Goals and use

Typical objectives of scenario analysis in environmental assessment are (Alcamo, 2001):

  • Providing a picture of future alternative states of the environment in the absence of additional environmental policies (baseline scenarios).
  • Illustrating how alternative policy pathways can achieve an environmental target
  • Identifying the robustness of environmental policies under different future conditions
  • Raise awareness about different (future) environmental problems and the connection between them
  • Help stakeholders, policymakers and experts to take into account the large time and space scales of a problem
  • Combine qualitative and quantitative information about the future evaluation of an environmental problem

Alternative baseline scenarios can be used to evaluate the consequences of current policies taking into account uncertainties in driving forces, such as economic and socio-cultural developments. Also alternative baseline scenarios can be used to take into account uncertainties about environmental processes occurring in nature and about impacts of environmental conditions on human health. In the same way policy scenarios can be used to evaluate environmental and economic impacts of environmental policies or other policies taking into account uncertainties in e.g. societal driving forces and environmental processes.

Exploratory scenarios can be used when the objective is to explore the consequences of a specified future trend in driving forces, or the consequences of implementing a policy. Anticipatory scenarios can be used when the objective is to investigate the steps leading to a specified end state, such as an environmental target.

Qualitative scenarios analysis can be used when the objective is to stimulate brainstorming about an issue, when many views about the future have to be included or when an idea has to be formed about for example general social and cultural trends. Quantitative scenario analysis can be used for assessments that require data and numbers, for example on the magnitude of air pollutant emissions.

Combinations are also possible, e.g. the "Story-and-Simulation" (SAS) approach, which combines the development of qualitative "storylines" by a group of stakeholders and experts and the use of models to quantify the storylines (Alcamo, 2001).

The principal elements of typical scenarios used in environmental studies are (adapted from Jansen Schoonhoven and Roschar, 1992 and Alcamo 2001):

  • Description of the present situation
  • Several alternative views on future developments, e.g. by means of story lines
  • Description of step-wise changes in the future state of society and the environment i.e. trajectories consisting of logical sequences of events that correspond with and are consistent with each view on future developments.
  • Driving forces influencing the step-wise changes
  • Base year
  • Time horizon and time steps

The main methods for in developing scenarios are:

    • Scenario writing (qualitative scenarios): policy exercises
    • Modeling analysis (quantitative scenarios)

The University of Kassel developed a method to combine both qualitative and quantitative approaches: the SAS is approach as mentioned above. (Alcamo, 2001)

The SAS approach includes the following steps:

  1. The scenario team and scenario panel are established
  2. The scenario team proposes goals and outline of scenarios
  3. The scenario panel revises goals and outline of the scenarios, and constructs zero order draft of storylines
  4. Based on the draft story line the scenario team quantifies the driving forces of the scenarios
  5. Based on the assigned driving forces , the modelling teams quantify the indicators of the scenarios
  6. At the next meeting of the scenario panel , the modelling team report5s on the quantification of the scenarios and the panel revises the storylines
  7. Steps 4,5 and 6 are repeated until an acceptable draft of storylines and quantification is achieved.
  8. The scenario team and panel revise the scenarios based on results of the general review
  9. The final scenarios are published ad distributed.