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19
Introduction
Various technologies and policy options have the potential to
mitigate greenhouse warming. The Mitigation Panel was given the
task of evaluating the effectiveness of these interventions, with
the following specific charge:
• The panel should examine the range of policy
interventions that might be employed to mitigate changes in the
earth's radiation balance, assessing these options in terms of
their expected impact, costs, and at least in qualitative terms,
their relative cost-effectiveness.
• Preliminary evaluation will help identify policy
interventions for closer examination. These might include reducing
emissions in primary energy production or industrial processes,
transportation vehicles and systems, or agricultural processes.
They might include policies aimed at reducing energy consumption or
changing practices in agriculture, silviculture, or general land
use. Novel global system interventions, such as removal of
greenhouse gases from the atmosphere, blocking of incident
radiation, or altering of the earth's albedo, should not be
excluded.
• Attention should be given to factors affecting the design
and implementation of potential programs at the international and
regional levels, including, as explicitly as feasible,
organizations that should be involved and practical impediments. In
performing this task, the panel should take into account any major
relationship between the particular intervention and ecological or
other problems apart from global climate change.
The panel defines "mitigation policy" as including programs and
specific interventions that might reduce either the rate at which
the radiative balance is changing or the ultimate level at
equilibrium, assuming one is reached. Mitigation policies include
not only interventions designed to reduce the emission of
greenhouse gases but also actions such as reforestation (or
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Representative terms from entire chapter:
gas emissions
Page 158
reducing deforestation), removal of radiatively active gases
from the atmosphere, and altering the earth's albedo in ways that
affect the earth's radiative balance.
Sources of Greenhouse Gas
Emissions
This section provides a very brief summary of the magnitudes and
sources of greenhouse gas emissions in order to suggest targets for
mitigation strategies and some indication of the magnitude of the
effort required. It is not intended to be a critical review, but
relies on the recent summary compiled by the Intergovernmental
Panel on Climate Change (1990, 1991). More information is available
in the report of the Effects Panel (Part Two).
The greenhouse gases include carbon dioxide (CO2), chlorofluorocarbons (CFCs), methane
(CH4), nitrous oxide (N2O), ozone (O3), and water vapor. Although water vapor
continually cycles through the atmosphere, if there is a change in
atmospheric temperature, the mean water vapor concentration could
change and provide an important positive feedback (i.e., magnify
the temperature change). Other gases such as carbon monoxide (CO)
and nitrogen oxides (NOx) are
involved in chemical reactions in the atmosphere and affect the
concentrations of greenhouse gases (in this case, O3). Greenhouse gas emissions come from
both anthropogenic (man-made) and natural sources (such as CH4 from wetlands). Table 19.1 lists the
primary greenhouse gases, the anthropogenic sources, and the
relative contribution of each gas toward greenhouse warming. As
shown in this table, CO2 is the
single most important greenhouse gas worldwide, but others also
make a significant contribution.
Table 19.2 shows the current rates at which greenhouse gases are
increasing worldwide. Figure 19.1 breaks down the current worldwide
contributions to radiative forcing by source sector emissions
during the 1980s. As shown here, energy use that generates
emissions of CO2 and other
greenhouse gases is the major greenhouse emission source. Table
19.3 shows a recent projection of global emissions from different
sources for the years 2000, 2015, and 2050. As CFCs are phased out
(presumably), under present international agreements, emissions
from energy use are likely to dominate the anthropogenic influence
on greenhouse warming.
Even though CO2 contributes about
half of the radiative forcing from increased atmospheric
concentrations of greenhouse gases, Table 19.4 shows that once in
the atmosphere, each molecule of the other greenhouse gases
contributes more to global warming than does each molecule of
CO2. For example, CFC-11 has, per
molecule, 12,400 times the capacity of CO2 to trap heat.
Worldwide, the United States is at present the largest emitter
of greenhouse gases (World Resources Institute, 1990). As shown in
Figure 19.2, the use of energy in the form of coal, oil, and
natural gas is the largest
Page 159
TABLE 19.1 Global Greenhouse Gases with Their
Anthropogenic Emission Sources
Greenhouse Gas
Greenhouse Gas Contribution During the 1980sa (%)
Anthropogenic Emission Sources
Carbon Dioxide
56
Combustion of coal, oil, natural gas, and wood for
use in electric utilities and for industrial, residential, and
commercial use
Combustion of gasoline, diesel fuel, and other
hydrocarbon fuels for automobiles, trucks, trains, aircraft, and
ships; calcining of limestone during cement manufacture
Deforestation, which leads to a net decrease in
the mass of terrestrial organic matter
Methane
15
Decomposition of waste in landfills
Fossil fuel use, which results in emissions during
coal mining, during exploration, production, and transportation of
oil and natural gas, and via incomplete combustion of natural
gas
Agricultural sources, including biomass burning,
animal husbandry (cattle), and rice cultivation
Chlorofluorocarbons
24
CFCs, which are used to make rigid and flexible
foam, and as aerosol propellants, refrigerants, and industrial
degreasers
Halons, which are used in fire extinguishers and
as sterilants for some medical applications
Nitrous oxide
5
Agricultural biomass burning, including use of
wood as a fuel and forest clearing
Use of nitrogenous fertilizers and probably
inadvertent fertilization through atmospheric nitrate
deposition
Tropospheric ozone
—
Generated from nitrogen oxides and carbon monoxide
emitted
aThe
greenhouse contribution shown is the fractional contribution to the
greenhouse gas alteration of the earth's radiation balance due to
atmospheric concentration during the 1980s. The percent
contribution is based on data from the IPCC Working Group I report
(Intergovernmental Panel on Climate Change, 1990). Greenhouse gas
emissions come from both anthropogenic (man-made) and natural
sources (such as methane from wetlands). The contribution of
tropospheric ozone to greenhouse warming is unknown at this time,
according to the IPCC.
Page 160
TABLE 19.2 Key Greenhouse Gases Influenced by Human
Activity
CO2
CH4
CFC-11
CFC-12
N2O
Preindustrial atmospheric concentration
280 ppmv
0.8 ppmv
0
0
288 ppbv
Current atmospheric concentration (1990)a
353 ppmv
1.72 ppmv
280 pptv
484 pptv
310 ppbv
Current rate of annual atmospheric
accumulation
1.8 ppmv (0.5%)
0.015 ppmv (0.9%)
9.5 pptv (4%)
17 pptv (4%)
0.8 ppbv (0.25%)
Atmospheric lifetime (years)b
(50–200)
10
65
130
150
NOTES: Atmospheric lifetimes are computed as the
ratio of the atmospheric burden to net annual removal, which is
estimated as emissions less atmospheric accumulation. Net annual
emissions of CO2 from the biosphere
not affected by human activity are assumed to be small, as are
volcanic emissions. Release and uptake from the biosphere not
affected by human activity are included under emissions deriving
from human activity. Emission estimates of human-induced emissions
from the biosphere are controversial.
Ozone has not been included in the table because
of lack of precise data. Here, ppmv = parts per million by volume;
ppbv = parts per billion by volume; and pptv = parts per trillion
by volume.
aThe 1990
concentrations have been estimated on the basis of an extrapolation
of measurements that go through 1988 or 1989, assuming that the
recent trends remained approximately constant.
bFor each
gas in the table, except CO2, the
"lifetime" is defined as the ratio of the atmospheric content to
the total rate of removal. This time scale also characterizes the
rate of adjustment of the atmospheric concentrations if the
emission rates are changed abruptly. CO2 is a special case because it is a
thermodynamically stable gas that equilibrates with oceanic and
biospheric processes. The lifetime shown does not indicate the
lifetime of the gas molecules, but rather of the perturbation of
atmospheric concentrations.
SOURCE: Intergovernmental Panel on Climate Change
(1990). Reprinted by permission of Cambridge University Press.
anthropogenic source of CO2
emissions in the United States. Cement production, gas flaring, and
land use change are relatively minor sources. Table 19.5 shows the
history of U.S. emissions of CO2
since 1950, indicating the U.S. percentage has been cut in half
over the last 30 years, although the total has almost doubled. The
major sources of CH4 emissions
(Figure 19.3) are solid waste (gas emissions from landfills),
natural gas pipeline
Page 161
FIGURE 19.1 Estimated global contribution to
radiative forcing by sector, 1980 to 1990.
SOURCE:
Intergovernmental Panel on Climate Change (1991).
leakage and livestock. The emissions of N2O are much more difficult to estimate,
and the principal cause of its increasing atmospheric concentration
is unknown, but a rough approximation puts these emissions at
approximately1.4 Mt/yr.1 This is
determined by taking worldwide N2O
emissions and scaling those emissions by the land area of the
United States.
With a variety of greenhouse gases being emitted to the
atmosphere, it would be useful to have a single index of the
relative greenhouse impact of the various gases. This would allow
comparison of the relative climatic benefits of mitigation measures
that address the emissions of different gases or measures that
reduce emissions of one gas at the expense of increasing emissions
of another (e.g., if changing the working fluid in a refrigeration
system results in a less energy-efficient refrigerator).
Ultimately, such an index might also let us understand the relative
importance of the emissions of gases that are not themselves
greenhouse gases but that because of their involvement in chemical
interactions in the atmosphere influence the abundance of
greenhouse gases. Because such an index would have to involve not
only the infrared absorptive capacities, concentrations, and
concentration changes of individual gases, but also their spectral
overlaps and atmospheric residence times, exact values will be
scenario dependent. A single index that meets all of our needs may
not even exist. It is clear that the
Page 162
TABLE 19.3 Global Greenhouse Gas Emissions from Human
Activities
Projections (Mt/yr)a
1985 Emissions (Mt/yr)
2000 Emissions
2015 Emissions
2050 Emissions
CO2emissionsb
Commercial energy
18,854 (86)
25,633 (87)
33,508 (89)
57,168 (92)
Tropical deforestation
2,628 (12)
3,241 (11)
3,388 (9)
3,728 (6)
Other
438 (2)
589 (2)
753 (2)
1,243 (2)
TOTAL
21,900
29,463
37,650
62,139
CH4 emissionsc
Fuel production
58 (18)
88 (22)
124 (26)
228 (32)
Enteric fermentation
74 (23)
96 (24)
110 (23)
156 (22)
Rice cultivation
109 (34)
124 (31)
138 (29)
171 (24)
Landfills
29 (9)
40 (10)
48 (10)
100 (14)
Tropical deforestation
19 (6)
24 (6)
24 (5)
28 (4)
Other
29 (9)
28 (7)
33 (7)
36 (5)
TOTAL
320
400
477
711
CFC-11 and CFC-12 emissionsd
TOTAL
0.64
0.84
0.76
0.83
N2O emissionse
Coal combustion
1.0 (25)
1.5 (26)
2.0 (29)
3.2 (36)
Fertilizer use
1.5 (38)
2.6 (43)
3.1 (44)
3.7 (41)
Gain of cultivated land
0.4 (10)
0.3 (8)
0.6 (8)
0.5 (6)
Tropical deforestation
0.5 (13)
0.4 (11)
0.7 (10)
0.8 (9)
Fuel wood and industrial biomass
0.2 (5)
0.2 (4)
0.2 (3)
0.2 (2)
Agricultural wastes
0.4 (10)
0.5 (8)
0.5 (7)
0.5 (6)
TOTAL
4
6
7
9
NOTE: Numbers in parentheses are percentages of
total.
aMt =
megatons = million metric tons.
bProjection based on U.S. EPA (1989) Rapidly Changing
World Scenario; assumed average annual growth rate = 1.6
percent.
cProjection based on U.S. EPA (1989) Rapidly Changing
World Scenario; assumed average annual growth rate = 1.2
percent.
dCFC
emission projection (from EPA) assumes no further controls beyond
original Montreal Protocol; assumed average annual growth rate =
0.4 percent.
eNitrous
oxide projections (from EPA) assume an average annual growth rate
of 1.2 percent.
SOURCE: Data are from U.S. Department of Energy
(1990).
Page 163
TABLE 19.4 Radiative Forcing Relative to CO2 per Molecule and per Unit Mass Change in
the Atmosphere for Present-Day Concentrations
Change in Radiative Forcing (dF) Relative to Change in Temperature
(dC)
Gasa
per Molecule Relative to CO2
per Unit Mass Relative to CO2
CO2
1
1
CH4
21
58
N2O
206
206
CFC-11
12,400
3,970
CFC-12
15,800
5,750
CFC-113
15,800
3,710
CFC-114
18,300
4,710
CFC-115
14,500
4,130
HCFC-22
10,700
5,440
CCl4
5,720
1,640
CH3CCl3
2,730
900
CF3Br
16,000
4,730
Possible CFC substitutes
HCFC-123
9,940
2,860
HCFC-124
10,800
3,480
HFC-125
13,400
4,920
HFC-134a
9,570
4,130
HCFC-141b
7,710
2,900
HCFC-142b
10,200
4,470
HFC-143a
7,830
4,100
HFC-152a
6,590
4,390
aCO2 CH4 and
N2O forcings are from 1990
concentrations.
SOURCE: Intergovernmental Panel on Climate Change
(1990).
relative importance of different gases will be a function of the
time interval over which one chooses to integrate, with the
short-lived gases appearing more important over short integration
times. Evolution of such an index has occurred rapidly over the
past several years, and a useful index of global warming potential
(GWP) has recently been described in the IPCC Working Group I
document (Intergovernmental Panel on Climate Change, 1990).
The GWP is not yet a mature concept, but it provides a
preliminary basis for a simple comparison of the emissions of
various greenhouse gases and has been adapted for use here. It is,
by definition, "the time integrated
Page 164
FIGURE 19.2 Sources of U.S. CO2 emissions (1987) in megatons CO2.
SOURCE: Adapted
from Marland (1990).
commitment to climate forcing from the instantaneous release of
1 kilogram of a trace gas expressed relative to that from 1 kg of
carbon dioxide." The GWP has, in essence, units of degree years
over degree years and varies considerably with the time interval of
integration because of the different mean lifetimes of the gases.
The indices of global warming potential for the most important
gases are given in Table 19. The CO2-equivalentimpact of different greenhouse
gases on greenhouse warming is computed by taking the emission of
each greenhouse gas and simply multiplying that emission by its
GWP. As shown here, CO2 is the least
effective greenhouse gas per kilogram emitted, but its contribution
to global warming is the largest. CH4 has an "indirect effect" because its
ultimate decomposition products are CO2 and H2O.
The Mitigation Panel has used thesame methodto determine the
"CO2-equivalent" reduction of
different greenhouse gas mitigation strategies. In addition, as
discussed in Part two, the effects Panel has developed a method of
comparing the relative impact on radiative forcing and temperature
rise due to greenhouse warming from reducing the emissions of
different greenhouse gases on a worldwide basis.
By using the U.S. greenhouse gas emission estimates provided
earlier and multiplying these emissions by the GWP of each gas, a
rough estimate of U.S. emissions in CO2-equivalent emissions is shown in Table
19.7. This provides a baseline for mitigation of U.S. greenhouse
gas emissions.
Page 165
TABLE 19.5 Carbon Dioxide Emissions from Fossil Fuel
Burning and Cement Manufacture in the United States (Mt C/yr)
Year
Total
Solid
Liquid
Gas
Cement
Gas Flaring
Per Capita
Percentage of Global Total
1950
696.1
347.1
244.8
87.1
5.3
11.8
4.6
42.5
1951
716.8
334.5
262.2
102.7
5.7
11.7
4.6
40.4
1952
698.0
296.6
273.2
109.9
5.8
12.5
4.4
38.7
1953
714.5
294.3
286.6
115.5
6.1
11.9
4.5
38.7
1954
680.5
252.2
290.2
121.2
6.3
10.6
4.2
36.4
1955
746.0
283.3
313.3
130.8
7.2
11.4
4.5
36.4
1956
781.9
295.0
328.5
138.1
7.6
12.7
4.6
35.8
1957
775.1
282.7
325.8
147.6
7.1
11.9
4.5
34.0
1958
750.8
245.3
333.0
155.8
7.5
9.3
4.3
32.1
1959
781.4
251.5
343.5
169.9
8.1
8.4
4.4
31.6
1960
799.5
253.4
349.8
180.4
7.6
8.3
4.4
30.9
1961
801.9
245.0
354.1
187.4
7.7
7.7
4.4
30.8
1962
831.5
254.2
364.3
198.7
8.0
6.3
4.5
30.7
1963
875.6
272.5
378.8
210.3
8.4
5.6
4.6
30.7
1964
912.9
289.7
389.7
219.8
8.8
5.0
4.8
30.3
1965
948.3
301.1
405.6
228.0
8.9
4.7
4.9
30.1
1966
999.7
312.7
425.9
246.4
9.1
5.5
5.1
30.2
1967
1039.2
321.1
443.6
258.5
8.8
7.2
5.2
30.4
1968
1081.0
314.8
471.9
277.4
9.4
7.6
5.4
30.1
1969
1132.0
319.7
497.4
297.8
9.5
7.7
5.6
29.7
1970
1165.5
322.4
514.8
312.1
9.0
7.2
5.7
28.5
1971
1173.2
305.7
530.5
323.3
9.7
4.2
5.7
27.7
1972
1227.3
310.4
575.5
327.6
10.2
3.6
5.9
27.8
1973
1275.4
334.0
605.4
321.7
10.6
3.6
6.0
27.4
1974
1231.1
330.1
580.7
307.9
10.0
2.4
5.8
26.4
1975
1179.0
317.6
565.1
286.0
8.4
1.9
5.5
25.5
1976
1262.0
351.6
608.1
291.3
9.0
2.0
5.8
25.8
1977
1269.7
355.6
641.9
260.5
9.7
2.0
5.8
25.2
1978
1293.4
361.2
655.0
264.7
10.4
2.2
5.8
25.5
1979
1300.9
378.7
634.6
274.8
10.4
2.4
5.8
24.4
1980
1259.3
394.6
581.0
272.5
9.3
1.8
5.5
23.9
1981
1210.6
403.0
533.1
264.2
8.8
1.4
5.3
23.6
1982
1116.9
390.1
502.2
245.4
7.8
1.4
4.9
22.5
1983
1149.4
405.5
500.1
233.8
8.7
1.4
4.9
22.6
1984
1187.5
427.8
507.1
241.5
9.6
1.6
5.0
22.6
1985
1201.3
448.0
505.6
236.7
9.6
1.4
5.0
22.3
1986
1204.5
439.7
531.1
222.6
9.7
1.4
5.0
21.7
1987
1257.5
465.8
545.3
235.0
9.6
1.8
5.2
22.1
1988
1310.2
493.6
566.4
238.6
9.5
2.1
5.3
22.2
NOTE: Emission estimates are rounded and expressed
in megatons of carbon; per capita estimates are rounded and
expressed in tons of carbon.
SOURCE: Marland (1990).
Page 166
FIGURE 19.3 Sources of U.S. CH4 emissions (1987) in megatons CH4.
SOURCE: Adapted
from Table 24.1 in World Resources Institute(1990).
Structure of Part Three
The following key questions are addressed by the Mitigation
Panel in this part of the report:
• Concerning the comparison of mitigation options: What
technical and policy options are available to mitigate emissions
and greenhouse warming? What are the costs, benefits, and
distributional effects of the various policies?
• Concerning the implementation of mitigation options: What
are the disadvantages and advantages of different policies and the
methods of implementing those policies? How should different policy
methods be implemented?
In answering these questions, the panel was charged not with
deciding whether emissions should be reduced, but rather with
evaluating which options have the greatest potential to mitigate
greenhouse warming if the decision is made to do so. Chapter 20
discusses the panel's approach to evaluating options and the
general advantages and disadvantages of different methods of
implementing policies.
In Chapters 21 through 28, the technical costs and potentials of
some of the mitigation options deemed to be most suitable for
reducing greenhouse gas emissions are estimated by source
sector:
• Residential and commercial energy management (Chapter
21)
• Industrial energy management (Chapter 22)
Page 167
TABLE 19.6 Global Warming Potentials of Several
Greenhouse Gases
Time Horizon
20 Years
100 Years
500 Years
CO2
1
1
1
CH4 (including
indirect)
63
21
9
N2O
270
290
190
CFC-11
4500
3500
1500
CFC-12
7100
7300
4500
HCFC-22
4100
1500
510
NOTE: The global warming potentials (GWPs) show
the relative contributions to radiative forcing (with respect to
CO2) for instantaneous injection to
the atmosphere of 1 kg of gas. Because the gases have different
atmospheric lifetimes, their relative importance changes with the
time interval over which the radiative impact is integrated.
CH4 is thus seen to have a large
impact over short times, but it is less important over longer times
because of its short lifetime. The CH4 calculation recognizes that when CH4 is fully oxidized, CO2 is one of its products.
SOURCE: Intergovernmental Panel on Climate Change
(1990).
• Transportation energy management (Chapter 23)
• Energy supply systems (Chapter 24)
• Nonenergy emission reduction (halocarbons, agriculture,
landfill gas) (Chapter 25)
• Population (Chapter 26)
• Deforestation (Chapter 27)
• Geoengineering (reforestation, sunlight screening, ocean
fertilization, halocarbon destruction) (Chapter 28)
It is important to note that the panel did not formulate or
analyze specific scenarios projecting emission rates into the
future. The panel felt that the accuracy of such projections so far
in the future was questionable (as illustrated by the accuracy of
projections made in the past). Rather, it assumed that the world of
the future would be roughly like the world of today and focused on
potential methods for reducing emissions as if they were being
applied to current (1989) emission sources. It should also be noted
that the panel looked at emission reductions and other measures
from a U.S. perspective—methods by which U.S. emissions could
be reduced and areas in which the United States could transfer
technology, support research and development, or otherwise assist
other countries in reducing their emissions.
Page 168
TABLE 19.7 Estimate of Current U.S. CO2-Equivalent Emissions
Pollutant
Approximate U.S. Greenhouse Emissions (Mt/yr)a
GWP (100 yr)b
Approximate U.S. CO2-Equivalent Emissions (Mt CO2 equivalent/yr)a,c
CO2
4800
1
4800 ± 10%
CH4
50
21
1050 ± 20%
CFC-11
0.08
3500
280 ± 30%
CFC-12
0.14
7300
1020 ± 30%
CFC-113
0.08
4200
340 ± 30%
N2O
1.4
290
410 ± 60%
Approximate total U.S. anthropogenic CO2-equivalent emissions
7900 ± 20%
aMt =
megatons = 1 million metric tons.
bGWP =
global warming potential. This is multiplied by the emission
estimate to determine the CO2-equivalent emissions. The 100-year
lifetime integration is used in these calculations.
cQualitative indications are given for the relative
emissions numbers.
SOURCE: Marland (1990) (CO2); World Resources Institute (1990)
(CH4); personal communication from
F. H. Vogelsberg, Du Pont, to Deborah Stine, Committee on Science,
Engineering and Public Policy, 1990 (CFCs); U.S. Department of
Energy (1990) (all gases).
SOURCE: Marland (1990) (CO2); World Resources Institute (1990)
(CH4); personal communication from
F. H. Vogelsberg, Du Pont, to Deborah Stine, Committee on Science,
Engineering and Public Policy, 1990 (CFCs); U.S. Department of
Energy (1990) (all gases).
The discussion in each of Chapters 21 through 27 is divided into
the following sections:
• Recent Trends. Recent trends in emissions from the
sector are described. For example, in the industrial sector, the
level of energy intensity has decreased in recent years. The
effectiveness of efforts to reduce emissions or improve efficiency
in the sector is also discussed.
• Emission Control Methods. Methods that can be used
to reduce emissions from the sector are discussed. These can
include technical actions both on the demand side (e.g., improving
end-use energy efficiency) and on the supply side (e.g., reducing
emissions from power plants).
In addition, the potential emission reductions and the costs of
implementing such methods are quantified. As discussed in Chapter
20, a ''supply curve" of the implementation cost (dollars per ton
CO2 equivalent) and emission
reduction (megatons of CO2 per year)
is developed for each option if possible. These are "first-order"
analyses, meant only to be a beginning point for determining the
cost-effectiveness of various mitigation options and for
demonstrating a method that could be used to evaluate options.
Page 169
Specifically, second-order effects, including system adjustments
that change costs of greenhouse warming emissions in other sectors,
in other regions of the world, or at later points in time, are not
included. In other words, the analysis presented here should not be
viewed as the definitive assessment of each option. Rather, the
intent is to describe a manner in which options could be evaluated
and to illustrate the approach with the best estimates
available.
• Barriers to Implementation. The technical and
policy barriers to achieving the potential emission reductions
described in the previous section are discussed. For example, in
many cases we can improve the energy efficiency with relatively
short economic payback periods, and yet these energy measures have
still not been fully implemented. What prevents us from achieving
the energy reductions that are possible?
• Policy Options. A number of policy options with
differing levels of effectiveness can be used to encourage the
reduction of greenhouse gas emissions in a particular sector. Each
policy and the positive and negative aspects of implementing it are
discussed. The policies described here are not all-encompassing but
are some that the panel believes are most worthwhile to consider. A
key resource used in this section is the Department of Energy's
(DOE) report entitled A Compendium of Options for Government
Policy to Encourage Private Sector Responses to Potential Climate
Change (U.S. Department of Energy, 1989). The DOE report
includes a more comprehensive look at the range of possible
mitigation policies.
Unfortunately, for many of the options, few data are available
to evaluate the expected effectiveness. Evaluations of the
effectiveness of comparable policies implemented in the past are
sorely needed. In the absence of such studies it is difficult to
determine how much of the potential reductions can actually be
achieved.
• Other Benefits and Costs. Uncounted in the
implementation cost are nongreenhouse-related benefits and costs
that might derive from a particular policy. For example, on the
benefit side, when energy consumption is reduced, the emissions
that cause urban air pollution are also reduced. On the other hand,
reductions in coal consumption could have severe economic
consequences for coal-mining communities.
• Research and Development Needs. Research and
development that is needed to remove or decrease technical and
other barriers to reducing greenhouse gas emissions is described.
For example, hydrogen would be an ideal transportation fuel on some
counts, but technical barriers in terms of storage and
infrastructure limit its application. In some cases, the barrier is
cost. For example, photovoltaics could generate at least a portion
of the energy supply, but high cost currently limits broad usage.
In this case, continued research could improve the technology so
that cost can be reduced. A key reference on research and
development in the energy sector is a recent report by the Energy
Engineering Board of the National Research Council entitled
Confronting Climate Change: Strategies for Energy Research and
Development (National Research Council, 1990).
Page 170
Because the discussion in these chapters is at times highly
technical, a glossary (Appendix S) has been provided for the
reader's convenience. In addition, conversion tables (Appendix T)
are provided for those who may be unfamiliar with the units of
measurement used throughout this report.
The final chapter of this part, Chapter 29, summarizes the
results of individual analyses and draws some general conclusions
regarding the relative merits of potential interventions. This
analysis should not be interpreted as all-inclusive, but it does
provide semiquantitative consideration of a wide sampling of
potential approaches to mitigation. The principal findings and
recommendations concerning the policy choices facing the country
are found in the report of the Synthesis Panel (Part One).
Note
1. Throughout this report, tons (t) are metric; 1 Mt = 1 megaton
= 1 million tons; and 1 Gt = 1 gigaton = 1 billion tons.
References
Intergovernmental Panel on Climate Change. 1990. Climate Change:
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Intergovernmental Panel on Climate Change. 1991. Climate Change:
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Marland, G. 1990. Carbon dioxide emission estimates: United
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Borden, P. Kanciruk, and M. P. Farrell, eds. Report ORNL/CDIAC-36.
Oak Ridge, Tenn.: Carbon Dioxide Information Analysis Center, Oak
Ridge National Laboratory.
National Research Council. 1990. Confronting Climate Change:
Strategies for Energy Research and Development. Washington, D.C.:
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U.S. Department of Energy (DOE). 1989. A Compendium of Options
for Government Policy to Encourage Private Sector Responses to
Potential Climate Change. Report DOE/EH-0103. Washington, D.C.:
U.S. Department of Energy.
U.S. Department of Energy (DOE). 1990. The Economics of
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