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The Emission Scenarios of the IPCC Special Report on Emission Scenarios (SRES)

A1. The A1 storyline and scenario family describes a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies.

Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system. The three A1 groups are distinguished by their technological emphasis: fossil intensive (A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies).

A2. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines.

B1. The B1 storyline and scenario family describes a convergent world with the same global population, that peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.

B2. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.

An illustrative scenario was chosen for each of the six scenario groups A1B, A1FI, A1T, A2, B1 and B2. All should be considered equally sound.

The SRES scenarios do not include additional climate initiatives, which means that no scenarios are included that explicitly assume implementation of the United Nations Framework Convention on Climate Change or the emissions targets of the Kyoto Protocol.

Emission scenarios are not assessed in this Working Group One report of the IPCC. This box summarizing the SRES scenarios is taken fromthe TAR and has been subject to prior line by line approval by the Panel.

Source & © IPCC Climate Change 2007:
The Physical Science Basis, Summary for Policymakers (2007) , p18

Related publication:
Climate Change (2007) homeClimate Change 2007 Update
Other Figures & Tables on this publication:

Figure SPM-1. (WGI) Changes in Greenhouse Gases from Ice-core and Modern Data

Figure SPM-2. (WGI) Radiative Forcing Components

Figure SPM-3. (WGI) Changes in Temperatures, Sea Level and Snow Cover between 1850 and 2010

Figure SPM-4. (WGI) Global and Continental Temperature Change

Figure SPM-5. (WGI) Multi-model Averages and Assessed Ranges for Surface Warming

Figure SPM-6. (WGI) AOGCM Projections of Surface Temperatures

Figure SPM-7. (WGI) Projected Patterns of Precipitation Changes

Figure SPM-1. (WGII) Changes in physical and biological systems and surface temperature 1970-2004

Figure SPM-2. (WGII) Key impacts as a function of increasing global average temperature change

Figure SPM-1. (WGIII) Emissions of different greenhouse gases 1970-2004

Figure SPM-2. (WGIII) Relative global development of indicators of income, energy supply, CO2 emissions and population for 1970 to 2004

Figure SPM-3a. (WGIII) Distribution of regional per capita greenhouse gas emissions

Figure SPM-3b. (WGIII) Distribution of regional greenhouse gas emissions per unit of income

Figure SPM-4. (WGIII) Global greenhouse gas emissions for 2000, 2030 and 2100

Figure SPM-5a/5b. (WGIII) Estimated global economic mitigation potential

Figure SPM-6. (WGIII) Estimated economic mitigation potential in 2030 as a function of carbon price

Figure SPM-7. (WGIII) Emissions pathways of mitigation scenarios for alternative categories of stabilization levels

Figure SPM-8. (WGIII) Relationship between stabilization scenario categories and equilibrium global mean temperature change

Figure SPM-9. (WGIII) Cumulative emissions reductions for alternative mitigation measures for 2000 to 2030 (left-hand panel) and for 2000-2100 (right-hand panel)

Global greenhouse gas emissions 1970-2004

Table SPM-1. (WGI) Observed rate of sea level rise and estimated contributions from different sources.

Table SPM-2. (WGI) Recent trends, assessment of human influence on the trend, and projections for extreme weather events for which there is an observed late 20th century trend.

Table SPM-3. (WGI) Projected globally averaged surface warming and sea level rise at the end of the 21st century.

Table SPM-1. (WGII) Examples of possible impacts of climate change due to changes in extreme weather and climate events based on projections to the mid- to late 21st century. These do not take into account any changes or developments in adaptive capacity. Examples of all entries are to be found in chapters in the full Assessment (see source at top of columns). The first two columns of the table (shaded yellow) are taken directly from the Working Group I Fourth Assessment (Table SPM-2). The likelihood estimates in Column 2 relate to the phenomena listed in Column 1.

Table SPM-4. (WGIII) Estimated global macro-economic costs in 2030a for least-cost trajectories towards different long-term stabilization levels.b,c

Table SPM-5. (WGIII) Characteristics of post-TAR stabilization scenarios [Table TS 2, 3.10]a

Table SPM-6. (WGIII) Estimated global macro-economic costs in 2050 relative to the baseline for least-cost trajectories towards different long-term stabilization targetsa [3.3, 13.3]

Table SPM-7. (WGIII) Selected sectoral policies, measures and instruments that have shown to be environmentally effective in the respective sector in at least a number of national cases.

Table SPM-1. (WGIII) Global economic mitigation potential in 2030 estimated from bottom-up studies.

Table SPM-2. (WGIII) Global economic mitigation potential in 2030 estimated from top-down studies.

Table SPM-3. (WGIII) Key mitigation technologies and practices by sector. Sectors and technologies are listed in no particular order. Non-technological practices, such as lifestyle changes, which are cross-cutting, are not included in this table (but are addressed in paragraph 7 in this SPM).

Figure SPM-2. (WGII) Key impacts as a function of increasing global average temperature change

Figure SPM-6. (WGIII) Estimated economic mitigation potential in 2030 as a function of carbon price

Likelihood

The Emission Scenarios of the IPCC Special Report on Emission Scenarios (SRES)

Box SPM-2 (WGIII) Mitigation potential and analytical approaches

Box SPM-3 (WGIII) Assumptions in studies on mitigation portfolios and macro-economic costs

Box SPM-4 (WGIII) Modelling induced technological change

Parties & Observers of the UNFCCC