Emissions Scenarios - IPCC

Technical Summary 29
effectively six equally sound groups after the merging of the
two fossil-intensive groups in the SPM - that share common
assumptions of some of the key driving forces and are thus not
independent of each other.
All four storylines and scenario families describe future worlds
that are generally more affluent compared to the current
situation. They range from very rapid economic growth and
technological change to high levels of environmental
protection, from low to high global populations, and from high
to low GHG emissions. What is perhaps even more important
is that all the storylines describe dynamic changes and
transitions in generally different directions. Although they do
not include additional climate initiatives, none of them are
policy free. As time progresses, the storylines diverge from
each other in many of their characteristic features. In this way
they allow us to span the relevant range of GHG emissions and
different combinations of their main sources.
7. Quantitative Scenarios and Modeling
Approaches
The storylines were essentially complete by January 1998.
After determining the basic features and driving forces for each
of the four storylines, the six modeling groups represented on
the writing team (on a voluntary basis) began quantifying
them. The six modeling groups that quantified the storylines
are listed in Box TS-2. Each model quantification of a storyline
constitutes a scenario, and all scenarios derived from one
storyline constitute a scenario family. The six models are
representative of different approaches to modeling emissions
scenarios and different integrated assessment (lA) frameworks
in the literature and include so-called top-down and bottom-up
models. The writing team recommends that IPCC or a similar
international institution should assure participation of
modeling groups around the world and especially from
developing countries in any future scenario development and
assessment efforts. Clearly, this would also require resources
specifically directed at assisting modeling groups from
developing countries. Indeed, a concerted effort was made to
engage modeling groups and experts from developing
countries in SRES as a direct response to the recommendations
of the last IPCC scenario evaluation (Alcamo et al., 1995).
The six models have different regional aggregations. The
writing team decided to group the various global regions into
four "macro-regions" common to all the different regional
aggregations across the six models. Box TS-3 indicates that the
four macro-regions (see Appendix III) are broadly consistent
with the allocation of countries in the United Nations
Framework Convention on Climate Change (UNFCCC, 1992),
although the correspondence is not exact because of changes in
the countries listed in Annex I of UNFCCC (1997).
All the qualitative and quantitative features of scenarios
belonging to the same family were set to conform to the
corresponding features of the underlying storyline. Together,
26 scenarios were "harmonized" to share agreed common
assumptions about global population and GDP (gross domestic
product) development (a few that also share common
population, GDP, and final energy trajectories at the level of the
four SRES macro-regions are called "fully harmonized," see
Section 4.1. in Chapter 4). Thus, the harmonized scenarios are
not independent within each of the four families. However,
scenarios within each family vary quite substantially in such
Box TS-2: The Six IVIodeling Teams that Quantified the 40 SRES Scenarios
In all, six models were used to generate the 40 scenarios:
• Asian Pacific Integrated Model (AIM) from the National Institute of Environmental Studies in Japan (Morita et al.,
1994);
• Atmospheric Stabilizafion Framework Model (ASF) from ICF Consulting in the USA (Lashof and Tirpak, 1990; Pepper
etal, 1992, 1998; Sankovski et al, 2000);
• 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 al, 1994, 1999, 2000), used m 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
• 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. For a more detailed description of the modeling approaches see
Appendix IV.