About Emission Scenarios

Also called Global Futures Scenarios, emission scenarios can be thought of as stories of possible futures. They allow the description of factors that are difficult to quantify, such as governance, social structures, and institutions.

In 1996, the Intergovernmental Panel on Climate Change (IPCC) opted to develop a new set of emission scenarios, which was published in the document Special Report on Emissions Scenarios (SRES) in 2000 and used as the basis for the IPCC Third Assessment Report (2001) and the IPCC Fourth Assessment Report (2007).

The scenarios are organized into families based on the emphasis on regionalization (A2, B2 storylines) versus globalization (A1, B1 storylines) and environmental sustainability (B1, B2 storylines) versus economic development (A1, A2 storylines).

Below are emission scenarios used in data found in the Climate Commons.

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List of Emissions Scenarios used in the Commons

Scenario Description

A convergent world with the same global population as in the A1 storyline but with rapid changes in economic structures toward a service and information economy, with reductions in materials 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.


A very heterogeneous world with continuously increasing global population and regionally oriented economic growth that is more fragmented and slower than in other storylines. Fertility patterns across regions converge very slowly, which results in high population growth. Economic development is primarily regionally oriented and per capita economic growth and technological change are more fragmented and slower than in other storylines.


A future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and rapid introduction of new and more efficient technologies, with the development balanced across energy sources. 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 A1B subset to the A1 family of scenarios has a balanced emphasis on all energy sources.