Marco A. Janssen

Global modeling has been used for decades to assess the possible futures of humanity and the global environment. However, these models do not always satisfactorily include the adaptive characteristics of systems. In this article, a general approach is used to simulate change and transition at a macrolevel due to adaptation at a microlevel. Tools from complex adaptive systems research are used to simulate the microlevel and consequently determine parameter values of the equation-based macrolevel model. Two case studies that applied this approach are reviewed. The first study assessed the efficacy of efforts to control malaria, whereas the second study used an integrated model to construct climate change scenarios by using various possible views on the nature of the climate system.

Key words: complex adaptive systems; global change; climate change; malaria; multiagent modeling; adaptation; coevolution; genetic algorithms.

To evaluate possible futures with regard to economy, energy and climate, a multi-agent modelling approach is used. Agents hold different perspectives on how the world functions (worldview) and how it should be managed (management style) and this is implemented in a simple dynamic model of the economy-energy-climate system. Each perspective is supported by a proportion of the agents, but this proportion changes in response to observations about the real world. In this way the totality of agents learn from their observations. It is concluded that this approach is a good illustration of how adaptive behavior can be included in global change modelling. Some exploratory experiments are done to address the consequences of surprises.

Keywords: Global change; Integrated assessment modeling; Perspectives; Multi-agent modeling.

Workers at the Dutch National Institute of Public Health and the Environment (RIVM) have recently developed a new comput­ er tool called the Interactive Scenario Scanner (ISS). The tool enables users to interactively construct global greenhouse gas emission scenarios and evaluate their likely climate change impacts. In this way, the tool can be used to support a dialogue between scientists and policy makers on scenario development and help in selecting scenarios to be analysed with more sophisticated modelling tools, like RIVM’s IMAGE 2 model.

The safe landing analysis has been devel­ oped to link short-term greenhouse gas emission targets to longer-term climate protection goals. The analysis was applied to the climate policy goals proposed by the European Union. This application and sev­eral presentations of the analysis during the negotiations on the Kyoto Protocol led to critical but constructive discussions. In this paper we discuss some of the key questions such as policy relevance, scien­tific credibility, use and adequacy of global indicators todetermine impact levels, tech­nological feasibility and economic aspects. The results from the safe landing analysis were generally accepted by the policy community because it bridges the gap between policy needs and the under­standing derived from complex but scienti­fically rigorous integrated assessment models.The selected indicators of the safe landing analysis are evaluated. It is shown that the indicators describing rates of change are as important for defining impacts and response policies as those describing only cumulative or absolute change. Lower levels of climatic change generally coincide with lower impact levels. However, only the lowest rates and levels of climate change allow natural eco­systems to adapt. It is further shown that the level of additional energy expenditures needed to meet such low impact levels strongly depends on the assumed techno­logical development rates.