Emissions Scenarios - IPCC

Emission Scenarios 249
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|Energy & Industry
A2 Family
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1990 2010 2030 2050 2070 2090
Figure 5-3b: Global CO^ emissions from fossil fuels and industry in the A2 scenario family (standardized). 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).
These rapid teclinical changes, as well as relatively low rates of
growth in the productivity of biomass and other non-fossil
sources, imply a world that is heavily reliant on oil and gas.
The three coal-based scenarios in this group (AIC-MESSAGE,
AlC-MiniCAM, and AIC-AIM) assume rapid increases in the
efficiency of synthetic fuel production, as well as relatively
limited oil and gas resources.
Three advanced technology or AIT scenarios fall in either the
"low" or the "medium-low" cumulative emissions categories
(Table 5-2). The AIT-MARIA scenario (Mori, 2000) achieves
very low carbon emissions tln'ough the combination of a low
final energy use (54% of that in A IB-AIM) and a rapid
increase in the importance of non-fossil energy technologies in
the primary energy system (81% by 2100).
The resultant CO2 emissions range of all the AI family
scenarios is so wide that most of the remaining SRES scenarios
fall within its bandwidth, horn 4.3 to 37 GtC in 2100. The total
cumulative carbon emissions of the AI family scenarios also
span a very wide range, from around 1000 GtC to more than
2500 GtC (Figure 5-1, Table 5-2).
53.1.2. A2 Scenario Family
Global CO2 emissions in the A2 marker scenario implemented
using the ASF model (Sankovski et al, 2000) increase by more
than fourfold over their 1990 level, to reach 29 GtC by 2100
(Figure 5.3b). Total cumulative carbon emissions from the A2-
ASF scenario amount to 1860 GtC by 2100.
In other A2 scenarios, CO2 emissions range from 17 GtC
(A2G-IMAGE5) to 33 GtC (A2-AIM) by 2100. The
harmonized A2-MESSAGE scenario and the A2-MiniCAM
scenario have very similar global COj emissions as compared
to the marker. Slightly higher emissions, primarily caused by
higher primary energy use, are generated in the A2-AIM
scenario. Unlike the rest of the A2 family scenarios, the A2G-
IMAGE scenario yields constant emissions after 2050. This
emission trajectory is explained by the combination of a lower
energy demand and a larger share of natural gas in the energy
supply mix (see Chapter 4 for more details). Total cumulative
carbon emissions in the A2 scenario group range between I7I0
and 1860 GtC by 2100.
A variant of the A2 storyline, developed with the MiniCAM
model (A2-A1-MiniCAM), explores a world in which
economic growth and population follow a "hybrid" trajectory,
which have traits of both the A2 and Al storylines. As
In the A2 scenario family, altemative energy technologies
develop relatively slowly and fossil fuels maintain their
dominant position in the energy supply mix. As oil and gas
resources become scarcer and non-fossil alternatives remain
underdeveloped, coal gains the leading role. Its share in the
energy mix ranges from 45% to 52% in the harmonized
scenarios (A2-ASF, A2-MESSAGE) and in other scenarios
with similar input assumptions (A2-MiniCAM and A2-AIM).
' The IMAGE results for the A2 and B2 scenarios are based on
preliminary model experiments camed out in March 1998. As a result
of limited resources it has not been possible to re-run these
experiments. Hence, unlike for the IMAGE Al and Bl scenarios, the
IMAGE team has not been able to provide background data and
details for these scenario calculations and the population and
economic growth assumptions are not harmonized fully.