Energy system modeling is central to informing the transition to low-carbon energy systems in the United States. Integrated Assessment Models (IAMs) are standard for such large-scale, intersectoral modeling of energy policy interventions, illustrating the various links between climate change, energy system technology development, and economic and social factors. While such models provide the most robust option for understanding the relationship of coupled climate-energy-social systems, they still include many simplified and idealized representations of how the energy system evolves over time. They often do not reflect the real-world political and policy landscape and tend to omit complicating factors like coalition building, policy revision, and incomplete policy implementation. This grant will support work by a multidisciplinary team led by Wei Peng of the Pennsylvania State University to make IAMs more representative of real-world conditions. The team will focus on improving the widely used Global Change Analysis Model (GCAM), specifically the downscaled version of GCAM that is centered on the United States, GCAM-USA. The team will devise an iterative process for updating GCAM-USA, and IAMs more generally, with concepts and insights from political economy and the social sciences. The project will start this process by undertaking two modeling demonstration projects. The first will attempt to better represent different domestic sectoral energy policy instruments in GCAM-USA. This includes modeling a more realistic set of sectoral-based regulations and policy incentives that are currently, or have a potential to be, put in place. The second demonstration project will focus on representing aspects of energy policies that are related to global supply chains, focusing initially on the impacts of policy change with respect to the global trade environment, such as domestic manufacturing incentives or the introduction of trade barriers.