module 3 educator’s guide investigation 2€¦ · a rapid decline in stratospheric ozone over the...

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The loss ofstratosphericozone: Where arepeople at risk?Investigation OverviewIn this investigation, students learn about the recent declines of ozoneconcentrations above Antarctica and the Arctic. These facts pose the riskthat unusually high amounts of harmful ultraviolet radiation will reach Earth’ssurface and threaten life, especially in the high latitudes. Students learn howhuman actions have affected the natural geography of stratospheric ozone,they estimate populations at risk from ozone destruction, and they learn howinternational complications obstruct solutions to the problem.

Time required:Beginning and Part 1: One to two 45-minute sessionsPart 2: One to two 45-minute sessionsParts 3 and 4: Two to three 45-minute sessionsParts 5 and 6: One to two 45-minute sessions (if time is short, these

parts can be deleted)

MaterialsA copy of the Briefing and Log for each studentWorld atlasesA current list of countries of the world and their populations. The World

Population Data Sheet, published annually by the Population Refer-ence Bureau, Inc., of Washington, D.C., is highly recommended:<http://www.prb.org>. Another source is the United Nations PopulationDivision at <http://www.undp.org/popin/wdtrends/p98/fp98.htm>.

Computer with CD-ROM. The Mission Geography CD-ROM contains colorgraphics that are required to explain the materials.

Optional: Access to the Internet, which offers opportunities for extendingthis investigation

Content PreviewA rapid decline in stratospheric ozone over the Antarctic (the Ozone Hole)was discovered in the 1970s. This discovery alarmed the scientific commu-nity because the stratospheric ozone layer protects Earth from the Sun’sdeadly ultraviolet radiation. The destruction of ozone was attributed to theuse of certain industrial chemical compounds, especially chlorofluorocar-bons (CFCs), which for decades have been used for refrigeration and asthe propellant in aerosol cans. This realization led to the signing of interna-tional agreements to cut back on CFC use and to seek substitutes forCFCs, but these agreements have not been universally honored. In the1990s, scientists began to observe significant losses of stratosphericozone over the Arctic. Since this region lies so close to very largeconcentrations of population, Arctic ozone loss poses a much more seriousthreat to humans than does Antarctic ozone loss.

Geography Standards

Standard 7: PhysicalSystems

The physical processes thatshape the patterns of Earth’ssurface

• Describe how physical processesaffect different regions of the

United States and the world.

Standard 10: HumanSystems

The characteristics, distribution,and complexity of Earth’s cul-tural mosaics

• Compare the role that culture playsin incidents of cooperation and

conflict in the present-day world.

Standard 14: Environmentand Society

How human actions modify thephysical environment

• Explain the global impacts ofhuman changes in the physical

environment.

Standard 15: Environmentand Society

How physical systems affecthuman systems

• Analyze examples of changes in thephysical environment that havereduced the capacity of the environ-

ment to support human activity.

Geography SkillsSkill Set 4: Analyzing GeographicInformation

• Use the processes of analysis,synthesis, evaluation, and explana-tion to interpret geographic informa-

tion from a variety of sources.

Module 3 Educator’s Guide Investigation 2

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International solutions are complicated by the fact thatthe rich, industrialized, high-latitude countries in theNorthern Hemisphere are more threatened than thepoor, less developed, low-latitude countries. Becausethe poor low-latitude countries have fewer incentives tobe concerned about the problem, they are more likelyto continue the manufacture and use of CFCs becausethey are cheaper than more advanced substitutes.Perhaps only the transfer of hundreds of millions ofdollars of technology from the rich high-latitude coun-tries to the poor low-latitude countries will be able tostop the manufacture and use of these chemicalcompounds. In any event, it will take many years forthe destructive compounds that are already in theatmosphere to disappear.

Classroom ProceduresBeginning the Investigation1. Distribute copies of the Briefing and the Log to each

student or, if you wish, to pairs (students can workthrough this investigation individually, but it is recom-mended that they work in pairs or small groups).• Leaf through these materials with students, and

call attention to the questions they shouldanswer in the Log.

• Point out the Glossary at the end of the Briefing.

2. Explain that all ozone is the same (O3, a gas

molecule with three oxygen atoms), but ozone is“good” in one place (the upper atmosphere orstratosphere), but “bad” in another place (loweratmosphere, called the troposphere, especially inthe air around cities).• Tell students that high ozone levels, which

contribute to air pollution in cities like LosAngeles, Denver, and Phoenix, is an interestinggeographic topic but one that is not the focus ofthis investigation.

• Instead, this investigation looks at the problemof the loss of ozone in the stratosphere.

3. Have students read (silently or aloud) the Back-ground and Objectives in the Briefing. Assistthem with any questions they may have, andinitiate a discussion about the problem. Forexample, ask students:• Have you heard of the hole in the ozone layer?• What do you know about it?• How does the loss of ozone affect life on Earth?• What parts of the Earth are likely to be most

affected?

Developing the Investigation4. Direct students to Part 1: What is NASA’s SOLVE

project? Students should work together to answerLog Questions 1-7, which are based on the tworeadings in the Briefing.• Table 1: Ozone time-line should help students

develop a historical perspective on this problem.• Have students use atlases to find the latitude and

longitude of Kiruna, Sweden (Log Question 1).

5. Part 2: What is the natural geography of ozone?requires careful study to answer Log Questions 8-13. (Although the material is not highly technical,you may wish to work with a science/chemistryeducator.)

• You should clarify that, although this “naturalgeography” deals with natural processes, theheart of this problem is that human influenceshave modified the natural geography.

• Use the eight steps below to help studentsunderstand how people have influenced thenatural geography of stratospheric ozone:

Step 1. Ozone-destroying chemicals, such aschlorine and bromine, are manufactured forindustrial purposes and are released by theactions of people. The release can come fromactions as innocent as replacing refrigerants ona car air conditioner or hauling an old refrigera-tor to a dump.

Step 2. These ozone destroyers float up throughthe lower atmosphere (troposphere) and into thestratosphere.

Step 3. The ozone-destroying chemicals floataround the stratosphere and reach the areasabove the North Pole and South Pole.

Step 4. Winter comes. There is no sunlight in apolar winter, which causes very low tempera-tures. A special type of cloud, a polar strato-spheric cloud, forms in the very cold air.


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Step 5. Polar stratospheric clouds change theozone-destroying chemicals into another chemi-cal during the long polar night during winter.This chemical is bad because when the sunlightstrikes it, chlorine is released. The polar strato-spheric clouds also lock away a natural agent(nitric acid) that protects ozone.

Step 6. When the spring comes (March over theNorth Pole, September over the South Pole),these dangerous forms of ozone-destroyingchemicals are touched by sunlight, whichreleases chlorine (Cl).

Step 7. Each atom of chlorine destroys approxi-mately 1,000 molecules of ozone! Eventually,the chlorine is neutralized by other chemicalreactions. But a lot of destruction occurs in ashort period of time each polar spring.

Step 8. The ozone-depleted air over the polesspreads towards the equator. For example, theAntarctic “ozone hole” in the stratosphere movestoward Argentina and Chile, New Zealand, andAustralia. The Arctic “ozone reduction” movestoward Alaska, Canada, northern Europe, andnorthern Asia.

• Point out to students that there are naturalprocesses that can destroy stratospheric ozone,including volcanoes and burning of plants. Acommon assumption among scientists is that thenatural processes of ozone destruction werebalanced by the natural processes of ozonecreation for the many years that humans did nothave refrigerators and air conditioning.

• Unfortunately, we do not have any record ofozone levels before the 1950s. The bestrecords are from the 1980s to today, as mea-sured by NASA satellites. These records showa great decline in stratospheric ozone each polarspring. And the decline gets worse each year.

• So we are left with a problem: we know that ourchemicals destroy ozone. We do not know ifthere were past natural changes that could alsocause this type of destruction.

• Some in industry argue that this uncertaintymeans that we should not act prematurely toban low-cost refrigeration systems and move tohigh-cost substitutes.

• Others argue that we can’t afford to wait. Weknow that it takes decades for the chlorine werelease today to destroy the ozone and fall outof the atmosphere.

6. Part 3 provides a partial list of effects of ozonedestruction.

• Direct class discussion of these effects and tostudents’ answers to Log Question 14: What doyou think are the two most serious effects ofstratospheric ozone depletion and why?

• Following the discussion, students should writetheir own answers to Question 14 in the Log.

7. Part 4: Where are the largest populations atrisk? asks students to estimate populations at riskfrom stratospheric ozone depletion. The purpose isto have students discover that the potential risk tohumans is much more serious in the Northern thanin the Southern Hemisphere.

• To complete Table 3 (Log Question 15), studentswill need world atlases, and you will need toprovide a recent list of countries and theirpopulations (see Materials/Resources). Alterna-tively, direct students to the library or Internet tofind this information.

• Estimation methods and assumptions are listedin the Briefing. These methods and assump-tions are arbitrary—they were designed only tofacilitate this student activity. Note that, follow-ing Table 3, students are asked to critique thesemethods and assumptions.

• The Log key to Table 3 lists only countries in theNorthern Hemisphere because no SouthernHemisphere countries qualify under the assump-tion that more than half of a country’s area mustlie at 50 degrees or more of latitude. Studentswill discover that, excluding uninhabited Antarc-tica, the only land area south of 50 degrees S isthe southern tip of South America—small parts ofArgentina and Chile that are virtually uninhabited.

Concluding the Investigation8. If time is short, the investigation can be concluded at

the end of Part 4. Students will have learned aboutthe physical and human processes contributing tothe depletion of stratospheric ozone, the potentialrisks to life, and the basic geographic dimensions ofthe problem. If you decide to conclude here, use theLog key to debrief student responses.


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9. Alternatively, it is recommended that you extendthe investigation by adding the important politicalgeographic perspective contained in Parts 5 and 6.

10. Have students read silently or aloud Parts 5 and 6.• You may want to download and print in advance

a copy of the Montreal Protocol, since studentsmay want to see the details of political arrange-ment. The Montreal Protocol can be found at<http://www.unep.org/mont_t.shtml>.

• To provide more information, you may wish tohave students access a web site giving up-to-date information on the status of the ozone layerat <http://jwocky.gsfc.nasa.gov/ozone/today.html>.

11. Put students into an even number of small groups,with three to five students in each.• These groups should prepare to make presenta-

tions at a meeting of the Executive Committee ofthe Multilateral Fund for the Montreal Protocol.

• The ECMF is the international body that wasestablished to help LDCs reduce their use ofozone-destroying chemicals.

• See 12 and 13, below.

12. Assign half of the small groups to role-play high-latitude, rich industrialized countries (MDCs), suchas Germany, United Kingdom, Sweden, Canada, orthe United States.• Encourage these groups to develop the posi-

tions and arguments they should make, basedupon their understanding of the geopolitics ofstratospheric ozone. If necessary, lead them tothe following:

• Groups playing the MDCs should prepare tosupport the position that lower latitude countriesshould work to avoid ozone destruction.

• Their goal should be to convince the low-latitudeLDCs that they should implement new restric-tions on the manufacturing and use of com-pounds that destroy stratospheric ozone.

13. Assign the other half of the small groups to role-play low-latitude poor developing countries (LDCs),such as India, China, Brazil, Indonesia, or Nigeria.• Encourage these groups to develop the posi-

tions and arguments they should make, basedupon their understanding of the geopolitics ofstratospheric ozone. If necessary, lead them tothe following:

• Groups playing the LDCs should prepare tosupport the position that lower latitude countriesshould not work to avoid ozone destruction.

• Their goal is to convince their fellow developingcountries to not rush too fast into new and expen-sive restrictions on the manufacturing and use ofcompounds that destroy stratospheric ozone.

14. Establish a time schedule for presentations byeach of the groups. You may wish to structurepresentations using a conventional debate format(e.g., with rebuttals, etc.) or simply allow each ofthe groups to have equal time to make theirarguments and offer their resolutions.

The following are points to look for from the LDCgroups:• The ozone layer is made in the stratosphere

over our low-latitude countries, and it is notbeing depleted over our countries.

• Developed nations want us to stop using theinexpensive chemicals that now go into ourrefrigerators and pesticides, but

• Who is going to pay for new refrigerators?• Who is going to give us a substitute for the

methyl bromide pesticide that has been so goodat increasing the yield of our crops?

• It is the rich industrialized countries that haveput most of the ozone-destroying chemicals intothe atmosphere.

• Unlike the poor low-latitude countries, the high-latitude countries have the wealth to cope withthe ozone problem.

• If the rich countries want the poor countries tostop using ozone-destroying chemicals, the richcountries should pay the poor countries for thenew chemicals and new equipment that wouldsubstitute for the old ozone-destroying com-pounds.

• In any event, the breakdown of the ozone layermay be occurring naturally. Science is notabsolutely certain on this point.

• So why make our people change from cheaprefrigerants and air conditioning until we learnmore about natural variability in the ozone layer?

• Low-latitude countries might put up a resolutionsuch as: Resolved: that we agree to ban themanufacturing and use of all ozone-destroyingchemicals when the high-latitude countriesagree to replace all facilities and machines thatproduce and use ozone-destroying chemicals.

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The following points could be made by the MDCgroups:• The ozone layer shields us from harmful ultra-

violet radiation.• The world’s use of ozone-destroying chemicals

is the main cause of stratospheric ozone deple-tion.

• Ozone depletion is taking place over the high-latitude countries; thus, it is life in these coun-tries that faces the greatest threat from in-creased UV radiation.

• Earth’s ozone layer has existed for billions ofyears in a balance between natural breakdownand natural creation.

• We can’t afford to take the chance that recentlyobserved ozone changes are nothing more thannatural variability. If we wait to take action tostop the use of ozone-destroying compounds, itwill take decades for the chlorine we make todayto fall out of the stratosphere.

• An example of a resolution that might be offeredby a rich, high-latitude country is: Resolved: thatwe agree to crack down on the illegal use ofozone-destroying chemicals.

15. Debrief the presentations by having studentscritique the arguments and resolutions made by thesmall groups.

EvaluationLog1. The latitude and longitude of Kiruna, Sweden, is

67.49°N and 20.08°E.

2. Complete this sentence: The purpose of theSOLVE project is to:Understand exactly why so much ozone disap-pears above the North Pole in winter and when thatozone layer might recover.

3. What is the significance of the stratospheric ozonelayer to life on Earth?The ozone layer of the atmosphere protects Earthbelow from ultraviolet radiation from the Sun. Toomuch UV radiation reaching the planet’s surfacecan burn skin, cause cataracts, kill living cells, andharm crops.

4. Complete this sentence: The major observation ofthe SOLVE project during the winter of 1999-2000was that:In some parts of the Arctic stratosphere—locatedfrom about 16 kilometers to 48 kilometers aboveEarth—ozone concentrations declined as much as 60percent from November 1999 through March 2000.

5. Complete this sentence: According to SOLVEproject scientists, the significant decline in ozoneover the Arctic in the winter of 1999-2000 wascaused by:An increase in the area and longevity of polarstratospheric clouds (PSCs).

6. What are polar stratospheric clouds (PSCs)?PSCs, which are made up of ice and nitric acid,form about 21 kilometers (13 miles) above thepoles where winter temperatures can drop to -93°C(-110°F) and below.

7. What is the role of PSCs in the destruction ofstratospheric ozone?PSCs are hosts to the chemical reactions thatdestroy ozone. Chlorine and bromine atoms in thestratosphere attach to the ice crystals of the PSCs.Sunlight on the PSCs in late winter and early springcauses reactions that change these atoms into aform that destroys ozone. One chlorine or bromineatom can destroy thousands of ozone molecules.

8. According to Figure 2, where has the most strato-spheric ozone been depleted, over the Arctic orAntarctic?Antarctic

9. Where are the lowest temperatures, over the Arcticor Antarctic?Antarctic

10. Where would you expect to find the most andlongest lasting PSCs, over the Arctic or Antarctic?Antarctic

11. Explain your answer to Question 10.The coldest temperatures are over the Antarctic,and so the most and longest lasting PSCs will formwhere the temperatures are the coldest.

12. In which hemisphere, the Northern or Southern,would stratospheric ozone depletion affect the mostpeople?The Northern Hemisphere

13. Explain your answer to Question 12.The Northern Hemisphere has much larger popula-tions at high latitudes than does the Southern Hemi-sphere, so one would expect Arctic ozone depletionto affect more people than Antarctic depletion.


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14. What do you think are the two most serious effectsof stratospheric ozone depletion and why?Since this question asks for an opinion, there is noone correct answer. However, a useful discussioncan be based on student opinions. Possibleanswers include:• increases in skin cancers, cataracts and blind-

ness, and infections; and• decreases in life in northern lakes, food produc-

tion, tree growth, and ocean phytoplankton thatmake oxygen.

15. Complete Table 3 and write your critique in thespace provided below.

Table 3: Estimated populations at riskfrom stratospheric ozone depletion in theNorthern Hemisphere a

a. Populations at risk are assumed to lie at 50 degrees or more oflatitude.b. These estimates come from the following rule: Countries listedhave more than half of their areas lying at more than 50 degrees.For example, less than half of France but more than half of Germanylie north of 50 degrees. Thus, France should not be listed, butGermany should be. Population numbers come from PopulationReference Bureau. 2000 World Population Data Sheet. Washington,D.C.: Population Reference Bureau, http://www.prb.org.NOTE: No Southern Hemisphere countries qualify for inclusionunder the above criteria.

In the space below, critique the above method ofestimating and describe what you think might be amore accurate method.In their critiques, students might make the followingpoints:

• The 50 degrees or higher assumption is arbi-trary: Ozone depletion may affect countries andareas lower in latitude than 50 degrees, depend-ing upon variations in atmospheric circulation.

• The assumption that populations are distributedevenly over a country’s area is hard to defend,given that populations are typically clustered intourban areas; also population density variesregionally within a country. Population estima-tion would be more accurate if it were based onthe actual distribution of populations.


Countryb Population (millions)Russia 145.2Germany 82.1United Kingdom 59.8Poland 38.6Canada 30.8Netherlands 15.9Belgium 10.2Belarus 10.0Sweden 8.9Denmark 5.3Finland 5.2Norway 4.5Ireland 3.8Lithuania 3.7Latvia 2.4Estonia 1.4Iceland 0.3TOTAL 428.1

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BackgroundHave you heard of the ozone hole? In the 1970s,scientists began noticing a hole developing in thestratospheric ozone layer high above Antarctica.Scientists attributed the ozone destruction to humanaction. This alarmed them because the ozone layerprotects Earth against harmful amounts of ultravioletradiation. Life on Earth could be threatened if toomuch ozone is destroyed. The Antarctic ozone holeputs the health of populations in the SouthernHemisphere at risk. In 1986, a similar hole wasidentified over the Arctic Ocean, which meant thatthe much larger populations in the Northern Hemi-sphere might be at risk. Observations by the NASASOLVE project showed a decline in Arctic ozone inthe winter of 1999-2000. How were these discover-ies made? What human actions are to blame?What are the risks to human populations? Howmany lives are at risk? Will countries cooperate tohalt ozone destruction? These are some of thequestions raised in this investigation.

ObjectivesIn this investigation, you will• learn how, where, and why stratospheric ozone

is made and destroyed;• learn about the effects of the loss of strato-

spheric ozone;• estimate the size of the populations at risk from

ozone depletion; and• learn why there is an international debate about

the problem of stratospheric ozone.

Part 1: What is NASA’s SOLVE project?

To answer this question, study the following tworeadings, a newspaper article and a NASA newsrelease, and answer Questions 1-7 on the Log.

PROJECT SEEKS KEYS TO OZONEHOLE, REGROWTH

By Katy Human

More than 300 scientists from around the

world spent most of December 1999 in Kiruna,Sweden, collecting data for a scientific missioncalled SOLVE.

This $17 million NASA project has an ambitious

Module 3, Investigation 2: BriefingThe loss of stratospheric ozone: Where are lives at risk?

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goal: to understand exactly why so much ozone[words in bold print are defined in the glossary atthe end of this investigation] disappears abovethe North Pole in winter, and when that ozonelayer might recover.

They’re flying airplanes high into the atmosphereto collect data, sending up balloons bearinginstruments, and collecting data from ground-based devices.

The chemical, ozone, is vital for life. The ozonelayer of the atmosphere protects the Earth belowfrom ultraviolet radiation. UV radiation, when itreaches the planet’s surface, burns skin, causescataracts, and can kill a living cell and harmcrops.

“UV radiation is the bad boy in the whole storyhere,” said Paul Newman, an atmosphericphysicist at NASA’s Goddard Space Flight Centerin Greenbelt, Maryland, and a SOLVE scientist.Newman said, “And because ozone screens UVradiation, we have to understand how ozonemight change in the future and what affects ittoday.”

A better understanding of ozone layer dynamicscould also help industry design products moreintelligently.

“If we create a new chemical, what’s the impacton ozone?” Newman asked. “If we fly airplaneshigher into the stratosphere, what’s the effect ofthat?”

In Kiruna, David Fahey, an atmospheric re-searcher with NOAA, said “winter is taken veryseriously up here.” He and his colleagues havelong taken winter seriously, because that’s whenthe chilly air above the poles sets the scene forozone destruction.

Winter winds keep a vortex of cold air trappedabove the North Pole, creating a virtual cauldronin which all the ingredients essential to ozonedestruction can mix. Chlorine and bromine, withnumerous industrial uses, are among the mostimportant.

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“One chlorine atom in the stratosphere candestroy thousands of ozone molecules. Bromineis even more effective,” said Rick Shetter, anatmospheric scientist from the National Center forAtmospheric Research in Boulder, Colorado.

Industries once used chlorine- and bromine-containing chemicals almost indiscriminately,because no one knew what they might do to theatmosphere. But in the 1980s, researchersrealized that the pollutants not only destroyozone, they have a long life span in the strato-sphere, once they drifted there. They mightwreak havoc on ozone for decades, even ifindustry were to shift immediately to alternativechemicals. [See Table 1 for a timeline of ozonedevelopments.]

In 1997, the United States signed the MontrealProtocol on Substances that Deplete the Ozone.Many nations have phased out and eveneliminated the use of chemicals that destroy theozone layer. [See Table 2 for a list of ozone-destroying chemicals.]

But Fahey says ozone is still in danger. “Theactive agent, the perpetrator, has been con-tained, but that doesn’t mean ozone has recov-ered,” he said. “It’s like a fire: First you keep itfrom spreading, but then you have to wait for it toburn itself out.” It’ll be at least 2050 before theseverely depleted Antarctic’s ozone layer returnsto its 1980 thickness, Fahey estimated.

Table 1: Ozone time-line

1928• Thomas Midgely produced a chemical compound called

CFC-12 (dichlorodifluoromethane) to serve as a replace-ment for the highly toxic and flammable refrigerants suchas ammonia.

1930s• Dupont and General Motors began to market CFCs under

the trade name Freon. Since then, other CFCs have beensynthesized and produced in large quantities. CFCs havebeen extensively used in refrigerators and as propellantsin aerosol cans.

1960s• Recognition that O3

was naturally low over Antarctic.

1970s• Discovery of curious “hole” in ozone layer over Antarctica,

a seasonal thinning of the layer occurring in early spring,reaching a minimum in October.

• United States issues ban on CFCs.1980s• Studies of SOL (stratospheric ozone layer) indicated

substantial decline in total global ozone—8 percentdecline from 1979-1987.

• Landmark paper in Nature by Farman, Gardiner, andShanklin of the British Antarctic Survey showed that O3

was disappearing over Antarctic during the southernhemisphere spring.

• Vienna Conference convened by United Nations Environ-ment Programme (UNEP)—43 countries brought forth theVienna Convention for the Protection of the Ozone Layer.

• Corresponding to the Antarctic hole, a hole was identifiedover the Arctic Ocean in February (maximum thinning at bothpoles matches the time of lowest surface temperatures).

• Scientists agreed that a serious and persistent globaldecrease was in progress at a rate far faster than whathad been previously predicted.

• Twenty-three countries endorsed the UNEP plan forcutting global CFC consumption by 50 percent by 1999.

• In an agreement known as the Montreal Protocol, theUnited States joined 31 other countries in approving asimilar goal.

• Airborne Arctic Stratospheric Expedition (AASE-I) foundhigh concentrations of chlorine monoxide inside the Arcticvortex, suggesting that significant ozone depletion couldoccur during the Arctic spring. Several studies calculatedand deduced ozone losses based on these observations.

1990s• Slight increase in UVR—about 1 percent/year over

preceding 8 years—had been documented at anobserving station in the Swiss Alps at an altitude of3600 meters (12,000 feet).

• Montreal Protocol was expanded and strengthened to agoal of 50 percent reduction of CFCs by 1995 and85 percent by 1997.

• With the Upper Atmosphere Research Satellite (UARS),the AASE-II, and the European Arctic Stratospheric OzoneExperiment (EASOE), the Arctic winter of 1991-1992 wasstudied extensively. A number of researchers deducedvarious ozone loss rates inside the Arctic vortex.

• 1995-1996 was the first winter to show very large ozonelosses and a polar ozone low in the Arctic that was verysimilar to the one observed over Antarctica each year.

• March 1997 Arctic ozone amounts were the lowest onrecord for the previous 20 years of observations.

• United States signed the Montreal Protocol on Sub-

stances that Deplete the Ozone.

2000s• NASA’s SOLVE project finds a significant decline in

stratospheric ozone over the Arctic caused by an increase inthe area and duration of polar stratospheric clouds (PSCs).

• Next global ozone report scheduled for 2002: UNEPpublishes ozone report every four years.

• 2050 is the year it is estimated that the severely depletedAntarctic ozone layer will return to its 1980 thickness.


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SOLVE researchers are not only trying to putnumbers on all the chemical reactions that leadto ozone depletion; they’re also trying to under-stand a dangerous new player in the ozonedepletion game up north.

In recent years, though the Earth’s surfaceappears to have warmed slightly, the strato-sphere has cooled. Those cold temperatures leta particular type of cloud form—polar strato-spheric clouds. These clouds are host to thechemical reactions that deplete ozone. [Human,Katy. 2000. [Boulder, CO] Daily Camera, Jan.

29, pp. 1A, 4A.]

ARCTIC OZONE DEPLETION LINKED TOLONGEVITY OF POLAR STRATOSPHERIC

CLOUDSNASA Press Release 00-43, May 30, 2000

A significant decline in ozone over the Arctic lastwinter was due to an increase in the area andlongevity of polar stratospheric clouds (PSCs),according to a group of researchers who partici-pated in a large, international atmosphericscience campaign.

The ozone-destroying clouds are made of ice andnitric acid, said University of Colorado atBoulder Professor Owen B. Toon, one of fiveproject scientists heading up NASA’s SAGE IIIOzone Loss and Validation Experiment, orSOLVE. The massive SOLVE project involvedsatellites, aircraft, balloons and ground-basedinstruments operated from December 1999through March 2000 by more than 200 scientistsand support staff from the United States, Canada,Europe, Russia, and Japan.

“Even very small numbers of particles in PSCscan efficiently remove nitrogen from the strato-sphere,” said Eric Jensen, a scientist at NASAAmes Research Center, located in California’sSilicon Valley. “We found that the clouds lastedlonger during the 1999-2000 winter than duringpast winters, allowing greater ozone depletionover the Arctic.”

“Polar stratospheric clouds generally form about13 miles above the poles where temperaturescan drop to minus 110 degrees Fahrenheit andbelow,” said Toon. The SOLVE campaign wasstaged out of Kiruna, Sweden.

In some parts of the Arctic stratosphere—which islocated from about 10 miles to 30 miles aboveEarth—ozone concentrations declined as muchas 60 percent from November 1999 throughMarch 2000. The fragile stratospheric ozonelayer shields life on Earth from the harmful effectsof ultraviolet radiation.

Although seasonal ozone loss is more severe inthe Antarctic, the ozone loss in the Arctic pre-sents potentially more serious health problems tohuman beings, said Toon. Ozone-depleted airfrom the Arctic drifts south toward North America,Europe, and Russia each spring, increasing theamounts of ultraviolet light reaching Earth’ssurface in the highly populated mid-latitudes andpotentially causing increases in several types ofcancer.

Most chlorine compounds pumped into Earth’satmosphere in recent decades by human activityinitially were tied up as chlorine nitrate orhydrochloric acid, both of which are nonreactive.But if there is a surface area to attach to, like thepolar stratospheric cloud ice crystals, the chlorinecompounds change into ozone-gobbling chlorineradicals in late winter and early spring afterreacting with sunlight.

The greenhouse effect, which warms Earth nearits surface, may ironically be cooling the strato-sphere enough to cause these clouds to formearlier and persist longer. Greenhouse gases areradiating energy and heat away from the upperstratosphere, creating prime conditions for polarstratospheric cloud formation.

“With the clouds persisting longer, we are seeinggreater ozone losses even though the amount ofchlorine in the atmosphere has declined slightly,”said Toon. Manufacture of chlorofluorocarbons[CFCs] ceased in 1996 in signatory countriesunder the terms of the Montreal Protocol and its

amendments (NASA 2000).


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Ozone-destroying chemicals that contain chlorineand bromine are released by the action of people.The release can come from actions as innocent asreplacing refrigerants in a car air conditioner orhauling an old refrigerator to a dump (Table 2).

Part 2. What is the natural geography ofozone?

Is ozone good or bad? The answer to that questionis fundamentally geographic: It depends on where itis. Ozone is the same molecule (O

3 or 3 oxygens)

no matter where it is found, but we don’t like the“bad ozone” in the lower atmosphere (tropo-sphere), and we are worried about the loss of “goodozone” in the upper atmosphere (stratosphere).

• The ozone close to the surface (in the tropo-sphere) causes air pollution in our cities. Ozoneair pollution is harmful to our health.

• But the stratospheric ozone is good. Strato-spheric ozone absorbs a lot of the harmfulultraviolet solar radiation. Without stratosphericozone, life as we know it would not be possibleon Earth.

There are three keys to understanding the naturalgeography of stratospheric ozone (Figure 1):

1. The oxygen that we breath (O2) is hit by the

intense sunlight in the tropics, including theintense ultraviolet radiation.

2. The ultraviolet sunlight in the stratosphere (10-50 kilometers above the surface) hitting the O

2

makes O3 over the tropics.

3. The O3 surplus over the tropics is moved all

over the planet by winds to provide a globalozone layer.


Table 2: Ozone-destroying chemicals

Chemicals Uses and Sources

Chlorofluorocarbons(CFCs)

Halons

Methyl bromide

Sulfate aerosols

Methyl chloride

Refrigerators, airconditioners, aerosolsprays, fire extin-guishers

Fire suppression

Pesticide and naturalocean release

From natural volca-noes

From natural andhuman-made savannafires

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Use Figure 2 to find outhow the geography ofthe ozone layer over theAntarctic and Arctic haschanged in the last twodecades.

Answer Questions 8-13on the Log.

You can see howimportant ozone is byexamining the tempera-ture curve on the rightof Figure 1. In thetroposphere, the sourceof heat comes onlyindirectly from the Sun.The Sun first heats upEarth, and then Earthheats up the tropo-sphere. So the fartheryou go from Earth, thecolder it gets. Tempera-tures rise in the strato-sphere because theozone layer absorbsharmful ultravioletradiation. The processof absorbing the ultra-violet radiation heats upthe stratosphere.

Figure 2: Polar ozone depletion over an 18-year period asmeasured by NASA’s Total Ozone Mapping Spectrometer(TOMS). Red indicates high-ozone amounts; blue indicateslow ozone.

Source: http://eos-chem.gsfc.nasa.gov/science.html


Figure 1: Ozone is produced over the tropics in the stratosphere. Windsthen distribute the ozone to higher latitudes.

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If you’re thinking that ozone destruction in the highlatitudes relates to the fact that it’s cold near thepoles, you’re absolutely right! During the SouthernHemisphere’s winter, air can reach temperaturescolder than -90°C near the South Pole. In theNorthern Hemisphere winter, the lowest tempera-tures reach about -65°C. As a result of the intensecold, a circular current of strong winds (called avortex) surrounds each pole in the winter. Thevortex around Antarctica is much stronger than thevortex around the Arctic. The vortex helps create a“witches brew” of ozone-destroying compounds.

Keep in mind that there is no sunlight reaching thepolar latitudes in the winter. So, of course, it’s goingto be cold. The very cold temperatures help formpolar stratospheric clouds (PSCs) (Figure 3).

The Northern Hemisphere has not seen as muchseasonal ozone destruction as has been experi-enced over Antarctica. This is because the Arcticdoes not have the extremely cold temperatures

Figure 3: Polar stratospheric clouds(PSCs) are seen above Stavanger, Norway

This photograph was taken from the NASA DC-8 flyinglaboratory at nearly 39,000 feet on February 28, 1989. Thelower polar stratospheric clouds (seen edge-on as a thin, darkorange or brown layer) are made up of nitrogen compounds,including nitric acid. Multiple layering can be seen. The whiterclouds consist mostly of frozen water molecules.

Source: http://ails.arc.nasa.gov/Images/EarthSci/AC89-0114-605.html

Figure 4: Thespringtimedecline in ozoneconcentrationsover the Arcticand adjacenthigh-latitudecountries

The red and orangeindicate high ozonevalues, which have beenslowly getting less sinceat least 1979—whenNASA started gatheringdata. There isn’t aconsistent decline inozone levels over theArctic because somewinters are not coldenough to form polarstratospheric clouds(PSCs).

Source: http://jwocky.gsfc.nasa.gov/multi/TOMSmarch79_98.gif


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needed to form polar stratospheric clouds eachyear. Intense PSC formation occurs only in someyears over the Arctic, leading to destruction ofozone but much less than over Antarctica. NASA’sTOMS satellite has kept track of ozone concentra-tions over North America since 1979 (Figure 4).What trends do you see in Figure 4?

Part 3: What are the effects of ozonedestruction?

The problem of stratospheric ozone destruction inthe tropics is minimal. Although some ozone-destroying chemicals are manufactured in thetropics, ozone depletion is least there. Even thoughthere is a lot of solar radiation hitting the tropics,tropical plants and animals are adapted to it.

Almost all of the effects of ozone depletion are at highlatitudes. Since plants and animals at these highlatitudes have adapted to only low levels of ultravioletradiation, a large increase could be potentiallydangerous. Here are some worrisome points.

• Information from NASA’s Total Ozone MappingSatellite (TOMS) indicates spring and summerultraviolet radiation has increased 5 percent perdecade at 45°N, 7 percent at 55°N, and 10 per-cent per decade at 55°S. The ability of ultravioletradiation to damage DNA increases 2.5 percentfor each 1 percent reduction in ozone. Increasesin skin cancers, nonmelanoma for example, areestimated to have increased from 3 percent atlow latitudes to 39 percent at 55°S.

• People of fair skin are generally more prone toskin cancer. Today, in the United States, morethan 50 percent of new cancers are skin can-cers. Skin cancer is now the fastest growingtype of cancer among men and the third fastestamong women.

• Medical researchers think that increases inultraviolet radiation reduce effectiveness of thehuman immune system, which increasessusceptibility to infections.

• Higher ultraviolet concentrations can lead tocataracts and eventually blindness. The UnitedNations Environment Program (UNEP) estimatesthat a 1 percent decrease in ozone can lead tocataracts in an additional 100,000 people.

• Northern lakes in areas formerly glaciated (suchas Canada and Scandinavia) are affected bysmall increases in ultraviolet radiation, with thedownward migration of zooplankton and reduc-tion in chlorophyll, causing complications in thefood chain in these lakes.

• Some agricultural plants appear to be sensitiveto increases in ultraviolet radiation, particularlybarley, broccoli, carrots, cauliflower, cucumbers,oats, peas, soybeans, sweet corn, and toma-toes. For every 1 percent increase in ultravioletradiation, food production decreases 1 percent.

• About 45 percent of tree species appear to besensitive to ultraviolet increases.

• Today, ultraviolet radiation is penetrating todepths in the ocean never previously seen.Phytoplankton grow just below the oceansurface and do not benefit much from thenatural blocking effect of ultraviolet radiation bywater. Phytoplankton in the ocean absorbcarbon dioxide, produce oxygen, producecompounds that help clouds form, and are thefoundation of the ocean food chain. In the areaaround the Antarctic ozone hole, there hasbeen a 6-12 percent decrease in phytoplanktonproductivity in the spring, when the ozone holeappears. When averaged out over the entireyear, the decrease is 2 percent. The long-termeffects of such a decline in phytoplanktonproductivity are uncertain.

Answer Question 14 on the Log.


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Part 4: Where are the largest populationsat risk?

The ozone-depleted air over the poles spreadstoward the equator. For example, the Antarctic“ozone hole” in the stratosphere moves towardArgentina, New Zealand, and Australia. The Arctic“ozone reduction” moves toward Canada, thenorthern United States, northern Europe, andnorthern Asia. Where are the largest populationsat risk?

You have read that PSCs have been photographedabove Kiruna, Sweden (68°N), and Stavanger,Norway (58°N). These are obviously high-latitudeplaces. Since PSCs form in the coldest air, whichis found near the poles, we can assume thatpopulations at the highest latitudes face thegreatest risk from ozone depletion.

It is your job to estimate which populations aremost at risk:

• Let us assume that human populations at riskfrom stratospheric ozone depletion lie at lati-tudes of 50 degrees or more.

• Use an atlas and a recent listing of populationsof countries to estimate the size of the popula-tions at risk in the northern and the southernhemispheres.

• Use the following rule to make your estimate:List only those countries with more than half oftheir areas lying at more than 50 degrees oflatitude.

• On the Log, complete the table listing thecountries and their populations that are at riskaccording to the estimation method describedabove.

Answer Question 15 on the Log.

Part 5: What are the geopolitics of ozone?

Because scientists convinced politicians about thedangers of the Antarctic ozone hole, an interna-tional agreement called the Montreal Protocol wasreached. Countries that signed agreed to stopusing ozone-destroying chemicals.

A copy of the Montreal Protocol can be found onthe Internet at: <http://www.unep.org/unep/secretar/ozone/mont_t.shtml>.

Following the Montreal Protocol, the United States,Canada, Germany, and other more developedcountries (MDCs) have begun to use substitutesfor CFCs that are less harmful to the ozone layer.On the positive side, there are signs that human-made ozone-destroying chemicals may be startingto decrease in the atmosphere.

On the other hand, the problem of ozone destruc-tion has not gone away because

1) Ozone-destroying chemicals stay up in thestratosphere for decades,

2) Some countries that signed the agreementstill produce and use ozone-destroyingchemicals, and

3) Some countries still have not signed theagreement.

So the world is faced with a geographical irony:

• Most of the countries still using ozone-destroyingchemicals are found in the lower latitudes. Theseare less-developed countries (LDCs), such asIndia and China. This is because CFCs and otherozone-destroying chemicals are cheaper toproduce and can be used in their equipment.


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• Most of the countries affected by the loss ofozone are found in the higher latitudes— MDCs,such as Canada, the United Kingdom, andGermany. All of these countries signed theMontreal Protocol and have made progress instopping the use of ozone-destroying chemicals.

In 1986, LDCs accounted for only 15 percent of thetotal usage of ozone-depleting substances. But by1991, this figure jumped to 21 percent. Chinaalone increased use 20 percent per year in the1980s, as refrigeration increased dramatically. By1996, China produced 60,000 tons of CFCs, India20,000 tons, Russia 18,000 tons, and the rest ofthe world 52,000 tons.

In 1987, the Montreal Protocol called for theworldwide elimination or reduction of ozone-destroying substances. The protocol has beenupdated several times as understanding of theozone problem increased. The Montreal Protocolhas been signed by more than 160 nations.

MDCs at first did not want to freely transfer newtechnology using ozone-friendly chemicals be-cause companies in the MDCs did not want to loseprofits. LDCs argued that they weren’t responsiblefor the problem and they shouldn’t have to pay.

A Multilateral Fund, created mainly by MDCs, wasestablished by the Montreal Protocol to help LDCsmeet the protocol.

The future is not at all certain because it is farcheaper to use ozone-depleting chemicals thansubstitutes. The rest of this section explains someproblems the Executive Committee of the Multilat-eral Fund faces.

• The Montreal Protocol allows MDCs such as theUnited States to export ozone-depleting com-pounds to LDCs. But LDCs cannot export thesecompounds to MDCs. The justification is thatreplacing old refrigeration technology usingozone-destroying compounds would have beenenormously expensive. Thus, LDCs who signedthe protocol were given a 10-year grace periodto phase out ozone-destroying chemicals.

• But China and India will continue to produce anduse CFCs legally for the first decade of the 21stcentury. Also, there is speculation that illegalproduction will continue in these countries forsome time to come.

• There are also problems with new substitutesbecause several substitutes themselves destroythe ozone layer. Because the chemical industryis constantly creating new products, manycountries are worried that new ozone-depletingchemicals could be made and sold.

• A major concern among MDCs is that LDCssimply have no ability or will to enforce theprovisions of the Montreal Protocol.

Part 6: A geopolitical confrontation?

You now know the basics. Science can explainwhere and how ozone destruction occurs, butscience alone cannot solve the problem. This isbecause ozone destruction occurs in the highlatitudes, not in the low latitudes where futureozone-destroying chemicals will be manufacturedand released by LDCs. And the high-latitude MDCssuffering from problems have already movedtowards substitutes for ozone-destroying chemicals.

The Montreal Protocol was intended to help reducethe manufacture of ozone-destroying chemicals,but not all countries have signed the agreement.Also, the Montreal Protocol specifies that higherlatitude MDCs give aid through the MultilateralFund to help poorer nations make the transition tosubstitutes. But because CFCs are far cheaperthan substitutes, ozone-depleting chemicals arestill made and used in vast quantities.

Thus, the stage is set for an unusual geopoliticalconfrontation. The LDCs are in control of the healthof the world’s ozone layer. These countries aretrying to industrialize, using ozone-destroyingrefrigeration for food preservation and comfort.China and other LDCs are still using ozone-destroying refrigerants. Thus, the poorer countriesin the lower latitudes have the power over rich,industrialized countries (MDCs) in the higher


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latitudes where the effects of ozone destruction willbe most pronounced.

Can the LDCs be convinced to make changes tosave the ozone layer above the MDCs? Or should

the LDCs put their priorities on their own devel-opment and let the MDCs use their wealth to tryto cope with ozone depletion in the higherlatitudes? Resolving these questions will requireworldwide commitment and agreement.


References

Human, Katy. 2000. [Boulder, CO] Daily Camera.Jan. 29, pp. 1A, 4A.

NASA. 2000. Arctic ozone depletion linked tolongevity of polar stratospheric clouds. NASAPress release 00-43, NASA Ames ResearchCenter, Moffett Field, California, May 30, 2000.

Population Reference Bureau. 2000. 2000 Worldpopulation data sheet. Washington, D.C.:Population Reference Bureau. http://www.prb.org

GLOSSARY

aerosols: tiny dust-sized particles in the atmosphere.

bromine: an element that destroys stratospheric ozone.Bromine is included in the compound methyl bromide.Methyl bromide is used as a pesticide, and it is alsomade naturally by oceans.

chlorine: an element that destroys stratospheric ozone.Chlorine is included in chlorofluorocarbons.

chlorofluorocarbons (CFCs): compounds containingchlorine, fluorine, and carbon. CFCs are used inrefrigerators and air conditioners. The term is sometimesused to include chlorocarbons, fluorocarbons, andhydrochlorofluorocarbons.

halons: chemicals similar to CFCs but containing bromine.Used for fire suppression.

LDCs: less-developed countries, sometimes called develop-ing countries. These are the poorer, least industrializedcountries.

MDCs: more-developed countries, sometimes calleddeveloped countries. These are the more wealthy,industrialized countries.

nitric acid: a natural compound (HNO3) in the stratosphere

that protects the ozone layer.

nitrogen: an element and a gas that makes up 77 percent ofEarth’s atmosphere. Nitrogen is important in protectingthe ozone layer when it exists in the form of nitricacids—that is, until polar stratospheric clouds (PSCs)get involved. The PSCs remove nitric acids and allowozone destruction.

ozone: a form of oxygen molecule containing three (O3) atoms

of oxygen, rather than two oxygen atoms.

phytoplankton: small, floating plants, such as algae, living inwater; they form the bottom of the oceanic food chain.

polar stratospheric clouds (PSCs): clouds in the strato-sphere that only form when the stratosphere is very, verycold—in the dead of the polar winter. Polar stratosphericclouds remove ozone’s natural guardian (nitric acid).

stratosphere: the layer of the atmosphere immediately abovethe troposphere. Temperatures increase with altitudewithin the stratosphere.

sulfates: compounds that include sulfur and oxygen. Sulfatesoccur in the atmosphere as tiny dust-sized particlescalled aerosols. Sulfate aerosols are released by sometypes of volcanic eruptions. When these volcaniceruptions are very violent, the sulfate aerosols can bethrown into the stratosphere and help destroy ozone.

troposphere: the lowest layer of the atmosphere. Almost allweather occurs in this layer. Its average thickness is11 kilometers (7 miles).

ultraviolet radiation: solar radiation with wavelengths lessthan that of visible light. Ultraviolet sunlight has a lot ofenergy and damages cells in animals and plants.

vortex: intense circular wind flow; a vortex forms in the winterover the poles—and is sometimes called a “circumpolarvortex.”

http://george.arc.nasa.gov/dx/basket/pix/pscpix/PSCcloudcaps/PSCpix.html

http://eos-chem.gsfc.nasa.gov/science.htmlhttp://ails.arc.nasa.gov/Images/EarthSci/AC89-

0114-605.htmlhttp://jwocky.gsfc.nasa.gov/multi/

TOMSmarch79_98.gifhttp://www.unep.org/mont_t.shtml

17

1. The latitude and longitude of Kiruna, Sweden, is degrees minutes anddegrees minutes.

2. Complete this sentence: The purpose of the SOLVE project is to

3. What is the significance of the stratospheric ozone layer to life on Earth?

4. Complete this sentence: The major observation of the SOLVE project during the winter of 1999-2000was that

5. Complete this sentence: According to SOLVE project scientists, the significant decline in ozone overthe Arctic in the winter of 1999-2000 was caused by

6. What are polar stratospheric clouds (PSCs)?

7. What is the role of PSCs in the destruction of stratospheric ozone?

11

Module 3, Investigation 2: LogThe loss of stratospheric ozone: Where are lives at risk?

18

8. According to Figure 2, where has the most stratospheric ozone been depleted, over the Arctic orAntarctic?

9. Where are the lowest temperatures, over the Arctic or Antarctic?

10. Where would you expect to find the most and longest lasting PSCs, over the Arctic or Antarctic?

11. Explain your answer to Question 10.

12. In which hemisphere, the Northern or Southern, would stratospheric ozone depletion affect the mostpeople?

13. Explain your answer to Question 12.

14. What do you think are the two most serious effects of stratospheric ozone depletion and why?

12


1)

2)

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15. Complete Table 3 and write your critique in the space provided below.

Table 3: Estimated populations at risk from stratospheric ozone depletion a

a Populations at risk are assumed to lie at 50 degrees or more of latitude.b These estimates come from the following rule: countries listed have more than half of their areas lying at more than 50 degrees.For example, less than half of France but more than half of Germany lie north of 50 degrees. Thus, France should not be listed butGermany should be. Population numbers come from Population Reference Bureau 2000, http://www.prb.org

In the space below, critique the above method of estimating and describe what you think might be a moreaccurate method.


Countryb Population (millions)

Russia 145.2

Total

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