Environmental Engineering Reference
In-Depth Information
the approaches, emphasising that scenarios were not predictions, simply a perception of likely
futures, articulating this as 'the gentle art of reperceiving'. Porter (1985) also used scenarios
to examine external uncertainties and forces on markets as a backdrop to planning. Scenario
analysis has since become extremely popular, with much use in government in policy-making
and also in business management for forward planning and strategy development (Schwartz,
1996; Frommelt, 2008), and many countries have carried out 'foresight programmes' that use
scenarios.
Van Notten et al. (2003) develop a typology of the varied approaches used in scenario
analysis, covering the following variables:
•
Norms and values: descriptive (explore possible futures) or normative scenarios (probable
or preferable futures);
•
Vantage point: forecasting, anticipatory (exploratory) and backcasting (steps from a
desirable future);
•
Subject: issue, area or institution-based;
•
Timescale: short (3-10 years) and long-term perspective (25+ years);
•
Spatial scale: global, supranational, national, city, local;
•
Nature of data: qualitative (often narrative) or quantitative, or hybrid;
•
Temporal nature: developmental trajectory or end-state 'snapshot';
•
Nature of variables: heterogeneous (wide variety) or homogeneous (limited);
•
Nature of dynamics: trend scenarios (extrapolating existing trends) or peripheral scenarios
(include unlikely and extreme events);
•
Levels of deviation: business as usual (BAU) scenarios represent the status quo and
alternative scenarios differ significantly from one another - to challenge assumptions and
raise discussion about potential and emerging issues.
The classic starting point for many scenario studies is to identify 'predetermined' and
'undetermined' elements. The predetermined elements are the same in each scenario (sometimes
called the external elements), and the undetermined elements are elaborated in several ways
(sometimes called the internal elements), dependent on possible future developments, and thus
result in different future images (Van der Heijden, 1996). Frommelt (2008) outlines the
different potential elements of the scenario generation process, including the different starting
points, methods, approaches and modes of development (
Figure 2.12
)
.
There are, therefore, a number of potential distinctions in the approaches that can be used.
The explorative scenarios start from the present and move towards an end state, whilst the
anticipative scenarios (sometimes also known as normative scenarios) start with a set of
characteristics or images in the future and work backwards to see what it would take to get
there. These are then assessed as to whether they are plausible. There is a similarity between
this approach and the backcasting approaches (see later discussion).
Inductive methods derive scenarios based on experience or experiential building blocks,
moving from the particular to the more general. Hence observations are used to develop general
principles. The deductive method operates in reverse, reasoning from the general to the specific.
A framework or general image may be added to with specific data. The incremental method
uses an 'official future' as the starting point, and uncertainties or flaws within this can be
identified and critiqued. Schwartz and Ogilvy (1998) see the official future as 'the scenario
that the decision-makers really believe will occur' and 'usually an unsurprising and relatively
non-threatening scenario, featuring no discontinuities, changes to current trends, no crises and
continued stable growth'. The degree to which these approaches produce similar or different
