If you're looking to run or modify a DICE/RICE model, Python and GAMS are the most recommended options depending on whether you prefer open-source tools or industry-standard optimization platforms.
DICE and RICE were originally coded in GAMS, which is designed for solving large-scale optimization problems. GAMS handles nonlinear dynamic optimization well and has a large user base in economics.
Although this requires a commercial license.
Python is a popular choice for open-source versions. Projects like pyDICE implement DICE logic in Python (e.g., using SciPy for optimization). This is free and easier to integrate with data analysis and visualization libraries.
Depending on your specific goals I also like R, although R is much less common in the dev community, it is a great choice for statistical and visual capabilities,
Other choices I'm told (but know nothing about) are Julia, Excel (with VBA) and MATLAB.