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Preface
The Intergovernmental Panel on Climate Change (IPCC) was established jointly
by the World Meteorological Organisation (WMO) and the United Nations Environment
Programme (UNEP) to assess periodically the science, impacts, and socio-economics
of climate change and of adaptation and mitigation options. The IPCC provides,
on request, scientific and technical advice to the Conference of the Parties
to the United Nations Framework Convention on Climate Change (UNFCCC) and its
bodies. In response to a 1994 evaluation of the earlier IPCC IS92 emissions
scenarios, the 1996 Plenary of the IPCC requested this Special Report on Emissions
Scenarios (SRES) (see Appendix I for the Terms of Reference). This report was
accepted by the Working Group III (WGIII) plenary session in March 2000. The
long-term nature and uncertainty of climate change and its driving forces require
scenarios that extend to the end of the 21st century. This report describes
the new scenarios and how they were developed.
The SRES scenarios cover a wide range of the main driving forces of future
emissions, from demographic to technological and economic developments. As required
by the Terms of Reference, none of the scenarios in the set includes any future
policies that explicitly address climate change, although all scenarios necessarily
encompass various policies of other types. The set of SRES emissions scenarios
is based on an extensive assessment of the literature, six alternative modelling
approaches, and an "open process" that solicited wide participation and feedback
from many groups and individuals. The SRES scenarios include the range of emissions
of all relevant species of greenhouse gases (GHGs) and sulfur and their driving
forces.
The SRES writing team included more than 50 members from 18 countries who represent
a broad range of scientific disciplines, regional backgrounds, and non-governmental
organizations (see Appendix II). The team, led by Nebojsa Nakicenovic of
the International Institute for Applied Systems Analysis (IIASA) in Austria,
included representatives of six scenario modeling groups and lead authors from
all three earlier IPCC scenario activities - the 1990 and 1992 scenarios and
the 1994 scenario evaluation. The SRES preparation included six major steps:
- analysis of existing scenarios in the literature;
- analysis of major scenario characteristics, driving forces, and their relationships;
- formulation of four narrative scenario "storylines" to describe alternative
futures;
- quantification of each storyline using a variety of modelling approaches;
- an "open" review process of the resultant emission scenarios and their assumptions;
and
- three revisions of the scenarios and the report subsequent to the open review
process, i.e., the formal IPCC Expert Review and the final combined IPCC Expert
and Government Review.
As required by the Terms of Reference, the SRES preparation process was open
with no single "official" model and no exclusive "expert teams." To this end,
in 1997 the IPCC advertised in relevant scientific journals and other publications
to solicit wide participation in the process. A web site documenting the SRES
process and intermediate results was created to facilitate outside input. Members
of the writing team also published much of their background research in the
peer-reviewed literature and on web sites.
In June 1998, the IPCC Bureau agreed to make the unapproved, preliminary scenarios
available to climate modelers, who could use the scenarios as a basis for the
assessment of climatic changes in time for consideration in the IPCC's Third
Assessment Report. We recommend that the new scenarios be used not only in the
IPCC's future assessments of climate change, its impacts, and adaptation and
mitigation options, but also as the basis for analyses by the wider research
and policy community of climate change and other environmental problems.
Ogunlade Davidson and Bert Metz
Co-chairs of IPCC WGIII
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