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Atmosphere, Climate



Stratospheric ozone is a very important gas because it absorbs most of the sun's harmful ultraviolet radiation and prevents it from reaching Earth's surface. However, the ozone layer has been depleting as the result of a complex set of circumstances and chemistry.

Ozone depletion is the term commonly used to describe the thinning of the Earth's protective stratospheric ozone layer. Ozone depletion occurs when the natural balance between the production and destruction of stratospheric ozone is tipped in favor of destruction. Natural phenomena, such as volcanoes and cold temperatures during the Antarctic winter, and human-generated ozone depleting substances can upset that balance, removing ozone faster than nature can produce it.

For example, the June 9-15, 2007, New Scientist reports findings that suggest volcanic eruptions in Siberia obliterated the Earth's ozone layer 251 million years ago. This coincides with the largest mass extinction in history, in accordance with atmospheric chemistry models. These models suggest that ozone-destroying halogen gases were released as lava reacted with coal and salt. (Philosophical transactions of the Royal Society A, DOI: 10.1098/rsta.2007.2046.)

One of the negative effects of ozone depletion is an increase in the number of people suffering from skin cancer. The relationship between skin cancer and uv radiation is well established. People of fair skin are generally more prone to skin cancer. For example, Queensland, Australia, which has high natural rates of uv radiation and a population largely of Northern European descent, has the highest rate of skin cancer in the world.

Since the 1920s scientists have measured ozone using ground-based instruments. The instruments, placed around the globe, measure the amount of ultraviolet radiation getting through the atmosphere at each site. From these measurements, scientists are able to calculate the concentration of ozone in the atmosphere above that location. While these data are useful in learning about ozone, they do not provide an adequate picture of global ozone concentrations. The amount and distribution of ozone molecules in the stratosphere vary greatly over the globe, and are continually moving.

NASA has been monitoring global ozone levels through satellite observations since the 1970s, beginning with the TOMS sensors (Total Ozone Monitoring Spectrometer), which operated on several satellites and provided data from 1978-1994 and August 1996-2007. The latest-generation ozone-monitoring technology, the Ozone Monitoring Instrument (OMI - pronounced oh-me), was launched in 2004 onboard NASA's Aura satellite.

TOMS and OMI measure total vertical column concentrations of ozone. By measuring the total sunlight striking the satellite and comparing it to the UV radiation scattered back from the atmosphere, it is possible to compute total ozone amounts.

Because ozone levels are derived from measurements of solar reflected and backscattered light, the satellite instruments require sunlight to operate. For that reason, there are periods when data is missing for the Antarctic and Arctic during the local polar winters - times when it is continuously dark. Areas where data is missing appear black in the satellite images. They are NOT the ozone hole. The thinning of the ozone layer in the stratosphere, as scientists recognize it, occurs in September and October of every year, which is springtime in Antarctica.

Ozone measurements given by TOMS and OMI are in Dobson Units (DU)--a measure of total ozone in a vertical column that stretches from a point on Earth to space. In 1924 Professor G.M.B. Dobson, one of the earliest ozone researchers, was faced with the problem of how to quantify the amount of ozone overhead. Comparing ozone molecules to oxygen molecules wouldn't work - the ratio changed as the height changed. So Dobson developed a new unit of measurement. He calculated that if all the ozone in a typical column of air over the U.S. were at standard temperature (0 degrees C) and compressed to surface pressure it would be about 3mm thick (or about as thick as 2 pennies). He defined this amount as 300 units, which were later named Dobson Units. In other words, one Dobson Unit is equal to a layer of ozone .01 mm thick, that has been condensed to surface pressure and cooled to 0 degrees C. (Pickle, et al., Global System Science: Ozone, 2004, Lawrence Hall of Science).

For more information, data, and images from OMI and TOMS go to:

In the 1970s, researchers began to think that human activity could affect the ozone layer. At the time, they were focusing on the exhaust from supersonic airplanes and the space shuttle. After studying other possible causes for ozone depletion, however, the international community came to a consensus that certain synthetic chemical compounds called chlorofluorocarbons (CFCs) were largely responsible for the ozone loss. As a result, the Montreal Protocol was adopted in 1987, calling for the worldwide elimination of CFCs and other ozone-destroying substances. So far, the Montreal Protocol has been signed by 191 nations. The Protocol has been amended several times, most recently in 1999.



The government of Queensland, Australia, is concerned that the Montreal Protocol is too lax on its control of some substances. The Queensland government has called upon your Earth System Science team to act as consultants to review the many issues that surround ozone depletion. Your role is to evaluate the current understanding of the cause-and-effect interrelationships of Earth's systems related to ozone depletion. The Queensland officials who will attend the annual fall meeting of the Parties to the Montreal Protocol and will use the information you provide to prepare for the meeting.


Date: 6/29/2007

Scenario Images:

Ozone, 1979-2004
TOMS Ozone Data, 1979-2004

Click here to watch movie

This animation shows total ozone in the Antarctic region along with the maximum ozone depth and size from 1979-2004 (data dropouts have been removed). The minimum ozone recorded is 82.0 Dobson Units (DU) on September 26, 2003. The maximum area of 29 million square kilometers (11.4 million square miles) occurred on September 9, 2000. Very low levels of ozone are represented by purple and blue, medium by green and yellow, and high levels by red. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio.

May take several minutes to load on slower connections. Tip for using in the classroom: download the animation to your computer.



Critical Chemistry (Cycle A)
This feature article on NASA's Earth Observatory explains why understanding nitrogen oxide distributions is important to understanding the production of ozone.


NASA Ozone Resource Page (Cycle A)
Contains the latest science, news, articles and multimedia resources related to Ozone. Link to all past NASA press releases related to stratospheric ozone. Click here for NASA study showing unprecedented 2011 ozone loss in the Arctic.


Neumayer Antarctic Station (Cycle A)
In situ measurements from radiosondes up to 35 km at the Neumayer Antarctic station.


Ozone Hole Meteorology: 2009 Ozone (Cycle A)
NASA Ozone Watch comparisons and data 1979-2009.


Ozone Levels Drop When Hurricanes Are Strengthening (Cycle A)
2005 press release from NASA.


United Nations Environment Programme - Ozone Secretariat (Cycle A)
Report of the UNEP Environmental Effects Assessment Panel.


US EPA - Ozone Web Site (Cycle A)
Good background information from the US EPA including regulations in the US to protect the ozone layer, flyers about the UV index, and international ozone policies.


What is ozone and why do we care about it? (Cycle A)
A NASA fact sheet on ozone.


Climate Change may Become Major Player in Ozone Loss (Cycle B)
NASA study finds that by the 2030s climate change may surpass chlorofluorocarbons (CFCs) as the main driver of overall ozone loss. UNEP Environmental Effects of Ozone Depletion and its Interactions with Climate Change 2009 Progress Report


Future Volcanic Eruptions May Cause Ozone Hole Over Arctic (Cycle B)
NASA press release from 2002: Scientists say the northern ozone hole may reappear for several consecutive years after a period of high volcanic activity.


NASA and NOAA Announce Ozone Hole is a Double Record Breaker (Cycle B)
2006 NASA press release.


Ozone, Nitrogen Change the Way Rising CO2 Affects Earth's Water (Cycle B)
Through a recent modeling experiment, a team of NASA-funded researchers have found that future concentrations of carbon dioxide and ozone in the atmosphere and of nitrogen in the soil are likely to have an important but overlooked effect on the cycling of water from sky to land to waterways. 2009


Stratospheric Ozone and Human Health Project (Cycle B)
Displays reports from the United Nations Environment Program and the World Meteorological Organization on the environmental effects of ozone depletion. Contains reports from 1994 - 2000.


Total Ozone Mapping Spectrometer (Cycle B)
This site from NASA's Goddard Space Flight Center allows you to access realtime ozone data from TOMS and OMI and download animations, graphics, and images of ozone depletion and the Antarctic ozone hole. Select "Teachers" to view lesson plans on this subject. Click on the link for "Ozone Over Your House" where ou can find the total column ozone amount over your house (or anywhere else) using data from the Ozone Monitoring Instrument (OMI) on the Aura spacecraft. Just enter the date, latitude, and longitude you want.


NASA has developed microsets of Earth science data for K-12 education, which can be used with existing curriculum and enable students to practice math skills using real measurements of Earth system variables and processes.

The microsets are created using data from NASA Earth science satellite missions and provide information on the atmosphere, ocean and land surface. New data types continue to be added to the collection. Data is available online along with K-12 lesson plans, computer tools and an Earth science glossary.

Use the Live Access Server to create your own microsets of NASA data. The LAS contains over 128 parameters in atmospheric and Earth science from five NASA scientific projects Click here for an overview of the parameters and time period available.


Scaffolding For Success In Problem-based Learning (Cycle C)
This paper is authored by Tony Greening of The School of Information Technology and Mathematical Sciences at the University of Ballarat, Australia. It makes the point that although PBL encourages student independence, the provision of an appropriate support structure is critical for success.


USC California Science Project (Cycle C)
The California Science Project (CSP) was started in 1990 to train K-12 science teachers. The teacher training was done using problem-based learning. Not only did teachers get to know the science content areas using PBL, they also learned how PBL can be used as a learning tool. They could then use PBL to instruct students in their K-12 science classes.


Webquest Matrix: (Cycle C)
This selective listing shows webquest lessons for Grades 9-12 in all curriculum areas.


Sample Investigations:


Earth Exploration Toolbook: Analyzing the Antarctic Ozone Hole (Cycle A)
Users examine satellite images that show how much ozone is in the atmosphere over the Southern Hemisphere. They interpret the images to identify the ozone hole that develops over this region every year during the Southern Hemisphere's spring, and compare its size from year to year.

Using freely available image analysis software, ImageJ, users quantify the area of the Antarctic ozone hole each October from 1996 to 2004. Finally, they bring their measurements into a spreadsheet program and create a graph to document changes in the size of the ozone hole. For grades 7-10
Difficulty: intermediate


Exploring the Environment: UV Menace (Cycle A)
A module from the NASA Classroom of the Future's Exploring the Environment site through which students use Problem-Based Learning to investigate the topic of ozone depletion. For grades 10-12.
Difficulty: advanced


MY NASA DATA: Validation of Stratospheric Ozone (Cycle B)
An example case study of validating NASA satellite data with atmospheric sounding observations of atmospheric ozone levels using either graphing calculators or Microsoft Excel.

Note: the term graphing calculators for this lesson is in reference to Texas Instruments graphing calculators, specifically the TI-84 Silver Plus. For grades 9-12.
Difficulty: intermediate


Ozone " The Sky Isn' Falling but There's a Hole Up There" (Cycle C)
In this activity, students calculate the rate of change of ozone depletion over Antarctica. The activities in this educator's guide are related to NASA's Earth science research. (NOTE: The activities were originally developed to supplement the "NASA Earth Science Enterprise CD-ROM" which is now out of print. For grades 5-12.)
Difficulty: intermediate




  • Science
    National Science Education Standards - Science Content Standards The science content standards outline what students should know, understand, and be able to do in the natural sciences over the course of K-12 education.
      The understandings and abilities associated with the following concepts and processes need to be developed throughout a student's educational experiences:
      • Evidence, models, and explanation
      • Science as Inquiry (Std A)
        • Abilities necessary to do scientific inquiry
      • Earth and Space Science (Std D)
        • Structure of the earth system
      • Science as Inquiry (Std A)
        • Abilities necessary to do scientific inquiry
      • Earth and Space Science (Std D)
        • Energy in the earth system
      • Science in Personal and Social Perspectives (Std F)
        • Environmental quality
        • Natural and human-induced hazards
        • Science and technology in local, national, and global challenges
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