Emissions Scenarios - IPCC

200 An Overview of Scenarios
development tendencies captured in the A2 scenario storyline.
Nonetheless, in view of the spirit of the SRES open process
this contrasting scenario is presented in Box 4-6. Regional
GDP growth differs more than global values across the
different model interpretations of the A2 scenario storyline.
A2-MESSAGE and A2-A1M scenarios are harmonized, based
on the marker scenario, at the regional level also, while the A2-
IMAGE and A2-MiniCAM scenarios have significant regional
deviations from the A2 (ASF) marker. In particular, these
scenarios assume stronger GDP/capita growth in the ASIA
region and slower growth in the ALM and REF regions.
4.4.4.5. Bl Scenarios
The Bl scenario storyline assumes high levels of social
consciousness and successful governance that resuh in strong
reductions in income inequalities and social inequity. Growth
in GDP, while being substantial, is qualitatively different
compared to that of other scenarios, as social activities and
environmental conservation are emphasized. Concepts of
"green" GDP. including socially desirable activities such as
childcare, apply in particular in the Bl scenario and qualify its
similarity to other scenarios in terms of monetary value of
GDP In contrast to the worid of scenario Al, the reduction of
income inequalities is not a byproduct, but rather the result of
constant domestic and international efforts. Global GDP
reaches US$328 trillion, which corresponds to an average
annual growth rate of 2.5%, shghtly less than the long-term
historical average. Per capita income differences between the
IND and DEV regions are reduced from 1:16 in 1990 to 1:1.8
by 2100; income disparities within particular regions are
assumed to be even further reduced, consistent with the thread
of the Bl storyline described in Section 4.3. For the IMAGE
model simulation, convergence assumptions were applied in
the foiiowiiig domúns:
• Technology convergence was toward the level of the
productivity frontier region (either Japan or the US).
• Economic structure convergence was toward long-term
sectoral shares of OECD economies (e.g., the US),
which over the long-term implies a decline of the share
of manufacturing sectors, and hence convergence to a
service-oriented econotny.
• Education convergence was to the OECD ratio of
highly skilled workers within the total workforce.
4.4.4.6. Harmonized and Other Bl Scenarios
The global GDP trajectories are all within the proposed
hannonization intervals, except for the Б1 High-MiniCAM (see
Box 4-5) and the Bl-MARIA scenarios in the middle period of
the 21*' century. On the regional level, differences in GDP
trajectories from different models are larger because of the
differences in regional aggregations outiined above in the
discussion of the Al scenario family.
4.4.4.7. B2 Scenarios
Global GDP in B2 is assumed to increase by more than a factor
of 10 during the 2P' century, or at an average annual growth
rate of 2.2%. This growth rate of GDP is similar to the median
GDP growth in the scenario database reviewed in Chapter 2.
Stabilization of global population at less than double cun'ent
levels, as projected in the UN median scenario adopted for B2,
combined with a sustained pace of development implies that a
B2 world generally achieves high levels of affluence. Average
per capita income reaches about US$18,000 by 2100 in the
developing countries, which exceeds the current OECD
averages. In comparison, average per capita GDP reaches
US$54,400 by 2100 in the developed regions, which
corresponds to an income ratio of about 3:1 between industrial
(IND) and now developing (DEV) regions, a considerable
improvement in interregional equity by 2100 (Riahi and
Roehrl, 2000). Noitetheless, given thé nature of the B2 scenario
storyline (Section 4.3), per capita income differences among
the world regions are higher than those in the Al and Bl
scenarios, but much smaller than those in A2.
4.4.4.8. Harmonized and Other B2 Scenarios
The economic growth paths described by the B2-MESSAGE
marker scenario are closely tracked by the B2 quantifications
derived from alternative models at the global level, with the
exception of the B2-IMAGE scenario, which is sfightly
below.^"* Differences at the regional level are larger. For B2-
ASF and B2-MiniCAM, GDP is higher in the ALM and lower
in the ASIA regions, respectively, compared to the B2 marker
scenario and its "fully harmonized" companion B2-AIM. The
latter - like all AIM scenarios - was developed by an
interdisciplinary group of researchers from different countries
in the ASIA region and therefore helps to guide readers as to
which scenario better reflects regional perspectives.
4.4.5. Energy Intensities, Energy Demand, and Structure
of Energy Use
Population and GDP assumptions, along with structural change
and technological change that affect energy efficiency and
energy costs (and prices), drive the demand for energy
services. Given the different model representations of energy
service demands, in this section final energy use is discussed as
a common measurement point across all SRES models and
scenarios. Final energy use per unit economic activity, that is,
energy intensity, is a frequentiy used measure of comparative
efficiency of resource use, and reflects a whole range of
structural, technological, and lifestyle factors (Schipper and
Meyers, 1992).
2^ In B2-IMAGE, economic output is higher in OECD90 and lower in
the other regions compared to the В 2 marker.