Science, and transportation united states senate

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I860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

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Figure 9. — The cumulative production of carbon dioxide since 1860 is compared

The similarity in the rates of increase (about 4 percent per year) produces

strong evidence that these two quantities are related. About 50 percent of the

fossil carbon flux apparently has been balanced, at least since 1958, by a

flow of carbon dioxide to such reservoirs at the world ocean and/or the land

biota (assumed 1860 atmospheric concentration equals 295 ppm) .

Source : Baes. C. F., et al. "The Global Carbon Dioxide Problem," Oak Ridge National

Laboratory, 1976. (ORNL-5194.)

Future levels of atmospheric carbon dioxide will depend primarily

on the rate of consumption of fossil fuel and to a lesser extent on land

use patterns and practices. With brief interruptions for two world

wars and the Great Depression, the production of carbon dioxide from

fossil fuels has increased with an annual rate of 4.3 percent. 33 If the use

of fossil fuels continues to grow at this present rate, the total carbon

dioxide injected into the atmosphere by man since 1860 wouM reach

300 parts per million by the year 2030, and the total concentration

would be equal to 595 parts per million. This assumes, of course, no

change in the average uptake by other reservoirs during this time.

Those energy scenarios that rely heavily on coal, especially for syn-

thetic oil and gas, yield estimated carbon dioxide concentrations of

33 4.3 percent per year provides an excellent fit to the data in figure 7.

168

about 100 years from now. Rotty and Weinberg (1977) discuss a

scenario by Niehaus in which nonfossil energy sources dominate soon

after 2000. Even in this case the annual emission of carbon dioxide

from fossil fuel peaks at about twice the present level in the year 2000

and tapers off thereafter; the atmospheric concentration nevertheless

reaches 475 parts per million by 2050. 34 ' 35 > 36 > 37 > 38

Sources and sinks for carbon dioxide

These extrapolations are based on certain assumptions, a critical

one being that the ocean and the biosphere will continue to absorb a

large fraction of the carbon dioxide in the atmosphere. Some ocean-

ographers see increasing evidence that the upper mixed layer of the

ocean, where most of the carbon dioxide is stored, is rapidly becoming

saturated, and if this were true, then it tends to reenforce the attain-

ment of relatively. high atmospheric carbon dioxide concentrations in

the next century. However, this prediction is far from certain, because

carbon dioxide absorption in the ocean could turn out to be greater than

expected because of mixing between ocean layers or other factors. 39

The problem is further complicated by a series of current appraisals

that suggest that the terrestrial biomass appears to be a net source of

carbon dioxide for the atmosphere. George M. Woodwell of the Marine

Biological Laboratory at Woods Hole, Mass., explains :

Over the past seven years several reviews of the world carbon budget have con-

firmed that there is an annual increase in the carbon dioxide content of [the

atmosphere] that is worldwide and is almost certainly man-caused. The source

of the carbon dioxide that is accumulating in the atmosphere has been commonly

assumed to be the combustion of fossil fuels. Because the amount of carbon diox-

ide accumulating in the atmosphere is * * * [about] half the total released from

fossil fuels, other sinks for carbon dioxide have been sought. The major sink is the

ocean, but mixing rates appear to be too low for the oceans to accommodate all

the carbon dioxide that is thought to be released in excess of that accumulating in

the atmosphere. The question of whether the terrestrial biota could be another

sjnk was raised in 1970 [at SCEP], and the assumption was made that the biota

might be a sink, especially in view of the stimulation of photosynthesis under

greenhouse conditions by enhanced concentrations of carbon dioxide. More re-

cently, the assumption that increased carbon dioxide in air stimulates photo-

synthesis worldwide has been questioned. So has the assumption that the biota

is a net global sink for carbon dioxide. A series of current appraisals suggests

that, quite contrary to the previous estimates, the biota is probably an addi-

tional source of carbon dioxide * * * as large as or larger than the fossil fuel

source. 40

Thus, the great puzzle is the basic stability of the global carbon

budget. Without better information on the behavior of the terrestrial

biosphere, it is difficult to say whether the biosphere is a sink or a

net source of carbon dioxide. If the biosphere is supplying more carbon

34 Baes, C. F.. Jr.. et al. "The Global Cnrbon Dioxide Problem," Oak Ridge, Tenn., Oak

Ridge National Laboratory. 1970. 78 pp. (ORNL 5194. )

* Lenkowski, Wil. "Carbon Dioxide: A Problem of Producing Usable Data." Chemical

and Engineering News. vol. 55, Oct. 17, 1977 : pp. 26-30.

;!0 Rotty, Ralph M.. "Energy and the Climate." Institute for Enerprv Analysis, Oak Ridge,

Oak Ridge Associated Universities. 1970. 28 pp. ( ORAU/IEA (M) 75-3.)

37 Rottv. R. M. and A. M. Weinberg. "How Long is Coal's Future," Climatic Change, vol. 1,

No. 1. March 1977 : op. 45-57.

3 * Rottv. Ralph M.. "The Atmospheric Carbon Dioxide Consequences of Heavy Dependence

on Coal." Institute for Energy Analysis, Oak Ridge Associated Universities, occasional

paper. 32 pp.. Nov. 14, 1977.

39 Anthes. Ricbard A.. Hans A. Panofskv. John J. Cnbir and Albert Rango, "The Atmos-

phere." Columbus. Charles E. Merrill Publishing Co., 197r>, p. 204.

in YVoo''" eii (i. M.. ef al., "The Biota and the World Carbon Budget." Science, vol. 199,

Jan. 13, 1978. pp. 141-146.

169

dioxide than it is absorbing, then the behavior of the ocean must be

be an even more effective sink for carbon dioxide than previously sur-

mised. Thus, there is a need for intense examination of the flux of

carbon into the ocean. The ability of the world ocean to act as a carbon

dioxide sink is large, but the rate of possible sequestering of carbon is

the important factor. One possibility is that biotic mechanisms in the

ocean are more effective than has been assumed in transferring fixed

carbon from the mixed (near-surface) Jayers of the ocean into deep

ocean waters. Before an estimate can be made with confidence of what

fraction of the carbon dioxide from fossil fuels remains in the atmos-

phere, a better understanding of the roles of both the biosphere and

the world ocean in the carbon cycle is necessary. 41, 42 - 43

Atmospheric effects of increased carbon dioxide levels

A change in the carbon dioxide content of the atmosphere upsets

the Earth's radiation balance by holding back departing infrared light.

All things being equal, if no other change were to occur in the system,

the net amount of energy accumulated by the Earth would raise its

surface temperature until the enhanced infrared emission reestab-

lished balance between incoming and outgoing radiation. The problem,

however, is greatly complicated by the fact that other changes would

certainly take place. For example, if the Earth's temperature rises,

the water vapor content of the atmosphere is likely to rise. More water

will have the same effect as more carbon dioxide creating positive feed-

back in the system and hence forcing temperatures to climb even higher.

A rise in water vapor would quite likely increase the fraction of the

globe covered by clouds. Such an increase would cause the amount of

primary solar radiation absorbed by the Earth to fall. Some combina-

tion of increased temperature and cloudiness will balance the enhanced

absorption of infrared radiation by the added carbon dioxide and

water vapor.

Implications of increasing atmospheric carbon dioxide concentrations

The possibilities and implications of a continued rise in the atmos-

pheric carbon dioxide concentration were reviewed in a special report

entitled ''Energy and Climate.*' released by the National Kesearch

Council (NRC) on July 25, 1977. 44

The most complete, though still imperfect, climate models suggest

that a doubling of the amount of carbon dioxide in the atmosphere,

relative to its present amount, would increase the average annual

temperature of the lower atmosphere at middle latitudes by about 2.4°

to 2.9° C (4.3° to 5.2° F), depending on which model is used to derive

the estimated temperature change.

Based on one climate model in which the hydrologic cycle is modeled

in detail along with other aspects of climate behavior, a doubling of

carbon dioxide has been calculated to result in about a 7 percent increase

41 Bolin, Bert. "Changes of Land Biota and Their Importance for the Carbon Cycle ; The

Increase of Atmospheric Carbon Dioxide Mav Partlv Be Due to the Expansion of Forestry

and Agriculture." Science, vol. 196, May 6. 1977. pp. 613-615.

"2 Siegreuthalpr. U and H. Oeschsrpr. "Predicting Future Atmospheric Carbon Dioxide

Levels." Science, vol. 199, Jan. 27, 1978, pp. 388-395.

43 WooriwHl. Geo-cre M., "The Carbon Dioxide Question," Scientific American, vol. 238,

Janvary 1978. pp. 34-43.

44 National Research Council. Geophysics Research Board, "Energy and Climate," Wash-

ington, National Academy of Sciences, 1977, 281 pp.

170

centrated in higher latitudes. A general retreat of snow and sea ice

cover, by perhaps as much as 10 degrees of latitude, could result in

the Arctic regions. The extent of such changes in the Antarctic, how-

ever, has not been determined. The temperature rise is greater by a

factor of three or four in polar regions than the average temperature

change for the world as a whole. For each further doubling of carbon

dioxide, an additional 3° C increase in air temperature is inferred. This

would mean that should the carbon dioxide concentration approach

four to eight times preindustrial levels, and increase in global mean air

temperature of more than 6° C (11° F) could be realized — at which

time Earth would be experiencing temperatures warmer than those at

any time in the last million years. 45

Implications of a climatic warming

The implications for man-induced climatic warming are particularly

far-reaching for agriculture, according to the NRC report. The global

picture presented by the report is one dominated by the f orementioned

gradual increase in mean air temperatures, with a concomitant shift-

ing of agricultural zones, altered rainfall patterns and other major

changes. Worldwide average annual precipitation could increase,

which, at first glance, would seem to benefit agriculture. The accom-

panying higher air temperature, however, would raise the rate of

evapotranspiration from cultivated lands, and part of the benefits

from the additional water supply could be lost. In some regions,

evapotranspiration might exceed the increase in precipitation; in

others, the reverse might be true. At higher latitudes, there would be

a longer frostf ree growing season than at present, and the boundaries

of cultivation could be extended northward in the Northern Hemi-

sphere. Attendantly, summer temperatures might become too high for

full production of middle-latitude crops such as corn and soy beans

grown in Iowa, Illinois, Indiana, and Missouri, and it might be

necessary to shift the Corn Belt toward the north where less produc-

tive soils are encountered. Generally speaking, warmer temperatures

would result in a poleward movement of agroclimatic zones. As the

authors of the NRC report state :

The most serious effects on agriculture would arise not from changes in global

average conditions but from shifts in the location of climatic regions and changes

in the relationships of temperature, evapotranspiration, water supply, cloudi-

ness, and radiation balance within regions. Present cropping patterns, crop vari-

eties, and farming technology in different climatic regions are based on cumula-

tive experience over many years in the selection of appropriate crop species and

varieties for each region and in adapting both the plants and their physical

environment to each other in as nearly an optimal fashion as possible. These

adaptations have remained fairly satisfactory over the relatively nam nge

of climatic changes that have occurred in the historic past. But large el in

climatic relationships within regions such as might be brought abo a

doubling or quadrupling of atmospheric carbon dioxide would almost c _ily

exceed the adaptive capacity of crop varieties grown at present. 46

The potential global warming trend associated with increasing con-

centrations of atmospheric carbon dioxide could increase desertifica-

tion, 47 although there is not conclusive evidence for this possibility.

*Mbid., pp. 4, 5.

47 The awkward word "desertification" often refers to the process by which existing deserts

spread but the term also may refer to the creation of desertlike conditions such as those

which developed during the 1930's dust-bowl years in the North American Great Plains.

171

release of carbon dioxide could change desert conditions in unexpected

ways and even increase agricultural potential in some cases. Authors

of the NRC report concede the present state of ignorance on the

subject :

The most serious effects of possible future climatic changes could be felt along

the boundaries of the arid and semiarid regions in both hemispheres. We need to

be able to estimate whether these belts of aridity and semiaridity will move

toward or away from the poles and whether they will expand or contract in

area. 48

The effect of manmade or of natural climatic alteration of desert-

areas is not clear. The advancement of desert conditions into agri-

cultural areas in Africa and elsewhere has been documented during

the past decade, and although rainfall patterns with associated wet

and dry climates are controlled mainly by the general atmospheric

circulation, human activities can have a marked effect on local desert

conditions, even possibly intensifying the process of desertification and

thereby compounding the problem. In particular, excessive ploughing

of dry land or overenthusiastic introduction of livestock and expan-

sion of cultivated areas, during wet periods, into marginal lands causes

destruction of soil-protecting vegetation. During ensuing dry periods,

these marginal lands, with their natural protective cover destroyed by

cultivation and overgrazing, suffer loss of, or a decline in, the quality

of soil. As this occurs over a large region, the bare dry ground, its

reflectivity altered, now acts to intensify the natural climatic condi-

tions which sustain the desert. 49

Carbon dioxide and future climate: the real climate versus "model

climate''''

In the final analysis, it is well to remember that it cannot be asserted

that a doubling of carbon dioxide in the real world would have the

same effects on real climate as a simulated doubling of carbon dioxide

in climate models would have on "model climate." This caveat is in

order because no climate model is altogether realistic in its description

of the real climatic system, and because some of the physical processes

that operate in the real climatic system cannot yet be simulated at all

in climate models. Comments J. Murray Mitchell, Jr. :

No climate model on which the above conclusions [regarding climatic warm-

ing] are based is capable of developing its own cloud systems in a realistic

way : most models must be instructed before hand where the clouds are assumed

to exist, and the clouds remain there unchanged throughout the computer

experiment using the model. We should be wary of this, because if the cloudi-

ness were to change in the real world along with a carbon dioxide change,

then the role of clouds in affecting the temperature of the Earth might sig-

nificantly alter the net temperature effect of the carbon dioxide change as

inferred from models that assume fixed cloudiness. 50

the model is allowed to adjust cloudiness along with other weather

variables as the calculation proceeds. Early indications are that

Some preliminary model experiments have been attempted at the

National Oceanic and Atmospheric Administration's (NOAA) Geo-

physical Fluid Dynamics Laboratory in Princeton, N.J., in which

48 National Research Council, Geophysics Research Board, op. cit., p. 14.

48 Ibid.

50 Mitchell, J. Murray, Jr., "Carbon Dioxide and Future Climate," p. 9.

172

experiments using models with fixed cloudiness.

Altogether, the experience with climate models suggests that their

use in evaluating the magnitude of temperature changes associated

with changes of atmospheric carbon dioxide leads to results that are

likely to approximate reality fairly closely. Models may be overesti-

mating the temperature and other climatic effects of carbon dioxide

changes by as much as a factor of two. On the other hand, it is

equally likely that they may be underestimating the effects by a

factor of two. In balance, the model results to date warrant being

taken as an unprejudiced and credibly realistic approximation to

reality. 51

OZONE DEPLETION

The concern that man's activities could in some fashion change the

stratosphere first emerged as a public issue during the debate on the

American SST in 1969. The American SST program was, at that

time, almost a decade old and was approaching its final phase when

it was challenged by a coalition of more than 30 environmentally

oriented organizations. The environmentalists contended that the

SST, flying in the stratosphere, would contaminate the stratosphere

and alter its characteristics. The dominant concern was that water,

created as a product of fuel combustion, would interact with the

stratospheric ozone and destroy it.

Concerns regarding ozone destruction

Ozone (0 3 ) exists everywhere in the atmosphere and reaches a

maximum concentration at around 80,000 feet. It is created, as well

as destroyed, by the interaction of ultraviolet light from the Sun with

oxygen molecules in the upper atmosphere. Most of the ozone is

created in the Tropics and is dispersed from there toward both poles.

Due to the destructive action of sunlight and to the atmospheric

transport systems, the Tropics, where most of the ozone is made, have

the least dense coverage of ozone. Ozone density increases in the

temperate zones and reaches its maximum density in the polar regions.

Ozone density over a given spot on Earth may vary as much as 25

to 30 percent on a given day and as much as 300 percent throughout

the year depending on the season. Ozone density measurements have

shown that the Northern Hemisphere of the Earth has a slightly

denser coverage than the Southern Hemisphere.

The importance of the ozone content of the upper atmosphere

centers on the fact that the ultraviolet light that creates ozone is

absorbed in the process. These wavelengths of ultraviolet light are

damaging to life of all sorts if the intensity is too great. It should be

noted that some ultraviolet light is required by animal life to produce

vitamin D which gives protection against rickets.

In the debate over the American SST, it became clear that neither

side had enough data on the stratosphere to refute the other. Despite

this, the debate remained lively for more than a year and was finally

terminated by the congressional decision to cancel the SST program

and to initiate programs to study the upper atmosphere and in par-

ticular, its ozone.

51 Information gleaned In a session on "climatic futures" at the 1978 annual meeting of

the American Association for the Advancement of Science in Washington, D.C., Feb. 17,

1978.

173

determine whether or not the stratospheric flight constituted a threat

to the Earth's environment. Responsibility for the study was given to

the Department of Transportation and was called the "Climatic Im-

pact Assessment Program" (CIAP). 52 The theoretical mechanisms

which indicated that water, created from the combustion of fuel, would

mix with and destroy ozone appeared to be reasonable and meritorious

of serious study. Early in the CIAP, however, actual measurements of

ozone density in the stratosphere in volumes of air which were per-

meated by the plume from jet engines, were made. These measurements

showed that ozone density seemed to increase subsequent to the injec-

tion of water vapor. Why this occurs is not yet understood, but the test

provided adequate information to conclude that water vapor injected

into the stratosphere would not constitute a danger to the ozone.

During the conduct of the CIAP program, other papers began to

appear which described a variety of heretofore unconsidered theoreti-

cal ways in which man's activities could adversely effect the ozone

density in the stratosphere. The atmosphere of the Earth is about 80

percent nitrogen and 20 percent oxygen. The oxygen used in the com-

bustion process is therefore accompanied by a large amount of nitro-

gen. The heat of combustion causes the formation of several oxides of

nitrogen (NO x ). Theoretical mechanisms were proposed which pre-

dicted that the NO x formed in the stratosphere by a jet engine would