Exploring climate change mitigation scenarios through Socio-Economic Metabolism models and Simulation Games

Humanity is facing a global climate crisis induced by a growing population, carbonintensive lifestyles, and highly polluting production systems. Solving the climate crisis requires a profound transformation of our socio-economic metabolism (SEM), i.e. the physical system of anthropogenic stocks and flows of materials, energy, and greenhouse gas (GHG) emissions. The transformation of the SEM towards a carbon-neutral system requires climate change mitigation (CCM) measures. The implementation of CCM measures is driven by a constellation of different actors, i.e. the social system. Most research on CCM focuses on studying either the transformation of the physical or the social system. However, the two systems are highly interdependent and connected to each other. Therefore, the solutions need to address both systems. Most existing approaches to integrating the two systems focus on exploring the actors as objects, for example through agents in agent-based models. Such approaches are useful to include different actors' rationale; however, they are limited in (1) including participatory exercises and (2) triggering personal experiences. This limitation can be addressed by considering the actors as acting subjects. In this thesis, we propose the use of SEM-based simulation games (SGs) in order to integrate the two systems and to explore the actors' perspectives through acting subjects. Furthermore, SEM-based SGs allow us to tackle another challenge of CCM research, namely its limited accessibility to wider audiences. Studies on CCM are typically targeted at policy-makers, industry representatives, and researchers, by means of scientific articles, reports, and oral presentations. By using SGs, we can use more playful and interactive means to address target groups such as the general public. In this thesis, we exemplify the link between SGs and SEM models with a case study, the postfossilCities SG, which contains a SEM model of the Swiss economy. The postfossilCities SG was developed in the frame of the Post-Fossil cities project. In SEM models, the physical system is typically modeled through technology- and lifestyle- based parameters. Examples of technology-based parameters are energy intensity, energy carriers, and systems efficiency, whereas lifestyle-based parameters include stocks per capita, user behavior, and intensity of use. Despite the use of these two types of parameters, SEM studies on CCM have largely focused on exploring technology-driven measures, and thus on refining the modeling of such measures through technology-based parameters. This leaves (i) untapped potential for further CCM through lifestyle-driven measures and (ii) unexplored synergies across technological developments and lifestyle changes. In this thesis, we explore and refine the modeling of both types of measures by developing two sectoral SEM models for the Swiss residential building stock and the Swiss passenger car stock. The sectoral models served as the basis for modeling and refining the Swiss economy-wide SEM model used in the postfossilCities SG. The results of the sectoral models show that technology-driven measures are highly effective in lowering emissions and can transform the physical system into a carbonneutral system. In particular, we found that the Swiss residential building sector can reach carbon neutrality in 2050 by (i) an extension of the current buildings program (i.e.lower energy intensity of buildings and increase use of renewable energies) and (ii) a complete replacement of fossil fuel heaters with heat pumps and solar energy by 2050. For the passenger car sector, the results show that carbon-neutrality can be achieved in 2050 through a full and rapid electrification of the car fleet, i.e. phase out sales of gasoline- and diesel-cars by 2025 and hybrid and plug-in hybrid cars by 2030. While technology-driven measures are highly effective at reducing emissions, they are limited in lowering energy consumption, and thus CCM strategies solely based on technology- driven measures can result in missing some of the energy-related goals. For example, in the residential building sector, we found that the 2000-Watt Society target can only be achieved by combining technology- and lifestyle-driven measures, which include (i) lower average indoor temperatures, i.e. from 22°C to 20°C, (ii) a reduction in heated surface areas, and (iii) a reduction in floor area per capita. For passenger cars, the results show that the lowest energy consumption is provided by a combination of technology- and lifestyle-driven measures, which includes a widespread use of ridesharing and autonomous cars (ACs). In contrast, the penetration of ACs without ridesharing is expected to trigger the highest energy consumption in 2050. Consequently, lifestyle-driven measures are highly effective in reducing energy consumption and in preventing an increase in energy demand from emerging technologies, such as ACs. Additionally, the results of the sectoral models indicate that the full mitigation effect of technology-driven measures can be severely delayed by the time it takes to replace the existing (technology) stock, while lifestyle-driven measure have an immediate impact on the entire stock. As a consequence, a longer delay in the implementation of technology-driven measures would require more drastic lifestyle-driven measures based on "old" technologies to reach the climate goals by 2050. Through the development of the postfossilCities SG, we found that SEM-based SGs can be used to integrate physical and social systems in a novel manner. In this integration, the physical system is described through a SEM model and the social system through (1) a role-play, (2) role-strengths models to quantify the success of each role, and (3) other game mechanics. Furthermore, we identified several benefits of linking SEM models and SGs: (1) the communication and understanding of complex systems through experiential and emotional learning, (2) the use of oral, written, non-verbal, and visual communication through activities and processes such as reading, writing, discussing, and doing, which are usually more appealing and intuitive for the general public, and (3) the increased robustness of SGs through mass- and energy-balance consistent representations of physical systems. However, we also found challenges in linking SEM models and SGs: (1) the integration of approaches from different disciplines, (2) the highly resource-intensive nature of the game development process, and (3) the identification of the right balance between simplification and complexity. Some of these challenges can be addressed by considering them early in the planning process of the project. Further research can support the refinement of SEM models and SEM-based SGs. For SEM models, future efforts should focus on refining the link between sectors through material, energy, and GHG emissions flows, which requires a better understanding of the dependencies and dynamics across sectors. An example of such dependencies is observed between stocks (e.g. building stock or car fleet) and material industries, as the stock size and the stock dynamics drive material demand. Therefore, the refinement of the links across sectors will allow for a more comprehensive evaluation of the direct and indirect emissions associated with CCM measures. This refinement can also provide a solid basis for improving the modeling of lifestyle-driven measures, and thus for understanding the (systemic) effects of behavioral change. For the SEM-based SG, further developments can exploit the rapid evolution of the SGs field through the use of new technologies, such as virtual reality, augmented reality, or real location-based features. By doing so, SGs can make the game experience highly engaging and motivating, and increase the outreach of CCM strategies to wide audiences with no prior knowledge of the topic