MESSAGEix is a versatile, dynamic, model framework for energy-engineering-economy-environment (E4) systems research. MESSAGE (without "…ix") is a specific formulation of a generic linear programming (LP) optimization model for strategic energy planning and integrated assessment of E4 systems, developed by the IIASA Energy, Climate, and Environment (ECE) Program since the 1980s. To incorporate feedback between prices and demand levels for energy and commodities, the LP model can optionally be linked to the economic general equilibrium (GE) MACRO model. The message_ix Python package—also fully usable from R—includes: Implementations of MESSAGE, MACRO, and their linkage, in GAMS, Application programming interfaces (APIs) and tools for model building and scientific programming, Extensive documentation and a complete test suite. The framework is built on IIASA's ix modeling platform (ixmp), which provides data warehouse features for high-powered numerical scenario analysis.

Thank you for using the MESSAGEix framework! Please cite the GitHub repository and the MESSAGEix framework manuscript (https://doi.org/10.1016/j.envsoft.2018.11.012).