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Representative terms from entire chapter:
mitigation options
Page 465
29
Findings and Recommendations
In the previous chapters, the Mitigation Panel has discussed
various options for responding to the emission of greenhouse gases
to the atmosphere. Here the panel has organized that material
within the framework of the charge it received to evaluate the
effectiveness of various policies that could potentially mitigate
greenhouse warming. No attempt has been made to judge
whether action to mitigate greenhouse warming should be taken.
If through the political process, however, the United States
decides to attempt to mitigate greenhouse warming, it should do so
as efficiently as possible, with a broad appreciation of the
alternatives available, their potential effectiveness, and the
implications of their implementation. This means (1) taking a
global perspective with respect to possible actions, (2) assembling
the best information available about the cost per ton of CO2-equivalent reductions, and (3)
evaluating other costs and benefits of prospective actions.
The panel again emphasizes that substantial uncertainties cloud
all the numerical estimates summarized in this chapter. The
degree of uncertainty varies greatly, but in many important
instances such as the large-scale "geoengineering" alternatives, it
is so large that even relative judgments must be made tentatively.
More generally, the assembly of information in this report should
be regarded as useful primarily for comparing large families of
options, and not as specific recommendations of steps to be taken
without additional analysis, research, or empirical study.
U.S. Mitigation Policy
United States policy toward greenhouse gas mitigation is
important for a number of reasons. First, the United States is
currently the largest emitter
Page 466
of greenhouse gases. As such, should greenhouse warming require
active intervention, the United States has a responsibility to do
its part to reduce greenhouse emissions, and unilateral action
could contribute significantly to a reduction in the rate of
emission growth. However, the U.S. role in greenhouse warming,
although large (approximately 20 percent of worldwide CO2-equivalent emissions), is not so large
that unilateral action could stabilize global climate. At least a
60 percent reduction in current worldwide CO2-equivalent emissions would be needed for
stabilization, according to the Intergovernmental Panel on Climate
Change (Intergovernmental Panel on Climate Change, 1991). As
discussed in Chapter 28, geoengineering options may be able to
reduce the amount of reduction required, but international
agreement and participation in such actions would be necessary in
order to undertake such action on a planetary scale.
Second, U.S. policy and technology will affect the inclination
and capability of other nations to respond to greenhouse warming.
The U.S. policy is of instrumental importance, both in meeting our
potential national responsibilities within the world community and
in leading constructive change in that community. The large
magnitude and long time scale of potential adjustments imply that
any response will require a coherent and sustained commitment on a
global scale. What is needed is not a single national policy, but a
long-term strategic perspective on greenhouse warming and its
implications for the world economy.
Third, developing countries are unlikely to be able to respond
to the potential threat of greenhouse warming at the same level as
industrialized countries. The United States should not focus
exclusively on interventions within its own boundaries because
greenhouse warming is a global issue and emission reduction in one
country could be as beneficial as in another. It may be appropriate
for the United States and other industrial economies to seek
low-cost opportunities for reducing greenhouse gas emissions in
developing countries, or to provide economic and technological
support, through the political process, should these countries
decide that such actions are warranted.
Three basic premises are central to the panel's comparison of
different mitigation policy options.
• First, possible responses to greenhouse warming should
be regarded as investments in the future of the nation and the
planet. That is, the actions needed would have to be
implemented over a long time. They should be evaluated as
investments, in comparison with other claims on the nation's
resources, bearing in mind their often widespread implications for
the economy.
• Second, cost-effectiveness is an essential
guideline. The changes in energy, industrial practice, land
use, agriculture, and forestry that might be implemented to limit
greenhouse gas emissions, or the use of geoengineering options,
imply an investment effort lasting several generations and large
enough to affect the macroeconomic profile of the country. Costs of
climate policy therefore need to be considered as a central
element. A sensible guideline is cost-effectiveness: obtaining the
largest reductions in greenhouse gas emissions at the lowest cost
to society. Positive or negative effects of any mitigation option
on societal factors not related to greenhouse warming must also be
taken into account.
Page 467
• Third, a mixed strategy is essential. The
magnitude of the economic changes at stake, together with the need
to pursue a cost-effective approach, implies that a mixed strategy,
employing a variety of measures, would be required. This simple
observation complicates the task of analysis and policy design,
however, because a mixed strategy that is cost-effective can be
designed and implemented only through comparisons of activities in
different sectors of the economy.
Categories of Mitigation Options
A brief description of the mitigation options analyzed by the
Mitigation Panel is shown in Table 29.1. In its comparison of
different options, the panel examined several factors. The first of
these was cost-effectiveness—how much reduction the United
States can get in greenhouse warming for each dollar spent. By
using the index of dollars per ton of CO2 equivalent, the panel was able to
contrast not only the mitigation options that affect CO2 emissions, but also those that address
emissions of halocarbons, N2O, and
CH4.1
As noted in Chapter 20, cost-effectiveness was evaluated using four
different discount rates: 3, 6, 10, and 30 percent. Options that do
not involve emission reductions, but would seek to reduce the level
of greenhouse gases already in the atmosphere or to compensate for
their climatic effects, were also reviewed. These "geoengineering
options" have been converted to CO2
emission reduction equivalence so that they can be compared with
emission reduction options. The comparison is made by using the
objective of climate stabilization rather than emission
reduction per se. In the case of the geoengineering options, the
cost-effectiveness was annualized for comparison purposes but was
not discounted. This is because the panel felt that these options
were so futuristic in nature that discounting would provide these
"back of the envelope" cost estimates a degree of accuracy not
available at the current time.
Assessment of the anticipated magnitude of climatic effects and
appraisal of their impact on society have been the work of the
Effects and Adaptation Panels (Parts Two and Four). That work
builds a basis for informed judgments of the appropriate magnitude
and rate of mitigation.
Barriers to implementing these mitigation options are also a
major concern. Although it may be technically possible to achieve
emission reduction
Page 468
TABLE 29.1 Brief Descriptions of Mitigation Options
Considered in This Study for the United States
RESIDENTIAL AND COMMERCIAL ENERGY MANAGEMENT
(CHAPTER 21)
Electricity efficiency measures
White surfaces/vegetation
Reduce air conditioning use and the urban heat
island effect by 25% through planting vegetation and painting roofs
white at 50% of U.S. residences.
Residential lighting
Reduce lighting energy consumption by 50% in all
U.S. residences through replacement of incandescent lighting (2.5
inside and 1 outside light bulb per residence) with compact
fluorescents.
Residential water heating
Improve efficiency by 40 to 70% through efficient
tanks, increased insulation, low-flow devices, and alternative
water heating systems.
Commercial water heating
Improve efficiency by 40 to 60% through
residential measures mentioned above, heat pumps, and heat recovery
systems.
Commercial lighting
Reduce lighting energy consumption by 30 to 60% by
replacing 100% of commercial light fixtures with compact
fluorescent lighting, reflectors, occupancy sensors, and
daylighting.
Commercial cooking
Use additional insulation, seals, improved heating
elements, reflective pans, and other measures to increase
efficiency 20 to 30%.
Commercial cooling
Use improved heat pumps, chillers, window
treatments, and other measures to reduce commercial cooling energy
use by 30 to 70%.
Commercial refrigeration
Improve efficiency 20 to 40% through improved
compressors, air barriers and food case enclosures, and other
measures.
Residential appliances
Improve efficiency of refrigeration and
dishwashers by 10 to 30% through implementation of new appliance
standards for refrigeration, and use of no-heat drying cycles in
dishwashers.
Residential space heating
Reduce energy consumption by 40 to 60% through
improved and increased insulation, window glazing, and weather
stripping along with increased use of heat pumps and solar
heating.
Commercial and industrial Space heating
Reduce energy consumption by 20 to 30% using
measures similar to that for the residential sector.
Commercial ventilation
Improve efficiency 30 to 50% through improved
distribution systems, energy-efficient motors, and various other
measures.
(continued on page 469)
Page 469
(Table 29.1 continued from page
468)
Oil and gas efficiency
Reduce residential and commercial building fossil
fuel energy use by 50% through improved efficiency measures similar
to the ones listed under electricity efficiency.
Fuel switching
Improve overall efficiency by 60 to 70% through
switching 10% of building electricity use from electric resistance
heat to natural gas heating.
INDUSTRIAL ENERGY MANAGEMENT (CHAPTER
22)
Co-generation
Replace existing industrial energy systems with an
additional 25,000 MW of co-generation plants to produce heat and
power simultaneously.
Electricity efficiency
Improve electricity efficiency up to 30% through
use of more efficient motors, electrical drive systems, lighting,
and industrial process modifications.
Fuel efficiency
Reduce fuel consumption up to 30% by improving
energy management, waste heat recovery, boiler modifications, and
other industrial process enhancements.
Fuel switching
Switch 0.6 quadsa of current coal consumption in
industrial plants to natural gas or oil.
New process technology
Increase recycling and reduce energy consumption
primarily in the primary metals, pulp and paper, chemicals, and
petroleum refining industries through new, less energy intensive
process innovations.
TRANSPORTATION ENERGY MANAGEMENT (CHAPTER
23)
Vehicle efficiency
Light vehicles
Use technology to improve on-road fuel economy to
25 mpg (32.5 mpg in CAFEb
terms) with no changes in the existing fleet.
Improve on-road fuel economy to 36 mpg (46.8 mpg
CAFE) with measures that require changes in the existing fleet such
as downsizing.
Heavy trucks
Use measures similar to that for light vehicles to
improve heavy truck efficiency up to 14 mpg (18.2 mpg CAFE).
Aircraft
Implement improved fanjet and other technologies
to improve fuel efficiency by 20% to 130 to 140 seat-miles per
gallon.
(continued on page 470)
Page 470
(Table 29.1 continued from page
469)
Alternative fuels
Methanol from biomass
Replace all existing gasoline vehicles with those
that use methanol produced from biomass.
Hydrogen from nonfossil fuels
Replace gasoline with hydrogen created from
electricity generated from nonfossil fuel sources.
Electricity from nonfossil fuels
Use electricity from nonfossil fuel sources such
as nuclear and solar energy directly in transportation
vehicles.
Transportation demand management
Reduce solo commuting by eliminating 25% of the
employer-provided parking spaces and placing a tax on the remaining
spaces to reduce solo commuting by an additional 15%.
ELECTRICITY AND FUEL SUPPLY (CHAPTER
24)
Heat rate improvements
Improve heat rates (efficiency) of existing plants
by up to 4% through improved plant operation and maintenance.
Advanced coal
Improve overall thermal efficiency of coal plants
by 10% through use of integrated gasification combined cycle,
pressurized fluidized-bed, and advanced pulverized coal combustion
systems.
Natural gas
Replace all existing fossil-fuel-fired plants with
gas turbine combined cycle systems to both improve thermal
efficiency of current natural gas combustion systems and replace
fossil fuels such as coal and oil that generate more CO2 than natural gas.
Nuclear
Replace all existing fossil-fuel-fired plants with
nuclear power plants such as advanced light-water reactors.
Hydroelectric
Replace fossil-fuel-fired plants with remaining
hydroelectric generation capability of 2 quads.
Geothermal
Replace fossil-fuel-fired plants with remaining
geothermal generation potential of 3.5 quads.
Biomass
Replace fossil-fuel-fired plants with biomass
generation potential of 2.4 quads.
Solar photovoltaics
Replace fossil-fuel-fired plants with solar
photovoltaics generation potential of 2.5 quads.
Solar thermal
Replace fossil-fuel-fired plants with solar
thermal generation potential of 2.6 quads.
(continued on page 471)
Page 471
(Table 29.1 continued from page
470)
Wind
Replace fossil-fuel-fired plants with wind
generation potential of 5.3 quads.
CO2 disposal
Collect and dispose of all CO2 generated by fossil-fuel-fired plants
into the deep ocean or depleted gas and oil fields.
NONENERGY EMISSION REDUCTION (CHAPTER
25)
Halocarbons
Not-in-kind
Modify or replace existing equipment to use
non-CFC materials as cleaning and blowing agents, aerosols, and
refrigerants.
Conservation
Upgrade equipment and retrain personnel to improve
conservation and recycling of CFC materials.
HCFC/HFC-aerosols, etc.
Substitute cleaning and blowing agents and
aerosols with fluorocarbon substitutes.
HFC-chillers
Retrofit or replace existing chillers to use
fluorocarbon substitutes.
HFC-auto air conditioning
Replace existing automobile air conditioners with
equipment that utilizes fluorocarbon substitutes.
HFC-appliance
Replace all domestic refrigerators with those
using fluorocarbon substitutes.
HCFC-other refrigeration
Replace commercial refrigeration equipment such as
that used in supermarkets and transportation with that using
fluorocarbon substitutes.
HCFC/HFC-appliance insulation
Replace domestic refrigerator insulation with
fluorocarbon substitutes.
Agriculture (domestic)
Paddy rice
Eliminate all paddy rice production.
Ruminant animals
Reduce ruminant animal production by 25%.
Nitrogenous fertilizers
Reduce nitrogenous fertilizer use by 5%.
Landfill gas collection
Reduce landfill gas generation by 60 to 65% by
collecting and burning in a flare or energy recovery system.
GEOENGINEERING (CHAPTER 28)
Reforestation
Reforest 28.7 Mha of economically or
environmentally marginal crop and pasture lands and nonfederal
forest lands to sequester 10% of U.S. CO2 emissions.
(continued on page 472)
Page 472
(Table 29.1 continued from page
471)
Sunlight screening
Space mirrors
Place 50,000 100-km2 mirrors in the earth's orbit to
reflect incoming sunlight.
Stratospheric dustc
Use guns or balloons to maintain a dust cloud in
the stratosphere to increase the sunlight reflection.
Stratospheric bubbles
Place billions of aluminized, hydrogen-filled
balloons in the stratosphere to provide a reflective screen.
Low stratospheric dustc
Use aircraft to maintain a cloud of dust in the
low stratosphere to reflect sunlight.
Low stratospheric sootc
Decrease efficiency of burning in engines of
aircraft flying in the low stratosphere to maintain a thin cloud of
soot to intercept sunlight.
Cloud stimulationc
Burn sulfur in ships or power plants to form
sulfate aerosol in order to stimulate additional low marine clouds
to reflect sunlight.
Ocean biomass stimulation
Place iron in the oceans to stimulate generation
of CO2-absorbing phytoplankton.
Atmospheric CFC removal
Use lasers to break up CFCs in the atmosphere.
a1 quad =
1 quadrillion Btu = 1015 Btu.
bCorporate
average fuel economy.
cThese
options cause or alter chemical reactions in the atmosphere and
should not be implemented without careful assessment of their
direct and indirect consequences.
to a given level, the necessary actions might not be taken for
any number of social, economic, or political reasons. For example,
some actions that are economically sensible will not be undertaken
by households and firms because they involve up-front costs and the
households or firms face liquidity constraints that make them
unwilling or unable to undertake the investment. In these cases, it
could be desirable to find some institutional mechanism to overcome
the constraints. In the case of energy efficiency, for example, the
natural focus for such changes is builders, manufacturers, and
utilities (i.e., the providers of electric power and natural gas).
They are, in principle, in a position to make credit available,
directly or indirectly, to purchasers who are constrained in their
decisions by inadequate liquidity. Yet institutions may also face
obstacles to moving to best practice or encouraging their customers
to do so. Thus building codes are typically out of date and may
limit local builders from incorporating the latest proven
energy-saving materials in construction. In most states, public
Page 473
utility pricing formulas reward public utilities for building
new power plants, but not for investments that conserve energy.
Examples exist in many areas. It should be remembered, however,
that some of these ''constraints" serve other social objectives.
For example, there are many reasons people drive their cars to work
instead of taking mass transit, and many reasons they select large,
less-efficient vehicles. The reasons may lie in time saved, safety,
or personal flexibility, but in each case energy conservation is
not the only social objective that enters into the decision
process. Altering long-standing practices is rarely easy—even
if such changes may bring economic as well as potential climatic
benefits.
Many of the potential climate interventions, of course, have
effects other than merely reducing atmospheric CO2 or its equivalent. Some of these effects
will be positive, others negative, and some will have different
effects on different parts of society. It is also important to
remember that these inquiries occur on a planet where the
population is still increasing and most of the inhabitants aspire
to a higher standard of living. Therefore another important factor
in analyzing various mitigation policies involves the costs and
benefits (beyond implementation) that are likely to occur should
the mitigation action be taken. Thus some low-cost options will be
unattractive on other grounds, while some high-cost actions will
provide additional benefits.
In the present study the Mitigation Panel has barely touched on
issues such as the barriers to implementation and the social,
environmental, and economic implications of the strategies
investigated. The panel hopes that the mention of these issues in
this analysis through the use of the categories described below
will contribute to their visibility and raise them to a higher
level of consideration in more detailed studies later. The panel
has tried to be qualitatively sensitive to these issues and to
discourage direct dollar comparisons of options with widely
different external implications. These three
factors—cost-effectiveness, implementation obstacles, and
other costs and benefits—suggested the categories for
analysis.
The three categories of options are as follows:
• Category 1 options: "Best-practice" mitigation
options available at little or no net cost that are not fully
implemented due to various implementation obstacles.
• Category 2 options: Mitigation options that are
either relatively costly or face implementation obstacles not fully
represented in the implementation cost. They may also have other
benefits and costs not fully represented.
• Category 3 options: Mitigation options that appear
to be feasible with the current, limited state of knowledge. They
may, with additional investigation, research, and development,
provide the ability to change atmospheric concentrations of
greenhouse gases, or radiative forcing, and the ultimate impact of
greenhouse warming on a substantial scale.
Page 474
In none of the categories have full institutional costs been
estimated. This is important because most Category 1 options,
particularly the ones estimated to produce net savings, require
institutional changes before they become available to buyers and
sellers of goods and services that release greenhouse gases. The
costs of changing these institutional barriers are unknown. Without
an appraisal of institutional costs, any comparison is incomplete;
such an appraisal has not been done in this report. The panel
believes it has provided a framework within which these appraisals
can be made in future studies. A major rationale for discussing
options under three categories is that the panel not believe the
full range of options should be compared on a simple monetary
scale.
In Tables 29.2 to 29.7 the panel summarizes the mitigation
strategies that have been reviewed using the three categories.
Although the menu of options reviewed is not intended to provide an
inventory of all possibilities, it seeks to identify the most
promising options. The panel hopes that it provides the beginnings
of a structure and a process for identifying those strategies that
could appropriately respond to the prospect of greenhouse
warming.
Category 1 Options
Every progressive society finds its economic activities on
average falling short of best practice in most areas. This is
because new practices are being contrived continually and it takes
time for them to diffuse throughout the economy. Thus every
progressive society enjoys opportunities for improving its overall
situation by reducing the gap between average practice and best
practice. Obstacles to more rapid diffusion of better practice
include lack of information, lack of opportunity (e.g., if stores
do not stock the improved products), political resistance, capital
investment, risk aversion, and simple human inertia. Cost of
replacement is also an obstacle, but one that disappears as old
equipment wears out and renewal becomes necessary. Within
organizations, better practices may not be introduced because of
divisions in responsibility, for example, if those making the
decisions to go ahead do not get credit for the benefits that flow
from the new practice (e.g., "maintenance" pays for the light
bulbs, but "operations" pays the electric bills).
Thus there are typically many improvements that "ought" to be
undertaken, and most of them will be undertaken, eventually,
because they are in the interests of those undertaking them. These
decisions can be hastened by providing information and opportunity.
Heightened awareness will encourage stores to stock improved
products, top management to review the division of responsibilities
within their firms, and so on.
The general proposition that economic activities fall short of
best practice
Page 475
applies to every area of the economy. Many opportunities for
reducing greenhouse gas emissions will also improve economic
well-being, because they are more efficient than prevailing
practices, judged in conventional terms. These "no-regrets" actions
show up in Table 29.2 as measures with a net savings or very low
cost. This negative cost does not imply that no expenditure is
required to implement these actions, but rather that the real rate
of return to the initial investment in making the change exceeds
the common societal discount rates. However, as discussed in
Chapters 21 and 22, households and firms do not have perfect
information, and they are often observed to behave as if a 30
percent rate of return were needed to invest in one of these
options. Therefore a column with a 30 percent discount rate has
been added to illustrate what some households or firms seek in the
marketplace prior to investment. As shown here, even at a 30
percent discount rate (well above their rate of return for other
investment opportunities), firms and households will still receive
a benefit for investment in many of these options. In other words,
these "movement to best practice" actions involve attractive rates
of return and would be undertaken voluntarily in many cases.
However, as discussed in Chapters 21, 22, and 23, the timing can be
accelerated if information, technical assistance, and financing can
be provided.
Category 2 Options
As shown in Table 29.3, there are actions to reduce greenhouse
gas emissions, or compensate for their climatic effects, that are
either economically costly in the sense that the nation or the
world must reduce its future income to reduce the potential for
climate change, must face implementation obstacles, or will
encounter additional benefits and costs not fully reflected in the
implementation cost. The panel has tried to make rough estimates of
the costs of reducing carbon in the atmosphere through various
actions. The range of costs is wide, varying from well under $1/t
CO2 equivalent reduction to over
$500/t.
As discussed in Chapter 25, reduction in CFC consumption can
also help reduce stratospheric ozone depletion. In another case of
issues beyond current cost, the information in Chapter 24 indicates
that solar energy is relatively costly now, but anticipated
technological developments may lower the price
substantially—perhaps making it a cost-effective option.
Nuclear power faces not only cost obstacles, but also
implementation obstacles because of public concerns about nuclear
plant safety and management of radioactive waste. The replacement
of coal power plants with natural gas also faces implementation
obstacles as utilities concerned about an uncertain natural gas
supply resist investment in plants with a 30-year lifetime. Chapter
24 discusses each of the energy options in more depth.
Page 488
Page 489
FIGURE 29.1 Low-mid-high mitigation cost comparison, assuming
100 percent implementation.
Net Implementation Costa
MaximumPotential Emission Reductionb
Percent Reduction
($/t CO2
equivalent)
in U.S. Emissionsc
Low
Mid
High
(Gt CO2
eq./yr.)
CO2(%)
CO2 eq. (%)
1
Residential & Commercial Energy Efficncyd
-78
-62
-47
0.9
18
11
2
Vehicle Efficiency (no fleet change)d
-75
-40
-2
0.3
6
4
3
Industrial Electric Efficiencyd
-51
-25
1
0.5
11
7
4
Transportation System Managemente
-50
-22
5
0.05
1
1
5
Power Plant Heat Rate Improvementsd
-2
0
2
0.05
1
1
6
Landfill Gas Collectiond
0.4
1
1
0.2
5
3
7
Halocarbonse
0.9
1
3
1.4
29
18
8
Agriculturee
1
3
5
0.2
5
3
9
Reforestatione
3
7
10
0.2
5
3
10
Electricity Supplye
5
45
80
1.0
21
13
aMitigation options are placed in order of
cost-effectiveness based on the average (arithmetic mean) of the
costs for each option within that category at a social discount
rate of 6 percent. If the cost provided (as shown in Tables 29.2 to
29.4) is a range, the cost range is averaged to determine the
options cost. Only a select number of emission reduction methods
are included. Those greater than $100/t CO2 eq. or whose cost is unknown are not
included.
bCumulative sector emission reductions are computed by
adding the emission reduction from each mitigation option in that
sector in gigatons per year. If the emission reduction is a range,
the arithmetic mean is used to compute the cumulative emission
reduction. To remove double-counting, the energy supply emission
reduction potential was reduced by the amount of reduction
potentially available for the less expensive efficiency options.
For non-CO2 emission reductions, the
equivalent impact of a CO2 reduction
is computed by multiplying the non-CO2 reduction by the 100-yr GWP factors (see
Chapter 19).
cPercent
reduction is in terms of 1988 U.S. CO2 emissions, which are assumed to be
approximately 4.8 Gt CO2 per year.
Total U.S. greenhouse gas emissions are, of course, larger than
this and include emissions of halocarbons, methane, and nitrous
oxide. They are assumed to be approximately 7.9 Gt CO2 eq./yr
dCategory
1 options.
eCategory
2 options.
Page 490
from a source but acts as a sink. Thus this figure should be
interpreted with extreme caution; however, the Mitigation Panel
believes it provides a useful picture of the way in which many
different mitigation options may be compared with one another.
Implementing Response Programs
Figures 29.2 to 29.5 place Figure 29.1 in the context of other
cost estimates and the limitations associated with actually
implementing a mitigation response program. To do this, the panel
examined the sensitivity to the extent to which these programs are
implemented by society. Figure 29.2 displays the Figure 29.1 supply
curve for threed different levels of implementation of the emission
reduction strategies: 25, 50, and 100 percent. As illustrated here,
the effectiveness of CO2-equivalent
emission reduction changes greatly as a function of the potential
achieved. Figure 29.3 shows the range of technological costing cost
estimates. The lower curve is the most optimistic estimate—100
percent implementation of the option as described in Table 29.1,
with the lower-cost bound. The upper curve is a more pessimistic
estimate—25 percent implementation of the option as described,
with the upper-cost bound. Mitigation costs will not be known
perfectly; an approach of the kind illustrated in Figure 29.3,
which develops bounding cases, can be useful in developing
mitigation plans.
Figure 29.4 is a compilation of a number of energy modeling
estimates of the cost of CO2-equivalent reduction. Details on the
compilation of this curve are provided in Appendix R. The energy
modeling estimates differ in two important characteristics from the
technological costing analyses in this report. First, energy
modeling estimates are comprehensive energy sector models. That is,
they include a consistent accounting of the demand, supply, and
resources used in the countries or regions studied. In this
respect, they differ from the approach in this report, which looks
at the possibilities for greenhouse gas reductions from individual
technologies and attempts to make the estimates mutually consistent
by manual calculations. One difficulty with the technological
costing approach is that calculations are on a constant cost basis;
that is, they do not account for how implementation of these
measures may affect the cost of the measure. A major surge in the
number of natural gas plants, for example, will likely increase
demand for and therefore the price of natural gas. This would
increase the cost of the mitigation option—perhaps changing
its ranking. The same is true for energy efficiency measures: as
demand is reduced, the price of electricity would change. This
would change the savings available from that energy efficiency
measure. The energy modeling approach takes these supply and demand
impacts into account, while
Page 491
FIGURE 29.2 Mitigation comparison with different
levels of implementation.
FIGURE 29.3 Range of technological costing
mitigation cost estimates.
Page 492
FIGURE 29.4 Range of energy modeling mitigation
cost estimates (see Appendix R for more information).
FIGURE 29.5 Comparison of technological costing
and energy modeling methods of mitigation costs.
Page 493
the technological costing approach is based on the margin of the
current economy and therefore does not.
A second important difference between the energy modeling
approach and the approach taken by the Mitigation Panel is that the
models surveyed estimate the cost function for reducing greenhouse
gas emissions beginning from the point at which all "negative-cost"
options have been employed. In most economic models, the market
equilibrium is this point; in one model, where market failures are
allowed, the results have been recast so that cost estimates begin
from the point at which the market failures have been allowed for.
It is important to note then, that the negative-cost part of the
cost function, should that exist, is excluded from energy modeling
analyses. A full description of the development of this curve is
provided in Appendix R.
Finally, Figure 29.5 combines the technological costing
mitigation curves in Figure 29.3 and the energy modeling curves in
Figure 29.4. The energy modeling curves fall roughly between the
bounding estimates of the technological costing approach. The
primary difference, as mentioned earlier, is that the energy
modeling curves do not include the financial benefits from
efficiency measures. At the current limited state of knowledge the
panel believes that the actual implementation costs of mitigating
greenhouse gas emissions (excluding costs beyond those needed
directly for implementation) are likely to fall within the range
provided by the technological costing method. It is important to
note that while the panel believes that the technological costing
approach is better suited to evaluating the comparative advantages
and disadvantages of specific mitigation options because current
economic models do not have the specificity needed for such an
analysis, there are reasons to be skeptical of the degree to which
such option-driven assessments can incorporate social responses
(including market responses) to alternative courses of action.
A review of Figures 29.2 to 29.5 indicates that it would not be
unreasonable to expect that a roughly 25 percent reduction in U.S.
greenhouse gas emissions (i.e., 2 Gt CO2 equivalent) might be achieved at a cost
of less than $10/t CO2 equivalent.
This is, in more commonly used terms, roughly an additional $22 per
short ton of coal, $4.75 per barrel of oil, $0.60 per million cubic
feet of natural gas, $0.11 per gallon of gasoline, or 0.7 cents/kWh
for the current U.S. electricity mix.
A wide array of policy instruments is available for implementing
mitigation options. Two categories are direct regulation and
incentives. Direct regulation instruments mandate action and
include controls on consumption (bans, quotas, required product
attributes), production (quotas on products or substances), factors
in design or production (efficiency, durability, processes), and
provision of services (mass transit, land use). Incentive
instruments are designed to influence decisions by individuals and
organizations,
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and include taxes and subsidies on production factors (carbon
tax, fuel tax), taxes on products and other outputs (emission
taxes, product taxes), financial inducements (tax credits,
subsidies), and transferrable emission rights (tradeable emission
reductions, tradeable credits). The choice of policy instrument
depends on the objective to be served.
Interventions at all levels of human aggregation could
effectively reduce greenhouse warming. For example, individuals
could reduce energy consumption, recycle goods, and reduce
consumption of deleterious materials. Local governments could
control emissions from buildings, transport fleets, waste
processing plants, and landfill dumps. State governments could
restructure electric and gas utility pricing structures and
stimulate a variety of efficiency incentives. National governments
could pursue action in most of the policy areas of relevance.
International organizations could coordinate programs in various
parts of the world, manage transfers of resources and technologies,
and facilitate exchange of monitoring and other relevant data.
Although the analysis of mitigation options in this report does
not include all possibilities, the Mitigation Panel is hopeful that
it does identify the most promising options considered here. The
panel feels confident that it provides the beginnings of a
structure and a process for identifying those strategies that could
appropriately mitigate the prospect of greenhouse warming.
International Considerations
Whatever policies the United States follows in order to truly
address greenhouse warming, it will eventually be necessary to
achieve broader international consensus in action. Many of the
cost-effective options appropriate for the United States are also
applicable in other countries, including developing nations. A
range of other measures are also relevant, such as removing or
reducing market-distorting subsidies that encourage greenhouse gas
emissions. Effective participation of developing countries in the
reduction of emissions will require political actions by those
nations, as well as international negotiations that deal with the
availability of financial and technical resources and with
competing requirements for current economic growth.
As discussed in Chapter 26, population growth, largely taking
place in developing countries, is a basic contributor to the
increase in greenhouse gas emissions. This will become even more
relevant in the future, as those countries improve their economies
with accompanying increased energy consumption. Limiting growth in
population is central to limiting future energy consumption and,
therefore, to future stabilization of greenhouse gas emissions.
Limiting population growth may not be financially costly, but it is
beset with political, social, and ideological obstacles. Similarly,
as discussed in Chapter 27, reducing or reversing net deforestation
as a means of
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reducing greenhouse gases raises a host of nontechnical issues
that are not evident from a financial standpoint.
The international negotiations on greenhouse issues that will be
required to lead to common action on these and related matters, and
to avoid "free riders" (where one nation benefits from the costly
actions of others), will be difficult and will necessarily involve
matters of great political and economic concern. International
studies and analyses are currently under way in an impressive
number of settings, with the recent experience of the Montreal
Protocol and Law-of-the-Sea negotiations as guides to approaches
that are useful and those that should be avoided. Hard choices
remain in the future, however, because negotiations will be more
difficult than any of the predecessors in the environmental area.
However, the necessarily deliberative nature of those negotiations
should not obscure the conclusion that unilateral actions by the
United States, or common actions by currently large greenhouse gas
emitters among industrialized countries, can be useful on their
own. They can reduce emissions below their expected levels in the
short term, delay the onset of warming (if warming materializes),
and create a precedent that could help lead to coordinated
international action.
Final Thoughts
The Mitigation Panel has attempted to outline a perspective that
should be pursued relative to mitigation policy. First, the United
States needs to realize that although unilateral actions can
contribute significantly to the reduction of greenhouse gases, the
greenhouse warming phenomenon is global, and national efforts alone
would not be sufficient to eliminate the problem. This means that
the nation should take a global perspective with respect to
possible actions. Second, cost-effectiveness should be a primary
guide in making greenhouse warming mitigation policy as efficient
as possible.
Therefore the Mitigation Panel has tried to bring together
informed judgments of the cost of greenhouse gas reduction, as well
as other costs and benefits of prospective actions. It should be
emphasized that the analysis the panel conducted was
"cross-sectional" as opposed to a longitudinal analysis of options
over time. There was no attempt, for example, to project future
levels of economic activity and their implications for greenhouse
gas emissions. This study does account, however, for future
consequences of current actions. In particular, the direct effects
of each option on greenhouse gas emissions are assessed. The panel
has not attempted to examine those options under the different
overall emission rates that might occur at future times. Its
analysis must therefore be seen as an initial assessment of
mitigation options in terms of their return on investment under
current conditions. A subsequent analysis might consider
appropriate strategies under changing
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conditions. Furthermore, the time required to implement these
mitigation options is not considered. Some options, such as those
in energy efficiency, can be implemented immediately if the
noneconomic obstacles are overcome. Others, such as changes in
electricity production, might take considerably longer, on the
order of decades. The rates at which these mitigation options are
implemented depends on the decision makers in a wide range of
firms, households, and governmental units throughout the United
States.
Once the cost-effectiveness and mitigation potential of each
option were determined, the Mitigation Panel categorized these
options. The best-practice (Category 1) options have significant
potential for mitigating greenhouse warming at negative or low net
implementation cost; however, information and incentive mechanisms
are needed to hasten these reductions. Although no firm
quantitative estimates of the net contribution of these policies
can be given, it is not unreasonable to believe that U.S.
greenhouse gas equivalent emissions could be reduced 25 percent
from 1990 levels through use of these relatively low cost options
alone. The second category of options (Category 2) entails
additional costs and benefits not included in the
cost-effectiveness estimate. The United States and other countries
are already working to reduce CFC emissions—providing a major
contribution to the reduction of greenhouse gas emissions at a
relatively low cost (in addition to the benefits to the
stratospheric ozone layer). Perhaps one of the surprises of this
analysis is the relatively low cost at which some of geoengineering
options (Category 3) might be implemented. However, it will require
further inquiry to decide if geoengineering options can produce the
targeted responses without unacceptable additional efforts. The
level at which science is currently able to evaluate the
cost-effectiveness of engineering the global mean radiation balance
leaves great uncertainty in both the areas of technical feasibility
and environmental consequences. This analysis does suggest that
further inquiry is appropriate.
Finally, greenhouse warming is an international problem that the
United States cannot solve alone. Slowing worldwide population
growth may be necessary to achieve a significant change in
worldwide emissions of greenhouse gases. However, the panel's
analysis indicates that reducing population growth alone may not
reduce emissions of greenhouse gases if there is continued economic
growth. Reduction of deforestation may provide another significant
contribution to mitigating greenhouse gas emissions. Due to
domestic concerns, however, candidate countries may find these
options difficult to implement. The United States can make
contributions to international efforts, and such action might
significantly slow greenhouse warming at a cost that is less
expensive than the cost of options implemented in the United
States.
The uncertainties in all of the mitigation alternatives
underscore the central role of learning. This is not the
usual academic call for more research. It is instead a
recommendation that policy actions be treated as opportunities
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to learn and that they be designed and executed so that learning
is enhanced. This implies the need for more and better policy
analysis. The world being altered by greenhouse warming is one
whose geophysical and social character is imperfectly understood.
Errors are inevitable. Large errors will be costly and painful.
Accordingly, the United States must seek to use small errors as a
source of learning, so as to lessen the possibility of serious
mistakes.
For example, the time dimension is an important part of
formulating a greenhouse warming mitigation strategy. It can have
important consequences for determining the optimal timing and
quantity of any intervention. This is true if that decision is
based on what society gets in the form of lesser global climate
change vis-à-vis what it gives up in terms of current
satisfaction and the enhanced ability to accommodate future
adaptation. In this, fully accounting for all the positive aspects
of mitigation—reduced speed of change, reduced total exposure
to damage, and final level of global climate change—is
important. Each has separate effects on the consequences of
societal interest such as rise in sea level, agricultural
productivity, and changes in ecological systems. They can also
differ in their effects on the distribution of consequences over
time and geography. Different instruments may lead to outcomes that
diverge from those expected when only tons reduced and costs are
considered. Application of the relationships discussed here
requires an understanding of the physical relationships among
flows, stock, and global climate change that lies beyond current
knowledge. It also requires complex judgments about the trade-offs
among sometimes competing policy goals.
Political processes will, in the end, determine whether and when
these particular mitigation options should be undertaken. The
results of this analysis indicate that the United States could make
an important contribution to slowing greenhouse warming through
adoption of some of these mitigation options. Some options might
even provide a net savings to the U.S. economy. Using this analysis
and information from the other two panels, the Synthesis Panel
judges the extent to which these options should be pursued.
Note
1. Throughout this report, tons (t) are metric; 1 Mt = 1 megaton
= 1 million tons; and 1 Gt = 1 gigaton = 1 billion tons.
Reference
Intergovernmental Panel on Climate Change. 1991. Climate Change:
The IPCC Response Strategies. Covelo, Calif.: Island Press.
