The primary economic benefits of mitigation are the
avoided costs associated with the adverse impacts of climate change.
Greenhouse gas emission reduction (mitigation) action
would lessen the pressures on natural and human systems from climate change.
Comprehensive, quantitative estimates of global primary benefits of mitigating
climate change do not exist. For mean temperature increases over a few
ºC relative to the year 1990, impacts are predominantly adverse,
so net primary benefits of mitigation are positive. A key
uncertainty is the net balance of adverse and beneficial
impacts of climate change for temperature increases less than about a
few ºC. These averages conceal wide regional variations.
||Mitigation generates costs and ancillary
||Major reductions in global greenhouse
gas emissions would be necessary to achieve stabilization of their concentrations.
For example, for the most important anthropogenic greenhouse gas, carbon
cycle models indicate that stabilization of atmospheric CO2 concentrations
at 450, 650, or 1,000 ppm would require global anthropogenic CO2
emissions to drop below year 1990 levels within a few decades, about a century,
or about 2 centuries, respectively, and continue to decrease steadily thereafter.
Emissions would peak in about 1 to 2 decades (450 ppm) and roughly a century
(1,000 ppm) from the present. Eventually stabilization would require CO2
emissions to decline to a very small fraction of current global emissions.
The key uncertainties here relate to the possibilities of
climate change feedbacks and development pathways and how these affect the
timing of emissions reductions.
|| Mitigation costs and benefits vary widely
across sectors, countries, and development paths. In general, it
is easier to identify sectors -- such as coal, possibly oil and gas, and
some energy-intensive industries dependent on energy produced from these
fossil fuels -- that are very likely to suffer an economic disadvantage
from mitigation. Their economic losses are more immediate, more concentrated,
and more certain. The sectors that are likely to benefit include renewable
energy, services, and new industries whose development is stimulated by
demand for low-emission fuels and production techniques. Different countries
and development paths have widely different energy structures, so they too
have different costs and benefits from mitigation. Carbon taxes can have
negative income effects on low-income groups unless the tax revenues are
used directly or indirectly to compensate such effects.
||Emission constraints in Annex I countries
have well established, albeit varied, "spill-over" effects on
non-Annex I countries. Analyses of the effects of emissions constraints
on Annex I countries report reductions below what would otherwise occur
in both projected GDP and in projected oil revenues for oil-exporting non-Annex
||Lower emissions scenarios require different
patterns of energy resource development and an increase in energy R&D
to assist accelerating the development and deployment of advanced environmentally
sound energy technologies. Emissions of CO2 due to fossil-fuel
burning are virtually certain to be to the dominant influence on the trend
on the atmospheric CO2 concentration during the 21st century.
Resource data assessed in the TAR may imply a change in the energy mix and
the introduction of new sources of energy during the 21st century. Fossil-fuel
resources will not limit carbon emissions during the 21st century. The carbon
in proven conventional oil and gas reserves is much less, however, than
the cumulative carbon emissions associated with stabilization of CO2
at levels of 450 ppm or higher.25
These resource data may imply a change in the energy mix and the introduction
of new sources of energy during the 21st century. The choice of energy mix
and associated technologies and investments -- either more in the direction
of exploitation of unconventional oil and gas resources, or in the direction
of non-fossil energy sources, or fossil energy technology with carbon capture
and storage -- will determine whether, and if so, at what level and cost,
greenhouse concentrations can be stabilized. Key uncertainties
are the future relative prices of energy and carbon-based fuels, and the
relative technical and economic attractiveness of non-fossil-fuel energy
alternatives compared with unconventional oil and gas resources.
Studies examined in the TAR suggest
substantial technological and other opportunities for lowering mitigation
costs. National mitigation responses to climate change can be more effective
if deployed as a portfolio of policy instruments to limit or reduce net
greenhouse gas emissions. Significant progress in energy-saving
and low-carbon technologies has been made since 1995, and the progress
has been faster than anticipated in the SAR. Net emission reductions could
be achieved through, inter alia, improved techniques in production and
use of energy, shifts to low- or no-carbon technologies, CO2
removal and storage, improved land-use and forestry practices, and movement
to more sustainable lifestyles. Significant progress is taking place in
the development of wind turbines, solar energy, hybrid engine cars, fuel
cells, and underground CO2 storage. Key uncertainties
are (a) the likelihood of technological breakthroughs leading
to substantial reductions in costs and rapid take-up of low-carbon processes
and products, and (b) the future scale of private and public R&D expenditures
on these technologies.
Q7.20, & Q7.23,
& Q7 Box 7-1