Keynote Presentations from the 2nd AVEC International Summer School, Peyresq, 18-30 September 2005

Speaker: Timothy Carter
Finnish Environment Institute (SYKE), PO Box 140, FIN-00251 Helsinki, Finland

Title of the talk: Global change scenarios (pdf: 3MB)

Summary of the talk by Diana Meyer-Veden: Students´ summary (pdf)


Scenarios of global change

The past centuries have witnessed a rapid increase in human population as a result of economic development and the successful exploitation of natural resources. Human activities have affected the environment through pollution and degradation of the basic "commons": air, water and soil. This has led to environmental problems such as acid rain, climate change, stratospheric ozone depletion and soil erosion. These changes are termed "global changes", because they affect all areas of the globe and because they touch upon all aspects of the relationship between human development and environmental change.

Europe has also experienced widespread global changes, a large portion of which are anthropogenic in origin. In order to anticipate global changes during the coming decades, and to prepare for their likely impacts on ecosystems and society, it is necessary to project current trends into the future. However, there are large uncertainties associated with estimates of human influence on complex natural systems, and it is impossible to predict the future with any confidence. Instead, it is customary to construct "scenarios". A scenario can be defined as "a coherent, internally consistent and plausible description of a possible future state of the world" (IPCC, 1994).

This lecture will introduce students to the concept of scenarios, contrasting descriptive and normative scenarios, emphasising the role of the base case scenario, and illustrating alternative approaches to scenario development:

Global change scenarios are often selected to shed light on key uncertainties in projections, though some studies may adopt other selection criteria (e.g. choosing the "best estimate" or "worst case" scenario). Scenarios can cover a wide range of issues, including:

Examples of each of these scenario types will be presented and students will be encouraged to participate in a scenario building exercise of their own as part of the group work following the lecture.


A questionnaire has been handed out to the participants and the results were shown and discussed already in Peyresq.

Recommended background literature on this presentation:

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