Introduction The ambition to achieve the Paris Agreement goals has led to the realization that a rapid and full decarbonization of the economy is required, involving a structural transition of the current economy and society. With the rise of quantified policy targets, policy packages, and consideration of multiple dimensions and sectors, Integrated Assessment Models with their ability to consider complex relationships and provide calibrated numerical results have become ever more important in the last decade. The PRISMA project aims to bring these models to the next level by focusing on four key areas of improvement, namely the representation of distributional justice and efficiency, innovation and finance, climate impacts and land-use implications, and lifestyle change and circularity. In these four key areas we will improve existing large-scale IAMs and sectorial models, and consider the linking of different models where applicable. Two cross-cutting shared themes across these areas are the improvement of the temporal and spatial resolution of the analysis, and the representation of disruptive and structural change in the economy. Notably we will increase the spatial granularity with a focus on Europe, and look at the yearly and in particular near term detailed modeling of rapid decarbonization pathways. The extensive model development will be co-designed through an interactive stakeholder engagement process from the beginning, and focus on model openness and usability to ensure the stakeholder and policy relevance. Moreover, PRISMA will focus in its application on the analysis of the spectrum of Fit for 55 package policies of the EU developing focalized

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