource file for both teachers and students interested in the ozone layer. Stratospheric ozone depletion is a concern because the ozone layer in the stratosphere keeps 95-99% of the suns ultraviolet radiation from striking the earth. In this file are:

1.       Internet resources for both ozone information, and neat digitized images of the antarctic ozone hole.

2.       Printed information including phone and e-mail contacts for those who wish to pursue the issue of ozone depletion further. For those in a hurry, my favorite source of quick yet reliable answers is Frequently-asked-Questions on Ozone by Robert Parson. For general science questions on the atmosphere the college undergrad textbook Atmospheric Change: An Earth System Perspective, an authoritative text accessible to those with a high school science background.

3.       An important part of the ozone discussion is the use of scientific models in an effort to better understand the problem and make useful predictions. I have written a laymans guide to scientific modelling which can aid you in understanding some of the applications and limitations of modeling.

4.       Some of the controversies surrounding the science and theories of ozone depletion are summarized here.

5.       Brief glossary of some of the terms and concepts used when discussing ozone depletion.

6.       A summary of the ozone depletion issue, below, with highlighted terms that you can click on for further information.

Stratospheric ozone depletion is a concern because the ozone layer in the stratosphere keeps 95-99% of the suns ultraviolet radiation from striking the earth. A number of consequences can result from increased levels of UV(ultraviolet radiation) striking the earth, including: genetic damage, eye damage and damage to marine life. Increased UV radiation in the lower atmosphere, called the troposphere, can result in increased amounts of photochemical smog. Photochemical smog is already a health hazard in many of the world's largest cities.

The decrease of stratospheric ozone was first reported in 1974 and the decrease was quickly linked to the increasing presence of a class of manmade compounds called CFC's or Chlorofluorocarbons. Many countries of the world have moved to reduce the use of CFC's but because of the slow rate of air mixing between the lower and upper atmosphere it is theorized that stratospheric CFC's will stay at a significant level well into the next century.

Stratospheric ozone depletion has become very much a controversial political and economic issue as well as a complex scientific issue. Major and minor sources of chlorine, and factors which affect ozone levels are still being sorted out among a great deal of media-generated excitement and misinformation; but the link between CFC's and Ozone depletion, and the major factors creating the antarctic ozone hole, are considered by most researchers to be well established facts. Scientific models of the atmosphere are being constructed in order to assist scientists in looking for other factors in Ozone depletion, evaluate their importance and predict what may happen to our atmosphere in the future.

**This file may be copied, distributed and archived but all copies must include this caveat as well. Caveat: This document is a compilation of information from a number of sources, with the gracious assistance of NASA and the IISME program, but does not necessarily reflect their views and definitely does not reflect the breadth of their knowledge. I am solely responsible for what is written here, including errors. Students should note that since this is not a peer reviewed publication, it should not be used as a reference for science projects; instead all scientifc facts and data should be referenced back to the original authors.

Brien Sparling. Chemistry Teacher. Live Oak High School. Morgan Hill. California. 95037

Curator: Jill Dunbar    Last Update: May 30, 2001     NASA Official: William J Feiereisen

http://www.nas.nasa.gov/About/Education/Ozone/    NASA Advanced Supercomputing Division

Additional Resources:

    Ozone Depletion  

http://www.soton.ac.uk/~engenvir/environment/air/oz_intro.htm

The Earth's Atmosphere

Access Energy www.energy.ca.gov Main Website Information about the Energy Commission, its programs, proceedings, and statistics about energy production and use in California.

Consumer Energy Center www.ConsumerEnergyCenter.org Consumer Energy Center Everything there is to know about energy efficiency for the home or business, information about alternative fuel vehicles and buying an energy efficient vehicle, and information about renewable energy.

Energy Quest www.EnergyQuest.ca.gov Energy Education Web Site   Our award-winning energy education site for students with great resources for parents and teachers has Its Own WEB Address!

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