LINKAGES BETWEEN CLIMATE CHANGE AND STRATOSPHERIC OZONE DEPLETION
ROBERT C. WORREST,* KATIE D, SMYTHE,** ALEXANDER M. TAIT**
*U.S, Environmental Protection Agency, Office of Research and Development,
Washington, DC;
**Science and Policy Associates, Washington, DC
INTRODUCTION
Alterations of the earth's atmosphere by human activities are now of regional
and global proportion. In the last decade scientists, policy makers, and the
general public have focused increasing concern on ozone depletion in the upper
atmosphere and on global climate change. These two problems are closely
interrelated and both are of truly global scale. Two primary areas link the
issue of stratospheric ozone depletion to global climate change: atmospheric
processes and ecological processes.
Atmospheric processes establish a linkage through the dual roles of certain
trace gases in promoting global warming and in depleting the ozone layer. The
primary radiatively active trace gases are carbon dioxide, nitrous oxide,
chlorofluorocarbons, methane, and tropospheric ozone. In the troposphere, the
atmosphere up to 10 miles above the earth's surface, these compounds function as
greenhouse gases. At increased levels they can contribute to global climate
change. Many of these gases also influence the concentration of ozone in the
stratosphere, the atmospheric layer located between 10-30 miles above the earth's
surface. This diffuse layer of ozone in the stratosphere protects life on earth
from harmful solar radiation. A reduction of this layer could have very
important impacts on the earth's systems.
The second mode of interaction revolves around various ecological processes.
Physical, chemical, and biological activities of plants and animals are affected
directly by global climate change and by increased ultraviolet radiation
resulting from depletion of stratospheric ozone.
The purposes of this paper are to: 1) provide general background on the
stratospheric ozone depletion issue, and 2) discuss the linkages surrounding both
the atmospheric and ecological processes.
BACKGROUND
The natural distribution of ozone in the earth's atmosphere is not uniform.
It is concentrated primarily in a thin layer in the stratosphere where it blocks
most of the ultraviolet radiation in the 290 to 320 nm range from reaching the
earth's surface. This is known as the ultraviolet-B (or UV-B) range and it can
be damaging to humans, biological organisms, and man-made materials.
Many gases emitted from man's industrial and agricultural activities can
accumulate in the earth's atmosphere and ultimately contribute to alterations in
the vertical distribution of stratospheric ozone. These gases accumulate in the
lower atmosphere (troposphere) and then gradually migrate upward into the
stratosphere where they contribute to depletion of stratospheric ozone. The
atmospheric and chemical processes involved in the destruction of ozone are
extremely complex and are reviewed elsewhere [e.g., 1], but the following section
will summarize one the most important interactions.
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Scientists have demonstrated that in recent years the release into the
atmosphere of halogens containing chlorine and bromine — such as
chlorofluorocarbons (CFCs) and halons — has resulted in the destruction of the
protective ozone layer in the stratosphere. Short wavelength radiation hitting
the stratosphere causes a breakup of the chlorofluorocarbons releasing the
chlorine radicals (see figure 1). A chlorine radical destroys stratospheric
ozone through a catalytic cycle producing oxygen molecules. After converting
ozone to oxygen, the radical—now chlorine oxide—then reacts with an oxygen atom
from another ozone molecule and emerges unchanged, ready to destroy more ozone.
FIGURE 1. The catalytic cycle of a chlorine radical breaking down ozone into
oxygen molecules.
Less ozone in the stratosphere will result in a greater transmission of
ultraviolet radiation to the surface of the earth, causing detrimental effects.
Because of the long atmospheric lifetimes of CFCs and halons, scientists expect
stratospheric ozone to continue to decrease into the middle of the next century
even if emissions are curtailed worldwide [2].
TABLE I. Trace gases affecting ozone concentrations and global climate change.
Trace
Gas
(Formula) Primary Source
Ave. Life
in Atmos.
ODP*
GP**
CFC-11
(CFC13)
Refrigerant/AC, 75
Plastic Foams,
Aerosols
yrs
1.0
0.40
CFC-12
(CF2C12)
Refrigerant/AC,110 1.
Plastic Foams,
Sterilants
,0
1.00

CFC-113
(C2F3C13)
Solvents 90

0.8 0.3-
¦0.8
Halon 1211
(CF2ClBr)
Fire Exting. 25

3.0
2
Halon 1301
(CF3Br)
Fire Exting. 110

10.0
0.80
Carbon (CC14)
Tetrachloride
Industrial 67
Processes

1.1
0.05
Methyl
Chloroform
(CH3CC13)
Industrial and 8
Natural Processes

0.1
0.01
Nitrous Oxide (N20)
Fossil Fuels 150

—
0.016
Methane (CH4)
Biogenic Activity,
11
—
0.001
Carbon Dioxide (C02)
Carbon Monox. (CO)
Fossil Fuels
Motor Vehicles
Fossil Fuels
7
0.4
0.00005
2

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* ozone depletion potential (CFC-11 =1.0)
** greenhouse potential (CFC-12 =1.0)
Table 1 provides a summary of the major trace gases that contribute to ozone
depletion, including their primary uses, atmospheric lifetime, and projected
annual increase. Currently, the primary focus of regulations and mitigation
options are on CFCs and halons, as depicted in the Montreal Protocol [3]. The
treaty document was officially ratified in December 1988; regulatory provisions
become effective in July 1989. The agreement calls for a freeze of CFC
production (at 1986 levels) by 1989, a 20 percent decrease in production by 1993,
and an additional 30 percent decrease by 1998.
Several recent national and international work group reports detailed
discussions of the growing concern about stratospheric ozone depletion and
assessment of scientific bases underlying such concern [e.g., 1, 4, 5]. A report
by the Ozone Trends Panel has also highlighted the issue of stratospheric ozone
depletion [6]. The panel's report describes the global decrease in stratospheric
ozone in recent years and the probable role of CFCs and other ozone-depleting
compounds in the development of the Antarctic ozone hole.
ATMOSPHERIC INTERACTIONS
Many of the atmospheric trace gases, such as chloro-fluorocarbons, are
relatively transparent in the visible region of the solar spectrum. They do,
however, absorb the long wavelength radiation that is radiated back from the
surface of the earth, resulting in the greenhouse effect. In addition to CFCs,
other gases contribute to the greenhouse effect, including: carbon dioxide,
methane, nitrous oxide, and tropospheric ozone. The effects of these gases on
global warming is cumulative because each blocks different wavelength radiation.
Their concentrations have been increasing over time, some more dramatically than
others. This point is particularly important because of their relatively long
atmospheric lifetimes, especially CFCs, halons and nitrous oxide.
Chlorofluorocarbons (CFCs).
The release of CFCs and other chlorine-containing compounds decreased
initially in the 1970s as a result of regulatory action to ban selected, non-
essential CFC compounds used as aerosol propellants. This regulation was enacted
in several countries, including the United States. Currently, CFC production and
consumption are increasing due at least in part to the involvement of newly
industrialized and lesser developed countries in CFC use.
In addition to breaking down ozone through the action of chlorine radicals,
chlorofluorocarbons contribute to the greenhouse effect. Estimates put the CFC
contribution to global temperature change at 20-25 percent, although under the
Montreal Protocol it would be reduced to 15-20 percent.
Nitrous Oxide (N20).
Nitrous oxide in the atmosphere originates from both natural and man-made
sources, including many bacterial processes involved in the nitrification or
denitrification cycles. Recently, nitrous oxide has been increasing at a rate of

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V
about 0.2% annually. In the atmosphere N20 is partly converted into nitrogen
oxides (NOx).
Nitrous oxide (N20) plays a role in both ozone depletion and global climate
change. The N20 functions as a greenhouse gas contributing to global warming.
Converted to nitrogen oxides (NOx) it destroys stratospheric ozone in a catalytic
cycle similar to that of chlorine radicals. On the other hand, nitrogen oxides
can serve as a temporary sink for the ozone depleting chlorine monoxide (CIO), so
the net effect is uncertain. NOx also is a precursor to acid deposition.
Carbon Dioxide (C02).
The concentration of C02 has been increasing in recent years by an average of
about 0.5% annually. Carbon dioxide links the issue of stratospheric ozone
depletion to that of the global climate change issue primarily because of its
role as a greenhouse gas. As such, it will absorb solar radiation being radiated
from the surface of the earth and re-radiate it in all directions increasing the
global warming. Because it is a greenhouse gas C02 modifies the temperature
structure of the atmosphere, cooling the stratosphere# Less ozone is destroyed
if the stratosphere is cooler, so the effect of C02 acting alone is to decrease
ozone depletion in the stratosphere.
Methane (CH4).
Methane has been increasing fairly constantly at a rate of about 1% annually.
Resulting from both natural and man-made processes, methane is involved in
several important reactions in the atmosphere. Through its effect on the amounts
of water vapor in the stratosphere methane can lead to destruction of
stratospheric ozone. Water droplets may act as a surface upon which the
reactions that destroy ozone occur. The increase or decrease of ozone depletion
will depend upon where the water vapor is produced. Ozone depletion will
increase if water vapor increases in the stratosphere. But an increase in water
vapor in the troposphere will heighten the greenhouse effect—water vapor is the
most important greenhouse gas—and decrease ozone depletion through cooling the
stratosphere.
A further effect of methane occurs in the troposphere. Here, when methane is
oxidized, it will produce an increase in the amount of tropospheric ozone. This
reaction occurs in the presence of nitrogen oxide.
Natural sources of methane include natural wetlands, arctic tundra,
agricultural crops such as rice paddies, and ruminate animals. Man-made sources
of CH4 include the production of fossil fuels such as natural gas and oil, and
cement production. The natural processes contribute about half of the total
methane production.
Carbon Monoxide (CQ^.
Carbon monoxide is not a radiatively important trace gas, but it is involved
indirectly in both stratospheric ozone destruction and global warming. Carbon
monoxide controls the concentration of the hydroxy1 radical (OH) in the
troposphere, which has a direct effect on the concentration of methane. The
concentration of methane, as described earlier, plays a role in the amount of
tropospheric ozone as well as stratospheric ozone. Methane is also a very
important contributor to the greenhouse effect. Although calculations are highly
variable, estimates indicate that the concentration of carbon monoxide is
increasing at about 1% per year.
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Stratospheric and Tropospheric Ozone ((A .
Based on current scenarios, the stratospheric component of the total ozone
column is calculated to decrease over time, whereas the tropospheric constituents
of the total ozone column will increase. Whether or not there will be an overall
increase in the level of ultraviolet radiation reaching the surface of the earth
is still uncertain. Even if the levels of ultraviolet radiation at the earth's
surface were not to change, the photochemical reactions involving ultraviolet
radiation and the interaction of ozone with various other atmospheric gases would
alter the distribution of ozone in the atmospheric column. Changes in the
concentration and altitude of ozone will play a major role in altering
temperature and atmospheric processes affecting current climate and perhaps add
to long-term global climate change.
Increased levels of ultraviolet radiation reaching the earth's surface also
will increase the production of ozone at ground level through photochemical
reactions. These conditions affect regional air quality. Tropospheric ozone
formation takes place in the presence of nitrogen oxide. In addition, hydrogen
peroxide (H202) is produced, which is a strong oxidant and a catalyst in the
production of sulfuric acid from sulfur dioxide. These two processes illustrate
the linkage between stratospheric ozone depletion and acid deposition. Sulfur
dioxide and nitrogen oxides are the two major precursors to acid deposition.
Trace gases affecting ozone also contribute to global climate change. Any
efforts by humans to address the potential problems in either area will influence
the other. If global warming were to begin, efforts to address the rise in
greenhouse gases could increase ozone depletion. Restraints imposed on the
buildup of carbon dioxide, methane, and nitrous oxide to control their
contribution to global warming, might reduce their role as moderators of
potential ozone depletion in high CFC emission scenarios [7].
ECOLOGICAL INTERACTIONS
A major consequence of decreasing the ozone layer is an increase in the
transmission of UV-B radiation to the earth's surface. Scientists have
identified many potentially serious effects on the environment and on human
health from increased exposure to UV-B radiation. These include damage to:
agricultural crops, forests, marine organisms, human health (eye disease, immune
system, skin cancer), and certain materials. Changes associated with an altered
global climate, such as increased C02 levels, interact with the effects of UV-B
radiation.
Terrestrial Ecosystems.
In assessing the impact of increased exposure of crops and terrestrial
ecosystems to UV-B radiation it must be recognized that existing knowledge is in
many ways deficient. The effects of enhanced levels of UV-B radiation have been
studied in species from only a few representatives of the major terrestrial
ecosystems. We derive most of our knowledge from studies focused upon
agricultural crops and conducted at mid- latitudes. Despite uncertainties due to
the complexities of field experiments, the data presently available suggest that
plant photosynthesis is vulnerable to increased levels of solar UV-B radiation
[1]. Unlike drought or other geographically isolated stresses, stratospheric
ozone depletion would affect all areas of the world, including ecosystems whose
UV-B sensitivity has not been investigated.
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In general, UV radiation causes reduced leaf and stem growth, lower total dry
weight, and lower photosynthetic activity in sensitive cultivars of plant species
[8]. Less photosynthesis decreases the amount of C02 fixed by plants and
exacerbates the rise in C02 levels. Higher C02 may lead to global warming. This
shows a direct link from an effect of stratospheric ozone depletion through
terrestrial ecosystems to climate change.
Increased levels of UV-B radiation also may affect forest
productivity. Only limited data are available on coniferous species, but about
one-half of the species of seedlings studied were adversely affected by UV-B
radiation [9]. Existing data also suggest that increased UV-B radiation will
modify the distribution and abundance of plants. Even small changes in
competitive balance over a period of time can result in large changes in
community structure and composition [10].
Aquatic Ecosystems.
Current evidence indicates that ambient solar UV-B radiation is an important
limiting ecological factor in marine ecosystems. Even small increases of UV-B
exposure could result in significant ecosystem changes [11]. In marine plant
communities a change in species composition rather than a decrease in net
production would be the probable result of enhanced UV-B exposure [12]. A change
in community composition at the base of food webs may produce instabilities
within ecosystems that likely would affect higher trophic levels [13].
Inhibition of marine microbial activity by increasing UV-B radiation could
have important consequences for several global biogeochemical cycles.
Phytoplankton photosynthesis in the upper layer of the oceans provides a sink for
approximately 80% of the anthropogenic CO2 released to the atmosphere. Bacterial
activity in the oceans provides probably the most important global source of CH3I
and CH3C1 (the only significant natural source of chlorine to the stratosphere).
Microorganisms in aquatic ecosystems produce large quantities of methane and
nitrous oxide. Chemical and photochemical oxidation of natural organic matter in
water bodies produces carbon monoxide. Enhanced UV-B radiation, resulting from
stratospheric ozone depletion, can alter these processes and affect the levels of
the various greenhouse gases in the atmosphere.
Human Health.
Depletion of the ozone layer, resulting in large part from CFCs in the
stratosphere, leads to increased UV-B radiation. The UV-B radiation has many
adverse affects on human health. Kripke [14], van der Leun [15], and the U.S. EPA
[1] summarize the potential health effects of UV-B radiation. Probably the best
defined health effects are increases in skin cancer cases expected to result from
even small increases in UV-B radiation reaching the earth's surface. However,
skin cancer affects only a small minority of the world's population, light-
skinned Caucasians, and therefore is not a significant global problem.
Another important health concern — with potentially more extensive impacts on
more diverse human populations than skin cancer — is the effect of increased UV-
B radiation on human immune suppression. Adverse ocular effects have also been
documented from enhanced UV-B radiation, including an increase in the incidence
of cataracts in exposed populations.
CFCs, as mentioned above, are important greenhouse gases and contribute to
global climate change. Several elements of climate change could have important
human health effects. Higher temperatures will increase heat stress in humans,
especially among the elderly. Increased temperature combined with changes in
precipitation distribution could alter the geographic distribution of diseases
and parasites, providing vectors for the northward movement of tropical diseases.
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STATE OF KNOWLEDGE
Table 2 illustrates differences in our state of knowledge regarding various
anticipated biological effects and their potential global impact, as viewed by an
expert subcommittee of EPA's Science Advisory Board [16]. One of the present
dilemmas we face is that our current state of knowledge of effects that have the
greatest potential for widespread global impacts is low. For example, the
current knowledge of potential effects of increased UV-B radiation on the human
immune system is relatively low, but the global impact on human health could be
quite high.
TABLE II. Potential effects of increased UV-B radiation resulting from decreased
stratospheric ozone
Potential
Effects	State of Knowledge	Global Impact
Plant Life	Low	High
Aquatic Life	Low	High
Skin Cancer Moderate to high	Moderate
Immune System	Low	High
Cataracts	Moderate	Low
Climate impacts*	Moderate	Moderate
Tropospheric Ozone	Moderate	Low**
* Contribution of both stratospheric ozone depletion itself and gases causing
such depletion to climate changes.
** Impact could be high in selected areas typified by local or regional scale
surface-level ozone pollution problems.
Modified from Kripke [16].
POLICY INFORMATION NEEDS
Many uncertainties remain regarding the effects of stratospheric ozone
depletion and global climate change. With both of these issues, scientists
should structure research around questions that are explicitly relevant to policy
decisions. Using "policy-relevant questions" as the framework for research
provides the rationale for undertaking specific initiatives. The questions that
follow are based on fundamental information needs relevant to stratospheric ozone
7

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depletion, including a question addressing the information needed about linkages
between ozone depletion and climate change (question 4).
1)	How widespread are the potential effects of UV-B radiation? What
populations, systems or substances are at greatest risk? An increase in UV-B
radiation will continue to exert some degree of influence on man and the
environment for the foreseeable future. This stress will transcend regional and
national boundaries, exerting significant effects on widely separated ecosystems
and populations. These two attributes make understanding the effects of UV-B
radiation on biological and human systems of critical importance.
2)	How intensive are the effects of UV-B irradiance? What are the doses that
would pose a significant risk? The response of systems to UV-B radiation may
differ significantly for different life stages of the same species as well as by
latitude and season. What are the specific dose-response relationships, and what
mechanisms are involved? Identification of basic and common mechanisms of damage
will allow extrapolation of dose-response models to other systems not yet
studied.
3)	If the dose of UV-B radiation is reduced, what is the anticipated rate and
extent of recovery of sensitive systems? Organisms and ecosystems generally (but
not always) recover from environmental stress. It is important to know to what
degree and at what rate individual organisms and ecosystems can repair the damage
inflicted by enhanced UV-B irradiance. In managed ecosystems (agriculture and
silvaculture), UV-B tolerant species may replace less tolerant species. In
natural ecosystems some species may be able to adapt over time to increasing UV-B
irradiance.
4)	What interactions occur between increased UV-B radiation, global climate
change and atmospheric pollutants? The composition of the atmosphere depends to
a large degree on the natural and man-made emissions of greenhouse gases such as
carbon dioxide, CFCs, methane, and nitrous oxide. If new data suggested that
increasing UV-B radiation would alter biogeochemical cycles involving these
chemicals and result in a disruption of ecosystems or change in global climate,
additional regulation to protect the stratospheric ozone layer may be necessary.
5)	What mitigation options can be applied? To which systems? Chemicals with
less ozone-depleting potential can be used as alternative substances, such as for
aerosol propellants. But substitutes are not currently available for some ozone-
depleting compounds. Recovery and reuse of substances also is a viable option.
We also need to develop mitigative responses to the effects of UV-B radiation,
including the replacement of sensitive species with more UV-B tolerant species.
Options relevant to the human system are more tenuous and are important to
investigate.
Policy makers and scientists should periodically review and revise this list
of questions to reflect the current state of science.
CURRENT ACTIVITIES
The depletion of stratospheric ozone and subsequent increase in UV-B radiation
is a problem of global proportions, and one that is not occurring in an
environmental vacuum. Other changes are occurring, including global climate
change and acid deposition/air pollution. Scientists must examine these issues
collectively through an integrated research approach.
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A concerted effort is recently underway in the United States and numerous
other countries in response to plans and initiatives under the International
Geosphere-Biosphere Program (IGBP), also known as the Global Change Program.
IGBP, which was launched in 1986 by the International Council of Scientific
Unions [17], is the first international attempt to integrate research on global
climate change and stratospheric ozone depletion.
Reports by the National Academy of Sciences' Committee on Global Change [18],
and the White House's Committee on Earth Sciences [19] describe the work proposed
by the U.S. federal agencies. Agencies involved in the U.S. Global Change
Program include the following:
Department of Agriculture (USDA)
Department of Energy (DOE)
Department of the Interior (DOI)
Environmental Protection Agency (EPA)
National Oceanic and Atmospheric Administration (NOAA)
National Science Foundation (NSF)
National Aeronautics and Space Administration (NASA)
Success in addressing the global problems facing us today relies upon such
international and interagency coordination. It is also important to address the
related global problems as parts of a whole: stratospheric ozone depletion,
global climate change, and acid deposition are intricately linked.
9

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REFERENCES
1.	U.S. EPA. 1987. Risks to crops and terrestrial ecosystems from enhanced UV-B
radiation. Pages (11)1-31 in Assessing the Risks of Trace Gases that Can Modify
the Stratosphere, J. Hoffman (ed.) USEPA 400/1-87/001C. U.S. Env. Prot. Agency,
Washington, DC.
2.	Crawford, M. 1987. Landmark ozone treaty negotiated. Science, 237, 1557.
3.	United Nations Environment Programme. 1987. Montreal Protocol on Substances
that Deplete the Ozone Layer - Final Act. UNEP, Nairobi, Kenya.
4.	Schneider, T.; Lee, S.D.; Grant, L.D.; & Wolters, G.; eds. 1988. Atmospheric
ozone research and its policy implications: third US-Dutch international
symposium. Elsevier, Amsterdam, The Netherlands (in press).
5.	World Meteorology Organization (WMO) and Canada Department of the Environment.
1988. Proceedings of the World Conference on the Changing Atmosphere.
6.	Watson, R.T. and Ozone Trends Panel, Prather, M, J. and Ad Hoc Theory Panel,
and Kurylo M.J. and NASA Panel for Data Evaluation. 1988. Present State of
Knowledge of the Upper Atmosphere 1988: An Assessment Report. NASA Reference
Publication 1208. National Aeronautics and Space Administration, Office of Space
Science and Applications, Washington, DC.
7.	Miller, A.S. and I. Mintzer. 1986. The sky is the limit: strategies for
protecting the ozone layer. Research Report #3, World Resources Institute,
Washington, DC.
8.	Tevini, M. and W. iwanzik. 1986. Effects of UV-B radiation on growth and
development of cucumber seedlings. In Stratospheric Ozone Reduction, Solar UV
Radiation and Plant Life, R.C. Worrest and M.M. Caldwell (eds.), Springer-Verlag,
Heidelberg.
9.	Teramura, A.H. and J. Sullivan. 1988. Annual Report to the U.S.
Environmental Protection Agency: The Effects of Changing Climate and
Stratospheric Ozone Modification on Plants. Univ. of Maryland, College Park,
Maryland (USA).
10.	Gold, W.G. and M.M. Caldwell. 1983. The effects of ultraviolet-B
radiation on plant competition in terrestrial ecosystems'. Physiol. Plant. 58.
435-444.
11.	Damkaer, D.M. 1982. Possible influence of solar UV radiation in the
evolution of marine zooplankton, In The Role of Solar Ultraviolet Radiation in
Marine Ecosystems, J. Calkins (ed.), Plenum, New York.
12.	Worrest, R.C, 1983, Impact of solar ultraviolet-B (290-320 rati) upon
marine microalgae. Physiol. Plant. Ji£, 428-434.
13.	Kelly, J.R. 1986. How might enhanced levels of solar UV-B radiation
affect marine ecosystems? In Effects of Changes in Stratospheric Ozone and
Global Climate, J.G. Titus (ed.). U.S. Environ. Prot. Agency and United Nations
Environment Prog., Washington, D.C.
14.	Kripke, M. 1988. Health effects of stratospheric ozone depletion: an
overview. In: Schneider, T.; Lee, S.D.; Grant, L.D.; & Wolters, G.; eds. 1988.
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Atmospheric ozone research and its policy implications: third US-Dutch
international symposium. Elsevier, Amsterdam, The Netherlands (in press).
15.	van der Leun, J.C. 1988. Effects of increased UV-B on human health. In:
Schneider, T.; Lee, S.D.; Grant, L.D.; & Wolters, G.; eds. 1988. Atmospheric
ozone research and its policy implications: third US-Dutch international
symposium. Elsevier, Amsterdam, The Netherlands (in press).
16.	Kripke, M. 1987. Review of EPA's Assessment of the Risks of Stratospheric
Modification. Prep, by the Stratospheric Ozone Subcommittee, Science Advisory
Board. SAB-EC-87-025, U.S. Environ. Prot. Agency, Washington, DC.
17.	international Council of Scientific Unions. 1986. The International
Geosphere-Biosphere Program: A Study of Global Change. Rept. No. 1. ICSU 21st
General Assembly, Bern, Switzerland.
18.	National Academy of Sciences. 1988. Toward an Understanding of Global
Change: Initial Priorities for U.S. Contributions to the International
Geosphere-Biosphere Program. National Academy Press, Washington, DC.
19.	Committee on Earth Sciences. 1989. Our Changing Planet: A U.S. Strategy
for Global Change Research. Rept. to Accompany the President's FY90 Budget.
Washington, DC.
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing'
1. REPORT NO. 2.
EPA/600/D-89/127
3-Re PB90-112590
4, TITLE AND SUBTITLE
Linkage Between Climate Change and Stratospheric Ozone
Depletion
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7. AUTHOR(S)
R. C. Worrest A. M. Tait
K. D. Smythe
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16. ABSTRACT
Two primary areas link the issue of stratospheric ozone depletion to global
climate change: atmospheric processes and ecological processes. Atmospheric
processes establish a linkage through the dual roles of certain trace gases in
promoting global warming and in depleting the ozone layer. The primary radiatively
active trace gases are carbon dioxide, nitrous oxide, chlorofluorocarbons, methane,
and tropospheric ozone. In the troposphere, the atmosphere up to 10 miles above the
earth's surface, these compounds function as greenhouse gases. At increased levels
they can contribute to global climate change. Many of these gases also influence the
concentration of ozone in the stratosphere, the atmospheric layer located between 10
-30 miles above the earth's surface. This diffuse layer of ozone in the stratosphere
protects life on earth from harmful solar radiation. A reduction of this layer could
have very important impacts on the earth's systems.
The second mode of interaction revolves around various ecological processes.
Physical, chemical, and biological activities of plants and animals are affected
directly by global climate change and by increased ultraviolet radiation resulting
from depletion of stratospheric ozone.
17.
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