Emissions Scenarios - IPCC

Emission Scenarios 287
-OECD90
REF
—•
ASIA
- - • - • A L M
» WORLD
1990 2010 2030 2050 2070 2090
1990 2010 2030 2050 2070 2090
-OECD90
- • • - • A L M
WORLD
Figure 5-16: Regional and global CO,
emissions in the four SRES markers
scenarios AIB, A2, Bl, and B2, shown
as an index (1990 = 100). The numbers
for the additional two illustrative
scenarios for the AlFI and AIT
scenario groups noted in the Summary
for Policymakers can be found in
Appendix VII.
in the industrialized regions. It also illustrates that the global
pattern IS strongly influenced by the developing region
trajectories. Furthermore, reflecting different development
perspectives in the four SRES families, CO^ emissions grow
differently in ASIA and ALM. In the AIB marker, emission
trajectories in ALM and ASIA are roughly parallel over the
entire time horizon. In the В1 marker, this is only true in the
earlier years. As the emission of ALM peaks and then declines
later than that of ASIA, emission trajectories diverge strongly
in the second half of the 2P' century. In the A2 marker,
emissions in ALM start to grow at a lower rate than in ASIA,
but subsequently catch up and later the two are again fairly
close. Finally, in the B2 marker, ALM emissions initially grow
at a modest rate, close to those for the OECD90 region and the
world average. In later years, the growth in ALM exceeds the
global rate, but total carbon emissions remain far below those
in the ASIA region (Figures 5-15, 5-16).
5.6.1.4. Methane
The resultant CH^ emission trajectories in the four SRES
markers are displayed in Figure 5-17. By 2020, regional
differences between the four markers are minimal. In 2050, the
largest difference is the relative share of the REF region in the
A2 marker, attributable primarily to an increased coal and gas
production in this region. By 2100, the A2 marker has the
largest CH^ emissions in all the regions as compared to the
other markers (Tables I3a-d, Figure 5-17). This arises from the
"heterogeneous" nature of the A2 storyline, in which each
region has to rely primarily on its own resources and progress
in the renewable energy sector is quite limited. The second
highest methane emissions are attained in the B2 marker,
which also has a "regional" orientation, but with a more
environmentally sustainable emphasis as compared to the A2
marker. Starting from 2100, both AIB and Bl markers have
notably lower CH^ emissions in all the regions in comparison
with the A2 and B2 markers (Figure 5-17). The regional
emission allocation changes considerably from 1990 to 2100;
all four markers project much greater percentages of emissions
in the developing regions (ASIA and ALM).
5.6.1.5. Nitrous Oxide
The relative shares of the OECD90, REF, ASIA, and ALM
regions in the base year NjO emissions are 39%, 9%. 34%, and
18%, respectively (Figure 5-18). The OECD90 emissions
remain quite stable over the 2F' century in all the markers,
except A2 in which emissions increase from 2.6 MtN in 1990
to almost 4 MtN in 2100. Emissions in the ASIA and REF
regions increase in the A2 marker, decline in the В1 marker
(after an initial increase in ASIA), and do not change
significantly in the AI and B2 markers. Finally, the ALM NjO
emissions grow quickly in the A2 marker and remain relatively
flat in the other markers. The relatively small changes in the