Hundreds of integrated assessment, energy system, electricity, and other sectoral models have been established in the literature and used in research and innovation projects, for the purposes of underpinning climate and energy policy. This diversity is embedded in the range of scientific disciplines and methodologies involved in their development and use and reflects that no single model can cover the broad spectrum of issues relevant to policy, such as effort sharing under the Paris Agreement principles, synergistic effects across policies corresponding to different sustainability dimensions, quantification of costs associated with realistically covering the gaps between NDCs and Paris targets, interpretation of the potential of negative emissions technologies, etc.
To help policymakers act in the face of such huge possibility sets, a diversified portfolio of modelling tools can help answer questions through targeted sensitivity or stochastic parameter perturbations, to identify robust patterns of mitigation, whilst exploring a genuinely large possibility space. As different types of modelling structure focus on specific sectors or aspects, while often ignoring changes taking place in other sectors or impacts on other aspects thereby offering different types of insights, establishing connections between models that deploy different methodologies and structures in multi-model analyses can produce more robust policy prescriptions. Therefore, effective climate policy must be underpinned by modelling ensembles that altogether provide insights for different geographic scales, cover in detail all economic sectors, represent different types of policies, provide insights for the broad range of GHGs and aerosols, and draw from different methodologies, toward capturing the diversity of climate-economy interactions and uncertainties. In this respect, the IAM COMPACT ensemble comprises 25 highly diverse global and regional integrated assessment models, energy and electricity models, as well as sectoral models, as outlined below and documented in detail in I2AM PARIS. The modelling frameworks to be used in the project’s capacity development activities are denoted with an asterisk.