often made in the context of a specific scenario family. According to the IPCC, all SRES scenarios are considered "neutral". None of the SRES scenarios project future disasters or catastrophes, e.g., wars and conflicts, and/or environmental collapse. The scenarios are not described by the IPCC as representing good or bad pathways of future social and economic development. Scenario families Scenario families contain individual scenarios with common themes. The six families of scenarios discussed in the IPCC's Third Assessment Report (TAR) and Fourth Assessment Report (AR4) are A1FI, A1B, A1T, A2, B1, and B2. The IPCC did not state that any of the SRES scenarios were more likely to occur than others, therefore none of the SRES scenarios represent a "best guess" of future emissions. Scenario descriptions are based on those in AR4, which are identical to those in TAR. A1 The A1 scenarios are of a more integrated world. The A1 family of scenarios is characterized by: Rapid economic growth. A global population that reaches 9 billion in 2050 and then gradually declines. The quick spread of new and efficient technologies. A convergent world - income and way of life converge between regions. Extensive social and cultural interactions worldwide. There are subsets to the A1 family based on their technological emphasis: A1FI - An emphasis on fossil-fuels (Fossil Intensive). A1B - A balanced emphasis on all energy sources. A1T - Emphasis on non-fossil energy sources..... A2 The A2 scenarios are of a more divided world. The A2 family of scenarios is characterized by: A world of independently operating, self-reliant nations. Continuously increasing population. Regionally oriented economic development. High emissions B1 The B1 scenarios are of a world more integrated, and more ecologically friendly. The B1 scenarios are characterized by: Rapid economic growth as in A1, but with rapid changes towards a service and information economy. Population rising to 9 billion in 2050 and then declining as in A1. Reductions in material intensity and the introduction of clean and resource efficient technologies. An emphasis on global solutions to economic, social and environmental stability. B2 The B2 scenarios are of a world more divided, but more ecologically friendly. The B2 scenarios are characterized by: Continuously increasing population, but at a slower rate than in A2. Emphasis on local rather than global solutions to economic, social and environmental stability. Intermediate levels of economic development. Less rapid and more fragmented technological change than in