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Figure A1. Schematic Illustration of SRES Scenarios
Source: IPCC, 2000, modified.
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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 changes 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 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 global population continuously increasing at a rate lower than that of A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. Though the scenario is also oriented toward environmental protection and social equity, it focuses on local and regional levels.
The overview in Table A1 summarizes the likely temperature changes under each of the scenarios described. It shows that B2 would lead to a temperature change of approximately 2.4°C toward the end of the century, under A1B the temperature change is estimated to be 2.8°C, while A2 is more extreme with a 3.4°C projected change. It is important to note that the projected surface temperature changes toward the end of the 21st century exhibit a broad range of likely estimates, as shown by the bars next to the right panel of Figure A2.