- How do CFCs destroy ozone in the earth's atmosphere?
- What can we do to help "close" the ozone hole?
In 1992, representatives of countries from around the world gathered in Rio de Janeiro for what was called the Earth Summit.
What resolutions concerningozone depletion came out of this meeting?
1. What can we do to help "close" the ozone hole? 2. In 1992, representatives of countries from around the world gathered in Rio de Janeiro for what was called the Earth Summit. What resolutions concerning ozone depletion came out of this meeting?
- a chemical element important in the destruction of ozone
- chlorofluorocarbons (CFCs):
- chemical compounds made up of carbon, fluorine, and chlorine
- a molecule made up of three atoms of oxygen
- the layer of the earth's atmosphere just above the troposphere; extends from 15km to about 50km above the earth
- total ozone mapping spectrometer:
- an instrument flown aboard the NIMBUS-7 spacecraft that provides high-resolution mapping information about atmospheric ozone content
- ultraviolet radiation (UV-B):
- high energy electromagnetic waves that lie beyond the purple end of the visible spectrum
>Ozone TRY ITS
OverviewOzone is a gas, a form of oxygen, that is found in the layers of the atmosphere, most predominantly in the stratosphere . Here, 90% of the atmosphere's ozone is distributed in a ratio of five ozone molecules to every million molecules of other gases. This minute distribution serves as a shield that helps screen the sun's rays by absorbing some of the ultraviolet(UV-B)radiation . Depletion of the ozone in the atmosphere can have severe consequences on earth. Plants, animals, and humans all suffer when exposed to higher levels of ultraviolet rays. Food crops have stunted growth; marine phytoplankton can die off; and humans are more vulnerable to skin cancer. Atmospheric research in the mid-1980s indicated a serious thinning of the ozone shield, upsetting a natural balance between oxygen and ozone in the stratosphere. This thinning was evident from satellite pictures and showed up as a dark area; thus the term "ozone hole" was coined. It was apparent to scientists studying the ozone depletion that chemicals called chloroflourocarbons (CFCs) , used in spray cans, refrigerators and air conditioners, foam, plastics, and cleaning solvents, might be contributing to the problem. After being released, either during the manufacturing process or from consumer use, CFCs reach the stratosphere. There, chemical reactions break apart the CFCs. The chlorine then breaks down the ozone. A single chlorine atom can destroy 100 thousand molecules of ozone. The degree of ozone depletion has followed an annual cycle that corresponds to the amount of sunlight that reaches the Antarctic. The cycle begins every year around June when the vortex winds develop in the Antarctic. Cold temperatures produced by these winds create polar stratospheric clouds that capture the floating CFCs. For the next two months, a reaction occurs on the cloud surface that frees the chlorine in the CFCs but keeps the chlorine contained within the vortex area. In September, sunlight returns to the Antarctic and triggers a chemical reaction, causing chlorine to convert ozone to normal oxygen. Measured ozone levels usually are lowest in October. November brings a breakdown in the vortex that allows the ozone-rich air to combine with the thinning ozone. Wind currents carry this mixture over the southern hemisphere and carry the "hole" over other areas of the earth.
ActivityAnalyze and interpret the same ozone TOMS images as those used by NASA. Before information about ozone is released to the general public, scientists spend many hours analyzing ozone data from earth and space. Here's your chance to be an ozone-research analyst. Materials
- NIMBUS-7 TOMS Images: The Twelve Octobers. Order one for each two students by lithograph name and number (HqL-308) from: NASA Goddard Space Flight Center Greenbelt, MD 20771 (301) 286-8955
- Divide students into research-analyst pairs.
- Discuss why the Dobson Unit key will be important and note the range of the value for each color. (If paper copies have been made, allow time for the students to color in the key.)
- Use the questions below to analyze this data and to formulate predictions.
- Aeronomy Laboratory/NOAA
Boulder, CO 80303
Climate Protection Institute
5833 Balmoral Drive
Oakland, CA 94619
Mail Code F
Washington, DC 20546
(Atlas 1 Teacher's Guide: Earth's Mysterious Atmosphere)
Larain County, JVS
15181 Route 58 S
Oberlin, OH 44074
(216) 774-1051 Ext. 293
(videotapes from shuttle missions during which Blue Planet was filmed)
National Air and Space Museum
Office of Education
Washington, DC 20560
(Blue Planet educational booklet)
PBS Environmental Resource Compendium
1320 Braddock Place
Alexandria, VA 22314