Emissions Scenarios - IPCC

280 Emission Scénarios
in tlie Al or Bl familles, but faster than in the A2 family. Sulfur
emission projections for the В 2 marker scenario were
generated on the basis of minimization of critical loads of
acidic deposition using the methodology described in Amann
et al. (1996). No explicit link between income levels and sulfur
control regime was made in this scenario. The resultant sulfur
emissions are 61 IVltS in 2020, 56 MtS in 2050, and 48 MtS in
2100 (see Figure 5-12).
All the SRES marker scenarios anticipate increasing levels of
sulfur control, with rates and timing ranging from rapid
introduction of stringent controls in Bl-IMAGE to more
gradual, later, and less stringent controls in A2-ASF. To
illustrate the impacts of sulfur controls in the scenarios, an
"uncontrolled sulfur" variant of the B2 marker scenario was
calculated at the Intemational Association for Applied Systems
Analysis (IIASA; for details see Box 5-4). In this hypothetical
scenario, sulfur emissions amount to 182 MtS in 2050 and 227
MtS in 2100 (compared to 57 and 47 MtS, respectively, in the
B2 marker scenario). These emission levels are much higher
even than those in the A2 marker scenario (105 MtS in 2050
and 60 MtS in 2100).
5.6. Regional Distribution and Gridding
Regional information on emissions serves at least two major
purposes - to identify the contribution of world regionsto the
global total and to track shifts in the relative weight of different
regions. This information is especially relevant for the
development of mitigation scenarios. For climate modeling, the
regional distribution of emissions for well-mixed GHGs (COj,
CH^, N^O, and halocarbons) may not be that important.
However, short-lived gases such as SO2 are radiatively
important close to the point of origin only; their local and
regional concentrations may significantly change the future
climate outlook. The same is true for the group of ozone
precursors (CO, N0^, and NMVOCs). To be able to estimate
tropospheric ozone concentration levels, regionalized
information is indispensable.
The initial evaluation showed that the 40 SRES scenarios have
a very substantial regional variability in emissions of all
radiatively important substances. The detailed and rigorous
analysis of this variability falls outside the scope of the cuiTent
report. Therefore, this section merely illustrates possible
regional pattems based on standardized regional emissions in
the four SRES marker scenarios (see also Kjam et al., 2000).
Standardized regional outputs from the 40 SRES scenarios are
provided in Appendix VII.
Subsection 5.6.1 describes emissions of GHGs and SO2 in the
four SRES macro-regions, followed by the description of
"gridded" SOj emissions (distributed over a ГхГ grid) in 5.6.2.
In this report represented by four macro-regions - OECD90,
REF, ASIA, and
ALM.
5.6.1. Regional Distribution
As Tables 5-13a to 5-13d clearly illustrate, the distribution of
emissions over the four regions in the base year (1990) is very
uneven. For example, while in industrialized regions (OECD90
and REF) fossil and industrial COj emissions are dominant, in
the developing regions (ASIA and ALM) the contribution of
land-use emissions (deforestation) is also very important. In
1990, developing regions produced much lower volumes of
CO, and high-GWP gases than the industrialized world, while
their relative share of NjO, CH4, and NO^, emissions was much
more substantial (see Figures 5-13a to 5-13d).
5.6.1.1. Carbon Dioxide Emissions from Fossil Fuels and
Industry
As suggested by Figure 5-14, in all the SRES scenario famihes
the share of industriaUzed regions (OECD90 and REF) in global
total becomes progressively smaller and by 2100 these regions
emit from 23% to 32% of the total (Table 5-14, Figure 5-14).
In the OECD90 region, standardized fossil fuel and industrial
CO2 emissions in the AlB marker scenario (AlB-AIM)
increase from 2.8 GtC in 1990 to 3.4 GtC in 2050, and
subsequently decline to 2.2 GtC in 2100 (Figure 5-14).
Compared to other scenarios, the growth in primary energy use
in this region is relatively high, spuixed by rapid economic
development (see also Chapter 4). However, after 2050 the
increases in the use of primary energy are accompanied by
declining emissions through the combination of a lower use of
fossil fuels and a switch from coal to gas. The share of nonfossil
fuels in the OECD90 region of the AlB marker scenario
also increases drastically. In 2100, the contribution of nonfossil
energy amounts to 68% of the total primary energy use
of the OECD90 countries, the largest non-fossil fuel share for
this region of all the SRES marker scenarios.
The fossil fuel and industrial COj emission trajectory of the
REF region is even less linear than in the OECD90 region.
Initially, emissions decline from the base year level of 1.3 GtC
to 1.1 GtC in 2020 because of economic restructuring. After
2020, emissions increase, driven by an increased energy
demand to support renewed economic growth (Figure 5-14).
However, after 2050 emissions decline again primarily through
a decrease in population and improved energy efficiency. By
2100, non-fossil fuels in REF contribute 58% of the total
primary energy use and the share of natural gas reaches almost
40%.
The energy and industry CO, emission growth in the ASIA
region of the AlB marker scenario is very high, reflecting rapid
economic growth and high energy demand. By 2100 the total
primary energy use in this region exceeds the 1990 level more
than 10 fold. Standardized COj emissions increase from 1.15
GtC in 1990 to 5.73 GtC in 2050 and then drop to 5.27 GtC in
2100 (Figure 5-14, Table 5-13c). By 2100 contributions from
the two major energy sources, non-fossil fuels and natural gas,
are 69% and 25%, respectively.