Emissions Scenarios - IPCC

Scenario Driving Forces 157
Overproduction in one country may be compensated to some
extent by lower production elsewhere. However, in general,
incentives for higher agricultural output are likely to lead to
more production globally, with a shift from consumption of
plant products to animal products, which are land-, resource-,
and GHG-intensive. In a few industrialized countries a small
trend has developed to support organic farming and regional
marketing of foods. Future policies may thus lead to
agricultural subsidies that are linked more to ecological and
social factors than to the volume of production.
3.7.2.3.3. Dematerialization policies
GHG emissions are likely to be reduced by other policies for
the sustainable use of resources, such as land, forest
ecosystems, mineral resources, water, and soil. Insti'uments
may include direct planning, regulations, establishing property
rights and obligations, information, education, and persuasion,
and a broad range of policies to support or influence the
innovation process to encourage dematerialization (OECD,
1998b).
3.7.2.4. Environmental Policies
While environmental objectives often form part of the rationale
for agriculture and energy policy reforms, many instruments
are focused entirely on environmental objectives. The most
obvious of these are pollution regulations and standards, ecotaxes,
and voluntary and other measures.
In the context of non-mitigation GHG emission scenarios,
probably the most important environmental policies are those
related to sulfur emissions (see Section 3.4.3). Sulfur
emissions are controlled for local and regional environmental
reasons, but sulfur oxides do have a radiative impact, and sulfur
controls can lead to the switching of fuel away from coal and
oil. Thus, almost paradoxically, environmental policies to
combat urban air pollution and acid rain may (via reduced
sulfate aerosol "cooling") exacerbate climate change. Most
sulfur control policies to date have involved either regulations
that limit the concentration of sulfur oxides in flue gas from
large combustion plants, or give standards for the sulfur
content of fuel. Recently, sulfur control poUcies have become
more sophisticated, and aim to limit aggregate emissions on a
national or regional basis to minimize acidic deposition in a
trans-national context. New policy instruments have also been
introduced. The USA has pioneered a "cap and trade" system
with tradable emission permits (for a review see Joskow et al.,
1998).
Other envnonmental poUcies with a greenhouse impact include
controls on ODSs; urban air pollution precursor compounds
(CO, N0^, CH4, and NMVOCs), especially from transport and
domestic solid fuels; and controls on agricultural practice to
reduce water pollution and soil erosion. Policies in all of these
areas are likely to contribute to GHG mitigation. However,
some options, such as an accelerated shift to electric vehicles
to reduce local air pollution, could resuh in higher GHG
emissions in the short term in certain circumstances (Michaelis
etal, 1996).
3.7.2.5. Transportation and Infrastructure PoUcies
Policies on infrastructure may have a very long-term influence
on GHG emissions, although in many cases the causal
relationships are complex and not understood well enough to
justify quantitative analyses of the policy options. These
include urban planning guidance, construction regulations,
policies on ownership and financing of infrastructure, and user
pricing for roads and parking. The most significant impacts on
GHG emissions are likely to derive from policies that influence
demand for travel by car and for freight transport by track
(Newman and Kenworthy, 1990; MichaeUs et al., 1996;
Watson et al, 1996), those that influence energy use in
buildings (Levine et al, 1996; Watson et al, 1996), and those
that influence the conversion of forest for agriculture, or
agricultural land for urban development.
3.7.3. Quantification of Impacts and Implementation of
Policies in SRES
Few of the poficies and instruments identified above can be
represented directiy in the models typically used to produce
GHG emission scenarios. In general, the impacts of policies
are highly uncertain (Houghton et al., 1996). Price-based
instruments have been analyzed in greater detail than other
types of measure, and many empirical studies have been
carried out to determine the response to price changes of
demand for various commodities, especially energy. However,
such research and analysis usually yields very large ranges of
uncertainty in the magnitude of the price response, and often
reveals a strong dependence on specific circumstances. Even
for price-based policies, national and global effects over
20-100 years are very uncertain. For the SRES, it is not
possible to make a precise link between governments'
application of specific policies and the outcome in the various
scenarios.
Instead, the qualitative SRES scenario storylines give a broad
characterization of the areas of policy emphasis thought to be
associated with particular economic, technological, and
environmental outcomes, as reflected in altemative scenario
assumptions in the models used to generate long-term GHG
emission scenarios. In some selected areas, such as sulfur
control policies, a wide body of literature can be drawn upon to
derive specific pollution control levels or maximum emission
trajectories consistent with a particular interpretation of a
scenario storyline. In other areas, such as GHG gases
controlled by the Montreal Protocol, existing scenarios that
reflect the most up-to-date information are used as direct input
to SRES.