Emissions Scenarios - IPCC

274 Emission Scenarios
180
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2010 2030 2050 2070 2040
Figure 5-12: Standardized global SO2 emissions for SRES scénarios, classified into four scenario families (each denoted by a
different color code - Al, red; A2, brown; Bl, green; В2, blue). Marker scenarios are shown with thick lines without ticks,
globally harmonized scenarios with thin lines, and non-harmonized scenarios with thin, dotted lines (see Table 4-3). Black lines
show percentiles, means, and medians for SRES scenarios. For numbers on the two additional illustrative scenarios AlFI and
AIT see Appendix VII.
Russia), uncertainties in sulfur contents of fuels (especially
coal) in many regions, and the use of different base years for
development of sulfur inventories. For instance, inventories
and scenario studies for China and Centrally Planned Asia give
a range of sulfur emissions that differ by more than a factor of
two (8.4 to 18 MtS) for the year 1990 (Grübler, 1998).
Base-year differences in the available data sources are
especially important because regional sulfur emissions trends
have changed drastically in the past decade. Although they
decreased strongly in Europe and North America as a result of
sulfur control policies, they increased rapidly in Asia with
growing energy demand and coal use. For instance, between
1980 and 1995 sulfur emissions declined by 59% in Western
Europe and Russia (albeit for entirely different reasons -
environmental policy limiting sulfur emissions in Westem
Europe versus a massive economic depression in Russia), by
37% in Eastern Europe, and by 36% in North America (ECE,
1997). Conversely, emissions in China rose rapidly, from an
estimated 6.6 MtS in 1985 to 9.1 MtS in 1994, or by 38%
(Sinton, 1996; Dadi et al., 1998). These diverging emission
trends and their rapid changes also require a continuous
updating of available gridded sulfur emission inventories (e.g.,
Dignon and Hameed, 1989; Spiro et al., 1992; Benkovitz et al.,
1996; Olivier et al., 1996) that in, some instances, still rely on
outdated 1980 emissions data.
at the regional level. The range is within the range of values
given by global inventories.
Model differences at the regional level are even larger, which
reflects the greater uncertainty of emission inventories at this
level, particularly outside the OECD countries. To standardize
sulfur emissions, the number of SRES reporting regions was
increased to six regions, by splitting Latin America from the
ALM region and Centrally Planned Asia and China from ASIA.
Important differences in economic development status and
resource endowments lead to different patterns of sulfur
emissions across all SRES scenarios. Regional emissions were
standardized (see Box 5-1) and then aggregated to the global
level. Global standardized base-year emissions for 1990 for the
SRES scenarios are equal to 70.9 MtS, in line with the literature
range of global emission inventories given above. The regional
sulfur emission profiles were also used to generate spatially
gridded emission patterns (see Section 5.6.2 below).
Concerning future emissions of sulfur, the SRES scenarios
reflect recent literature and trends of sulfur control scenarios, as
well as the conclusions from the 1994 evaluation of the IS92
scenarios (Alcamo et al., 1995). Despite considerable scenario
variability, all scenarios portray similar emission dynamics - at
various future dates (between 2020-2030 and 2070, depending
Global base-year (1990) sulfur emission values from the SRES
models range from 63 to 77 MtS, with the addition of 3 MtS
from international shipping.^ This difference reflects the
existing uncertainty in sulfur emission estimates, particularly
^ FoUowing UN energy statistics and IPCC inventory practices,
intemational bunker fuels are included in global totals, but not in
national/regional subtotals (and thek aggregates to global totals).
Hence, bunker fuels are reported separately here.