The Atmosphere and Climate Modeling - Introduction to Carbon Capture and Sequestration - page 85

Box 2.5.1 Emission scenarios
To predict what the climate will look like in, say, 100 years, we have to make assump-
tions about future CO 2 emissions. These emissions are closely related to future energy
use and possible changes in the use of fossil fuels. Future energy use (and sources of
energy) is diffi cult to predict, so climate scientists adopt various scenarios to make
climate predictions. The scenarios typically include a “business as usual scenario”
where we assume that we continue to use energy exactly the same way as in the past.
In a similar way, we can assume a scenario in which emissions are capped at some
level that might be the result of an international treaty. The IPCC has developed a set
of scenarios in their Special Report on Emissions Scenarios. These scenarios are
referred to as the “SRES.” The IPCC uses four different story lines of how the world
might evolve:
A1 (an integrated world) is a scenario with rapid economic growth and a global popu-
lation that reaches 9 billion in 2050, then gradually declines. In this world there is a
quick spread of new and effi cient technologies, and income and way of life converge
between the different regions. Extensive social and cultural interactions are manifest
worldwide. Within A1 there are three subset scenarios, each differing in their use of
fossil fuels:
A1FI: emphasis on fossil fuels.
A1B: a balanced emphasis on all energy sources.
A1T: emphasis on non-fossil energy sources.
A2 (a heterogeneous world) is a scenario where nations are self-reliant and operate
independently. The population continues to increase and economic developments are
regional. Technological changes are slow and fragmented.
B1 (an integrated ecologically friendly world) is a scenario where the world sees the
same rapid economic growth as in A1: the population will increase to 9 billion, and as
in A1, it will decrease afterwards. Technological advances reduce the use of materials
and result in the introduction of clean and resource-effi cient technologies. The world
adopts global solutions to ensure economic, social and environmental stability. This
scenario does not include economic incentives to mitigate climate change.
B2 (a more divided but ecologically friendly world) is a scenario wherein the world
shows intermediate economic growth and seeks local solutions to economic, social,
and environmental problems. The population is continuously increasing, but at a
slower rate than in A2.
The fi gure shows the global greenhouse gas emissions predicted in each of these
scenarios.
( Continued )