Integrated assessment models (IAMs) have emerged as key tools for building and assessing long term climate mitigation scenarios. Due to their central role in the recent IPCC assessments, and international climate policy analyses more generally, and the high uncertainties related to future projections, IAMs have been critically assessed by scholars from different fields receiving various critiques ranging from adequacy of their methods to how their results are used and communicated. Although IAMs are conceptually diverse and evolved in very different directions, they tend to be criticised under the umbrella of ‘IAMs’. Here we first briefly summarise the IAM landscape and how models differ from each other. We then proceed to discuss six prominent critiques emerging from the recent literature, reflect and respond to them in the light of IAM diversity and ongoing work and suggest ways forward. The six critiques relate to (a) representation of heterogeneous actors in the models, (b) modelling of technology diffusion and dynamics, (c) representation of capital markets, (d) energy-economy feedbacks, (e) policy scenarios, and (f) interpretation and use of model results.

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When modeling medium and long-term challenges we need a reference path of economic development (the so-called baseline). Because sectoral models often offer a more fundamental understanding of future developments for specific sectors, many CGE modeling teams have adopted approaches for linking their models to sectoral models to generate baselines. Linked models include agricultural sector, energy sector, biophysical and macroeconomic models. We systematically compare and discuss approaches of linking CGE models to sectoral models for the baseline calibration procedure and discuss challenges and best practices. We identify different types of linking approaches which we divide into a) one-way, and b) twoway linking. These two types of linking approaches are then analyzed with respect to the degree of consistency of the linkage, information exchanged, as well as compromises in aggregations and definitions. Based on our assessment, we discuss challenges and conclude with suggestions for best practices and research recommendations.