The B1 family describes a world with the same population growth as the A1 family. There are rapid changes in economic activity away from production towards a service economy. Clean and efficient technologies are introduced. Like A1, this storyline describes a convergent world. The A2 family describes a world that remains heterogeneous with regional identity being preserved and lower income growth per head.
Global population rises continuously throughout the century.
The introduction of new and efficient technology is less rapid than the other scenarios. The B2 family describes a world with population increasing throughout the 21st century, but at a lower rate than A2. Levels of economic growth and technological development are less than those of A1 and B1. The greenhouse-gas concentrations were calculated from the SRES emissions using separate computer models. The sulphur emissions were converted to concentrations of sulphate aerosol particles concentrations within the climate model itself.