Emissions Scenarios - IPCC

Background and Overview 71
SRES Scenarios
Figure 1-4: Schematic illustration of SRES scenarios. The
four scenario "families" are illustrated, very simplistically, as
branches of a two-dimensional tree. In reality, the four
scenario families share a space of a much higher
dimensionality given the numerous assumptions needed to
define any given scenario in a particular modeling approach.
The schematic diagram illustrates that the scenarios build on
the main driving forces of GHG emissions. Each scenario
family is based on a common specification of some of the
main driving forces.
• Integrated Model to Assess the Greenhouse Effect
(IMAGE) from the National Institute for Public Health
and Environmental Hygiene (RIVM) (Alcamo et al.,
1998; de Vries et ai, 1994, 1999, 2000), used in
connection with the Dutch Bureau for Economic Policy
Analysis (СРВ) WorldScan model (de Jong and Zalm,
1991), the Netherlands;
• Multiregional Approach for Resource and Industry
Allocation (MARIA) from the Science University of
Tokyo in Japan (Mori and Takahashi, 1999; Mori,
2000);
• Model for Energy Supply Strategy Alternatives and
their General Environmental Impact (MESSAGE) from
the Intemational Institute of Applied Systems Analysis
(IIASA) in Austria (Messner and Strubegger, 1995;
Riahi and Roehrl, 2000); and the
• Mini Climate Assessment Model (MiniCAM) from the
Pacific Northwest National Laboratory (PNNL) in the
USA (Edmonds et al., 1994, 1996a, 1996b).
These six models are representative of emissions scenario
modeling approaches and different lA frameworks in the
literature and include so-called top-down and bottom-up
models.
The six models have different regional aggregations. The
writing team decided to group the various global regions into
four "macro-regions" common to all different regional
aggregations across the six models. The four macro-regions
(see Appendix III) are broadly consistent with the allocation of
the countries in the United Nations Framework Convention on
Climate Change (UNFCCC, 1997), although the
correspondence is not exact because of changes in the
countries listed in Annex 1 of the UNFCCC:
• The OECD90 region groups together all countries that
belong to the OECD as of 1990, the base year of the
participating models, and coiTesponds to Annex II
countries under UNFCCC (1992).
• The REF region comprises tiiose countries undergoing
economic reform and groups together the East
European countries and the Newly Independent States
of the former Soviet Union. It includes Annex I
countries outside Annex II as defined in UNFCCC
(1992).
• The ASIA region stands for all developing (non-Annex
I) countries in Asia.
• The ALM region stands for rest of the world and
includes all developing (non-Annex I) countries in
Africa, Latin America and the Middle East.
In other words, the OECD90 and REF regions together
correspond to the developed (i.e., industrialized) countries
while the ASIA and ALM regions together coiTespond to the
developing countries. The OECD90 and REF regions are
consistent with the Annex I countries in the Framework
Convention on Climate Change, while the ASIA and ALM
regions correspond to the non-Annex I countries.
/. 7.3. The Range of SRES Emissions and their
Implications
The 40 SRES scenarios cover the full range of GHG and SO,
emissions consistent with the storylines and underlying ranges
of driving forces from studies in the literature as documented
in the SRES database. The four marker scenarios are
characteristic of the four scenario families and jointly capture
most of the ranges of emissions and driving forces spanned by
the full set of scenarios. Figure 1-6 illustrates the range of
global energy-related and industrial CO^ emissions for the 40
SRES scenarios against the background of all the emissions
scenarios in the SRES scenario database shown in Figure 1-3.
Figure 1-6 also shows a range of emissions of the four scenario
families
Figure 1-6 shows that the SRES scenarios cover most of the
range of global energy-related CO2 emissions from the
literature, from the 95* percentile at the high end of the
distribution down to low emissions just above the 5* percentile
of the distribution. Thus, they only exclude the most extreme
emissions scenarios found in the literature - those situated in
the tails of the distribution. What is perhaps more important is