Emissions Scenarios - IPCC

Emission Scénarios 263
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1990 2010 2030 2050 2070 2090
Figure S-8c: Standardized global NjO emissions in the Bl family scenarios. The marker scenario is shown with a thick line
without ticks, the globally harmonized scenarios with thin lines, and the non-harmonized scenarios with thin, dotted lines (see
Table 4-3).
5.4.2.3. Bl Scenario Family
The spread of emissions in the В1 family is quite large.
The high-end reflects the agricultural assumptions used in the
MiniCAM model, in which continued growth in meat
production is driven by increases in per capita consumption
that more than offset the reduction in population size (Figure 5-
8c). The Bl-AIM scenario has emissions near the low end of
the range, because fertilizer use in developing countries is
assumed to level off and better management increases
productivity. Emissions from animal waste, mobile sources,
and other sources in Bl-AIM are nearly constant. The Bl-
IMAGE scenario (Bl family marker) has slowly increasing
emissions through to 2050, which predominately originate
from increases in livestock and the use of synthetic fertilizer
(Table 5-6). After 2050, these emissions decline as the
population size and associated demand for animal products
declines (Figure 5-8c). The Bl-ASF scenario has an
intermediate emission trajectory with a maximum of 11.5 MtN
in 2050 and a subsequent decline to 9.3 MtN by 2100 (Figure
5-8c). The two illustrative scenarios AlG-MiniCAM and AIT­
MESSAGE display similar patterns of methane emissions as
the A2 and В1 marker scenarios, respectively, and are therefore
not discussed separately here.
the sector (Table 5-6). Slow growth in agriculture and energyrelated
emissions and declines of emissions from other sectors
result in a relatively flat emissions proñle (Figure 5-8d).
Emissions in the B2-ASF scenario are between the middle of
the family range and its high end. The continuous increase in
emissions in the B2-ASF scenario (which lie between the
middle and high end of the family range) occurs through
growth in nitrogen fertilizer use, in animal wastes, and in
mobile sources. It is driven by increases in population and, to
a smaller extent, by per capita increases in consumption of
meat and dairy products.
5.4.2.5. Inter-Family Comparison
The allocation of N2O emissions into source categories for the
SRES marker scenarios is shown in Table 5-6. Separate
emissions estimates for fertilized soils and manure were not
available for all scenarios. As the emissions in Table 5-6 have
not been standardized (see Box 5-1), base-year 1990 (and
2000) emissions are not the same for the different scenarios. In
general, base-year emissions are likely to have greater
differences at finer levels of detail. These differences result
from different model calibrations, different model
methodologies, and different classification schemes.
5.4.2.4. B2 Scenario Family
The B2 family of scenarios covers a large range of N2O
emissions, similar to that found for the Al family (see Figure
5-7). In the B2-MESSAGE scenario (B2 family marker), which
has the lowest emissions in the family, improvements in
agricultural productivity exceed increases in the demand for
agricultural products and signiñcantly slow emission growth in
Emissions from fertilized soils and manure from agricultural
animals dominate N2O emissions in all the SRES markers. The
fraction of total emissions from these two sources increases to
about 80% in the A2, Bl, and B2 marker scenarios, while the
agricultural fraction remains roughly the same over the 2P'
century in the AlB marker. As discussed in Section 5.4.2, the
range of future emissions is similar across each scenario family
when all storyline inteфretations are considered. Therefore,