United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
'/I
Research and Development
EPA/600/S9-86/016 Dec. 1986
4>EPA Project Summary
EPA Workshop on Global
Atmospheric Change and EPA
Planning: Final Report
Harvey E. Jeffries
The earth's climate is warming due to
"greenhouse" gases, stratospheric
ozone modifications caused by chlo-
rofluorocarbons, and tropospheric
ozone modifications caused by carbon
monoxide and methane. Consensus
among scientific researchers as to the
causes, probable magnitudes, and tim-
ing of the changes has led to a call for
assessment of policy options and im-
pacts.
This workshop was organized to be-
gin collaborations among EPA research
and policy personnel, and climate re-
searchers. 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 dis-
cussed the impact of the projected
global climate change on EPA planning.
EPA responses to climate problems
were suggested.
This Project Summary was devel-
oped by EPA's Atmospheric Sciences
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
Expanding industrial and agricultural
growth are leading to greater and
greater emissions of many compounds
that are changing the earth's atmos-
phere and climate. The changes are
broadly classified as:
• warming of the climate caused by
increasing concentrations of
"greenhouse" gases;
• modifications of stratospheric com-
position and ozone chemistry
caused by the introduction of com-
pounds, especially the chlorofluoro-
carbon gases, that contribute to
ozone depletion; and
• modifications of tropospheric
chemistry mainly caused by in-
creasing levels of carbon monoxide
and methane.
The emissions include carbon dioxide
from fossil fuel combustion, carbon
monoxide from automobile and com-
bustion sources, methane from agricul-
tural sources, nitrous oxide from fer-
tilizers, and Freons from industrial
processes.
The Global Atmospheric Change and
EPA Planning workshop was designed
to initiate active collaboration among
EPA research and policy personnel and
non-EPA climate researchers. The work-
shop served as a forum for scientific
leaders in the climate research field to
impress upon the decision makers the
extent to which they understand the
problems and believe that actions are
needed. EPA decision makers had the
opportunity to begin an on-going dia-
logue with climate researchers and to
develop a better understanding of the
relevance of this field to EPA control
policies and methodologies.
Conclusions
A. Climate Modification
Processes
There is reliable evidence that the cli-
mate of the earth is far from constant.
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The most fundamental factors influenc-
ing climate are: the solar constant (i.e.,
the energy flux at the earth's orbit) and
orbital variations that influence the lati-
tudinal 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 C02 con-
centrations are also implicated.
The composition of a planet's atmos-
phere influences its global temperature.
Gases that absorb radiation in the IR-
region can influence the global temper-
ature by intercepting some of the out-
going 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 green-
house gases. In addition to the direct
greenhouse effect of IR-absorbing
gases, there are major positive feed-
back processes that determine climate
sensitivity to long-term changes. For ex-
ample, greenhouse warming causes an
increase in atmospheric water vapor,
which leads to more greenhouse effect,
which leads to more warming. Climate
change is, therefore, discussed in terms
of an initial forcing function and the
positive and negative feedback proc-
esses that increase or decrease the ini-
tial change. Thus, the direct effect of
doubling the carbon dioxide (C02) over
pre-industrial concentrations is esti-
mated to be a temperature rise of 1.2°C
because of increased IR-radiation ab-
sorption (the direct effect); currently the
total multiplicative feedback processes
are estimated to increase the initial ef-
fect 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 ef-
fect).
B. The Dynamic Nature of the
Atmosphere
The atmosphere is in continuous mo-
tion and is coupled to the oceans and
the biosphere; in addition, the atmos-
phere's composition is a result of both
long-term and short-term chemical
cycles. The abundance of trace gases in
the global atmosphere is the result of
the interaction between sources and
sinks. 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 chem-
ical 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 (03), as well as the
reaction of hydroperoxy radicals (HO2)
with nitric oxide (NO). A major source of
HO2 radicals is the photolysis of alde-
hydes (such as formaldehyde), which
are products of all organic oxidation in-
cluding methane. Methane and CO are
the primary consumers of HO in the tro-
posphere.
The most common stratospheric pho-
tolysis process is for molecular oxygen
(O2) to photolyze into atomic oxygen
(0). The 0 atom most often reacts with
O2 to produce ozone (O3). Ozone also
absorbs UV-radiation and photolyzes to
produce O and 02 again. This cycle re-
curs many times and converts light en-
ergy into heat in the upper stratosphere.
This absorption of UV radiation limits
the amount of short wavelength, high-
energy light that reaches the earth's sur-
face. Such wavelengths can cause skin
cancer and promote rapid smog forma-
tion.
The dynamic processes and chem-
istry of the atmosphere are so complex
and interactive that mathematical simu-
lation models are the only tools avail-
able to comprehend the processes. Be-
cause of the complexity, models must
often simulate only one aspect of the
problem, using simple or average de-
scriptions for the other aspects. For ex-
ample, one-dimensional models tend to
have complex chemistry and no hori-
zontal atmospheric transport. Still,
these models predict the average con-
centrations in the hemisphere fairly
well. More complex and costly two-
dimensional models also predict con-
centrations as a function of latitude as
well. These models have to make as-
sumptions about how transport occurs
and different assumptions lead to
somewhat different predictions of the
temporal and spatial distributions of the
03-
C. Increasing Emissions
Carbon dioxide concentrations have
increased from 315 ppm in 1958 to more
than 340 ppm in 1985, a very consider-
able increase. Researchers, using sam-
ples 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. Part of the source of this increase
in C02 is from the combustion of fossil
fuel. Man's activities are injecting abou
5 gigitons per year into the atmosphere
about 50% of this material appears fr
remain in the atmosphere, the rest gc
ing into the oceans and the biosphere
Chlorofluorocarbon (CFC) concentra
tions are increasing at about 3% pe
year. Nitrous oxide (N20), which had ,
northern hemispheric concentration o
301 ppb in 1980, is increasing at abou
0.5 ppb per year. Methane (CH4) is thi
most abundant atmospheric hydrocar
bon, and in 1980 its concentration wa
1.65 ppm in the northern hemisphere
Its concentration has also been showi
to be increasing at rates between 0.!
and 2% per year, and the rate itself hai
been increasing. Near the surface, ii
rural areas of Europe and ther centra
and eastern U.S., the summertime con
centration of 03 may have increased b'
6-12 ppb since the 1940s. There is reli
able evidence for an increase in ozoni
in the middle troposphere over Europi
during the past 15 years, and weake
evidence for a similar increase ove
North America and Japan.
D. Implications for Climate am
Atmophere
Increasing the concentrations of IP
absorbing gases can cause an increas
in the earth's average global tempera
ture. Three independently developei
global climate models predict a total cli
mate sensitivity of about 4°C for a dou
bling of CO2 concentrations over prein
dustrial times or for a combination o
some increase in C02 and increases ii
other greenhouse gases such a:
methane, ozone, chlorofluorocarbons
and nitrous oxide. Although CO2 is th<
greenhouse gas that is increasing th(
most, other trace gases (Freons, N20
CH4, and O3) also have a major green
house effect. If present trends continue
their combined concentrations will lea(
to an equivalent effect of doubling thf
CO2 concentration by the 2030s insteac
of the actual doubling of the C02 con
centration that was predicted to occu
sometime around 2070. Analysis of ob
servations over the last 100 years sug
gests that the average global tempera
ture has increased 0.3-0.5°C. Mode
simulations of the changes in emissions
and concentrations over this same pe
riod also predict similar increases. Be
cause of uncertainties in the model in
puts and formulations, however, it is
not possible to ascribe, in a scientificallv
rigorous manner, the increase in globa
temperature to the increases in the
greenhouse gases.
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The photolysis of chlorofluorocar-
bons in the stratosphere results in the
release of chlorine that acts as a catalyst
in shortening the O3 formation chain re-
action and ultimately lowering the
stratospheric 03. Stratospheric O3 ab-
sorbs short wavelength UV-radiation
and thus filters such radiation from the
earth's surface. Lower 03 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 in-
crease in tropospheric gases such as
CH4 and NOX results in increases in 03 in
the troposphere. 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 Dobson Units (DU)
in the springtime. Now values are 40%
lower in October (antarctic spring). In
the winter at Halley, there is no sun-
light; 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 03. As the CFCs are con-
sumed, O3 levels gradually increase to
higher values, but by autumn the level
is still 5-10% lower than it was 10 years
ago.
Increased emissions of CO and CH4
can, through complex photochemical
interactions, result in a decrease in the
average tropospheric HO concentration.
Estimates suggest that HO concentra-
tions were as much as 30% higher in
1860 than now. Projections of emis-
sions patterns suggest that in 2035, HO
concentrations will have decreased an-
other 20-30%. Not only will many trace
gases (including some toxics) survive
longer in such conditions, so will CH4,
which contributes to the greenhouse ef-
fect. Longer survival in the troposphere
also means a greater concentration in
the stratosphere through tropospheric-
stratospheric coupling and transport.
Preliminary modeling studies of
urban smog formation have shown that
increased UV-radiation and global tem-
perature may cause a significantly en-
hanced potential for smog formation.
The combined effects appear to be addi-
tive in some scenarios, resulting in e.g.
a 40% increase in 03 in the Nashville
urban area.
Climate changes may have a variety
of impacts on the acid rain problem. For
example, increased air temperatures
will lead to a larger demand for electric-
ity for air jconditioning and, hence, to
increased SO2 emissions, and to a more
rapid oxidation of the SO2 and NOX to
sulfate and nitrate ions. Also, altered
precipitation patterns and changed
cloud cover can potentially change the
importance of aqueous phase oxidation
and long range transport processes, as
well as the impacts on aquatic systems
and forests.
Recommendations
1. Implicit recommendations were
derived consistent with the following
four general types of responses to
these problems:
• Understanding—We can continue
to develop the basic science and
measurement programs needed to
determine the magnitude and
timing of environmental effects.
• Preventing—Many scientists be-
lieve that climate change cannot
be prevented: too much material
is already in the air and only lags in
the system (such as ocean turn-
over) are delaying the changes;
the changes will happen eventu-
ally.
• Limiting—There are questions
about the quasi-irreversibility of
the systems that suggest that op-
tions to limit the changes are diffi-
cult. The long lifetimes of some of
the species mean that if emissions
stopped now, it would require 30-
50 years for conditions to be re-
stored 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, noncritical uses of
Freonsi
• Adjusting—We can adjust to the
existence of the situation by ac-
counting for its existence in our ac-
tivities. This means that decision
makers at all levels should begin to
consider the impact of the proba-
ble changes in their policies and
strategies. There have been very
few policy impact analyses com-
parable with the level of scientific
modeling work done in the last few
years.
2. One of the challenges that EPA
should address is that of devising an
observational strategy and support-
ing validating studies to give the pol-
icy and scientific community a good
model for the continental U.S.
3. In the short term, EPA can build un-
derstanding and institutional capa-
bility. Furthermore, EPA should un-
dertake additional analyses to assure
that agency actions do not inadver-
tently speed up the rate of change. In
the long term, EPA should use cli-
mate scenarios in long-range trans-
port models; conduct synergistic ex-
periments (e.g., involving the impact
of CO2, increased UV-radiation, and
acid rain) on forests, crops, lakes,
and materials for the world of the
year 2020; and we should begin to
develop a risk methodology for the
global environment.
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Harvey E. Jeffries is with the University of North Carolina, Chapel Hill, NC27514.
Basil Dimitriades is the EPA Project Officer (see below).
The complete report, entitled "EPA Workshop on Global Atmospheric Change and
EPA Planning: Final Report," /Order No. PB 86-244 639/AS; Cost: $22.95.
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park. NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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