Emissions Scenarios - IPCC

30 Technical Summaiy
Box TS-3: SRES World "Macro-Regions" Used by All Six Modeling Teams
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. The four macro-regions (see Appendix
Ш) are broadly consistent with the allocation of the countries in the United Nations Framework Convention on Climate Change
(UNFCCC, 1992), although the correspondence is not exact due to changes in the countries listed m Annex I of UNFCCC
(1997):
• The OECD90 region groups together all countries belongmg to the Organization for Economic Cooperation and
Development (OECD) as of 1990, the base year of the participatmg models, and corresponds to Annex II countries under
UNFCCC (1992).
• The REF region stands for countries undergoing economic reform and groups together the East European countries and
the Newly Independent States of the former Soviet Union. It includes Armex I countries outside Annex II as defined in
UNFCCC (1992).
• The ASIA region stands for all developing (non-Annex I) countries m Asia.
• The ALM region stands for rest of the world and includes all developing (non-Annex I) countries in Africa, Latm
America, and the Middle East.
In other words, the OECD90 and REF regions together correspond to the developed (industrialised) countries (referred to as
IND in this report) while the ASIA and ALM regions together correspond to the developing countries (referred to as DEV in
this report). The OECD90 and REF regions are consistent with the Annex I countries under the Framework Convention on
Climate Change, while the ASIA and ALM regions correspond to the non-Annex I countries (UNFCCC, 1992).
characteristics as the assumptions about availability of fossilfuel
resources, the rate of energy-efficiency improvements, the
extent of renewable-energy development, and, hence, resultant
GHG emissions. Thus, after the modeling teams had quantified
the key driving forces and made an effort to harmonize them
with the storylines by adjusting control parameters, there still
remained diversity in the assumptions about the driving forces
and in the resultant emissions (see Chapter 4).
The remaining 14 scenarios adopted alternative interprétations
of the four scenario storylines to explore additional scenario
uncertainties beyond differences in méthodologie approaches,
such as different rates of economic growth and variations in
population projections. These variations reflect the "modeling
teams' choice" of alternative but plausible global and regional
development compaied to "harmonized" scenarios and also
stem from the differences in the underlying modeling
approaches. Each of the 40 quantifications of one of the
storylines constitutes a SRES scenario. This approach
generated a large variation and richness in different scenario
quantifications, often with overlapping ranges of main driving
forces and GHG emissions across the four families.
In addition, the Al scenario family branched out into four
distinct scenario groups. They are based on four alternative
technological developments in future energy systems, from
carbon-intensive development to decaibonization. Sitnilar
storyline variations were considered for other scenario
families, but they did not result in genuine scenario groupings
within the respective families. This further increased richness
in different GHG and SO2 emissions paths, because this
variation in the structure of the future energy systems in itself
resulted in a range of emissions almost as large as that
generated through the variation of other main driving forces
such as population and economic development. It should be
noted that future energy systems variations could be applied to
the other storylines, but they may evolve differentiy from those
in Al. They have been introduced into the Al storyline because
of its "high growth with high technology" nature, where
difterences in alternative technology developments translate
into large differences in future GHG emission levels.
Altogether the 40 SRES scenarios fall into seven groups: the
three scenario families, A2, Bl, and B2, plus four groups
within the Al scenario. In the SPM, two of these groups, the
coal and gas and oil intensive groups, were merged into one
fossil-intensive group, leading to six groups.
As in the case of the storylines, no single scenario - whether it
represents a modeler's choice or hatmonized assumptions -
was treated as being more or less "probable" than the others
belonging to the same family. Initially, for each storyline, one
modeling group was given principal responsibility, and the
quantification produced by that group is retened to as the
"marker" scenario for that storyline. The four preliminary
marker scenarios were used in 1998 to solicit comments during
the "open process" and as input for climate modelers in
accordance with a decision of the IPCC Bureau in 1998. The
four marker scenarios were posted on the SRES web site
(www.sres.ciesin) in June 1998 and were subsequently revised
to account for comments and suggestions received tlirough this
open scenario review process that lasted until January 1999. In
addition to many revisions, the marker scenarios were also
harmonized along with the other 26 scenarios that adopted
common assumptions for the main driving forces within the
four respective families. The choice of the markers was based
on extensive discussion of: