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This question focuses on the potential for, and costs of, mitigation
both in the near and long term. The issue of the primary mitigation benefits
(the avoided costs and damages of slowing climate change) is addressed
in Questions 5 and 6, and
that of ancillary mitigation benefits is addressed in this response and
the one to Question 8. This response describes a
variety of factors that contribute to significant differences and uncertainties
in the quantitative estimates of the costs of mitigation options. The
SAR described two categories of approaches to estimating costs: bottom-up
approaches, which often assess near-term cost and potential, and are built
up from assessments of specific technologies and sectors; and top-down
approaches, which proceed from macro-economic relationships. These two
approaches lead to differences in the estimates of costs, which have been
narrowed since the SAR. The response below reports on cost estimates from
both approaches for the near term, and from the top-down approach for
the long term. Mitigation options and their potential to reduce greenhouse
gas emissions and sequester carbon are discussed first. This is followed
by a discussion of the costs for achieving emissions reductions to meet
near-term emissions constraints, and long-term stabilization goals, and
the timing of reductions to achieve such goals. This response concludes
with a discussion of equity as it relates to climate change mitigation. |
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Potential, Barriers, Opportunities, Policies, and
Costs of Reducing Greenhouse Gas Emissions in the Near Term |
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Significant technological and biological potential
exists for near-term mitigation. |
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7.3 |
Significant technical progress relevant to greenhouse
gas emissions reduction has been made since the SAR, and has been faster
than anticipated. Advances are taking place in a wide range of
technologies at different stages of evelopment -- for example, the market
introduction of wind turbines; the rapid elimination of industrial by-product
gases, such as N2O from adipic acid production and perfluorocarbons
from aluminum production; efficient hybrid engine cars; the advancement
of fuel cell technology; and the demonstration of underground CO2 storage.
Technological options for emissions reduction include improved efficiency
of end-use devices and energy conversion technologies, shift to zero-
and low-carbon energy technologies, improved energy management, reduction
of industrial by-product and process gas emissions, and carbon removal
and storage. Table 7-1 summarizes the results from many sectoral studies,
largely at the project, national, and regional level with some at the
global level, providing estimates of potential greenhouse gas emissions
reductions to the 2010 and 2020 time frame. |
WGIII TAR Sections 3.3-8, & WGIII TAR Chapter 3 Appendix | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
7.4 |
Forests, agricultural lands, and other
terrestrial ecosystems offer significant carbon mitigation potential.
Conservation and sequestration of carbon, although not necessarily permanent,
may allow time for other options to be further developed and implemented
(see Table 7-2). Biological
mitigation can occur by three strategies: a) conservation of existing
carbon pools, b) sequestration by increasing the size of carbon pools,13
and c) substitution of sustainably produced biological products (e.g.,
wood for energy-intensive construction products and biomass for fossil
fuels). Conservation of threatened carbon pools may help to avoid emissions,
if leakage can be prevented, and can only become sustainable if the socio-economic
drivers for deforestation and other losses of carbon pools can be addressed.
Sequestration reflects the biological dynamics of growth, often starting
slowly, passing through a maximum, and then declining over decades to
centuries. The potential of biological mitigation options is on the order
of 100 Gt C (cumulative) by the year 2050, equivalent to about 10 to 20%
of projected fossil-fuel emissions during that period, although there
are substantial uncertainties associated with this estimate. Realization
of this potential depends upon land and water availability as well as
the rates of adoption of land management practices. The largest biological
potential for atmospheric carbon mitigation is in subtropical and tropical
regions. |
WGIII TAR Sections 3.6.4 & 4.2-4, & SRLULUCF | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Other reports in this collection |