The Scenario Narrative
A scenario modeler usually starts with a narrative, a basic story of the future. In a formal
scenario exercise, these come from a narrative team. But stories of the future are all around us,
and it is interesting to put numbers to them to see what they imply. For this tutorial, an official story
of carbon emissions in the U.S. will be used as a narrative.
In early 2002, President Bush of the United States put forward a goal for mitigating the country’s greenhouse gas emissions.
The goal is to decrease the emission intensity (emissions per dollar GDP) by 18 percent over the following 10 years.
It is reasonable to ask whether the target of an 18 percent decline
in emission intensity, if it is met, is likely to raise or lower total emissions. After all,
it is total emissions that makes the difference in driving climate change. So, the question to be addressed in the
scenario is this:
Given different assumptions for population and GDP per capita over the next 10 years, what does the president's target imply for emissions?
