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United States
Environmental Protection
Agency
EPA-600/9-86/01
July 1986
Research and Development
EPA Workshop on Global
Atmospheric Change
and EPA Planning
Final Report
<„ i'
U.S. Environmental Protection Agency
Office of Research and Development
Atmospheric Sciences Research Laboratory
Research Triangle Park, NC 27711
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EPA-600/9-86/016
July 1986
EPA WORKSHOP ON GLOBAL ATMOSPHERIC CHANGE AND EPA PLANNING
FINAL REPORT
Professor Harvey Jeffries, Workshop Chairman
Department of Environmental Sciences and Engineering
The University of North Carolina at Chapel Hill
Chapel Hill, NC 27514
Contract No. 68-02-3839
Project Officer
Basil Dimitriades
Atmospheric Chemistry and Physics Division
Atmospheric Sciences Research Laboratory
Research Triangle Park, NC 27711
Atmospheric Research Sciences Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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DISCLAIMER
Although the workshop described in this report has been funded wholly by the U.S. Environmental
Protection Agency under Contract 68-02-3839 to Northrop Services, Inc., the report has not been
subjected to the Agency's required peer and policy review and therefore does not necessarily reflect
the views of the Agency and no official endorsement should be inferred. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
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ABSTRACT
Expanding industrial and agricultural growth are leading to greater and greater emissions of many
compounds that are changing the earth's atmosphere and climate. The changes are warming of the
climate caused by greenhouse gases, stratospheric ozone modifications caused by chlorofluoro-
carbons, and tropospheric chemistry modifications caused by carbon monoxide and methane.
Consensus among scientific researchers as to the causes, probable magnitudes, and timing of the
changes has led to a call for assessment of policy options and impacts.
This workshop was organized to begin a collaborative process among EPA research and policy
personnel, and climate researchers. EPA policy makers described their needs and working methods.
Eight technical papers, presenting the state of the science, were given by non-EPA climate
researchers. In addition to typical discussion and dialogue, a panel of policy makers and scientists
discussed the impact of the projected global climate change on EPA planning. EPA repsonses to
climate problems were suggested.
in
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ACKNOWLEDGEMENTS
We appreciate the time and effort given by the presenters at this workshop. Their contributions
made the workshop possible.
DennisTirpak and John Hoffman at the Office of Policy, Planning, and Evaluation orginated the
concept of this workshop. Basil Dimitriades and Joseph Buffalini at the Atmospheric Sciences
Research Laboratory; Larry Zaragoza at the Office of Air Quality, Planning, and Standards; Bill Keith
at the Off ice of Research and Development; and Dwain Winters at the Off ice of Program
Development were instrumental in defining elements of the workshop.
The efforts of Jaynee Allen, Northrop Services, Inc., in managing the actual meeting are gratefully
acknowledged. Linda Cooper, Workshop Coordinator, Northrop Services, Inc., provided assistance in
planning the workshop and making arrangements with the presenters. Her editorial assistance in
assembling this final report was essential and is appreciated.
IV
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CONTENTS
Acknowledgements iv
Executive Summary 1
Workshop Purpose 1
Summary of Scientific Information 2
EPA'sPlanning Needs 12
Pane! Discussion 14
Recommendations 15
Panel Discussion 17
Papers
_ 1. Emissions and Atmospheric Concentrations
• Ralph Cicerone
2. Evidence for a Greenhouse Effect
John Perry
3. Past and Future Changes in Climate
David Rind
4. Abstract of Depletion of Stratospheric Ozone
Richard Stolarski and Donald Wuebbles
Nimbus 7 SBUWTOMS Measurements of the Springtime Antarctic Ozone Hole
Richard Stolarski et at.
• 5. Relationships among CO, NOX, CH4, and HO'
Anne Thompson
6. Tropospheric Ozone
Jennifer Logan
fl. Effects of Increased UV Radiation on Urban Ozone
Gary Whitten
_ 8. Linkages between Global Climate Change and Acid Rain
• Dennis Tirpak
Appendices
A. Workshop Agenda
B. Workshop Attendees
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Executive Summary
Workshop on
Global Atmospheric Change
and EPA Planning
Harvey E. Jeffries
Workshop Chairman
Workshop Purpose
Expanding industrial and agricultural growth are leading to greater and greater
emissions of many compounds that are changing the earth's atmosphere and climate.
The changes are broadly classified as:
• warming of the climate caused by increasing concentrations of "greenhouse"
gases;
• modifications of stratospheric composition and ozone chemistry caused by the
introduction of compounds, especially the chlorofluorocarbon gases, that con-
tribute to ozone depletion; and
• modifications of tropospheric chemistry mainly caused by increasing levels of
carbon monoxide and methane.
The emissions include carbon dioxide from fossil fuel combustion, carbon monox-
ide from automobile and combustion sources, methane from agricultural sources,
nitrous oxide from fertilizers, and Freons from industrial processes.
The World Meteorological Organization, United Nations Environment Pro-
gramme, and the International Council of Scientific Unions sponsored a conference
on assessment of global climate change. The meeting was held at Villach, Austria
in October 1985 and was attended by some 80 scientists from 29 countries. The
participants concluded that our understanding of the implications of rising concen-
trations of trace gases is "sufficiently developed that scientists and policymakers
should begin immediately to work together to assess policy options and impacts."
The Global Atmospheric Change and EPA Planning workshop was designed to
begin this active collaboration process among EPA research and policy personnel
and non-EPA climate researchers. The workshop served as a forum for scientific
leaders in the climate research field to impress upon the decision makers the extent
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Summary of Scientific Information
to which they understand the problems and believe that actions are needed. EPA
decision makers had the opportunity to begin an on-going dialogue with climate
researchers and to develop a better understanding of the relevance of this field to
EPA control policies and methodologies.
Scientific presenters at the workshop were from the National Center for At-
mospheric Research, National Academy of Sciences, Goddard Space Flight Center,
Goddard Institute for Space Studies, Lawrence Livermore National Laboratory,
System Applications, Inc., and Center for Earth and Planetary Physics at Har-
vard University. In addition, collected papers and abstracts from research being
done at the Geophysical Fluid Dynamics Laboratory at Princeton University, the
Department of Chemical Engineering at Washington State University, the Center
for Meteorology and Physical Oceanography at MIT, the Department of Chemi-
cal, Biological, and Environmental Sciences at Oregon Graduate Center, and the
British Antarctic Survey from Cambridge, U.K. were supplied to all participants
in the form of a Background Information Notebook. The notebook also included
information from the National Climate Program and the whole text of the Villach
conference statement.
Summary of Scientific Information
Climate Modification Processes
There is reliable evidence that the climate of the earth is far from constant.
The most fundamental factors influencing climate are: the solar constant (i.e.,
the energy flux at the earth's orbit) and orbital variations (i.e., changes in the earth's
axis tilt) that influence the latitudinal distribution of the energy input. There is
evidence that suggests that major climate swings between glacial and interglacial
periods have occurred every 120,000 years, and it is believed that orbital variations
may have been the triggers for these large changes in climate although changes in
CO2 concentrations are also implicated (see paper by John Perry).
The composition of a planet's atmosphere influences its global temperature.
The earth's climate is maintained by a balance between incoming short wavelength
radiation (e.g., the sun's spectrum peaks in the yellow visible region) and outgoing
long wavelength radiation (e.g., infrared (|R) region). Gases that absorb radiation
in the IR-region can influence the global temperature by intercepting some of the
outgoing energy and re-radiating it back to the surface, thus warming the surface.
This is called the "greenhouse" process and the gases are described as greenhouse
gases (see papers by John Perry, Ralph Cicerone, and David Rind). Our knowledge
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The Atmosphere Is Dynamic
of atmospheric compositions from Venus and Mars and their mean global temper-
atures are consistent with this simple model of the greenhouse effect, (see John
Perry's paper and the Hanson, et al. paper in Background Information Notebook).
Water vapor is one of the major naturally occurring greenhouse gases. The
greenhouse effect caused by the earth's pre-industrial atmosphere is responsible for
raising the earth's average global temperature by about 30°C. The earth's global
temperature would be about -18°C without an IR-absorbing atmosphere.
In addition to the direct greenhouse effect of IR-absorbing gases, there are major
positive feedback processes that determine climate sensitivity to long-term changes.
Examples of these feedback processes are:
• Air temperature controls how much water vapor is present in the air, which
determines how much water vapor contributes to the greenhouse effect. Cold
air holds less water, which leads to less greenhouse effect, which leads to more
cooling, which lowers air temperature, leading to lower water vapor. Likewise,
warmer air holds more water vapor, which leads to more greenhouse effect,
which leads to more warming and still warmer air.
• Ice reflects incoming solar radiation back to space, and therefore, energy to
warm the earth is lost. Warming of the earth caused by some other process,
however, can lead to less ice, which reflects less solar radiation (more is absorbed
by bare earth), leading to more warming and still less ice. The converse is also
true.
Climate change is, therefore, discussed in terms of an initial forcing function (the
factor that caused the change to occur) and the positive and negative feedback
processes that increase or decrease the initial change. Thus, the direct effect of
doubling the carbon dioxide (COj) over pre-industrial concentrations is estimated
to be a temperature rise of 1.2°C because of increased IR-radiation absorption (the
direct effect); currently the total multiplicative feedback processes are estimated to
increase the initial effect by factors of 3 to 4, leading to a total temperature rise at
equilibrium of 3.2-4.8°C (the total direct and indirect effect).
The Atmosphere Is Dynamic
The atmosphere is in continuous motion and is coupled to the oceans and the
biosphere; in addition, the atmosphere's composition is a result of both long-term
and short-term chemical cycles.
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The Atmosphere Is Dynamic
The troposphere is coupled (from presentation by McElroy):
• pole-to-pole with a time constant of 1-1.5 years;
• to the stratosphere with a time constant of 5 years;
• to the ocean with a time constant of 10 years;
• to the biosphere with a time constant of 10 years.
The oceans have a large heat capacity, and thus, they introduce large lags in re-
sponse time for temperature changes. Oceans are the dominant sink for atmospheric
C02.
The abundance of trace gases in the global atmosphere is the result of the inter-
action between sources and sinks; estimates of atmospheric lifetimes for important
trace gases are given in the Cicerone paper.
For the majority of the trace gases, the two major sink processes are reaction
with hydroxyl radicals (HO ) in the troposphere and photolysis by short wavelength
ultraviolet (UV) radiation in the stratosphere.
Hydroxyl radicals are produced in the troposphere by a chemical cycle involving
the oxidation of methane (CH4), carbon monoxide (CO), other hydrocarbons, and
aldehydes. Its primary source in the troposphere is the photolysis of ozone (Os), as
well as the reaction of hydroperoxy radicals (HO2) with nitric oxide (NO). A major
source of HO2 radicals is the photolysis of aldehydes (such as formaldehyde), which
are products of all organic oxidation including methane. Methane and CO are the
primary consumers of HO in the troposphere (see paper by Anne Thompson).
Outside the earth's atmosphere, the solar spectrum is rich in high-energy short
wavelength UV-radiation. As light passes through the atmosphere, most of the
shortest wavelength UV-radiation is absorbed by various gases that photolyze into
reactive radicals. Absorption of UV-radiation is a dominant sink process for many
trace chemicals. These chemicals are relatively inert in the troposphere: they do
not wash out, do not react rapidly with HO , and do not photolyze at the longer
UV wavelengths found in the troposphere. Their photolysis in the stratosphere,
however, can introduce materials not normally found there, and thus, influence
major chemical cycles (see paper by Richard Stolarski).
The most common stratospheric photolysis process is for molecular oxygen (02)
to photolyze into atomic oxygen (o). The O atom most often reacts with O2 to
produce ozone (Og). Ozone also absorbs UV-radiation and photolyzes to produce O
and O2 again. This cycle recurs many times and converts light energy into heat in the
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upper stratosphere. Sometimes O reacts with O3 to produce two 03, thereby ending
a long cycle. This absorption of UV radiation limits the amount of short wavelength,
high-energy light that reaches the earth's surface. Such wavelengths can cause skin
cancer and promote rapid smog formation (see paper by Gary Whitten).
The dynamic processes and chemistry of the atmosphere are so complex and
interactive that mathematical simulation models are the only tools available to
comprehend the processes. Thompson said, "We are not dealing with independent
gases whose sources and sinks can be isolated from one another, but we are deal-
ing with a series of compounds that are linked by photochemical reactions. The
causes and effects of processes, therefore, are not so clear." For example, Stolarski,
in his presentation, said that stratospheric O3 concentration determines how much
UV-radiation is available; the available UV-radiation determines how rapidly other
compounds are decomposed, which interact with the O3 cycle to determine how
much O3 would be present. Furthermore, reactions and UV absorption give rise to
heat, which results in winds that transport material that influences the concentra-
tions of the reactants; in addition, temperature feeds back on the rates of chemical
reaction producing the material that is absorbing the UV-radiation to cause the
heating, and so on.
Because of the complexity, models must often simulate only one aspect of the
problem, using simple or average descriptions for the other aspects. For example,
one-dimensional models tend to have complex chemistry and no horizontal atmo-
spheric transport. Still, these models predict the average concentrations in the
hemisphere fairly well. More complex and costly two-dimensional models also pre-
dict concentrations as a function of latitude as well. These models have to make
assumptions about how transport occurs and different assumptions lead to some-
what different predictions of the temporal and spatial distributions of the O3.
The amount of O3 in the atmosphere is most conveniently measured as the "total
column" of O3 in Dobson Units (DU). Ozone, however, has tropospheric sources as
well as the stratospheric source, and thus, its vertical concentration profile varies
significantly. The peak O3 concentration is usually in the stratosphere at 20-30 km.
Likewise, because of atmospheric dynamics, total column O3 varies greatly, much
like weather patterns, over the surface of the earth. Values are usually between
250-500 DU.
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Emissions Are Increasing
Emissions Are Increasing
Cicerone stated that although it is difficult to believe that "global conditions can j
be changed by these small concentrations of little known gases, in fact, there is a *
10 year record of research that gives some confidence that change is under way. In
many cases, research has progressed to process and mechanistic understanding as I
well." *
Carbon dioxide concentrations have increased from 315 ppm in 1958 to more I
than 340 ppm in 1985, a very considerable increase. Researchers, using samples
from ice cores, have determined that pre-industrial CO2 concentrations were about ,
225 ppm, and in the last glacial period, the values were even lower (see Paper 4 in |
the Background Information Notebook.)
Part of the source of this increase in COj is from the combustion of fossil fuel.
Man's activities are injecting about 5 gigitons per year into the atmosphere; about
50% of this material appears to remain in the atmosphere, the rest going into the
oceans and the biosphere (see paper by John Perry). In his presentation, McElroy
estimated that "In terms of the global natural carbon cycle, we are lifting carbon
from the sediments 20-30 times faster than nature. It is not surprising that we are
seeing a steady rise in C02."
Chlorofluorocarbons (CFC) have been measured precisely and accurately over the
last decade, and the evidence clearly shows that their atmospheric concentrations
are increasing at about 3% per year. The two most abundant Freons, F12 and
Fll (CCl2F2 and CClsF), have long atmospheric lifetimes (65 and 110 years) and are
ultimately destroyed by UV-radiation in the upper stratosphere.
Nitrous oxide (N2O), which had a northern hemispheric concentration of 301 ppb
in 1980, has an estimated atmospheric lifetime of more than 120 years. Careful
measurements over the last four years show that its concentration is increasing at
about 0.5 ppb per year. McElroy, in his presentation, estimated that production
now exceeds loss by 40%. Considerable uncertainty exists in the source of this
increase; the two most likely sources are coal combustion and microbial production
through nitrification and denitrification of inorganic nitrogen fertilizers applied to
soils. Estimates of atmospheric concentrations in the year 2030 give a range of
350-450 ppb.
Methane (ChU) is the most abundant atmospheric hydrocarbon, and in 1980
its concentration was 1.65 ppm in the northern hemisphere. Its concentration has
also been shown to be increasing at rates between 0.5 and 2% per year, and the
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Implications For Climate and Atmosphere
rate itself has been increasing. By using measurements from ice cores, it has been
estimated that the CH4 concentrations have approximately doubled in the last 350
years, with most of the increase occurring in the last 150 years (see Paper 6 in
the Background Information Notebook). At least 80-90% of CH4 sources could be
biogenic, the major sources being enteric fermentation in ruminant animals, release
from organic-rich sediments below shallow water bodies (e.g., rice paddies), and
biomass burning. As indicated above, reaction with HO is the dominant sink for
CH4.
Near the surface, in rural areas of Europe and the central and eastern U.S., the
summertime concentration of Os may have increased by 6-12 ppb since the 1940s.
There is reliable evidence for an increase in ozone in the middle troposphere over
Europe during the past 15 years, and weaker evidence for a similar increase over
North America and Japan. It is argued that these increases are due to photochem-
ical production associated with anthropogenic emissions of nitrogen oxides (NOX),
hydrocarbons, and CO from combustion of fossil fuels (see paper by Jennifer Logan).
Implications For Climate and Atmosphere
Increasing the concentrations of IR-absorbing gases can cause an increase in the
earth's average global temperature. Three independently developed global climate
models predict a total climate sensitivity of about 4°C for a doubling of COj concen-
trations over pre-industrial times or for a combination of some increase in COj and
increases in other greenhouse gases such as methane, ozone, chlorofluorocarbons,
and nitrous oxide (see paper by David Rind).
Although CO2 is the greenhouse gas that is increasing the most, other trace
gases (Freons, N2O, CH4, and Os) also have a major greenhouse effect. If present
trends continue, their combined concentrations will lead to an equivalent effect of
doubling the CO2 concentration by the 2030s instead of the actual doubling of the
CO2 concentration that was predicted to occur sometime around 2070 (see Paper 1
in Background Information Notebook).
Analysis of observations over the last 100 years suggests that the average global
temperature has increased 0.3-0.5°C. Model simulations of the changes in emissions
and concentrations over this same period also predict similar increases. Because of
uncertainties in the model inputs and formulations, however, it is not possible to
ascribe, in a scientifically rigorous manner, the increase in global temperature to
the increases in the greenhouse gases (see paper by David Rind, and Paper 1 in
Background Information Notebook).
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Implications For Climate and Atmosphere
To put a 4°C change in average global temperature in perspective, during the
last Ice Age, 18,000 years ago, the average global temperature was 3.7°C cooler
than now; ice extended over Long Island; some northern areas had temperatures
25°C cooler than present day temperatures, primarily because there were large ice
sheets 3 km thick. At the same time, however, there was very little temperature
change in the low latitudes. Simulating these Ice Age conditions has been used as
a validation test for many of the global climate models.
Such studies show that small initial changes can be greatly amplified by positive
feedback processes. Because of large lag times in the feedback processes, however,
the system requires sustained initial perturbations so the feedback processes can
build. For example, the oceans have a very large heat capacity and the deep water
turnover time may be hundreds of years, so it would require a long period to heat
up or cool down the oceans. The surface layers of the ocean may reach equilibrium
more rapidly.
Although agreeing on the ultimate climate sensitivity, the climate model pre-
dictions by different groups differ in the spatial details of the temperature changes,
some giving 25°C warmings occurring throughout the southwestern U.S. and ex-
treme northeast and others predicting less dramatic changes. In all cases, the lower
latitudes have a smaller change than the higher latitudes.
In a time-dependent model for the period 1956 to 2010, Rind and his co-workers
found that temperature changes on the order of 0.3-0.5°C occur with no specific
forcing whatever, just due to the natural variability and dynamics of the model.
Therefore, if we wanted to be sure that we were seeing a clear indication of the
warming trend, a rise of 1°C would have to be observed. Rind's model, using
current emissions trends, suggests that this will occur in the 1990s.
The photolysis of chlorofluorocarbons in the stratosphere results in the release
of chloride that acts as a catalyst in shortening the 0$ formation chain reaction
and ultimately lowering the stratospheric 03. Stratospheric Os absorbs short wave-
length UV-radiation and thus filters such radiation from the earth's surface. Lower
Oa results in more UV-radiation in the troposphere and at the surface, as well as
cooler stratospheric and warmer tropospheric temperatures. At the same time, the
increase in tropospheric gases such as CH4 and NOX results in increases in O3 in the
troposphere.
In their presentations, Stolarski and Wuebbles described model calculations
of global QZ production that have been made from pre-industrial times to 2050.
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These models predict that the total column 03 increased during the 1970s. This,
however, was the result of the cancellation of substantial, but opposing changes in
Os with altitude. A maximum decrease of 4.4% was predicted at 40 km, largely
due to CFC emissions (it was noted that increasing COj emissions reduced the CFC
impact!), while an increase of 1% was predicted at 30 km and an increase of 6.7%
was predicted at 8-9 km due to aircraft and increased CH4 emissions.
As indicated above, based on monitoring data, there is reliable evidence that
Os did increase in the middle troposphere in Europe over the past 15 years and
supporting evidence for a similar increase in North America and Japan. This in-
crease is estimated to contribute significantly to the total column O3, and may have
compensated for a 20-30% decrease in O3 in the stratosphere over middle and high
latitudes of the northern hemisphere (see paper by Jennifer Logan).
In future scenarios, most models predict either a small decrease or increase in
total column O3 mainly due to increasing CH4 in the troposphere. The vertical
distributions of O3, however, are dramatically modified. For example, one model
predicts up to a 36% O3 increase below 26 km and a 22% O3 decrease above 26 km.
The British have been measuring total column O3 at Halley, Antarctica (76°S)
since the International Geophysical Year in 1956. In 1957, the values were 310-
320 DU in the springtime. Now values are 40% lower in October (antarctic spring).
In the winter at Halley, there is no sunlight; in the spring, the sun returns. It is
speculated that during the dark, very cold winter, CFCs accumulate, and when the
sun does reach the upper stratosphere for the first time in the spring, the CFCs
undergo rapid reaction and destroy the O3. As the CFCs are consumed, 03 levels
gradually increase to higher values, but by autumn the level is still 5-10% lower
than it was 10 years ago. (see Paper 9 in Background Information Notebook)
NASA has made a color movie from the Nimbus-7 satellite's TOMS instrument
that can measure total 03. The movie, which was shown at the EPA workshop,
shows the pole view of O3 concentrations on each day in October for the years
1980 to 1985. The images are dramatic: in the beginning of each year the 03 is
reasonably uniform, and then the depletion process starts. It appears as if a large
hole—thousands of kilometers wide—is being eaten in the atmosphere. The O3
begins to recover near the end of the month. Each year, however, the area of O3
depletion increases as does the depth of the central depletion. In 1984, the pole O3
values were down to about 190 DU, and in 1985, they were down to about 180 DU
(see paper by Richard Stolarski).
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Implications For Climate and Atmosphere
Increased emissions of CO and CH4 can, through complex photochemical interac-
tions, result in a decrease in the average tropospheric HO concentration. Estimates
suggest that HO concentrations were as much as 30% higher in 1860 than now.
Projections of emissions patterns suggest that in 2035, HO concentrations will have
decreased another 20-30%. Not only will many trace gases (including some toxics)
survive longer in such conditions, so will CH4, which contributes to the greenhouse
effect. In addition, Os production increases as a result of the increased organic oxi-
dation, and Os is a greenhouse gas that also can contribute to the global warming
(see paper by Anne Thompson). Longer survival in the troposphere also means a
greater concentration in the stratosphere through tropospheric-stratospheric cou-
pling and transport. McElroy, in his presentation, indicated that CH4 oxidation
is now a major source of water vapor in the stratosphere; low temperatures and
atmospheric stability prevent water vapor from being directly transported into the
stratosphere.
Preliminary modeling studies of urban smog formation have shown the effects
of increased UV-radiation caused by stratospheric Q$ depletion combined with an
increase in global temperature. These suggest a significantly enhanced potential for
smog formation. In the simulations, the warming always increased the production
of Os and decreased the production of peroxyacyl nitrate (PAN). The direct effect
of raising temperatures by 4°C was to increase Os by 10-20 ppb for typical urban
scenarios. More complex was the effect of increasing UV-radiation, in that different
results occurred in differ city simulations, with the maximum change being a 26%
increase in Os for a 16% decrease in stratospheric O3. The combined effects appear
to be additive in some scenarios, resulting in a 40% increase in Os in the Nashville
case, increasing the O3 from its current 130 ppb to 184 ppb in the future, keeping
the emissions the same as current values.
Climate changes may have a variety of impacts on the acid rain problem (see
paper by Dennis Tirpak):
• Increased air temperatures will lead to a larger demand for electricity for air
conditioning in summertime, which most likely will lead to increased sulfur
dioxide (802) atmospheric: loadings; in addition, the higher air temperatures
will lead to a more rapid oxidation of the SO2 and NOX, particularly in northern
latitudes, which will decrease the importance of long-range transport of sulfate
and nitrate ions.
• Altered precipitation patterns can potentially change both the importance of
some long-range sources and the impacts on aquatic systems and forests (over
the past 50 years, increased precipitation has been associated with increased
temperatures in the Adirondack Mountain area of New York); the forests may
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Implications For Climate and Atmosphere
undergo significant ecological changes due to altered microclimates; a changed
winter snow pack can lead to altered vulnerability of aquatic life during spring
snow melt; altered frequency of wet days can lead to changed degradation rates
for materials.
Changed cloud cover at different altitudes may lead to changes in aqueous-
phase oxidation rates for SOj and NOX, thereby altering the significance of
long-range transport; in addition, increased cloud cover may increase natural
NOX formation from increased lightning.
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EPA's Planning Needs
EPA's Planning Needs
At the workshop, many EPA policy makers discussed the problems of balancing
today's apparently pressing needs against problems that are long-range, global in
scale, and multi-component in nature.
Hoffman, from the Office of Policy Analysis, described the basic EPA approach
as "setting air quality goals and then making plans to achieve these goals." He
stressed that present EPA planning relies heavily on historical trends. The time
dimension for major climate change is shortening, however, and thus the predicted
global changes have a large potential to impact current decisions.
Emisson, Director of the Office of Air Quality Planning and Standards (OAQPS),
stressed that his organization must make numerous trade-off decisions. This results
in a need to have a clear understanding of the problems, especially the uncertain-
ties associated with the problem, not only to make better decisions, but also to
convince the public when there is a need to change. In addition, the public health
implications of the problem must be recognized and methods for risk management
and risk assessment must be developed and applied before regulations can be put
forth that might affect the problem.
Weigold, head of Strategic Planning Programs in OAQPS, stressed that OAQPS
has been in the mode of dealing with "known conventional problems" and functions,
for the most part, in a reactionary mode. Furthermore, EPA tends to be constrained
by the realities of the enabling legislation. Efforts are under way, however, to
broaden OAQPS's viewpoint, to improve information flow in the organization, to be
less single pollutant oriented, and to deal with more complex cross-media problems.
One such action in OAQPS has been the organization of the Strategic Planning
Program to identify emerging issues and problems and to formulate responses.
Hoffman ended his presentation by posing a series of questions for consideration
by presenters and attendees. These were:
• How might EPA programs be affected?
• When might current programs be affected?
• How significant might changes be?
• How could EPA programs be used to limit change, if needed?
• Are current science efforts going to provide EPA with answers in time?
• Is EPA building its own intellectual infrastructure rapidly enough?
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EPA's Planning Needs
Weigold presented another set of questions that reflected OAQPS's needs; these
were:
• What is happening or may be happening?
• When will serious problems become manifest?
• What kind of research may be needed?
• What will EPA get for that research?
• Will this research be worth the required trade-offs?
• What kinds of changes in present operations are needed?
• What solutions are there to these problems, if any?
• What are the institutional and legislative barriers to solutions?
• How should the problem best be presented to the public and to lawmakers?
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Panel Discussion
Panel Discussion
A discussion panel that included policy planners and researchers held a lively dis-
cussion.
The basic position of many OAQPS staff members was that the linkages between
the global climate and atmospheric change issues and the regulatory program had
not been built. EPA was described as basically a regulatory agency, and research
is done in support of regulation. The limited research resources of EPA are al-
ready overextended in dealing with immediate issues and it was hard for many to
determine what needed to be done.
The Office of Policy, Planning, and Evaluation staff members suggested that the
global climate change issue did add a long-range perspective to many daily issues
at EPA, for example, the O3 attainment issue. Global climate change would likely
make it much more difficult to move near-attainment areas into attainment and to
keep those who are in attainment still in attainment in the future. Some discussion
suggested that regulations could be designed to prevent further deterioration of
stratospheric O3 and these could be beneficial in helping marginal locations meet
Os attainment.
Improving awareness of staff making regulatory decisions every day in the
Agency was another major point made. Taking into account the impact of global at-
mospheric changes on these current regulatory activities might lead to more optimal
decisions. In addition, EPA should expend more effort to inform outside climate
researchers of Agency informational needs in the climate change area.
It was suggested that the global climate change issue would have a gradual
and incremental effect on the Agency and would eventually be incorporated into
the Agency, that is, the issue would be "institutionalized" and the Agency would
therefore deal with global climate change as part of its normal activities.
Some of the scientists suggested that many of the major effects of global at-
mospheric change would occur while this "institutionalization" of the problem was
occurring. This is because so much of the problem was linked to our use of fossil
fuel, and changes of the magnitude needed to delay the changes would require more
than 30 years to implement. During this time, major changes in climate would
occur.
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Recommendations
Recommendations
Four general types of responses to these problems were described by Hoffman:
• Understanding—We can continue to develop the basic science and measurement
programs needed to determine the magnitude and timing of environmental ef-
fects. We can modify current policy development (one suggestion raised in
discussion was to include global climate effects in environmental impact state-
ment development).
• Preventing—Many scientists believe that climate change can not be prevented:
too much material is already in the air and only lags in the system (such as
ocean turnover) are delaying the changes; the changes will happen eventually.
Furthermore, the problems are global in scale and other industrially developed
countries make major contributions to the problems.
• Limiting—There are questions about the quasi-irreversibility of the systems
that suggest that options to limit the changes are difficult. The long lifetimes
of some of the species mean that if emissions stopped now, it would require
30-50 years for conditions to be restored to those of pre-industrial times. On
the other hand, a "wait and see" approach implies very significant changes will
occur when the system lags catch up with the emissions input. Actions can
be taken to limit the emissions of some of the critical species, for example,
non-critical uses of Freons.
• Adjusting—We can adjust to the existence of the situation by accounting for
its existence in our activities. This means that decision makers at all levels
should begin to consider the impact of the probable changes in their policies
and strategies. There have been very few policy impact analyses comparable
with the level of scientific modeling work done in the last few years.
McElroy said, "One of the challenges that EPA should address is the problem
of devising an observational strategy and supporting validating studies that would
give the policy and scientific community a good model for the continental U.S."
Tirpak, from OPPE, stressed that in the short term, EPA can build understand-
ing and institutional capability. Furthermore, EPA should undertake additional
analyses to assure that agency actions do not inadvertently speed up the rate of
change by EPA actions. In the long term, Tirpak suggested that EPA should use
climate scenarios in long-range transport models; conduct synergistic experiments
for the world of 2020 (e.g., CO2, increased UV-radiation, and acid rain) on forests,
crops, lakes, and materials; and we should begin the process of developing a risk
methodology for the global environment.
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Panel Discussion
Transcribed and Edited by
Harvey Jeffries
Workshop Chairman
A panel consisting of EPA policy, headquarters, and research staff and of invited
scientists was assembled under the leadership of Dr. Michael McElroy, Harvard
University, to discuss the topics and issues that had been raised. Dr. McElroy
asked each panel member to make initial comments.
B. Steigerwald, OAQPS/EPA
"I have been disappointed. I have a concern about not only how this issue affects
EPA but also how it specifically affects the Air Program and there has not been as
much said about EPA Planning as I had hoped. I am able to concede a lot of what
the scientific consensus is, but I do not have a good sense of what it means to EPA.
That is, putting this information in the context of EPA and what EPA does.
"EPA is a regulatory agency and we put up with research because it helps us
support policy decisions, keeps us from doing dumb things, and helps define regula-
tory issues. If we expect more than that from EPA we are going to be disappointed.
We fight the budget fights on a year-to-year basis looking at the current issues.
After the FY86 budget was fixed, for example, the air research group had to change
the current budget and operational plans for such things as: a million dollars for
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M. McElroy
the radon problem; $900,000 to non-ionizing radiation; a million dollars for low
lead gasoline effects on agricultural vehicles; accident prevention; and indoor air
quality and toxics required an additional $800,000. So it appears that we are con-
stantly dropping a million here, a million there, until 10% of the research program
is reprogrammed after the start of the fiscal year.
"Although I can see how this issue might fit with the ozone problem in Nashville
40 years from now, I do not see what it means to us now. We did not ask ourselves
tough enough questions."
M. McElroy
"While I am sympathetic to the day-to-day pressures that a manager like you has,
I think that perhaps the promise to solve the management problems of EPA as well
as addressing the science problems, would not be possible in a day and a half. I
am distressed by your statement—and I hope that you really did not mean it—that
EPA is a regulatory agency and that you are obliged to put up with research. EPA,
under those circumstances, will always make decisions in ignorance."
B. Steigerwald
"We do have research programs, for example, five-year, sizable programs to attempt
to understand what is involved in say the context of a ten-year regulatory program,
in which the first five years are an attempt to understand it and the last five years
are when the regulations are passed and we attempt to meet the requirements. This
is a focused, narrow program, however, and we have very little money to attempt
to define problems. We often are pushed to move into regulatory programs early
and need immediate research support for these. There is little left over to attempt
to define problems and attempt to study things."
D. Rind, Goddard Institute for Space Studies
"There is a lot of research going on that can be of benefit to EPA. These researchers
do not always know EPA needs. Without pre-consultation, it is very hard to know
what small incremental work could be done. You need to develop such communica-
tions: 'What programs might be affected by global atmospheric change and what are
the informational needs in these programs that might be supplied by outside-funded
researchers?' And we need communication established as a on going situation."
R. Cicerone, NCAR
"I see tremendous opportunities here for exchange of information and to identify
needs. A good example of how EPA can have an impact on the total research com-
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R. Morgenstern, OPPE/EPA
munity is the EPA funding of Rand to do emissions scenarios. This was not being
done by other research agencies. There are another 15-20 such focused opportuni-
ties where EPA can do things to contribute to total effort.
"We must also, however, be building towards programs at EPA about the sys-
tems that are just coming into view. We should remember that we have only
thought about the earth as a system in very recent years. This idea is not very old
and we should not be ashamed of this. It has only been since WWII that we have
had much disposable income, education, and time to make these types of questions
meaningful. But they are coming into view and we will be helping each in many
ways, and EPA will be taking a major responsibility in this area."
R. Morgenstern, OPPE/EPA
"I would like to echo a sentiment somewhere between Steigerwald and the scientists.
EPA has a responsibility to study this issue very seriously. The challenge is to
make a link between the global importance and the everyday budget constraints
and problems.
"In the policy area, for example, the global atmospheric change adds a long-
range perspective. The ozone strategy will be impacted by global atmospheric
change in the long range. A second way that global atmospheric change information
can enter the policy debate is in selected issues where a decision is to be made and
where knowledge of the future of the sort discussed here is very important.
"In the air area, for example, where banning of a particular hazardous material
may be under consideration, the question of substitutes is raised. What kinds of
substitutes are available and will they have deleterious effects on the atmosphere?
"In terms of the research issue, it is easy to get bogged down in your budget,
my budget type questions, but this is an important area and it does need support,
and if nothing else the international community is likely to pick this up and it will
be an area of international debate in the next decade. EPA must play a leadership
role in that debate."
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J. Hoffman, OPPE/EPA
J. Hoffman, OPPE/EPA
"This meeting is to initiate the process and the process will be years in the making.
"There are immediate applications, however. For example, for air issues, Whit-
ten's work suggests that we may need modification of the treatment of photolytic
radiation in models, and that current treatment may not reflect the existing situa-
tion.
"EPA recently re-budgeted a lot of money to go after small hydrocarbon sources,
who are difficult and expensive to control, and in which we do not get a lot out
of. If Whitten's results are correct, this effort might not be doing the job. Are we
making an error in going after these small sources?
"Another example, is in the EPA mobile sources group. They put out stan-
dards for CO emissions. We have found that the rest of the world tends to follow
U.S. technology. Because of our reduction, the world has followed, leading to a
more rapid decrease in CO globally than had been estimated. What other types of
activities is EPA involved in like this?
"We need to consider the wisdom of our investments. For example, we are mak-
ing a big investment in trying to bring all the areas that are not in attainment into
attainment and to hold the ones in attainment where they are. Bromine is leaking
into the stratosphere, which will cause a more rapid depletion of 03. According to
Whitten's work, small changes in global temperature and in stratospheric O3 can
be as important in helping Nashville meet and sustain attainment as hydrocarbon
controls. In fact, it may be that the most important strategy for keeping Nashville
in attainment is to control bromine emissions. This might be done at a cost of
1/10,000 the cost of hydrocarbon controls in Nashville. But at present there are no
regulations on bromine. A lot of it comes from practice in fire fighting and thus a
simple modification of practice rules might significantly decrease bromine emissions.
"Other examples of the possible effects of EPA decisions are: biotechnology
areas-can we find different bugs that decrease methane production in cows?; tox-
ics decisions-are there tradeoffs between PERC and CFC 113? We may have a major
impact on global atmospheric change for getting rid of a small toxic risk like PERC.
We are in the process of regulating a whole bunch of solvents and nobody is ana-
lyzing how all these solvents are interrelated and what various tradeoffs in solvent
regulations may do to the stratosphere.
"We should be concerned about short-term vs. long-term planning and the U.S.
economy. For example, we spend a lot of time bringing all the locations that are
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D. Tirpak, OPPE/EPA
marginally outside of attainment into attainment. If, at the same time, we ignore
the areas that are in attainment, but that may slip out of attainment because of
long-term global changes, then we are going to find that we are very unproductive
as an agency and in marshaling the nation's resources.
"We have to justify the Agency's regulation expenditures to the nation. We can
not regulate anymore without good cause. Some scientists are telling us that it is
oxidants and not just acid rain that are killing the trees, or that a 1°C warming
and 3% ozone depletion means that ozone attainment is going to be difficult."
B. Dimitriades, ASRL/EPA
"EPA research is, rightly or wrongly, dictated by priorities and we [the research
group] do not set them, the regulatory part of EPA sets them. The priorities are
based on impressions that they build about the relative importance of various issues.
I personally have a concern as to whether there was enough of an impression made
on EPA policy makers. Is this a new program to replace something else, or is it a
new program in itself?"
M. McElroy
"The EPA decision maker must take the long view. EPA can not maintain a re-
sponsible view of the environment while ignoring that oxidants are going to change,
weather systems may change, and regulatory standards that are set on the basis of
historical data may be inadequate and outdated. The target is a moving target."
B. Steigerwald
"I may have possibly overstated it—as everyone has said—but a key point is that
the linkages to the regulatory program must be built better than they have been.
It is not enough to say that 'Aren't you being irresponsible not considering...'
Somehow the linkages have to built in a 'harder' way than they have been. You
are going to have to compete with existing problems. You have to say: 'Here is an
action. Here is what happens if it does or does not happen. Here is why it is more
important than something else'. "
D. Tirpak, OPPE/EPA
"I agree. We have only turned over a few stones in the course of this meeting,
and we have only looked at a few issues; we do not have money, or people, or time
to examine the issue in an adequate manner. We are in a chicken and egg sort
of situation. You are right, all those linkages have not been built. What we are
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Audience Comment
trying to do with this conference is to get enough recognition that there are a lot
of things to be looked at. How do we begin that process today? This is a historic
meeting. We have not had this type of dialogue about what kind of future we want
to look towards. People should not either feel invested or bad about where they
find themselves and where EPA stands. It happens to be where we are and the
question is 'How do we allow this issue to unfold as time goes on?'."
Audience Comment
Public understanding about this issue is very poor. How do we make these issues a
lot better known?
J. Hoffman
"What I would expect to see happen at EPA is that before we make decisions,
people examine the effect of the decision on the global issue. For example, people
working on methylene chloride regulations could ask 'What is going to happen when
we regulate? What will be the effects of the substitutes?' It is easy to ask this,
because in figuring out the costs of the action, they have to figure out what the costs
of the substitutes are. What is lacking is not that they do not have information,
but that they do not consider the effect that a proposed regulation may have on
the stratosphere. So the first thing we have to do in the Agency is to identify the
decisions that might be changed, not by spending more money, but by accounting
for global atmospheric issues in making these decisions. A priority of the Agency
then, should be to identify five or six regulatory programs that might be affected by
global atmospheric changes and to begin examining the decisions in light of existing
information."
R. Morgenstern
"We must focus on specific problems. What specific problems are underway at EPA
or are on the horizon at EPA that will be affected by global atmospheric change?
That is the way change occurs in the kind of political and bureaucratic situation in
which EPA operates."
M. McElroy
"Most of the issues we are discussing here are related to the use of fossil fuel. And
accepting the climate impacts we have heard discussed here might underestimate as
well as overestimate what is actually going to happen, it could be worse. What is the
response of the 'future thinker,' the gentleman at the top with the long-range view?
If we judge that the climate change that may occur is undesirable to disastrous,
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D. Winters, OPD/EPA
how are we going to deal with it? Are we going to make an instantaneous decision
to switch from fossil fuel to nuclear? How do you build into that fact that there is
a minimum time to make the switch—not less than 30 years—with an impact that
is going to occur on a shorter time scale. There are some very serious potential
problems that lie ahead. At the very least then let us understand as well as we
can what might happen because maybe there is someone with enough wisdom to
respond to the issue."
D. Winters, OPD/EPA
"I think the way we respond as an institution is not through a process of revolution,
that is, it is not through a process of making a major institutional change: 'Gee,
we have a major societal problem, we have to drop what we are doing and do
something else.' Instead, it comes through a series of incremental changes that build
momentum in terms of ways in which the institution begins to focus its direction.
That process is already under way at EPA and other agencies. The very fact that
we are having this meeting is evidence that the process is under way. We now have
the question of stratospheric change and chlorofluorocarbons fully institutionalized
and recognized as an issue in EPA. It exists not because there are particular groups
of managers within the Agency that want to support the work, but because the
institution has now blessed it as a piece of work that can go forward in a planned
time line. These things are the indications of that incremental change that lead to
a new focus.
"The discussion we have had here today relative to the full interrelated nature
of the atmosphere, as opposed to simply looking at acid rain or looking at it on a
regional scale, are things that most of the people who are working on these problems
are already aware of. Some of us are aware of this on a daily basis. But the ways
in which we begin to accommodate the complexity of the global atmosphere will
be incremental and gradual changes. I came to this meeting with most of the
basic convictions I have now, I come away a little supercharged. I go away with a
little better sense of targets of opportunity, a little greater drive—yes, I think I am
going to push a little harder here, I think I am going to shake things a little harder
there. This, I think, is the way the institution will respond and we will end up with a
greater and greater percentage of the movers and shakers in the Agency and outside
the Agency adopting these views. That is the best chance we have for success. If
we try to go for the fundamental revolutionary change, that, at best, happens if
one individual adopts that and it lasts as long as that individual is around. What
we are moving for is an institutional change. That will be difficult, because we
operate an institution that is ultimately making intuitive decisions. Sometimes,
we make intuitive decisions on counterintuitive problems. The accountability of
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M. McElroy
all the decision makers, in terms of their success or failure at making decisions,
is in the short term. That is a fundamental problem our society has: 'How do
people who are accountable in the short term, making intuitive decisions, deal with
a counterintuitive problem?' The main way we attempt to deal with this issue is to
institutionalize the problem so that it is spread over more individuals and several
different time lines.
"For the global atmospheric change problem, we are moving in that direction.
Are we moving there fast enough? The answer is probably no. Can we move faster?
The answer is probably yes. Can we move a lot faster. My own view is probably
not. The main value that comes from the exercise we have today and from the
times that we redo that exercise is that it helps refocus us on where it is we are
trying to get to, because we get lost in the day-to-day battles.
"So it is the gradual progress and when it is going in the right direction, to
recognize it and when it is going in the wrong direction, identify what direction it
should be going and help it move on through."
M. McElroy
"That is very useful. We need to distinguish, however, between the easy problems
and the really tough ones. When you pick the stratospheric problem, for exam-
ple, I think you pick a very easy one. That it was easy explains why the public,
political, and the regulatory response to the ozone issue was so positive from the
very beginning. It was basically because here was one of these complicated global
problems in which the answer was relatively simple: you regulate a few chemicals,
and impose alternatives, the public would not have to spend very much money, a
few industrialists would have to make adjustments. But it was really basically a
simple thing to do.
"I think it is important to tackle the tropospheric oxidant issue, because that
is a lot more complicated. And then, if you really want to go for the big one, take
on the climate issue because that is really a powerful challenge. Given what you
said, and I believe that what you described is the way in which we will proceed—in
a stepwise fashion, then maybe the people on the cutting edge in the scientific area
should be thinking about, in a worst case, how would we intervene to change the
climate, because we may actually have to. Maybe it is time we should give a little
thought about how you might do that, because the time scales involved here—the
time scales of global atmospheric change—are really becoming quite short compared
to natural rates of change [and while we wait to see what to do, the change may
already have taken place].""
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M. McElroy
I M. McElroy
"Thank you for attending. The meeting is adjourned."
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Paper 1
_ Emissions and Atmospheric Concentrations
by
Ralph Cicerone
National Center for Atmospheric Research
This presentation was based upon the following published paper, which has been reproduced with
permission of the American Geophysical Union. The authors' consent has been obtained.
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* Trace Gas Trends and Their Potential Role in Climate Change
• by
V. Ramanathan
IR.J. Cicerone
H.B.Singh
J.T. Kiehl
I
V. Ramanthan, R.J. Cicerone, H.B. Singh, and J.T. Ki eh\, Journal of Geophysical Research, Vol. 90,
• No. D3, Pages 5547-5566, June 20, 1985, copyright by the American Geophysical Union.
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Paper 1
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 90, NO. D3, PAGES 5547-5566, JUNE 20, 1985
Trace Gas Trends and Their Potential Role
in Climate Change
V. RAMANATHAN, R. J. CICERONE, H. B. SINGH,' AND J. T. KIEHL
National Center for Atmospheric Research, Boulder, Colorado
This study examines the potential climatic effects of the radiatively active trace gases that have been
detected in the atmosphere including chlorofluorocarbons, chlorocarbons. hydrocarbons, fluorinated and
brommated species, and other compounds of nitrogen and sulfur, in addition to CO2 and O3. A
one-dimensional radiative-convecuve model is used to estimate trace gas effects on atmospheric and
surface temperatures for three cases: (1) modern day (1980) observed concentrations are adopted and
their present trends are extrapolated 50 years into the future. These projections are based on analyses of
observed trends and atmospheric residence times; (2) the preindustrial to present increase in CO2 and
other trace gases are inferred from available observations; (3) a hypothetical increase of 0-1 ppbv is
considered to provide insights into the radiative processes. Trace gases other than CO2 are shown to be
potentially as important as CO2 for long-term climate trends. The relative importance of the 30 or so
trace gases included in this study depends on the problem under consideration. The inferred CO2
increase from preindustrial to the present causes an equilibrium warming of the model surface by 0.5 K,
which is amplified by 50% by CH4, CFC1, (Fll), CF2Clj (F12), and tropospheric ozone. For the
projected increase from year 1980 to 2030, the other trace gases amplify the estimated CO, warming of
0.7 K by about 110%: CFC13, CF2C12, ozone, and CH4 each contribute in the 0.1-0.2 K. range followed
by N2O, CHClFj (F22), CH,CC13, and CC14 in the 0.03-0.1 K range. Finally, on a per ppb basis, about
12 trace gases are identified to be important: CBrF3, C2F6 (F116), CHF3, and CF3O (F13) have
greenhouse effects comparable to those of CFCI3 (Fll) and CF2CI2 (F12). The narrow-band overlap
treatment and the accurate spectral and angular integration techniques employed in the present radiation
model enable quantitative interpretation of the differences between various published estimates for the
greenhouse effects of CFQ, and CF2C12. For the projected trace gas increase, we compute the strato-
spheric O, change by employing a photochemical model coupled to the radiative-convective model. The
O, change cools the stratosphere and the magnitude of the cooling is as large as that due to the
projected CO2 increase. Because of the 0,-induced stratospheric cooling and the surface warming due to
the greenhouse effect, the trace gas effects on climate are virtually indistinguishable from those of CO2.
1. INTRODUCTION
The release of chemicals into the atmosphere has grown
greatly over the last 50 years. Increased reliance on synthetic
chemicals, deforestation, biomass burning, and fossil fuel com-
bustion have all contributed to the observed perturbations of
trace chemicals in the atmosphere. One of the important po-
tential consequences of this chemical change is an alteration of
the earth's climate because trace chemicals modify the radi-
ation energy balance of the earth-atmosphere system. To date,
the climatic effects of future levels of CO2 have received the
most attention [e.g., see National Research Council, 1982,
1983; World Meteorological Organization, 1983]. However,
from the studies summarized by the World Meteorological
Organization [1982a] as well as subsequent publications
[Chamberlain el al., 1982; Alexandrov et al., 1981; Ramana-
than, 1982; Hansen el al., 1982; Wuebbles, 1983a], it can be
inferred that the combined effects of the other trace gases is to
warm the surface-troposphere system and the magnitude of
this warming in the future can potentially be as large as the
warming due to projected increases in CO2.
The study of climatic effects of other trace gases poses cer-
tain special problems. The difficulty encountered in examining
the effects of trace gases other than CO2 arises because they
perturb the radiation energy balance of the earth/tropo-
sphere/stratosphere system in a number of ways: (1) some of
'Also at SRI International. Menlo Park, California.
Copyright 1985 by the American Geophysical Union.
Paper number 5D0059.
0148-0227/85/005D-0059$05.00
the trace gases (e.g., CFCI3, CF2C12, and CHJ have strong
infrared bands in the 5- to 20-/im wavelength region, which
enhance the atmospheric opacity and contribute to the green-
house effect [e.g., Ramanathan, 1975; Wang et al., 1976]; (2)
addition of chemicals, such as CO and NO, even if by them-
selves they are not radiatively important, can alter the chemis-
try of the background troposphere, which in turn can perturb
the radiatively important gases, such as O3 and CH4 \_Hameed
el al., 1980]; (3) the IR cooling due to the increase in several of
the gases perturbs the stratospheric temperature, so that the
middle stratospheric chemistry is altered appreciably through
temperature-dependent reaction rales [Boughner and Ramana-
than, 1975]. The net effect of these chemical-radiative interac-
tions is a substantial perturbation of the stratospheric ozone
concentrations, which in turn modulates the solar and IR
fluxes to the troposphere. A summary of our current under-
standing of the above issues can be found by the World
Meteorological Organization [1982a], which also gives a
lengthy compilation of published studies on the problem;
hence these earlier studies will not be reviewed here.
The potential importance of the other trace gases provides
the primary motivation for the present study, which attempts
to examine the climatic effects of most (if not all) of the an-
thropogenic trace gases. The major objectives of the present
study are given below in the order in which they are discussed.
1. Characterize the trace gases, their observed abundances.
known sources, and sinks in the present-day atmosphere.
2. Based on current understanding of the observed trends.
estimate the future concentrations of trace gases, including
stratospheric ozone. This step, while it has numerous pitfalls.
5547
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5548
RAMANATHAN ET AL. : TRACE GAS CLIMATE EFFECTS
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RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
5549
is necessary for the discussions concerning the relative impor-
tance of the various trace gases.
3. From observational records and other considerations,
infer the preindustrial concentrations of trace gases.
4. Estimate the radiative effects of the trace gases and their
potentials for climate changes.
5. Clarify the sources for differences and discrepancies be-
tween published estimates for the trace gas radiative effects.
First, some comments are in order on the scientific necessity
of this study because several papers have been published on
the trace gas effects. None of the previous studies have includ-
ed all of the trace gases included in this study. The present
study uses new laboratory spectroscopic data made available
subsequent to the earlier studies; the present study relies heav-
ily on observed concentrations and trends for the trace gases
as opposed to the hypothetical concentrations and increases
assumed in most of the earlier studies. The Lacis et al. [1981]
study did use observed trends but was restricted to only the
effects of chlorofluorocarbons (CFCs), CH4, and N2O.
Chamberlain et al. [1982] included the direct effects of most of
the trace gases considered in this study, but inferred the tem-
perature changes from the radiative flux change at the surface
instead of the changes to the surface-troposphere system. It is
the radiative flux change to the surface-troposphere system
that governs the surface temperature change \_Manabe and
Wetherald, 1967; Ramanathan, 1981, 1982; Hansen et al.,
1982]. Furthermore, all of the above studies ignore strato-
spheric ozone changes due to CFCs.
For estimating their present-day radiative effects, we adopt
the observed concentrations as of 1980. With respect to pro-
jected increases, we extrapolate the present-day trends to SO
years into the future. This procedure enables us to determine
the relative importance of the various trace gases. Fur-
thermore, we examine quantitatively the validity of the opti-
cally thin approximation, an important issue because this ap-
proximation is employed by all studies to treat the radiative
effects of trace gases other than CO2, O3, N2O, and CH4.
For the purposes of this study, the word "climate" refers to
surface/troposphere/stratospheric temperatures. The temper-
ature changes are computed from a one-dimensional
radiative-convective model described by Ramanathan [1981].
The radiative-convective model provides a convenient frame-
work for examining the other trace gas effects, even though it
ignores several important feedback processes arising from at-
mospheric circulation, oceans, and the cryosphere (e.g., ice-
albedo feedback). Numerous one-, two-, and three-
dimensional climate model calculations have estimated the
surface wanning due to doubled CO2 (see summaries by the
National Research Council [1982, 1983], among several
others). Furthermore, the radiative effects of the other trace
gases (with the exception of stratospheric ozone changes) are
very similar to that of CO2. Hence one-dimensional model
estimates for the surface warming effects of the other trace
gases and that of CO2 (provided both are performed with the
same model) can be used to scale the effects for the more
realistic general circulation models (GCM), since numerous
GCM estimates for the CO2 effects are currently available.
2. OBSERVED AND PROJECTED CONCENTRATIONS
OF TRACE GASES
The earth's atmosphere currently contains trace gases with
atmospheric lifetimes that vary from much less than an hour
to several hundred years. The abundance of trace gases is
therefore dictated as much by their removal rates as by the
TABLE li>.
Assumed Premdustrial (Year 1880) Concentrations of
the Trace Gases
Trace Gas
C02
N26
Tropospheric O3
Stratospheric O3
CFC11 and 12
ecu
All others
Concentration
270 ppm
1.15 ppm
0.285 ppm
- 12.5%*
Same as present-day values
0.
0.
0.
*O3 concentration is altitude dependent. Uniformly smaller at all
altitudes from 0 to 12 km by 12.5%.
growth in sources. From a viewpoint of global climate effects.
species with extremely short lifetimes are unlikely to play an
important direct role. To project the concentration of each
species to year 2030, we have used a knowledge of the follow-
ing: (1) recent (1980) atmospheric concentration and recent
trend data if any; (2) nature of sources (man-made, natural.
etc.), relative strengths or budget for each gas; (3) growth in
natural as well as man-made sources due to projected human
activities over the next SO years; and (4) atmospheric lifetimes
of each species.
In what follows, we emphasize radiatively important gases
Table la briefly describes the lifetimes, dominant sources, and
sinks of trace chemicals that have been identified in the globa!
atmosphere. Many of these properties were listed earlier in an
extensive review of scientific literature {World Meteorologies
Organization, 19826]. For a large number of species where
reaction with hydroxyl radical (OH) is the principal removal
mechanism, lifetimes are estimated using an average OH con-
centration of 7 x 103 molecules/cm3 and an average global
atmospheric temperature of 265 K. While uncertain, this OH
average is consistent with the budgets of CH3CC13, CO, and
'*CO [Volz et al., 1981]. For species with lifetimes greater
than 20 years in Table la, removal is largely due to photolytic
decomposition in the stratosphere. For all of the chlor-
ofluorocarbons in Table la, lifetimes are determined based
only on stratospheric photolysis from the computations 01
Wuebbles [1981] and those summarized by the World
Meteorological Organization [19826]. Only oxygenated species
(O3, aldehydes) and CH3I absorb UV light in the troposphere
(A > 290 nm). The fully fluorinated species are not decom-
posed by UV light even in the stratosphere. Their destruction
by and large would occur in the mesosphere and ionosphere
from absorption of Lyman alpha and Lyman beta radiation at
altitudes above 70 km [Cicerone, 1979]. The lifetime of fully
fluorinated organics (Table la) can be in the 500- to 1000-year
range. Hydrogen is the only species in Table la where micro-
bial action at soil surfaces provides the major removal process.
Ozone destruction also occurs on all surfaces (e.g., soil, water.
and snow), but the mechanism of this destruction process is
not known.
In addition to providing source, sink, and lifetime infor-
mation. Table la also presents global average concentrations
of species for the atmosphere of year 1980. These data are
based on actual measurements that have already been summa-
rized in some detail [World Meteorological Organization
1982b].
It must be remembered that for species with lifetimes of less
than 10 years, significant horizontal (latitudinal) gradients can
exist. As an example, the ratio of northern to southern hemis-
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5550
RAMAN ATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
pheric average concentration is about 1.4 for CH3CC13 (r, = 8
years) and >2 for C2C14 (T, = 0.5 year). For short-lived
species (T, < 0.3 year), vertical gradients can also be expected.
These gradients have been taken into consideration, based on
available information, in developing the global averages
shown in Table la.
The year 2030 concentrations are projected to develop a
standard set of conditions, but a probable range is also includ-
ed. The year 2030 "best estimates" in Table la thus constitute
the "standard set." The range of likely variability associated
with this standard set is also presented in Table la.
In the following sections we discuss the information that
was utilized in developing the year 2030 projections. The year
1980 characterization is based exclusively on atmospheric
measurements.
2.1. Carbon Dioxide
The CO2 concentrations in the atmosphere have been mea-
sured to be increasing at a rate of approximately 1.5 ppm/yr
(see Figure 1.2 of the National Research Council [1983]).
Fossil fuel combustion is believed to be a major contributor to
this increase. Over the past decades, CO2 release rates due to
combustion have increased at a rate of about 4.3%/yr A
recent analysis [Rotty and Marland, 1980] supports a 2.4%/yr
increase in CO: emissions over the next 50 years. Only a
fraction (« 50%) of this input is expected to remain airborne.
Based on this analysis, Wuebbles [1981] described the CO2
concentration in ppm empirically.
[CO2] - 330.0*° 0036('- "73> 1975 <. t £ 2100
The CO2 concentration of year 2030 is computed to be 450
ppm. This projected concentration is consistent with available
scenarios based on more detailed considerations of energy
policies and the sources and sinks for CO2 [e.g., Smagorinsky,
1983, p. 278].
2.2. Chlorofluorocarbons (CFCs)
These chemicals came into major use in the 1960's and
initially exhibited a rapid growth (10-15%/yr). The most im-
portant CFCs to date have been CF2C12 (F12 or CFC12) and
CFClj (Fll or CFC11). The global emissions of the major
CFCs (F12 and Fll) actually declined somewhat from the
mid-1970*s through 1982 [Chemical Manufacturer's Associ-
ation, 1983]. Part of this decline may be attributed to a ban on
some nonessential usages (e.g., spray cans) of CFC's and due
to adverse economic conditions that have prevailed in several
industrial nations during this time. CFC emissions increased
sharply in 1983. Data for CFC13 and CF2C12 have been pre-
sented by Logan et al. [1981] and Cunnold et at. [1983a, &].
The use of CFC's in other more essential industries and in
previously less industrialized nations (e.g., refrigeration) is ex-
pected to grow. We estimate that a 3%/yr growth rate for all
of the relatively inert CFC's, i.e., Fll, F12, and C2C13F3
(F113), C2CI2F4 (F114), C2C1F5 (F115), and C2FS (F116), is a
reasonable scenario. The range of concentrations shown in
Table la is established based on a 0-5%/yr growth. For
CHC1F2 (F22), less severe controls are anticipated, since 60%
of the emitted amount could be removed in the troposphere. A
5% growth rate with a 3-7%/yr range is used for compu-
tations presented in Table la.
2.3. Chlorocarbons
All chemicals (except carbon tetrachloride) in this category
have atmospheric residence times of less than 10 years. Be-
cause of the toxic nature of many of these chemicals [Surgeon
General, 1980], a rapid growth of emissions cannot be ex-
pected. Also, because of relatively fast removal rates, a dra-
matic buildup of these in the global atmosphere is not likely.
Methyl chloride (CH3Q) is the most abundant natural chlo-
rine carrier; it appears to arise mostly from the world's oceans
[Lovelock, 1975; Rasmussen et at., 1980; Singh et al., 19836],
although relatively small man-made sources are known to
exist [National Academy of Sciences/National Research Coun-
cil, 1976] and inadvertent release is possible due to biomass
burning and/or reactions between organic matter and chlori-
nated water, as in rivers. Thus it is unlikely that the sources of
atmospheric CH3C1 will increase substantially, and we indi-
cate in Table la little or no growth in its atmospheric con-
centration by the year 2030. It is worth noting, however, that
if tropospheric OH (dominant sink for CH3C1) levels decrease,
CH3C1 concentrations could increase: see methane discussion
below.
Methyiene chloride (CH2C12), a relatively short-lived chemi-
cal, is a popular solvent which is expected to undergo rapid
growth unless found to be toxic in the future. Its virtual non-
involvement in the stratosphere and its lack of toxicity assures
it an excellent growth potential. On the average, a 5%/yr
(range of 3-7%/yr) growth rate appears a reasonable projec-
tion. This growth rate is also consistent with the growth in the
last decade [Bauer, 1979].
Over the last decade, the methyl chloroform (CH3CC13)
market has grown at a rate of about 15%/yr. Although it may
make an increasing contribution to stratospheric ozone deple-
tion, its market is expected to grow rapidly and a growth rate
similar to that of CH2C12 is projected. Methyiene chloride
along with CH3CC13 are the most likely chemicals to be used
for substitution as other more toxic chemicals (e.g., C2HCI3,
C2C1J are more severely controlled.
Carbon tetrachloride (CC14) is the longest lived atmospheric
chlorocarbon, and its historical emission pattern is more com-
plicated [Singh et al., 1976]. Since the early 1960's, when the
toxic effects of CC14 became evident, direct emissions virtually
ceased. The present atmospheric CC14 concentration growth
rate is between 2%/yr [Simmonds et al., 1983] and 5%/yr
[Singh et al., 1983a]. Current emission levels of CC14 could
grow at a rate of about 2% (0-3%/yr) over the next 50 years,
in a manner similar to those of fluorocarbons because a large
fraction of CC14 emitted is during its use in fluorocarbon pro-
duction.
2.4. Fully Fluorinated Species
Three chemicals in this cateogry have been measured at
enough locations to characterize global concentrations: CF4
(F14), C2F6 (F116), and sulfur hexafluoride (SF6). These three
man-made species are relatively stable chemicals with atmo-
spheric residence times over 500 years. These species are not
chemically involved in atmospheric processes below about 50
km. The sources of CF4 and C2F6 are not at all clear. Inad-
vertent emissions from carbon-electrode processing of min-
erals [Cicerone, 1979] are likely, specifically from aluminum
processing [Penkett et al., 1981]. Assuming a 2-3% steady
growth rate of the aluminum industry over the next 50 years.
the year 2030 concentrations of CF4 and C2F6 are shown in
Table la. Indeed, a temporal increase of about 2%/yr in CF4
concentrations has been measured recently (R. J. Cicerone et
al., unpublished manuscript, 1985). This rate of increase is less
than that deduced by Cicerone [1979]. SF6 is a dielectric
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RAMANATHAN FT AI_: TRACE GAS CLIMATE EFFECTS
5551
agent used in electrical equipment. Its concentrations are also
estimated based on a 2-3%/yr growth rate.
2.5. Nitrogen Compounds
The most important nitrogen-containing chemical from a
climatic viewpoint is N2O. The 1980 atmospheric con-
centration is 301 ppb (0.8 ppb less in the southern hemisphere)
as measured by Weiss [1981]. Contrary to many previous
estimates, it is now accepted that N2O has a very long atmo-
spheric lifetime (> 100 years) with stratospheric photolysis the
only known removal process. Microbial production in soils
and oceans has been found to be a source as well as a sink of
N2O. The net contribution of soils and oceanic microbes to
the atmospheric budget of N2O is not yet clear; Weiss [1981]
calculated that the total annual source of atmospheric N2O is
about 3 x 1012 g. Over a 4-year period (1976-1980), Weiss
measured a rate of increase of 0.2%/yr for N2O con-
centrations. Further, he constructed a mathematical model
which used an exponentially increasing N2O source function
to fit his measurement data. More recent data (R. F. Weiss,
private communication, 1984) continue to fit Weiss' math-
ematical model. The recent record shows more uniformity
among data from measurement locations than was apparent
in the 1976-1980 record. From the Weiss [1981] mathemat-
ical model, we estimate the year 2030 concentration to be 375
ppb and a likely range of 350-450 ppb. This range reflects the
considerable existing uncertainty as to the identity of the N2O
sources most responsible for the observed N2O concentration
trend, e.g., coal combustion and microbial production of N2O
through nitrification and denitrification of inorganic nitrogen
fertilizers applied to soils. Even with the recent expansion of
Weiss's data base, the record is still not adequate to dis-
tinguish between these two sources (R. F. Weiss, private com-
munication, 1984). In the future, the atmospheric residence
time of N2O could decrease if ozone concentrations decrease
above 30-km altitude (Table 2); increased UV light levels just
below 30 km would increase the rate of N2O photolysis. Also,
while we have adopted Weiss's [1981] semiempirical method
for projecting future N2O concentrations, we note that there
remain many questions about sources of atmospheric N2O.
For example, if we employ a slower rate of increase of fossil
fuel combustion than did Weiss, we arrive at a reduced lower
limit for N2O in that year, i.e., 350 ppb. Further, while many
studies suggest that only 1-2% of all fertilizer N is released as
N2O in the year following fertilization, much higher release
rates are possible especially from fertilized organic-rich soils
[Duxbury et ai, 1982].
Two other nitrogen-containing gases, hydrogen cyanide
(HCN) and peroxyacetyl nitrate (PAN), have now been ob-
served in the nonurban troposphere. Infrared absorption
measurements with the sun as the source have shown that
HCN is present in the northern hemisphere (NH), midlatitude
troposphere, and the entire NH stratosphere at about 160 ppt,
with little, if any, altitude gradient up to the midstratosphere.
These measurements, the atmospheric chemistry and possible
sources of HCN, have been discussed by Cicerone and Zellner
[1983]. In Table la we show no increase in HCN con-
centration by 2030, but only because there are no data on its
temporal trends and because the identities of its sources are
uncertain. Similarly for PAN, we can do little more than note
that it has been detected recently in the nonurban tropo-
sphere, occasionally at concentrations of 400 ppt. While there
is reason to believe that its global concentrations are nonne-
gligible [Singh and Solas, 1983] and that its precursors (NOX,
TABLE 2. Computed Stratospheric Ozone Changes From
1980 to 2030
Altitude
10
16
22
26
28
30
32
34
36
38
40
44
50
Percent Ozone
Change
3.8
4.1
4.5
2.0
-1.2
-6.1
-13.4
-22.6
-31.1
-36.7
-37.9
-27.4
-5.4
The calculations account for the feedback between temperature
and chemistry within the model stratosphere (above 10 km) and
employ the chemistry model of Cicerone et al. [1983] and the
radiative-convective model used in this study.
ethane, and propane) might increase in the future, there is too
little information to permit an estimate of PAN's future con-
centrations.
The other nitrogen species (NH3 and NO,) have extremely
short lifetimes (0.5-5 days). The global distribution of these
species, even for the 1980 atmosphere, is poorly characterized
IKley et al., 1981]. As expected with species of such short
lifetime, a great deal of variability in atmospheric levels is
evident. Although anthropogenic sources of NO, in the tropo-
sphere (auto and aircraft exhaust, high-temperature combus-
tion, soil emissions) may double over the next 50 years, it is
unclear if this change would increase the atmospheric abun-
dance of NO, outside the range of present uncertainty.
2.6. Ozone
The climatic effects of ozone change depend very strongly
on whether tropospheric or stratospheric ozone is being al-
tered [Ramanathan and Dickinson, 1979; Wang, 1982]. Hence
we discuss separately the tropospheric and stratospheric O3
trends.
Focusing first on ozone in the free troposphere (above the
planetary boundary layer), there are data and theories that
suggest that ozone concentrations are increasing with time. A
number of investigators [Logan, 1982; Angell and Korshover,
1983; Bojkov, 1983] have reviewed and analyzed data from
many ozone-measuring stations supported by Umkehr data.
Logan finds that at Uccle (Belgium) at 500- and 700-mbar
levels, ozone increased by about 1%/yr between 1969 and
1980. Similarly, at Hohenpeissenberg (Germany) at the 500-
and 700-mbar levels, ozone increased by 15% from 1967 to
1981. However, at Payerne (only 500 km away) at these same
altitudes, no such trend was observed. A preliminary analysis
of data from nine NH ozonesonde stations has been per-
formed by Liu et al. [1980]. Eight of nine stations show ozone
increases (8 + 4%) from 1969 to 1977 in the middle tropo-
sphere, a result consistent with that reported by the National
Aeronautics and Space Administration [1979] for the 2- to
8-km region. These ozone increases are not mirrored in sur-
face measurements where no trends have been observed or in
the southern hemisphere (SH), where one station. Aspendale.
shows a decrease in tropospheric ozone 1965-1978 [Liu et al.,
1980]. Based on available data, one cannot distinguish a clear
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5552
RAMANATHAN ET AI_: TRACE GAS CLIMATE EFTCCTS
trend, but an upward trend in tropospheric ozone (2-8 km)
seems to have occurred [Angell and Korshover, 1983].
Other considerations suggest that tropospheric ozone is in-
creasing in the northern hemispheric troposphere. First, Fish-
man et al. [19796] presented evidence that there is appreciable
in situ photochemical production of ozone. This evidence in-
cludes the fact that ozone is more concentrated in the NH
even though there should be faster uptake at the earth's sur-
face in the NH. Also, Fishman et al. noted that there are much
stronger seasonal variations in the NH production of ozone.
Recent models of tropospheric chemistry that embody this
theory predict that tropospheric ozone has already increased
and will continue to do so, especially in the NH. Due to
increases in combustion releases of NO*, CO, H2, and in-
creased CH4, Logan et al. [1978] calculated that tropospheric
O3 can increase greatly, even 100% in the next century, es-
pecially in the middle and upper troposphere. Liu et al. [1980]
focused on the consequences of NOX injections from high
flying aircraft. In their view, most photochemical production
of ozone occurs above the boundary layer, so direct injections
by aircraft are especially effective and ground-level NO,
sources may not lead to much photochemical ozone in the free
troposphere. Liu et al. calculated that a 14-30% ozone in-
crease should have occurred in the NH middle and upper
troposphere between 1970 and 1980. A more recent analysis of
tropospheric ozone production by human activities is given by
Crutzen and Gidel [1983].
To summarize the two paragraphs above, there is some
observational evidence that NH tropospheric ozone has in-
creased by 0.8-1.5%/yr since about 1967; this evidence is
compelling but not conclusive. Photochemical theory applied
to emission histories and projections of combustion NO* sug-
gests that a 1 %/yr increase in NH tropospheric ozone is possi-
ble. In the SH, given the smaller anthropogenic influences, O3
might not change at all (NH anthropogenic NOT, a key in-
gredient for photochemical production of O3, should not in-
fluence the SH). For our globally averaged radiative calcula-
tions, we will adopt an annual growth rate for tropospheric
ozone of 0.25%/yr, although values from zero to 1.5%/yr
appear possible, at least for the NH. A nominal 40 ppb of
tropospheric ozone, for example, becomes 45 ppb in the year
2030 with a 0.25%/yr growth rate; a 1%/yr growth rate would
result in 64 ppb in 2030. Note that we do not assume a con-
stant mixing ratio with altitude in our calculations. Table la
provides the adopted altitude variation in the model calcula-
tions which are based on the hemispherical, annual mean
ozone data described by Ramanathan and Dickinson [1979].
Stratospheric ozone is also thought to be susceptible to
perturbing influences, including man-made chloro- and chlor-
ofluorocarbons, increasing CH4 and N2O concentrations (see
below) and decreases in stratospheric temperature due to in-
creasing CO2. For our stratospheric ozone profile for the year
2030, we have taken the computed ozone perturbations listed
in Table 2. These ozone changes were calculated with the
basic chemistry model of Cicerone et al. [1983] with fixed-flux
lower boundary conditions for N2O, CH3C1, and CC14 but a
fixed mixing ratio (1.6 ppm) for CHt. As discussed later, the
present computations account for the feedback between tem-
perature and chemistry. A refined diurnal averaging scheme
was employed; it led to less nonlinearity in the ozone-chlorine
response curve than reported by Cicerone et al. The ozone
change shown in Table 2 was obtained by increasing the flux
of CFC13 (Fll) and CF2C12 (F12) till the stratospheric mixing
ratio of inorganic chlorine (C1X) reached a value of 9.4 ppb for
the year 2030. A C1X value of 9.4 ppb for year 2030 results
from a 3%/yr increase (1980-2030) in emissions of CF2C12,
CFC13, CH3CC13, C2C13F3, C2C12F4, CCU, and CHC1F2 (D.
]. Wuebbles, private communication, 1984; also see Wuebbles
[1983ft]). This uniform 3% growth rate is consistent with
those adopted in Table la, except that Table la shows a 2%
growth rate for CC14 and a 5% rate for C2H3C13. In order to
place this slight inconsistency in proper perspective, we note
that the calculated future stratospheric C1X mixing ratios
depend, not only on future emissions, but also on the vertical
eddy-mixing coefficient in the (one-dimensional) model. For
the 1980 reference atmosphere, we took C1X = 2.5 ppb.
The ozone changes shown in Table 2 account for the feed-
back between temperature and chemistry. For this purpose,
we iterated the temperature changes computed by the climate
model (described later) with the ozone change resulting from
the chemistry model. The temperature change calculations in-
clude not only the ozone changes but also the increase in all
other trace gases shown in Table la (see the "Best Estimate"
column). This temperature feedback reduced the computed
ozone changes by a nonnegligible amount. For example, with-
out the temperature feedback, the computed ozone change at
a few of the levels are +4.2% (10 km), +5.1% (20 km),
-7.3% (30 km), -45% (40 km), and -36% (44 km); these
changes can be compared with those in Table 2.
Our usage of a fixed mixing-ratio lower boundary condition
for CH4 actually assumes an increasing flux of CH4 (to main-
tain the fixed mixing ratio as C1X increases). A fixed-flux
boundary condition for CH4 would have led to larger ozone
changes than those shown in Table 2. Beyond the year 2030,
even larger ozone changes are possible \_Prather et al., 1984].
In the present paper, we have neglected stratospheric ozone
changes due to the projected CH* and N2O increases shown
in Table la. It should also be stated that model calculations of
ozone changes below 30 km are plagued with uncertainties.
Accordingly, model results have fluctuated over the past 10
years or so [see, e.g., National Academy of Sciences/National
Research Council, 1982].
2.7. Methane (CH4) and Carbon Monoxide (CO)
The most abundant atmospheric hydrocarbon, methane,
was present at about 1.65 ppm in the NH in 1980; a con-
centration about 6% lower characterized the SH. More rele-
vant for our present purposes, atmospheric CH4 con-
centrations are known to be increasing globally. Between early
1978 and early 1981, concentrations increased by (2±0.5)%/yr
as measured by Rasmussen and Khalil [1981] and by 1-
1.5%/yr as measured by Blake et al. [1982]. Ehhalt et al.
[1983] have reviewed these and other data on atmospheric
methane and conclude that its concentration increased by
about 0.5%/yr between 1965 and 1975 and by 1-2%/yr be-
tween 1978 and late 1980. Further, from trapped air in dated
ice cores, Craia and Chou [1982] have deduced that CH4
concentrations have approximately doubled in the last 350
years with a greater rate of increase in the last century. It is
not clear why these increases have occurred, i.e., which of the
methane sources have increased or even if the atmospheric
sink of methane (oxidation by OH reaction) has decreased.
Arguments for increasing sources of methane are favored by
13C data [Craig and Chou, 1982]. Principal sources of atmo-
spheric methane appear to be enteric fermentation in rumi-
nant animals, release from organic-rich sediments below shal-
low water bodies and rice paddies, and quite possibly, pro-
duction by termites and biomass burning. Also, methane re-
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5553
lease in mineral, oil, and gas exploration and gas transmission
is growing. Clearly, to be able to predict future levels of atmo-
spheric methane, it is necessary- to know the relative impor-
tance of the various methane sources and their trends. If, for
example, rice agriculture is a dominant source, then trends in
cultivated area, plant-strain proportions, irrigation, and multi-
ple cropping and fertilization practices must be discerned as
they affect methane release.
The dominant sink of atmospheric methane, tropospheric
gaseous OH, may not be unchanging. Increased levels of tro-
pospheric CO or of CH« itself can suppress OH con-
centrations, as has been noted by several authors. CO exhibits
large hemispheric differences; these patterns and our knowl-
edge of CO sources are reviewed by Logan et al. [1981]. Re-
cently, Khalil and Rasmussen have reported evidence from
measurement (in Oregon) of dramatic (6%/yr) increases of at-
mospheric CO between 1979 and 1983. On the other hand, W.
Seiler (private communication, 1984) has measured little or no
change (^ 1 %/yr) in CO at several stations in both hemi-
spheres. For a clean, background troposphere a CO increase
of x% leads to a depletion of tropospheric OH of x/(4 ± 1)%,
depending on altitude and various model assumptions, ac-
cording to A. M. Thompson and R. J. Cicerone (unpublished
manuscript, 1984). Combining the (1) source analysis by Logan
et al. [1981], (2) information on trends of these sources (e.g.,
fossil fuel usage, oxidation of anthropogenic hydrocarbons),
and (3) the CO data mentioned above, it is clearly possible
that CO will increase by 1-2%/yr through 2030 A.D. Such an
increase could cause CH* concentrations to increase faster
(through OH suppression) than if only CH4 source increases
were considered. Because of the spectral locations of the ab-
sorption of CO, the CO increase itself is not of interest here.
Its effects on the atmospheric levels of OH, CH4, and O3
could be very important.
Lacking all the detailed information necessary to under-
stand the presently documented rate of increase of atmospher-
ic CH4 concentrations and to predict the future, we estimate
that CH4 will increase by 0.75%/yr between now and 2030;
this would lead to a globally averaged CH4 concentration of
2.34 ppm in 2030. Rates of increase of 1.5% and 0.25%/yr
would lead to 3.30 and 1.8S ppm in 2030, respectively, as listed
in Table la. Beyond the year 2030, when the release of
continental-slope sediment methane clathrates might occur
due to oceanic wanning [Revelle, 1983], faster methane in-
creases are possible.
2.8. Nomethane Hydrocarbons
In this category we include alkanes, alkenes, alkynes, alde-
hydes, ketones, and H2. We pay little attention to simple aro-
matic compounds. By contrast with the situation for methane,
there is too little information available on the concentrations,
distributions, and sources of these compounds (except for
C3H2 and H2) to justify projections of future concentrations.
For acetylene (C2H2), fossil fuel burning (e.g., internal com-
bustion engines, oil-fired heaters) is a known source; its atmo-
spheric residence time is about 4 months, and no significant
biological sources are known yet [Rudolph and Ehhalt, 1981].
If its sources are wholly anthropogenic, an annual increase of
1-2% would be a reasonable guess. For ethane (C2H6), ethyl-
ene (C2H4), propane (C3H8), and propene (C3H6) the existing
atmospheric and oceanic surface water data suggest that there
are natural as well as anthropogenic sources [see, e.g., Rudolph
and Ehhalt, 1981, and references therein]. Fugitive emissions'
from oil and gas wells and transmission lines are likely, of
course. The state of our measurement data base for higher
hydrocarbons, aldehydes (present as oxidation products of hy-
drocarbons), and acetone is discussed by Penkett [1982].
2.9. Sulfur Compounds
Carbonyl sulfide (OCS) is the most abundant gaseous sulfur
carrier in the atmosphere. It is nearly uniformly distributed
with a measured average concentration of 0.52 ppb. Turco et
al. [1980] have examined the sources and sinks of OCS. While
there are many remaining questions, they propose that up to
50% of the total source is anthropogenic. If so, OCS con-
centration could increase in the future, but our present under-
standing of OCS sinks and its atmospheric residence time is
not very complete. No measured trend in OCS concentration
is available at this time. Considering the lack of such data and
the uncertainties about OCS sources and sinks, we cannot
project other than a constant OCS abundance in Table la.
Sulfur dioxide (SO2) is a notorious atmospheric constituent
because of its role in acid deposition. In continental boundary
layers where its principal source is combustion of S-contaming
fuels, its concentrations are often 10 ppb. Above the boundary
layer its concentration is of order 100 ppt [Marouiis et al..
1980]; its presence there is probably due to escape from the
boundary layer below, and to oxidation of other species, e.g..
OCS, CS2, and CH3SCH3. Similar concentrations have been
measured in the marine boundary layer [Herrmann and
Jaeschke, 1984]. Near major anthropogenic SO2 sources its
atmospheric residence time is about 1 day (due largely to
gas-to-particle conversion); in the higher troposphere in clear
air its residence time is up to 1 week. Because of its very short
lifetime and the uncertain future of SO2 emission, it is not at
all clear that SO, concentration will increase in the future.
Dimethyl sulfide (DMS) is now known to exist in the oceanic
boundary layer; it appears to have microbial sources in
oceans that provide a significant DMS flux to the marine
atmosphere [Andreae and Raemdonck, 1983]. Because this na-
tural source appears to be the major DMS source and because
of the short (~ 2 days) atmospheric residence time of DMS, we
project no growth in its atmospheric concentrations.
Carbon disulnde (CS2J is known to be present in back-
ground surface air at concentrations that vary from 0.03 to
0.08 ppb. However, it is virtually undetectable in the free
troposphere. Excited-state oxidation [Wine et al., 1981] can
be an important removal process. Oceans may be a major
source. No growth projection in CS2 concentrations can be
proposed reliably at this time.
2.10. Brommated and lodated Species
Only a handful of species in this class have been measured
in the nonurban atmosphere. The species of interest are bro-
minated and iodated methane- and ethane-series molecules
methyl bromide (CH3Br), methylene bromide (CH2Br2), bro-
moform (CHBr3), bromotrifluoromethane or (F13B1, CBrF3).
methyl iodide (CH3I), and dibromoethane (C2HJBr2, or ethyl-
enedibromide, EDB). CH3Br is apparently a natural species
[Lovelock, 1975; Singh et al., 19836]. Man-made emissions
have the potential to perturb its global background, but only
slightly. Methyl iodide is essentially all natural and, given its
concentration, is predicted to remain unchanged. CHBr3 and
CH2Br2 have been measured only recently [Berg et al., 1984],
and too little is known about their sources to permit reason-
able future projections. CBrF3 (F13B1) and ethylene dibro-
mide are exclusively anthropogenic. A continued shift toward
nonleaded gasoline could offset growth that may occur in fu-
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RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
migation applications of ethylene dibromide. Because of its
high carcinogenic potential, a rapid growth is not likely to be
permitted in any case. CBrF3 (used as a fire extinguisher) is
the only brominated organic whose sink is primarily in the
stratosphere (where bromine atoms can be efficient ozone de-
stroyers). Despite its very low present abundance it can
become an important carrier of organic bromine within the
next 50 years. Inorganic species such as HBr, HI, BrO, IO,
and NOBr are not discussed here because they are as yet
undetected in the atmosphere. Their residence times are prob-
ably 5 days or less, and future trends are difficult to predict.
3. PREINDUSTRIAL ERA CONCENTRATIONS
OF GREENHOUSE GASES
It is important to ask if CO, and the other trace gases
should already have caused a global warming. It is very diffi-
cult, if not impossible, to answer this question for at least two
reasons: (1) there are no direct data on the trace gases of
interest from, say, the 1850-1940 time period, and (2) there
should be a significant time lag between any increased atmo-
spheric radiative forcing and increased global temperatures,
due to oceanic heat capacity. To allow at least a rough esti-
mate of the size of the effect due to increased trace gas con-
centrations from about 1880 until 1980, we will attempt to
estimate the 1880 concentrations of methane, nitrous oxide,
chlorofluorocarbons, CC14) and tropospheric ozone. The pro-
posed preindustrial concentrations of the trace gases are
shown in Table Ib.
For CO2, the National Research Council [1983] study sug-
gests that the most likely preindustrial value is between 260
and 290 ppm. For this study, the preindustrial concentration
of CO2 is assumed to be 275 ppm.
For CH4, the data of Craig and Chou [1982] show that
CH4 has increased monotonically for the past 400 years; these
data are CH4 concentrations in air trapped in dated Green-
land ice cores. Craig and Chou noted that there is as much as
a 90 year uncertainty in the age of this air, depending on
whether air moved freely throught the firn phase of the snow
above the firn-closure depth. If the air at the 90-year firn level
was zero years old, then the CH4 concentration in the year
1880 was about 1.05 ppm. If the air there was not so young,
the Craig and Chou data show that the CH4 concentration in
1880 had to be over 1.05 ppm. If, for example, the air in
90-year old ice at this site were 50 years old instead of zero
years old, the implied 1880 CH4 concentration would be 1.10-
1.15 ppm in 1880. We assume that the 1880 CH4 level was
1.15 ppm.
For nitrous oxide, there are no direct data from pre-1900;
indeed, N2O was discovered in the atmosphere only in 1938.
Modern data from 1976-1980 and from 1961-1974 have been
used by Weiss [1981] to estimate a preindustrial atmosphere
N2O concentration of 281-291 ppb. Accordingly, we assign a
value of 285 ppb to N2O for the year 1880.
The chlorofluorocarbons and fluorocarbons (CC12F2,
CC13F, and the other compounds listed in Table 1 are almost
certainly of exclusive and post-1940 anthropogenic origin [Afa-
tional Academy of Sciences/National Research Council, 1979].
Therefore we estimate that each of them was absent from the
1880 atmosphere.
Carbontetrachloride is more interesting. It is known to be
produced by marine organisms [see, e.g., Fenical, 1982], yet its
mid-1970's (and present) concentration can be explained by
anthropogenic emissions [Singh et at., 1976]. Because of the
apparent unimportance of current natural sources, we will
assume that it was essentially absent from the 1880 atmo-
sphere.
Of the important greenhouse gases, tropospheric ozone is
most difficult for which to estimate differences between
present-day concentrations and those of one century ago. The
surplus of NH over SH ozone, the more pronounced seasonal
cycle in the NH ozone data, the strong theoretical case for
excess ozone production in the industrialized NH and the
hints of a positive trend since 1967, all imply that there was
less O3 in the 1880 NH troposphere. Detailed examination of
these and other factors [see Levy et al., 1985] does not allow
one to state with confidence that the hemispheric or global
background tropospheric ozone is strongly controlled by
photochemical reactions (such as those between hydrocarbons
and nitrogen oxides to produce ozone). For example, there is
evidence that the NH troposphere receives perhaps 3 times as
much ozone from the stratosphere as does the SH tropo-
sphere. One would predict higher NH concentrations from
this meteorological input of ozone, although the higher
surface-destruction rates in the NH would offset some of the
additional input. Perhaps 50% more ozone is observed in the
NH tropics than in the SH tropics (0- to 12-km altitude;
Fishman et al. [19796]) and 25-50% more in the midlatitudes
of the NH at 800-mbar pressure levels than at corresponding
SH locations. Another feature of ozone in the NH midtro-
posphere, the east-west gradient over North America
[Chatfield and Harrison, 1977], appears to be evidence for
photochemical production over continents. We assume that
half of the difference between NH and SH is due to anthropo-
genic emissions (and that 1880 emission of NOX and hydro-
carbons was negligible compared with those in 1980). Even
with these assumptions, one is left with uncertainty about ver-
tical profiles. In the upper troposphere, there is more influence
from the stratosphere, but there is also significant existing
potential for human impact by direct injections from aircraft
[Liu et al., 1980]. As a very rough estimate, we will guess that
there was 25% less ozone in the 1880 NH troposphere than in
1980 NH troposphere and that SH tropospheric ozone did not
change during that century.
4. DESCRIPTION OF THE CLIMATE MODEL
The direct radiative effects of trace gases are included in this
study. The effects due to altered chemistry are included ex-
plicitly as far as stratospheric O3 perturbation is considered
and implicitly with respect to tropospheric O3, i.e., projected
O3 increases can be considered to arise from the projected
increases in hydrocarbons, CO, and NO. With respect to the
feedback effects, this study accounts for troposphere/
stratosphere radiative interactions and the feedback between
temperature and chemistry within the stratosphere. The
climate-chemistry interactions in the troposphere and the pos-
sible effects of temperature changes on stratospheric H2O are
ignored. Both of these feedback effects, while they may be
relatively smaller than the direct radiative effects would re-
quire coupled photochemical climate models [Callis et al.,
1983].
A brief description follows of the radiative-convective model
and the source for the spectroscopic data used for the compu-
tations.
4.1. Radiative-Convective Model
The one-dimensional radiative-convective model described
by Ramanathan [1981] is adopted. This model, hereafter re-
ferred to as model R, has a surface boundary layer which
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RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
explicitly allows for the surface-atmosphere exchange of latent
and sensible heat and also solves for the boundary layer mois-
ture [Ramanathan, 1981, equations 17-20, Figure 7]. The stan-
dard radiative-convective models [e.g., Manabe and We-
therald, 1967; Ramanathan and Coakley, 1978] ignore these
processes and do not treat explicitly the exchange of latent
heat flux between the surface and the free atmosphere.
The boundary layer moisture and hence the relative humidi-
ty are explicitly computed in the model, but the tropospheric
relative humidity is prescribed as discussed by Ramanathan
[1981]. The mass mixing ratio of H2O above 12 km is pre-
scribed to be 2.5 ppm. Because of the explicit treatment of the
boundary layer, the model R computes the surface temper-
ature and the surface air temperature. Standard radiative-
convective models compute only one temperature for the
lower boundary which can be interpreted as an average of the
surface and surface air temperature. In model R the surface air
temperature change is larger than that of the surface temper-
ature change by about 10-13%. This point should be noted
when comparing the present calculations with the published
results.
4.2. Radiation Model and Spectroscopic Data
The trace gases, their longwave band centers, and the
adopted band strengths are shown in Table 4. The treatment
of H2O, O3, CO2, and CH4 are as described in model R. For
CO2, one of us (J.T.K.) incorporated the more detailed band
model of KieM and Ramanathan [1983] in model R. The sur-
face warming due to doubled CO2 estimated with the detailed
CO2 scheme was in excellent agreement (within 5%) with that
estimated from the somewhat simpler scheme in model R. For
CH4, model R employs the Donner and Ramanathan [1980]
band model. Although the band strength adopted in model R
is stronger than the current accepted value by about 35%, the
band model parameters were fit to give agreement with lab-
oratory absorptances. Hence the CH« radiative forcing esti-
mated by this band model agrees within 5-10% of that esti-
mated from a 5 cm"' spectral resolution narrow band model
which employs recent [Rothman et al., 1983] line data. Nu-
merous modifications were incorporated in model R to treat
the effects of the minor trace gases included in this study and
these modifications are described below.
N2O. The R scheme used the Donner and Ramanathan
[1980] band model scheme. We have retained this scheme, but
included the following N2O bands that were ignored by
Donner and Ramanathan [1980]: the two-band systems cen-
tered at 1168 cm"', one of which is the 2v4 band of the four
isotopes with bandstrength 8.5 cm"' (cm atm)~' STP and the
hot bands of the four isotopes with band strength 1.5 cm"1
(cm atm"') STP. Although these bands are considerably
weaker than the fundamental v, band system centered at 1285
cm"1, they contribute as much as 20% of the v, band system
to the surface warming due to N2O. This disproportionately
large contribution by the weak bands arises because N2O is
almost in the strong line limit, and hence the opacity scales as
the square root of the band strength. Hence for gases whose
concentration are large and their band strengths are suf-
ficiently strong that they are in the strong line limit, great care
must be exercised in including all the bands whose strengths
are smaller by as much as 2 orders of magnitude than the
strong fundamental band. This is the reason why the present
model incorporates many isotopic and hot bands of trace
gases such as CO2, N2O, and CH4.
Other trace gases. The band absorption A is expressed aj>
/i/".
.V
I/l-l
n
1*1-1
ID
(2)
(3)
(4)
where Acu is the band width in cm"l, S is the band strength in
cm"1 (cm atm)"1, w is the absorber amount in cm atm. The
above procedure of expressing the band transmission as a sum
of transmission functions averaged over pseudo-spectral inter-
vals i with weighting functions / and fc, is essentially the
exponential-sum fitting method described by Wiscombe and
Evans [1977]. The procedure of employing /I to approximate
the solid angle integration of the transmission is referred to as
the exponential kernel approximation [Sparrow and Cess.
1970, p. 226]. However, instead of adopting the standard pro-
cedure of employing one value for fi, we obtain exact values of
ft as a function of the optical depth from tabulated values of
the £3 exponential kernel function [see Sparrow and Cess.
1970, pp. 200, 312]. The values of fi as a function of T is fit by
the following smooth expression:
(ft)-1 =
0.5
10r2
(5)
In (5), the optical depth T is the total optical depth, i.e., the
sum of the optical depths of all gases in the interval. The
above set of equations is mathematically and conceptually
rigorous if one of the two following asymptotic limits are
satisfied.
1. The optically thin limit, i.e., T, « 1. In this limit, (1H5)
reduce to
A = 2Sw
(6)
It can be easily shown that (6) is the exact expression for the
band absorption in the optically thin limit. Ramanathan
[1975] used this expression to treat the CFC13 and CF2C12
bands.
2. The smeared out line structure limit. In this limit, the
line spacing between neighboring lines is much smaller when
compared with the line half-width. Consequently, the lines are
smeared out and the absorption coefficient follows a smooth
variation with wavelength. This limit is adequately satisfied
for the CFClj and CF2C12 bands, as can be inferred from the
TABLE 3. Band Parameters for Trace Gases that Employ
Equation (1) for the Band Absorption
Species
CFC13(CFCH)
CF2C12 (CFC12)
CF<
All others
Aw,
cm'1
60
60
20
60
N
3
2
1
1
i
1
2
3
1
2
1
1
/.
0.25
0.25
0.5
0.25
0.75
1
1
k.
0.72
0.22
0.06
0.52
0.48
1
1
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5556
RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
TABLE 4. Band Locations and Strengths
Band Strengths,
cm"1 (atmcm)"1 STP
Trace Gas
C02
N2O
CF4 (F14)
C2F6(F116)
CF3Q (FU)
CF2C12 (F12)
CHClFj (F22)
CFa3(Fll)
cH2a2
CHC13
CCI4
cH3ca3
CHt
C2H2
S02
Ozone
PAN
CHF3
CH2F2
CBrF3
Band Center,
cm"1
667
589
1168
1285
632
1261(2vJ
1285(v3)
714
1116
1250
783
1102
1210
915
1095
1152
810
1110
1310
846
1085
717
758
898
1268
774
1220
776
725
1080
1385
1306
1534
730
1328
518
1151
1362
1041
1103
590
790
1160
1300
1730
H 17-1152
1090
1085
1209
Range of
Measurements
i
20.7^0.3
8.5-12
242-384
42-62
4175-5934
1370-1568
1237-1330
789-893
1670-1965
576-781
35
424-548
4.3-5.4
119-147
864-1201
140-206
1317-2026
148-185
2-3
724-804
95.6-101.1
116-125
96-106.8
844-857
356-382
10-11
Value Adopted2
44 bands incl.
27(F, 1H, 41)
10(F, 1H, 41)*
234.5(F, 1H, 41)
54.7
4175
146
1057
3658
157
2505
3000
1567.5
1236.8
835.8
237
691
109
1965
736
35
424
5.4
118.7
1009
140
1437
299.8
167
14.2
185
801
95.6
106.8
857
376
11
78
321
326
272
576
3838.5
1314
2069.3
2074.7
Reference1
M
M
P
P
P
K
N
K
P
P
P
N
P
P
P
P
P
M
N
P
P
P
lThe reference is for the value adopted in this study: M, McClatchey et at. [1973]; N, H. Niki
(personal communication, 1983); P, Pugh and Rao [1976]; and K. Kagann et at. [1983].
-f. fundamental band; 1H, first hot band; I, isotopic band. 41 denotes four isotopic bands.
'Minimum of 44 isotopic, fundamental, and hot bands are required.
Treated as two band systems: one for the 2v4 band and one for the hot band, and each system has
four isotope bands.
line parameters given by Goldman et al. [1976a]. Inspection of
published spectra reveals that this limit is more than ad-
equately satisfied for most other polyatomic trace gases con-
sidered here.
The values of the band parameters and band strengths are
given in Tables 3 and 4, respectively. In order to examine the
validity of the present approach (i.e., (1)), we computed the
surface-troposphere heating due to the strongest band of
CFC13 (Fll) with a fine spectral resolution model which com-
putes transmittances at 1 cm ~' intervals employing line pa-
rameters given by Goldman et al. [1976a] and performs angu-
lar integration with a 12-point Gaussian quadrature scheme.
As shown in the next section, the surface-troposphere heating
estimated by employing (1) agrees within 4% with that ob-
tained from the detailed computations. The procedure adopt-
ed in the present study for the various trace gases is summa-
rized below.
1. For all trace gases except H2O, CO2, CH4, N2O, and
O3, (1H5) are adopted.
2. The parameter, Aoi, is assumed to be 60 cm ~' for all of
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RAMANATHAN ET AL. : TRACE GAS CLIMATE EFFECTS
the bands, except CF4, for which Aw = 20 cm '. These values
are chosen by inspection of the published spectra. For exam-
ple, Goldman et al. [1976a, b~\ have shown the spectra for the
strongest bands of CFC13 and CF2C12. For the CFC13 band at
846 cm"1, the line strengths in the band wings around 810
and 869 cm"' are smaller by 2 orders of magnitude than their
values near the band center. For the CF2C12 band, the Aw can
be as large as 100 cm"', but our calculations are rather insen-
sitive to Aw for Aw > 40 cm"1. The CF< band at 1285 cm'1
appears to be extremely narrow [Goldman et al., 1979]. Al-
though we have chosen 20 cm"', we have examined values as
low as 5 cm"l, and these results will be discussed subsequent-
ly.
3. For CFClj and CF2C12, the exponential-sum fit param-
eters N, /,, and fc, are obtained from the random model line
parameters published by Goldman et al. [1976a, &]. Note how-
ever, as mentioned later, the band strengths are obtained from
Kagann et al. [1983]. For all other gases, the relevant line
parameters are not available, and hence we let N = 1. This in
turn forces kt = 1 and f, = 1 because of the consistency re-
lationship expressed in (3) and (4).
4. We employ an accurate procedure for evaluating the
Planck function. For w> 1000 cm"1, the Planck variation
with co is so strong that, the Planck function evaluated at the
band center (a commonly adopted procedure in climate
models) can differ from the mean value for the band by as
much as 10-15%. To avoid such errors, the Planck function is
evaluated at 10 cm"1 intervals within the band, and a mean
value for the band is obtained by averaging the narrow band
values.
5. Band strengths: Except for CFC13, CF2CI2, CHjCClj,
CFC22, and PAN, we have relied heavily on the published
summary by Pugh and Rao [1976], denoted as P in Table 4.
These authors give a range of measured values, which are
reproduced in Table 4. For this study, we have chosen the
values measured after the 1970's, and if these were not avail-
able, we adopted the middle value of the range given in P. For
CFClj and CF2C12 we have adopted the most recent values of
Kagann et al. [1983]. For the CF4 v3 band at 1285 cm"',
Wang et al. [1980] have employed a value of 5934 cm"1 (cm
aim)"1 based on Saeki et a/.'s [1976] measurements. This
value is beyond the range given by Pugh and Rao [1976], and
furthermore, the recent measurements by Goldman et al.
[1979] yield a value of 4500 cm"2 atm"1. The band strengths
for CHjCCl3, CHC1F2 (F22), and PAN are not available in
the open literature. High-resolution spectral data for these
TABLE 5.
Surface-Troposphere Heating due to CFC11 846-cm"
Band
Model*
F,
W
Comment
Reference
Present scheme
Optically thin
approximation
0.51
0.525
0.59
Narrow-band model with 1-cm '
resolution; 12-poinl Gauss
quadrature for angular
integration.
Equations (IH5).
Parameters from Table 3.
Equation (6)
Atmosphere: midlatitude clear-sky conditions. F: surface-
troposphere heating due to increase of CFC11 from 0 to 2 ppb.
•For comparison purposes, all the three models adopt the spec-
troscopic parameters from Goldman et al. [I976a],
bands and integrated band strengths were kindly supplied to
us by H. Niki (personal communication, 1983), whose values
are shown in Table 4 as N.
6. The CFC's and other trace gases besides CO2 are as-
sumed to be mixed uniformly from the surface up to 12 km.
above which the mixing ratio is assumed to decrease with a
scale height of 3 km. However, as shown by Fabian et al.
[1984], the mixing ratios of long-lived species such as CF^,
C2F6, and CF3C1 are nearly constant from the surface to the
middle stratosphere (~30 km). In the next section we will
examine the sensitivity of the greenhouse effect to the mixing-
ratio profile. CH4, N2O, and CO2 are assumed to be uniform-
ly mixed throughout the atmosphere. The observed mixing
ratio of CH4 and N2O decreases with height above 12 km.
However, as shown in the next section, the computed surface
warming due to CH4 and N2O increase is insensitive to their
mixing-ratio profile in the stratosphere. The O3 profile is
taken from the hemispherical, annual data given by Ramana-
than and Dickinson [1979].
7. We have allowed for the overlap of all of the minor
trace gas bands with H2O, CO2, O3, CH4, N2O, and CFC's
and the mutual overlap of these gases. In certain spectral lo-
cations, e.g., 1285 cm"', as many as four gases have strong
overlapping bands, and such effects are included in the calcu-
lations. For all of the trace gases with band centers shortward
of 8 /an and longwave of 12 ^m, the overlap with CH^, N2O.
CO2, or H2O is treated by adopting the Malkmus narrow-
band model. The transmission is computed with a spectral
resolution of 20 cm"1. The line parameters are derived from
the 1982 Air Force Geophysics Laboratory (AFGL) line tape
[Rothman et al., 1983]. Hence the overlap treatment does not
follow the broadband model approach.
In summary, the number of trace gases included in this
study, together with the treatment of the overlap between the
various gases and the details of the various fundamental, hot.
and isotopic bands, make the present study the most compre-
hensive climate model calculations that have been performed
so far for the trace gas climate effects.
4.3. Accuracy of the Trace Gas Radiative Treatment
The accuracy of the treatment as given by (1H5) is exam-
ined by performing detailed narrow-band calculations for the
CFC13 band at 11.8 ^m. This band is chosen because it is the
strongest of the CFC bands and hence provides a stringent
test of the present scheme. Furthermore, random-band model
parameters, with a spectral resolution of 1 cm"'. for this band
have been provided by Goldman et al. [1976a]. For the refer-
ence calculations, a Malkmus random-band model with a
spectral resolution of 1 cm " ' is employed. The details of this
model are given by Kiehl and Ramanathan [1983]. The angu-
lar integration within each spectral interval is performed with
a 12-pomt Gaussian quadrature. The model atmosphere rep-
resents midlatitude summer condition with no clouds. In
Table 5, the change in the net (down-up) flux at the tropo-
pause, i.e., the surface-troposphere heating, due to increase of
CFC11 from 0 to 2 ppb as computed by the reference model is
compared with that obtained from the present scheme, i.e..
(1H5). Also shown in this table, for comparison purposes, is
the result obtained from (6), which is the form of the optically
thin limit equation employed by Ramanathan [1975]. It is seen
that the present scheme is in excellent agreement with the
more detailed calculations. The equation for the optically thin
assumption employed by Ramanathan [1975] overestimates
the heating by about 16%. However as shown later, the sur-
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5558
RAMANATHAN ET AL.: Ti
TABLE 6. Examples of the
Effect of Overlapping of
Absorption
Bands on the Computed Surface Wanning
With Overlap*
Constituent
CH4f
N2Ot
CF2C12 (F12»
CFClj(Fll)
CF4 (F14)
CFjCl (F13)
CH2C12
CHClj
ca4
C2H2
C2F6(F116)
CH3CC13
PAN
Change
1.25X
1.25X
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
0-1 ppb
AT,
0.09
0.12
0.16
0.14
%0.06
0.22
*0.03
*0.06
%0.08
*0.02
0.13
*0.02
*0.04
*T,
0.08
0.1
0.15
0.13
as 0.05
0.2
wO.02
*0.06
*0.07
*0.02
0.12
ssO.01
a 0.03
Without
Overlap
AT.
0.19
0.2
0.19
0.16
0.12
0.25
0.04
0.09
0.11
0.07
0.2
0.04
0.06
AT, is surface-air temperature change, and AT, is surface (or
ground) temperature change.
•Numbers have been rounded off; when AT is less than about 0.02
1C, because of the convergence criterion, the result may be uncertain
by as much as ± 30%.
tCH4 and N2O are assumed to be uniformly mixed from the sur-
face to the top of the atmosphere. However, these calculations, when
repeated with observed profiles which show a decrease in the mixing
ratio above 12 km, yield AT results identical to those shown in this
table.
JFor this gas and for all the others following it, the mixing ratio
decreases above 12 km with a scale height of 3 km. The computed
surface warming is larger by about 15% when the mixing ratio above
12 km is held constant at the surface value.
face wanning due to increase of CFC's computed with the
present accurate scheme is in excellent agreement with that
estimated by Ramanathan [1975], The agreement is because of
the following compensating effects: (1) the band strengths used
in Ramanathan [1975] are smaller by about 10% than the
recent values used in this study; (2) the 16% error shown in
Table 5 is reduced somewhat with the inclusion of clouds; (3)
the error in the optically thin approximation is smaller for the
other bands of CFC11 and 12 whose strengths are consider-
ably smaller than the 11.8-jon CFC11 band.
Cess [1982] has also performed similar narrow-band calcu-
lations for CFC13 and showed that the smeared-out line struc-
ture assumption, which is invoked in arriving at (1), is an
excellent approximation for CFC bands. In summary, we con-
clude that the present scheme is very accurate. The only
source of remaining error is the neglect of the temperature
dependence of the hot bands of CFCs that have been detect-
ed, in the vicinity of the strong CFC13 and CF2C12 bands, by
Varanasi and Ko [1977] and Nanes et ai [1980]. While the
effects of the hot bands are included in this study, the temper-
ature dependence of their band strengths arising from the tem-
perature dependence of the excited vibrational states is ig-
nored. Nanes et al. [1980], however, suggest only a weak tem-
perature dependence. As a note of caution, we add that the
temperature dependence mentioned above should not be con-
fused with the temperature correction that is needed to con-
vert band strengths, S, measured at temperature T to STP
conditions. Recall that in (1), the path length w is in cm atm,
STP, and hence S measured at a temperature T in the units of
cm"1 (cm atm)"1 should be multiplied by (T/273) to convert
to the units of cm"1 (cm atm)~', STP. In some instances in
the literature, this correction factor has been confused for the
temperature dependence of S. The procedure of employing the
correction factor (T/273) is rigorous for the fundamental CFC
bands. For the hot bands, however, we need an additional
term to account for the temperature dependence of the excited
vibrational state [e.g., see Kiehl and Ramanathan, 1983, equa-
tion 12].
5. RESULTS
5.1. Uniform Increase in Certain Trace Gases
Before presenting the results for the trace gas scenario
shown in Table la, we will discuss results for a hypothetical
case of 0-1 ppb increase for several of the trace gases. The
purpose of this exercise is twofold: to elucidate the processes
that determine the magnitude of the trace gas effects and to
identify the most important trace gases from a climate view-
point. For these two objectives, we avoid specific scenarios to
assure that conclusions are not scenario dependent.
The computed surface warming due to a 0-1 ppb increase in
15 different trace gases is shown in Figure 1. The tropospheric
O3, CH4) and N2O effects are relatively better known and are
shown merely for comparison purposes. Several interesting
and rather surprising features of the results shown in Figure 1
are noted below.
TABLE 7. Computed Surface Temperature Change Resulting From
Increasing CFC's From 0 to 2 ppbv1
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
Model
Ramanathan [1975]
Reck and Fry [1978]
Chamberlain et ai. [1982]
Wang et al. [1976]
Wang et al. [1980]
Hansen et al. [1982]
Lacis et al. [1981]
Karol et al. [1981]
Hummel and Reck [1981]
This study7
This study (uniformly
mixed)*
This study : CFC band
strengths from Ramanathan
[1975]
This study: CFC band
strengths from Varanasi
and Ko [1977]
FCA,2
K
0.565
0.766
0.38
0.8
0.76
0.55-0.6"
0.63-0.7"
0.51-0.568
0.50-0.558
FCT,3 Empirical,*
K. K.
0.9 0.9
1.42
0.56
0.69
0.50
0.65
Companson of various model results. CFC13 and CF2C12 are each
increased from 0 to 2 ppbv.
^Ramanathan [1975], this study, and the GISS models (items 4-6)
assume a constant CFC mixing ratio from the ground to 12 km. and
above 12 km the mixing ratio decreases exponentially with a scale
height of 3 km. Reck and Fry [1978], Karol et al. [1981], and Hummel
and Reck [1981] assume a constant CFC mixing ratio from the
ground to the top of the atmosphere.
2One-dimensional radiative-convective model with fixed relative
humidity and with fixed-cloud altitude (FCA).
3Same as footnote 2. but with fixed-cloud temperature (FCT) in-
stead of fixed-cloud altitude.
•'Estimated from an empirical expression for the surface temper-
ature sensitivity parameter.
'The FCA model results were not mentioned by Ramanathan
[1975] but were obtained for the purposes of the present comparison.
*Reck and Fry gave AT results for 1-ppbv increase, which was
linearly scaled for the 2-ppbv increase.
7CFC mixing ratio as described by Ramanathan [1975]. See foot-
note 1 above.
'The lower value is surface temperature change, and upper value is
surface air temperature change.
"CFC mixing ratio is constant from surface to top of the atmo-
sphere.
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RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
SENSITIVITY TO UNIFORM INCREASE IN MIXING RATIO
5559
<
o
UJ
cr
5
£E
I
UJ
(T
<
Ul
g
1
0.5 r-
0.2
O.I
0.05
0.02
0.01
T
• 0 to I ppbv increase •
TRACE GAS
Fig. I. Surface temperature increase due to a 0-1 ppbv increase in trace gas concentration. Troposphenc O3, CH4, and
N,O increases are also shown for comparison.
1. Among the other trace gases, CFC13, CF2C12, CF3C1,
C2F6, CHF3, and CBrF3 exert the largest surface wanning
effect. The contribution by CF3C1, C2F6, CHF3, and CBrF3
has not been discussed before and is a surprising and new
'aspect of the present results. The primary reason is the
strength of their bands, and as shown in Table 4, the strongest
bands of these gases are stronger than the strongest bands of
CFClj and CF2C12 by more than a factor of 2. The location of
the band center, however, plays a crucial role because of the
overlap effect. For example, in the 1295-cm'1 region, the ab-
sorption by N2O, CH4, and H2O bands saturates this region,
and hence trace gases in this spectral region have relatively
lesser impact on climate. This is the primary reason why CF4,
although possessing a band in the 1285-cm"1 region which is
stronger than any other bands in the 8- to 20-ian region,
produces a surface wanning of only 0.06 K.
2. The sensitivity of surface temperature to tropospheric
ozone has been anticipated earlier [Ramanathan and Dickin-
son, 1979] but has not received much consideration elsewhere
in the literature.
3. Although PAN has several moderately strong bands, its
strongest band is in the middle of the strong 6.3-^m H2O
bands. Similarly, although CC14 and CHC13 have moderately
strong bands, their strongest bands are located in the
774-cm"1 region, where they are overlapped by CO2, H2O
rotation bands, and the H2O continuum.
4. To illustrate the importance of the overlap problem, we
show in Table 6 the surface temperature increase with and
without the overlap effects. Such results, besides illustrating
the contribution from various radiative processes, also facili-
tate model intercomparison study by enabling the identifi-
cation of the sources for model differences. We also show in
this table, the surface and surface air temperature change for
one of the two cases. In general, surface air temperature is
larger than the surface temperature change by about 10%. It
is clear from Table 6 that for several trace gases, e.g., CF4>
CHClj, CH3CCI3, C2F6, the overlap effect ameliorates AT, by
factors of 1.5-2.
We will now compare the present estimates of AT; with
other published estimates for a few of the trace gases. Consid-
er first CFC13 and CF2C12 for which the differences between
the various model estimates of the global surface temperature
change are disturbingly large as illustrated in Table 7. The
differences shown in Table 7 can arise from differences in the
radiative treatment and (or) from differences in the model sen-
sitivity. In order to isolate these two sources, the climate sensi-
tivity parameter, x, as estimated from various models is shown
in Table 8. As explained by Dickinson [1982] and Ramanathan
[1982], /. and AT; are approximately related by
AT, =s
(7)
where &.F is the radiative forcing of the surface-troposphere
system due solely to trace gas increase, i.e., CFC increase in
the present example. As described below. Tables 7 and 8 pro-
vide the answers for all of the differences in the computed ATS.
1. There is a wide spread in the measured band strengths.
For example, Figure 2 shows the measured band strengths by
various investigators for the strongest CFC bands. The pres-
ent study uses the recent measurements of Kagann et al.
[1983], whereas all of the other studies employ the earlier
measurements. The values used by Ramanathan [1975] under-
estimate (compare item 12 with item 10) AT, by 8% while
Varanasi and Ko's values employed in the Goddard Institute
for Space Studies (GISS) models underestimate (compare item
13 with item 10) AT; by 10%.
2. With respect to the radiative treatment, Ramanathan
[1975] and Chamberlain et al. [1982] employ (6), which is one
form of the optically thin approximation. By comparing item
12 with 1, both of which use the same band strengths, it is seen
that (6) overestimates AT; by about 5%. However, the present
study which uses an accurate procedure is in excellent agree-
ment with Ramanathan [1975] because of the compensating
effects of the smaller band strengths used in that study. The
other models cited in Table 7. unfortunately, do not give the
equation or the details of their radiative treatment. However,
all of these models rely primarily on integrated band strengths
and hence must employ the optically thin approximation, but
not necessarily (6).
3. The unrealistically large value obtained by Chamberlain
et al. [1982] results primarily from their approach of esti-
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5560
RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
TABLE 8. Comparison of Model Climate Sensitivity Parameter
Model
Manabe and Wet herald [1967]
Ramanathan [1975]
Reck and Fry [1978]
Wang et al. [1976]
Wang et al. [1980]
Hansen et al. [1982]
Lacis et al. [1981]
This study
K/Wrn"2
0.53
0.52
0.53
0.47
0.47
0.47
0.47
0.52
f
1.6
1.5
1.23
1.4
1.4
/
(empirical)
1.6
Here, /' = /i(FCT)/x(FCA); /(empirical) = /i]. Midlatitude profiles show a
sharper decrease (scale height %8 km) with altitude than
tropical profiles (scale height > 15 km). We repeated the sur-
face temperature calculations with the observed midlatitude
profiles [World Meteorological Organization, 19826, Figures
1-43 and 1-44]. For a doubling of CH4, both the uniform
mixing-ratio profile and the midlatitude profile yielded a A Ts
of 0.31 K. Similarly, for a doubling of N2O, both mixing ratio
profiles yielded a AT, of 0.4 K. The scale height of the mixing
ratio for CH4 and N2O is sufficiently large (S8 km) that the
stratospheric column abundance (of CH4 and N2O) for the
uniform mixing-ratio profile and the observed profile is nearly
the same, and hence both profiles yield the same surface
wanning.
For all of the other trace gases shown in Figure 1, the
computed AT, is about 15% larger for the uniform mixing-
ratio profile than for the reference profile (assumed in this
study) in which the mixing ratio decreases (above 12 km) with
1800
1700
1600
iinn
v4CCI3F
1 1
Band
Strength
846 cm"
i
-
-
H0959) G(I976) V(I977) N(I980) K(I983)
1500
1400
1300
9°nd Strength 915cm'
M(I966) G(I976) V(I977) K(I983)
Fig. 2. Band strengths for the v4 CC12F2 bands in units of cm~2
atm"' at 296°K. Sources for band strengths are H(1959), Herranz et
al. [1959]; G(1976), Goldman et al. [1976a, />]; V(1977). Varanasi and
Ko [1977]; N(1980), Nones et al. [1980]; and K.(1983), Kagann et al.
[1983].
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RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
5561
a scale height of 3 km. This nonnegligible sensitivity in the
computed surface warming for these trace gases is largely be-
cause of the substantial difference in the stratospheric abun-
dance between the uniform mixing-ratio profile and the profile
with a J-km scale height.
5.2. Climatic Effects of the Projected Increases
Figure 3 shows the results of the radiative-convective model
calculations employing the projected increases shown in
Tables la and 2. Our results basically confirm the suggestions
by earlier calculations (see World Meteorological Organization,
[1982s] for a summary) that the other trace gases can amplify
the CO2 surface wanning by factors ranging from 1.5 to 3. But
our results reveal several new features. We will summarize
these features by considering the "best estimate" curve in
Figure 3.
1. The surface warming (AT,) due to all the trace gases
(shown in Figure 3) is 1.54 K. The increase in CO2 contributes
about 0.71 K.
2. The CFCs, CFC13 (Fll) and CF2C12 (F12), have the
largest warming effect of all the trace gases besides CO,. The
direct radiative effect of CFC13 and CF2C12 (increase) contrib-
utes about 0.36 K. to the surface warming. Furthermore, the
stratospheric O3 change, resulting largely from the projected
increase in CFCs, leads to an additional warming of about
0.08 K. Hence the combined effect of 0.44 K. due to CFCs is
roughly 60% of the CO2 effect.
3. Somewhat smaller, but nonnegligible, surface wanning
results from the increases in CH4 (0.14 K), N2O (0.1 K) and
tropospheric O3 (0.06 K).
4. Increases in CHC1F2 (F22), CH3CC13, and CFjCl con-
tribute, respectively, about 0.04 K, 0.02 K, and 0.01 K. All
others shown in Figure 3 have negligible (< 0.005 K) impact.
The warming we compute due to stratospheric ozone is at
variance with Wang et al. [1980] results, who compute a sur-
CUMUIATWC SURFACE WARMING
FOR ADOPTED TRACE GAS SCENARIO
( Ptriod:Fifty Yeors from 1980 Levels)
ATMOSPHERIC TEMPERATURE CHANGE
DUE TO C02 AND OTHER TRACE GASES
TRACE GASES
Fig. 3. Cumulative equilibrium surface temperature warming due
to increase in CO2 and other trace gases. Increases in gas amounts
from 1980 values to 2030.
TEMPERATURE CHANGE (°K)
Fig. 4. Change in the vertical distribution of temperature due to
an increase in CO2 alone, and CO, along with all other trace gases
listed in Figure 3. The trace gas increase scenario is as given by the
"best estimate" values in Table la.
face cooling due to CFM-induced ozone perturbations. The
major source of discrepancy is in the adopted stratospheric O3
perturbation profile. The present profile is based on the most
recent chemistry and reaction rates, and it shows that large
decreases in middle and upper stratospheric O3 profile are
accompanied by somewhat smaller percentage increases in the
lower stratosphere. Additional calculations were performed to
examine the sensitivity of the computed surface warming to
vertical distribution of O3 change, which lead to the following
inferences. The profile shown in Table 2 leads to a surface
warming of 0.08 K. Roughly, 0.06 K is due to the O3 decrease
above 30 km, and the remainder of 0.02 K. is due to the O3
increase below 30 km. Thus the O3 decrease above 30 km as
well as the O3 increase below 30 km contribute to a warming.
The perplexing nature of this result can be understood from
the detail analyses given by Ramanathan et al. [1976] and
Ramanathan and Dickinson [1979], and hence only a brief
discussion is given below.
A decrease in stratospheric O3, irrespective of the altitude of
the decrease, would lead to an increase in the solar radiation
reaching the troposphere, and this solar effect would tend to
warm the surface. However, O3 also alters the IR (longwavel
emission from the stratosphere in two ways: first, the de-
creased solar absorption (due to O3 decrease) cools the strato-
sphere; the cooler stratosphere emits less downward to the
troposphere. Second, a decrease in 03 reduces the absorption
(by the O3 9.6-/im band) of the surface-troposphere emission.
This reduction causes an additional cooling of the strato-
sphere, which in turn, causes an additional reduction in the
downward IR emission by the stratosphere. Thus the IR ef-
fects of O3 decrease tend to cool the surface. However, the IR
opacity of stratospheric CO2, H2O. and O3 is sufficiently
strong that the impact of the reduction in IR emission (by the
stratosphere) on the surface diminishes with an increase in the
altitude of O3 perturbation. On the other hand, the surface
warming induced by the solar effect is independent of the
altitude of O3 perturbation. Consequently, for a decrease in
O3 in the upper stratosphere, the solar effect dominates (lead-
ing to a surface warming), while for a decrease in the lower
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RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
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I
TABLE 9. Gases Not Shown in Figure 3
Gas
CHCljF
C2CI3F3
C2C12F4
C2C1F3
SO2;CS2;H2S
COS;CS2;H2S
CH2QCH2a
CHjCI
C2H6; C2H4; C3H,
HCHO; CHjCHO
CHjF; CH3Br: CH3I
CH2F2
CHF3
CBrF3
HN03
NOX(NO, NO2> NO3, N2O5)
HCN
7- to 13-iaa
Absorption
Feature
band intensities
unavailable
band intensities
unavailable
band intensities
unavailable
band intensities
unavailable
strong
weak
strong
weak
weak
weak
weak
strong
very strong
very strong
strong
weak
weak absorption
Predicted
Concentration
Increase
yes
yes
yes
yes
uncertain
no
small
no
uncertain
uncertain
uncertain
uncertain
uncertain
small
small but uncertain
uncertain
uncertain
Potential
Role
yes
yes
yes
yes
no
no
no
no
no
no
no
yes
yes
no
no
no
no
The first four chlorofluorocarbon gases here could contribute significantly to future global warming
because of the spectral positions of their absorption bands in the 7-13 urn atmospheric window region if
their band-absorption intensities are large enough. For other gases, e.g., HCN and SO2, their absorption
bands are not strong enough to be significant at present or near-present atmospheric concentrations. For
other gases such as C,H6 and CH3F, we have too little information to be able to estimate future trends.
1
I
stratospheric O3, the IR effect dominates (leading to a surface
cooling).
The uncertainty in our computed surface warming due to
stratospheric O3 change is best illustrated by the following
examples. The profile of O3 change in Table 2 for altitude
above 30 km when combined with 10% uniform O3 decrease
between 12 and 30 km leads to a surface warming of 0.02 K;
whereas the same profile (as in Table 2) above 30 km when
combined with a 10% uniform O3 increase between 12 and 30
km leads to a surface warming of 0.1 K.. In view of the high
sensitivity of the computed temperature change to the vertical
O3 profile, our computed estimates for stratospheric O3
change should be viewed with caution because such distri-
butions would be influenced by atmospheric dynamics (whose
effects are ignored in this analysis) and of course by remaining
uncertainties in model chemistry.
The vertical distribution of the computed atmospheric tem-
perature change is shown in Figure 4. It is clear from this
figure that other trace gas effects on temperatures are com-
parable to CO 2 effects, not only for surface wanning, but also
for stratospheric cooling. The stratospheric cooling, to a large
extent, results from the stratospheric O3 reduction. The poten-
tial climatic effect of gases that are not explicitly discussed in
Figure 3 is summarized in Table 9.
5.3. Effects of the Inferred Trace Gas Increases From the
Preindustrial to the Present Levels
For the sake of discussion, the concentrations for the year
1880 are associated with the preindustrial levels, and these
concentrations have been shown in Table Ib, while the ob-
served 1980 concentrations are shown in Table la. The com-
puted equilibrium temperature changes are shown in Table 10.
The CO2 increase causes a surface warming of 0.52 K, which
is enhanced by 50% due to the increase in the other trace
gases. The computed stratospheric cooling due to CO2 in-
crease is substantial, but that due to other gases is negligible.
The computed stratospheric cooling would be larger had we
included the effects of stratospheric O3 decrease due to in-
creases in CFC's. From Table \Qb, which shows the contri-
bution of the individual gases, it is seen that CH4, tropo-
spheric O3, and CFCs are the largest contributors, next to
CO2, to the surface warming computed for the period 1880-
1980.
6. SUMMARY
The basic conclusion that can be derived from the present
study is that the radiative effects of increases in trace gases
(other than CO2) are as important as that of CO2 increase in
determining the climate change of the future or the past 100
years. Several tens of man-made chemicals have been detected
in the troposphere and about 20 of these have strong absorp-
tion features in the 7- to 13-/*m regions of the longwave spec-
trum. The present-day, taken as the year 1980, concentrations
are taken from in situ observations. A careful analysis of the
measured trends from early 1970's to 1980 form the basis for
the concentrations projected 50 years into the future. Pub-
lished ice-core CH4 observations, surface-based O3 observa-
tions, and other studies are used to infer the trace gas con-
centrations for the preindustrial era. The equilibrium surface
and atmospheric temperature changes estimated with the aid
of a radiative-convective model reveal the following features.
1. The preindustrial to present-day increase in CO2 causes
an equilibrium surface warming of 0.5 K. in the model, which
is enhanced by a factor of 1.5 by the increases in the other
trace gases. CH4, tropospheric O3, and CFCs are the largest
contributors to this enhancement. The upper stratospheric
cooling due to the CO2 increase is as large as about 3 K.
2. The projected CO2 increase from 339 ppm in the year
1980 to 450 ppm in 2030 warms the model surface by 0.7 K,
which is enhanced by a factor of about 2.1 by the other trace
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RAMANATHAN ET AL. : TRACE GAS CLIMATE EFFECTS
5563
gases. The factor of trace gas enhancement varies from about
1.5 to 3 depending on the assumed scenario. The trace gases
that contribute to this significant enhancement are CFC13
(Fll), CF2C12 (¥12), CH4, N2O, stratospheric and tropo-
spheric Oj. Somewhat smaller but nonnegligible contributions
arise from CHCIF2 (F22), CH3CC13, and CFC13.
3. The stratospheric O3 changes resulting from the as-
sumed increase in CFC's and other chlorine compounds by
year 2030 are a large decrease in middle stratospheric O3
accompanied by a slight increase in lower stratospheric O3.
Hence although CFCs are estimated to cause only a slight
reduction in the column ozone, the significant perturbation to
the shape of the O3 profile leads to a nonnegligible surface
warming of 0.08 K. Thus the O3 change due to CFC's adds to
the surface warming of 0.36 K resulting from the CFC direct
radiative effects. These two effects when considered together
make CFC's the largest contributors (next to CO2) to the
overall surface warming computed in this study. However,
because of the strong sensitivity of the computed surface
wanning to the vertical profile of O3 change, the magnitude of
the potential surface warming due to stratospheric O3 change
is highly uncertain.
4. All of the other trace gases perturb the vertical atmo-
spheric profile in the same manner as CO2 in the following
sense: they warm the surface and the troposphere while cool-
ing the stratosphere (above 20 km) significantly. However,
there is one important difference between the radiative effects
of CO2 and the other trace gases: as pointed out by Dickinson
ei al. [1978], CFCs have a strong warming on the tropical
tropopause. Also the studies by Ramanaihan and Dickinson
[1979] and Pels et al. [1980] reveal the significant sensitivity
of tropical tropopause to O3 perturbations. Warming of the
tropical tropopause by 2-3 K could lead to large changes in
stratospheric water vapor.
5. On a ppb basis, CF3CI has the strongest greenhouse
effect (exceeding very slightly even that of CFC 12) followed
closely by CBrF3, CF2C12 (F12), CHF3, CFCI3 (Fll), and
C2F6 (F116), all of which have effects comparable to that of
TABLE 10.
Computed Temperature Changes due to Inferred Trace
Gases for the Period 1880-1980
Temperature Change, K
Stratosphere, km
Constituent
Surface*
26-30
38-42
a. Surface and Stratospheric Temperature Change
CO2 0.52 -0.77 -2.78
CO j plus all other gases 0.79 -0.8 -2.85
Constituent
Concentration
Change
Temperature
Change
CO,
CH!
N2O
Troposphere O3
CFC11
CFC12
All others in Table la
275-339 ppm
1.15-1.65 ppm
0.285-0.3 ppm
12.5%
0-0.18 ppb
0-0.28 ppb
0 to 1980 values
— ;?
0.52
0.12
0.02
0.04
0.025
0.04
0.02
Possible changes m stratospheric O 3 are ignored.
"Surface air temperature change is larger than the surface temper-
ature change by about I0-13"'i
CFC13 or CF2C12. Gases such as CF4, CC14, and PAN have
strong absorption features, but due to the overlap with CH^,
N2O, CO2, and H2O bands, these gases are not very effective
in enhancing the atmospheric greenhouse effect. However, our
conclusion concerning the overlap effects should be considered
as tentative. Measurements of narrowband spectroscopic pa-
rameters for these other trace gases are currently not avail-
able, and such measurements are needed for improving the
accuracy of the estimates for the overlap effects. For impor-
tant species such as C2C13F3 (F113), C2C12F4 (F114), and
CjCIF, (F115) even band strengths are not available.
6. The accurate radiation model developed here for CFC13
(Fll) and CF2C12 (F12) helped sort out the differences be-
tween the various published studies for the estimated surface
warming.
The important implication of this study is that the prein-
dustrial to the present increase in CO2 and the other trace
gases might, very likely, have caused a significant perturbation
to the radiative heating of the climate system. This pertur-
bation radiative heating induces a warming of about 0.8 K m
the present model, whereas it might have induced a warming
twice as large in recent GCM's [Washington and Meehl, 1984;
Hansen et al., 1984]. These GCM's compute a 4 K global
warming due to CO2 doubling as opposed to the 2 K. yielded
by the radiative-convective model. The 0.8-1.6 K global
warming, had it indeed occurred from the preindustrial to the
present, should have been detectable above the statistical fluc-
tuations of the climate. This is a controversial issue, and the
published papers have contradictory results. Hansen et al.
[1982] suggest that the CO2 warming is discernible from ob-
served records of global or hemispherical average temper-
atures. The statistical analysis of the 70-year homogeneous (in
time and in longitude) temperatures for 50-70°N by Madden
and Ramanathan [1980] has failed to reveal the CO2 effect.
Before we can attempt to verify the greenhouse theories of
preindustrial to present warming by comparing model results
with the observations, the following important issues must be
dealt with.
1. The one-dimensional and GCM results pertain only to
the equilibnum warming of the surface to a step-function in-
crease in the trace gases. The quantity of interest, for the
purpose of verification, is the transient climate response to a
time-varying distribution of trace gases. Even assuming that
time-dependent trace gas distribution is known (for the past
100 years), our understanding of the ocean mixed layer inter-
actions with the atmosphere and the thermocline as well as
the lateral ocean heat transport is too imprecise to estimate
reliably the transient response of the climate system.
2. Other climate forcing terms, e.g., solar irradiance, vol-
canic aerosols, surface radiative properties, can also change on
the time scales of interest to this study, and we do not have
adequate data bases to estimate their contributions to past
climates. Major volcanic events, such as EI Chichon, can cause
an equilibrium global cooling of 0.5-1 K, but the aerosol resi-
dence time is about 2 years or less, and as yet, we have not
come to grips with the tough issue of estimating the transient
response to an episodic forcing.
3. The last issue concerns the source of errors in observa-
tions of temperatures, humidities, and other trace gases arising
from instrumental and sampling biases. There are no reliable
global measurements for key components like lower strato-
spheric H2O and troposphenc O3.
It is hoped this study will provide more scientific justi-
fication for making some key measurements on a long-term
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5564
RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
basis of trace gas trends (at least the top 12 gases identified
here), stratospheric aerosols, stratospheric humidity, and
tropical tropopause temperatures. Of equal importance, accu-
rate measurements of narrow-band spectroscopic parameters
and band strengths for the trace gases are urgently needed.
Acknowledgments. We are indebted to Dr. Niki for providing un-
published data. One of us (V.R.) thanks the Atmospheric Sciences
Division, NASA Langley for the hospitality extended during the sab-
batical visit. L. B. Callis of NASA Langley provided a careful review
of an earlier version of this manuscript. We thank Gretchen Escobar
for typing several versions of this manuscript. We also thank M.
Coffey of NCAR for providing the routines and data tapes for infer-
ring narrow-band moilel' parameters. NCAR is sponsored by the Na-
tional Science Foundation.
REFERENCES
Alexandrov. E. L., J. L. Konol. A. Ch. Khrgian, L. R. Rakipova, and
Yu. S. Sedonov, Contribution of ozone and other minor trace gases
to atmospheric radiation regime and their possible effect on global
climate change, WMO Global Ozone Res. and Monitoring Proj.
Rep. 10, 79 pp.. World Meteorol. Organ., Geneva, 1981.
Andreae, M. O., and H. Raemdonck, Dimethyl sulfide in the surface
ocean and the marine atmosphere: A global view, Science, 221,
744-747, 1983.
Angell, J. K., and J. Korshover, Global variation in total ozone and
layer-mean ozone: An update through 1981, J. Climate Appt. Me-
teorol.,22, 1611-1627, 1983.
Bauer, E.. A catalog of perturbing influences on stratospheric ozone
1955-1975, J. Geophys. Res., 84, 6929-6940, 1979.
Berg, W. W., L. E. Heidt, W. Pollock, P. D. Sperry, R. J. Cicerone,
and E. S. Gladney, Brommated organic species in the Arctic atmo-
sphere, Geophys. Res. Lett., II, 429-432, 1984.
Blake, D. R., E. W. Mayer, S. C. Tyler, Y. Makide, D. C. Montague,
and F. S. Rowland, Global increase m atmospheric methane con-
centrations between 1978 and 1980, Geophys. Res. Lett., 9, 477-480,
1982.
Bojkov, R. D., Tropospheric ozone, its changes and possible radiative
effect, WMO Spec. Environ. Rep. 16, World Meteorol. Organ.,
Geneva, 1983.
Boughner. R. E., and V. Ramanathan. Climatic consequences of in-
creasing CO2: A study of the feedback mechanisms between in-
creased CO, concentrations and the atmospheric ozone, water
vapor, and thermal structure and balance, paper presented at the
Second Conference on Atmospheric Radiation, Am. Meteorol. Soc..
Arlington, Va., Oct. 29-31. 1975.
Callis. L. B., M. Natarajan, and R. E. Boughner, On the relationship
between the greenhouse effect, atmospheric photochemistry, and
species distributions, J. Geophys. Res., 88, 1401-1426, 1983.
Cess, R. D., The optically thin approximation. Meeting of Experts on
Potential Climatic Effects of Ozone and Other Trace Gases, WMO
Rep. 14, pp. 27-28, World Meteorol. Organ.. Geneva, 1982.
Chamberlain, J. W.. H. M. Foley, G. J. MacDonald, and M. A. Ru-
denman. Climatic effects of minor atmospheric constituents, in
Carbon Dioxide Review • 1982, edited by W. C. Clark, pp. 253-278,
Clarendon Press, New York, 1982.
Chatfield, R. B., and H. Harrison, Tropospheric ozone, 2, Variations
along a meridional band, J. Geophys. Res., 82, 5969-5976. 1977.
Chemical Manufacturers Association, 1982 world production and
sales of fluorocarbons FC-11 and FC-12, 29 pp., Washington, D.
C, 1983.
Cicerone, R. J., Atmospheric carbon tetrafluoride: A nearly inert gas,
Science, 206, 59-61, 1979.
Cicerone, R. J., and R. Zellner, The atmospheric chemistry of hy-
drogen cyanide. J. Geophys. Res., 88, 10689-10696, 1983.
Cicerone, R. J., S. Walters, and S. C. Liu, Nonlinear response of
stratospheric ozone column to ciilonne injections, J. Geophys. Res.,
88, 3647-3661, 1983.
Craig, H., and C. C. Chou, Methane: The record in polar ice cores,
Geophys. Res. Lett., 9, 1221-1224, 1982.
Crutzen, P. J., and L. T. Gidel, A two-dimensional photochemical
model of the atmosphere, 2, The troposphenc budgets of the an-
thropogenic chlorocarbons. CO. CH4, CH3C1 and the effect of
various NO, sources on troposphenc ozone, J. Geophys. Res., 88,
6641-6661, 1983.
Cunnold, D.. R. Pnnn, R. Rasmussen, P. Simmonds, F Alyea, C.
Cardelino, A. Crawford. P. Fraser, and R. Rosen, The Atmospheric
Lifetime Experiment. 3, Lifetime methodology and application to 3
years of CFC13 data, J. Geophys. Res., 88, 8379-8400, 1983a.
Cunnold, D., R. Prinn, R. Rasmussen, P. Simmonds, F. Alyea, C.
Cardelino, and A. Crawford, The Atmospheric Lifetime Experi-
ment, 4, Results for CFC12 based on 3 years of data, J. Geophys.
Res.,88.8401-8414,1983*.
Dickinson, R. E.. Modeling climatic changes due to carbon dioxide
increases, in Carbon Dioxide Review, edited by W. C. Clark, pp.
101-133, Clarendon Press, New York, 1982.
Dickinson, R. E., S. C. Liu, and T. M. Donahue, Effect of clorofluoro-
methane infrared radiation on zonal atmospheric temperature, J.
Atmos. Sci, 3S, 2142-215Z 1978.
Donner, L., and V. Ramanathan, Methane and nitrous oxide: Their
effects on the terrestrial climate, J. Atmos. Sci., 37, 119-124, 1980.
Duxbury, J. M., D. R. Baldwin, R. E. Terry, and R. L. Tate, Emissions
of nitrous oxide from soils, Nature, 298, 462-464, 1982.
Ehhalt, D. H., R. J. Zander, and R. A. Lamontagne, On the temporal
increase of troposphenc CH.,., J. Geophys. Res., 88, 8442-8446.
1983.
Fabian. P., R. Borchers, D. Gomer. and S. A. Penkett, The vertical
distribution of halocarbons in the stratosphere. Quadrennial Ozone
Symposium, IAMAP Programs and Abstracts, pp. 3-6, Int. Assoc.
of Meteorol. and Atmos. Phys., 1984.
Fels, S. B., J. D. Mahlman. M. D. Schwarzkopf, and R. W. Sinclair.
Stratospheric sensitivity to perturbations in ozone and carbon
dioxide: Radiative and dynamical response, J. Atmos. Sci., 37,
2265-2297, 1980.
Fenical, W.. Natural products chemistry in the marine environment,
Science, 215, 923-928, 1982.
Fishman. J., V. Ramanathan, P. J. Crutzen, and S. C. Liu, Tropo-
sphenc ozone and climate. Nature, 282, 818-820, 1979a
Fishman, J.. S. Solomon, and P. J. Crutzen. Observational and theo-
retical evidence in support of a significant in-situ photochemical
source of troposphenc ozone, Tellus, 31, 432-446, 19796.
Goldman, A.. F. S. Bonomo, and D. G. Murray, Statistical band
model analysis and integrated intensity for the 11.8 urn band of
CFC13, Appl. Opt., IS, 2305-2307, 1976a.
Goldman, A., F. S. Bonomo, and D. G. Murray, Statistical band
model analysis and integrated intensity for the 10.8 urn band of
CF2C12, Geophys. Res. Lett., 3, 309-312, 19766.
Goldman, A., D. G. Murray, F. J. Murray, G. R. Cook, J. W. Van
Allen, F. S. Bonomo. and R. D. Blatherwick, identification of the v3
vibration-rotation band of CFt in balloon-borne infrared solar
spectra, Geophys. Res. Lett., 6. 609-612. 1979.
Hameed, S., R. D. Cess, and J. Hogan, Response of the global climate
to changes in atmospheric chemical composition due to fossil fuel
burning, J. Geophys. Res.. 85, 7537-7545, 1980.
Hansen. J. E., A. Lacis, and S. A. Lebedeff. Commentary on climatic
effects of minor atmospheric constituents, in Carbon Dioxide
Review: 1982, edited by W. C. Clark, pp. 284-286, Clarendon Press,
New York, 1982.
Hansen. J. E., A. Lacis, D. Rind, G. Russell, P. Stone, 1. Fung, R.
Ruedy, and J. Lerner, Climate sensitivity. Analysis of feedback
mechanisms, in Climate Processes and Climate Sensitivity. Maurice
Ewing Ser. S, edited by J. E. Hansen and T. Takahashi. AGU,
Washington. D. C., 1984.
Herranz. J. R. de la Cierva, and J. Morcillo, Intensidades absolutas en
infrarrojo de bandes fundamentales del fluoroformo, chloroformo,
tnrluorclorometano y tnchlorofluormetano. An. R. Soc. Esp. Fis.
Quim. Madrid, ASS, 69-76, 1959.
Herrmann, J., and W. Jaeschke, Measurements of H2S and SO, over
the Atlantic Ocean. J. Atmos. Chem.. I, 111-124, 1984.
Hummel. J. R., and R. A. Reck, The direct thermal effects of CHC1F2,
CH3CC13 and CH2C12 on atmosphenc surface temperatures.
Atmos. Environ., IS, 379-382, 1981.
Kagann, R. H.. J. W. Elkins. and R. L. Sams, Absolute band strengths
of halocarbons F-ll and F-12 m the 8- to 16-jim region, J. Geo-
phys. Res.,88. 1427-1432, 1983.
Karol. 1., et al., Atmosphenc ozone and global climate. Report of
U.S./USSR Workshop on the Climatic Effects of Increased Atmo-
sphenc Carbon Dioxide, Leningrad. 1981
Kiehl. J. T., and V. Ramanathan. CO2 radiative parameterization
used in climate models: Companson with narrow band models and
with laboratory data, J. Geophys. Res., 88, 5191-5202, 1983.
Kley, D., J. W. Drummond. M. McFarland. and S. C. Liu, Tropo-
sphenc profiles of NO,,./. Geophys. Res.. 86. 3153-3161, 1981.
Lacis. A.. J. Hansen, P. Lee. T. Mitchell, and S. Lebedeff. Greenhouse
I
I
-------
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Paper 1
RAMANATHAN ET AL. : TRACE GAS CLIMATE EFFECTS
5565
effect of trace gases, 1970-1980, Geophys. Res. Lett., S, 1035-1038,
1981.
Levy, H., J. D. Mahlman, W. J. Moxim, and S. C. Liu, Troposphenc
ozone: The role of transport, J. Geophvs. Res., in press, 1985.
Liu, S. C., D. Kley, M. McFarland, J. D. Mahlman, and H. Levy II,
On the origin of tropospheric ozone, J. Geophys. Rev., 85, 7546-
755Z 1980.
Logan, J. A., Trends in tropospheric ozone, paper presented at
Second Symposium on the Composition of the Nonurban Tropo-
sphere, Williamsburg, Va., May 1982.
Logan, J. A., M. J. Prather, S. C. Wofsy, and M. A. McElroy, Atmo-
spheric chemistry: Response of human influence, Philos. Trans. R.
Soc. London, 290, 187-234, 1978.
Logan, J. A., M. J. Prather, S. C. Wofsy, and M. B. McElroy, Tropo-
spheric chemistry: A global perspective, J. Geophys. Res., 86, 7210-
7254, 1981.
Lovelock, J. E., Natural halocarbons in air and in sea. Nature, 256,
193-194, 1975.
Madden, R. A., and V. Ramanathan, Detecting climate change due to
increasing carbon dioxide. Science, 209, 763-768, 1980.
Manabe, S., and R. T. Wetherald, Thermal equilibrium of the atmo-
sphere with a given distribution of relative humidity, J. Atmos. Sci.,
24,241-259, 1967.
Maroulis, P. J., A. L. Torres, A. 8. Goldberg, and A. R. Bandy,
Atmospheric SO2 measurements on Project Gametag, J. Geophys.
Res^ 85, 7345-7349, 1980.
McClatchey, R. A., et al.. AFCRL atmospheric absorbtion line pa-
rameters compilation, AFCRL-TR-73-0096, 77 pp., Air Force
Cambridge Res. Lab., Hanscom Field, Bedford, Mass.. 1973.
Nanes, R., P. M. Silvaggio, and R. W. Boese, Temperature depen-
dence of intensities of the 8-12 ion bands of CFC13, J. Quant. Spec-
tros. Radiat. Transfer, 23, 211-220, 1980.
National Academy of Sciences/National Research Council, Halocar-
bons: Effects on stratospheric ozone, Washington. D. C., 1976.
National Academy of Sciences/National Research Council, Strato-
spheric ozone depletion by halocarbons: Chemistry and transport,
Washington, D. C., 1979.
National Academy of Sciences/National Research Council, Causes
and effects of stratospheric ozone reduction: An update. National
Academy Press, Washington, D. C, 1982.
National Aeronautics and Space Administration, The stratosphere:
Present and future, NASA Ref. Publ. 1049, 1979.
National Research Council, Carbon dioxide and climate: A second
assessment, Report of the CO 2/Climate Review Panel, National
Academy Press, Washington, D. C., 1982.
National Research Council, Changing climate, Report of the Carbon
Dioxide Assessment Committee, National Academy Press, Wash-
ington, D. C, 1983.
Penkett, S. A., Nonmethane organics in the remote troposphere, in
Atmospheric Chemistry, pp. 329-355, Springer, New York, 1982.
Penkett, S. A., N. J. D. Prosser, R. A. Rasmussen, and M. A. K.
Khalil, Atmospheric measurements of CF4 and other fluorocarbons
containing the CF3 grouping, J. Geophys. Res., 86, 5172-5178.
1981.
Prather, M. J., M. B. McElroy, S. C. Wofsy, Reductions in ozone at
high concentrations of stratospheric halogens, Nature, 312, 227-
231, 1984.
Pugh, L. A., and K. N. Rao, Intensities from infrared spectra, Mol.
Spectros., Mod. Res., 2, 165-225, 1976.
Ramanathan, V., Greenhouse effect due to chiorofluorocarbons: Cli-
matic implications. Science, 190, 50-52, 1975.
Ramanathan, V., The role of ocean-atmosphenc interactions in the
CO2 climate problem, J. Atmos. Sci., 38, 918-930, 1981.
Ramanathan, V., Commentary on climatic effects of minor atmo-
spheric constituents, in Carbon Dioxide Review: 1982, edited by W.
C. Clark, Clarendon Press, New York, 1982.
Ramanathan, V., and J. A. Coakley, Climate modeling through
radianve-convective models. Rev. Geophys. Space Phys., 16, 465-
489, 1978.
Ramanathan, V., and R. E. Dickinson, The role of stratospheric
ozone in the zonal and sesonal radiative energy balance of the
earth-troposphere system, J. Atmos. Sci., 36, 1084-1104, 1979.
Ramanathan, V., L. B. Callis and R. E. Boughner. Sensitivity of atmo-
spheric and surface temperature to perturbations in stratospheric
concentration of ozone and nitrogen-dioxide, J. Atmos. Sci., 33,
1092-1112. 1976.
Rasmussen. R. A., and M. A. K. Khalil. Atmospheric methane:
Trends and seasonal cycles. J. Geophys. Res., 86, 9826-9832. 1981.
Rasmussen, R. A., L. E. Rasmussen, M. A. K. Khalil. and R. W
Dalluge, Concentration distnbution of methyl chloride in the atmo-
sphere, J. Geophys. Res., 85, 7350-7356, 1980.
Reck, R. A., and D. L. Fry, The direct effects of chlorofluoromethanes
on the atmospheric surface temperature, Atmos. Environ., 12. 2501-
2503, 1978.
Revelle, R. R., Methane hydrates in continental slope sediments and
increasing atmospheric carbon dioxide, in Changing Climate, sect.
3.5, pp. 252-261, National Academy of Sciences. Washington, D
C, 1983.
Rothman, L. S., and R. R. Gamache, A. Barbe, A. Goldman, J. R.
Gillis, L. R. Brown, R. A. Toth, J. M. Flaud, and C. Camy-Peyret.
AFGL atmospheric absorption line parameters compilation: 1982
edition, Appi. Opt., 15, 2247 -2256. 1983.
Rotty. R. M.. and G. Marland. Constraints on carbon dioxide pro-
duction from fossil fuel use, paper presented at the Energy/Climate
Interactions Workshop, Munster. Germany, March 3-8, 1980.
Rudolph, J., and D. H. Ehhalt, Measurements, of C2-C,, hydro-
carbons over the North Atlantic, J. Geophys. Res., 86. 11959-11964.
1981.
Saeki, S., M. Mizumo, and S. Kondo, Infrared absorption intensities
of methane and fluoromethanes. Spectrochim. Ada Part A, 32. 403-
413, 1976.
Simmonds, P. G., F. N. Alyea, C. A. Cardelino. A. J. Crawford. D. M.
Cunnold, B. C. Lane, J. E. Lovelock, R. G. Prinn. and R. A. Ras-
mussen. The Atmospheric Lifetime Experiment. 6. Results for
carbon tetrachlonde based on three years data. J. Geophys. Res,
88, 8427-8441, 1983.
Singh. H. B., and L. J. Salas, Peroxyacetyl nitrate in the free tropo-
sphere, Nature, 302, 326-328, 1983.
Singh, H. B., D. P. Fowler, and T. O. Peyton. Atmospheric carbon
tetrachlonde: Another manmade pollutant. Science, 192. 1231-
1234. 1976.
Singh. H. B.. L. J. Salas, and R. E. Stiles, Selected man-made haloge-
nated chemicals in the air and oceanic environment, J. Geophvs.
Res.. 88, 3675-3683, I983a.
Singh, H. B., L. J. Salas, and R. E. Stiles. Methyl halides in and over
the eastern Pacific (40CN-32CS), J. Geophvs. Res.. 88, 3684-3690.
1983ft.
Smagormsky, J., Effects of carbon dioxide, chap. 4, sect. 4.1. in
Changing Climate, pp. 266-284. Report of the Carbon Dioxide As-
sessment Committee, National Research Council. 1983.
Sparrow, E. M., and R. D. Cess, Radiation Heat Transfer. 366 pp.
McGraw-Hill. New York, 1970.
Surgeon General, Health effects of toxic pollutants: A report from the
Surgeon General, Report prepared for U.S. Senate, Department of
Health and Human Services, Serial 96-15, Washington. D. C, 1980.
Turco. R. P.. R. C. Whitten. O. B. Toon, J. B. Pollack, and P Hamill,
OCS. Stratospheric aerosols and climate, Mature, 283. 283-286,
1980.
Varanasi. P.. and F. K. Ko. Intensity measurements in freon bands of
atmospheric interest, J. Quant. Spectros. Radiat. Transfer. 17, 385-
389. 1977.
Volz, A.. D, H. Ehhalt. and R. G. Derwent. Seasonal and latitudinal
variation of '*CO and the tropospheric concentrations of OH radi-
cals, J. GvopHys. Res.. 86. 5163-5171. 1981.
Wang, W. C., Ozone changes: Climatological effects, in Stratospheric
Ozone and Man. edited by F A. Bower and R. B. Ward. pp. 123-
135. CRC Press. Cleveland. Ohio. 1982.
Wang, W. C., Y. L. Yung. A. A. Lacis. T. Mo. and 1. E. Hansen.
Greenhouse effect due to manmade perturbations of trace gases.
Science. 194, 685-690, 1976.
Wang, W. C., J. P. Pinto, and Y. L. Yung, Climatic effects due to
halogenated compounds in the earth's atmosphere. J Atmos. Sci..
37. 333-338. 1980.
Washington, W. M., and G. A. Meehl, Seasonal cycle experiment on
the climate sensitivity due to a doubling of CO, with an atmo-
spheric general circulation model coupled to a simple mixed layer
model. J. Geophys. Res., 89. 9475, 1984.
Weiss. R. F., The temporal and spatial distribution of tropospheric
nitrous oxide. J. Geophys. Res.. 86. 7185-7195. 1981
Wine. P. H.. W. L. Chameides. and A. R. Ravishankara. Potential role
of CS, oxidation in tropo-iphenc sulfur chemistry, (jeuphvs Ret..
Lett..8. 543-546. 1981.
Wiscombe. W. and J. Evans. Exponential-sum titling of radiative
transmission functions. J. Comp. Phvsiol., 24. 416—444. 1977.
World Meteorological Organization. Report of the meeting of experts
on potential climatic effects of ozone and other minor trace gases.
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5566 RAMANATHAN ET AL.: TRACE GAS CLIMATE EFFECTS
WMO Global Ozone Res. and Monitoring Prof. Rep. 14, 35 pp., atmospheric composition and temperature structure, Ph.D. thesis,
Geneva. I982a. UCRL-53423, Univ. of Calif., Davis. 1983a.
World Meteorological Organization, The stratosphere 1981—Theory Wuebbles, D. J., Chlorocarbon emission scenarios: .Potential impact
and measurements, WMO Rep. II, Geneva. 19821). on stratospheric ozone, J. Geophys. Res., 88. 1433-1440, 1983ft.
World Meteorological Organization. The world climate research pro-
gram report on the meeting of experts on detection of possible R. J. Cicerone, J. T. Kieht and V. Ramanathan, National Center
climate change. WCP 29. edited by W. W. Kellogg and R. D. for Atmospheric Research, P. O. Box 3000, Boulder, CO 80307.
Bojkov, p. 42. Geneva, 1983. H. B. Singh, SRI International, Menlo Park, CA 94025.
Wuebbles. D. ].. Scenarios for future anthropogenic emissions of trace
gases in the atmosphere, UC1D-I8997, Lawrence Livermore Lab., (Received August 15, 1984;
Berkeley. Calif.. 1981. revised January 14, 1985;
Wuebbles, D. J., A theoretical analysis of the past variations in global accepted January 18,1985.)
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Evidence for a Greenhouse Effect
_
* by
• John Perry
National Academy of Sciences - National Research Council
t
This paper was based upon the presentation made at the workshop.
1
Trace Gas Trends and Climate Change
by
John Perry
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DRAFT 01/29/86
Presentation at Raleigh EPA Meeting
TRACE GASES AND CLIMATIC CHANGE
In contrast to the polished presentation made by Dr. Cicerone, mine
will be a more conventional sort of scientific talk with messy slides,
lots of wiggly lines, and at least one equation. As a card-carrying
meteorologist, I feel compelled to give you at the outset a weather
forecast. (Slide 1) This type of forecast that winter will follow
fall and summer will follow spring is in fact the most reliable type of
prediction we can make. This type of "prediction," the expectation of
future weather, is known as "climate." We think of the climate of the
globe, including its annual cycle and its distribution across the face
of the planet, as being a fixed part of geography. For example
(Slide 2), we find charts of various climatic parameters plotted on
maps with the same degree of authority and permanence as if they were
state boundaries or the distributions of geological or mineral
resources.
In fact, however, there is much evidence that the climate of the
earth is far from constant. Even a parameter such as the globally
averaged mean temperature of the planet is observed to change quite a
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bit in the long term, and exhibit rather puzzling fluctuations even
over short periods. For example, here (Slide 3) is a century-long
record of one estimate of the global mean temperature. It shows an
irregular increase over the period of record, and also some peculiar
shorter-term features such as the rise in temperature in the 1940s.
If we look a bit further back into history, I am sure we all recall
the tales in our schoolbooks about the great ice ages. About 18,000
years ago, great ice sheets extended over much of the northern
hemisphere and well down into North America and Europe. Much research
in recent years has focused on elucidating the details of these
climatic changes of the past. Here (Slide 4) is a reconstruction of
global sea-surface temperatures derived from deep sea sediment cores by
the CLIMAP group of researchers. The boundaries of sea ice coverage
derived in this way match very well with what we know of the land ice
cover in the same period.
Thus, by digging into the past, we have established quite a good
chronology of climate change in the relatively recent history of the
earth. Ice ages such as the one which culminated 18,000 years ago have
been duplicated many times in the Quaternary period in which we live.
The climate of this geological epoch has been characterized by swings
between glacial and interglacial conditions with a periodicity of about
120,000 years. The precise pacing of this oscillation seems to be
triggered by the characteristics of the earth's orbit, but the
mechanisms are not clear. Going back still further into mists of time
(Slides 5 and 6), we find that the earth has gone through a variety of
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different climatic regimes. By and large, however, it has stayed in
range in which life is possible. Our own period with its rapid
fluctuations between glacial and interglacial conditions is a bit
cooler than the period in which the great masses of fossil coal were
formed.
For these reasons, the title of a report issued a few years ago by
the National Academy of Sciences (Slide 7), Changing Climate, is quite
appropriate. We have to think of climate as a constantly changing and
perhaps a fragile element of our global environment. Such a viewpoint
leads us to another question: What determines our climate? The
fundamental governing factor, of course, is the relationship between
the earth and its parent sun that provides virtually all our energy.
It is relatively easy to estimate the temperature, that is the climate,
of an inert lump of rock located at the same distance as the earth from
2
the sun (Slide 9). The rock would receive about 340 w/m of energy
from the sun and would thus slowly warm. Elementary physics tells us
that the rock would radiate thermal energy back to space at a rate
proportional to the fourth power of its absolute temperature.
Eventually, it would warm to the point where it would be radiating as
much energy as it absorbed from the sun. A lump of rock with the same
reflectivity as our present earth would thus warm to a temperature of
about -18 C, significantly less comfortable than the real earth on
which we find ourselves.
The curves in the upper right hand corner of the slide show another
fundamental property of the energy balance. The energy coming in from
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the sun is primarily in the shorter wavelengths of light, around the
yellow part of the spectrum in which our own eyes are the most
sensitive. On the other hand, the rock, like any other warm body,
emits most of its energy in thermal radiation at a considerable longer
wavelength in the infrared. Thus, the balance of energy that maintains
its temperature is composed of two streams of radiant energy in very
different wavelengths.
The real earth, however, (Slide 10) is not a naked lump of rock
like the moon. Instead, it has a very peculiar sort of atmosphere
that, on the one hand, is essential for life and, on the other hand,
was largely made by life. Its components are nitrogen, oxygen, and a
small collection of trace gases. Among the most important of the
latter in the radiation balance of the earth are water vapor, which
varies widely in concentration, and carbon dioxide. These gases have
interesting effects on the way radiation is handled by the earth's
atmosphere (Slide 11). At the top of this illustration, we see again
the two curves showing the emission of energy by the sun and the earth,
respectively. Below, we see the absorption of energy in the atmosphere
in various wavelengths. One large open window of transmission neatly
underlies the visible input from the sun. Thus, solar energy is
admitted to the surface of the earth quite effectively. However, under
the peak of radiation from the earth, there is considerable absorption
by the atmosphere, indeed, almost total absorption.
The effects of the atmosphere can be readily discerned from
satellite observations. Here (Slide 12) is a series of measurements
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taken from a satellite flying over the Sahara and looking down at the
earth in different wavelengths in the infrared. The topmost dotted
line shows approximately the radiation one would expect to receive from
the earth's surface at the temperature of the Sahara. But what the
satellite actually saw was the lower trace, from which we see that
large portions of that radiation have been taken out by the
atmosphere. What one sees instead of the surface radiation is much
lower amounts of radiation from a much colder source up in the higher
atmosphere. Each of the dips in this curve, the slices taken out of
the energy coming from the earth, can be associated with individual
absorbing gases in the atmospehre. For example, large amounts are
taken out by water vapor, carbon dioxide, ozone, and methane.
If we now consider an earth surrounded by an atmosphere with these
properties, we find a very different type of energy balance
(Slide 13). Solar energy still comes in largely unabated, but the
radiation leaving the earth now is absorbed by the atmosphere in major
I
parts of the infrared spectrum. The energy balance with space is
• achieved in quite a different fashion. Only a small part of the energy
leaving the earth goes directly to space. The remainder of the energy
9 needed to balance the earth's accounts with the cosmos is provided by •
*t the atmosphere running at a much cooler temperature. The balance that
eventually evolves involves a warm earth's surface, about 15 C on the
B average, and a cooler atmosphere acting as a filter or blanket between
the earth and space. Largely for traditional reasons, this is called
f the "greenhouse effect," but actually it would be more appropriate to
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call it the "blanket" effect. Indeed, the situation is not unlike
sleeping in a chilly bedroom with a wool blanket.
This type of elementary physical reasoning may be tested very
easily by calculating what the greenhouse effect should be for the
different planets of the solar system given current understanding of
the nature of their atmospheres. With no atmosphere, calculation for
the moon is quite simple, and agreement with observations is
excellent. More impressively, for climates as different as Venus, the
Earth, and Mars, the arithmetic still works out quite well (Slide 14).
We find, for example, that Mars without an atmosphere would be quite
chilly at -56 C, but its puny atmosphere gives it about 3 worth of
greenhouse warming. On the other hand, the dense atmosphere of Venus
provides a massive greenhouse effect leading to truly torrid surface
temperatures. The major greenhouse gas on Venus is carbon dioxide, and
we have seen that CO is also present in small amounts in our own
atmosphere. Moreover (Slide 15), measurements of CO carried out by
Charles Keeling from 1958 to the present show steadily increasing
concentrations. Indeed, the data are sufficiently accurate for us to
perceive the annual respiration of the biosphere reflecting the fact
that the vast mass of forest lies primarily in the northern .
hemisphere. Still further back, recent Swiss work on glacial ice has
permitted quite a consistent reconstruction of past trends in carbon
dioxide concentration (Slide 16).
The principal reason for this increase in recent times is easy to
infer. Our modern society is taking vast reserves of fossil carbon
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• (Slide 17) that were entombed many millions of years ago and bit by bit
returning them to the atmosphere at the rate of 5 gigatons per year,
• Historically, it appears that about 50% of the emissions in each year
• from fossil fuel combustion has stayed in the atmosphere. The
remainder has been partitioned between the oceans and the terrestrial
• biosphere. The global carbon cycle that has been in operation since
the dawn of life on the planet is thus being perturbed on a major scale
I by human activities. The magnitude of this human influence can be
H assessed by looking at world figures on energy consumption and fossil
fuel use (Slide 18). Until quite recent times, the rate of increase in
• fossil fuel use was virtually exponential with no end in sight.
But what about the future? As is well known, prediction is a
• difficult exercise, particularly when it concerns the future.
— Nevertheless, a number of attempts have been made by various analysis
™ groups. The task is not easy. Fuel is consumed by society for some
• purpose of society. To estimate future fuel consumption, one must look
ahead 25, 50, or 100 years to determine what sort of society we will
• have, make some guesses as to what it will want to do in the world, and
how it will get its energy. Despite these difficulties, a number of
scholars have made valiant attempts to predict future energy and fossil
fuel consumption. Not surprisingly, their estimates of energy use,
fuel consumption, and carbon dioxide emissions diverge widely as one
goes out into the future (Slide 19). Some postulate a rapidly growing
and industrializing world society that burrows out of the ground every
last scrap of carbon. Others visualize a frugal future society relying
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largely on renewable energy resources. Thus there is a widening band
of uncertainty in future carbon use. A recent international conference
held in Villach, Austria, developed estimates of future carbon
emissions that were in a somewhat lower range than previous studies.
Their conclusions were heavily biased by recent experiences in energy
conservation in response to rising energy prices.
One can employ these emission estimates together with a carbon
cycle model of some type to make projections of future atmospheric
CO concentrations (Slide 20). Here the background chart shows a
range of estimates developed in the National Academy of Sciences study
referred to earlier. For comparison, I have crudely indicated the
estimates developed in connection with the Villach conference. The
lower band of estimates shows the range for CO alone. The higher
band shows the equivalent effect on the radiation budget that would be
produced by CO plus the other trace gases considered in their
survey. That is, this upper chart shows the amount of CO that would
be required to produce the same effect on the radiation budget as the
mixture of gases that are estimated to be present. Thus, in terms of
the total effect on climate, the other trace gases roughly double the
impact of C0_, and completely wipe out the beneficial effects of the
expected decreases in the rate of growth of energy demand. We are
essentially back to where we started. Indeed, the Villach estimates
would support the equivalent of a CO doubling effect on climate by
as early as the year 2030.
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Once we have an estimate of the future course of concentration of
C0? and other perturbing gases in the radiation budget, how can we
turn this into an estimate of future climate? The atmosphere is, after
• all, but one element of the complex global climate system (Slide 21).
To predict future climate, we must consider the ocean that not only
I acts as a chemical buffer but also exchanges heat and momentum with the
atmosphere. We must consider clouds whose distribution over the earth
|P and effects on the radiation budget are by no means well understood.
^ We must deal with the variations of ice and snow masses on an annual
basis and over long periods of time. Later presentations at this
I conference will deal with this challenging task.
By looking at the results of climate model simulations and the
• projections of future atmospheric trends, the Villach conference
— developed a number of conclusions of considerable significance
• (Slide 22). First, they confirmed strongly that it is time to move out
• of the purely scientific arena in discussion of the issue of greenhouse
gas trends. Implications of changes in atmospheric composition and
• global climate should be taken account of in practical policy
development, not necessarily from the standpoint of taking immediate
|§ action but certainly in laying the groundwork for future actions should
•| they become necessary. To support this effort, the conference
^ recommended stronger public information activities and, of course,
continued research. They believed that this research should be pursued
with equal vigor on both the scientific front to elucidate the details
of climate change, and on the policy front to examine policy and
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10
economic options. The conference believed that it was high time to
arrange for more frequent and more intense interactions between
scientists and policy people in the study of the implications of
greenhouse gas increase. They suggested a number of specific
scientific and policy research topics and the establishment of a
standing international task force sponsored by the three major
sponsoring agencies of the assessment— the World Meteorological
Organization, the International Council of Scientific Unions, and the
United Nations Environment Program. This task force would arrange for
future assessments of the issue at appropriate intervals and would
provide advice to governments and international organizations. The
group would also begin the consideration of a global convention to
attempt regulation of all the greenhouse gases. The most important
conclusion of the conference, I believe, was that "our understanding...
is sufficiently developed that scientists and policymakers should begin
an active collaboration to explore the effectiveness of alternative
policies and adjustments."
In conclusion, the true message of the greenhouse gas problem was
most clearly stated a long time ago and not by an atmospheric scientist
but by a distinguished Soviet mineralogist (Slide 23). Vernadsky saw
that in this century mankind has colonized the geographical map of the
planet earth and its whole surface to become a large-scale geological
force. Our challenge is to learn how to control and focus that force.
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IS &R WINTER QGCOMfHS
SPXiNG, TWMNG Id SUMM&?
LATER IMTiJE YEAR, THEN
FiNA UYBHZK ^> HMTER //
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MAW TRENDS M GLOBAL CUMATE: THE PAST MUJON YEARS
LAND TEMPERATURE
COLD
OCEAN TCMKRATUtt
COLD WARM
CUMAL MX VOLUME
MIN
g
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Fig. 51
Here we see climatic variations characteristic of the major components of the climate system,
the land, sea, and ice. A major challenge remains in integrating these complex histories into
one coherent picture.
The information in Figure 51 shows climatic variations on three different time scales. For the
last 30,000 years we see the major change between a glacial world and an interglacial one. Over
the last 150,000 years, some details of the change between one interglacial and another are
identified. And, on a time scale of 1 million years we can see that such glacial-interglacial
changes are part of a repeating cycle. While there is much to infer about the dynamics of
climate from time histories, let us highlight one aspect of these data. Notice, for the period
about 6,000 years ago, the Earth's climate was warmer (by several degrees) than today. This
interval of time may be of particular importance in providing a perspective on the current CO2
problem. Let me explain this, and at the same time illustrate a second part of our work in the
area of global climatic record namely that of climatic reconstructions on a regional scale.
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PHANER020IC CLIMATE
Period Cold
< 65
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QUATERNARY
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CAMBRIAN
Figure 1. A schematic global temperature history of the earth for the
Phanerozoic.36
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Changing
Climate
Report of the Carbon Dioxide Assessment Committee
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in
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I COMPOSITION OF THE ATMOSPHERE
• Nitrogen (N) 78%
• Oxygen(O) 21%
Argon, Hydrogen, etc. <1%
| Water Vapor (HaO) 0-4%
Carbon Dioxide (CO2) -0.3%
| (-300 ppm)
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The Greenhouse
Looking
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Figure 17. The Earth's » Lac*.-body emission spectrum At
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at various temperatures are superimposed.
(From Hanel et al., 1971).
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1700
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Figure 3.3 Atatospheric CO. concentrations Measured in glacier ice
formed during the last 200 years (Neftel et al, 1965).
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Other
Trace
Gases
C02
9123
tfTS 2000 2025 2060
YEAR
2075
2100
FIGURE 2.4 Atmospheric concentration of carbon dioxide (5th, 25th,
50th, 75th, and f 5th percentilesi parts per million). The indicated
percentile runs for concentrations; the numbers on the right-hand side
indicate concentrations in the year 2100 foe >ach rwn.
(Villach, 1985)
TABLE 1.2 Indices of Sensitivity of Atmospheric Concentration in 2100
to Uncertainty about Key Parameters*. (100 • Level of Effect of Host
Important Parameter^}
•arginal Variance
from Most
Likely Out
Base of substitution between fossil
and nonfossil fuels
General productivity growth
Trends in real costs of producing energy
Base of substitution between energy and labor
Airborne fraction for 002 •»*«*iom
Extraction costs for fossil fuels
Population growth
Fuel mix among fossil fuels
Trends in relative costs of fossil
and nonfossil fuels
Total resources of fossil fuels
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I UNEP/WMO/ICSU CONFERENCE
VILLACH, OCTOBER 1985
• It Is Time To Take Greenhouse Cases Into Account In Policy
I Development
• Public Information Efforts Are Needed
• • Research Is Needed On Both Scientific And Policy Fronts
• - Climate (Global Change, WCRP)
- Analysis Of Policy And Economic Options
| • Specific Research Topics
• International (WMO/ICSU/UNEP) Task Force
• - Assessments
• - Advice
- Consideration Of A Global Convention
".. .(ll)nderstanding... j$ sufficiently developed that scientists and
I policy-makers should begin an active collaboration to explore the
effectiveness of alternative policies and adjustments."
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"In the twentieth century, man, for the first time in the history of the earth, knew and embraced the
whole biosphere, completed the geographic map of the plant Earth, and colonized its whole surface.
Mankind has become a single totality in the life of the earth....(F)or the first time man becomes a
large-scale geological force. He can and must rebuild the province of his life by his work and
thought....Wider and wider creative possibilities open before him. It may be that the generation of
our grandchildren will approach their blossoming."
W.I.Vernadsky
The Biosphere and the IMoosphere,
American Scientist, 33, No.1.,
January 1945
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• Papers
Past and Future Changes in Climate
| by
David Rind
• NASA/Goddard Institute for Space Studies
I This paper was based upon the presentation made at the workshop.
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I Climate Modeling and Climate Change
by
| David Rind
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The following represents an edited version of a talk given at
the EPA Workshop on Global Atmospheric Changes, November 5,
1985.
• Paper 3
• CLIMATE nODELING AND CLIMATE CHANGE
• D. Rind
• Goddard Space Flight Center
I Institute for Space Studies
• 2880 Broadway
New York, N.Y. 10025
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Introduct ion
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_ The focus of this talk will be on uhat climate change we
• may expect in the next 35 years. To put the conclusions in
• the proper perspective, however, it is necessary to
understand the uncertainties that go into the models that are
V being used to provide this estimate. Thus we will first
discuss how climate models are constructed, and what problems
• are involved. Ue will then review the physics of the climate
• system, to explain why climate is expected to change. At the
end we will show preliminary results of an experiment made to
• assess future climate changes.
m C1imate Model ing
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The word climate means different things to different
people. Scientifically it refers to the time-averaged
weather, but in practice each individual extracts from the
concept that which is most appropriate to his needs. For
people concerned with air pollution, climate refers to the
normal wind velocity responsible for dispersal. To the "man
in the street" climate probably refers to the mean
temperature, primarily. For ski resort ouners, it will be
snoufal1 amounts, for farmers, rainfall and grouing season
degree days. The climate system is very diverse. If one wants
to model the system fully, it is necessary to include all the
elements that interact and whose change could be of
importance to the general community.
The physics of climate modeling is, on the surface,
straightforward. There are only a few conservation laws,
i.e., fundamental equations, which require solution. These
equations represent the conservation of momentum, energy,
mass and moisture (Fig. 1). A representative application of
these equations provides an answer to the question of why
temperature will change in a given area with time. For this,
one uses the equation for the conservation of energy. The
change with time of energy (or temperature) (on the left-hand
side of the equation) results from the occurrence of heating
or cooling processes (on the right-hand side). For example,
the sun's radiation warms the air during the daytime, while
at night the only radiative process involves energy being
lost back to space ("long-wave" radiation). The change of
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temperature or energy uill be positive during the day from
the radiative processes, and negative at night. The actual
change depends upon the sum of all the heating and cooling
processes; the air can uarm uhen there is a flux of heat from
the ground, uhen uater vapor condenses, or uhen uind brings
in air uith a higher temperature. To knou uhat the uind
direction uill be requires solution of the conservation of
momentum equation, and to knou if uater vapor uill condense
in the atmosphere requires the solution of the equation for
conservation of moisture. The equations are thus coupled
together, and must be solved simultaneously. This brings up
the first of the problems : these "non-linear, partial
differential" equations cannot be solved analytically. One
has to obtain an approximate solution via the computer using
numerical techniques.
The method of solution involves "discretization". The
• differential equation indicates the instantaneous change uith
~ time of temperature, uind or humidity; the numerical solution
M. solves for the change over a finite length of time, generally
ranging from five minutes to an hour. Similarly, the
• advection of air uith a different temperature into a region
in the fundamental equation involves an infinitely small
« spatial change; the numerical equation calculates gradients
• on much coarser scales, dividing the earth into finite "grid
boxes" (e.g., Fig. 2). It is important to realize that this
• procedure has changed the equation. Ue have departed from the
full differential equation, uhich is exact, to an
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approximation of this equation in "finite difference" form.
The closer one approaches the differential equation, i.e.,
the smaller the temporal and spatial scales employed, the
more accurate the solution. In practice, these equations must
be solved over the entire earth for a number of years uhen
making climate projections, thus relatively large finite
distance grids have to be employed. So the first problem is
that ue are only obtaining an approximate solution to the
fundamental equations.
The grid boxes shoun in Fig. 2 emphasize another
limitation of climate modeling. The size of this grid is
often very coarse compared to the usual scales of concern.
For example, if one is interested in the pollution of a lake
in a specific area, the lake uill likely represent an
extremely small portion of the grid box. Due to the increase
in computer time needed to produce calculations on very small
spatial grids, it is not practical to attempt to solve for
climate change on the scale of the lake. The natural
variation within the grid box provides some estimate for hou
representative the grid box solution is to that particular
1 oca!e.
The second problem involves the calculation of the
"source" terms of energy, momentum and moisture on the
right-hand side of the equations. Hou are processes such as
absorption or emission of radiation, fluxes from the surface
or condensation of moisture to be calculated? For computing
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• purposes it is necessary to find some numerical formulation
for each of these physical events; houever, in many cases,
9 the precise mechanisms involved are imperfectly known. Ue
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thus use approximate equations to model these processes,
often relating occurrences which take place on very small
scales to the large grids used in climate models. Ue are
"parameterizing" the physical process, and to the extent that
the parameterization is not an accurate representation of
reality, we are introducing additional errors into the model.
• The types of processes which need to be parameterized in
each grid box are shown in Fig. 2 (bottom). Included are
ft calculations of variables as diverse as cloud cover, the
radiative effect of atmospheric aerosols, and fluxes of heat
• and moisture within the ground. The physics of each of these
» tends to be quite complicated, and many involve
interdisciplinary research areas. For example, moisture is
• drawn from the ground by plants. Understanding the exact
mechanism is the goal of botanists, plant physiologists and
V soil scientists. How deep do the roots go into the ground,
and what is their rooting density? Exactly when and under
what conditions are plants activated in the spring?
v Atmospheric scientists who have developed the climate models
need to work in conjunction with researchers from these
disciplines, who are often used to viewing the problems on a
much smaller spatial scale and with a different perspective.
In the climate model developed at GISS (NASA Goddard
Institute for Space Studies) we have incorporated a 1°
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representation of the vegetation over the surface of the 1
earth; the distribution over North America is shoun in Fig.
3. The impact this vegetative cover has on the climate model J
is most apparent over desert regions, uhere there is little
vegetation present to drau moisture out of the ground. A
truly proper representation uould include concepts such as
crusting of the desert surface uhich inhibits infiltration.
The future of climate model development involves interaction
uith many different disciplines to help quantify these
effects.
Climate Model Output
There are essentially three climate models being used
for long-term climate simulations in the United States. The
models are located at Princeton (the GFDL model), at NCAR
(National Center for Atmospheric Research), and at GISS. The
models handle the processes ue have been describing in
someuhat different uays, although the approaches are
generally conceptually equivalent. The major task of each
modeling group is to justify their parameterizations and
numerical schemes by comparing the output of their model to
observed climate parameters. Shoun in Fig. 4 is a comparison
of the GISS model simulation of precipitation, for the annual
average, uith observations. The model successfully reproduces
many elements of the observed precipitation field, including
the dryness in desert regions and off the uest coast of
continents, uhile rainforest areas are uet. Also shoun is the
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interannual variability of rainfall. Not only must the models
accurately simulate today's climate, they must have the same
variability if they are to be used to assess future climate
changes. The model results appear realistic except for
reduced variability over the oceans. This introduces another
difficulty; the oceans are an essential part of the climate
system, and ocean changes uill impact climate (as climate
changes uill impact ocean circulation). Ocean modeling is in
a very primitive state, and most climate models use very
simplified ocean models. The results presented here mere
derived uith the sea surface temperatures specified from
observations of their climatological norm; since no
variability is introduced in the year-to-year specifications,
events such as El Nino, are not introduced. This then is
responsible for a major portion of the reduced rainfall
variability over the ocean in the model.
Fig. 5 shous the surface air flou generated by the model
for January (top) and July (bottom). At 1ou latitudes the
trade uinds b1ou from uest to east and touards the equator in
the uinter hemisphere. During July, the model simulates the
monsoon circulation, as air is suept onto the Indian
subcontinent bringing rain. These features are realistic
representations of the actual flou field. All the basic
models simulate the current climate in a reasonable fashion,
although none are perfect. If one compares the model output
uith enough different types of observations, the model has to
be realistic in an absolute sense to reproduce all of them.
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In practice, one discovers certain aspects that are
inaccurate, uihich then become the focus of further model
development•
Fig. 6 displays the model uind at the jet stream level,
uhere the atmospheric pressure has been reduced to about 0.2
of what it uas at the surface. The Jetstream is a region of
strong west to east flow at that level; in the figure the
circled region is uhere the Jetstream is most intense. Again,
this is a relatively realistic assessment of the actual
Jetstream. Ue have now introduced another factor: the
atmosphere is three-dimensional, and therefore the
discretization involves not only the horizontal grids but
also vertical levels. In addition to horizontal winds, the
atmosphere also features vertical advection, most strongly
concentrated in convective areas (e.g., thunderstorms). To
complete the point we may also note that the ground is also
divided into vertical layers for calculations of the movement
of water and heat within the soil.
Elements of the Climate System
To be able to predict how climate will change in the
next 35 years, we must know what the sensitivity of the
climate system is. Studies of past climates
(paleoclimato1ogy) provide the major source of evidence in
this regard. Therefore, modeling past climates, for example
the climate of the last ice age, allows us to evaluate
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through the model's perspective hou the various elements of
the climate system change, and hou they feedback to amplify
or diminish initial perturbations. Ue utilize the estimated
boundary conditions derived for the peak of the last ice age,
about 18,000 years ago. This includes the sea surface
temperatures, sea ice, land ice and orbital parameters for
that time. These boundary conditions are established by
various techniques, often involving deductions of past
temperatures from fossil or geologic evidence.
_ In Fig. 7 ue show the change in surface air temperature
™ between the ice age climate and that of today for the annual
• average, as produced by the GISS climate model.. Large
temperature changes occur in the vicinity of the ice sheets,
while at low latitudes, due to the uarmth of the estimated
sea surface temperatures, little cooling occurs. Whether low
latitudes really mere this warm during the last ice age is a
matter of some debate.
• The global average temperature change in the model
produced in this experiment is close to 4°C; global surface
air temperature changes of this magnitude uere associated
•* uith the advance of ice sheets to Long Island. In the
simulation, the insertion of the ice sheets and colder ocean
temoperatures force the model to produce a colder climate.
Houever, additional feedbacks arise (Fig. 7, bottom). For
example, a colder atmosphere can hold less moisture; uhen the
atmosphere cools, not as much uater vapor is evaporated from
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the oceans. Uater vapor is a very effective greenhouse gas,
absorbing energy radiating from the earth, so with less
moisture in the atmosphere more energy escapes, and the
atmosphere cools further. The water vapor reaction is an
example of a positive feedback inherent in the system - as
the climate cools, there is less water vapor, which cools the
climate more, which results in even less water vapor, and so
on. There are other such feedbacks in the system. For
example, when ice replaces vegetation as the surface land
feature, it increases the reflection of solar radiation back
to space. There is thus less available energy to warm the
climate, and temperature is reduced. Lower temperatures allow
more ice to form, and again, the cooling is accentuated.
Carbon dioxide in the atmosphere was apparently less
abundant during the last ice age. If C02 was reduced prior to
the beginning of the ice age, then it could have helped
initiate the ice age. If the reduction occurred after the
start of the ice age, then it is another example of a
positive feedback: a reduction of CQ2 lessens the greenhouse
capacity of the atmosphere, which would cool the climate
further. The primary generating mechanism for ice ages is
thought to be variations in the orbit of the earth,
especially those changes which produce less solar radiation
at upper mid-latitudes of the Northern Hemisphere during
summer. Cooler summers would allow ice to remain throughout
the year, and therefore to grow. This direct forcing is
relatively small, especially on the global average, and the
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implication is that the 4°C cooling results primarily from
the positive feedbacks (Fig. 7, bottom). The orbital
perturbations are long lasting, with variations on the order
of 20,000 to 100,000 years, so the feedbacks in this case are
those applicable to long-term climate perturbations. But if
the climate system can amplify initial perturbations of
shorter time scales then this will effect the future climate.
Future Climates
Uith the current rate of atmospheric COz increase, an
effective doubling of the 1958 atmospheric COz concentration
should occur during the next century. To understand the
future climate sensitivity, the climate model has been run
with doubled atmospheric C02 concentration, allowing the
ocean temperatures to adjust to the new radiative balance.
The annual average surface air temperature changes which
arise are shown in Fig. 8, as well as the feedbacks which
have augmented the warming. Large increases in temperature
are seen at high latitudes; this is partly the result of
reductions in sea ice which reduce the reflectivity of the
surface and allow heat from the ocean to warm the winter
atmosphere. In addition, the greater natural stability of the
colder regions trap the added heat near the surface, and thus
exaggerate the surface air temperature change. These changes
represent the model's equilibrium result; for the feedbacks
to become fully involved requires allowing the ocean
temperatures to respond. The ocean has a large thermal heat
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capacity, so its temperature changes only slowly. It was
necessary to integrate the model for a simulated 35 years to
arrive at the full equilibrium result. Even after the
equivalent of doubled atmospheric C02 is achieved, some time
will still elapse before the effect is felt in full.
The three different climate models all produce a warming
of about 4"C when their atmospheric CCk concentration is
doubled. However, in the GFDL model with fixed clouds (and a
few other changes) the warming is only about 2°C. This
underlines the importance cloud changes can have on climate
sensitivity. Reduction of low level clouds, as occurs in
these model runs when climate warms, reduces the reflectivity
or albedo of the system, allowing more solar radiation to
reach the surface- In addition, there is some tendency for
upper level clouds, relatively thin cirrus clouds, to
increase. Cirrus clouds act as an additional greenhouse
component by absorbing the long wave radiation from the
planet. Both of these cloud feedbacks are thus positive,
amplifying the climatic warming in the model. There is little
confidence that the models are parameterizing clouds in a
realistic way, so this aspect of the climate sensitivity
assessment represents a major uncertainty. A project has been
organized by the World Meteorological Society to observe from
satellites the present-day cloud climatology, which could
then be used to determine if cloud cover is changing.
On more local levels, and for other climatic variables,
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there is less agreement among the models. This implies ue can
have less confidence in such results. The uncertainties in
climate model parameterizations are probably more important
uhen considering results at smal1-seales. This precaution
applies, for example, to the following discussion. Uhat are
the local expressions of a 4°C global temperature change? In
the model low latitudes experience less of a variation than
do higher latitudes, in both the ice age and doubled C02
simulations. There are also seasonal variations to the global
warming, with winter hemispheres more affected. The 4° C ice
age cooling was associated with ice year-round in New York.
To put the 4"C warming in perspective, we have looked at the
impact of the model-generated temperature change on the
summertime temperatures in different American cities. The
procedure involved adding the mean monthly temperature
difference to the observed daily summer temperatures,
assuming the patterns of day-to-day variability remain
unchanged.
• Some results of this study are shown in Fig. 9, For
example, in Omaha there are currently 3^ days during the
|| summer in which the temperature rises above 100°F. For the
_ doubled C02 climate, this number increases to 20^ days. For
" Washington D.C., there are currently 0.7 days of above 100°F
readings; in the doubled CCb climate there are 11.6 days. The
results for temperatures above 90" F are even more dramatic.
Omaha experiences an increase from the current 36.6 days to
85.5 days above 90°F. Ue can also look at the nighttime
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temperatures : in Omaha there are nou 0.2 days/year in which
the temperature at night does not fall below 80°F. For the
doubled COa climate this occurs 9.4 days/year. In Washington
D.C. the current number is 0.4 days/year, which increases to
19 days/year uith doubled CO? « It is probable that such
changes would necessitate shifts in patterns of energy
consumption across the country, including both seasonal and
diurnal distributions.
COz is only one of the atmospheric trace gases uith
greenhouse significance uhich has been increasing. In Fig. 10
ue provide an assessment of the relative importance for
warming or cooling of various potential forcing factors. It
also provides a comparison uith other components of the
climate system uhich may affect the surface temperature. The
direct effect of doubling C02 is similar to that of a 2%
increase in the solar constant. Small fluctuations of solar
input have been observed but nothing of that magnitude,
although precise observations have been made for only a short
time. Other trace gases uhose increase effects the greenhouse
capacity are methane, freons and nitrous oxide. The effect of
increases in tropospheric aerosols is more complex; if the
aerosol is soot (carbon particles), and if the optical
thickness is increased by only a small amount, then the
additional aerosols will help uarm the climate. If the
aerosol is made of sulfuric acid, a small increase uill cause
cooling of the climate. There is currently some uncertainty
as to whether tropospheric aerosols are increasing away from
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urban areas, and, as these calculations show, the climatic
impact will depend upon the nature of the aerosol.
Stratospheric aerosols associated most often with
volcanoes tend to cool the climate. However, volcanic
aerosols tend to fall out of the atmosphere within several
years. Volcanic aerosols are thus a short-term climatic
perturbation, and illustrate that the effect on this time
scale is muted compared to that of longer-lived
perturbations. The residence time of the volcanos is too
short to allow the ocean to cool substantially, and this
limits the capability of the subsequent feedbacks (such as
reduced evaporation) to become involved. Again, the positive
feedbacks discussed previously require that the whole system
be given time to react. The potential influence of two of
these feedbacks, cloud cover and land albedo, is also
illustrated in this figure.
Transient Response
Uhat has been the effect of the known climatic
perturbations in recent decades? Shown in Fig. 11 are the
decadal increments of greenhouse forcing that has or will
occur (given reasonable projections) through the 1980s. Uhat
is most obvious is that, ignoring water vapor and ozone
changes which are uncertain, the equilibrium impact of
increasing trace gases other than COz is cumulatively of the
same order as that due to increasing C02 • The anthropogenic
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impact on climate is clearly not simply a C02 problem. This
predicted equilibrium change has not yet been fully realized,
as, again, the ocean must be given time to respond. If the
heat entering the ocean can diffuse belou the surface mixed
layer into deeper levels, then it increases the ocean heat
capacity and requires that the ocean will warm even more
slouly. Fig. 12 presents an estimate of how the climate would
have changed between 1850 and 1980 due to the estimated C02
increase were the equilibrium response evident (top line), or
diffusion to deeper levels in the ocean occurring. The
difference, which depends on the climate sensitivity to
doubled COz , represents the unrealized uarming already built
into the system due to the lag in the ocean response. If the
ocean temperature change has not kept up with the atmospheric
concentration change, then the system is not currently in
radiative balance - more energy is coming in than is going
out. This implies the oceans uill continue to uarm and so
will the climate, even if no additional changes in
atmospheric composition occur. As
anthropogenical1y-inf1uenced trace gases are likely to
continue to increase, the system uill get further out of
balance, which indicates that the observed conditions will
become less and less indicative of the ultimate response. The
magnitude of this discrepancy will depend on the climate
sensitivity and the actual heat capacity of the ocean.
To estimate what the climate change may be like over the
next 35 years, we returned to the atmospheric composition
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prevalent in 1958 and changed C02 , stratospheric aerosols,
and other trace gases in the observed fashion through 1985.
For projections into the future, in case A, ue kept the
grouth rates for the trace gases at their current levels. The
greenhouse forcing for this case, as uell as for a reduced
grouth rate scenario (case B) is shoun in Fig. 13. Note that
the equivalence to a doubled CCb forcing occurs around 2030,
although the equilibrium response uill lag by at least
several decades. The simple ocean model employed uses
specified ocean heat transports; it allous diffusion through
the bottom of the oceanic mixed layer uith a diffusion
coefficient calculated so as to match the vertical dispersal
of oceanic transient tracers, such as tritium from atomic
explosions. While several large volcanos occurred in the time
period from 1958-1985, and are thus included, for the future
projections for case A ue simply use the mean value of the
volcanic aerosol optical depth averaged over the last 100
years.
Some results of this experiment are shoun in Figs. 14
and 15. The model indicates that an unambiguous uarming uill
occur over the next several decades. The model sensitivity
and simulation from 1958 to 1985 is in reasonable agreement
uith the observations (Fig. 14). By the mid-1990s the model
indicates there uill be a global average surface air
temperature change of about 1°C. For the eastern United
States a temperature increase approaching 2°C is reached by
2020 (Fig. 15). Uarming of this magnitude is unprecedented
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during recorded history, and in the model simulation is
occurring very rapidly. If such changes actually do take
place, they would exceed the natural variability of the
system, and be an unmistakable indication that the trace gas
effect uas proceeding as expected.
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ft F»«f» 1. Fundamental equations.
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m Conservation of momentum: dV _,
• (Newton's second law of & ~ ~ p P
motion)
| + g + F (Tl)
Conservation of mass: dp _
• (continuity equation) — = -pV • V + C - £> (T2)
Conservation of energy: dj_ _ dp]
(first law of
thermodynamics)
Ideal gas law: p = pRT (T4)
(approximate equation of
state)
uiioci vauuu ui ciicigy. u^ up ._
I (first law of 7t~ ~P~dT + Q (T3)
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Notation
IV velocity relative to rotating earth
t time
— — total time derivative = — + V • V
A dl I dl J
Q planet's angular rotation vector
IP atmospheric density
g apparent gravity [=true gravity — Q X (0 X r)]
r position relative to planet's center
IF force per unit mass
C rate of creation of (gaseous) atmosphere
D rate of destruction of atmosphere
§/ internal energy per unit mass [=cvT]
Q heating rate per unit mass
R gas content
cc specific heat at constant volume.
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1
Pig. 2 .. Grid spacing for the 8 x 10° model. The shading indicates a
particular choice of the regions for which special monthly diagnostics
are produced. The four black regions are a particular choice of the
grid-points for which special hourly diagnostics are produced.
'••"•: •'• •'. '• .'' j stratospheric aerosols' ;'•'•'•' :.'-:' •':'•:'•';'
£ large-scale supersaturation cloud S
convective cloud N
i y-
—13 C
r n
radiative
constituents :
H20,C02,0,,
— — trace gases,
clouds,
aerosols
latent and
sensible heat and
heat fluxes moisture . ,
I 1 i I sforafl* } |
I ' •_ ' \^~^niii-«« ICC
"CEAN OCCAM ICE UANON T"^^Z.(dJ«r««ll
Pig. ^ • Schematic illustration of the model struc-
ture for a single grid-point.
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FlG. 3 . 32-component vegetation classification based on 1 x 1 ° vegetation file of E. Matthews. Legend: 1
= tropical rain forest, 2 = tropical/subtropical evergreen seasonal forest, 3 = subtropical rain forest, 4 = temperate
rain forest, 5 = temperate evergreen seasonal forest, 6 = dry evergreen forest. 7 = subtropical evergreen needle-
leaved forest, 8 = temperate evergreen needle-leaved forest, 9 = drought deciduous forest, A = cold-deciduous
forest with evergreen trees, B = cold-deciduous forest without evergreen trees, C = xeromorphic woodland, D
= dry evergreen woodland, E = evergreen needle-leaved woodland. F = drought-deciduous, G = cold-deciduous
woodland, H = evergreen broad-leaved shrubland. I = evergreen microphyllous shrubland. J = drought-deciduous
shrubland, K = cold-deciduous shrubland. L = xeromorphic shrubland, M = tundra, N = grassland: 10-40%
treecover, O = grassland < 10% tree cover. P = grassland: shrub cover. Q = tall grassland, R = medium grassland,
S = short grassland, T = meadow, U = desert. V = ice, W = cultivation. The different vegetation types contribute
proportionally to each 8 X 10° grid. The hatched box defines the latitudinal belt encompassing most of the United
States.
(after Matthews, E., J. dim. and App. Meteor., 22, 474-483, 1983)
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Paper 3
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Paper 3
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Paper 3
A Surf act Air Temperature (*C)
I8K-Control
H80
•120
•60 0 60
Longitude (degrees)
Contributions to Cooling of
Last lee Age (18KD
180
2
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.
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Saa Vagatatlon COj
lea Orbital
Cloud. - Varutlon.
•loud portion dopanda
vary modal on
mainly dapandt on
CLIMAP ACO2
dapandant data
Fig.7- Annual mean surface air temperature difference between the climates of
today and the Wisconsin ice age (18,000 years ago), based on 3-0 climate model
simulations with the CLIMAP boundary conditions (paper 2). Areas in which the
cooling exceeded 5°C are stippled, while areas with wanner temperatures at 18K
are indicated by slashes. The contributions of different physical processes to
the global mean cooling at 18K are shown in the lower part of the figure, as
estimated by inserting individual changes of boundary conditions into the modal.
(from Hansen et al., 1986, in C07 and Changing Climate, EPA/National Fores
Products Association, in press"]
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Paper 3
GLOBAL WARMING IN 3-D MODEL FOR DOUBLED C02
& Si*foe« Air T«mptrohir« PC) OouoUd COt
to
HBO H20 -«O O CO
Longitude (degrees)
120
I
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CONTRIBUTIONS TO GLOBAL WARMING IN MODEL
CO, H,0 H,0
Is 2) UL33) Vtrtieol
Oianbulion
Ground Cloud Cloud
Albedo Htioht Cow
t-0.009) C-!.7%)
. Annual mean wanning obtained in a 3-0 global climate model (GISS model,
described in papers 1 and 2) at equilibrium (t*-) for doubled atmospheric C02-
Lower part of figure shows contributions of different physical processes to the
global warming, as estimated by inserting the changes in the 3-0 model into a l-o
(after Hansen
it al. , 1986 as in Fig. 1}
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Paper 3
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Fig. 9. (from Ashcraft and Hansen, 1986, submitted to Science)
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Paper 3
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Paper 3
0.10
0.08
0.04
0.02
Decadal Increments of Greenhouse Forcing
C02
4.2
ppm
str.H20
C02
8.2
ppm
C02
12.8
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03
_ str.
••.«.«
CFCs :
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15.6
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••• **
CFCs
'12
N,0
CH4
1850 -I960
(per decade)
I960 s
I970's
I980's
FlgJl . Decadal additions to global mean greenhouse forcing of the climate
system. aT0 is the computed temperature change at equilibrium (t-*—) for the
estimated decadal increases in trace gas abundances, with no climate feedbacks
Included. Multiply AT0 by the feedback factor f to get the equilibrium surface
temperature change including feedback effects. Most of the estimated trace gas
Increases are based on measurements, as discussed in the text. The 03 and
stratospheric H20 trends (dotted bars) are based principally on 1-D model calcu-
lations of Wuebbles et al. (1983); however, we have decreased the aT0 for 03 by
the factor 0.5 because much of the 63 chance would be confined to the hemispheric
or smaller scale.
(after Hansen et al., 1986 as in Fig. 7)
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Paper 3
ATtq(2*C02)
3 6
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55
1850-1980 C02 Warming
F1g.l2. Ocean surface *arm1ng (A!) and the equilibrium wanning UTeq) due to
added to the atmosphere 1n the period 1850-1980 fo- the 1-0 box diffusion
ocean model as a function of f or ATeq(2 *
(from Hansen et al., 1985, Science, 229, 857-859)
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Paper 3
u
o
Greenhouse Forcing
for two trace gas scenarios
Case A:
Current
Growth
Rates
doubled
C02 _± .
Case 6:
Reduced
Growth
Ramanathan eta!.(1985)
I960 1980 2000 2020 2040 2060 2080 2100
Date
fcj3(after Hansen et al., 1986, as in Fig. 7)
-------
Paper 3
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Fig.iH . Modeled and observed global mean surface air temperatures. The model
climate is driven by Case A greenhouse gases and stratospheric aerosols as
described in the text. The zero point for the model temperature is the mean for
that month from the last 10 years of a 35 year control run with fixed January
1959 greenhouse gases and the mean 1880-1980 stratospheric aerosol optical
depth. The observational data will be fully described elsewhere; the zero point
for observations is the mean for that month from the period 1958-1983. Five
year running means are 61 month averages for the period from 30 months before to
30 months after the indicated month.
(after Hansen et al., 1986, as in Fig. 7)
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Paper 3
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Paper 4
Depletion of Stratospheric Ozone
by
Richard Stolarski
NASA/Goddard Space Flight Center
and
Donald Wuebbles
Lawrence Livermore National Laboratory
This abstract was prepared by Workshop Chairman Harvey Jeffries from a taped recording of the
workshop presentation by Richard Stolarski and Donald Wuebbles. The following paper contains
information presented at the workshop and has been submitted to Nature for publication.
Nimbus 7 SBUV/TOMS Measurements of the Springtime
Antarctic Ozone Hole
by
R.S. Stolarski
IA.J. Krueger
M.R. Schoeberl
R.D. McPeters
IP.A. Newman
J.C Alpert
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Paper 4
Depletion of Stratospheric Ozone
Richard Stolarski and Donald Wuebbles
Abstracted by H. Jeffries
from Taped Meeting Presentation
Richard Stolarski described the fundamental science behind the stratospheric mod-
els for ozone (O3). Donald Wuebbles presented time-dependent predictions of ozone
as a function of altitude from his model. The following text was abstracted from a
tape recording of their presentations. A paper describing the springtime Antarctic
ozone depletion by Stolarski and co-workers follows this abstract.
Ozone Is Both Formed And Lost In The Stratosphere
Ozone is formed by the interaction of UV-radiation from the sun and oxygen (Oj) in
the earth's atmosphere. Ozone is also destroyed by UV-radiation, as well, but this
produces atomic oxygen that usually re-forms 0$; this cycle occurs many times.
Sometimes, the atomic oxygen reacts with Os to make two O2, thus ending a long
chain process. The absorption of UV, and the chemical transformations that follow,
result in an increase in stratospheric temperature. It also limits the amount of
UV-radiation that reaches the earth's surface.
The amount of ozone in the atmosphere is most conveniently measured as the
"total column" of ozone in units called Dobson Units (DU). Ozone, however, has
tropospheric sources as well as the stratospheric source, and thus its vertical con-
centration profile varies significantly. The peak Os concentration is usually in the
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Paper 4
Ozone Cycle Can Be Modified By "Catalyst-like" Compounds
stratosphere at 20-30 km. Likewise, total column ozone varies greatly over the
surface of the earth, much like weather patterns do. Values are usually between
250-500 DU.
Ozone Cycle Can Be Modified By "Catalyst-like" Compounds
Some chemical compounds have a potential to greatly shorten the cyclic chain that
makes Os in the stratosphere. The ones with the greatest effect are those that are
regenerated in the process, and therefore act much like a catalyst to accelerate the
loss of 03. These compounds result in ozone depletion in the upper stratosphere.
That is, the amount of Os that would normally be present is decreased. This lower
amount of Os absorbs less UV-radiation and thus the surface UV-radiation levels can
be elevated. In addition, less heating of the upper stratosphere may occur.
Source Of These Compounds Is The Troposphere
All the chemical compounds in the stratosphere come from the troposphere. The
compounds must have a long lifetime in the troposphere, that is, they cannot be
soluble, must not absorb visible light, and must not react fast with HO . These
"un-reactive" compounds can survive long enough to be transported into the strato-
sphere where they do encounter sufficiently energetic UV-radiation that their chem-
ical bonds are broken and they can then participate in chemistry. A major class
of such compounds are the chlorofluorocarbons (CFCs) or Freons, the most common
being F12 and Fll (CCI2F2 and CCI3F).
Complex Interactions Require Models
The dynamic processes and the chemistry are so complex and interactive that math-
ematical simulation models are the only tools available to understand the processes.
For example, Os concentration determines how much UV-radiation radiation is avail-
able; the available UV-radiation radiation determines how rapidly the catalytic com-
pounds are decomposed, which determines how much Os is present. Furthermore,
reactions and UV-radiation absorption give rise to heat; the heat results in winds that
transport material that influences the concentrations of the reactants; in addition,
temperature feeds back on the chemical reaction rates that produces the material
that is absorbing the UV-radiation to cause the heating, and so on. Often the models
tend to concentrate on one aspect of the problem using simple descriptions of the
other aspects. For example, one dimensional models tend to have complex chemistry
and no horizontal transport. Still, these models predict the average concentrations
in the hemisphere fairly well. More complex and costly two dimensional models
also predict concentrations as a function of latitude as well. These models have to
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Paper 4
The Depletion Process Is Occurring Now
make assumptions about how transport occurs, and different assumptions lead to
somewhat different predictions of the temporal and spatial distributions of the 0$.
Some Processes In The Models Result In Non-linear Behavior
Because of the relative competition among various species in the models, there
are perturbation scenarios in which the effect of some increasing linear change of
inputs results in a very non-linear response. For example, when the total chloride
is approximately equal to the total NOX, there is a a break in the rate of Os change.
Also, the predicted effects are very different at different altitudes, usually resulting
in a decrease in Os in the upper stratosphere and an increase in Os in the upper
troposphere and lower stratosphere. These altitude differences often offset each
other so that the total column O3 is only changed a small amount.
Model Predictions
Model calculations have been made from preindustrial times to 2050. These models
predicted that the total column Os increased during the 1970s. This, however,
was the result of the cancellation of substantial, but opposing, changes in Os with
altitude. A maximum decrease of 4.4% was predicted at 40 km, largely due to CFC
emissions (it was noted that increasing COj emissions reduced the CFC impact!),
while an increase of 1% was predicted at 30 km, as well as. an increase of 6.7%
predicted at 8-9 km due to aircraft and increased CH4 emissions. The extent to
which the model predictions are in agreement with the meager observational data
during this time will be described in a later section.
In future scenarios, most models predict a small decrease or increase in total
column Os, mainly due to increasing CH4 in the troposphere. The vertical distribu-
tions of Os, however, are dramatically modified. For example, one model predicts
up to a 36% Os increase below 26 km and a 22% Os decrease above 26 km.
The two dimensional models with transport predict a distribution of the altitude
effect with latitude in which the low latitude results are similar to those quoted
above for the low and mid-latitudes, but the predictions for the poles showed a
decrease at all altitudes. The total column changes predicted by these models, for
an increase of 5 ppb chloride, were about 4% O3 depletion at the equator and 18%
O3 depletion near the poles.
The Depletion Process Is Occurring Now
British Antarctic Survey Station at Halley
The British have been measuring total column Os at Halley, Antarctica (76°S) since
3
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Paper 4
Nimbu8-7 Satellite Data
the International Geophysical Year in 1956. In 1957 the values were 310-320 DU
in the springtime. Now they are 40% lower in October (Antarctic spring). In the
winter at Halley, there is no sunlight; in the spring, the sun returns. It is speculated
that during the dark, very cold winter, CFCs accumulate, and when the sun does
reach the upper stratosphere for the first time in the spring, the CFCs undergo
rapid reaction and destroy the ozone. As the CFCs are consumed, the ozone levels
gradually increase to higher values, but by autumn the level is still 5-10% lower
than it was 10 years ago.
Nimbus-7 Satellite Data
NASA has made a color movie from the Nimbus-7 satellite's TOMS instrument that
can measure total 03. The movie, which was shown at the workshop, shows the
pole view of Os concentrations on each day in October for the years 1980 to 1985.
(A paper describing these data follows this abstract). The images are dramatic:
in the beginning of each year, the Os is reasonably uniform and then the depletion
process starts; it appears as if a large hole is being eaten in the atmosphere and
then it begins to recover near the end of the month. Each year, however, the area
of Os depletion increases and the depth of the central depletion is deeper. In 1984,
the value at the pole was down to about 190 DU, and in 1985 it was down to about
180 DU.
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NIMBUS 7 SBUV/TOMS MEASUREMENTS OF THE
- SPRINGTIME ANTARCTIC OZONE HOLE
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R. S. Stolarski
I A. J. Krueger
M. R. Schoeberl
R. D. McPeters
IP. A. Newman
J. C. Alpert*
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NASA/Goddard Space Flight Center
•Laboratory for Atmospheres
Greenbelt, MD 20771
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_ Submitted to Nature
• April 8, 1986
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*Presently at NOAA/NMC Camp Springs, MD
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NIMBUS 7 SBUV/TOMS MEASUREMENTS OF THE
SPRINGTIME ANTARCTIC OZONE HOLE
Abstract
• Paper 4
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Satellite measurements confirm the recent decline of total ozone in
• successive Octobers reported over Halley Bay Station, Antarctica. The
• decrease occurs during September as the the Sun rises, reaching a minimum in
mid-October. Six years of October monthly means show a 30% decrease in the
• ozone minimum and a 10% decrease in the surrounding ozone maximum. These are
shown to be related.
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I. Introduction
Fartnan et a!.*, in a series of measurements which date back to 1956,
report a rapid decrease in the total column amount of ozone over the Halley
Bay station in Antarctica at 76°S and 27°W. The decrease was most pronounced
in October, early spring in the Southern Hemisphere. They attributed the
decrease to the increase in stratospheric chlorine due to chlorofluorocarbon
release and proposed that the unique conditions of extreme cold and low
sunlight in the Antarctic winter and spring maximized the effect. We report
measurements from the Solar Backscatter Ultraviolet (SBUV) instrument and the
Total Ozone Mapping Spectrometer (TOMS) onboard the Nimbus 7 satellite. These
provide global measurements of ozone from November, 1978 to the present time.
The SBUV is a nadir-viewing instrument which obtains total ozone from
measurements of the backscattered solar ultraviolet radiation in the
wavelength range 310 nm to 340 nm.^»3 Measurements in the 250 nm to 310 nm
wavelength range by the SBUV instrument provide information on the
distribution of ozone with altitude. The TOMS instrument is designed to
measure the spatial distribution of total ozone by scanning across the track
of the satellite to obtain data between successive satellite orbital tracks.
Nimbus 7 is a Sun-synchronous polar-orbiting satellite which passes any given
point on the dayside near local noon.
II. Observations
a. Spatial morphology of total ozone in October
One of the major advantages of the TOMS instrument is its ability to map
total ozone over the entire globe on a daily basis. Figure 1 (see also cover
picture) shows a sequence of daily south polar projections of total ozone for
October, 1984. The Halley Bay Station is indicated by a * on the figure and
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Paper 4
the Greenwich meridian is to the top. The extreme low total ozone over Halley
• Bay is observed to be part of a larger elliptically shaped minimum region
extending out to about 60-70°S. The minimum region, which tends to rotate
| about the pole with an irregular period of about 7-10 days, is bounded by a
« steep gradient where total ozone increases to values in excess of 300 milli-
atm-cm (Dobson Units or DU). At 50-60°S total ozone goes through a maximum
• which exhibits larger variability due to travelling planetary waves. The
existence of a polar minimum and a mid-latitude maximum in total ozone is a
| part of the normal, long-term climatology of the Southern Hemisphere. The
— recent year-to-year changes in these features are the focus of this paper.
™ The twelve panels in Figure 1 show twelve consecutive days from October
• 11, 1984 to October 22, 1984. This is the time period for which the lowest
values are generally recorded. Each panel is centered about the South Pole
I and gives data out to 45° latitude. On October 11, Figure 1 shows that the
minimum in total ozone is relatively symmetrical about the pole and the
• maximum in total ozone is located in the lower right between about 90°E and
• 180°E. On succeeding days the total ozone maximum region rotates clockwise,
while the minimum region elbngates and begins to corotate with the maximum.
• On October 16 and 17 the maximum region has reached the lower left corner,
between 180°E and 270°E where it seems to dissipate and subsequently reappear
| in the upper right corner. From there it continues to move around the pole
_ but does not pass over Halley Bay. By October 20 the ozone distribution has
™ returned approximately to the original situation on October 11, giving a
• rotation period at this time of 9 days. The next 2 days are near repeats of
October 12 and 13.
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Total ozone is proportional to the pressure weighted integral of the
ozone mixing ratio, and fluctuations in the amount of total ozone may indicate
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Paper 4
a relative lifting of the mixing ratio distribution in altitude, a chemical
loss in the lower stratosphere, advection of ozone into a~ region from other
locations or all of the above. Figure 2a shows the temperature distribution
for October 3, 1982 at a pressure of 50 mb, a level centered in the lower
stratosphere. This map can be compared to the total ozone map for the same
day in Figure 2b which shows a high correlation of low temperatures with low
total ozone and high temperatures with high total ozone. Superposed on each
panel of Figure 2 are heavy lines with arrows indicating the geostrophic wind
streamlines and wind direction at the 50 mbar surface. The circulation within
the ozone minimum region is closed, thus confining air parcels to this cold
region, the polar vortex. At lower latitudes parcel trajectories pass from
cold, low total ozone regions through the warm, high total ozone regions on
the other side of the pole. Along these trajectories total ozone varies by as
much as 150 OU.
An excellent correlation between total ozone and 50 mb temperatures
exists on all other days we have examined. This correlation results from the
adiabatic temperature changes due to vertical motions which simultaneously
produce total ozone changes as the air is advected around the pole. At the
point where the ozone column is lifted the highest both total ozone and 50 mb
temperatures are minimum.
b. Year-to-year trend in total ozone for October
Evidence that the long term total ozone decrease observed at Halley Bay
is not unique to Halley Bay is shown in Table 1 where we give the zonal mean,
local minimum, and local maximum total ozone values for the month of October
in each year for the 70°-80° latitude band for 1970-72 from BUV and 1979-34
from SBUV. Data from the Nimbus 4 BUV instrument, the predecessor to SBUV,
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was fairly complete for the 1970-1972 period; in later years coverage of the
I Antarctic by BUV was reduced. The BUV ozone data have been reprocessed with
exactly the same algorithm as SBUV and with compatible instrument
• characterization functions, so it is reasonable to compare the BUV total ozone
m with the SBUV total ozone. Antarctic total ozone observed in 1979 appears
comparable to that observed in the early 1970's; significant total ozone
I decreases occurred only after 1979. Thus, the long-term behavior of total
ozone reported for Halley Bay appears to reflect the general behavior of total
| ozone for the Antarctic.
_ The nature of the decrease is shown more clearly in Figure 3 which gives
™ October monthly mean TOMS total ozone maps for each of the six years from 1979
• through 1984 for the Southern Hemisphere. The monthly mean values in the
minimum region are seen to decrease from about 250 OU in 1979 to about 180 DU
I in 1983 and 1984. The three days of October 1985 TOMS total ozone data which
we have examined indicate values as low as or slightly lower than in 1984.
• Table 2 indicates the specific values for the October monthly means over three
• stations (Halley Bay, Syowa and Amundsen-Scott) as well as the minimum, and
maximum values of the monthly mean. The total ozone values for Halley Bay
• agree closely with those reported by Farman et al. We have examined 4 years
(1979-1982) of 50 mbar temperature data. The interannual variations in
| temperature were similar to the total ozone variations, but no definitive
• trend could be seen in the temperature data.
Figure 3 also shows the October monthly mean total ozone maximum located
• at about 60°S latitude. The phase of the maximum shifts from year to year;
ranging from about 90° E to 180°E. In 1979 the maximum monthly mean total
I ozone value exceeds 450 DU. By 1984 the maximum is barely over 400 OU, a
decrease of just over 10% in 6 years. Although six years is too short to
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definitively identify a two-year cycle, there does seem to be some modulation
of the decrease in both the maximum and minimum. A quasi-biennial oscillation
in total ozone has been previously observed but its magnitude was only about
6-8 DU.5'6
The year-to-year downward trend seen in the 50-60°S maximum in total
ozone is consistent with the decrease in the high latitude minimum region.
The air parcel trajectories shown in Figure 2 indicate that the parcels which
form the total ozone maximum have also passed through the periphery of the
cold region. The existence of maximum and minimum regions are the result of
adiabatic descent and ascent of the column as a whole. Therefore, if some
mechanism is chemically removing ozone in the cold region of the parcel orbit,
a loss should also appear in the maximum in total ozone as the parcel descends
and warms.
c. The annual cycle in total ozone
The data given by Farman et al.* for Halley Bay showed total ozone
amounts coming out of the polar night beginning on October 1, 1984 which were
a few tens of percent lower than those entering the polar night. Sunrise
occurs in late August over the station, but the data are limited by the solar
zenith angle of the observations. The ozone algorithms for both TOMS and SBUV
have been carefully scrutinized for their behavior at high solar zenith angles-
and found to return accurate results for zenith angles up to 85°.^ We thus
have observations back through the month of September for the latitude of
Halley Bay (76°S). The results show values of total ozone coming out of polar
night very close to those observed entering the polar night. This result is
also in agreement with the observations of total ozone taken at Syowa station
(69°S) for 1982.8 However, there is some indication from Lunar Dobson and
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ozonesonde measurements at Syowa that total ozone increases slowly until
I winter solstice then decreases again until sunrise with a more rapid decrease
thereafter.
| Throughout the month of September and the first week in October, a rapid
_ decline is observed in total ozone by both SBUV and TOMS until the previously
• mentioned low values are obtained. This is shown in Figure 4 with data from
• the SBUV instrument for the period late August 1983 through April 1984. The
data points are the satellite data which are centered within ±2° latitude and
• ±15" longitude of Halley Bay. The solid lines are the maximum and minimum of
values reported at all longitudes within the latitude band 74°S to 78°S.
• Throughout October and November the data over Halley Bay are consistently near
• the minimum values for all longitudes for this and other years as well. The
decline in the minimum value of ozone column extends from late August through
I early October at a rate of approximately 0.6%/day. At longitudes on the other
side of the pole from Halley Bay the total ozone amount is variable and often
| very large.
• Near the end of November the low values have completely disappeared and
the minimum curve goes through a maximum. The jump in total ozone is
I coincident with the final warming in the Southern Hemisphere and marks the
switch from winter to summer circulation. During the final warming process
Jj large amounts of ozone are advected into the polar regions from lower
latitudes. A similar process occurs in the Northern Hemisphere but usually
• only three months after the winter solstice rather than the five months seen
• here. Throughout the Antarctic summer the ozone column decreases and the
Halley Bay values oscillate between the maximum and minimum curves as lower
• stratospheric travelling waves pass over the station.
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Paper 4
III. Conclusions and Discussion
The satellite data from the Nimbus 7 TOMS and SBUV instruments
significantly extend our view of the growing ozone minimum over the South
Polar region. The decrease observed by Farman et al.* over Halley Bay has
been confirmed and shown to be part of a general decrease over the Antarctic
region. Data for 1985 indicate a continuation of the ozone minimum. Our data
places significant constraints on possible mechanisms for explaining the
decrease. The deep minimum, or hole, follows the polar vortex, and its
position is well correlated with the temperature minimum in the lower
stratosphere. There also appears to be a smaller but significant
decrease (-10%) in the total ozone maximum surrounding the polar region over
the 6 years studied. The decrease in the total ozone maximum is related to
the decrease in the total ozone minimum in that the air parcels in the maximum
region have passed through the periphery of the low temperature region, which
is associated with the total ozone minimum.
An important constraint placed on theoretical models by this data is that
the decrease in total ozone near the pole appears to largely take place in
September during twilight, not in the polar night. The maximum rate of
decrease in total ozone occurs after most of the polar region is sunlit and is
about 0.6% per day extended over 40-50 days in 1983.
Any explanation of the total ozone change must be consistent with the
year-to-year'changes both in the polar vortex as well as consistent with the
rate of decrease through September. Various ideas have been put forward
involving combinations of chlorine chemistry, heterogeneous chemistry taking
place in polar stratosphere clouds, bromine chemistry and dynamical lifting of
the polar stratosphere.1»10,11,12
We estimate that, in order for chlorine chemistry at 1983 concentrations
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to cause the 0.6%/day decline in September, virtually all of the chlorine must
g be in its active state, i.e. Cz and CzO, with little or no interference from
_ NOY. Therefore any proposed chemical mechanism must be able to remove most of
I
• the chlorine from both the HCi and QONCL reservoirs and to tie up NOX,
• preferably as HNO^. Such a mechanism could involve the cold temperatures
and/or polar stratospheric clouds that form within the polar vortex. ^
• Any conclusions concerning the implications of the observed Antarctic
decreases in total ozone on predictions of the effects of chlorine from
8 fluorocarbons must await a definitive mechanism and continued observations to
• verify the persistence of the phenomenon. Only then will we be able to
clearly evaluate the relative roles of chemistry, radiation and dynamics in
• contributing to the observed decrease.
| Acknowledgment
_ We thank the Nimbus 7 Ozone Processing Team (A. Fleig, Chairman) for making
™ available TOMS data from October 1983 and 1984, and the Real-Time TOMS Project
• for data for a few days in October of 1985 before regularly scheduled
processing. Reggie Galimore was responsible for the image processing which
I made the data readily available for visual examination. We thank S. Solomon,
S. Wofsy and N. D. Sze for discussing and making available preprints of their
• papers and S. Chandra for useful discussions. We. thank Lori Winter and
• Roberta Duffy for their excellent typing of the many versions of this
manuscript.
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References
1. Far-man, J. C., B. G. Gardiner and J. 0. Shanklin, Nature, 35, 207-210,
1985.
2. Heath, D. F., A. J. Krueger, H. A. Roeder and B. 0. Henderson, Opt. Eng.,
14, 323-330, (1975).
3. Klenk, K. F., P. K. Bhartia, A. J. Fleig, V. G. Kaveeshwar, R. 0.
McPeters and P. M. Smith, J. Appl. Meteor., 21, 1672-1684, (1982).
4. Sticksel, P. R., Mon. Weather Rev., 98, 787-788 (1970).
5. Hasebe, F., in Dynamics of the Middle Atmosphere, J. R. Holton and T.
Matsuno, eds., Terra Scientific Publishing Co., Tokyo Japan, pp. 445-464,
(1984).
6. Hilsenrath, E. and B. M. Schlesinger, J. Geophys. Res., 86, 12087-12096,
(1981).
7. Bhartia, P. K., personal communication (1985).
8. Chubachi, S.t in Atmospheric Ozone, C. S. Zerefos and A. Ghazi, eds., D.
Reidel Publishing Co., Dordrecht, pp. 285-299. (1984).
9. Rood, R. B., PAGEOPH, 121, 1049-1064, (1983).
10. Solomon, S. and R. R. Garcia, Submitted to Nature, 1986.
11. McElroy, M. B., R. J. Salawitch, S. C. Wofsy and J. A. Logan, Submitted
to Nature, 1986.
12. Tung, K. K., M. K. W. Ko, J. M. Rodriguez, and N. 0. Sze, Submitted to
Nature, March 1986.
13. Steele, H. M., P. Hamill, M. P. McCormick and T. J. Swissler, J. Atmos.
Sci., 40, 2055-2067 (1983.
10
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Paper 4
Table 1. Zonal mean, local minimum, and local maximum total ozone values in
DU for the month of October each year for the 70-80°S latitude zone
from Nimbus 4 BUV (1970-1972) and from Nimbus 7 SBUV (1979-1984).
Year Zonal Mean Local Minimum Local Maximum
1970 306 240 484
1971 334 249 482
1972 337 237 539
1979 333 235 515
1980 270 212 467
1981 266 206 422
1982 283 186 494
1983 245 166 479
1984 240 162 446
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Table 2. October mean ozone column as determined by TOMS from 1979 through
1984 over 3 Antarctic Stations plus the minimum and maximum values
of the monthly mean (all in Dobson Units or mi Hi-atmosphere
centimeters). Also given are the one-sigma variances of the daily
values from the monthly mean for the specific locations.
TOMS TOMS
Halley Bay Syowa South Pole Minimum Maximum
76°S 27°W 69°S 39°E 90°S
October
1979 273 ± 19 367 ± 47 266 ± 25 259 458
1980 232 ± 11 276 ± 22 218 ± 9 215 433
1981 244 ± 12 312 ± 30 223 t 9 219 449
1982 221 ± 12 240 ± 49 220 ± 22 205 432
1983 199 ± 13 239 ± 32 182 ± 8 178 414
1984 190 ±8 245 ± 24 187 ± 14 181 404
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Paper 4
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• Paper 5
• Relationships among CO, NOx, CH4, and HO*
by
• Anne Thompson
m Applied Research Corporation
I
This presentation was based upon the following paper, which has been submitted to the Journal of
M Geophysical Reseach for publication.
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Possible Perturbations to Atmospheric CO, ChU, and OH
1 by
fAnne M. Thompson
Ralph J. Cicerone
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• Possible Perturbations to Atmospheric CO, CH^, and OH
I
jm Anne M. Thompson
Applied Research Corporation
V Landover, Maryland
and
National Center for Atmospheric Research
i*j and
^ Ralph J. Cicerone
tt National Center for Atmospheric Research
Boulder, Colorado
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• 23 May 1986
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*The National Center for Atmospheric Research is sponsored by the National
• Science Foundation.
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Paper 5
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Paper 5
ABSTRACT
A photochemical model is used to predict temporal trends in OH, CH^ and
CO over the next fifty years and to assess possible past changes in these
trace gases from 1860 to 1985. Various scenarios of perturbed CH^ and CO
levels based on recently reported CH^ and CO data are simulated at several
levels of background NOV. With low NO... conditions (NO + N05=25 pptv) typical
A A £
of the nonpolluted troposphere we compute a monotonic loss of tropospheric OH
from 1860 to 2035 with the magnitude of the decrease dependent on CO and CH^
increases during the period. If current trends continue (ground level mixing
ratios [mole fractions] of CH^ rising ""\% yr"1), by 2035 northern latitude CH^
will increase from 1.6 to 2.9 ppmv and CO will double or triple its present
day level (to ~250-350 ppbv in the nonpolluted northern hemisphere). The
column abundance of OH in the background troposphere will decrease 25-35%,
depending on the magnitude of CH^ and CO increases and assuming that global
temperature increases do not raise water vapor levels during that time.
Calculations with increased H20 show a 17-30^ decrease in OH.
Under higher NOV conditions (1 ppbv) OH shows a decline from 1860 to
A
2035, but only half as much as with low N0_ conditions. In the case of NOV in
A A
a transitional zone (i.e. NOX increasing from 20 pptv in 1860 to 0.5 ppbv in
2035) CO and CH^ increases accompany a rise in OH followed by a small
decline. The turning point in OH depends on the rate of change in NOX and
GO- Recently observed upward trends in CO and CH^ are probably due to
increasing emissions of both CHjj and CO.
We always compute a temporal increase in tropospheric O? when CH^ and CO
increase. Typical 1860 values for surface Oo are 25 ppbv, compared to 30 ppbv
(NOX = 25 pptv) and 40 ppbv (NOX = 1 ppbv) in 1985. In a transitional NOX
zone we find surface Oo increasing from 10 ppbv in 1860 to 27 ppbv in 1985.
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1. INTRODUCTION
m The interdependence of atmospheric CO, CH^, and OH is well known [Levy,
1972; Crutzen, 1973; Wofsy,1976]. The OH radical is centrally important in
• the photochemistry of the troposphere because it oxidizes many nitrogen-,
carbon-, and sulfur-containing species and some halogenated hydrocarbons. The
| oxidation of methane, for example, starts a chain of processes, eventually
forming CO:
—
M
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C13 -i_ AU \ f*l] j_ U A
wil|j + wfl — / V^flo T flow
CH3 * °2 * M "> CH3°2 * M
CHgO + 02 -> H2CO + H02
fH2 + CO
H2CO + hv ->V
( HCO + H
HCO + 02 -> CO + H02
CO itself reacts with OH; a product is C02:
CO * OH -> C02 •(• H.
Methane and CO together are the largest consumers of tropospheric OH.
M
Thus, an increase in the background level of either of these species can
• reduce OH and the oxidizing power of the entire troposphere. This has
important implications for the environment, e.g., reduced rates of formation
| of atmospheric acids, at least in remote regions. The rate at which natural
— and anthropogenic trace species are oxidized in the boundary layer before
' passing into the free troposphere and the stratosphere would also be reduced.
ti| Not only are CHjj and CO the dominant consumers of tropospheric OH, OH is
the major sink for CH^ and CO. Thus, a sort of feedback can be envisioned:
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1
more CO -> less OH; less OH -> more CH^; more CH^ -> less OH, and so on. |
Sustained perturbations to any one of the three species CO, CH^, OH influence
background levels of the other two, possibly with an amplified effect. J
Relationships among CHjj, CO and OH and the effects of perturbed CH^ and |
CO have been the subject of previous studies [Chameides et al., 1977; Sze, "
1977; Hameed et al., 1979; Levine et al, 1985; Crutzen, 1986]. Sze [1977] \
studied the effects of increased anthropogenic CO production on ground level
OH and CH^. Chameides et al. [1977] described changes in total tropospheric I
abundances of OH and CH^. Hameed et al. [1979] pointed out that both j
magnitude and direction of calculated changes are highly sensitive to ambient *
NOX. The current investigation is prompted by newly published evidence for a |
temporal increase in tropospheric Cfy [Ehhalt et al., 1983; Rasmussen and
Khalil, 1981; Rinsland et al, 1985; Stauffer et al, 1985] and possibly for an I
increase in CO [Khalil and Rasmussen, 1984; Rinsland and Levine, 1985]. It is
similar to the modeling study of Levine et al [1985] in prescribing specific
CHjj and CO changes but it covers a longer time span and wider NOX and On
variations.
Section 2 describes the photochemical model including choice of model
inputs and boundary conditions for three cases: low NOX, midlatitude; high
NOX, midlatitude; low NOX, low latitude. Basic features of CO and CH^
perturbation calculations are also presented in Section 2. In Section 3 the
model is used to predict CH^, CO, and OH over the next fifty years and to
assess possible CH^-CO-OH perturbations from 1860 to 1985. Discussion
(Section 4) follows. We attempt to discern whether increasing global sources
of CO or increasing sources of CHj, or both are responsible for the recent
apparent increases of these gases.
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2. CH4-CO-OH COUPLING
A. Photochemical Model
The coupled photochemical transport model used in these calculations is
that of Thompson and Cicerone [1982]. The model solves
a set of continuity
equations for the time rate of change of species i:
3 > K(z,t)N(z) *xi(z,t)
32 3Z
where z = altitude; K(z,t) = eddy
+ Pj^z.t) - Li(z,t) =
diffusion coefficient
3ci(z,t) (1)
3t
(cm2 s"1); N(z) =
molecular density (cm~3) of background air; Xj/z»t) = mixing ratio or mole
fraction of species i; c^z.t) is
production, loss rates (cm~3 3~1)
density (cm~3); P^(z,t
for chemical reaction
model domain spans 0-15 km with 24 grid points; vertical
simulated by eddy diffusion coefficients as described by
[1982]. Fixed profiles for molecular density, H2, H20,
1
1
1
-l^
1
1
1
1
given in Table 1 .
), Li(z,t) =
of species i. The
transport is
Thompson and Cicerone
and temperature are
The basic model [Thompson and Cicerone, 1982] solves (1) for 17 radical
and gaseous species: Oo, 0(^p)f NO, N02, NO,, NgO^, HNO^
, HN04, H, OH, H02,
H202, CHj, CH^O, CHj02, CH^OOH, and H2CO. In the present study the number of
continuity equations is increased
to 25 with the addition of CO, CH4, and six
nonmethane hydrocarbon species: C2Hg, C^^O^ C2HcOOH, CH^CHO, CH^CO,, and
CHoCOqNOg (peroxyacetylnitrate) .
photochemical equilibrium: 0( D),
reactions and three photolyses to
One reason for the NMHC additions
Three species are calculated assuming
CHO, C2H50. The NMHC
species add eight
the model photochemical scheme (Table 2).
is to make background
3
hydrocarbon levels
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more realistic than those obtained if methane is the only hydrocarbon radical
precursor. For example, the oxidation of ethane, £fl§, produces two moder-
ately long-lived hydrocarbons, CH^CHO and CgHgOOH. The oxidation of CH^CHO
leads to the formation of PAN (peroxyacetylnitrate). PAN may be an important
reservoir of odd nitrogen in the troposphere [Crutzen, 1979; Singh and Hanst,
1981; Aikin et al, 1982; Brewer et al, 1983; Kasting and Singh, 1986].
Photolysis rates used in (1) are calculated as described in Thompson
[1984] and free radical reactions [Thompson and Cicerone; 1982] appearing in
(1) employ rate constants taken from the NASA/JPL [1983] tabulation.
Species boundary conditions (Table 3) used to represent low NOX
conditions (both low and midlatitude) are similar to those used in Thompson
and Cicerone [1982]. Two basic low NOV models are designated LNLL for low
A
latitudes and LNML for midlatitudes. Lower boundary conditions for CO and Ctfy
are surface upfluxes prescribed- to give appropriate mixing ratios for these
species: 1.6 ppmv CH^, 120 ppbv CO (midlatitude); 85 ppbv CO (low latitude).
Ethane at the lower boundary is fixed at 1.5 ppbv, a typical value for the
background troposphere [Singh et al, 1979; Rudolph and Ehhalt, 1981]. A
transfer velocity upper boundary condition is assumed for CO, CH^, and ^2^6'
Boundary conditions for the high NO case (~1 ppbv NOX) are similar to
those for the low NOV model runs (Table 3) except that the high NOY model uses
A A
a surface NO upflux nearly 100 times greater than the flux used for low NOX
model runs. The high NO midlatitude model is denoted HNML. Corresponding 0^
is higher in the HNML model than in the LNML case: 41 ppbv Oo at the surface
compared to 30 ppbv. OH is also higher and CO and CH^ fluxes are adjusted to
maintain background surface mixing ratios at typical levels (120 ppbv CO, 1.6
ppmv CHjj). In the HNML model (Table 3) deposition velocities are taken to be
higher than in lower NO., models to reflect the fact that most higher NOV
A A
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environments are in continental areas where surface deposition is faster
[Lenschow et al., 1982]. than in the lowest NOX (marine) environments. In
mi
both low NOX and high NOX models we neglect lightning-produced NOX.
For each of the model types LNLL, LNML and HNML, the time dependent
equations (1) are integrated until ozone has converged to a time- in variant
vertical profile and all other species display periodic 24 hour behavior.
Diurnally averaged species concentrations and diurnal factors for reaction and
photolysis rates are calculated according to the procedure of Turco and
Whitten [1978]. These concentrations and diurnal factors are used as input
for a time- independent (steady-state) version of the model, which consists of
Eqs (1) with acat = 0.
B. Basic Model Results
Calculations to determine the sensitivity of CH^-CO-OH changes to
perturbed CO and CHjj emissions are carried out with a steady-state model using
inputs unchanged except for higher specified fluxes of CO (or CH^).
Perturbation calculations are made for each of the three models LNLL, LNML,
HNML. For CH^ perturbations CH^ fluxes are adjusted to give methane surface
mm mixing ratios 10-150% higher than present day values. For CO perturbations CO
fluxes are modified to give higher surface mixing ratios of CO.
I Figure 1 shows vertical profiles (0-15 km) of tropospheric OH (cm~^) with
no perturbations (solid lines) and with 50% and 100% CO and CH^ pertur-
j| bations. LNML results are illustrated in Figure 1a. Both quantitatively and
^ qualitatively OH responds differently to CO and CH^ variations. First, in the
• upper troposphere increasing CO suppresses OH whereas adding CHlt increases
£ OH. Second, in the mid and lower troposphere addition of CO and CH^
suppresses OH, but the response is greater for CO because the effective rate
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of OH removal by CO is shorter.
Figure 1b gives HNML results for OH response to perturbed CO and CH^.
With relatively high background NOX OH increases rather than decreases near
the ground with added CO and methane. This is because in the presence of high
NOX additional CO and C^ oxidation forms ozone through smog-type reactions.
Additional ozone when photolyzed replenishes OH:
03 + hv -> O^D) + 02
0(1D) + H20 -> 20H.
In an environment with higher NOX, or at least with a high N0x/hydrocarbon
ratio as in the present simulations, adding CO or CHjj appears to increase
oxidant levels. This could affect urban and nonurban atmospheres where NOV
A
levels are high. Furthermore, enhanced amounts of ozone might be transported
from urban to remote (low NOX) areas where it could increase the potential for
forming OH, perhaps offsetting some of the local OH depletion initiated by
elevated CO or CH^ levels (Vukovich et al, 1985).
The high N0_ OH behavior is only a surface phenomenon, however. Total
A
tropospheric OH (column-integrated) in all three models, LNML, LNLL, and HNML,
decreases in response to added CO and CH^. This can be seen in Figure 2 where
tropospheric OH is shown as a function of perturbed CHjj and CO. The effect of
high NOX in the boundary layer is to lessen total column loss.
The effects of perturbed CO and CHjj fluxes on CO and CH^ themselves are
shown'in Figure 3; only results from the LNML model are illustrated but
results with HNML and LNLL models are nearly identical. Effects of feedback
of CO on CH1j and vice versa are obvious. For both CO and CH^ the additional
flux required, A flux (as a fraction of the initial flux) is less than the
desired fractional mixing ratio increase (A mixing ratio) and the ratio of the
increments, i.e., A flux/ A mixing ratio, is not constant over the range of
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m perturbations studied. The nonlinearity in the flux/mixing ratio relationship
» is such that it takes only a 77% increase in the CO emission rate (with no
change in CH^ emissions) to double the CO surface mixing ratio. Methane
• doubles even more effectively than CO. With fixed CO influx it takes only a
65% increase above the initial CHn flux to double surface methane. Similar
I4
nonlinearities were noted by Chameides and Davis [1985].
M A consequence of the nonlinearity of the response of steady-state mixing
ratios to perturbed flux is an infinite number of paths to a given CO or CH^
• increase. For example, a 25% increase in the CO mixing ratio is produced as a
result of a 20% increase in CO emissions with no change in the methane flux
| (Figure 3a). The same CO increase can occur, with no increase in CO emis-
— sions, if methane emissions are increased by about 57% (Figure 3b). Clearly,
™ some combination of CO and CHh perturbations could also bring about a 25%
• increase in background CO. From a practical point of view this is very
important. Monitoring concentrations of a trace gas that is changing without
• knowing the source(s) of the change makes meaningful long-term predictions
impossible. Should a trend in anthropogenic CHn or CO or or of some other gas
• that is related to changes in OH be deemed undesirable, it would be difficult
• without knowing cause and effect to devise a control strategy.
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3. TRENDS IN ATMOSPHERIC CO, CH^ AND OH: 1860-2035
A. Ofy, CO, OH Scenarios
We have performed model calculations to predict CH^, CO and OH changes
over the next fifty years and to look backward in time, assessing possible
variations in these species since i860 (chosen as the start of the heavily
industrial era). As much as possible observations are used to prescribe model
scenarios, although we are limited by sparse data, uneven geographical
coverage and a short historical record; i.e. prior to 1950 there are few data
for any trace gas.
Perturbations to background CHh and CO have been measured or deduced by a
number of investigators [Graedel and McRae, 1980; Rasmussen and Khalil, 1981;
Blake et al, 1982; Khalil and Rasmussen, 1984; Rinsland et al, 1985], but the
magnitude and duration of trends is far from certain. This makes choice of
model input for predicting further changes problematic. Extrapolating back-
ward to 1860 is difficult because source budgets are not known accurately and
emissions trends must be estimated over the past 125 years. The situation is
further complicated by the sensitivity of CH^ and CO perturbations to NOX for
which no historical data are available and for which the present day record is
spotty. Our approach to model runs is to parameterize CHjj and CO over a range
of values in keeping with recently reported data and to combine these with
several levels of NOX. Choices for input are reviewed below.
QH||Z The weight of evidence favors secular increases in CHh of about 1% per
year, at least over the past three decades or so [Ehhalt et al, 1983; Blake et
al, 1982; Rasmussen and Khalil, 1984; Rinsland et al, 1985], and the long-term
record of CHjj trapped in polar ice cores indicates that CHjj has been
increasing since 1800 [Rasmussen and Khalil, 1984; Stauffer et al, 1985] or
8
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Paper 5
• even earlier [Craig and Chou, 1982].
• For model runs from i860 to 2035 we have adopted two approaches. The
conservative choice assumes no temporal change in CHjj sources and assigns a
• constant CJfy flux at all times. In this case temporal increases in CH^ occur
only in response to perturbed OH caused by altered levels of some other trace
• gas(es), i.e. in our model, by CO. The second approach specifies the CH^
M mixing ratio at each year of model calculation, following ice core data from
* 1860 to 1985 [Khalil and Rasmussen, 1985; Stauffer et al, 1985] and assuming a
• 1% yr"^ increase beyond 1.60 ppmv for years after 1985.
CO; The choice of input for CO is complicated because there are large
| geographical and seasonal variations owing to the relatively short lifetime of
_ CO, a few months in midlatitudes. Also, trends in CO are ambiguous. Khalil
™ and Rasmussen [1984] extracted a 6% yr~' rate of increase from more than
• 60,000 measurements of CO taken in Oregon over a 3-1/2 year period (1979-
1983), but this is probably too high [Seller, private communication, 1984].
• Rinsland and Levine [1985] deduce a 71/6 increase from 1951 to 1976 from spec-
troscopic data at one European site. Southern hemisphere CO concentrations
• may have risen a total of 5-10% between 1971 and 1981 [Seller et al, 1984].
• Three sources of CO are specified in the model and uncertainties in CO
budgets and trends are treated by parameterizing relative amounts of natural
• and anthropogenic sources. Model runs for years other than 1985 assume that
anthropogenic inputs scale with population or fossil fuel usage. For year t
• at altitude z the total source, S^ ^ •, Q0(z,t) consists of:
Stotal,CO{z'fc) = QcO(z'fc) * fluxco(t) * SNMHC(z'fc)
I
where QCQ is in-situ photochemical formation from CH^ and C2Hg oxidation;
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, the model lower boundary condition, signifies direct boundary layer
sources. 3^^ is an explicitly specified term representing in-situ airborne
CO sources besides CHji and C^Hg oxidation, i.e., photooxidation of nonmethane
hydrocarbons besides CgHg. SHIQIC is added to the CO continuity equation with
a functional form that follows the product of OH and the altitude dependence
of a typical OH and alkane reaction.
For model runs at midlatitude conditions CO is always 120 ppbv at 0 km
for 1985 and relative amounts of sjjMHC^1^5^ and fluxco^1985^ are Para~
meterized as shown in Table 4. Type 1-CO (Models 1 and 3) is based on
stotal,CO(1985) consisting of 35% fluxco and Type 2-CO (Models 2 and 4) is
based on 65% of Stotal'CO( 1985) as fluxco. Model runs at years other than
1985 assume that natural sources contributing to S^^ and flux^Q are fixed in
time and anthropogenic ones scale with population or fossil fuel usage. The
in-situ source is given by:
SNMHC(2,t) = SNMHC(2,1985) [fjMHC.M * rff(t) fNMHC,A( 1985) 1 (4)
where fji^jjc N (O'0^) and ^NMHC ft(1985)=0.l8 are fractions of SNMHC due to
oxidation of natural and anthropogenic NMHC [Logan et al, 1981]. r^(t) is
the ratio of fossil fuel usage in year t relative to 1985. We assume that
incremental CO emissions follow C02 and use Reeling's (1973) values for C02
from fossil fuel burning to obtain rff(t) from i860 to 1965. After 1965 a
2.5% annual increase in fossil-derived C02 is used [NRC, 1983] implying a 30-
35 year doubling time for CO from this source. Where combustion CO is mainly
from automobiles and is regulated, CO may rise more slowly [Kavanaugh, 1986].
The time dependence of fluxCg(t) is:
fluxco(t) = fluxco(1985) [fflux>N + rffU) fAff(1985) + rP°P(t)fAnf(1985)]
10
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with rp°P(t) the ratio of population in year t relative to 1985. f's are
based on the Logan et al [1981] budget for Northern Hemisphere CO sources;
*"flux M = °'^3 is the natural fraction of fluxCQ (oceanic flux, emissions from
• plants and lightning-induced wildfires); fAff and fAnf are fossil fuel and
non-fossil fuel (wood fuel and biomass burning) combustion components of
• anthropogenic flux^Q, equal to 0.45 and 0.43, respectively, in 1985.
• The time dependence of SJJ^Q and fluxQQ are shown in Figure 4. The
largely anthropogenic component fluxCQ displays a large increase — ~6-fold
• from i860 to 2035 — whereas S«uur, mostly natural in origin, changes little.
Model runs to simulate the period i860 to 2035 are based on combinations
f§ of the parameterized CHn and CO inputs described above. Five scenarios
_ (Models 1-5 in Table 5) are chosen to look at background tropospheric changes
™ assuming constant NOX. In each case the model is initialized to give 120 ppbv
• CO and 1.6 ppmv CHj| for 1985. Calculations are performed with perturbed
inputs (CO fluxes, CH^ mixing ratios or fluxes) at 10 to 30 year intervals.
• In fact, time-dependent calculations show that Cffy and CO can exhibit slower
transients than would be predicted from their respective steady-state life-
• times. Models 1 and 2 employ constant CH|j flux at all times, with Model 1
• based on a minimum CO change (Type 1-CO) and Model 2 based on a larger CO
change (Type 2-CO). Models 3, 4 and 5 simulate scenarios based on large
• temporal changes in CHj, (mixing ratios from ice core data with extrapolation
to 2035) and varying degrees of change in CO. Model 3 is Type 1-CO and Model
P 4 is Type 2-CO. Finally, we consider an extreme case in which no CO sources
jm change in time, i.e. constant values of SJJ^Q and flux^g, to look at the
* effects of perturbed Cfy on OH and CO (Model 5). This is similar to Models 1
V and 2 in assigning all OH changes to only one of the perturbed gases.
9-3J. M2°-«. NQX: Besides CH^ and CO, these trace species and other parameters,
11
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e.g. uv radiation, and rainout rates, are critical in determining OH concen-
trations. Water vapor, radiation fluxes and rainout rates are fixed at
constant values (Section 2) for all runs except for the perturbed climate case
described later.
Ozone varies so widely in time and space, even on a short term, that
there is no way of extracting with certainty historical trends to be followed
in calculations. CH^ and CO perturbations establish self-consistent Og levels
when Oo is calculated in model runs with constant boundary conditions: fixed
stratospheric input of odd oxygen and surface removal at the lower boundary.
It was shown in Section 2 that NOV is critical in determining perturbed
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OH concentrations yet uncertainties in the odd nitrogen budget [Logan, 1983;
Liu et al, 1983], introduce some arbitrariness in the selection of appropriate
NOX levels for CH^ and CO perturbations. There is little doubt that anthro-
pogenic activities exert a large and changing role in NOV on a local basis,
A
but effects on the background troposphere are less clear. We have taken a
simplified approach in choosing three alternate NOX scenarios to accompany
CO/CHjj perturbation calculations for background midlatitude environments.
Two sets of CH /CO perturbations assume nearly constant NO... One
4 x
simulates the nonpolluted marine midlatitude troposphere where we assume low
NOV boundary conditions (LNML, Table 3) at all times. A second NO., scenario
A A
simulates a nonpolluted continental midlatitude environment with ground-level
NOY ~1 ppbv at all times and HNML boundary conditions.
A
Assuming constant NOX while CO increases, i.e. CO/NOX is increasing in
time, implies that NMHC and CO emissions increase faster than NOV. We per-
A
formed one set of calculations in which NO emissions increase along with CO
emissions. Starting with low surface NOV (20 pptv in i860) model NO influx at
A
succeeding years increases at the rate given by Brimblecombe and Stedman
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[1982] until NOX is 0.2 ppbv in 1985. Extrapolating forward from 1985, NOX
— input follows the pattern of the past two decades with some leveling off due
• to pollution controls [Kavanaugh, 1986]. We do not know the historical record
• of NOX, but this may be a more realistic representation of its temporal
evolution in some continental environments than assuming constant 1 ppbv
• N0_. We refer to these as "transitional regions."
Model 3 is the only case run with a time-varying NO influx. For consis-
m tency with the limits suggested by low and high NOX scenarios, calculations
• with changing NO are performed with specified Oo, beginning with the Model 3
low NOX Oo profile for 1860 and ending with a higher NOX 0? profile for
• 2035. Surface NOX increases from 20 pptv in i860 to 480 pptv in 2035.
P B. Results
£ Model results simulating CH^-CO-OH from 1860 to 2035 are. shown in Figures
5 (low NOX) and 6 (high NOX). Ground level CHjj and CO mixing ratios and
M fractional changes in column-integrated OH for Models 1 and 2 with low NOX are
shown in Figure 5a. With constant CHj, flux, CO perturbations alone determine
P CO and OH behavior and CH^ response. In 1860 Ofy is 1.2-1.3 ppmv but CO
levels are 2-3 times lower than in 1985. From 1985 to 2035 CO is predicted to
• double or triple at the surface (from 120 to 270 or 355 ppbv). In Models 1
• and 2 OH decreases are 22-34? from i860 to 1985 with an additional 25-34? loss
(and a 25? increase in CH^) projected over the next fifty years. Figure 5a .
• shows that if CO perturbations alone are driving OH changes, then significant
changes in background CHjj have occurred since 1860, but not as great as those
m deduced from ice core data (Figure 5b).
H Figure 5b shows Models 3, 4 and 5 where a steady increase in CH^ has been
specified from 1860 to 2035. Models 3 and 4 correspond to changing scenarios
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for CO sources (dashed and solid lines respectively). Model 5 (dotted lines)
shows CO and OH perturbations responding to increasing CHjj in the absence of
altered CO emissions. When both CO and CHjj changes are specified (Models 3
and 4), changes for OH are of greater magnitude than when only CH^ or CO is
perturbed. For Model 5 in 1860 CO is "100 ppbv (probably unrealistically
high) and it may increase to 150 ppbv in 2035. The concurrent OH change is a
13% loss from 1860 to 1985 and an additional 13* loss from 1985 to 2035.
Figure 6 shows surface CHjj, CO and total OH for Models 1-5 calculated at
"1 ppbv NO™ at the surface. Because CO and CH^ are largely controlled by
their respective sources, CO and CHjj patterns are not very different from the
low NOX case (of Figure 5). However, the OH decrease accompanying each CH^/CO
perturbation is roughly half the magnitude of its low NOV counterpart. This
X
is because at higher NOX, CH^ and CO perturbations cause increases in boundary
layer OH that offset mid-tropospheric losses (Figure 1). In Model 5 OH is
almost constant from 1860 to the present.
Our CO and CH^ levels for 1950 are higher than those deduced by Levine et
al [1985]. The Levine et al 1950 CO and CH^ values occur at "1930 where
Figures 5b and 6b show OH 25-35% higher (low NOX) and 10-15% higher (high NOX)
than in 1985. They estimate 25% higher OH with NOX and 0, different from our
cases. Although our results are not strictly comparable to Levine et al
[1985], we calculate OH changes of similar magnitude.
Figure 7 shows Model 3 type CH^ and CO with NOX and OH calculated with
the "transitional region" NOX scenario. OH increases slightly and then de-
creases slowly. The complexity of NO -OH interaction is evident when one
A
compares the boundary layer behavior of OH in the three NOV cases run with
X
Model 3. Figure 8 shows OH changes in the boundary layer (0-2 km in the
model) for the three NOX scenarios. Vertical profiles of OH are shown for
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• three years, 1970, 2005, 2035, along with a bar graph of total and boundary
• layer OH column depth. Profile shapes differ sharply among the cases. There
is also a pronounced difference in boundary layer OH trend, which at increas-
• ing concentrations of NOX becomes a large fraction of total OH. The rela-
tionship between boundary layer and total OH implies that localized and
I regional scale processes may affect global OH. Even if most of the tropo-
_ sphere is isolated from the urban environment, and OH is decreasing as a whole
™ (as globally increasing CO and CH^ suggests), transport among various regions
• needs to be included in a full investigation of the problem. In other words
CO and Cfy perturbations are a. problem that is chemically and dynamically more
|H complex than can be treated in a one-dimensional model.
™ 4. DISCUSSION
I
Changing CH^-CO-OH levels in the background troposphere imply: (1)
• changes in tropospheric lifetimes for many trace species; (2) CH^ and 0,
changes which may affect climate. Since OH controls lifetimes of most
• terrestrially derived gases, perturbations to atmospheric OH alter rates of
• photooxidation throughout the troposphere. For example, reduced OH means a
slower formation of atmospheric acids, at least in the unpolluted tropo-
• sphere. As CO increases over time, the ratio OH/H02 increases due to CO + OH
-> C02 + H02. This leads to increasing levels of H202. At low NOX we
I calculate a doubling of H202 from 1860 to the present day.
« Changes in atmospheric lifetimes of hundreds of trace gases, e.g. reac-
~ tive hydrocarbons, sulfur and nitrogen compounds, may have occurred since 1860
• as a consequence of OH perturbations. Consider, for example, Ofy itself.
There are two ways in which CHjj levels can be forced to change: (1) by
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Paper 5
altering CH^ emissions; (2) by changing the mean level of atmospheric OH.
Looking at Models 1 and 2 where no change in surface CH^ emissions is assumed,
we see that CO increases alone (with OH decreasing) could have caused back-
ground level Cfy to increase 15-20? from 1860 to 1985. From 1985 to 2035 an
additional 20% increase in CH^ is predicted. From the magnitude of CH^
increases and OH losses shown in Figure 5a, we estimate that "half the CHjj
increase shown in Models 3 and 4 (Figure 5b) is due to increased lifetime
relative to OH (suppressed by CO) and the rest to increased emissions of
CHjj. Khalil and Rasmussen [1985] and Levine et al [1985] reached a similar
conclusion in analyzing past methane trends.
Changes in CH^-CO-OH chemistry may affect climate because 0,, CH^, and
C02 (to which CO converts by OH oxidation) are greenhouse gases. All of the
CHjj and CO scenarios simulated in our study (Figures 5 and 6) are accompanied
by steady increases in tropospheric Oo. Surface 0^ mixing ratios for 1860,
1985, 2035 are given in Table 5. From i860 to 1985 we calculate an 8-22%
increase in Oq for constant, low NOX conditions. For high NOX the increase
from 1860 to 1985 is as great as 78% (Model 4). Furthermore, in a set of
Model 3 calculations with "transitional NOX" and 0^ unconstrained (surface
deposition instead of fixed mixing ratio) Oq is only 10 ppbv in i860 and 27
ppbv in 1985. Dignon and Hameed (1985) have suggested that increasing NOV
A
emissions probably caused some of the recent increases in tropospheric Oo.
Calculated tropospheric O? increases are consistent with observations
that tropospheric Oo has been increasing over the past decade or two [Bojkov,
1984; Logan, 1985] and possibly longer [Volz et al, 1985; Bojkov, 1986]. If
tropospheric 0? increases are part of a long-term trend, then there are
continuous perturbations in background chemistry and potentially in global
climate, since 0, is a greenhouse gas [Wang et al, 1976; Fishman et al, 1979;
16
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• Paper 5
• Ramanathan et al, 1985]. Depending on the altitude dependence of these
jm increases, changes in tropospheric On may be perturbing the earth's radiation
field. For example, Ramanathan et al [1985] have shown that a 25% increase in
• ozone over the past 100 years could have contributed to a modest rise in
global temperature and continuing increases in On, along with CHj, and other
non-C02 greenhouse gases, could have growing effects on global climate.
— Secular CO increases over the past century may be influencing global
* climate through C02 because CO contributes to C02 through the oxidation CO +
• OH -> H + C02- Atmospheric CO increases also affect radiation by suppressing
OH and allowing On and CHjj to build up, even if CH^ emissions do not increase.
• We note that global climate change would feed back on background CH^-CO-
OH through: (1) altered temperature perturbing chemical reaction rates and
" tropospheric water vapor; (2) altered precipitation patterns. Since the
• nature of these changes is not clear [Hansen et al, 1984] we do not know how
feedback to trace chemistry would occur. The greatest effect might be modi-
I fication of average water vapor. We performed a set of calculations (Models
1-5 with high and low NO..) assuming constant relative humidity [Manabe and
Wetherald, 1967] and perturbed temperature from Ramanathan et al [1985].
M Higher temperatures imply more water vapor (Table 1), leading to more OH via
0(1D) + H20 -> 20H.
• In all cases the decline predicted for the next 50 years (Figures 5 and 6) is
substantially less than if mean temperature is assumed constant from 1985 to
| 2035. The fractional OH losses shown in Figures 5 and 6 are reduced 6-8%
~ with higher water vapor. The opposite effect (reinforcement of OH loss) might
™ occur if climate change means increased precipitation and greater removal of
• OH reservoirs like HNO^ and H202. A complete investigation of perturbed
photochemical-climate interaction is beyond the scope of this paper.
i
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Paper 5
5. SUMMARY AND CONCLUSIONS
The effects of perturbed CO and CH^ on tropospheric OH are complex.
Total tropospheric OH always decreases when CO or CHh is increased, but under
certain conditions, surface and upper tropospheric OH may actually increase.
The magnitude of OH changes is highly sensitive to local NOX levels.
CHjj-CO-OH coupling means that a positive perturbation in either CO or CH^
emissions causes both CO and Cfy to increase throughout the troposphere. A
practical consequence of the coupling is that observed changes in CO or CH^
cannot be ascribed unambiguously to enhanced CO emissions, CHjj emissions or to
a given combination of the two — or to changes in OH for other reasons. It
is essential to determine sources and emission rates of individual tropo-
spheric gases that show secular changes to distinguish cause effect and to
make meaningful long-term predictions.
Recent reports of changing CO and CH^ form the basis for a series of
photochemical model calculations simulating tropospheric trace gases from 1860
to 2035. Several scenarios are considered. In pristine environments (low,
constant NOX) CH^ will probably continue to increase, reaching a value of 2
ppmv by 2035 (assuming that growing anthropogenic CO emissions perturb OH but
CH^ emissions are unchanged) or 3 ppmv if CHjj emissions also rise. During
that time CO will increase from 20% to two or three times its current level,
depending on the intensity of CO emissions. Looking back to 1860 (a reference
year for the preindustrial atmosphere) we find CH^ at 50-80/i and CO at 45-85^
of present day levels and OH 22-^5% higher than at present.
At higher levels of NOX tropospheric OH may have decreased monotonically
since 1860 as in low NOX environments (although at a smaller rate) or it may
have increased to a maximum level then decreased. The complexity of the
18
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• Paper 5
• urban-influenced environment and its potential interaction with remote
• environments complicates interpretation of CO, CH^, and OH trends. A more
nearly complete treatment of NMHC chemistry and boundary layer dynamics is
• required than is included in the present modeling study.
There are global consequences of projected CH^ and CO trends. In all NOX
• scenarios considered tropospheric 0, shows a monotonic increase from 1860 to
12035. In the case of background NOV in transition from 20 pptv in 1860 to 0.2
ppbv in 1985, surface ozone would have increased from 10 ppbv in 1860 to 27
• ppbv in 1985. This compares favorably with recently published Oo observations
taken at a midlatitude continental site. Decreased OH means longer tropo-
| spheric lifetimes for hundreds of trace gases, both natural and anthropogenic,
_ and enhanced escape of some of these species to the stratosphere. In the case
' of CHjj directly and in the case of CO indirectly (through enhanced formation
A of Oo and oxidation of CO to C02) there are perturbations in the earth's
radiative forcing and possibly climate.
I
ACKNOWLEDGMENTS
• A. M. T. acknowledges support from an NCAR Advanced Study Program
• Postdoctoral Fellowship and from the NASA Tropospheric Chemistry Program.
Thanks to S. Walters and J. Herwehe for programming assistance.
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Paper 5
REFERENCES
Aikin, A. C., J. R. Herman, E. J. Maier, and C. J. McQuillan, Atmospheric
chemistry of ethane and ethylene, J_.. Geophys. Res., 87, 3105-3118, 1982.
Atkinson, R. and J. N. Pitts, Jr., Kinetics of the OH radical with HCHO and
CHgCHO over the temperature range 299-466°K, J_._ Chem. Phys.. 60, 3581-
3584, 1978.
Blake, D. R., E. W. Mayer, S. C. Tyler, Y. Makide, D. C. Montague, and F. S.
Rowland, Global increase in atmospheric methane concentrations between
1978 and 1980, Geophys. Res. Lett.. 9, 477-480, 1982.
Bojkov, R., Tropospheric ozone, its changes and possible radiative effects,
Spec. Environ. Rep., 16, World Meteor. Org., Geneva, 1984.
Bojkov, R., Surface ozone during the second half of the nineteenth century, J_._
Glim. Appl. Meteor.t 25. 343-352, 1986.
Brewer, D. A., T. R. Augustsson, and J. S. Levine, The photochemistry of
anthropogenic nonmethane hydrocarbons in the troposphere, J_._ Geophys.
Res.. 88, 6683-6695, 1983.
Brimblecombe, P., and D. H. Stedman, Historical evidence for a dramatic in-
crease in the nitrate component of acid rain, Nature. 298, 460-462, 1982.
Calvert, J. G., and J. N. Pitts, Jr., Photochemistry. Wiley, New York, 1966.
Chameides, W. L., and D. D. Davis, The photochemistry of tropospheric trace
species: the central role of radicals and their possible variability, in
Chemical Events in the Atmosphere and Their Impact on the Environment,
Pontifical Acad. Science, Rome, 1985.
Chameides, W. L., S. C. Liu, and R. J. Cicerone, Possible variations in
atmospheric methane, J_._ Geophys. Res.. 82, 1795-1798, 1977.
Cox, R. A., and M. J. Roffey, Thermal decomposition of peroxyacetylnitrate in
the presence of nitric oxide, Environ. Sci. Technol.. J_1, 900-906, 1977.
20
-------
I
I
Paper 5
Craig, H., and C. C. Chou, Methane: The record in polar ice cores, Geophys.
Res. Lett.. 9, 1221-1224, 1982.
Crutzen, P. J., A discussion of the chemistry of some minor constituents in
• the stratosphere and troposphere, Pure Appl. Geophys.. 106-108. 1385-1399,
1973.
P Crutzen, P. J., The role of NO and N02 in the chemistry of the troposphere and
• stratosphere, Ann. Rev. Earth Planet. Sci., Tj. 443-472, 1979.
Crutzen, P. J., The role of the Tropics in atmospheric chemistry, in
I Geophysiology of Amazonica, ed. by R. E. Dickinson, J. Wiley 4 Sons,
N. Y., 1986.
| Dignon, J., and S. Hameed, A model investigation of the impact of increases in
•anthropogenic NOV emissions between 1967 and 1980 on tropospheric ozone,
'
J_._ Atmos. Chem.. 3, 491-506, 1985.
A Ehhalt, D. H., R. J. Zander, and R. A. Lamontagne, On the temporal increase of
tropospheric Cfy, J^ Geophys. Res.. 88, 8442-8446, 1983.
• Fishman, J., V. Ramanathan, P. J. Crutzen, and S.-C. Liu, Tropospheric ozone
and climate, Nature. 282. 818-820, 1979-
• Graedel, T. E., and J. E. McRae, On the possible increase of the atmospheric
• methane and carbon monoxide concentrations during the last decade,
Geophys. Res. Lett.. 7, 977-979, 1980.
• Greiner, N. R., Hydroxyl radical kinetics by kinetic spectroscopy: V. Reac-
tions with alkanes in the range 300-500 K, J^ Chem. Phys., 53, 1070-1076,
I 1970.
M Hameed, S., J. P. Pinto, and R. W. Stewart, Sensitivity of the predicted CO-
OH-CHjj perturbation to tropospheric NOX concentrations, J.. Geophys. Res.,
• 84, 763-768, 1979.
Hansen, J., A. Lacis, D. Rind, G. Russell, I. Fung, and S. Lebedeff, Evidence
i
I
-------
Paper 5
for future warming: How large and when, (^ Conf. of the Natl. Forest
Prod. Assoc., 25-27 June 1984, Boulder, CO.
Horowitz, A., and J. G. Calvert, Wavelength dependence of the primary
processes in acetaldehyde photolysis, J.. Phys. Chem.. 86, 3105-3114, 1982.
Kasting, J. F., and H. B. Singh, Nonmethane hydrocarbons in the troposphere:
Impact on the odd hydrogen and odd nitrogen chemistry, J^ Geophys. Res.,
submitted, 1986.
Kavanaugh, M., Estimates of future CO, ^0, and NOX emissions from energy
combustion, Atmos. Environ., submitted for publication, 1986.
Keeling, C. D., Industrial production of carbon dioxide from fossil fuels and
limestone, Tellus. 25, 174-198, 1973.
Khalil, M. A. K., and R. A. Rasmussen, Carbon monoxide in the earth's
atmosphere: Increasing trend, Science, 224, 54-56, 1984.
Khalil, M. A. K., and R. A. Rasmussen, Causes of increasing atmospheric
methane: Depletion of hydroxyl radicals and the rise of emissions,
Atmos. Environ., Qt 397-407, 1985.
Lenschow, D. H., R. Pearson, Jr., and B. B. Stankov, Measurements of ozone
vertical flux to ocean and forest, J._ Geophys. Res.. 87, 8833-8838, 1982.
Levine, J. S., C. P. Rinsland, and G. M. Tennille, The photochemistry of
methane and carbon monoxide in the troposphere in 1950 and 1985, Nature,
318. 254-257, 1985.
Levy, H., Photochemistry of the lower troposphere, Planet. Space Sci., 20,
919-935, 1972.
Liu, S.-C., M. McFarland, D. Kley, and 0. C. Zafiriou, Tropospheric NOX and 0^
budgets in the Equatorial Pacific, J_.. Geophys. Res., 88, 1360-1368, 1983.
Logan, J. A., Nitrogen oxides in the troposphere: Global and regional budgets,
J. Geophys. Res.. 88, 10785-10808, 1983.
22
-------
• Paper 5
™ Logan, J. A., Tropospheric ozone: Seasonal behavior, trends and anthropogenic
• influence, J^ Geophys . Res.. 90. 10463-10482, 1985.
Logan, J. A., M. J. Prather, S. C. Wofsy, and M. B. McElroy, Tropospheric
• chemistry: A global perspective, J_._ Geophys . Res.. 86, 7210-7254, 1981.
Manabe, S. and R. T. Wetherald, Thermal equilibrium of the atmosphere with a
• given distribution of relative humidity, J^ Atmos . Sci. . 24, 241-259,
• 1967.
NASA/JPL, Chemical kinetics and photochemical data for use in stratospheric
• modeling, Eval. Number 5j. JPL Publ. 82-57, Jet Propul. Lab, Pasadena,
Calif., 1982.
• NASA/JPL, Chemical kinetics and photochemical data for use in stratospheric
m modeling, Eval. Number 6^ JPL Publ. 83-62. Jet Propul. Lab, Pasadena,
Calif., 1983.
B
NRC (National Research Council), Changing climate: Report of the Carbon Di-
oxide Assessment Committee, National Academy Press, Washington, D. C.,
1982.
Oort, A. H. , and E. M. Rasmusson, Atmospheric circulation statistics, NOAA
_
• Prof. Paper 5. U. S. Govt. Print. Off., 1971.
• Ramanathan, V., R. J. Cicerone, H. B. Singh, and J. T. Kiehl, Trace gas trends
and their potential role in climate change, J_._ Geophys . Res. , 90. 5547-
| 5566, 1985.
Rasmussen, R. A., and M. A. K. Khalil, Increases in the concentration of
• atmospheric methane, Atmos . Environ. , 15 , 883-886, 1981.
• Rasmussen, R. A., and M. A. K. Khalil, Atmospheric methane in the recent and
ancient atmospheres: Concerns, trends, and interhemispheric gradient, J^
I Geophys. Res.. 89. 11599-11605, 1984.
Rinsland, C. P., J. S. Levine, and T. Miles, Concentration of methane in the
I
I
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Paper 5
troposphere deduced from 1951 infrared solar spectra, Nature. 318, 245-
249, 1985.
Rinsland, C. P. and J. S. Levlne, Free tropospheric carbon monoxide
concentrations in 1950 and 1951 deduced from infrared total column amount
measurements, Mature 318. 250-254, 1985.
Rudolph, J. and D. H. Ehhalt, Measurements of Cj-Cc hydrocarbons over the
North Atlantic, J^ Geophys. Res.. 86, 11959-11964, 1981.
Seiler, W., H. Giehl, E.-G. Brunke, and E. Halliday, The seasonality of CO
abundance in the Southern Hemisphere, Tellus. 3_6b, 219-231, 1984.
Singh, H.B., L. J Salas, H. Shigeishi, and E. Scribner, Atmospheric
halocarbons, hydrocarbons and sulfur hexafluoride: global distributions,
sources and sinks, Science. 203. 899-903, 1979.
Singh, H. B., and P. L. Hanst, Peroxyacetylnitrate (PAN) in the unpolluted
atmosphere: An important reservoir for nitrogen oxides, Geophys. Res.
Lett.. 8,941-944, 1981.
Stauffer, B., G. Fischer, A. Neftel, and H. Oeschger, Increase of atmospheric
methane recorded in Antarctic ice core, Science, 229, 1386-1388, 1985.
Sze, N. D., Anthropogenic CO emissions: Implications for the atmospheric CO-
OH-CHu cycle, Science. 195. 673-675, 1977.
Thompson, A. M., The effect of clouds on photolysis rates and ozone formation
in the unpolluted troposphere, J^ Geophys. Res., 89, 1341-1349, 1984.
Thompson, A. M., and R. J. Cicerone, Clouds and wet removal as causes of
variability in the trace-gas composition of the marine troposphere, J_^
Geophys. Res.. 87. 8811-8826, 1982.
Turco, R. P., and R. C. Whitten, A note on the diurnal averaging of
aeronomical models, J_._ Atmos. Terr. Phys., 40, 13-20, 1978.
U^ §_._ Standard Atmosphere, 1966, National Oceanic and Atmospheric
24
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• Paper 5
I Administration, NASA, U. S. Air Force, 1966.
• £L. S.. Standard Atmosphere Supplement. 1976, National Oceanic and Atmospheric
Administration, NASA, U. S. Air Force, 1976.
• Volz, A., H. G. J. Smit, and D. Kley, Ozone measurements in the 19th century:
The Montsouris Series, Eos, 66, 815, 1985.
| Vukovich, F. M., J. Fishman, and E. V. Browell, The reservoir of ozone in the
« boundary layer of the Eastern United States and its potential impact on
™ the global tropospheric ozone budget, J_._ Geophys. Res., 90, 5687-5698,
• 1985.
Wang, W., Y. Yung, A. Lacis, T. Mo, and J. Hansen, Greenhouse effects due to
p manmade perturbations of trace gases, Science, 194, 685-687, 1976.
_ Wofsy, S. C., Interactions of CHi, and CO in the earth's atmosphere, Ann. Rev.
I
• Earth Planet. Sci.. 4, 441-469, 1976.
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Paper 5
TABLE 1
FIXED TROPOSPHERE MODEL PARAMETERS
Mid-Latitude
Low Latitude
|Alti-|Temp
tude
(km) (K)
15
14
216.
216.
13 |216.
12 (216.
11 J216.
10 |223.
9
B
229.
236.
7 (242.
f*
5
249.
255.
4 |262.
3
2
268.
275.
1 §|2S1.
0 |288.
. | Molecular I H_o Volume 1 Pertur- | Team .t
IDensity \ Taxing (bed** H o|
|N(cm~3) 1 Ratio IFactors 1 (K)
6J4.05*
6J4.74
615.54
616.49
8|7.59
3(8.60
7(9.71
2J1.09
7|1.23
2)1.37
7(1.53
2|1.70
7(1.89
2(2.09
7(2.31
2(2.55
!
(18)13
(18) |3
(18) J4
(18)]4
(18)17
(18)11
(18) [3
(19)|3
(19) |3
(19)18
(19)|1
(19)|2
(19)|3
(19)14
(19)|5
(19) (7
!
.10 (-6)
.50 (-6)
.00 (-6)
.30 (-6)
.00 (-6)
.20 (-5)
.30 (-5)
.00 (-5)
.00 (-4)
.86 (-4)
.37 (-3)
.03 (-3)
.25 (-3)
.55 (-3)
.92 (-3)
.50 (-3)
1.48
1.48
1.48
1.48
1.48
1.45
1.40
1.39
1.36
1.29
1.27
1.25
1.24
1.22
1.21
1.20
!
(203.7
(210.3
(217.0
(223.6
(230.3
1237.0
1243.7
(250.4
[257.1
1 263 . 8
(270.6
1277.4
(284.3
|289.4
(295.9
[302.6
I
( Molecular (HjO Volumett|H2 Mixing!
IDensityt | (
|N(on~ J) IMixing Ratio! Ratio
I
(4.42 (13)
(5.20 (13)
(6.09 (18)
(7.12 (18)
(8.27 (18)
(9.28 (18)
|1.04 (19)
|1.16 (19)
[1.29 (19)
(1.43 (19)
(1.58 (19)
jl.75 (19)
(1.93 (19)
|2.12 (19)
(2.32 (19)
(2.55 (19)
|
1
| 3.00
| 3.60
| 4.80
| 5.30
! 1.00
j 5.00
| 2.42
| 7.89
| 1.39
| 2.27
j 3.54
| 5.03
| 7.57
1 1.17
! 1.85
| 2.53
I
(-6)
(-6)
(-6)
(-6)
(-5)
(-5)
(-4)
(-4)
(-3)
(-3)
(-3)
(-3)
(-3)
(-2)
(-2)
(-2)
i
is.
15.
(5.
|5.
15.
[5.
is.
(5.
is.
(5.
(5.
(5.
15.
is.
(5.
|5.
!
15 (-7)
24 (-7)
30 (-7)
35 (-7)
38 (-7)
40 (-7)
42 (-7)
44 (-7)
46 (-7)
47 (-7)
48 (-7)
49 (-7)
49 (-7)
50 (-7)
50 (-7)
50 (-7)
*US Standard Atmosphere (1976)
••Simulation of perturbed climate in the year 2035: midlatitude temperatures
are increased 3K at all altitudes: Corresponding H_o volume mixing. ratios,
assuming constant relative humidities are obtained oy multiplying standard
mixing ratios by these factors.
US Standard Atmosphere Supplements (1966)
tfOort and Rasmusson (1971)
***4.05 (13) signifies 4.05 x 10
IS
§Not shown are values for 8 additional grid points between 0 and 1 km which are
used for calculations in the boundary layer fThompson and Cicerone. 1982]
-------
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Paper 5
CM
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-------
Paper 5
Species
Table 3
Photochemical Model: Trace Gases and Boundary Conditions
Upper Boundary (15 km)
Boundary Condition
r*H n PH n
y L*41^U j \*Cl'3\J'*
HJfo, PAN, §H,c3o
CH^OOH, C2HC
"~ , H, OH,'
CO
C2»6
Low NOx (LNLL. LNML)
0, vi"
0{3P) v
= 0.05
= 0.5
influx: 5x1010 cm'2 s"1
influx: 4xl03 cm'2 s"1
photochemical equilibrium
influx: 2.5x10° cm"2 s"1
zero outflux
yt = 0.0003
v = 0.1
v = 0.013
Lower Boundary £0 km)
High NOx (HNML)
v = 0.5
v = 0.5
NO
NO,
H2CO,CH,OOH
CR,CHO,
•)
CH,,
photochemical
equilibrium
influx=7.5x108cm"2s~'
v = 0.01
v = 0.5
v = 0.1
v = 0.5
v = 0..5.
fixed: 1.5 ppbv
influx gives
120-300 ppbv (LNML)
85-214 ppbv (LNLL)
influx gives 1.6-4 ppmv
photochemical equilibrium
influx=7.5x1010 cm"2 s'1
v = 0.01
v = 1.0
v = 0.2
v = 1.0
X * 1.0
fixed: .1.5 ppbv
influx gives 120-300 ppbv
influx gives 1.6-4.0 ppmv
Value given is diurnally averaged and is one-half that used in
time-dependent calculations.
t Upper boundary: v = troposphere-to-stratosphere transfer velocity
(cm s~')
boundary: v = surface transfer or deposition velocity (cm s"1)
Rainout loss (rate = 1.65x10"° s"' below 6 km) in species continuity
equation. Applies to all models.
-------
Low NOX: Stotal = 1.9 x 1011 cm"2 s'1
High NOX: Stotal = 4.8 x 1011 cm'2 s'1
Type 1-CO 25* 35* 40*
Type 2-CO 25* 65* 10*
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H Table 4: Parameterization of CO Sources — 1985
I
Type 1-CO 15* 35* 50*
• Type 2-CO 15* 65* 20*
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Paper 5
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Paper 5
Table 5: Model Characteristics.
1
Model 1
Model 2
Model 3
Model 4
Model 5
Input
CH4
CO
Output
0^ (0 km,
1860
19853
2035
03 (0 km,
1860
1985
2035
constant CH^ flux
Type 1-CO
low NOX):
28 ppbv
30 ppbv
34 ppbv
high NOX):
35 ppbv
41 ppbv
52 ppbv
Type 2 -CO
26 ppbv
30 ppbv
36 ppbv
31 ppbv
41 ppbv
57 ppbv
Cfyj m. ratio from ice
[Khalil
Type 1-CO
25 ppbv
30 ppbv
36 ppbv
26 ppbv
41 ppbv
60 ppbv
core data
and Rasmussen , 1 985 ]
Type 2-CO
25 ppbv
30 ppbv
37 ppbv
23 ppbv
41 ppbv
63 ppbv
constant
fluxco,
SNMHC
27 ppbv
30 ppbv
34 ppbv
32 ppbv
4 1 ppbv
53 ppbv
' Models 1-5 are run at both high and low constant MOX conditions; a scenario
with NOX driven by increasing NO emissions is run with Model 3.
2 CHU flux: 4.4 x 1010 cm"2 s"1 (low NOV); 1.31 x 1011 cm'2 s"1 (high NO..).
• « A
3 OH column, 0-15 km (1985): 5.4 x 1011 cm'2 (low NOJ; 1.15 x 1012 cm'2
A
(high NOX).
-------
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Paper 5
LLJ
Q
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LOW NOx,
MID LATITUDE
(LNML)
0 X CO, 1 .0 X CH4
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OH(x10'5CM-3)
20
25
Fig. 1 OH profile (diurnally averaged) from LNML model. Solid line is for
unperturbed CO and CH^. Dotted and dashed lines are for perturbed CO or CH^
with fractional increments beyond initial values (1.5 or 2.0) determined at the
0 km level.
-------
Paper 5
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Fig. 7 Ground level CH^, CO, and NOX mixing ratios and percent change in
tropospheric OH. Model 3 scenario is followed with NOX increasing from a low
(20 pptv in 1860) to moderate level (0.49 ppbv in 2035) in response to
increasing NO emissions.
-------
2.0
1.5
1.0
<
0.5
0.0
(A)
I I I
TOTAL OH
Ixl0"cm'2l
2035 2005
11970
- 5
m
1970 2006 2036
345
OH (x10-5cm-3)
0.0
10
11
12 13 14
OH(x10-5cm-3)
15
Paper 5
12 13 14 15 16 17 18 19 20
16
17
Fig. 8 OH profiles in the boundary layer (0-2 km) for years 1970, 2005, 2035
calculated with Model 3 scenario. Bar graphs give total OH column with shaded
part showing the depth of OH from 0 to 2 km. (a) constant low NOX case; (b)
higher NOX (1 ppbv) case; (c) "transitional region" NOX.
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Paper 6
Tropospheric Ozone
•
" by
• Jennifer Logan
Harvard University
This presentation was based upon the following published paper, which has been reproduced with
_ permission of the American Geophysical Union. The author's consent has been obtained.
I
Tropospheric Ozone: Seasonal Behavior, Trends, and
• Anthropogenic Influence
by
• Jennifer Logan
| J. Logan, Journal of Geophysical Research, Vol.90, No. D6, Pages 10,463-10.482, October 20, 1985,
copyright by the American Geophysical Union.
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Paper 6
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 90, NO. D6, PAGES 10,463-10,482, OCTOBER 20, 1985
Tropospheric Ozone: Seasonal Behavior, Trends, and Anthropogenic Influence
JENNIFER A. LOGAN
Center for Earth and Planetary Physics. Harvard University. Cambridge, Massachusetts
We present an analysis of data for tropospheric ozone with a focus on spatial and temporal variations.
Surface ozone at mid-latitudes displays two modes of seasonal behavior: a broad summer maximum
within a few hundred kilometers of populated and industrialized regions in Europe and the United States
and a minimum in summer or autumn in sparsely populated regions remote from industrial activity-in
Tasmania and Canada for example. The current data base for different regions, in combination with
limited historical data, indicates that summertime concentrations of ozone near the surface in rural areas
of Europe and the central and eastern United States may have increased by approximately 6-22 ppb
(20%-100%) since the 1940's. The seasonal cycle of ozone in the middle troposphere over Europe, the
United States, and northern Japan is very similar to that at the surface with a summer maximum, but it
is quite different from that at 300 mbar, which is characterized by a maximum in spring. There is good
evidence for an increase in ozone in the middle troposphere over Europe during the past IS years and
weaker evidence for a similar increase over North America and Japan. The increase in troposphenc
ozone contributes significantly to the trend in the column of ozone and may compensate for 20%-30%
of the decrease in ozone in the stratosphere over middle and high latitudes of the northern hemisphere.
We argue that the summer maximum in ozone and the observed trends are due to photochemical
production associated with anthropogenic emissions of NO,, hydrocarbons, and CO from combustion of
fossil fuels. A strong seasonal variation in ozone observed at Natal, Brazil (6°S), may also result from
emissions of NO, and hydrocarbons, in this case from agricultural burning. Maximum concentrations at
Natal are similar to values found at mid-latitudes in summer. Tropical ozone exhibits strong spatial and
temporal variability.
1. INTRODUCTION
Ozone plays an important role in controlling the chemical
composition of the troposphere. Photolysis of ozone near 300
run,
(I)
followed by reaction of the metastable O('D) with water,
+ H2O-» OH + OH
(2)
leads to producton of OH. A variety of atmospheric species,
including CO, CH4 [Levy. 1971], NO2, and halocarbons are
removed from the atmosphere by reaction with OH. Ozone by
absorption of thermal radiation at 9.6 uM also plays an im-
portant role in the energy budget of the troposphere [Ramana-
than and Dickinson, 1979; Fishman et al., I979a].
Ozone enters the troposphere from the stratosphere and is
destroyed by heterogeneous reactions at the earth's surface
[Regener, 1949; Junge, 1962; Junge and Czeplak, 1968; Pruch-
niewicz, 1973]. Ozone is also produced and destroyed within
the troposphere by chemical reactions involving free radicals.
It is formed during the oxidation of CO, CH4, and hydro-
carbons in the presence of nitrogen oxides and destroyed by
reactions with HO, radicals [Chameides and Walker, 1973;
Crutzen, 1973].
There is a growing body of evidence to suggest that con-
centrations of ozone in the nonurban troposphere are influ-
enced by human activity. Concentrations of ozone are larger
at mid-latitudes in the northern hemisphere than at corre-
sponding southern latitudes [Pittock, 1977]. Fishman and Crut-
zen [1978] proposed that the observed excess of ozone in the
north may reflect significant photochemical production associ-
ated with sources of NO, and CO from combustion of fossil
fuels [see also Fishman and Setter, 1983; Crutzen and Gidel,
Copyright 1985 by the American Geophysical Union.
Paper number 5D0425.
0148-0227/85/005D-0425S05.00
10
1983]. Regional-scale pollution episodes, during which ozone
concentrations may exceed 100 ppb for several days [e.g., Cox
et al., 1975; Vukovich et al., 1977; Wolff et al, 1977; Guicherit
and Van Dop, 1977; Wolff and Lioy, 1980], indicate an exten-
sive anthropogenic influence on ozone near the surface in both
Europe and the United States. Measurements from a rural site
on the Baltic coast suggest that surface ozone has increased by
~60% since the 1950*s [Warmbt, 1979]. Concentrations of
ozone in the middle troposphere over Europe and North
America appear to have increased at a rate of ~ 1% per year
from 1969 to 1981 [Angell and Korshover, 1983]. These trends
could be due to increasing emissions of ozone precursors such
as NO*, hydrocarbons, and CO.
Increases in ozone are of concern, in part because of the
important role ozone plays in controlling the chemical compo-
sition and climate of the troposphere and in part because of
the deleterious effects of the gas on vegetation and human
health. For example, changes in ozone could affect the con-
centration of OH, which in turn could influence con-
centrations of the many trace species removed from the atmo-
sphere by reaction with OH. A doubling of tropospheric
ozone could increase surface temperatures by 0.9° K, according
to model results of Fishman et al. [1979a]. Ozone is thought
to be responsible for most of the crop damage caused by air
pollution in the United States. Recent field studies show that
the yields of many crops decrease linearly, as ozone is in-
creased, at a rate of 6%-8% per 10 ppb ozone [Heck et al.,
1982]. It has been known since 1956 that certain species of
trees are susceptible to damage by oxidants, and there is con-
cern at present that ozone may be contributing to the ob-
served decline of forests in Europe and the eastern U.S.
[Skarby and Sellden, 1984].
This study presents a quantitative assessment of the impact
of human activities on the distribution of tropospheric ozone.
The assessment relies on systematic measurements of surface
ozone in combination with sonde measurements of the vertical
distribution. Previous analyses of the sonde data have focused
primarily on ozone in the stratosphere [Dutsch, 1974, 1978;
,463
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Paper 6
10,464
LOGAN: TROPOSPHERIC OZONE
J
London and Angell, 1982] or have considered the behavior of
ozone at a single location [e.g., Dutsch and Ling, 1973; Mat-
tana et al., 1973; DeMuer, 1976; Attmanspacher and Hartmans-
gruber, 1976; Attmanspacher et al., 1984; Pittock, 1977;
Bojkov, 1984]. The analysis presented here focuses attention
on interesting features in the seasonal behavior of tropo-
spheric ozone that were not apparent in earlier studies [e.g.,
Chatfield and Harrison, 1977a, b; Fabian and Pruchniewicz,
1977: Fishman et a/., 19796]. Characterization of the seasonal
behavior in different environments, in combination with long-
term measurements available for only a few locations, permits
useful estimates to be made for the change in ozone resulting
from human activities.
Stratosphere-troposphere exchange is most effective during
late winter and spring [Dame/sen, 1968; Danieisen and
Mohnen, 1977; Mahlman and Maxim, 1978], and the lifetime
of ozone in the troposphere is only about 1 month. Thus one
might expect concentrations of tropospheric ozone to be larg-
est in spring in the absence of a significant photochemical
influence on the distribution of the gas. Early measurements at
a few sites did show a spring maximum in surface ozone,
leading to the hypothesis that the stratosphere provides the
dominant source of ozone to the troposphere [Regener, 1949;
Junge, 1962]. More recent data presented here and elsewhere
[Oltmans, 1981; I. E. Galbally, private communication, 1984]
confirm that surface concentrations of ozone at remote lo-
cations such as northern Canada, Tasmania, and the Pacific
Islands are highest in winter or spring, reflecting the influence
of the stratospheric source [cf. Levy et al., 1985]. By contrast,
ozone concentrations remain high from spring into late
summer at rural locations in Europe and the United States,
regions where one might expect significant photochemical
production of ozone associated with anthropogenic sources of
NO,, CO, and hydrocarbons. The broad summer maximum
extends into the middle troposphere over these regions. Sig-
nificant increases in ozone are found only in regions with a
summer maximum. The data presented here provide evidence
for a photochemical influence on large spatial scales.
We present a brief review of the chemistry of tropospheric
ozone in section 2. The data analysis is described in section 3,
and results are presented in section 4. Implications of these
results are discussed in the concluding section.
2. CHEMISTRY OF OZONE IN THE TROPOSPHERE
Ozone is formed by
O(3P) + O2
and is removed by photolysis
O3 + M
(3)
to; + 03-0(3P) + 02 (1")
The metastable O('D) is quenched by O2 and N2, though as
shown above it can also react with H2O (reaction (2)). Nitric
oxide reacts with ozone to form NO2
NO + O3-» NO2
with NO2 removed by photolysis
NO2 + hv-> O(3P)
NO
(4)
(5)
Ozone removed by (4) is reconstituted by (5) followed by (3).
Because of the cyclic nature of the chemistry, it is convenient
to define a family of species undergoing rapid reactions lead-
ing to formation or removal of ozone. We identify this family-
odd oxygen-with O3, O('D), O(3P), and NO2.
Odd oxygen is conserved in reactions (1), (3), (4), and (5). It
is formed by reactions of NO with HO2, CH3OZ, and RO2.
H02 + NO-> OH + N02
CH3O2 -I- NO-> CH3O + NO2
RO2 + NO— RO + NO2
(6)
(7)
(8)
The species RO2 represents a variety of complex organic
peroxy radicals. These reactions occur during the photooxida-
tion of CO, CH«, and hydrocarbons, for example, by
OH + CO + O2-» HO2 + CO2
H02 + NO-» N02 -I- OH
NO2 -I- fo-> NO + O
O + O2
-» O3 -(- M
Net: CO + 2O2~» CO2 + O3
Odd oxygen is removed by reaction of O('D) with H2O, by
reaction of O3 with HO2 and OH,
H02 + 03->OH
OH + O3-» HO2
by formation of nitrates from NO2,
HNO3 + M
(9)
(10)
(11)
and by heterogeneous reactions of O3 and NO2 at the earth's
surface.
Oxidation of CO, CH4, and hydrocarbons leads to net pro-
duction of odd oxygen in the presence of adequate NO,. The
rate for production of ozone is roughly proportional to the
concentration of NO, while the rate for loss is almost indepen-
dent of NO, (NO + NO2) for concentrations below ~ 200 ppt
[Fishman et al., 19796]. Loss of odd oxygen, primarily by (2)
and (9), is balanced by production in (6) and (7) for con-
centrations of NO near 30 ppt [Fishman et al., 19796; Logan
et al., 1981]. Hence regions of the globe characterized by ex-
tremely low concentrations of NO, such as the remote Pacific.
are likely to provide a net photochemical sink for odd oxygen
[Liu et al., 1983], while the continental boundary layer at
mid-latitudes, characterized by higher concentrations of NO,
is likely to provide a net source. Model studies indicate that,
averaged over the globe, chemical sources and sinks for odd
oxygen are in approximate balance and are similar in mag-
nitude to the source from the stratosphere and the sink at the
ground {Fishman et al., 19796; Logan et al., 1981; Chameides
and Tan, 1981].
Production of ozone in the troposphere is limited ultimately
by supply of CO, CH4, and hydrocarbons if NO, is available.
One molecule of ozone may be formed for each molecule of
CO as shown above, while the yield of ozone from oxidation
of CH4 could be as large as 3.5 [e.g., Logan et al., 1981]. The
potential yield of ozone from higher hydrocarbons is larger
still, 10-14 for butane and pentane [e.g., Singh et al., 1981].
3. DATA AND ANALYSIS
3.1. Surface Measurements of Ozone
Most of the data for near-surface ozone discussed here were
obtained with instruments employing one of three techniques:
a chemiluminescent analyzer sensitive to light emitted by the
reaction of ozone with ethylene, an optical device measuring
the absorption of ultraviolet light by ozone, and a variety of
wet-chemical sensors in which detection of ozone is based on
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LOGAN: TROPOSPHERIC OZONE
10.465
TABLE 1. Ozonesonde Data
Latitude
Longitude
Number
Sonde
Correction Factor
Dates
Notes
Northern Hemisphere
Resolute'
Poker Flat
Churchill
Edmonton
Goose Bay
Berlin
Linden berg
Uccle*
Hohenpeissenberg
Payerne
Biscarosse
Sapporo
Bedford'
Boulder'
Cagliari
Wallops Island
Tateno
Palestine
Kagoshima
Kennedy, Florida'
New Delhi
Grand Turk'
Poona
Ft. Sherman'
Trivandrum
75°
65°
59°
53°
53"
52°
52°
51°
48°
47°
44°
43°
42"
40°
39°
38°
36°
32°
32°
29°
29°
21°
19°
9°
8°
95°W
147°W
94°W
U4°W
60°W
13°E
14°E
4°E
11°E
7°E
rw
141°E
71°W
105°W
9°E
76°W
140°E
%°W
131°E
81°W
77°E
71 °W
74°E
80°W
77°E
597
133
51
282
235
128
355
327
150
532
491
111
358
337
574
483
913
1162
1846
1769
343
261
245
253
495
219
209
457
262
253
52
233
147
99
71
80
135
113
43
32
26
BM
ECC
ECC
BM
ECC
BM
ECC
BM
ECC
B
GDR
BM
BM
BM
BM
KC
BM
BM
MB
ECC
KC
BM/ECC
KC
BM
I
BM
1
BM
I
1.21 ± 0.14 (2%)
1.03 ± 0.09 (2%)
—
1.27 ± 0.28 (17%)
1.24 ± 0.15
1.04 ±0.10(1%)
1.25 ± 0.24 (8%)
1.22 ± 0.15 (0%)
1.05 ± 0.12 (3%)
1.29 ± 0.22 (8%)
1.26 ±0.15 (0%)
1.04 ±0.09(1%)
1.32 ± 0.27 (6%)
1.27 ± 0.14 (0%)
1.26 ±0.29 (16%)
1.21 ± 0.18 (0%)
1.33
1.09 ± 0.09 (1%)
1.24 + 0.17 (4%)
1.22 ± 0.13 (0%)
1.19 ±0.11 (1%)
1.04 ±0.1 5 (7%)
1.01 ±0.11 (0%)
—
1.16
1.24 ± 0.17 (5%)
1.23 ± 0.14 (0%)
1.00 ±0.10(1%)
1.03 ± 0.15 (4%)
1.02 ± 0.12 (0%)
—
0.99 ±0.14(1%)
—
1.42 ± 0.34 (28%)
1.24 ± 0.17 (0%)
—
1.25 ± 0.30 (16%)
1.16 ±0.17(0%)
—
1.26 ±0.26 (19%)
1.20 ± 0.20 (0%)
January 1966 to November 1979
November 1979 to Decenber 1982
July 1979 to June 1982
October 1973 to August 1979
September 1979 to December 1982
October 1972 to August 1979
August 1979 to December 1982
June 1969 to August 1980
August 1980 to December 1982
November 1966 to January 1973
January 1975 to December 1982
January 1969 to December 1980
November 1966 to December 1982
August 1968 to December 1981
March 1976 to December 1982
December 1968 to December 1982
January 1966 to May 1969
August 1963 to July 1966
July 1968 to August 1976
May 1970 to April 1982
December 1968 to December 1982
October 1977 to June 1982
December 1968 to December 1982
February 1966 to February 1969
January 1969 to December 1976
March 1966 to May 1969
February 1966 to December 1975
June 1967 to May 1969
June 1969 to December 1976
Y
S '
Y
Y
Y
Y
Y
Y
Y
Y
Y
S
Y
Southern Hemisphere
Natal
Aspendale
Christchurch
Syowa
6°
38°
43°
69°
35°W
145°E
173°E
39°E
40
752
25
135
ECC
BM
BM
KC
—
1.23 ± 0.16 (2%)
—
1.03 ± 0.14 (8%)
August 1979 to January i982
June 1965 to April 1982
March 1965 to December 1965
November 1969 to November 1980
Y
Y
All data were obtained on computer tape from the World Ozone Data Center, unless otherwise indicated. The first and second columns give
the latitude and longitude of the station. The third column gives the total number of ozone soundings with data in the troposphere during the
period given in the sixth column. The fourth column gives the type of ozonesonde used: BM, conventional Brewer-Mast; ECC, electrochemical
concentration cell, Kohmyr type; GDR. Brewer, type GDR: KC, carbon-iodine, a version of the electrochemical concentration cell; MB.
modified Brewer; I, Brewer, type India. The fifth column gives the average value and the standard deviation of the correction factor (C.F.) at
that station and, in parentheses, the percentage of soundings with correction factors outside the range 0.9-1.6 (BM type) and 0.7-1.3 (ECC
type). Where two values are given for a particular sonde type at one station, the second value is the average C.F. calculated by excluding all
soundings with C.F. outside 0.9-1.6 for BM-type sondes and outside 0.7-1.3 for ECC-type sondes (see text). Measurement programs known to
be continuing are indicated by a Y in the seventh column. An S marks stations where measurements are made irregularly in support of other
programs. .Note that the table does not include a few stations that started operation after 1979.
'An estimate of the correction factor is given in Ozone Data for the World for soundings during the winter months when a Dobson
measurement of the ozone column cannot be made.
'Data taken from Bulletin Trimestrial of the Royal Meteorological Institute of Belgium, provided by D. DeMuer.
'Data taken from ChatfieU and Harrison [19776].
'Data taken from Dutsch [1966].
its reaction with potassium iodide to form molecular iodine.
The chemiluminescent and ultraviolet devices are not thought
to suffer significantly from interference by other trace gases in
nonurban air. The wet-chemical sensor is based on an oxida-
tion reduction reaction that is not specific for ozone. Sulfur
dioxide causes a negative interference of 1 mole of O3 per
mole of SO2, while NO2 gives a slight positive interference of
a few percent [Kat:, 1977; Schenkel and Broder, 1982]. Con-
tamination by NO2 should be unimportant at rural sites
where concentrations of NO, are 0.2-10 ppb [Logan, 1983].
Modern instruments based on the KI reaction employ a filter
or scrubber to remove SO2 from the air being sampled. A field
comparison of a chemiluminescent device, an optical device,
and three wet-chemical sensors was carried out at Hohen-
peissenberg Observatory for 6 months [Attmanspacher and
Hartmansgruber, 1982]. Results from the three types of instru-
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Paper 6
10,466
LOGAN: TROPOSPHERIC OZONE
I
60
50
:4O
3O
20
i I i i i i
J F M A
S 0 N 0
M J J A
MONTH
Fig. 1. The influence of seasonal variations in the correction
factor on the seasonal distribution derived for ozone. The solid line is
an average of monthly mean values for ozone at 700 mbar at Goose
Bay, Edmonton, and Churchill, obtained with Brewer-Mast sondes.
The dashed line is obtained if results for each sounding are divided by
the correction factor before forming monthly means. Concentrations
are about 20% lower, since the average correction factor for these
stations is ~ 1.24, but the seasonal pattern is very similar.
ments agreed within about 10% (C. M. Elsworth and I. E..
Galbally, unpublished manuscript, 1984).
3.2. Ozonesonde Measurements
The two types of ozonesonde in common use, the Brewer
Mast (BM) bubbler [Brewer and Milford, 1960] and the elec-
trochemical concentration cell (ECQ [Kohmyr, 1969; Kohmyr
and Harris, 1971], are based on the reaction of ozone with KI.
The sondes differ in the design of the electrochemical cell.
Measurements with Regener sondes have been shown to
underestimate concentrations of ozone by 20%-60% below 10
km [Chatfield and Harrison, 1977a; Wilcox, 1978; Logan et aA,
1981] and were not considered in this study. We discuss some
of the difficulties associated with the electrochemical sondes
and argue that the sondc data, with careful analysis, may
provide useful information regarding spatial, seasonal, and
temporal variations of ozone in the troposphere.
Sulfur dioxide is not removed from air sampled by ozone-
sondes. Sondes may tend to underestimate ozone in the
boundary layer in polluted areas, particularly in winter, when
ozone concentrations are lowest (~ 20-30 ppb) and SO2 con-
centrations are highest. Concentrations of SO2 at rural sites in
the eastern United States, for example, are between S and 15
ppb in winter but below 5 ppb during other seasons [Mueller
J F M A
0 N
M J J A S
MONTH
Fig. 2. The ratio of the standard deviation of ozone to the
monthly mean concentration of ozone (coefficient of variation) versus
season. Results are shown for Hohenpeissenberg (H), Wallops Island
(W.I.), Goose Bay (G.B.), and Kagoshima (K) at the surface and at
700 mbar.
60
so
[40
1 30-
20-
JFMAMJJASONO
MONTH
Fig. 3. The seasonal distribution of surface ozone at Hohenpeiss-
enberg. The dashed line shows monthly averages of daily mean sur-
face values, given in Ozone Data for the World (ODW). The dotted
line shows monthly averages at 900 mbar (i.e., near surface) obtained
from sonde measurements made at ~0800. The solid line shows the
sonde data adjusted to daily mean values, using the diurnal behavior
of surface ozone as a function of season at Hohenpeissenberg [Attman-
spacher and Hartmansgruber. 1980]. AH results are averages of
monthly means for 1976 to 1983. The vertical lines show the year-to-
year standard deviation of the monthly mean. The diurnally averaged
results estimated from the sonde data are in reasonable agreement
with continuous measurements at the surface.
and Hidy, 1983]. Similar values are observed in southern Ger-
many [Reiter and Kanter, 1982]. Concentrations of SO;
above the boundary layer are generally below 1 ppb [Blu-
menthal et al., 1981; Georgii and Meixner, 1980].
The electrochemical technique does not provide an absolute
measure of the ozone concentration. Preliminary studies using
a standard ultraviolet photometer showed that concentrations
of ozone were overestimated with ECC sondes by 3%-10%,
while Brewer Mast sondes gave values too low by 4%-20%.
The precision of the sondes in the troposphere was 5%-13%
in field tests [Hilsenrath et a/., 1984; Barnes et al., 1985].
Comparison of integrated ozone profiles recorded by Brewer
Mast sondes with concurrent measurements of the ozone
column recorded by a Dobson spectrophotometer indicates
that the sonde results are too low by 10%-30% [e.g., Dutsch,
1966, see below]. Results from ECC sondes agree more closely
with Dobson measurements, largely because the KI solution
strength was originally adjusted to give this result [Kohmyr,
1969; Geraci and Luers, 1978; Torres and Bandy, 1978]. In
practice, individual soundings are multiplied by a. correction
factor to ensure that the integrated ozone column is equal to
the Dobson measurement of the ozone column. This pro-
cedure requires an estimate of the amount of ozone above the
altitude reached by the sonde, ~30 km [Dutsch et al., 1970].
The scaling procedure introduces errors caused by uncertainty
in the ozone amount above 30 km, errors associated with the
Dobson technique, and probably bias resulting from variation
of sonde efficiency with altitude. There is evidence to suggest
that the response of the sondes to ozone is altitude dependent
[Barnes et al., 1985]. Intercomparison flights have shown that
ECC sondes give concentrations of tropospheric ozone higher
than Brewer Mast sondes by 12%-20% after correction to the
Dobson column. Systematic differences are less apparent in
the stratosphere [Attmanspacher and Dutsch, 1970, 1981; Hil-
senrath et al., 1984]. Uncertainties in the response of the
sondes to ozone at tropospheric pressures and concentrations
should be resolved by further laboratory and field studies. We
believe that conclusions presented below are not seriously af-
fected by current uncertainties in absolute concentrations. Our
focus is on the seasonal behavior of tropospheric ozone and
on temporal changes derived from internally consistent data
sets.
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LOGAN: TROFOSPHERIC OZONE
10,467
3.3. Analysis of Sonde Data
Ozonesonde data were obtained for the locations given in
Table 1 from the Atmospheric Environment Service of
Canada, which coordinates the World Ozone Data Center,
and from published reports. These measurements provide the
most coherent set of data for tropospheric ozone available at
present The majority of stations use conventional Brewer
Mast sondes. The Canadian program changed from Brewer
Mast to ECC sondes in -1979; our analysis employs only
BM data. Programs in India and the German Democratic
Republic (GDR) use their own version of the Brewer Mast
sonde; some difficulties were experienced with the operation of
these devices at a recent field intercomparison [Attmanspacher
and Dutsch, 1981]. The GDR sonde appears to overestimate
tropospheric ozone by about 30%, based on comparison of
results from Lindenberg and other European stations, as
shown below in Figures 18-20. Wallops Island, U. S. A., and
Natal, Brazil, employ identical ECC sondes, and their differ-
ential response to ozone (-15% compared to the Brewer
Mast sonde) was discussed above. The program in Japan uses
a version of the ECC sonde, which appeared in field tests to
1OOr
50-
HOHENPEISSENBERG
-50
-1001-
lOOi-
50-
0
-50
-100
TO 72 74 76 78 80 82 84
70 72 74 X76X« >8 80 82 84
74 76 78 80 82 84
GOOSE BAY
WALLOPS ISLAND
10O
50
0
-50
-100
74
«76
78
80 82
Fig. 4. Time series for ozone at 500 mbar. The seasonal cycle in
ozone has been removed from the data as described in the text (see
equation (12)); monthly residuals are shown as percent deviations
from the monthly means. At Hohenpeissenberg the measurement fre-
quency increased from weekly to three times a week in winter and
two times a week in summer in 1978; at Aspendale the frequency
decreased from weekly to biweekly in 1974; at Sapporo the frequency
changed from weekly to. at most, biweekly in 1975; the influence of
these changes on the variance of monthly mean values is evident. At
Goose Bay, measurements were made with Brewer-Mast sondes until
August 1980 and with ECC sondes thereafter; the latter give -15%
more ozone in the troposphere. At Wallops Island an instrument
calibration program was instituted in 1978. and the variance in the
data was reduced considerably.
HOHENPEISSENBERG
PAYERNE-
Fig. 5. Comparison of annual mean values of ozone (nbar) at
Hohenpeissenberg (solid) and Payerne (dashed) at 900 mbar, 700
mbar, 500 mbar, 300 mbar, and 50 mbar. Measurements were made
at -1600 from 1969 to April 1977, at -0930 from April 1977 to
November 1980, at 1045 from November 1980 to December 1981,
and at 1200 thereafter. Results for Hohenpeissenberg for 1967 to 1969
(faint solid line) were given for 850 mbar rather than 900 mbar in
ODW.
give results similar to the Brewer Mast sonde [Attmanspacher
and Dutsch, 1981].
The mean correction factor for each station and its standard
deviation are given in Table 1. These factors are about 1.2-
1.3( ± 0.1-0.3) for the Brewer Mast type of sonde and about
1.0( ± 0.1-0.15) for the ECC type of sonde. The magnitude
and variability of the correction factor provide a good indica-
tion of the quality of the measurements. A recent World
Meteorological Organization (WMO) report recommends that
profiles with factors outside the range 0.8-1.4 should be con-
sidered unacceptable for BM soundings [World Meteorologi-
cal Association, 1982, hereinafter referred to as WMO 82].
This recommendation is based on results from Hohenpeissen-
berg where the correction factor is 1.09( ± 0.09). The low cor-
rection factor at this station is attributed to careful prep-
aration and conditioning of the sondes before use (WMO 82).
We chose instead to omit from the analysis profiles with cor-
rection factors outside the range 0.9-1.6 for BM soundings,
TABLE 2. Ratio of Ozone Concentrations at Payerne and
Hohenpeissenberg
Altitude
900mbar
700 mbar
500 mbar
300 mbar
P/H (1970-1976)
1.40 ±0.14
1.02 ± 0.04
1.01 ± 0.04
0.94 ± 0.08
P/H (1977-1980)
0.96 ± 0.06
0.91 ± 0.02
0.90 + 0.03
0.99 + 0.06
P/H (1977-1980)
P/H (1970-1976)
0.7
0.9
0.9
-1
At Hohenpeissenberg, ozone was measured at -0800. At Payerne.
ozone was measured at - 1600 from 1970 to April 1977 and at ~0930
from April 1977 to 1980. The second and third columns give the
average ratio (and standard deviation) of the annual mean value at
Payerne (P) to the annual mean value at Hohenpeissenberg (H) for
1970-1976 and 1977-1980, respectively. The fourth column gives the
ratio of P/H for 1977-1980 to P/H for 1970-1976 and provides a
measure of the systematic change in ozone concentrations caused by
the change in the time of measurement at Payerne.
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Paper 6
10.468
LOGAN: TROPOSPHERIC OZONE
68 1970 72
76 78 80 82
74
YEAR
Fig. 6. Annual mean values of the correction factors at As-
pendale, Hohenpeissenberg, Payerne. Resolute, and Goose Bay.
Values given for Resolute after 1979 and Goose Bay after 1980 are for
ECC sondes; all other values are for Brewer-Mast sondes.
since the average correction factor for other stations using
these sondes is 1.26. There is a small seasonal variation in the
correction factor [Pittocfc, 1977], and use of the WMO cri-
terion would have eliminated many more measurements in
summer than in other seasons. We omitted profiles with fac-
tors outside the range 0.7-1.3 for ECC soundings. Revised
N D
Fig. 8. The seasonal distribution of surface ozone at rural sites in
the United States. The upper panels show daily average values; the
lower panels show monthly means derived from daily maximum
values. The left panels show results for sites in Vermont (VT), coastal
North Carolina (NC), Wisconsin (WI), and Missouri (MO) for Oc-
tober 1978 to September 1982; these sites are all below 500-m eleva-
tion. The right panels show results for sites in Oregon (OR) and
Montana (MT) for October 1979 to December 1983, for Whiteface
Mountain (N.Y.) for 1973-1981 (V. Mohnen, private communication,
1984) and for Hohenpeissenberg, Germany (HP), for 1976-1983; these
sites are all between 1000-m and 1500-m elevation. The first six sites
are part of a rural ozone network maintained by the Environmental
Protection Agency from 1976 until 1983 [.Evans et a/., 1983; G. Evans,
private communication, 1985),
SOi
30h
10
SOT
50
4O
30
20
10
MEAN
HPVx
J F M
A M J J A
MONTH
S 0 N 0
Fig. 7. The seasonal distribution of ozone near the ground at
mid-latitudes. The upper panel shows ozonesonde results. Daily
average values were derived for Hohenpeissenberg, (HP), 900 mbar as
described for Figure 3. Results for Payerne, (PAY), 900 mbar are an
average of sonde data at ~0930 and - 1600. Daily average values for
Wallops Island (W.I.), 1000 mbar, were derived by using the diurnal
variation of rural ozone in the eastern United States as given in Boons
et ai. [1983]. The lower panel shows results from continuous surface
measurements at rural sites in the United States. Average values are
shown for: two sites in Minnesota and one in North Dakota for 1977
to 1981 (MN, ND; Pratt et al. [1983]); nine sites in the northeast
quadrant of the United States for August 1977 to July 1978 (SURE;
Mueller et al. [1983]); and three sites in the Ohio River Valley for
May 1980 to August 1981 (ORV; Shaw ami Puur [1983]). The vertical
lines show the standard deviations of the monthly means for the nine
SURE sues.
correction factors, after application of these acceptance cri-
teria, are given in Table 1.
We examined the influence of the seasonal variation in the
correction factor on the seasonal distribution derived for
ozone. Correction factors tend to be highest in late summer
and lowest between January and May but are not exactly in
phase at each station. The peak-to-peak amplitude of the
monthly mean correction factor is < 10% at eight stations,
10%-15% at seven stations, and 16%-24% at three stations
(Churchill, New Delhi, and Tateno). The peak-to-peak ampli-
tude of the monthly mean ozone concentration in the middle
troposphere is 35%-50% of the annual mean value. Conse-
quently, the seasonal variation in the correction factor has
little influence on the seasonal distribution of ozone derived
from the data, as shown for example in Figure 1.
Monthly mean values and standard deviations were calcu-
lated for each station at standard pressure levels (1000 or 900,
to
40-
20
10
- KAGOSHIMA
F M A M
S 0 N 0
J J A
MONTH
Fig. 9. The seasonal variation of surface ozone near 30°N. Diur-
nally averaged values are shown for a rural site in Louisiana (LA) (G.
Evans, private communication. 1985). Ozonesonde results are shown
for Kennedy, Florida, in the morning [Chat/ield and Harrison, 1977fc]
and for Kagoshima, Japan, for midafternoon.
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LOGAN: TROPOSPHERIC OZONE
10.469
700, 500, 300, 200, and 150 mbar) for the entire period of
observations, unless otherwise stated. The mean value in Janu-
ary, for example, is the arithmetic average of all values ob-
tained in January of any year. Monthly mean values for sta-
tions in the North American Ozone Network [Hering and
Borden, 1967] were taken from Chatfield and Harrison,
[1977fr], and results for Boulder are from Dutsch [1966]. The
coefficient of variation is typically 0.15-0.35 at 500 mbar and
700 mbar and 0.2-0.6 near the ground [Pittock, 1977;
Chatfield and Harrison, 1977b], as shown in Figure 2. There
does not appear to be a significant seasonal variation in the
coefficient of variation in the middle troposphere, except at
the Japanese stations.
In section 4 the seasonal variation in tropospheric ozone
obtained from sonde measurements is compared with results
from ground-based instruments. We demonstrate the com-
patability of the two techniques with data from Hohenpeissen-
berg. There is a significant diurnal variation in surface ozone
[e.g., Decker et al., 1976; Evans et al., 1983] that first must be
taken into account. The diurnal variation of surface ozone at
Hohenpeissenberg obtained from continuous measurements
[Attmanspacher and Hartmannsgruber, 1980] was used to
derive diurnal averages from sonde measurements made at
0700-0900. After adjustment to diurnal averages, the sonde
data near the ground reproduced the long-term seasonal be-
havior of ozone derived from ground-based measurements, as
shown in Figure 3. This comparison demonstrates that sonde
instruments may provide reliable long-term average values for
surface ozone and that results from the two techniques may be
compared quantitatively with some confidence.
Data from sonde stations with records longer than 10 years
were examined for trends. We caution that the quality of these
data is rather uneven. The measurement frequency, procedure,
time, and sonde type have changed at several stations. Figure
4 illustrates the influence of these changes on time series for
ozone at 500 mbar. The seasonal cycle in ozone has been
removed from the data by subtracting the average, monthly
mean value over the entire record from the given monthly
mean >imonth, year), e.g.,
z(month, year) = Xm°nth, year) — yfmonth) (12)
Here, $month) is the average of all the monthly means for the
particular month: January, for example. Figure 4 shows time
series of monthly residuals, rfmonth, year), expressed as per-
cent deviations from the monthly means, y(month). The top
three panels demonstrate qualitatively that the variance in
monthly mean values decreases as the measurement frequency
increases. A measurement frequency of three times weekly ap-
pears preferable to weekly or biweekly measurements. Almost
no measurements were made for 2 years at the Japanese sta-
tions and few measurements after 1978; these data are far
from ideal for trend detection. Measurements at Goose Bay
were made with BM sondes until August 1980 and with ECC
sondes thereafter; a discontinuity is evident in the data record.
There are, however, similar discontinuities in the data for
which there is no apparent rationalization and which could, of
course, be real. The data from Wallops Island show the dra-
matic reduction in data variances that resulted from imple-
mentation of a sonde calibration program in 1978.
We found that a change in the time of measurement at
Payerne from midafternoon (when ozone near the ground is
largest) to dawn (when it is smallest) influences concentrations
above the boundary layer. Values for ozone near dawn at 700
mbar and 500 mbar appear to be about 10% smaller than
those in the afternoon, based on comparison of results for
Payerne and Hohenpeissenberg (see Figure 5 and Table 2).
This need not imply a significant diurnal variation in ozone in
the middle troposphere. The 10% difference could be an arti-
fact introduced by the change in time of measurement, sonde
preparation, etc.
Trends were calculated only for measurements made with a
single instrument type, at the same time of day, to ensure that
each data set is internally consistent. The seasonal cycle was
removed from the time series by using equation (12), and the
trend in the monthly residuals, z(month, year), was calculated
by linear regression. Results are given in terms of percentage
change in ozone per year, with 90% confidence intervals cal-
culated by using the two-sided Students t test. Trends were
calculated also for each season, using the series of residuals for
the appropriate months, e.g., consecutive residuals for Decem-
ber, January, and February for winter. Sonde data have been
scaled to the measured ozone column, and there is consider-
able variability in the correction factors, as shown in Table 1
and Figure 6. In order to remove any bias introduced by
trends in either the ozone column or the correction factor, we
repeated the analysis with the correction factor removed from
each sounding. The trends in the correction factor and in the
ozone column were calculated separately in the same manner
as the trend in ozone.
4. RESULTS
4.1. Ozone at Middle and High Latitudes
4.1.1. Ozone near the ground. The seasonal variation of sur-
face ozone at mid-latitudes of the United States and Europe
follows a common pattern. Maximum concentrations occur
between March and August, as shown in Figure 7. Results
from sonde stations in central Europe and the eastern United
States (upper panel) are rather similar to those from rural
locations in the United States (lower panel) [Mueller and
Hidy, 1983; Shaw and Paur, 1983; Pratt et al., 1983]. Measure-
ments from a network of rural sites in the United States are
displayed in Figure 8, which includes a comparison with re-
sults from Germany. Average concentrations in spring and
summer are between 30 and 50 ppb (upper panel), while daily
maximum concentrations are between 45 and 65 ppb (lower
panels). Sites within 100 km of major urban areas (St. Louis
(MO) and Munich (HP) exhibit the largest maximum con-
centrations and the most prolonged sumer maxima. Maxi-
mum values at sites in less populated and less industrial envi-
ronments (upper Wisconsin (WI), Vermont (VT), and coastal
North Carolina (NC) are lower than values near St. Louis by
5-10 ppb in spring and summer, while maximum values at
two remote mountain locations (Montana (MT) and Oregon
(OR)) are lower by 10-20 ppb.
The broad summer maximum extending through July or
August is found over most of the U. S., from 35°N to 45°N
(see Figures 7 and 8) [Singh et al., 1978; Viezee et al, 1982;
Chatfield and Harrison, 19776; Mohnen et al., 1977; Mueller
and Hidy, 1983; Shaw and Paur, 1983; Pratt et al., 1983]. The
same pattern is found in Ontario, Canada (42°-45°) [Mukam-
mal, 1984]. In Europe the summer maximum extends to
higher latitudes, from 39°N to 55°N [Fabian and Pruchnie-
wicz, 1977; Attmanspacher and Hartmansgruber, 1980; Reiter
and Kantor, 1982]. A different seasonal pattern is found at
coastal locations near 30°N. Measurements from Florida
[Chatfield and Harrison, 19776] and Lousiana and prelimi-
nary data from Texas [Viezee et al., 1982] show a summer
minimum with maxima in spring and late autumn. This pat-
tern is also found in Japan near 30°N (Figure 9).
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Paper 6
10,470
LOGAN: TROPOSPHERIC OZONE
J F
MAMJJASONO
MONTH
Fig. 10. The seasonal distribution of surface ozone at rural sites
in Canada and Alaska. The upper panel shows Brewer-Mast sonde
results from Goose Bay (G.B.), Edmonton (ED) and Churchill (CH),
while the lower panel shows results for Resolute. All sonde measure-
ments were made near dawn. The lower panel also shows daily
average surface data from Barrow, Alaska [Oltmans, 1981]; the diur-
nal variation in ozone at this site is less than 1 ppb.
The seasonal cycle of ozone near the ground in Canada
(53°-59°N) is rather different from that at mid-latitudes in the
United States and Europe. Concentrations are highest in
spring, while minimum values are found between August and
MONTH(N H)
JFMAMJJASOND
0 N D J F M
MONTH (SH)
Fig. 11. The seasonal distribution of surface ozone at northern
and southern mid-latitudes. The line labeled E. U.S. is an average of
results for the nine SURE sites, the three sites in Minnesota and
North Dakota, and the four EPA sites in Vermont, North Carolina,
Wisconsin, and Missouri (see Figures 7 and 8), with each of the three
data sets given equal weighting. Also shown is the average of results
for the rural site in Missouri and for Hohenpeissenberg, Germany, the
two sites shown in Figure 8 with largest concentrations of ozone
(U.S.-Europe, high). These distributions represent daily average
values. The results for Canada (dashed line) are an average of
measurements from Goose Bay, Edmonton, and Churchill at dawn
(Figure 10). The cross-hatched area shows the daily average values
estimated from this distribution, using the diurnal variation of ozone
at Ellerslie. near Edmonton and Bitumount, Alberta (R. Angle, pri-
vate communication, 1985). Results for Cape Grim (41°S) represent
daily average values (I.E. Galbally, private communications, 1984; C.
M. Elsworth and I. E. Galbally, unpublished manuscript, 1984), while
results for Aspendale (38'S) are sonde measurements at 1000 mbar
made in early afternoon. Measurements from the southern hemi-
sphere are shown 6 months out of phase with respect to the northern
hemisphere.
50
40
UJ
g20
o
10
PAY.
1968-79
.•••'AR03A
-•••' 1931-53
J F M A
M J J A S
MONTH
0 N 0
Fig. 12. Seasonal behavior of ozone at mountain locations in
Europe. Monthly average values derived from daily maxima are
shown for Arosa, Switzerland, 1860 m, for 1951-1953 [Junge, 1962]
and for Garmisch-Partenkirchen, 740 m (G.P.), and nearby Wank
Peak, 1780 m (W.P.), for 1977-1979 \_Reiter and Kantor, 1982]. Sonde
data at 900 mbar for 1968-1976 are given for Payeme, near Arosa
(PAY). These measurements were taken at ~ 1600 hours and should
represent daily maxima. The seasonal variation of the correction
factor was subtracted out of the Payerne data by dividing results for
each sounding by the correction factor before forming monthly means
and then multiplying the monthly means by the annual mean correc-
tion factor.
October (Figure 10) (R. Angle, private communication, 1985).
Concentrations in summer are very similar at the three sonde
stations located in western, central, and eastern Canada. A
summer minimum is found also at higher latitudes, Resolute
(75°N) and Barrow, Alaska (71°N) [.Oltmans, 1981], but maxi-
mum values occur in winter rather than in spring.
Surface ozone in Canada (53°-59°N) is compared with that
in the United States and Europe in Figure 11. The results for
the United States and Europe are daily average values, while
those for Canada are values measured near dawn. We used
recent observations of the diurnal variation of ozone at two
rural sites in Alberta to estimate daily average concentrations
from the Canadian sonde data, as shown by the hatched area
in Figure 11. In summer, daily average values exceed dawn
values by ~ 11 ppb at Ellerslie, near Edmonton, and by — 6
ppb at a more remote site, Bitumount, 57°N (R. Angle, private
communication, 1985). We note that daily average values
exceed dawn values by ~ 12 ppb in the eastern United States
and by 5-8 ppb in the western United States (G. Evans, pri-
vate communication, 1985). The results in Figure 11 indicate
that average concentrations of ozone in late spring and
MICHIGAN, 1876-1880
60
_ 50
1
UJ
o
o 30
20
4O
10
J F
S 0 N 0
M A M J J A
MONTH
Fig. 13. The seasonal vanation of ozone at Lansing, Michigan, m
1876-1880. These results were derived from daily measurements at
0700-1400 made with Schoenbem's test paper (see text) and were
taken from Linvill el at. [1980].
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Paper 6
LOGAN: TROPOSPHERIC OZONE
TABLE 3. Trend in Ozone Near the Ground
10.471
Hohenpeissenberg
Sonde"
Surface*
Payerne
Resolute
Goose Bay
Wallops Island
Sapporo'
Tateno
Kagoshima'1
Aspendale
Dates
January 1970 to December 1982
1971-1983
1971-1983
August 1968 to January 1977
January 1966 to August 1979
June 1969 to August 1980
May 1970 to August 1981
January 1969 to December 1982
January 1969 to December 1982
January 1969 to December 1982
June 1965 to April 1982
Scaled to
Column
2.6 + 0.7
2.S + 1.0
1.5 ± 0.9
(0.8 + 1.4)
(0.1 ± 1.0)
-1.9+ 1.1
(0.9 + 1.2)
(1.5 ± 1.7)
2.1 ± 1.0
(-0.5 ± 1.6)
(0.2 + 0.8)
Divided by
Correction
Factor
3.2 ± 0.7
—
—
(0.6 + 1.5)
(0.0 ± 1.0)
(-1.1 ±1.2)
(0.9 ± 1.2)
(1.3 ± 1.7)
13 + 1.0
(-0.7 ±1.5)
(-0.2 + 0.8)
Trend in
Correction
Factor
—
—
NS
NS
-0.7 + 0.3
NS
NS
0.5 ± 0.3
NS
0.6 ± 0.2
Trend values in this table represent percentage change per year. All trends were calculated from
monthly residuals z(month, year) as described in section 3, unless otherwise indicated. Results are shown
for 900 mbar for Payerne and Hohenpeissenberg and for ~ 1000 mbar for the other stations. The third
column gives the trend (and 90% confidence intervals) calculated from near-surface ozonesonde measure-
ments that have been scaled to the Dobson measurement of the ozone column. The fourth column gives
the trend obtained if results for each sounding are divided by the correction factor for that sounding
before forming monthly means. This procedure should remove artifacts introduced by trends in either
the correction factor or the ozone column. The fifth column gives the trend in the correction factor. NS
indicates that the trend is not statistically significant. Results for Resolute and Goose Bay include only
measurements made with Brewer-Mast sondes.
Trend calculated from annual values for ozone at 900 mbar (sonde results).
Trend calculated from annual values for ozone obtained with surface instruments. Data for 1971-1975
were taken from Attmanspacher and Hartmannsgruber [1980]. Data for 1976-1983 were taken from
Ozone Data for the World.
'Sapporo is a major city in northern Japan. Surface ozone concentrations given by the sonde measure-
ments are lower than other mid-latitude stations, probably because of contamination by SO2. Trends in
SO, may therefore introduce an artifact in the trend estimated for ozone.
There is a 2-year gap in the data record for Kagoshima, and concentrations after 1978 appear to be
systematically smaller than those before 1976.
summer in the rural United States and Europe exceed those in
remote regions of Canada by between 6 ppb and 22 ppb or by
between 20% and 100%.
Figure 11 includes a comparison between surface ozone at
mid-latitudes of the northern and southern hemispheres.
Measurements from the clean air site at Cape Grim, Tasmania
(4 PS), show a summer minimum and winter maximum (I.
Galbally, private communication, 1984) and little diurnal vari-
ation. Concentrations at Cape Grim in summer are about 20
ppb smaller than typical values in the United States and
Europe. Ozone at Aspendale (38°S), 300 km north of Cape
Grim, shows a late summer-autumn maximum and a winter
minimum, with a much smaller seasonal amplitude than is
found at northern mid-latitudes. It is known that ozone at
Aspendale is influenced by proximity to the city of Melbourne
[Galbally, 1971].
There appears to have been a significant change in the sea-
sonal cycle of ozone in Europe over the past 30 years. Con-
centrations of ozone at Arosa, Switzerland (1780 m), were
highest in May in the 1950's [Junge, 1962]. Recent measure-
ments from nearby Payerne and from high-altitude stations in
Germany [Reiter and Kantor, 1982] show the characteristic
summer maximum in mid-latitude ozone (see Figure 12). Con-
centrations of ozone in July and August are now similar to
those in May, implying an increase in summertime values in
excess of 10 ppb. Data from East Germany provide further
evidence for a change in the seasonal cycle of ozone. Warmbt
[1979] observed increases in both summer and winter values
for ozone at Arkona (54°N) on the Baltic coast. Ozone con-
centrations in summer increased from 18 ppb in 1956-1960 to
31 ppb in 1973-1977, while winter values increased from 11
ppb to 16 ppb. There is no indication of a further increase in
ozone since 1977 [Feisterand Warmbt, 1984].
Measurements of ozone from the 19th century appear to
indicate a similar change in the seasonal cycle of ozone in the
United States. Ozone was measured on a daily basis in Michi-
gan from 1871 to 1903, using Schoenbein's test paper. The
paper, impregnated with starch, changes color in response to
the reaction of O3 with potassium iodide. Linvill et al, [1980]
calibrated the Schoenbein test results as a function of humidi-
ty by using a Dasibi ozone instrument and presented an
analysis of the Michigan measurements from 1876 to 1880 in
terms of parts per billion ozone (see Figure 13). The Schoen-
bein results are no doubt less reliable than data obtained with
contemporary instrumentation, but the seasonal pattern may
be reliable. It appears that ozone was significantly higher in
spring than in summer in the 1870's in the midwestern United
States, in contrast to results for the present day (compare
Figures 7 and 8 with Figure 13).
We performed trend analyses on ozonesonde data near the
ground, with results shown in Table 3. Sonde data suggest
that ozone increased about 3% yr"1 from 1970 to 1982 at
Hohenpeissenberg, Germany, while surface data suggest a
smaller trend, ~1.5% yr"1. Unfortunately, the sonde data
may be contaminated by SO2, as may surface results prior to
1976 when an SO2 filter was installed [Attmanspacher et al.,
1984]. A negative trend in concentrations of SO2 could mimic
a positive trend in O3. It appears that the sonde data may
exaggerate the magnitude of the trend (Figure 14). Sonde data
indicate that the trend is largest in summer, 1.1 +0.3 ppb
yr"1 (Figure 15). Ozone did not change significantly from
1968 to 1977 at Payerne, Switzerland, on an annual basis, but
summer values increased by 1.7( + 1.3) ppb yr"1. The change
in the time of measurement at Payerne in 1977 precludes accu-
rate assessment of the trend over the entire record. Surface
data from Wallops Island, U. S. A., suggest a slight increase in
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Paper 6
10,472
LOGAN : TROPOSPHERIC OZONE
o
N
O
60
50
[40
L
30
20
10
- SONOE
MIN. ^•• — -
1970 72 74
76
YEAB
78 1980 82
84
Fig. 14. Annual mean values of surface ozone at Hohenpeissen-
berg. The solid line shows sonde measurements at 900 mbar made at
~0800. The long dashed line (mean) shows daily average con-
centrations of ozone measured with surface instruments. Results were
taken from Attmanspacher and Hartmannsgruber [1980] for 1971-
1975 and from Ozone Data for the World for 1976-1983. Annual
means of monthly daily maxima (max) and minima (min) are also
shown.
ozone during the 1970s', but the trend is not statistically sig-
nificant; neither is the decrease in ozone at Goose Bay,
Canada, once the bias introduced by the trend in the correc-
tion factor is removed. It is noteworthy that increases in ozone
are found only at stations that show a prolonged summer
maximum in the seasonal distribution.
There is no significant trend in ozone at locations that ex-
hibit a summer minimum: Resolute and Goose Bay in Canada
(see Table 3); Barrow, Alaska; and the Pacific islands of
Hawaii and Samoa [Oltmans, 1981, 1984].
4.1.2. Ozone in the middle troposphere. The seasonal vari-
ation of tropospheric ozone at middle and high latitudes of
the northern hemisphere is shown in Figure 16. Results for
stations in Europe, the United States, and Japan at latitudes
38°-42° and 43°-48° are shown as composite profiles, as are
results for Canada at 53°-59°. The variance of monthly mean
values between stations in each group is similar to the vari-
ance in the monthly mean at an individual station.
A broad summer maximum is found at 700 mbar over
Europe, the United States, and northern Japan, while a late
spring maximum is found over Canada. The patterns are simi-
lar to those observed at ground level. The seasonal maximum
extends from April to August at 48°-53° in Europe but occurs
between March and June at 53° in Canada, indicating a longi-
tudinal gradient in ozone at these latitudes. Ozone con-
centrations in summer over the United States and Europe
appear to exceed those over Canada by 5-15 ppb, or between
10% and 40%. The difference in the seasonal cycle of ozone
HOHENPEISSENBERG (1/70-12/83)
WIN.
SPR
SUM
AUT.
Fig. 15. Trend in ozone in each season at 900 mbar at Hohen-
peissenberg (January 1970 to December 1983) derived from ozone-
sonde data. The horizontal bars give the trend in parts per billion per
year, and the vertical bars give the 90% confidence interval for the
trend.
300
26O
220
180
14O
100
60
20
1 70
ui 60-
O
g 50
40
30
60
50
40
30!
I I I i I I I
JF
MAMJJASO
MONTH
ND
Fig. 16. The seasonal distribution of tropospheric ozone at
middle and high latitudes. The solid line (75°) shows results for Re-
solute; the long dashed line (55°) is an average of monthly mean
values for Goose Bay, Edmonton, and Churchill; the short dashed
line (45°) is an average for Bedford. Sapporo, Biscarosse, Payerne, and
Hohenpeissenberg, and the vertical bars show the standard deviation
of the five mean values; the dotted line (38°) is an average for Wallops
Island. Caglian. and Boulder. Results are shown for 300 mbar
(upper), 500 mbar (center), and 700 mbar (lower).
over the two regions is less pronounced at 500 mbar than at
700 mbar.
Data from Florida and the Bahamas [Chatfield and Harris-
on, 1977b] indicate that the summer maximum in ozone at
500 mbar extends as far south as 21°N in the western hemi-
sphere. The summer maximum is not found at lower latitudes
over Japan, as shown in Figure 17. Ozone decreases dramati-
cally in early summer over Kagoshima (32°N), and results for
Tateno at 36° also indicate the onset of a summer decrease.
The decrease appears to be related to seasonal changes in
circulation, as discussed below.
Maximum concentrations of ozone occur between March
and May at 300 mbar, earlier than in the middle troposphere
(Figure 16). The seasonal pattern in the upper troposphere
resembles that for ozone in the lower stratosphere. Ozone at
300 mbar shows a steep gradient with latitude which also
resembles that for stratospheric ozone, with largest con-
centrations at high latitudes. This may reflect, in part, the
frequency of sampling stratospheric air at 300 mbar, which
increases at higher latitudes [Reiter, 1975].
The distribution of ozone with latitude in the middle tropo-
sphere is very different from that in the upper troposphere-
I
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Paper 6
LOGAN: TROPOSPHERIC OZONE
10.473
60
5O
40-
30-
20-
160
120-
80-
40
80
-70-
-eoh *V1
i
3 50
40
300mb -
700mb -
i i i i i i i i i i i i
JFMAMJJASONO
MONTH
Fig. 17. The seasonal distribution of tropospheric ozone over
Japan. Results are shown for Sapporo (43°), Tateno (36°), and Kago-
shima (32°). Almost no measurements were made in July and August
at Tateno.
lower stratosphere region. Largest concentrations are found at
mid-latitudes in the northern hemisphere, between 30° and
50°, as shown in Figures 18-20. The mid-latitude maximum is
present in all seasons at 700 mbar, but only in spring and
summer at 500 mbar. Figures 18 and 19 give mean con-
centrations of ozone at sonde stations in January, April, July,
and October at 700 mbar and 500 mbar, with supplementary
results for August in Figure 20. The solid line indicates a 5°
moving average for 20°N to 60°N, while the dashed lines show
snapshots of the latitudinal distribution obtained by aircraft
sampling.
There is little evidence for a latitudinal gradient in ozone at
middle and high latitudes of the southern hemisphere, except
in summer (January), but the data are very sparse. Interhemi-
spheric differences at mid-latitudes are shown more clearly in
Figure 21. The amplitude of the seasonal cycle in the middle
troposphere at 38°S (Aspendale) is much smaller than that at
38°^40°N, as noted previously by Pittock [1977] and by Fish-
man et al. [19796], and concentrations are largest in spring in
the south in contrast to the broad summer maximum in the
north. There is a significant hemispheric asymmetry in the
seasonal cycle of ozone at high latitudes also (see Figure 22).
Ozone at 700 mbar and 500 mbar is largest in winter and
smallest in summer at Syowa (69°S), in agreement with earlier
results from Antarctica [Wisse and Meerburg, 1969], while
ozone is largest in late spring and early summer at Resolute
(75°N). There is a summer minimum near the surface in both
hemispheres.
Data from sonde stations indicate that tropospheric ozone
may be increasing in the northern hemisphere. Angell and Kor-
shover [1983] reported an average increase of ~ 12% from
1970 to 1981 at mid-latitudes; Bojkov and Reinsel [1984] re-
ported similar results. We find that the evidence for an in-
crease in ozone at 700-500 mbar is strongest for Europe
(~2% yr~' over Hohenpeissenberg, with somewhat smaller
increases over Payerne and Uccle) as shown in Table 4. The
trends calculated for North America (Wallops Island and
Goose Bay) are positive, once the bias introduced by the trend
in the correction factor is removed, but are not statistically
significant. The trend derived for Wallops Island is significant,
0.9( ± 0.6)% per year, only if outliers are first removed from
the data record (see Table 4). Angell and ICorshover found a
larger trend over North America than over Europe. Their
analysis included measurements with Brewer Mast and ECC
sondes at the Canadian stations and from two times of day at
Payerne. These changes in measurement strategy may have
introduced inconsistencies in the data they analyzed, as dis-
cussed earlier.
Measurements from Resolute indicate that ozone in the
middle troposphere is increasing at high northern latitudes
also, by ~1% yr"'. The trend is much larger in spring and
summer (~1 ppb yr~l) than in other seasons, as shown in
Figure 23. There is less seasonal variability in the magnitude
of the trend at mid-latitudes, as shown by results for Hohen-
peissenberg.
The altitude dependence of the trend in ozone is quite dif-
ferent at locations with a summer maximum in ozone com-
pared to those with a summer minimum. Hohenpeissenberg
700mb
so
40
20
0
I 60
T - I I 1 T-S—
- OCTOBER
•
juLy
9 «f- i •
2
u SO
§
a
0
40
20
-
. 4*WL
- JANUARY
1 _ 1 1 1 _) 1_ L J
L J
L ' ' J
. r '., * "' •' ^
-t
I
• a J
: s°-^f^**m -i
u • _:
- 3 _j
»-""
-
a a
__J L- L . — _J J 1
JO 70
50 40 30 20 10 0 10 20 30 W 50 60 TO 80
SH LATITUDE N-H
Fig. 18. The distribution of ozone with latitude at 700 mbar. The
symbols show monthly mean concentrations for the stations listed in
Table 1. The symbols are denned as follows: (solid squares) North
America, BM sondes: (open squares) North American Ozonesonde
Network, BM [Chatfield and Harrison, 1977]; (half-rilled squarel
Americas, ECC; (solid circle) Europe; (open circle) Lmdenberg; (trian-
gle) India; (diamond) Japan: (hexagon) Hawaii [Oltmans. 1981]; (plus)
Australia and the Antarctic, including surface data from the South
Pole from Oltmans [1981]. Seasonal values are shown for tropical
locations (crosses) if they are somewhat different from midseason
values because of the small number of tropical measurements. The
plus at 2°S shows ECC measurements made at Canton Island (four
profiles) in December [Kohmyr and Sticksel, 1967]. The solid line is a
5° moving average of sonde results for 20"N to 60°N.
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Paper 6
10,474
LOGAN: TROPOSPHERIC OZONE
,.i OCTOBER
T . ,\ ,
20-
ffl-
';
SOOmb
,-, < ,
JULY
10. APRIL
20-
JANUARY
» 70
10 20
30 40
HH
so so ro K
60 50 « 30 20 10 0
S.M LATITUDE
Fig. 19. The distribution of ozone with latitude at 500 mbar.
Symbols are denned in Figure 18. The panel for Apnl shows aircraft
data from Routhier et al. [1980] for the central Pacific south of 40°N
and for North America north of 40°N for April and May (dashed
lines). The panel for October shows aircraft data from Gregory et al.
[1984] for a flight from Wallops Island to the west coast of South
America. Southbound data are given by the dot-dashed line, north-
bound data by the dashed line.
(summer maximum) shows the largest increase at the surface
and smaller increases at 700 mbar and 500 mbar. Resolute
(summer minimum) shows no trend at the surface but a signifi-
cant increase at 700 mbar and 500 mbar (see Figure 24). Both
locations show a switch over from a positive trend in the
middle troposphere to a negative trend in the lower strato-
sphere. This is a feature common to trend results for all the
stations in the northern hemisphere (see appendix). At As-
pendale, the only sonde station at southern mid-latitudes,
there is no significant trend in the middle troposphere, but
there is a decrease in ozone in the lower stratosphere (see
appendix).
The trend in tropospheric ozone contributes significantly to
the trend in the integrated column of ozone. The increase in
the troposphere, at Hohenpeissenberg appears to compensate
for at least 30% of the decrease observed in the stratosphere
over the same period and may be of comparable magnitude to
the decrease in the stratosphere. The increase in tropopheric
ozone at Resolute is about 20% of the decrease in the strato-
sphere (see appendix).
_ w
Is,
Z tn
s
20
n
AUGUST. SOOmb
" '• ^
" * * * ... -
i L *-- ._!_-- ' . __ ' — '
'
'jF*y%**^ ". •"
- .»£'V "" « '•'' \> '
• *
iii.ii — i
SH LATITUDE H H
Fig. 20. The distribution of ozone with latitude at 500 mbar in
August. Symbols are defined as in Figure 18, except that the sonde
data in the southern hemisphere are shown as squares for clarity. The
dashed line shows aircraft data of Routhier et al. [1980] for the route
described in Figure 19. The crosses show the aircraft measurements of
Seller and Fishman [1981] taken over both coasts of North America
and the west coast of South America. The cross-hatched area shows
measurements over central Brazil [Delany et al., 1985; Crutzen et al.,
1984].
120
100
80
60
40
70
~60
>
•o
a
*50
040
O
30
MONTH (N.H.)
JFMAMJJAS 0 N 0
3OOmb
i I i i i i
I i i i i
SONDJFMAMJ
MONTH (S.H.)
Fig. 21. Comparison of ozone at mid-latitudes of the northern
and southern hemispheres. Results are shown for Aspendale, 38°S
(solid), and for stations near 38°N (dashed: see Figure 16) for 300
mbar, 500 mbar, and 700 mbar. The vertical lines show the standard
deviation of the monthly means.
4.2. Ozone in the Tropics
Recent measurements indicate that concentrations of ozone
at Natal, Brazil, are much larger than at other tropical lo-
cations {Kirchhoff et oJ., 1983; Kirchhoff, 1984]. Figure 25
displays annually averaged concentrations of ozone in the
tropics and subtropics (upper panel). The difference between
concentrations at Natal (6°S) and Panama (9°N), ~60%, is
much too large to be ascribed to the differential response of
the ECC and Brewer-Mast sondes to tropospheric ozone,
which could account for a difference of about 15%. There is a
significant seasonal variation in ozone at Natal, with values in
September and October about a factor of 2 higher than in
February to April (Figure 25, lower panel). Ozone at Panama
shows little seasonal variation [Chatfield and Harrison,
19776]. Maximum concentrations in the middle troposphere
at Natal are as large as those found at mid-latitudes in
summer (compare Figures 16 and 25), while minimum con-
centrations correspond to those found all year at Panama.
The results for Natal in Figure 25 suggest that ozone mixing
ratios are almost constant above 600 mbar, but this picture is
somewhat misleading. Inspection of individual vertical profiles
reveals that high levels of ozone are found in layers above the
trade wind inversion, —800 mbar, as shown in Figure 26. A
more detailed analysis of these data and more recent measure-
ments from Natal will be presented elsewhere (V. W. J. H.
Kirchhoff and J. A. Logan, unpublished manuscript, 1985).
Surface data from Sa Da Bandeira, Angola (15°S), display the
same seasonal behavior as ozone at Natal, with a September
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LOGAN: TROPOSPHHUC OZONE
10,475
MONTH (N. H.)
J F M AMJJASOND
RESOLUTE (1/66-10/791
HOHENPBSS EN BERG (1/70- 12/831
70
60
50
4O
30
20
I 50
o.
o.
ui 40
|
O 30
20
>0
30H
20
10
i i i i i i i i i
i i i i i i i i i i
69-S
-1000mb
i i i i i i
JASONDJFMAMJ
MONTH (S.H.)
Fig. 22. Comparison of ozone at high latitudes of the northern
and southern hemispheres. Results are shown for Syowa (69°S, solid)
and Resolute (7S°N, dashed) for 500 mbar, 700 mbar, and ~ 1000
mbar. Surface measurements at the South Pole (90°S, dotted; Oltmans
[1981]) are also included.
-0.4
WIN SPR SUM AUT WIN SPR SUM AUT
Fig. 23. Trend in ozone in each season at Resolute (January 1966
to October 1979) and Hohenpeissenberg (January 1970 to December
1983) at 700 mbar and 500 mbar. The horizontal bars give the trend
in parts per billion per year, and the vertical bars give the 90%
confidence interval for the trend.
maximum [Fabian and Pruchniewicz, 1977], while ozone a?
Samoa (14°S) is largest in July and August [Oltmans, 1981].
The sonde results suggest significant spatial and temporal
inhomogeneities in ozone in the tropics. Recent aircraft
measurements, shown in Figures 19 and 20, provide further
evidence for inhomogeneities, particularly in the southern
tropics. Routhier et al. [1980] found concentrations of about
20-30 ppb at 500 mbar over the Pacific Ocean in May and
August, while Seiler and Fishman [1981] reported similar
values for the west coast of South America in August. These
TABLE 4. Trend in Tropospheric Ozone
Dates
Scaled to
Column
Divided by
Correction
Factor
Trend in
Correction
Factor
700 mbar, 500 mbar
Hohenpeissenberg
Payerne
Uccie
Resolute
Goose Bay
Wallops Island'
Sapporo
Tateno
Kagoshima
Aspendale
Hohenpeissenberg
Goose Bay
Kagoshima
January 1969 to December 1982
August 1968 to January 1977
January 1969 to December 1980
January 1969 to March 1981
January 1966 to August 1979
June 1969 to August 1980
May 1970 to August 1981
January 1969 to December 1982
January 1969 to December 1982
January 1969 to December 1982
June 1965 to April 1982
300 mbar
January 1969 to December 1982
June 1969 to August 1980
January 1969 to December 1982
1.9 ± 0.3
0.9 ± 0.7
I.I ± 0.7'
1.7 ± 0.7»
1.2 ± 0.5
(-0.2 ± 0.7)
(0.6 + 0.8)
0.7 + 0.5
0.7 ± 0.5
1.5 + 1.0
(0.4 ± 0.5)
0.8 ± 0.8
-4.6 + 1.7
(1.3 ± 1.3)
2.2 ± 0.3
(0.7 t 0.8)
—
—
1.1 ±0.5
(0.5 ± 0.7)
(0.4 ± 0.9)
(0.5 ± 0.5)
(0.3 ± 0.5)
1.5 ± 1.1
(-0.4 ±0.4)
1.0 ± 0.8
-3.8+ 1.7
(1.4 ± 1.4)
-0.4 + 0.2
NS
—
—
NS
-0.7 ± 0.3
NS
NS
0.5 ± 0.3
NS
0.6 ± 0.2
-0.4 ± 0.2
-0.7 + 0.3
NS
Trends are given as the percentage change per year and are presented in the same format as Table 2.
Trends were calculated from monthly residuals z(month, year), as described in section 3. Concentrations
at 700 mbar and 500 mbar were averaged before forming monthly means. Results are given for 300 mbar
only if statistically significant.
Trend derived from data provided in tabular form by D. DeMuer. Monthly mean values were
calculated for soundings with correction factors between 0.8 and 1.4, omitting those flagged as being
contaminated in the troposphere.
Trend derived from monthly mean values provided by J. London.
The calculated trend is 0.7 + 0.6 (scaled to the ozone column) and 0.9 ± 0.6 (divided by C.F.) if ozone
values more than 2 standard deviations from the monthly mean are removed from the data set prior to
analysis.
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Paper 6
10,476
LOGAN: TROPOSPHERIC OZONE
RESOLUTE
HOHENPEISSENBERG
10O
100O
2 -2
A OZONE (%yr"
Fig. 24. Vertical distribution of the trend in ozone (in percent per
year) at Resolute and Hohenpeissenberg. The horizontal bars give the
90% confidence interval for the trend at each level. The shaded area
shows the range of tropopause heights through the year.
concentrations are about a factor of 2 lower than results for
Natal on the east coast of Brazil but are similar to results for
Panama. Crutzen et al. [1985] reported values of 40-50 ppb
over central Brazil in August. A recent expedition over the
west coast of South America in October found concentrations
of 35-55 ppb from 5°S to 20°S on the southbound flight, but
concentrations were even higher, 55-80 ppb, on the north-
bound flight only a few days later [Gregory et al., 1984]. The
high values are similar to results for Natal.
Sonde results from Natai (6°S) and Panama (9°N) in combi-
nation with the aircraft measurements indicate that ozone
concentrations in the southern tropics are in some cases much
greater than those of the northern- tropics. The data in Figures
18-20 do not support the previously accepted view [e.g., Fish-
ISOi
OZONE -TROPICS
ANNUAL
200|- MEAN
400-
800
100O
20O-
400-
£ 600-
8OO-
1OOO
40 6O
OZONE (ppbv)
Fig. 25. Average vertical profiles for ozone in the tropics. The
upper panel shows annual mean concentrations of ozone at Panama,
9°N (solid); Grand Turk, 21°N (dashes) [Chatfield and Harrison,
1977fe]; Poona. 19°N (dots); and Natal, 6°S (dot-dash). Surface data
are from Mauna Loa, 19°N (square), and Samoa, 14°S (circle) [Olr-
mans, 1981]. The lower panel shows average concentrations at Natal
(solid) in September and October (11 profiles) and in February-April
(10 profiles). Although few profiles are available for each month, the
seasonal pattern is reproduced in 3 years of data. Horizontal bars
shown one standard deviation based on individual profiles for Natal.
Results are compared with the annual mean profile at Panama
(dashes) and its standard deviation (based on monthly mean values).
200-
400
600
800
1000
25
50 75
OZONE (ppb)
R H (%)
100 125
150
Fig. 26. Vertical profiles of ozone at Natal (6°S). Results are
shown for three consecutive days in October 1979. The figure includes
the vertical distribution of water vapor, shown in terms of relative
humidity, for October 9.
man et al., 19796] that ozone is more abundant in the north-
ern tropics. The analysis by Fishman et al. [1979b] may have
been confounded by instrumental differences. They compared
measurements made with Brewer-Mast sondes at Panama
with results from Regener sondes at Canton Island (2°S) and
LaPaz(10°S).
5. DISCUSSION
Daily average concentrations of surface ozone in summer
are between 30 ppb and 50 ppb in rural areas of the United
States and Europe, while daily maximum concentrations are
between 45 ppb and 65 ppb. We argue here that these con-
centrations are influenced significantly by photochemical pro-
duction of ozone associated with emissions of NO,, hydro-
carbons, and CO, and we present a quantitative assessment of
the magnitude and extent of the anthropogenic influence. The
persistence of high ozone concentrations from spring into
summer occurs only at continental mid-latitudes of the north-
ern hemisphere. Concentrations appear to be largest in the
most densely populated and industrialized regions, the eastern
United States and central Europe. The behavior of ozone is
quite different in sparsely populated regions remote from in-
dustrial activity: for example. Cape Grim and much of
<
ui
100
50
I •
-50|
S-rooL^
JFM
AMJJA
MONTH
SONO
Fig. 27. Seasonal distribution of 90Sr at the surface. Data shown
for Moosonee, Canada 52°N (solid), and for Sterlmg-NYC. 40°N
(dashed) are from Staley [1982].
1
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LOGAN: TROPOSPHERIC OZONE
10.477
HOHENPEISSENBERG, 1/76-13/83
70
60
>
a
§50
940-
30|- /"-SURFACE
20-
SOOmB
700mb
J F M A
S 0 N D
M J J A
MONTH
Fig. 28. Seasonal distribution or ozone at Hohenpeissenberg. The
solid lines show sonde results for 700 mbar and 500 mbar. The
dashed line shows daily mean values, and the dot-dashed line shows
daily maximum values at the surface, derived from continuous surface
measurements. Results are given for 1976 to 1983.
Canada, where ozone is largest in winter or spring and small-
est in summer or autumn (15-25 ppb). The source of ozone
from the stratosphere might be expected to give rise to a late
winter or spring maximum in tropospheric ozone, since
stratosphere-troposphere exchange is most effective during
this period [Danielsen, 1968; Danielsen and Mohnen, 1977;
Mahlman and Moxim, 1978].
The difference in seasonal behavior of surface ozone cannot
be attributed simply to a latitudinal gradient or to differences
between the hemispheres. We emphasize in this context first
the summer maximum in surface ozone at 53°-55°N in
Europe and the late summer-autumn minimum at similar lati-
tudes in Canada. The Canadian sites experience surface air
flow from the north in summer [Bryson and Hare, 1974] and
therefore should represent some of the cleanest continental air
in the northern hemisphere. Second, we note that the seasonal
cycles of 90Sr, a tracer of stratospheric air, are exactly in phase
at 52° and 40° in North America (see Figure 27) [Staley,
1982]. This suggests that the different seasonal cycles of ozone
at these latitudes cannot be ascribed simply to variations in
the source of ozone from the stratosphere. Ozone mixing
ratios in rural areas are too large in any event to be supplied
by downward transport. Daily maximum mixing ratios of
ozone near the ground at Hohenpeissenberg, for example,
exceed values at 700 mbar in spring and summer (Figure 28).
A similar result was found by Reiter and Kanter [1982] at a
nearby location. Maximum ozone concentrations at Garmisch
(740 m) exceeded those on the neighboring Zugspitze peak
(2940 m) by ~ 10 ppb on sunny summer days. Third, we note
the summer-autumn maximum in near-surface ozone at As-
pendale (38°S), in contrast to the summer minimum at Cape
Grim (41°S). Aspendale is affected by urban air pollution
[Galbally, 1971], while Cape Grim is usually under the influ-
ence of pristine marine air masses. Thus nearly all locations
within a few hundred kilometers of anthropogenic sources of
NOj and hydrocarbons exhibit a summer maximum in surface
ozone, while very remote sites exhibit a summer or autumn
minimum. The principal exceptions to this general behavior
are southern coastal sites in the United States near 30°N and
similarly situated Japanese stations. During summer, these lo-
cations experience tropical marine air flow [Bryson and Hare,
1974; Fukui. 1977] characterized by low concentrations of
ozone (see Figures 18 and 19).
There is good evidence for a change in the seasonal distri-
bution of surface ozone in Europe and the United States. This
change implies substantial ozone increases in summer over
regions of continental scale between 1950 and 1975. The avail-
able long-term measurements, from Arkona on the Baltic
coast, show that ozone concentrations in summer increased by
~13 ppb (~70%) from 1958 to 1975, while winter values
increased by ~5 ppb (-45%). Warmbt [1979] noted that
ozone concentrations are highest during years with warm, dry,
sunny summers [see also Attmanspacher et al., 1984; Reiter
and Kanter, 1982]. The measurements from Arosa suggest that
ozone has increased by at least 10 ppb (-35%) in summer
over the same period, and they imply a larger increase in
summer than in other seasons. Measurements from Hohen-
peissenberg for 1970 to 1983 indicate an increase in ozone of
perhaps 6 ppb (20%), also with evidence for a larger change in
summer.
Maximum concentrations of ozone in Michigan occurred in
April and May in the 1870's, the same months as they do
today in Canada (53°-59°N). If we use as preindustrial values
the present-day concentrations of ozone at the relatively
remote sites in Canada (Figure 11), we estimate that daily
average concentrations of ozone in summer have increased by
as much as 6-12 ppb in the Midwest and possibly by as much
as 10-22 ppb in highly impacted environments such as the
Ohio River Valley. These changes correspond to increases of
20% to 100%. Alternatively, if we adopt ozone concentrations
at Cape Grim, Tasmania (15-20 ppb), as representative of the
preindustrial atmosphere, we estimate that average con-
centrations of ozone in summer in the United States and
Europe have increased by 15-25 ppb (see Figure 11), consis-
tent with results discussed above.
Increases in ozone of the magnitude discussed here appear
to be consistent with current understanding of the photochem-
istry of rural air. Oxidation mechanisms for hydrocarbons
(HC) in the presence of NOr indicate that several molecules of
ozone may be formed for each molecule of NOX and HC that
is released [e.g., Isaksen et ai, 1978; Singh et al., 1981], and
field observations of O3, NO.,, and hydrocarbons in rural
areas support this view [Fehsenfeld et al., 1983; Kelly et al.,
1984; Parrish et ai, 1985]. The average emission rate of NOX
from combustion of fossil fuels is ~ 2 x 10" molecules cm ~z
s~l in the eastern United States, about a factor of 10 larger
than the flux from natural sources [Logan, 1983]. Even if only
one molecule of ozone were formed for each molecule of NO,
released, the production rate of ozone in the boundary layer in
this region would exceed the average flux from the strato-
sphere ~5-8 x 10'° molecules cm"2 s"1 [Danielsen and
Mohnen, 1977; Mahlman et al., 1980; Gidel and Shapiro, 1980].
Hence it does not seem unreasonable that ozone con-
centrations might have increased by as much as a factor of 2
as a result of photochemical production associated with emis-
sions of NO, and hydrocarbons.
It is likely that much of the increase in ozone occurred
between 1940 and the mid-1970's, at least in the United States.
Emissions of NO, from combustion increased by a factor of
~3 during this period, while emissions of hydrocarbons in-
creased by a factor of ~2 [U.S. Environmental Protection
Agency, 1982]. Emissions of NO., increased at a slower rate
after 1970 and have decreased since 1979, while emissions of
HC have decreased since 1970, in part as a result of pollution
control measures, in part as a result of energy conservation.
It is more difficult to quantify the possible impact of anthro-
pogenic emissions on concentrations of ozone above the
boundary layer. The similarity between the seasonal cycle of
ozone in the middle troposphere over Europe, the United
States, and northern Japan and that at ground level and the
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Paper 6
10,478
LOGAN: TROPOSPHERIC OZONE
observed increases of ozone in the 1970's in the middle tropo-
sphere certainly argue in favor of a significant anthropogenic
impact. It is extremely difficult to rationalize the persistence of
high concentrations of ozone from April to August at 500
mbar without invoking a photochemical source, largely be-
cause of the short lifetime of ozone at mid-latitudes in
summer, less than 1 month [Isaksen et a/., 1978]. Ozone or its
precursors from the boundary layer are most likely to influ-
ence the distribution of ozone at higher altitudes in summer,
when convective mixing is most effective.
Results from a recent study with a general circulation model
also suggest that a photochemical source is required to ex-
plain the summer maximum [Levy et al., 1985]. The model
allowed for downward transport of ozone from the strato-
sphere and removal at the surface but did not include photo-
chemical production and loss; it reproduced the observed sea-
sonal cycle at remote locations where ozone concentrations
are highest in late winter or spring but failed to simulate the
broad summer maximum at mid-latitudes.
The seasonal behavior of ozone and observed increases sug-
gests that the anthropogenic influence extends from about
30°N to 75°N in the middle troposphere and that the latitudi-
nal extent varies with circulation patterns. For example the
lack of a summer maximum in ozone over southern Japan
(30°N) may be attributed to the onset of the summer monsoon
when airflow from the Asian continent is replaced by air from
the tropical Pacific [Fufcui, 1977]. The increase in ozone over
Resolute (75°N) at 500 mbar in spring and summer may result
from long-range transport of ozone or its precursors from
lower latitudes. Measurements of sulfate and particulates indi-
cate that the Canadian Arctic is most likely to be influenced
by air masses from mid-latitudes between December and May
[Barrie et ai, 1981; Rahn, 1981], and ozone data near the
ground show scant evidence for an anthropogenic impact in
summer. The lifetime of ozone in the middle troposphere is
expected, however, to be longer than that of SO2 and sulfate,
which are removed from the atmosphere by precipitation
scavenging, and hence transport of ozone or its precursors
from mid-latitudes may influence high-latitude ozone at 500
mbar in summer.
The increases in tropospheric ozone implied by the sonde
data are substantial, l%-2% yr"1 between 30°N and 75°N. It
is unfortunate that there are no systematic observations from
the period of most rapid growth in emissions of ozone precur-
sors, 1940-1970. The trends in tropospheric ozone since 1967
contribute significantly to the trends in the integrated column
of ozone and may compensate for 20%-30% of the decrease
in ozone in the stratosphere over middle and high latitudes.
Studies of the influence of tropospheric ozone on climate
have shown that surface temperature is most sensitive to
changes in ozone near the tropopause {Wang et at., 1980],
and the evidence for change in this region is rather weak.
Measurements from only two locations, Hohenpeissenberg
and Kagoshima, suggest an increase in ozone at 300 mbar,
while results for Goose Bay suggest a decrease. However, the
variance of ozone concentrations near the tropopause is much
larger than in the middle troposphere, and derived trends are
less reliable.
Recent observations from Brazil suggest that elevated ozone
concentrations in the tropics may result from photochemical
synthesis, with combustion of vegetation rather than fossil
fuels providing the source of NO,, HC, and CO {Crutzen et
at., 1985]. Concentrations of ozone in the polluted boundary
layer m a region of biomass burning in central Brazil, 60-65
ppb \Delany et al., 1985], and values over Natal in September
and October, > 60 ppb, are similar to concentrations at mid-
latitudes of the northern hemisphere in summer. Biomass
burning takes place during the dry season, which lasts from
June to September to the south and west of Natal [Ratisbona.
1976]. The prevailing winds in spring to the south of Natal are
westerly above ~ 500 mbar, but from the ocean below [Sabral,
1979; Oort, 1983]. High levels of ozone are found above the
trade wind inversion ( — 800 mbar) with much lower con-
centrations below. We speculate that the enhanced con-
centrations of ozone over Natal may be due to transport and
photochemical degradation of emissions from biomass burn-
ing and possibly from biogenic emissions [Crutzen et al.,
1985] in the interior of the continent. Stratospheric intrusions
could contribute also to the ozone enhancements that occur in
the southern spring.
The observations of ozone over Natal in combination with
surface data from Samoa, 14°S [0 It mans. 1981], and Angola,
15°S [Fabian and Pruchniewicz, 1977], indicate a significant
seasonal variation in tropical ozone, with highest con-
centrations in late austral winter or spring. Concentrations of
ozone appear to vary significantly with longitude also (see
Figures 19 and 20). The lifetime of ozone toward photo-
chemical loss is about 2 weeks in the tropics [Liu et al., 1983;
Logan et al., 1981], less than the transit time of air masses
around the globe. It is, perhaps, not surprising therefore that
the distribution of the gas in the tropics should be quite het-
erogeneous. The recent data do not support earlier con-
clusions [e.g., Fabian and Pruchniewicz, 1977; Fishman et al.,
19796] that ozone is more abundant in the northern tropics
than in the south and more abundant at northern mid-
latitudes than in the tropics. It is clear that latitudinal gradi-
ents in ozone vary significantly with season and with lon-
gitude.
Evidence presented here suggests that concentrations of
ozone at middle and high latitudes of the northern hemisphere
have been influenced significantly by photochemical pro-
duction associated with emissions of NO,, hydrocarbons, and
CO from combustion of fossil fuels. Ozone over the tropical
continents may also be influenced by emissions from combus-
tion, in this case from agricultural burning. At present the
seasonal behavior of tropospheric ozone is reasonably well
characterized only over continental mid-latitudes of the north-
ern hemisphere. Long-term measurements are sparse, even for
Europe and North America. Data for ozone are particularly
lacking for the tropics and subtropics. Given the central role
of ozone in tropospheric chemistry, it is clear that a concerted
effort should be made to determine the global climatology of
ozone by establishing a network of suitably placed measure-
ment stations. A serious commitment should also be made to
measure ozone on a long-term basis with well-calibrated in-
struments at selected locations. Measurements of species that
affect ozone, such as NOX, hydrocarbons, and CO, are needed
also in order to improve our understanding of the role of
photochemistry in determining the distribution of ozone. It
will be necessary, in addition, to develop rather sophisticated
models for chemistry and dyamics in order to test our con-
cepts about the processes influencing ozone and to evaluate
future effects on tropospheric ozone of combustion related
emissions. Such models must allow for the transformation and
transport of pollutants from urban source regions (or from
regions of agricultural burning) to the middle troposphere and
must adequately simulate intrusions of stratospheric air and
removal of ozone at the surface over varied terrain.
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LOGAN : TROPOSPHERIC OZONE
10.479
2 -2
AOZONE (%yr''l
-202
Fig. Al. Vertical distribution of the trend in ozone (in percent per
year) at Hohenpeissenberg, Payerne, and Resolute. The solid lines
show results for ozone soundings that have been scaled to Dobson
measurements of the ozone column. The dashed lines show results
that have not been scaled; concentrations were divided by the correc-
tion factor before forming monthly means. The horizontal bars give
90% confidence intervals for the trend. Meaningful trends could not
be calculated for the troposphere at Payerne because of changes in
the time of measurement (see Figure 5).
APPENDIX: THE CONTRIBUTION OF THE TREND IN
TROPOSPHERIC OZONE TO THE TREND IN THE OZONE
COLUMN
The sonde data permit an evaluation of the contribution of
the trend in tropospheric ozone to the trend in the ozone
column at those locations where the trends are statistically
significant throughout the troposphere and stratosphere. This
condition is met most closely at Hohenpeissenberg and Re-
solute (see Figure Al). Trends in ozone integrated through the
troposphere and stratosphere are given in Table Al in terms
of Dobson units. The trend in the ozone column derived from
the sonde data is in excellent agreement with the trend derived
from concurrent Dobson measurements, but this is not sur-
prising, since the sonde concentrations are normalized to the
Dobson data. The increase in the column of ozone in the
troposphere is about 20% of the decrease in the column in the
stratosphere at Resolute. The results for Hohenpeissenberg are
more difficult to interpret. The increase in ozone in the tropo-
sphere is ~ 30% of the decrease in the stratosphere, based on
sonde data that have been scaled to the Dobson measurement
of the ozone column, but the increase and decrease are of
equal magnitude if the conventional scaling procedure is not
used. This discrepancy arises because there is a significant
trend in the correction factor at Hohenpeissenberg, —0.4%
yr~', of comparable magnitude to the trend in stratospheric
ozone (see Tables Al and A2 and Figure Al). We note that
the trend in the ozone column derived from Dobson data at
Hohenpeissenberg, -0.28% yr"', does not agree with the
average trend in the ozone column over Europe for 1970-
1981, 0.1 ± 0.27% in 12 years. The average trend was derived
by Angell and Korshover [1983] from 13 Dobson stations. The
sonde data that have not been scaled to the Dobson results
give no change in the ozone column, in better agreement with
the average result for Europe. If the unsealed data provided a
better measure of the trend in ozone at Hohenpeissenberg, this
could imply that the increase in tropospheric ozone is of simi-
lar magnitude to the decrease in stratospheric ozone over
Europe.
The results in Table Al and Figure Al highlight one of the
major difficulties with interpretation of long-term ozonesonde
measurements. The procedure of normalizing sonde results to
Dobson measurements may introduce a significant bias into
TABLE Al. Trends in Ozone in the Stratosphere and Troposphere
Hohenpeissenberg,
January 1969 to
December 1982, D.U. yr
Payerne,
January 1969 to
January 1981, D.U. yr"1
Resolute,
January 1966 to
August 1970, D.U. yr'
AO3,
A03,
A03,
AO3,
Trend
Sonde
troposphere
stratosphere
total-
Dobson
column
Scaled
to
Column
+0.4
-1.5
-I.I
-0.9 + 0.5
Divided by
Correction
Factor
+ 0.5
-0.5
0.0
Scaled
to
Column
-0.9
-0.8 + 0.5
Divided by
Correction
Factor
-0.7
Scaled
to
Column
+ 0.2
-1.0
-0.9
(-0.6+ 1.0)
Divided by
Correction
Factor
+0.2
-1.3
-1.1
Ozone Column
Dobson Units
Dobson Units
Dobson Units
Sonde
O3, troposphere
O3, stratosphere
O3, total"
Dobson
O3, column
26
284
310
339
24
281
305
335
19
360
379
392
The upper portion of the table gives trends in ozone derived from ozonesonde measurements and from
Dobson measurements made on the same day. Integrated trends in the stratosphere and troposphere
were obtained from trend results for the standard pressure levels (see Figure Al) and are given in
Dobson units per year (one D.U. = 2.69 x 10" molecules cm"2). The left-hand columns give results
from sonde data that have been scaled to the Dobson measurements of the column; the right-hand
columns give results from data that have not been scaled in this manner (see Table 3 footnotes). The
lower portion of the table shows the integrated amount of ozone recorded by the sondes and by the
Dobson instruments.
"Column of ozone below 10 mbar.
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Paper 6
10,480
LOGAN: TROPOSPHERIC OZONE
TABLE A2. Trend in Stratospheric Ozone, 100-50 mbar
Hohenpeisscnberg
Payerne (January 1969 to December 1981)
Uccle (January 1969 to March 1981)
Resolute
Goose Bay (June 1969 to December 1982)
Wallops Island (May 1970 to August 1981)
Sapporo
Tateno
Kagoshima
Aspendale (January 1969 to April 1982)
Scaled to
Column
-0.7 ± 0.3
-0.5 ± 0.3
-0.4 + 0.4
-0.7 ± 0.3
-0.5 ± 0.3
NS
NS
- 1.2 ± 0.5
NS
-0.5 ± 0.4
Divided by
Correction
Factor
-0.4 + 0.3
-0.4 + 0.4
NS
NS
- 1.6 + 0.5
NS
- 1.1 ± 0.4
Trend in
Correction
Factor
-0.4 ± 0.2
NS
a
b
NS
NS
0.5 + 0.3
NS
0.8 ± 0.3
Trend in
Column
-0.28 + 0.15
-0.23 ± 0.14
-0.35 ± 0.24
-0.20 ± 0.18
NS
NS
NS
0.36 ± 0.21
NS
Trends are given as the percentage change per year for average concentrations at 100,70, and 50 mbar.
Trends were calculated as described in section 3 and are presented in the same format as Table 2. Results
are given for January 1969 to December 1982, unless otherwise indicated. The trend in the ozone column
was calculated from Dobson measurements made on the same days as the ozone soundings.
The trend in the correction factor for January 1969 to January 1979 was 0.5(±0.3)% per year. The
change from Brewer-Mast to ECC sondes in 1979 precludes meaningful interpretation of the trend in the
C.F. thereafter.
The trend in the C.F. for June 1969 to August 1980 was -0.7(±0.3)% per year. ECC sondes were
used after August 1980.
trend results. There are trends in the normalization factors of
similar magnitude to the trends derived for ozone in the lower
stratosphere at over half the ozonesonde stations, as shown in
Table A2. The problem seems to be less serious for the tropo-
sphere simply because the derived trends in ozone are much
larger. These difficulties arise because the sonde technique, in
its present form of implementation, does not provide ad-
equately well-calibrated or internally self-consistent measure-
ments of the concentration of ozone (see section 3).
Acknowledgments. This analysis would not have been possible
without the dedicated efforts of the research groups who initiated and
maintained the long-term measurement programs that formed the
basis for this study. To them I extend my sincere appreciation. I am
indebted to S. C. Wofsy for many enlightening discussions and would
like to thank him and M. B. McElroy for their constructive comments
on this paper. Special thanks are due to R. Yevich and C. S. Spiva-
kovsky for their invaluable assistance with analysis of the ozonesonde
data. I would like to acknowledge useful discussions with H. Levy II
and I. Galbally and to thank R. Angle, D. DeMuer, G. Evans, I.
Galbally, V. Kirchhoff. and V. Mohnen for kindly providing unpub-
lished measurements of ozone. L. Morrison of Atmospheric Environ-
ment Service was most cooperative in supplying computer tapes of
the sonde data. R. Bojkov brought to my attention the change in the
time of measurements at Payerne. Finally, I would like to thank C.
Demore for her expert editorial assistance and M. Burrell for her
patience and skill in drafting the many figures. This work was sup-
ported by NSF grant ATM-81-17009, NASA grant NSG-2031 and
CRC contract CAPA-22-83 to Harvard University.
REFERENCES
Angell, J. K., and J. Korshover, Global variation in total ozone and
layer mean ozone: An update through 1981, J. Climate Appl. Me-
teorol., 22, 1611-1626, 1983.
Attmanspacher, W., and H. U. Dutsch, International ozonesonde
intercomparison at the Observatory Hohenpeissenberg, January 19
to February 5, 1970, Ber. Dtsch. Wetterdienstes, 76(120), 1970.
Attmanspacher, W., and H. U. Dutsch, Second international ozone-
sonde intercomparison at the Observatory Hohenpeissenberg, Apnl
5-20 1978, Ber. Dtsch. Wetterdienstes, 157, 1981.
Attmanspacher. W., and R. Hartmannsgruber, Some results of 6 years
(1967-1972) of regular ozone soundings at the Meteorological Ob-
servatory Hohenpeissenberg, FRG, Contnb. Atmos. Phys., 49,
18-33, 1976.
Attmanspacher, W., and R. Hartmannsgruber, Trend and extreme
value of 8 years continuous measurements of ozone near the surface
at the Meteorological Observatory Hohenpeissenberg, FRG, in Pro-
ceedings of the Quadrennial International Ozone Symposium, 4—9
August, 1980, Boulder, Colorado, National Center for Atmospheric
Research, Boulder, Colo., 1980.
Attmanspacher, W., and R. Hartmannsgruber, Intercomparison of in-
struments measuring ozone near the ground at the Hohenpeissen-
• berg Observatory, October 1, 1978 to April 30, 1979, Ber. Dtsch.
Wetterdienstes, 161. 1981
Attmanspacher, W., R. Hartmannsgruber, and P. Lang, Long period
tendencies of atmospheric ozone based on ozone measurements
started in 1967 at the Hohenpeissenberg Meteorological Observa-
tory, Meteorol. Rundsch., 37, 193-199, 1984.
Barnes, R. A, A. R. Bandy, and A. L. Torres, Electrochemical con-
centration cell ozonesonde accuracy and precision, J. Geophys.
Res^ 90(D5), 7881-7888,1985.
Barrie, L. A., R. M. Hoff. and S. M. Daggupaty, The influence of
mid-latitudinal pollution sources on haze in the Canadian Arctic,
Atmos. Environ., 15, 1407-1419, 1981.
Blumenthal, D. L., W. S. Keifer, and J. A. McDonald, Aircraft
measurements of pollutants and meteorological parameters during
the Sulphate Regional Experiment Program (SURE): Meteorologi-
cal Research, Inc., Rep. EA-1909. Electr. Power Res. Inst., Palo
Alto, Calif, 1981.
Bojkov, R. D., Tropospheric ozone, its changes and possible radiative
effects. Spec. Environ. Rep. 16, World Meteorol. Org., Geneva, 1984.
Bojkov, R. D., and G. C. Reinsel, Trends m tropospheric ozone con-
centrations. Proceedings of the Quadrennial Ozone Symposium,
Greece, September 3-7, 1984, edited by C. S. Zerefos and A. Ghazi.
D. Reidel, Hingham. Mass.. 1984.
Brewer, A. W., and J. R. Milford, The Oxford-Kew ozone sonde,
Proc. R. Soc., A2S6, 470-495, 1960.
Bryson, R. A., and F. K. Hare, The climates of North America, in
World Survey of Climatology, vol. //, chap. 1, edited by R. A.
Bryson and F. K. Hare, Elsevier, New York, 1974.
Chameides, W. L., and A. Tan, The two-dimensional "diagnostic
model for tropospheric OH: An uncertainty analysis, J. Geophys.
Res., 86, 5209-5223, 1981.
Chameides, W., and J. C. G. Walker, A photochemical theory of
tropospheric ozone, J. Geophys. Res., 78, 8751, 1973.
Chatfield, R.. and H. Harrison. Tropospheric ozone, 1, Evidence for
higher background values, J. Geophys. Res., 82, 5965-5968, 1977
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I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Paper 6
LOGAN: TROPOSPHERIC OZONE
10.481
various NO2 sources on tropospheric ozone, J. Geophys. Res., SS,
6641-6661,1983.
Crutzen, P. J., A. C. Delaney, J. Greenberg, P. Haagenson, L. Heidt,
R. Lueb, W. Pollock, W. Seiler, A. Wartburg, and P. Zimmerman,
Tropospheric chemical composition measurements in Brazil during
the dry season, J. Atmos. Chem* 2,233-256, 198S.
Danieisen, E. F.. Stratosphere-troposphere exchange based on radio-
activity, ozone and potential vorticity, J. Atmos. Sci. 25, 502-518,
1968.
Danieisen, E. F., and V. Mohnen, Project Ouststorm: Ozone trans-
port in situ measurements, and meteorological analysis of tropo-
pause folding, J. Geophys. Res* 82, 5867-5877,1977.
Decker, C. E., L. A. Ripperton, J. J. B. Worth, F. M. Vukovich, W. D.
Bach. J. B. TommerdahL F. Smith, D. E. Wagoner, Formation and
transport of oxidants along Gulf Coast and in northern U. S., Rep.
EPA-450/3-76-033, U.S. Environ. Prot. Agency, Research Triangle
Park, N. C, 1976.
Delany, A. C, P. J. Crutzen, P. Haagenson, S. Walters, and A. F.
Wartburg, Photochemically produced ozone in the emissions from
large-scale tropical vegetation fires, /. Geophys, Res* 90, 2425-2429,
1985.
DeMuer, D.. Vertical ozone distribution over Uccle, Belgium, from
six years of soundings, Contrib. Atmos. Phys., 49, 1-16, 1976.
Dutsch, H. U., Two years of regular ozone soundings over Boulder,
Tech. Note. 10, Natl. Center Atmos. Res., Boulder, Colo., 1966.
Dutsch, H. U., The ozone distribution in the atmosphere. Can. J.
Chem.. 52, 1491-1504, 1974.
Dutsch, H. U., Vertical ozone distribution on a global scale, Pure
Appl. Geophys* 116, 512-529.1978.
Dutsch, H. U., and C. C. Ling, Six years of regular ozone soundings
over Switzerland. Pure Appl. Geophys* 106-108, 1151-1168, 1973.
Dutsch, H. U., W. Zuiig, and C. C. Ling, Regular ozone observations
at Thalwill, Switzerland and at Boulder, Colordao, Rep. LAPETH
1, Lab. Atmospharenphys. Eidgcnoss, Tech. Hochsch, Zurich,
1970.
Evans, G., P. Finkelstein, B. Martin, N. Possiel. and M. Graves,
Ozone measurements from a network of remote sites, J. Air Pollut.
Concr. Assoc* 33,291-296,1983.
Fabian, P., and P. G. Prucnniewicz, Meridional distribution of ozone
in the troposphere and its seasonal variation, J. Geophys. Res., 82,
2063-2073, 1977.
Fehsenfeld, F. C, M. J. Bellinger, S. C. Liu, D. D. Parrish, M. McFar-
land, M. Trainer, D. Kley, P. C. Murphy, and D. L. Albritton, A
study of ozone in the Colordao mountains, J. Atmos. Chem., I,
87-105, 1983.
Feister, U., and W. Warmbt, Long term surface ozone increase at
Arkona, Proceedings of Quadrennial Ozone Symposium, Greece, Sep-
tember 3-7, 1984, edited by C. S. Zerefos and A. Ghazi, D. Reidel,
Hingham, Mass., 1984.
Fishman, J., and P. J. Crutzen, The origin of ozone in the tropo-
sphere. Nature, 274, 855-857, 1978.
Fishman, J.. and W. Seiler, Correlative nature of ozone and carbon
monoxide in the troposphere: Implications for the tropospheric
ozone budget, J. Geophys. Res., 88, 3662-3670, 1983.
Fishman, J., V. Ramanathan, P. J. Crutzen, and S. C. Liu, Tropo-
spheric ozone and climate. Nature, 282, 818-820, 1979o.
Fishman, J., S. Solomon, and P. 1. Crutzen, Observational and theo-
retical evidence in support of a significant in-situ photochemical
source of tropospheric ozone, Teilus, 31, 432-446, 1979ft.
Fukui. E. (Ed.), The Climate of Japan. Elsevier, New York, 1977.
Galbally, I. E., Surface ozone observations at Aspendale, Victoria,
1964-1970, Atmos. Environ., 5, 15-25, 1971.
Georgii, H.-W.. and F. X. Meixner, Measurement of the tropospheric
and stratospheric SO2 distribution, J. Geophys. Res., 85, 7433-7438,
1980.
Geraci. M. J., and J. K. Luers, An evaluation of electrochemical con-
centration cell sonde measurements of atmospheric ozone, J. Appl.
Meteorot.. 17, 1521-1527, 1978.
Gidel, L. T., and M. A. Shapiro, General circulation model estimates
of the net vertical flux of ozone in the lower stratosphere and the
implications for the troposphenc ozone budget, J. Geophys. Res.,
85, 4049-4058, 1980.
Gregory, G. L., S. M. Beck, and J. A. Williams, Measurements of free
troposphenc ozone: An aircraft survey from 44°N to 46°S latitude,
J. Geophys. Res., 89, 9642-9648, 1984.
Guichent. R., and H. Van Dop. Photochemical production of ozone
in Western Europe (1971-1978) and its relation to meteorology,
Atmos. Environ.. 11. 145-155, 1977.
Heck, W. W., O. C. Taylor, R. Adams. G. Bingham, J. Miller, E.
Preston, and L. Weinstein, Assessment of crop loss from ozone, J.
Air Pollut. Contr. Assoc., 32, 353-361, 1982.
Hering, W. S., and T. R. Borden, Ozonesonde Observations Over
North America, vol. 4, Environ. Res. Pap. 279, AFCRL-64-30(lVj,
Air Force Cambridge Res. Lab., Cambridge, Mass., 1967.
Hilsenrath, E., et al.. Results from the balloon ozone intercompanson
campaign (BOIC), in Proceedings of the Quadrennial Ozone Sympo-
sium, Greece, 3-7, September 1984, edited by C. S. Zerefos and A.
Ghazi, D. Reidel, Hingham, Mass., 1984.
Isaksen, I. S. A., O. Hov, and E. Hesstvelt, Ozone generation over
rural areas. Environ. Sci. Technol., 12, 1279-1284, 1978.
Junge, C. E., Global ozone budget and exchange between strato-
sphere and troposphere, Teilus, 14, 363-377,1962.
Junge, C. £„ and G. Czeplak, Some aspects of the seasonal variation
of carbon dioxide and ozone, Teilus. 20,422-434, 1968.
Katz, M., Methods of Air Sampling and Analysis, edited by M. Katz,
pp. 549-555, American Public Health Association, Washington, D.
C., 1977.
Kelly, N. A., G. T. Wolff, M. A. Ferman, Sources and sinks of ozone
in rural areas, Atmos. Environ., 18, 1251-1266. 1984.
Kirchhoff, V. W. J. H.. Are northern hemisphere tropospheric ozone
densities larger?, Eos Trans. AGU, 65, 449-^J50, 1984.
Kirchhoff, V. W. J. H., E. Hilsenrath, A. G. Motta, Y. Sahai, and R. A.
Medrano, Equatorial ozone characteristics as measured at Natal, J.
Geophys. Res., 88,6812-6818, 1983.
Kohmyr, W. D., Electrochemical concentration cells for gas analysis.
Ann. Geophys., 25,203-210, 1969.
Kohmyr, W. D., and T. B. Harris. Development of an ECC ozone-
sonde. NOAA Tech. Rep. ERL 200-APCU8, U.S. Dep. Commer..
Boulder, Colo., 1971.
Kohmyr, W. D., and P. R. Sticksel, Ozonesonde Observations 1962-
1966, vol. 1, ESSA Tech. Rep. 1ER 51-IAS 1, U.S. Dep. Commer,
Boulder, Colo, 1967.
Levy, H., II, Normal atmosphere: Large radical and formaldehyde
concentrations predicted, Science, 173, 141-143, 1971.
Levy, H.. II, J. D. Mahlman, W. J. Moxim, and S. C. Liu, Tropo-
spheric ozone: The role of transport, J. Geophys. Res., 90, 3753-
3772, 1985.
Linvill, D. E, W. J. Hooker, and B. Olson, Ozone in Michigan's
environment 1876-1880, Man. Weather Rev* 108, 1883-1891, 1980.
Liu, S. C, M. McFarland, D. Kley, O. Zafiriou. and B. J. Huebert,
Tropospheric NO, and O, budgets in the Equatorial Pacific, J.
Geophys. Res., 88, 1360-1368. 1983.
Logan, J. A., Nitrogen oxides in the troposphere: Global and regional
budgets, J. Geophys. Res., 88, 10,785-10,807, 1983.
Logan. J. A., M. J. Prather, S. C. Wofsy, and M. B. McElroy, Tropo-
sphenc chemistry: A global perspective, J. Geophys. Res., 86, 7210-
7254, 1981.
London, J., and J. K. Angell, The observed distribution of ozone and
its variations. Stratospheric Ozone and Man, vol. 1, edited by F. A.
Bauer and R. B. Ward, pp. 7-42, CRC Press, Boca Raton, Fla.,
1982.
Mahlman, J. D., and W. J. Moxim, Tracer simulation using a global
general circulation model: Results from a mid-latitude instanta-
neous source expenment. J. Atmos. Sci., 35, 1340-1374, 1978.
Mattana. N., G. P. Porra, and A. Serra, Cinq annees de sondages
ozone sur CagJian (Sardaigne). Pure Appl. Geophvs.. 106-108, 1169-
1179, 1973.
Mohnen, V. A., A. Hogan, and P. Coffey, Ozone measurements in
rural areas, J. Geophys. Res.. 82. 5889-5895, 1977.
Mueller. P. K.. and G. M. Hidy, The sulfate regional expenment:
Report of findings, Rep. 1901 (3 vols.), Electr. Power Res. Inst., Palo
Alto, Calif.. 1983.
Mukammal, E., Report on Oxidant Climatology of Ontario. Atmos.
Environ. Serv., Toronto, Canada. 1984.
Oltmans, S. J., Surface ozone measurements in clean air. J. Geophys.
Res.,86, 1174-1180, 1981.
Oltmans, S. J., Troposphenc ozone at four remote observatories. Pro-
ceedings of the Quadrennial Ozone Symposium, Greece. 3-7 Septem-
ber, 1984, edited by C. S. Zerefos and A. Ghazi, D. Reidel. Hing-
ham. Mass., 1984.
Oort, A. H., Global atmospheric circulation statistics. 1958-1973,
NOAA Prof. Pap. 14, 1983.
Parrish, D. D., D. W. Fancy, E. J. Williams. S. C. Liu. M. Trainer, P.
C. Murphy, D. L. Albritton. and F. C. Fehsenfeld. Background
ozone and anthropogenic ozone enhancements at Niwot Ridge,
Colorado, J. Atmos. Chem., in press. 1985.
-------
Paper 6
10,482
LOGAN: TROPOSPHERIC OZONE
Pittock, A. B., Climatology of the vertical distribution of ozone over
Aspendale, Q. J. R. Meteorol. Soc., 103, 575-584, 1977.
Pratt, G. C. R. C. Hendrickson, B. I. Chevone, D. A. Christopherson,
M. V. O'Brien, and S. V. Krupa, Ozone and oxides of nitrogen in
the rural upper midwestern U. S. A., Atmos. Environ^ 17, 2013-
2023, 1983.
Pruchniewicz, P. G., The average tropospheric ozone content and its
variation with season and latitude as a result of the global ozone
circulation, Pure Appl. Geophys^ 106-108,1058-1073,1973.
Rahn, K. A, The Mn/V ratio as a tracer of large scale sources of
pollution aerosol for the Arctic, Atmos. Environ,, IS, 1457-1464,
1981.
Ramanathan, V., and R. E. Dickinson, The role of stratospheric
ozone in the zonal and seasonal radiation energy balance of the
earth troposphere system, J. Atmos. Sci., 36,1084-1104, 1979.
Ratisbona, L. R, The climate of Brazil, in World Survey of Clima-
tology, vol. 12, chap. 5, edited by W. Schwerdtfeger, Elsevier, New
York, 1976.
Regener, E., Ozonschicht und atmospharische turbulenz, Ber. Dxh.
Wetterdienstes, 11,45-57, 1949.
Reiter, E. R., Stratosphenc-tropospheric exchange processes. Rev.
Geophys. Space Phys., 13,459-474,1975.
Reiter, R., and H. J. Kanter, Time behavior of CO2 and O3 in the
lower troposphere based on recordings from neighboring mountain
stations between 0.7 and 3.0 km ASL including the effects of
meteorological parameters. Arch. Meteorol. Geophys. BioUimatol.,
Ser. B, 30, 191-225, 1982.
Routhier, F.. R. Dennett, D. D. Davis, A. Wartburg, P. Haagenson,
and A. C. Delaney, Free tropospheric and boundary-layer airborne
measurements of ozone over the latitude range of 58°S to 70°N, J.
Geophys. *«„ 85, 7307-7321, 1980.
Sabral, Z. R., Um estudo ciimatologico dos campos de vento e de
temperatura nos nivers superiores sobre a America do Sul, M. Sc.
dissertation, Sao Jose dos Campos, Inst. Pesq. Espacais^ Sao dos
Campos, Brazil, 1979.
Schenkel, A., and B. Broder, Interference of some trace gases with
ozone measurements by the KI method, Atmos. Environ., 16, 2187-
2190,1982.
Seller, W., and J. Fishman, The distribution of carbon monoxide and
ozone in the free troposphere, J. Geophys. Res., 86, 7255-7265,
1981.
Shaw, R. W., and R. J. Paur, Measurements of sulfur in gases and
particles during sixteen months in the Ohio River Valley, Atmos.
Environ^ 17, 1431-1438, 1983.
Singh, H. B., F. L. Ludwig, and W. B. Johnson, Tropospheric ozone:
Concentrations and variabilities in clean remote atmospheres,
Atmos. Environ., 12, 2185-2196, 1978.
Singh, H. B, J. R. Martinez, D. G. Hendry, R. J. Jaffe, and W. B.
Johnson, Assessment of the oxidant forming potential of light satu-
rated hydrocarbons in the atmosphere, Environ. Sci. Technol., IS,
113-119,1981.
Skarby, L., and G. Sellden. The effects of ozone on crops and forests,
Ambio, 13, 68-72,1984.
Staley, D. O., Strontium-90 in surface air and the stratosphere: Some
interpretations of the 1963-1975 data, J. Atmos. Sci., 39, 1571-1590,
1981
Torres, A. L., and A. R. Bandy, Performance characteristics of the
electrochemical concentration cell ozonesonde, J. Geophys. Res., 83,
5501-5504, 1978.
U.S. Environmental Protection Agency, National air pollutant emis-
sion estimates, 1940-1980, Rep. EPA-450/4-82-001, Research Trian-
gle Park, N. C, 1982.
Viezee, W., H. B. Singh, and H. Shigeishi, The impact of stratospheric
ozone on tropospheric air quality: Implications from analysis of
existing field data, report, Proj 1140, SRI Int., Menlo Park, Calif.,
1982.
Vukovich, F. M., W. D. Bach,.B. W. Crissman, and W. J. King, On
the relationship between high ozone in the rural surface layer and
high pressure systems, Atmos. Environ., 11, 967-983,1977.
Wang, W-C, J. P. Pinto, and Y. L. Yung, Climatic effects due to
halogenated compounds in the earth's atmosphere, J. Atmos. Sci.,
37, 333-338, 1980.
Warmbt, W., Results of long term measurements of near surface
ozone in the GDR, Z. Meteorol., 29, 24-31,1979.
Wilcox, R. W., Comments on "Tropospheric ozone, 1, Evidence of
higher background values" by R. Chatfield and H. Harrison, J.
Geophys. Res., 6263-6264,1978.
Wisse, J. A., and A. J. Meerburg, Ozone observations at Base King
Baudouin in 1965 and 1966, Arch. Meteorol. Geophys. Bioklimatol.,
Ser. A, 18,41-54,1969.
Wolff, G. T., and P. J. Lioy, Development of an ozone river associated
with synoptic scale episodes in the eastern United States, Environ.
Sci. Technol^ 14, 1257-1261, 1980.
Wolff, G. T., P. J. Lioy, G. D. Wight, R. E. Meyers, and R. T. Ceder-
wall. An investigation of long range transport of ozone across the
mid western and eastern United States, Atmos. Environ., II, 797-
802,1977.
World Meteorological Organization, Report of the meeting of experts
on sources of errors in detection of ozone trends. Rep. 12, WMO
Global Ozone Res. Monit. Proj., Geneva, 1982.
J. A. Logan, Center for Earth and Planetary Physics, 108 Pierce
Hall, 29 Oxford Street, Harvard University, Cambridge, MA 02138.
(Received February 25,1985;
revised May 17, 1985;
accepted May 17,1985.)
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Paper?
Effects of Increased UV Radiation on Urban Ozone
-
• by
I Gary Whitten
Systems Applications, Inc.
This presentation was based upon the following paper prepared for the workshop.
I
I Effects on Urban Smog Resulting From Changes in the
Stratospheric Ozone Layer and in Global Temperature
I by
— G.Z. Whitten
• M.W. Gery
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> EFFECTS ON URBAN SMOG RESULTING FROM
CHANGES IN THE STRATOSPHERIC OZONE LAYER
AND IN GLOBAL TEMPERATURE
I
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• by
G. Z. Whitten
• M. W. Gery
Systems Applications, Inc.
1101 Lucas Valley Road
San Rafael, CA 94903
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• Presented at the U.S. Environmental Protection Agency Workshop on
"Global Atmospheric Change and EPA Planning"
_ Raleigh, North Carolina
— 11-12 November 1985
I
™ 163000 65 85176
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Paper 7
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Paper 7
EFFECTS ON URBAN SMOG RESULTING FROM
CHANGES IN THE STRATOSPHERIC OZONE LAYER
AND IN GLOBAL TEMPERATURE
As part of ongoing research into the nature and causes of photochemical
smog, Systems Applications, Inc. has conducted a preliminary investigation
into the potential changes in urban ozone levels due to an increase in
solar ultraviolet (UV) radiation resulting from reductions in the strato-
spheric ozone layer. Estimates were also made of the effects on urban
ozone chemistry resulting from a general warming of the lower atmo-
sphere. Hence, the focus of this study was on the effect of reductions in
stratospheric ozone by as much as 30 percent on (1) peak ozone concentra-
tions in urban areas and (2) the attendant control requirements predicted
by a modified version of the Empirical Kinetics Modeling Approach (EKMA).
The model used in this study was the simple trajectory model used in the
EKMA. This model was developed by the U.S. Environmental Protection
Agency (EPA) and is widely used to assess the effectiveness of emissions
control scenarios to abate urban ozone. Because these investigations were
intended as the first phase of a more thorough study of these potential
effects, only simple modeling techniques were applied to a limited number
of situations.
PHOTOLYSIS RATE RELATIONSHIPS
A reduction of the atmospheric ozone column is known to allow more ultra-
violet radiation to reach the global surface in the wavelength region
between 280 and 330 nm (Bane et al., 1979). In addition to causing
biological effects as skin cancer, radiation in this region plays a major
role in smog chemistry. We began by investigating the ozone formation
processes in the lower troposphere that would be affected by increased UV
transmission through the atmosphere. From this preliminary work, it is
evident that the photolysis channel of formaldehyde that leads to radical
products is selectively enhanced at a higher UV flux. Formaldehyde
emissions are products of incomplete combustion, and formaldehyde is a
major intermediate oxidation product from virtually all organic
molecules. Since radicals from formaldehyde photolysis are the main
source of radicals needed to drive the chain reactions that generate
85176 2T
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photochemical smog (Whitten, 1983), an increase in rate of photolysis
would have a bearing on the design of future control strategies.
The photolysis of ozone to electronically excited oxygen atoms is thought
to be the second most important source of the radicals that drive smog
formation. However, the role of ozone photolysis is different from that
of formaldehyde because ozone is the principal ingredient of photochemical
smog. At low levels of oxidation potential, the excited oxygen atoms tend
to accelerate smog reactions, making the atmospheric chemistry more
efficient in generating ozone from minimal precursor emissions. However,
at the highest or most severe ozone levels, the excess radicals can
partially suppress the ozone peak, making the precursors seem less
efficient in generating ozone. Other photolysis rates can also be affec-
ted, but their contribution to smog formation is less important.
A specific increase in formaldehyde photolysis to radical products is
difficult to determine accurately for a number of reasons. Atmospheric
photolysis rates have often been calculated in 10 nm wavelength
intervals. However, the accurate calculation of formaldehyde photolysis
requires fine spectral resolution for both the formaldehyde absorption
cross-section and the surface solar flux (related to the ozone absorption
cross-section). Only in this manner can a comparison of the respective
fine structures be performed. Near-ground solar flux data of high
resolution and known stratospheric ozone abundance have not been readily
available. Although we have obtained high-resolution absorption cross-
section data, we are currently estimating surface solar fluxes using low-
resolution information provided by the National Aeronautics and Space
Administration. Figure 1 shows two different determinations of the UV
absorption spectra of formaldehyde. Figure 2 shows a high-resolution
spectrum of surface solar flux data.
The necessary photolysis rate parameter, commonly refered to as the "J
value" is obtained from integration of the product of absorption cross-
section, light flux, and quantum yield over all relevant wavelengths.
Figure 3 shows the product function for the two formaldehyde cross sec-
tions given in Figure 1. Plots of the product functions against wave-
length are often referred to as the "photoaction spectrum." The J-value
is the area under this photoaction curve. Figure 3 was generated from a
NASA computer program for the UV flux (which has only a 5 ym resolution)
and quantum yield data from NASA (1983). The 1 nm values in the figure
were determined by linear interpolation of the solar radiation data. The
photoaction spectrum using high-resolution UV data has not yet been
generated. However, a comparison of Figures 1 and 2 shows that there can
be several overlaps in fine structure. At this time, we have determined
that a minimum resolution of 0.25 ym is required. Coarser resolutions
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HCHO
277 LK
270 280 290 300_ 310 320 330 340 350
Wavelength (nm)
I I I I I I I I I I I I I I
2700 2800 2900 3000 3100 3200 3300 '3400 3500
Wavelength (A)
FIGURE 1. Formaldehyde absorption cross sections from Moortgat (1985)
and Bass et al. (1980).
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Paper 7
Formaldehyde absorption
Solar flux2
1200
1000
305
310
Wavelength (nm)
315
"320
FIGURE 2. Matched high-resolution spectra for formaldehyde cross section and sblar
flux. 1. Source: Bass (private communication 1985). 2. Source: Bahe et al (1979}.
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4.00
3.20
CD
+
UJ
EJ
X2.40
x
ZJ
U
UJ
0.
en
o
u
CC
o
I—
o
•r.
Q_
1.60
0.80
0.0
Moortgat
et al
300
310 320
WflVELENGTH (NMJ
330
340
FIGURE 3. Formaldehyde photoaction spectrum using the absorption cross sections
of Moortgat (1985) and Bass et al. (1980).
85176 5
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Paper 7
would miss the overlaps in fine structure, whereas finer resolutions
should not affect the calculated J-values.
Figure 2 also shows a correspondence between the peaks of the formaldehyde
absorption spectrum and dips in the solar flux. This correspondence
suggests that formaldehyde in the troposphere is affecting the photolysis
rate of formaldehyde at the surface. This finding is consistent with
observations of tropospheric formaldehyde in the 0.2-0.5 ppb range and
indicates that theoretical calculations of the J-values for formaldehyde
must take tropospheric formaldehyde absorption into account along with
high-resolution UV data.
Figure 4 shows a high resolution photoaction spectrum for ozone derived
from the surface solar data of Bahe et al. (1983). This data was collec-
ted with a Dobson Unit (DU) of 300.* The figure also shows a 200 DU
curve, which was calculated by applying the 300-to-200 DU ratios of the
calculated NASA solar data to the measured 300 DU solar data of Bahe et
al. (1983). The increase in UV to the short wavelength side is evident in
the plot.
MODEL PREDICTIONS
Using the spectral data, we estimated formaldehyde and ozone photolysis
rates as a function of zenith angle and ultraviolet flux changes due to
stratospheric ozone depletion. The estimated photolysis rates for formal-
dehyde, coupled with the information compiled for surface ozone photoly-
sis, provide the inputs needed to calculate diurnal photolysis rates for
projected future ozone column densities. This information is then used to
evaluate the future impact of stratospheric ozone changes on near-surface
smog formation.
The preliminary results of the possible effects of increased ultraviolet
radiation on urban smog are based on simulation of atmospheric conditions
for three urban cities:
(1) Nashville—because it is nearly in compliance with the 0.12 ppm
federal ozone standard.
•j
* This unit of measure is the height (in 10 cm) that all ozone molecules
above the earth's surface would attain if all those molecules were
compressed to pure ozone at 1 atmosphere pressure and 298 K.
85176
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300
305 310
HflVELENGTH (NH)
315
320
FIGURE 4. Photoaction spectra for ozone using the measured solar
radiation of Bahe et al. (1979) at 300 Dobson, and a 200 Dobson estimate
from information provided by NASA-Goddard.
85176
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Paper 7
(2) Philadelphia—to represent cities that require moderate control
(30-50 percent reduction in organic precursors) to achieve the
0.12 ppm standard.
(3) Los Angeles—because of the severity of the exceedance of the
ozone standard in that region.
Present-day predictions are based on a total ozone column of 300 OU and
future predictions are based on a total ozone column of 250 and 200 DU. A
33 percent decrease in total ozone column would increase ozone photolysis
by nearly a factor of two, and increase formaldehyde photolysis to radical
products by nearly 20 percent. Both of these increases are still somewhat
uncertain because of uncertainties regarding the spectral fine structure
and other factors.
The effects of these photolysis rate increases are given in Table 1 for
298 K and 302 K. For all three cities, the model predicts higher ozone
concentrations resulting either from increases in temperature or decreases
in the Dobson number. The magnitude of the increases in ozone is
apparently a function of local hydrocarbon-to-nitrogen oxide ratio, reac-
tivity, meteorology, and emission distribution. The linearity of the
response to stratospheric ozone depletion is not general. For the Los
Angeles case, the increases in ozone are moderate and quite linear with
decreasing Dobson number. For the Philadelphia case, ozone is predicted
to increase progressively as the Dobson number declines; that is, only a
modest increase in ozone is seen for a decline in Dobson number from 300
to 250 units, but a more dramatic increase in ozone is seen when the Dob-
son number declines from 250 to 200 units. For the Nashville case, the
increases are all very dramatic and the linearity is a function of
temperature. At the more normal temperature of 298 K, the simulated urban
ozone tends to increase linearly with Dobson number decrease; but at the
warmer 302 K temperature, the simulated ozone increases more for the first
50-unit Dobson change than for the second 50-unit change, down to the 200
unit limit studied.
The effects of a 4 K increase in temperature are most pronounced in the
Los Angeles and Nashville simulations where 14 to 23 ppb increases in
simulated ozone peaks are predicted. The effects of a combined tempera-
ture increase and reduced Dobson number appear to be always additive, if
not synergistic, especially for the Nashville simulations. When a 4 K
temperature increase is combined with only a 50-unit Dobson reduction, the
simulated peak ozone jumps from a base value of 0.13 ppm to over 0.18 ppm
ozone.
The EKMA isopleth diagram for Nashville shown in Figure 5 indicates that
peak ozone is nearly independent of total precursor loading (for 300 DU,
85176 2T
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• Paper 7
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TABLE 1. Ozone concentrations (ppm) predicted for changes in Dobson
• number and temperature for three cities.
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| * For Los Angeles, values under 298 K used actual hourly temperatures
and values under 302 K are from simulations using those temperatures
_ increased by 5 K.
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Ozone Concentrations
Temperature (K)
Dobs on Number
City
Los Angeles*
Philadelphia
Nashville
300
0.288
0.112
0.130
298K
250
0.301
0.127
0.161
200
0.315
0.149
0.195
300
0.306
0.122
0.146
302K
250
0.318
0.134
0.184
200
0.331
0.159
0.215
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Paper 7
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Paper 7
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Paper 7
298 K), but rather strongly defined by the ratio of organic-to-nitrogen
oxide precursors. Thus, substantial changes in emissions of volatile
organics (VOC) and nitrogen oxide (NOX) might occur without affecting peak
ozone as long as the ratio of VOC/NOX is held constant. An increase in
temperature or ultraviolet flux evidently alters the ratio of VOC/NOX,
which results in 0.13 ppm ozone.
The isopleth diagram shown in Figure 6 corresponds to the 200 Oobson
number/302 K case shown in Table 1 for Nashville. The difference isopleth
for Figures 5 and 6 is shown in Figure 7. From this difference isopleth
we see that the sensitivity to UV and temperature perturbations is both a
function of VOC/NOX ratio and overall concentration. Hence, control
strategies aimed at lowering the VOC/NOX ratio (by emphasizing VOC control
over NOX control) may be undermined by either decreases in the Dobson
number or increases in tropospheric temperature, but control strategies
that reduce the total VOC and NOX loading (even at the optimum VOC/NOX
ratio for generating ozone) will probably be little affected by such
global effects.
Another way of describing the simulated effects of increased UV radiation
is to say that the extra UV flux is equivalent to increasing the reacti-
vity of the VOC mix. Figure 8 shows the diurnal curves of N0£ and ozone
in the Philadelphia simulations. Although the ultimate ozone peaks
increase from about 0.11 ppb to only about 0.15 ppm, the shape of the
ozone curve shows that ozone above or near the 0.12 ppm standard is
reached much earlier in the day. Trajectory models such as that used here
imply an equivalence in distance with time. Therefore, an occurrence of
high ozone concentrations earlier in the day implies that more people will
be exposed to episodic levels of ozone. Often the population density
increases as the distance from the high initial sources of precursors
decreases. Hence, the number of people exposed to episodic ozone levels
may increase dramatically if the ozone peak occurs earlier in the day.
RECOMMENDATIONS
The results of our preliminary investigation suggest the following recom-
mendations:
The appropriate type of model for assessing effects on population
exposure would be a grid model rather than a trajectory model. In
addition to providing estimates of the increased number and hours of
exposure, a grid model could provide estimates of changes in the
horizontal spread of an episodic cloud that might result from global
effects.
85176 2T 12
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Paper 7
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Paper 7
Since the processes we nave discussed represent different types of
processes than those previously investigated (e.g. projected future
increases in rates of reaction, rather than in emissions or boundary
conditions), a larger number of test cases than have been thus far
performed should be investigated. The study of future changes for
additional urban scenarios should provide a clearer understanding of
the atmospheric consequences of these processes and indicate a
clearer range of expected changes in future control strategies.
In addition to the simulation of various single-day urban episodes,
multi-day and long-term scenarios should be investigated. Increases
in the urban photochemical production of ozone, combined with varia-
tions in the concentrations of species above the mixing layer due to
global effects, could cause changes in nocturnal and next-day chemis-
try that are not obvious from single-day simulations. Species above
the mixing layer can come from the free troposphere as well as from
carryover from the same or upwind urban areas. Both free-troposphere
and carryover species would likely be affected by changes in the
stratospheric ozone layer or by global warming.
Also, since the calculations that should be performed for these simu-
lations are relative to the Dobson number, differences in seasonal
extremes of photochemical ozone production with respect to measured
Oobson variation can be investigated for present and future
scenarios. Present-day smog episodes may occur more frequently in
the fall than in the spring, due to the seasonal shift in Dobson
number.
Our investigation of the key reactions involved in the temperature
effect indicated that PAN chemistry explains most of this effect;
that is, increased ozone at the higher temperatures is offset by
reductions in PAN concentrations. Since this preliminary study of
the effect of temperature involved only the effect on chemistry,
follow-on work should include the possible effects of increased tem-
perature on emission rates and meteorology. Emissions from evapor-
tive sources and emission sources related to additional use of air
conditioning would obviously increase. Also, the frequency and
intensity of smog episode meteorology would require further study to
elucidate the effects of global warming on smog intensity.
85176 2T 15
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Paper 7
REFERENCES
Bass, A. M., L. C. Glasgow, C. Miller, J. P., Jesson and D. L. Filken.
1980. Planet. Space Sci., 28:675.
Bane, F. C., W. N. Marx, U. Schurath, and E. P. Roth, 1979.
Determination of the absolute photolysis rate of ozone by sunlight,
03 + hv -»• 0(^0) + 62 (*Aq), at ground level. Atmos. Environ.,
13:1515.
Bahe, F. C., H. Illner, W. N. Marx, U. Schurath, and P. Roth. 1979.
"Messung der von Veranderungen der Ozonschicht stark abhangigen
kurzwelligen Sonnenstrahlung. Gesellschaft fur Strahlen- und
Umweltforschung MBH, January 1979.
NASA. 1983. "Chemical Kinetics and Photochemical Data for Use in
Stratospheric Modeling." National Aeronautics and Space
Administration, Jet Propulsion Laboratory, California Institute of
Technology, Pasadena, California.
Whitten, G. Z. 1983. The chemistry of smog formation: A review of
current knowledge. Environ. International, 9:447-463.
85176 3
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• PaperS
_ Linkages between Climate Change and Acid Rain
• by
lisl
U.S. Environmental Protection Agency
™ This paper was based upon the presentation made at the workshop.
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• Dennis Tirpak
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™ Paper 8
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I Linkages Between
£ Global Climate Change
— and Acid Rain
1
Dennis A. Tirpak
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m February, 1986
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I [The views expressed are those of the author.
They do not represent official views of the
U.S. Environmental Protection Agency.]
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m Linkages Between Global Climate Change and Acid Rain
• Introduction
Two important problems facing the atmospheric and ecological
B science communities and government policy analysts are changes in
the global atmosphere from increased C02 and trace gases and
• . the acid rain phenomenon.
fl Acid rain and climate change from the greenhouse effect
have independently evoked considerable attention and concern
• as issues of public policy, but the circumstances that have
shaped the issues are quite similar. For example, in both
m cases the scientific community recognizes that large uncer-
H tainties in atmospheric modeling and complex chemical and
physical interactions present challenges limiting their ability
• to provide answers to questions of causality, magnitude, and
implications. Faced with the absence of clear signals, the
I policy community has walked a tightrope between the scientific
m uncertainties surrounding these issues on one side and the
potentially large economic and environmental risks on the
• other side.
The Federal government has two separate programs to
| address these issues: i.e., the National Climate Program
~ (NCP) and the National Acid Precipitation Assessment Program
* (NAPAP). While these programs have largely evolved along
M independent paths, they have in fact many scientific and
policy issues in common which have not been heretofore
I explicity recognized. For example, will climate change
enhance or negate the impacts of potential S02 controls?
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2 Papers
Could natural source emissions of S02 and NOX resulting from
climate change partially offset potential anthropogenic
source reductions? Could increased precipitation resulting
from climate change alter the rainout of pollutants before
they reach ecologically critical receptor areas? Will total
deposition change? What will be the combined effects of
changes in carbon, nitrogen and sulfur on forests, aquatic
systems and materials? How will proposed solutions to the
acid rain problem affect long-term climate trends.
The purpose of this paper is to examine some of the scientific
connections between these problems and to speculate about their
implications. It will also briefly explore the management
and policy styles that have shaped the approach to these
problems. The implications formed in this paper are that much
more must be done to develop appropriate research and to
assess the implications of climate change on acid rain policy.
We must begin to chart a national research course that fully
links these two issues.
FORCES SHAPING APPROACHES TO THE PROBLEMS
The National Climate Program (NCP) and the National Acid
Precipitation Assessment Program (NAPAP) have their origins
in different Congressional authorities. The former program
was initiated as a result of the "National Climate Program
Act of 1976 - Public Law 95-367" and the latter program had
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Paper 8
1
• its origin in Public Law 96-294, "The Energy Security Act of
^ 1980". As a result of these different laws, two distinct and
• independent management structures have evolved with different
• relationships within the Federal research establishment and
the university community.
M In the evolution of these programs, there has been an
implicit assumption that the problems involve different time
P scales. The acid rain problem has been viewed as a problem
• that must be solved in the 1990' s. This target date has
evolved because of the perception that current ecological
• evidence suggests that a rapid solution is required and
because of the implication that a major new control program
• would take at least a decade to implement. Beyond the 2000 -
• 2010 period, the emission modeling community has typically
forecast that the number of older electric utility and industrial
• sources would decline thereby reducing emissions. In contrast
the climate change problem has been viewed as a problem of
the mid twenty-first-century. This impression grows out of
the manner in which large Global Circulation Models (GCMs)
I
have been utilized to predict climate change. In many cases,
I scientists have used a doubled C02 atmosphere as a reference
case when running Global Climate Models (GCMs). The general
| prediction for when CC"2 will double is the year 2050, plus or
_ minus 20 years. This date often appears in the literature
* and the popular press as the target date for significant
• climate changes.
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Paper 8
In addition, to temporal differences, the problems have
generally been seen to have different spatial scales. Acid
rain is recognized as a regional or subcontinental scale
problem and climate change as a global issue. Model development
activities have relected this difference in the specification
of grid scales, boundary conditions and input data. For
example, typical GCM's have grid scales of hundreds of miles,
while long range transport models developed for source receptor
studies have grids under 100 miles.
Finally, the nature of the effects have been perceived
to be significantly different. For example, the principal
concerns associated with acid rain are effects on aquatic
ecosystems, forests and materials in sensitive regions or in
areas with high deposition levels. The effects of changing
climate touch all of the above plus impacts from sea level
rise, on crop productivity, hydrology, and human health
indeed almost every aspect of society.
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- 5 -
The Time Dimension
There is uncertainty over how and when the earth will
M respond to increases in atmospheric carbon dioxide, CFCs and
other trace gases. However/ the "greenhouse" effect, i.e.,
• the process by which these gases trap heat in the lower
atmosphere, is one of the most well analyzed of the potential
• responses. This effect has been of interest because for several
m decades/ scientists have measured the increases in atmospheric
C02 at Mauna Loa Observatory. The steady rise in the annual
• average concentration of C02 from 316 ppm in 1959 to over 345
ppm in 1984 has generally been accepted as a global trend
i
m Keeling (1,2). For comparative purposes, various reports
m by Brewer (3), Raynaud (4) and Bojkov (5) have estimated CC>2
levels to be in the range of 260 to 280 ppm in the late nine-
tt teenth century.
The present rate of increase of atmospheric CC>2 (about 1.5
^ ppm per year)/ suggests that it will take more than 150 years
^j for C02 to approximately double the preindustrial concentrations.
™ But emission rates for C02 have not remained constant in the
• past and most assuredly will not in the future. The most important
factors influencing emissions are the rate of population growth,
| the rate of worldwide energy consumption, and the fraction of
total energy supplied by fossil fuel. For example, world energy
™ consumption prior to 1973 grew at about 5 percent per year, but
£• in response to rising energy prices, the growth of energy
consumption has been reduced to about half the earlier rate
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Paper 8
- 6 -
according to a report of the World Energy Conference (6).
A complete summary of C02 emission scenarios is presented
by Perry (7) and by Ausbuel and Nordhaus (8). The most
reasonable estimates of energy forecasts, suggest that growth
rates for carbon releases to the year 2030 will most likely
range between one and half to three percent per year.
Wuebbles (9) described the corresponding atmospheric C02
concentrations in ppm empirically to be:
[C02] = 341.4 + 1.539 (t-to) exp [0.00917 (t-to)]
where t is the time in years beyond 1983. This suggests that
atmospheric C02 will double from preindustrial levels in the
period between 2050 to 2060.
However, C02 is not the only gas capable of modifying future
climate. Other trace gases, including the chlorofluorocarbons,
nitrous oxides, methane, and carbon tetrachloride were first
noted to be increasing in the atmosphere according to Lovelock,
Singh, and Rasmussen as summarized by the World Meteorological
Organization (10). For example, production of CFC-11 (CC13F)
and CFC-12 (CC12F) is projected by Quinn (11) to increase
by 7.2 percent and 3.6 percent annually while atmospheric
concentrations are increasing by approximately 10 percent per
year according to Cunnold (12, 13). The rate of increase in
atmospheric methane has been estimated to be between one and
two percent. The impact of these trace gases on mean global
temperatures has been estimated by Ramanathan et. al. (14)
to be roughly equivalent to that of C02- Predicting growth
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• Paper 8
I
rates for all of these compounds beyond the year 2000 is
I difficult, but conservative estimates suggest that the result
of changes in these gases will be to shift the equivalent
impact of C02 doubling to the time period between 2030 and
^ 2050. This perception of the new equivalent doubling
™ time is recognized in a recent conference statement by the
• United Nations Environment Program/ World Meteorological
Organization and the International Committee of Scientific
P Unions (15) which notes that, "The role of greenhouse gases
— other than C02 in changing the climate is already about as
P important as that CC>2. If present trends continue, the
fej combined concentrations of atmospheric C02 and other greenhouse
gases would be equivalent to a doubling of C02 from pre-
• industrial levels possibly as early as the 2030 's".
What then is the significance of a doubled CC>2 world and
• how is it related to the timeframe associated with the acid
Ik rain problem? In responding to these questions it must be
recognized that a doubled C02 world has been fabricated and
• utilized by the climate research community as a bench mark
for comparing results and estimating climate effects. Typically
• global climate models are run by initializing the models with
m a doubled CO2 atmosphere, because simulations with small
increases in CC>2 provide results which are difficult to
•
i
i
interpret. The doubled C02 silulations, while often dramatic,
orovide only a snapshot of what the climate might be like at
some future date. However, climatological changes resulting
from increased emissions of CC>2, CFCs and other trace gases
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Paper 8 j
- 8 -
are taking place today,, although not readily apparent. These J
changes will become increasingly evident according to Hansen (16),
in the next 10-30 years, depending upon the degree of buffering I
provided by the oceans, the extent to which changes in cloud I
cover amplify or retard the warming and other factors. Thus
significant climate changes are likely to occur in the time j
frame under consideration by Congress and other governments
for implementing an acid rain strategy. 1
Second, there is a growing recognition that at least some j
aspects of the acid rain problem are long term processes. For
example, acid deposition impacts on various soil systems and I
materials are most likely to have long term impacts which may
not be easily quantified for decades. Impacts on many lake |
systems are described as extensive according to the results of j
recent surveys by the Environmental Protection Agency (17).
In some cases, e.g., lakes in the southeast, the acidification 1
process is thought to be associated with long term natural
acid producing processes, while in other cases e.g. high ^
elevation lakes, acidification may take place more rapidly.
The acidity of individual watersheds appears to be a function
of lake elevation, physical and geologic features and the percent
of watershed covered with coniferous vegation. In contrast,
current hypotheses on forest damage have not yet permitted a
clear understanding about the rate or causes of forest decline
in Germany and the United States. While the rate of damage
appears to be high in Germany, one or more phenomenan, including
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Paper 8
I
air pollution and climate, may ultimately be proven to be the
p cause. The differences between the U.S. and German forest
— problems make guesses about the rate of decline speculative.
* A third factor influencing current thinking about the
M time dimension of the two problems is the perception that the
potential need for acid rain controls will diminish sometime
m between 2010-20 because older, more nonpolluting, utility and
« industrial sources will be replaced by lower emission sources
of SC>2 and NOX. However, there is a growing recognition that
• difficulties in obtaining suitable new sites, in raising
capital, and in obtaining permits now make it more likely that
• utlities wil extend the lives of existing plants.
Recently, the Congressional Office of Technology Assess-
• ment (18) found that by the year 2000, nearly a third of the
fl| existing U.S. fossil generating capacity will be more than 30
years old, including about 700 coal fired units totaling
• nearly 40,000 MW. In the past, the benefits of new technology
outweighed the benefits of plant improvements, but plants
reaching 30 years of age over the next decade have attractive
M unit sizes (100 MW or larger) and performance (heat rates of
* 10,000 Btus/KWh). Extending the lives of such units at an
fl anticipated capital of cost $200-400/KW is an extremely
attractive opportunity for many utilities. In many instances
P plant improvements can also include up to 5 percent efficiency
^ improvements and /or capacity upgrades of 5-10 percent.
* Current research efforts by the Electric Power Research
1
I
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Paper 8 J
- 10 - *
Institute and individual utilities may soon make it economically J
attractive to extend the lifetime of many plants from 40 to
60 years or more. In theory, there are few obstacles to \
extending the life of an existing plant almost indefinitely. »
As a result of this process, it is possible as shown in Figure (1)
that many existing sources will continue to operate well 1
beyond the 2010-20 time period.
In summary, some aspects of the acid rain problem are |
increasingly likely to be viewed as a long term ecological u
issue, rather than a problem requiring an "emergency response". *
It is also probable that efforts to extend the life of many 1
existing utility plants will inadvertently extend the time
period of concern about acid rain well into the next century. I
Hence, as shown in Figure (1) the sensitive timeframe for _
acid rain is sliding forward into the next century, while *
perceptions about when climate change will be important are fl
shifting backward in the direction of the early decades of
the next century. jl
CLIMATE IMPACTS ON ACID RAIN PROCESSES
The National Academy of Sciences reports that a doubling of
the concentration of atmospheric CO2 will raise the earth's global
temperature by 3°^ 1.5°C. This estimate is based on predictions
from different atmospheric models with the most complex being the
general circulation models (GCMs). These models predict climate
from first principles. They break the atmosphere into several
layers which are represented by energy equations and components
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11 Papers
9 of the wind velocity. GCMs also solve radiation and transport
m equations to obtain heating or cooling in each layer. A
review of modeling studies is provided in several reports
I including reports by the National Research Council (19) and
Schlesinger (20).
B The results of various modeling studies generally agree
fon two conclusions: (1) that the atmospheric surface air
temperature will rise and that this temperature increase will
fl be much greater in the polar regions than at equatorial
latitudes, and (2) that there will be alterations in the
P hydrologic cycle including changes in regional precipitation
^ and evaporation. Current models cannot predict with great
•
9 specificity parameters such as humidity, groundwetness,
• cloud cover, windfields, and snow cover, but preliminary numerical
experiments and sensitivity analyses yield insights into
• these topics.
^ For example, the work of Hansen (21) and Washington (22)
W suggest that there will be:
J| o Increases in zonal mean precipitation at all
latitudes due to increases of available moisture
• evaporated from warmer oceans.
o Decreases in soil moisture in tropical and subtropical
P continental areas and increases at higher latitudes.
m At the mid latitudes the change depend on the season,
for example, soils may be drier.
I
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Paper 8
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Paper 8 J
- 12 -
o Increases in humidity at most latitudes because of \
more evaporation. j
o Increases in clouds depending on altitude in the mid
latitudes. I
o Changes in the strength and direction of major wind
patterns because of decreases in the mid- and 1
lower troposphere equator-to-pole temperature _
gradients. *
o Increases in precipitation in the northern hemisphere 1
during the winter.
o More persistent droughts in some areas of the south I
and eastern U.S. and more sequences of wetter than
normal months in the northwest.
o Decreases in the number of days that the surface
temperatures drops below 0°C
These results, while not a forecast, can be used to speculate •
about how climate change can affect acid deposition in the future.
For this purpose, a representative list of potential climate •
changes and the associated acid deposition implications is •
presented in Table 1. While not comprehensive, it is apparent
from Table 1 that climatological shifts have the potential to I
both enhance and negate the impacts of potential acid rain
policies. In the following discussion, consideration is given to |
two climate parameters where there is agreement that significant M
changes will occur, namely temperature and precipitation.
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TEMPERATURE EFFECTS ON ACID RAIN
The temperature increases projected to occur because of
rises in C02 and other trace gases will have significant
atmospheric and ecological effects related to the acid rain
• problem. Among these effects are those associated with
shifts in global wind patterns, changes chemical reaction
W rates in the troposphere and changes natural emission rates.
M Still other important changes related to future temperature
increases are alterations in cloud cover and humidity and an
• extension of the growing season.
• 1) WIND PATTERNS
Winds are generated around the world because radiation
• from the sun is not equally distributed over the globe. As a
result, temperature and pressure gradients are created between
i
w the equator and the poles and winds act to reduce these
tt gradients. Changes in temperature at the equator and
the poles associated with increased CC>2 and trace gases will
• alter these winds. For example, according to one GCM experiment
by Washington, at the equivalent of doubled CO2» there is a
V decrease in the strength of the mid-latitiude westerlies in
A the summer between 30°-60° latitude. It was also demonstrated
that westerlies north of 60° latitude increase in strength in
• the winter because the greatest relative increases of lower
tropospheric warming for doubled C02 occur near the sea ice
B margins. While these results are not precise enough for
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Paper 8
- 14 -
decision making, there appear to be two kinds of implications
which are important.
First, if windfields shifted significantly, the manner
in which current source-receptor models are used to analyze the
transport and deposition of sulfur species would have to be
altered. Because current models are pretuned to historical
data, their applicabilty to the 2010-2020 time period will
be limited. To determine the importance of such changes
a series of sensitivity studies using a range of windfields
and other climatological parameters generated by several
CMC's could be conducted.
Second, summertime stagnation episodes with elevated
temperature and pollution levels have always been a focus
of concern to the the air pollution community because of
their important health and ecological impacts. For example,
Altshuller (23) and others have demonstrated the relationship
between increased sulfate concentrations and the summer months.
He noted that increased summer sulfate concentrations appeared
to be related to increases in regional emissions of SOx, to
photochemically induced reaction processes and to a higher
frequency of summer regional scale sulfate episodes. In the
future, changes in the frequency and duration of these blocking
events appear to be likely as demonstrated by Mearns, Katz and
Schneider (24) who examined historical temperature data to
determine that the number high temperature episodes was
likely to increase with even a modest 1.9°C change in global
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• Paper 8
I
™ temperature. If changes in the frequency and length of these
tf epsiodes is demonstrated with additional analyses to be
correct, traditional air pollution strategies for ozone, S02
• and other pollutants will need to be reexamined.
A 2) ATMOSPHERIC REACTION RATES
A second important impact of elevated surface air temperatures
P concerns changes in the reaction rates of sulfur, nitrogen,
M and other compounds. It is generally known that these rates
* are a function of temperature, solar radiation, humidity, and
• cloud cover. However, the precise influence of changes in
temperature on important reaction rates has been difficult
• to ascertain because smog chamber experiments are often conducted
^ with a constant radiation flux and temperature. To overcome
™ this difficulty, scientists have examined the net result of
fl| all these variables in both summer and winter field studies.
The Environmental Protection Agency's Critical Assessment
• Review Papers (25) reports on such field studies. They indicate
that upper level oxidation rates for S02 are over 12 percent hr-1
f
• for midday, summer conditions and that average conversion
rates are in the range of 3 to 5 percent hr-1 for summertime
conditions. Other data indicate that wintertime conversion
• rates are less than 1 percent hr-1. This suggests that
temperature along with other parameters plays an important
P role in the conversion of S02 to 804.
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Another relationship between temperature and clouds is
also important in determining reaction rates. It is known
from the cloud physics literature that there is a tendency
for cloud liquid water content to increase with temperture
over a broad range of cloud types. There is also some evidence
that clouds will increase with increases in C02 and trace
gases, but there remains uncertainty about the net climate
forcing induced by clouds. For example, Somerville and Remer
(26) suggest the possibility that increased optical thickness
may provide a negative feedback to stablize climate against
other radiation forcings. However, it has been demonstrated
by Gilliami and Wilson (27) that in-cloud conversion rates of
SC>2 and 864 were on the order of 10 percent hr-1, a very signi-
ficant rate compound to the average winter and summer rates.
Moreover, when clouds come in contact with mountains, the net
deposition of pollutants through direct interception is signi-
ficant. For example, Scherbatskoy and Bliss (28), have shown
that 82% of the total water available to three mountains (900-
1200m) in Vermont came from clouds with a mean pH of 3.7 com-
pared to 4.2 for rainfall. Assuming that climate change is
accompanied by increasing cloud cover, aqueous conversion
rates will increase, the potential for long range transport
will diminish and the net wet deposition in high elevation
forests will change. If the summertime is viewed as a surrogate
for temperature, cloud cover, and other climate variables,
then it can be postulated that climate change has a high potential
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to alter the transport, transformation and deposition of
acidic species.
I 3) EMISSIONS
It is well recognized that fossil fuel combustion sources
• particularly oil and coal, are yet another important link
M between climate change and acid rain. Reductions in emissions
from such sources through increased efficiency, energy
• conservation and use of alternative technologies have the
potential to slow the rate of climate change and reduce acid
rain concentrations. Natural sources of sulfur, however are
generally considered to be small. Robinson (29) has characterized
these emission to be less than ten percent of the estimated
• 12 to 15 Tg yr-1 of anthropogenic sulfur emissions. Among
the important natural sources, sulfur from soils is estimated
P to be 0.23 Tg S yr-1. The basis for these estimates is
» derived from the work of Adams (30,31) who also points out that
sulfur emission rates in tropical areas are probably at least
fl an order of magnitude higher along areas such as the U.S.
Gulf Coast than at 25°N. Adams noted that gaseous sulfur
V emissions from soils are generally considered to be related
to temperature, moist climate, the fraction of high organic
• soils and latitude.
• Climate change can alter these emission rates by changing
temperature, soil moisture, percent of coastal marsh area,
• type of vegetation and the time period between frosts. Based
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Paper 8
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on the results from Hansen, it can be assumed that the average
daily temperature maximum for many locations in the U.S. will
increase 5-7°F in a doubled C02 climate. Such a shift may be
viewed as the equivalent of shifting the climate in current
U.S. Gulf Coast States approximate 10° North. Using the
results of Adam's latitudinal relationship, it is estimated
that soil emission rates may increase nearly 10 times for the
states in the southern third of the country. Even a conserva-
tive estimate of a fivefold increase in emission rates,
taking into consideration the arid soil in the west, would
mean that sulfur emissions from soils alone would be approxi-
mately 1.15 Tg S yr-1 or nearly ten percent of anthropogenic
emissions. Moreover, most other natural emission sources of
sulfur, nitrogen, and ammonia, e.g., oceanic sources and
lightning are directly related to the changes in climate
variables.
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Precipitation
m Climate forecasts/ as generated by current GCM's/ replicate
measured precipitation at very aggregated levels. For example,
£ Hansen states that the GISS model represents dry areas in the
_, Sahara desert, off the west coast of North and South America
™ and southwest Africa and in the lee of mountain chains such
• as the Andes and Himalayas. Similarly/ regions of high
rainfall are successfully reproduced along the equator/ in
£ the Amazon and African rainforests. Seasonal precipitation
— patterns reproduced by the model are also generally consistent
™ although the poleward movement of precipitation in the summer
• over the U.S. was somewhat higher than measured.
Nonetheless, when current GCMs are utilized to predict
• precipitation patterns resulting from increased levels of
C02/ the results are less certain because of the coarse resolution
W of the modeling grids and because of the manner of parameterizing
A key processes. However/ all the GCMs suggest substantial
changes throughout the hydrologic cycle and even generally
• agree on impacts at a few locations i.e./ a dryer interior of
the U.S. particulary during the summer. For several locations
• in the U.S./ the model of Hansen et. al./ predicts changes in
g| precipitation which vary from today's conditions by approximately
+25% to -5% for doubled C02« Improvements to these models,
• will be forthcoming over the next decade as improved data
sets are generated for clouds and the oceans and as more
B vigorous methods are developed to more accurately represent
important processes.
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Other investigators including Williams (32), Pittock and
Salinger (33), and Jager and Kellogg (34) have studied the
influence of global warming on regional precipitation patterns
by comparing historical precipitation records in warm and
cold years. An analysis of long-term temperature and precipata-
tion data over the United States was conducted by Diaz and Qualye
(35). More recently Rind and Libedeff (36) compared temperature
and precipitation over the U.S. for the cold period of 1990
to 1920 and the warm period of 1940 to 1960. The global tempera-
ture difference between the two periods was about 0.3°C. They
compared their results to those of Diaz and Quayle and the
results were shown to be generally similar. Both analyses
show a precipitation increase in the Southeast and Northwest
and a precipitation decrease over the Midwest. Rind and
Libedeff show a broad increase of approximately 10% over the
eastern U.S. for a . 27°C increase in global temperature. To
assess these relationships in the acid sensitive Adirondack
Park area, temperatures and precipitation were analyzed. The
results in Figure 2, show the relationship between the ten
year mean temperature and changes in precipitation for the
period 1930 through 1980.
These temperature differences are relatively small
compared to those projected for increased CC>2 and trace
gases, but the results provide insights about the type of
changes that may take place over the next few decades.
Together with the results from GCM models these analyses
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Paper 8
FIGURE 2.
Ten Year Mean
Temperature - Precipitation
Relationship for Adirondack Park Area
-0.2 0 0.2
TEMPERATURE DEVIATIONS
FROM THE MEAN ( °C)
WARMER
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Paper 8
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suggest that shifts in mean precipitation of H^IO percent or
greater may easily be possible in the Northeast over the next
few decades as wind patterns and other climate variables
shift due to global warming. Changes in extreme precipitation
events may even be greater.
RELATIONSHIP TO ACID DEPOSITION
These changes in annual precipitation could play a
significant role in determining the form and amount of sulfur,
nitrogen/ hydrogen ions and other substances deposited in regions
sensitive to acid rain. Changes in precipitation would affect the
the concentration and total quantity of deposited acidic material
and the ratio of wet to dry deposition. We know, for example,
from work by Scott (37) that scavenging of sulfate aerosol is
a function of precipitation rate and of storm type i.e.
convective, warm/nonconvective, and cold storms. Still other
investigators have conducted field studies at different
distances from pollution sources and found that while very
little scavenging takes place directly adjacent to plumes, an
enhancement of sulfate and nitrate precipitation seems to
occur at distances up to 200km presumably because precursors
have more of an opportunity to react with atmospheric water
vapor. Also from Likens (38), we know that when precipitation
does occur, the highest concentrations of acidity generally
occur with the lowest amounts of precipitation, while total
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Paper 8
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deposition generally increases with increasing amounts of
precipitation.
In summary, changes in the location and quantity of
precipitation likely to be induced by global warming will
affect the chemical composition of important substances
deposited in sensitive regions. The potential also exists,
if regional precipitation patterns shift relative to major
source regions, to washout pollutants before reaching sensitive
areas or to increase the chance that pollutants will be dry
deposited. However, total deposition of acidic material may
not be reduced in sensitive regions, if increases due to changes
in the frequency and intensity of precipitation balance out
losses due to increased scavenging between sources and receptors.
Impacts of Precipitation on Sensitive Lakes
The potential impact of changes in precipitation on sensitive J
lakes can be examined by utilizing a model to predict changes in
alkalinity. For this purpose, the Adirondack Lakes Region was
analyzed using assumed changes in precipitation as suggested by
historical climate relationships and forecasts. The model
was developed by Schnoor (39) and modified by Hoogendyke and
Kaplan (40) to support analyses of how changes in runoff,
evapotranspiration, and sulfur deposition would effect future
lake chemistry. The Schnoor model is represented by the
equation:
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Paper 8
- 23 -
L m
k acy +k
h L o
ref
L
akalinity =1^ acy
0 R-0.1
1^ = inflow to outflow ratio (evapotranspiration concen-
Q tration factor)
k = weathering rate constant for acid hydrolysis
h
k = weathering rate constant in the absence of free acidity
o
L = total acidity input
acy
L = reference acidity
ref
m = fractional reaction order constant
R = precipitation rate
0.1 » units conversion factor
The application of this model requires various assumptions
about baseline conditions and the processes of acidification.
For example, in this application, an Adirondack Lake data set
of approximately 600 lakes was utilized and assumed to apply
to all 2,865 lakes in the region, although the appli-
cability of the model is limited for brown colored water with
high organic acid concentrations. According to Baker and
Harvey (40), approximately 37 percent of the high elevation
Adirondack lakes may be in this category.
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Paper 8
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Other key assumptions include the selection of the existing
mean annual precipitation to be 100 cm/yr, a reference acidity
level corresponding to a natural background of 5 kg/HA and a
current acidity of 40 Kg/HA. The evapotranspiration factor
was held constant at 1.2 although it can be expected that
it may vary with wind, temperature, rainfall, vegetation and
soil moisture. Hsnce, the analysis should be viewed with
caution and should not be considered a forecast of future
lake status.
With these caveats in mind, it is useful to examine
the results depicted in Table 2. The results demonstrate that
rainfall is an important variable which must be accounted for
in order to assure the efficacy of future acid rain policies.
The results for existing deposition and rainfall suggest that
up to 1,019 lakes or (35 percent) are currently below a pH 5.5,
This is in close agreement with Baker and Harvey who provide
lake survey data indicating that 34 percent of the lakes are
below pH 5.5. Table 2 also notes that the number of lakes
with a pH of less than 5.5 changes from 1,019 to 724 when
sulfur deposition is decreased and from 40 Kg/HA to 30 Kg/HA
and rainfall is constant. When rainfall is increased by 25
cm/yr and sulfur held constant the number of lakes less than
pH 5.5 change from 1,019 to 787. Finally, IF rainfall is
increased by 25 cm and deposition increased to 50 Kg/HA,
the number of lakes less than 5.5 pH is constant at 1,019.
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in in in in
in o o m
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While simplified these results suggest that uncertainties
in future climate may be an important factor in attempting
to predict the impact of acid rain control strategies on lake
systems. Moreover, it can be anticipated that forest and
material effects will also be a function of climate variables.
How significant a factor climatology will be in altering acid rain
impacts must await the development of improved lake, forest and
material models. However, it is apparent that current efforts to
reduce uncertainty in long range transport models, air pollution
data bases and lake models may be of little value, in the absense
of corresponding efforts to understand the impact of future
climate.
THE MANAGEMENT STYLES
The NCP and NAPAP programs had very different origins
and consequently evolved significantly different budgetary and
management processes. Table 3 presents the funding history
for both programs (41). The National Climate Program was
assembled from then existing programs in several agencies
particularly NOAA, NSF, DOE and NASA. It was conceived at a
time when C02 emissions from energy sources were viewed as a
significant source of climate change. The NCPO was given a
mandate to develop an integrated budget, but the traditionally
has acted simply to provide coordination among the Federal
agencies. It has developed broad guidance while leaving
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Table 3
Funding history
for the National Climate Program (NCP)
and the National Acid Precipitation Assessment Program (NAPAP)
Fiscal Year
1980
1981
1982
1983
1984
1985
1986*
Estimated
(Million $)
NCP
121
134
141
140
145
145
145
NAPAP
11
13
18
23
27
62
80
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individual agencies to prepare and defend specific parts of
their programs. The NCP has also avoided direct management
of the program, preferring to serve in a coordinating role
when key issues of importance warranted attention, such as
whether to support major programs to measure clouds or develop
improved data on oceanographic parameters.
In contrast, the National Acid Precipitation Assessment
Program began with very limited resources, but has grown
considerably, i.e., from approximately $11 million in 1980 to
over $80 million in the FY-86 budget. The program has three
cochairmen from NOAA, DOA and EPA. The NAPAP had few of the
traditions that marked climate research activities and as a
result developed an independent budget and research planning
process. The Office of Management and Budget encouraged and
supported this process as a means of obtaining advice to
supplement the normal agency budget processes. Consequently,
the NAPAP made vigorous attempts from its inception to establish
budget priorities and to ensure that all agencies adhered to
budgeting decisions. Finally, the Executive Committee of
NAPAP closely manages activities on a week to week basis.
Program decisions are continously reviewed to correspond to
newly emerging scientific information. NAPAP*s coordinating
activities have generally focused on other air pollution
programs.
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• Paper 8
I
As a result of these different beginnings and contrasting
• management approaches the programs have developed significantly
• different approaches for planning research, conducting business
and supporting participants. From the discussion above it is
• apparent that increased coordination between the NCP and
NAPAP will become increasingly important in the future. The
| scientific links between the programs and the need to optimize
• resources for tropospheric chemistry and climatological research
will lead this process. The challenge before the federal
• agencies is to assess how this need can be accommodated in an
innovative manner and without losing sight of the framework
| and specific objectives that have shaped each program.
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SUMMARY
JB An examination of the time horizons of importance to both
the acid rain and climate change problems suggests that these
£ two issues can no longer be viewed in isolation. This paper,
_ has demonstrated that our understanding of emissions, atmos-
" pheric reaction rates, pollutant transport and acid lake effects
• are likely to be influenced by long term changes in climate.
Moreover, it is very likely that as we attempt to unravel the
I causes of forest and material damage that additional links
between climate and acid rain will probably become apparent.
m The outgrowth of this recognition must not only be a more holistic
!• approach to the conduct of acid rain and global climate research,
but also other troposheric and stratospheric programs. In a
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broader context. These issues are only symbolic of the
broader relationship between general air pollution problems
and changes in the global atmosphere. For example, there are
important reactions between CO, NOX, CH4, OH, and other oxidizing
agents that control local tropospheric ozone levels and
directly or indirectly affect the radiation balance of the
globe. Similarly, fine particulates affect regional
visibility and may influence global climate change.
In fifty years, the earth will be very different from what
it is today. Most likely, it will have higher C02 concentra-
tions, different precipitation patterns, higher temperatures
and probably higher concentrations of other atmospheric
chemicals. Any single one of these changes may be of little
concern, but in combination it is safe to say that the atmos-
phere and climate of the next century may make the world a
very different place. How can we prepare for this future?
First, we can begin to plan long term experiments that will
assess the synergistic impacts on the atmosphere and climate.
Second, we can conduct studies of future atmospheric effects
on health, ecology and welfare.
In the near term, several steps specific to acid rain
and climate should be considered:
1) A detailed assessment of both the ecological and
atmospheric impacts of climate change on acid rain should be
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undertaken to precisely define the synergistic links between
these issues. Ultimately other pollution problems could be
added to this analysis.
—
* 2) The acid rain and the climate change science communities
• should join together to define and develop potential climate change
scenarios with significance to the acid rain community. Once
I developed these scenarios should be used in long range transport
models to further our understanding of source-receptor relationships
• and in the design of acid rain effect studies.
• 3) The global climate community must begin to generate
and make available data which is useful to acid rain researchers.
• It is suggested that climate models be run with 1 1/4 x CC>2
and 1 1/2 x C02» and that greater attention be paid to the use
P of smaller grid sizes in order to improve regional predictions.
• Ultimately, as technology and computational techniques improve,
it may be possible to nestle improved chemistry models within
• global circulation models.
4) Finally, the managements of both NAPAP and NCP should
• join together to integrate these two important national
M programs and where appropriate conduct joint experiments.
The managements must assure that the resources are allocated
• in a mutually supportive manner and that the appropriate
institutional mechanisms exist to foster cooperation between
H scientists in both programs.
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i
ACKNOWLEDGEMENTS: The author wishes to acknowledge the
cooperation of M. Gibbs, and C. Hoogendyk in the preparation j
of this paper and the many useful suggestions made by colleagues
on the Acid Deposition Assessment Staff and Strategic Studies I
Staff of the U.S. Environmental Protection Agency in j
Washington, D.C. The author appreciates the assistance of
Deloris Swann in the preparation of this manuscript. I
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REFERENCES
1. C.D. Keeling, R.B. Bascaston, A.E. Bainbridge, C.A. Ekdahl,
P.R. Guenther, L.S. Waterman, and J.F.S. Chin, "Atmospheric
Carbon Dioxide variation at Mauna Loa Observatory,
Hawaii," Tellus 28:538-551, 1976.
2. R.B. Bascaston and C.D. Keeling, "Atmospheric Carbon
Dioxide Concentration and Observed Airborne Fraction," pp.
103-112 in B. Bolin, ed., Carbon Cycle Modeling, Scope
16, John Wiley and Sons, New York, 1981.
3. P.G. Brewer, 1983," Past and Future Atmospheric Concentrations
of Carbon Dioxide," p. 186-188 in "Changing Climate" National
Academy Press, Washington, D.C.
4. D. Raynaud and J.M. Barnola, "An Antararctic Ice C,ore
Reveals C02 variations over the Past Few Centuries," p. 309
Nature Vol 315, May 23, 1985.
5. R.J. Bojkov, ed., World Meteorological Organization,
p. 42 Report No. 10. Project on Research and Monitoring
of Atmospheric C02« 1983, Geneva*
6. World Energy Conference, World Energy Resources, 1985-2020.
(New York: IPC Science and Technology Press), 1978.
7. A.M. Perry, "Carbon Dioxide Production Scenarios,"
pp. 337-363 in W.C. Clark, ed., Carbon Dioxide Review:
Oxford University Press, New York, 1982.
8. J. Ausbuel and W.D. Nordaus, "A Review of Estimates
of Future Carbon Dioxide Emissions", p. 153-185, in Changing
Climate, National Academy Press, Washington, D.C., 1983.
9. D. Wuebbles, M. MacCracken and F. Luther, "A Proposed
Reference Set of Scenarios for Radiatively Active Atmospheric
Constituents", U.S. Department of Energy Report TR015,
October, 1984.
10. World Meteorological Organization - Global Ozone Research and
Monitoring project - Report No. 11, "The Stratosphere,
1981, Theory and Measurements", Geneva, 1981.
11. 'T.H. Quinn, et. al. "Projected Use, Emissions, and Banks
of Potential Ozone Dupleting Substances", Rand, Inc., Draft
Report August, 1985.
I
I
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Paper S
- 32 -
12. Cunnold, D.M., et. al., 1983a. "The Atmospheric Lifetime
Experiment. 3. Lifetime Methodology and Application to
Three Years of CFC13 Data." journal of Geophysical Research,
88:013:8401-14.
13. Cunnold, D.M. et. al., 19835. "The Atmospheric Lifetime
Experiment. 4. Results for CF2C12 based on three years
data." Journal of Geophysical Research, 88:013:8401-14.
14. Ramanathan, V. et. al.,, 1985 "Trace Gas Trends and Their
Potential Role in Climate Change," Journal of Geophysical
Research, 85:03:5547-66.
15. United Nations Environment Program, World Meteorological
Organization and International Committee of Scientitic Unions,
Conference Statement, villach, Austria, 1985.
16. Hansen, et. al., "Evidence for Future Warnming: How Larger
and When", presented at "C02 Conference of the National
Forest Products Association", June 25-27, 1984, Boulder, CO.
17. R..A. Linthurst et. al. "Chemical Characteristics of Lake
populations the Eastern united States", U.S. Environment
Protection Agency, 1986-(In Press).
18. "New Electric power Technologies," July 1985 / Congress of
the united States, Office of Technology Assessment, Report
OTA-E-247, Washington,.. D.C.
19. National Research Council, Carbon Dioxide and Climate;
A Second Assessment, p. 72, National Academy of Sciences,
Washington, D.C. T9~82.
20. M.E. Schlesinger, "A Review of Climate Model Simulations
of C02-Induced Climate Change," Report No. 41, Climate
Research Institute and Department of Atmospheric Sciences,
Oregon State University, 1983.
21. J. Hansen, G. Russell, D. Rind, P. Stone, A Lacis,
S. Lebedeff, R. Ruedy and L. Travis, "Efficient
Three-Demensional Global Models for Climate Studies:
Models I and II, pp. 609-662, Monthly Weather Review, vol.
Ill, 1983.
22. W. M. Washington, and G. A. Meehl, "Seasonal Cycle
Experiment on the Climate Sensitivity Due to Doubling of
C02 with an Atmospheric General Ciruclation Model Coupled
to a Simple Mixed Layer Ocean Model", National Center for
Atomspheric Research, March 1984.
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I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Paper 8
- 33 -
23. A.P. Altshuller, "Seasonal and Episodic Trents in Sulfate
Concentrations (1963-1978) in the Eastern United States",
p. 1337-48, Environmental Science and Technology, Vol.
14, No. 11, November 1980.
24. L. Mearns, R. Katz and S. Schneider, "Extreme High
Temperature Events: Changes in their probabilities with
Changes in Mean Temperature", journal of Climate and
Applied Meteorology
25. E. Robinson and J. B. Homalya, 1983. "Natural and
Anthropogenic Emission Sources, Chapter A-2, in A. P.
Altshuller and R. A. Linthurst, "The Acidic Deposition
Phenomenon and its Effects: Critical Assessment Review
papers," Washington, D.C., U.S. EPA, No. 600/8-84-016AF,
July, 1984.
26. R.C. Somerville and L.A. Remer, "Cloud Optical Thickness
Feedback in the CC<2 Climate Problem", p. 9668-72, Journal
of Geophysical Research, Vol. 89, No. D6, October 20, 1984
27. N.V. Gilliani, Transport Processes", Chapter A-3, in "The
Acidic Deposition Phenomenon and Its Effects: Critical
Assessment Review Papers", Washington, D.C. U.S. EPA
No. 600/8-84-016 AF, July, 1984.
28. T. Scherbatskoy and M..Bliss, "Occurence of Acidic Rain
and Cloud Water in High - Elevation Ecosystems in The
Green Mountains of Vermont", p. 449-463, in P.J. Samson
editor. The Meteorology of Acidic Deposition "proceeding
of APCA Specialty Conference Hartford, Conn. 16-19 Oct.
1983 p. 449-463.
29. E. Robinson, "National and Anthropogemic Emission Sources"
in Chapter A-2, in "The Acidic Deposition Phenomenon and
Its Effects - Critical Assessment Review papers", U.S.
Environmental protection Agency, No. 600/8-83-016AF,
July, 1984.
30. D.F. Adams, et. al., "Bigenic Sulfur Source Strengths",
Presented of 74th Annual Meeting of the Air Pollution
Control Association, Philadelphia, PA., June, 1981.
31. D.F. Adams, et. al." Biogenic Sulfur Source Strengths",
p. 1493-98, Environmental Science and Technology. No. 15,
1981.
32. J. Williams, "Anomalies in Temperature and Rain During
Warm Arctic Seasons as a Guide to the Formulation of
Climate Scenarios", p. 249-60, Climate Change, vol. 2,
1980.
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Paper 8
- 34 -
33. A. Pittock and M. Salinger, "Towards Regional Scenarios
for a C02-Warmed Earth", p. 23-39. Climate Change Vol. 4,
1982.
3.4. J. Jager and W. Kellogg, "Anomalies in Temperature and
Rainfall During Warm Arctic Seasons," p. 39-60, Climate
Change Vol. 15, 1983.
35. M.F. Diaz and R.G. Qualye, "The Climate in the United
States since 1995: Spatial and Temporal Changes p.
246-66, Monthly Weather
36. Rind and s. Libedeff," Potential climate Impacts of
Increasing Atmospheric CC>2 with Emphasis on Water Avail-
ability and Hydrology in the United Stated", U.S. Environ-
mental Protection Agency, Office of Policy Analysis
April, 1984.
37. B.C. Scott, "Parameterization of sulfate Removal by
Precipitation", p. 1375-89, journal of Applied Meteorology,
No. 17, 1978.
38. G.E. Likens, et.al. "Long-Term Trends in Precipitation
Chemistry at Hubbard Brook, New Hampshire, p. 2641-47,
Atmospheric Environmental Vol. 18. No. 12, 1984.
39. J. L. Schnoor and W. S-tumm, "Acidification of Aquatic
and Terrestrial Systems", in Chemical processes in Lakes.
Wiley Interscience, New York, 1984.
40. C. Hoogendyk and E. Kaplan, "Aquaffects: Aquatic Effects
Simulator", Brookhaven National Laboratory, February, 1985.
41. J. Baker and T.B. Harvey, "Critique of Acid Lakes and
Fish polulation Status in the Adirondack Region of New
York State", NSPAS Project E3-25 North Carolina State
University, December, 1984.
42. "National Climate Program - FY 1984-1986, Interim Plan"
Prepared by National Climate program Office, NOAA, June
1985.
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APPENDICES
Appendix A: Workshop Agenda
Appendix B: Workshop Attendees
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1
1
•
1
1
1
•
1
Appendix/:
Global Atmospheric Change
Day 1 :
Morning
10:00-10:05
10:05-10:10
10:15-10:20
10:20-10:30
10:30-11:00
11:00-11:30
11:30-12:00
and EPA Planning
November 13-14, 1985
Agenda
10:00 - 5:30
Welcome and Introduction
Meeting Purpose
OAQPS Overview
Office of Policy Analysis Overview R
Atmospheric Change Overview
Emissions and Atmospheric Concentrations
Evidence for a Greenhouse Effect
A. Ellison, EPA/ASRL
H. Jeffries, UNC
J. Weigold, EPA/OAQPS
. Morgenstern, EPA/OPA
J. Hoffman, EPA/OPPE
R. Cicerone, NCAR
J. Perry, NAS
Lunch : 12:00 - 1:30
Afternoon
1:30-2:15
2:15-3:00
OAQPS Perspective
Past and Future Changes in Climate
G. Emison, OQAPS
D. Rind, GISS
Break : 3:00 - 3:15
1
1
1
1
1
1
1
3:15-4:00
4:00-4:45
4:45-5:30
Dinner
Depletion of Stratospheric Ozone R. Stolarski, NASA/GSFC
Relationships among CO, NOX, ChU, and HO A.
Tropospheric Ozone
Thompson, NASA/GSFC
J. Logan, Harvard
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Appendix A •
Day 2 : 8:00 - 12:30
Day 2 : 8:00 - 12:30
Morning
8:00- 8:30 Discussion
8:30- 9:00 Stratospheric/Tropospheric Ozone D. Wuebbles, LLNL
9:00- 9:45 Effects of Increased UV on Urban Ozone G. Whitten, SAI
Break : 9:45 - 10:15
10:15-10:45 Linkages Between Climate Change and Acid Rain D. Tirpak, EPA/OPPE
10:45-11:00 Overview of Stratospheric Ozone Activities J. Hoffman, EPA/OPPE
11:00-12:30 Science/Policy Panel Discussion Leader: M. McElroy, Harvard
Main Meeting Adjourned
Afternoon : 2:00 - 4:00
Steering Committee Meeting
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APPENDIX B
EPA Workshop on Global Atmospheric Changes and EPA Planning
Workshop Attendees
Mr. Frederick Allen
Office of Policy, Planning, and Evaluation (PM-221)
U.S. Environmental Protection Agency
401M Street, SW
Washington, DC 20460
(202)382-4012
Mr. John D. Bachmann
Office of Air Quality Planning and Standards (MD-12)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-5531
Mr. Charles Brunot
Office of Research and Development (RD-680)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-5776
Dr. Joseph J. Bufalini
Atmospheric Sciences Research Laboratory (MD-84)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2422
Mr. Frank Camm
The Rand Corporation
2100 M Street, NW
Washington, DC 20037-1270
(202) 296-5000
Dr. Ralph Cicerone
National Center for Atmospheric Research
P.O. Box 3000
Boulder, CO 80307
(303)497-1434
Mr. Roger Cortesi
Office of Research and Development (RD-675)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-5750
Mr. Alexander Cristofaro
Office of Policy, Planning, and Evaluation (PM-221)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-5490
Dr. Larry T. Cupitt
Atmospheric Sciences Research Laboratory (MD-84)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2878
Dr. Basil Dimitriades
Atmospheric Sciences Research Laboratory (MD-59)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2706
Dr. Marcia C. Dodge
Atmospheric Sciences Research Laboratory (MD-84)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2374
Dr. Alfred H. Ellison, Director
Atmospheric Sciences Research Laboratory (MD-59)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2191
Mr. Gary Evans
Environmental Monitoring and Support Laboratory
(MD-56)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-3124
Mr. Gerald Emison, Director
Office of Air Quality Planning and Standards (MD-10)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-5615
Mr. Bruce W. Gay, Jr.
Atmospheric Sciences Research Laboratory (MD-84)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2830
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Dr. Lester D. Grant, Director
Environmental Criteria and Assessment Office (MD-52)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919) 541-4173
Mr. Mark Greenberg
Environmental Criteria and Assessment Office (MD-52)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919) 541-4156
Mr. John S. Hoffman
Office of Policy, Planning, and Evaluation (PM-219)
U.S. Environmental Protection Agency
401M Street, SW
Washington, DC 20460
(202) 382-4036
Dr. Harvey Jeffries, Professor
Room 120, Rosenau Hall 201-H
The School of Public Health
University of North Carolina
Chapel Hill, NC 27514
(919)966-5451
Mr. Bruce Jordan
Office of Air Quality Planning and Standards (MD-12)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-5655
Mr. William H.Keith
Office of Research and Development (RD-680)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202)382-5716
Dr. Robert E. Lee
Environmental Monitoring and Support Laboratory
(MD-78A)
U.S. Enviromental Protection Agency
Research Triangle Park, NC 27711
(919)541-2454
Dr. Jennifer Logan
Harvard University
108 Pierce Hall
29 Oxford Street
Cambridge, MA 02138
(617)495-4582
Mr. James Losey
Office of International Activities (A-106)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-4894
Dr. Michael McElroy
Harvard University
Room 100-E Pierce Hall
29 Oxford Street
Cambridge, MA 02138
(617)495-4359
Dr. Joe McSorley
Air & Energy Engineering Research Laboratory
(MD-65)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2920
Mr. Richard D. Morgenstern
Off ice of Policy, Planning, and Evaluation (PM-221)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-4034
Dr. Deran Pashayan
Office of Research and Development (RD-680)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-5776
Dr. JohnS. Perry (JH-810)
Board on Atmospheric Sciences and Climate
National Academy of Sciences
2101 Constitution Avenue, NW
Washington, DC 20418-0001
(202)334-3517
Dr. Francis Pooler
Atmospheric Sciences Research Laboratory (MD-80)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-4551
Dr. David Rind
Goddard Institute for Space Studies
2880 Broadway
New York, NY 10025
(212)678-5593
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Mr. Steve Seidel
Office of Policy, Planning, and Evaluation (PM-220)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 475-8825
Dr. Jack H. Shreffler
Atmospheric Sciences Research Laboratory (MD-59)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2191
Dr. Bernard J. Steigerwald
Office of Air Quality Planning and Standards (MD-10)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-5555
Dr. Richard Stolarski
NASA/GSFC
Code 616
Greenbelt, MD 20771
(301)344-9111
Dr. Anne Thompson
NASA/GSFC
Code 616
Greenbelt, MD 20771
(301)344-0834
Mr. Joseph Tikvart
Office of Air Quality Planning and Standards (MD-14)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-5512
Mr. Dennis Tirpak
Office of Policy, Planning, and Evaluation (PM-220)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-2724
Mr. John C. Topping
Office of Air and Radiation (ANR-443)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-7403
Mr. James Weigold
Off ice of Air Quality Planning and Standards (MD-11)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-5641
Mr. Stephen Wei I
Office of Policy, Planning, and Evaluation (PM-223)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202)475-8661
Dr. Gary Whitten
Systems Applications, Inc.
101 Lucas Valley Road
San Rafael, CA 94903
(415)472-4011
Dr. William E.Wilson
Atmospheric Sciences Research Laboratory (MD-84)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-2251
Mr. Dwain L. Winters
Off ice of Air and Radiation (ANR-445)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-7407
Dr. Herbert L. Wiser
Office of Air and Radiation (ANR-443)
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
(202) 382-5750
Dr. Don Wuebbles
Lawrence Livermore National Laboratory
P.O. Box 808
Mail Code 1-262
Livermore, CA 94550
(415)422-1845
Dr. Larry J. Zaragoza
Office of Air Quality Planning and Standards (MD-12)
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
(919)541-5519
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