#.

Lo p-

GENERAL T7A

lrEtt0Rtil0ur
-a
....t !t'.,
ro T. K.''lKett
:

,

FRoM HENRYSHAW

oare December 18.

1980

is the "C02 Greenhouse Effect"
technological forecast. I have added the
Attached

items you suggested on 12fi6180. Pat McCall
has not had a chance
He

will

to review this draft.

contact you directly

if

he has any

corments.

HS/lw

Attachment

cc: P. P. McCall
H. C.

Hayworth

lf. N. wEtNf:iiG
ulu 3 0 tggo

 Exxon Research and Engjneering Company's Technological Forecast
C02 Greenhouse Effect
by
H. Shaw and P. P. McCall

Current Status
The bu'ild-up of C02 in the atmosphere has been monitored continuously at the National Oceanic and Atmospheric Adm'inistration's 0bother places since
servatory at Mauna Loa, Hawai'i and periodicaliy in
.1957-.1979
1957. In addition to observing a trend between
that showed
atmospheric C02 increasing from 3.l5 to 337 ppm, Keeling and others also
observed a seasonal variability ranging from 6 to l0 ppm between a low
at the end of summer growing season (due to photosynthesis) and a high
at the end of the winter (due to fossil fuel burning for heat, and biomass decay). There is little doubt that these observations indicate a
growth of atmospheric C02 (See Figure 1). It is also believed that the
growth of atmospheric C02 has been occuring since the middle of the past
century j.€., coincident with the start of the Industrial Revolution.
There is, however, great uncertainty on whether the atmospheric C02 concentration prior to the Industrial Revolution was 290-300 ppm or 260-270
ppm-

relative contributions of

biomass oxidation (mainly due to
deforestation) and fossil fuel combustion to the observed atmospheric
C02 increase are not known. There are fairly good indications that the
annual growth of atmospheric C02 is on the order of 2.5 to 3.0 Gt/a ot
carbon and the net quantity of carbon absorbed by the ocean is similarly
2.5 to 3 Gt/a. Thus, these two sinks (atmosphere and ocean) can account
for the total fossil carbon burned which is on the order of 5-6 Gt/a and
does not allow much room for a net contribution of biomass carbon. Yet,
highly respected scientists, such as Woodwell, Bolin and others have
poitulated a net bjomass contribution to atmospheric C02 that range from
'l to perhaps 8 Gt/a of carbon. The rate of forest clearing has been
of the-exlsting area. Forests occupy about
estimatqd 4t 0.5 to I .5%/a
.l50
x l06kmz of cont'inental land, and store
50 x l06km2 out of about
about 650 Gt of carbon. One can easily see that if 1% of the worlds
The

forests are cleared per year, then this could contribute 6.5 Gt of carbon to the atmosphere. Even if reforestation were contributing significantly to balancjng the C02 from deforestat'ion, the total carbon stored
in new trees would be only a small fraction of the net carbon emitted.
It should be noted, however, that the rate of forest clearing and reforestation are not known accurate'ly at thjs time. If deforestation is
indeed contributing to atmospheric C02, then another sink for carbon
must be found and the impact of fossjl fuel must be considered in the
context

of

such a sink.

 -2Figure 2, taken out of a recent DOE publication summarizes the
fluxes and reserviors for the carbon cycle. Note that a deforestation
flux of 0 to 2 Gt/a and a net flux to the oceans of 4 Gt/a are assurned.
Thus, the carbon flux to the atmosphere is 6 Gt/a of fossil fuejs, and 2
Gt/a deforestation, whjle 4 Gtla returned to the ocean resulting in a
50% carbon retention rate in the atmosphere. One of the major objectives
of the Exxon Research and Engineering Company project to measure C02 in
the oceans using tankers is to clarify and quantify the role of the
oceans as the ultjmate sink for C02.
Projections of scientists active in the area indicate that the
contrjbutjon of deforestation which may have been substantiai in the
past, will diminish in comparison to the expected rate of fossil fuel
combustion in the future. A number of scientists have postuiated that a
doubling of the amount of carbon dioxide in the atmosphere could occur
as early as 2035. Calculations recently completed at Exxon Research
indicate that using the energy projections from the CONAES study and the
World Energy Conference, a doubling of atmospheric C02 can occur at
about 2060. If synthetic fuels are not developed, and fossi I fuel needs
are met by petroleum, then the atmospheric C02 doubl ing time would be
delayed by about 5 years to 2065. It is now clear to mnst people working in the area that the doubling time will be much later in the future
that previously postulated because of the decreasing rate of fossil fuel
use.

Description of potential impact on weather, cl imate, and land availability
The most widely accepted calcu.lations carried on thusfar on
the potential impact of a doub)ing of carbon dioxide on climate indicate
that an increase in the global average temperature of 3+1.50C is most
likely. Such changes in temperature are expected to occur with uneven
geographic distribution, with greater warming occuring at the higher
latitudes i.e., the polar regions. This is due to the presumed change
'in the reflectivity of the Earth due to melting of the ice and snow
cover (See Figure 3). There have been other calculations on a more
limited scale by a number of climatologjsts which project average temperature increases on the order of 0.25oC for a doubiing of C02. These
calculations are not held jn high regard by the scientific community.
Figure 4 summarizes the results presented in the literature on the possible temperature increase due to various changes in atmospheric C02

concentrat i on.

The area of climate modeiing was recently studied by a comnittee of the National Research Council, chaired by Jules G. Charney of
MIT, and the conclusions are summarized in their booklet titled ,'Carbon
Dioxide and Climate: A Scientific Assessrnent." This National Research
Counci l study concluded that there are major uncertainties jn these
models in terms of the timing for a doubling of C02 and the resu)ting
temperature increase. These uncertainties center around the thermal-

 ?

capacjty of the oceans. The oceans have been assumed to consist of a
relatively thin, well mixed surface layer averaging about 70 meters in
depth in most of the general circulation mode1, and that the transfer of
heat into the deep ocean is essentially infinitely slow. The Charney
panel feels, however, that the amount of heat carried by the deep ocean
has been underestimated and the oceans will slow the temperature increase due to doubling of atmospheric C02. The Charney group estirnated
that the delay in heating resulting from the effect of the oceans could
delay the expected temperature increase due to a doubling of C02 by a
few decades.
Along with temperature increase, other climatologicai factors

that are expected to occur will include

rainfall,

uneven

global distributjon of

and increased evaporation. These disturbances in
the existing g1oba1 water distributjon balance will have dramatic impact
on soil moisture, and in turn, on agriculture. The st ate -of -the -art in
cl imate model.ing allows only gross g'lobal zoning while some of the expected results from temperature increase of the magnitude indicated are
quite dramatic. For exampie, areas that 4,000 to 8,000 years ago in the
Altithermal period (when the globa1 average temperature was some 2oC
higher than present) were deserts, may in due time return to deserts.
Conversely, sone areas which are deserts now were formerly agricultural
regions. it is postulated that part of the Sahara Desert in Africa was
quite wet 4,000 to 8,000 years ago. The American Midwest, on the other
hand, was much drier, and it is projected that the Midwest will again
become drier should there be a temperature increase of the magnitude
postuiated for a doubling of atmospheric C02 (See Figure 5).

increased

In addition to the effects of climate on the g1obe, there are
particularly dramatic questions that might cause serious global
problems. For example, if the Antartic ice sheet which is anchored on
1and, shouid melt, then this could cause a rise in the sea level on the
order of 5 meters. Such a rise would cause flooding in much of the U.S.
East Coast including the state of Florida and Washington D.C, The melting rate of polar ice is being studjed by a number of glaciologists.
Estimates range for the melting of the West Antartjca ice sheet from
hundreds of years to a thousand years.
some

In a recent AAAS-DOE sponsored workshop on the environrnental
societal consequences of a possible C02 induced climate change,
other factors such as the environmental effects of a C02 growth rate on
the less managed biosphere were studied. For example, lhe impact of a
and

temperature increase and a higher atmospheric C02 concentration on weeds
and pests was considered. The general concensus was that these unmanaged
species would tend to thrive with increasing average globai temperature.
The effects of atmospheric C02 growth on the managed 6iosphere such as
in agriculture would also tend to benefit from a C02 growih. It turns
out that c02 can fertilize agriculture, provided the other key nutrients,
phosphorous and nitrogen, are present in the right proportion-s, Agr.i-

 -4cultural water needs can be met by new jrrigation techniques that require less water. In addition, with highest C02 and higher temperature
condjtions, the amount of water that some agricultural plants may need
will be reduced. It is expected that bjoscience contributjons could
po'int the way for dealing with cl'imatological disruptions of the magnitude indicated above.

In terms of the societal and institututional responses to an
increase in C02, it was felt that society can adapt to the jncrease in
C02 and that this problem is not as significant to mankind as a nuclear
holocaust or world famine. Fina' 1y, in an analysis of the issues associated with economic and geopo'l'itical consequences, it was felt that
society can adapt to a C02 increase within econom'ic constraints that
will be exjsting at the time. Some adaptive measures that were tested,
for example, would not consume more than a few percent of the gross
national product estimated in the middle of the next century.
Major Programs Underway
The DOE which is acting as a focal point for the U.S. government in this area is considering two reports to the scientific community
and to the policy makers. The first one, summarizing five years of
study is due in 1984, and the second one in 1989. The current plan is
to spend approximately 10 years of research and assessment prior to
recornmending policy decisions in thjs area which impact great'ly on the
energy needs and scenarios for the U.S. and the world. The national
program on C02, environment and society is summarized in Figure 6.

Projections on When General

Concensus Can be Reached

It is antic'ipated by most scientists that a general concensus

will not be reached until

such time as a significant temperature increase can be detected above the natural random temperature fluctuations
in average global climate. The earliest that such discreet signals will
be able to be measured js after the year 2000. However, depending on
the actual globa'l energy demand and supply, it is possible that some of
the concerns about C02 growth due to fossil fuel combustion will be
minimized jf fossil fuel use is decreased due to hjgh price, sbarcity,
and unavailability. Figure 7 illustrates the behavior of the mean global
temperature from'1850 to the present contained within an envelope sca'led
to include the random temperature fluctuations.

Future Scenarios and Their Consequences For

Exxon

A number of future energy scenarios have been studied in relation to_tlq C9a prob'lem. These include such unlikely scenarios as stopping all ftissil fuel combustion at the l9B0 rate, looking at the de'lay'
in doubl'ing time and maintaining the pre-I973 fuel growth rate. Othei

studies have investigated the mirket fenetration of-non-fossil fuel

 -5technologies such as nuclear, and its impact on C02. It should be noted,
however, that a new technology in a competitive scenario would need about
50 years to penetrate and achieve roughly half of the total market. Thus,
even if solar or nuclear were to be considered viable alternatives, these
would not really displace fossil fuel power generation for the next 50
years or so, and C02 growth would have to be estimated based on realistic
market displacement of the fossil fuel technologies. All of these studies
tend to give a range of deviations on the order of 50 years, indicating
aC02 doubling time.that might !e as early as 2035 (for a fossil fuel
growth rate of 4.3/"), to a doubling time occuring by about 2080 resulting
from scenarios which assumed fossi I fuel growth rates of 1 to 2%. Synthetic
fuels will cause minor perturbations on the projected atmospheric C02
growth rates in the next century.

 FIGURE I

Trend

in

Atmospheric C02 Concentrations
at Mauna Loa (Hawai j )

340

340

(Based on Scrlpps 1974 manomelrlc calibrailon)

o
E

335

I
o

tt
e 330
CL

330

c
c
o
o

c

o
a
c
o

I

325

325

o
o

E
x

320

o

o

c

ao
od

I

Ol

315

310

3't 5

1958 1959 1960 1961 1962 1963 1964 1965 1966 1967

Year

1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980

310

 FIGURE 2

Exchangeable Carbon Reservoirs and Fluxes

Atmosphere
(710) 335 ppm

Combustion

of GOz

Photo-

0:2
I

\l

(650) Biota

Surf ace

P5000)

Fossil Fuels
and Shale

(

)=

(39,000)

Terrestrial
Biosphere

lntermediale,

Deep Ocean
and Sediments

Oceans

Size ol Carbon Reservoirs in Billions of Metrlc Tons of Carbon

Fluxes (airows)

Exchange of Carbon Between
= Metric
per

Tons of Carbon

Reservolrs in Billions ol
Year

I

 FIGURE 3

Temperature Change (oC) Due to
Doubl jng COp Concentrations

COz-Standard

Stratosphere

I

@

Tropopause

I

o
5

:ct

.=

=

\\

---.*_- _-nn-j

'7r*7-2-*:L\ f900

800

600

-+3

500

400

200

300

Latitude
Decrease

in

100

Temperature

 -9FIGURE 4

of the Change in Global Average Surface Temperature
to various changes !n c02 concentration. shading shows

Estimates
Due

Present Range of Natural Fluctuations.
6

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 FIGURE 5

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 FIGURE 6

A National Program on Carbon Dioxide,
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-12FIGURE 7

Range

of Global Mean Temperature From 1850 to the Present with
Response to Increasing C02

the Projected Instantaneous Climatic
Concentrations.

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1900

1950

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2100

Year

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