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6.2.2. Economic Development
The SRES scenarios span a wide range of future levels of economic activity
(expressed in gross world product). The A1 scenario family with a ("harmonized")
gross world product of US$529 trillion (all values in 1990 US dollars unless
otherwise indicated) in 2100 delineates the SRES upper bound, whereas B2 with
("harmonized") US$235 trillion in 2100 represents its lower bound. The range
of gross world product across all scenarios is even higher, from US$197 to US$550
by 2100.
| Table 6-1: Income per
capita in the world and by SRES region for the IS92 (Leggett et al., 1992)
and four marker scenarios by 2050 and 2100, measured by GDP per capita in
1000 US dollars (at 1990 prices and exchange rates). The additional illustrative
scenarios A1FI and A1T have GDP assumptions similar to the A1B marker, shared
with all harmonized scenarios in the A1 family. |
|
|
Income per Capita by World and Regions (103 1990US$
per capita)
|
|
|
Regions
|
|
| Year |
Scenario |
OECD90 |
REF |
IND |
ASIA |
ALM |
DEV |
WORLD |
|
| 1990 |
SRES MESSAGE |
19.1
|
2.7
|
13.7
|
0.5
|
1.6
|
0.9
|
4.0
|
| 2050 |
IS92a,b
IS92c
IS92d
IS92e
IS92f
A1B
A2
B1
B2 |
49.0
35.2
54.4
67.4
43.9
50.1
34.6
49.8
39.2
|
23.2
14.6
25.5
38.3
21.5
29.3
7.1
14.3
16.3
|
39.7
27.4
43.4
56.9
35.8
44.2
26.1
39.1
32.5
|
3.7
2.2
4.1
5.9
3.3
14.9
2.6
9.0
8.9
|
4.8
2.9
5.4
7.7
4.1
17.5
6.0
13.6
6.9
|
4.1
2.5
4.6
6.6
3.6
15.9
3.9
10.9
8.1
|
9.2
6.3
10.5
13.8
8.1
20.8
7.2
15.6
11.7
|
| 2100 |
IS92a,b
IS92c
IS92d
IS92e
IS92f
A1B
A2
B1
B2 |
85.9
49.2
113.9
150.6
69.7
109.2
58.5
79.7
61.0
|
40.6
17.6
51.3
96.6
31.3
100.9
20.2
52.2
38.3
|
69.5
36.5
88.8
131.0
54.9
107.3
46.6
72.8
54.4
|
15.0
6.4
20.3
34.6
11.9
71.9
7.8
35.7
19.5
|
14.2
5.8
17.7
33.0
10.7
60.9
15.2
44.9
16.1
|
14.6
6.1
19.1
33.8
11.4
66.5
11.0
40.2
18.0
|
21.5
10.1
28.2
46.0
16.8
74.9
16.1
46.6
22.6
|
|
Although the SRES scenarios span a wide range, still lower and higher gross
world product levels can be found in the literature (see Chapters 2,
3, and 4). Uncertainties in future
gross world product levels are governed by the pace of future productivity growth
and population growth, especially in developing regions. Different assumptions
on conditions and possibilities for development "catch-up" and for narrowing
per capita income gaps in particular explain the wide range in projected future
gross world product levels. Given a qualitatively negative relationship between
population growth and per capita income growth discussed in Chapters 2
and 3, uncertainties in future population growth rates
tend to narrow the range of associated gross world product projections. High
population growth would, ceteris paribus, lower per capita income growth, whereas
low population growth would tend to increase it. This relationship is evident
in empiric data - high per capita income countries are generally also those
that have completed their demographic transition. The affluent live long and
generally have few children. (Exceptions are some countries with small populations,
high birth rates, and significant income from commodity exports.) This relationship
between affluence and longevity again identifies development as one of the most
important indicators of human well being. Yet even assuming this relationship
holds for an extended time into the future, its quantification is subject to
considerable theoretic and empiric uncertainties (Alcamo et al., 1995).
|
Figure 6-3: Global primary
energy structure, shares (%) of oil and gas, coal, and non-fossil (zero-carbon)
energy sources - historical development from 1850 to 1990 and in SRES
scenarios. Each corner of the triangle corresponds to a hypothetical
situation in which all primary energy is supplied by a single source
- oil and gas on the top, coal to the left, and non-fossil sources (renewables
and nuclear) to the right. Constant market shares of these energies
are denoted by their respective isoshare lines. Historical data from
1850 to 1990 are based on Nakicenovic et al. (1998). For 1990
to 2100, alternative trajectories show the changes in the energy systems
structures across SRES scenarios. They are grouped by shaded areas for
the scenario families A1, A2, B1, and B2 with respective markers shown
as lines. In addition, the four scenario groups within the A1 family,
A1, A1C, A1G, and A1T, that explore different technological developments
in the energy systems, are shaded individually. In the SPM, the A1C
and A1G scenario groups are combined into the fossil-intensive A1FI
scenario group. For comparison the IS92 scenario series are also shown,
clustering along two trajectories (IS92c,d and IS92a,b,e,f). For model
results that do not include non-commercial energies, the corresponding
estimates from the emulations of the various marker scenarios by the
MESSAGE model were added to the original model outputs.
|
Two of the SRES scenario families, A1 and B1, explicitly explore alternative
pathways to gradually close existing income gaps. As a reflection of uncertainty,
development "catch-up" diverges in terms of geographically distinct economic
growth patterns across the four SRES scenario families. Table
6-1 summarizes per capita income for SRES and IS92 scenarios for the four
SRES world regions. SRES scenarios indicate a smaller difference between the
now industrialized and developing countries compared with the IS92 scenarios.
This tendency toward a substantially narrower income "gap" compared with the
IS92 scenarios overcomes one of the major shortcomings of the previous IPCC
scenarios cited in the literature (Parikh, 1992).
6.2.3. Structural and Technological Change
In this brief summary of the SRES scenarios, structural and technological changes
are illustrated by using energy and land use as examples. These examples are
characteristic for the driving forces of emissions because the energy system
and land use are the major sources of GHG and sulfur emission. Chapter
4 gives a more detailed treatment of the full range of emissions driving
forces across the SRES scenarios.
6.2.3.1. Energy Systems
Figure 6-3 illustrates that the change of world
primary energy structure diverges over time. It shows the contributions of individual
primary energy sources - the percentage supplied by coal, that by oil and gas,
and that by all non-fossil sources taken together (for simplicity of presentation
and because not all models distinguish between renewables and nuclear energy).
Each corner of the triangle corresponds to a hypothetical situation in which
all primary energy is supplied by a single source - oil and gas, coal at the
left, and non-fossil sources (renewables and nuclear) to the right. Historically,
the primary energy structure has evolved clockwise according to the two "grand
transitions" (discussed in Chapter 3) that are shown by
the two segments of the "thick black" curve. From 1850 to 1920 the first transition
can be characterized as the substitution of traditional (non-fossil) energy
sources by coal. The share of coal increased from 20% to about 70%, while the
share of non-fossils declined from 80% to about 20%. The second transition,
from 1920 to 1990, can be characterized as the replacement of coal by oil and
gas (while the share of non-fossils remained essentially constant). The share
of oil and gas increased to about 50% and the share of coal declined to about
30%.
Figure 6-3 gives an overview of the divergent evolution
of global primary energy structures between 1990 and 2100, regrouped into their
respective scenario families and four A1 scenarios groups that explore different
technological developments in the energy systems. The SRES scenarios cover a
wider range of energy structures than the previous IS92 scenario series, which
reflects advances in knowledge on the uncertainty ranges of future fossil resource
availability and technological change.
In a clockwise direction, A1 and B1 scenario groups map the structural transitions
toward higher shares of non-fossil energy in the future, which almost closes
the historical "loop" that started in 1850. The B2 scenarios indicate a more
"moderate" direction of change with about half of the energy coming from non-fossil
sources and the other half shared by coal on one side and oil and gas on the
other. Finally, the A2 scenario group marks a stark transition back to coal.
Shares of oil and gas decline while non-fossils increase moderately. What is
perhaps more significant than the diverging developments in these three marker
scenarios is that the whole set of 40 scenarios covers virtually all possible
directions of change, from high shares of oil and gas to high shares of coal
and non-fossils. In particular, the A1 scenario family covers basically the
same range of structural change as all other scenarios together. In contrast,
the IS92 scenarios cluster into two groups; one contains IS92c and IS92d and
the other the four others. In all of these the share of oil and gas declines,
and the main structural change occurs between coal on the one hand and non-fossils
on the other. This divergent nature in the structural change of the energy system
and in the underlying technological base of the SRES results in a wide span
of future GHG and sulfur emissions.
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