SRES Scenarios

SRES Storylines

[from Special Report on Emissions Scenarios]

A1: This 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. A major underlying theme is convergence among regions of the globe, with a substantial reduction over time in regional differences in per capita income.  The A1 family is split into 3 groups that describe alternative directions of technological change in the energy system: fossil intensive (A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B).

B1: This scenario family describes a convergent world with the same population trajectory as in the A1 storyline, but with rapid changes towards a service and information economy, with reductions in material intensity, and the introduction of clean and resource-efficient technologies.

A2: This scenario family describes a very heterogeneous world, with the underlying theme of self-reliance and preservation of local identities. Global population increases continuously, economic development is regionally oriented, and per capita economic growth and technological change are more fragmented and slower than in the other storylines.

B2: This scenario family describes a world that emphasises local solutions to economic, social and environmental sustainability (i.e., a heterogeneous world as in A2). Global population increases continuously at a rate slower than A2, with intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines.


This slide is only to be used in people are interested in understanding how the socio-economic scenarios are derived.


Schematic illustration of the four SRES scenarios as branches of a two-dimensional tree. The two dimensions indicate the relative orientation of the different scenario storylines toward economic or environmental concerns and global and regional scenario development patterns, respectively. The A1 storyline branches out into different groups of scenarios to illustrate that alternative development paths are possible within one scenario family.