Page 54 - Module_6_en

Module 1. Determine the approach to be used for quantification (e.g., which tools and models to use, how
6 2. Assemble the necessary data and relationships.
these will be linked to each other, and how these will be informed by/inform the narratives).

3. Use the tools and models to produce the quantitative estimates.

9-12 December, 2013 Comments

For quantification, it is best to use models that are as simple as possible without being simplistic, are
transparent, rely on widely available data, and can be applied and compared across widely differing
circumstances. Quantification ideally will provide much more policy-relevant information than qualitative

descriptions alone. It can provide a measure of the magnitude of the challenge and the scale of the
needed policy response.

Models that can be used interactively are advantageous because they can be used in working sessions

to provide quantification, leading to a revision of the narrative and a next round of quantification. In any
case, iterations between storylines and models are an important part of a scenario process including
quantification.

The selection of models to be used in the quantification depends on the issues emphasized in the
scenarios. For GEO-3, for example, initial quantification for two of the scenarios was done using the
PoleStar software tool (Raskin and others 2002). While PoleStar offers a flexible and easy-to-use
accounting framework for organizing economic, resource and environmental information for alternative
scenarios, the scenario authors agreed that the analysis needed to be complemented by further
information on environmental impacts. This could only be provided by other, more spatially explicit and

process-oriented modelling tools. Therefore other models (i.e., IMAGE from RIVM, WaterGAP from
CSER, AIM from NIES) were introduced to make the data more consistent across regions and with
the narratives, and to harmonize input data (e.g., growth rates of GDP per capita). Bakkes and others
(2004) show how the quantification of the GEO-3 scenarios was carried out and describe the tools

that were used. This is also in line with what was done in the Millennium Ecosystem Assessment and
has been done in GEO-4.

The Africa Environment Outlook (UNEP 2006) used two tools to provide quantification of their

scenario narratives: the Polestar software tool developed by the Stockholm Environment Institute
(www.sei.se); and T21, a tool for integrated, comprehensive development and policy planning developed
by the Millennium Institute (see http://www.threshold21.com/collaborative.html). In the latter case, the
existing T21-Malawi Model was customized to enhance its environmental modelling capability for the
production of the case study.

52 Scenario Development and Analysis