Changelog

All notable changes to CNit will be documented here.

The format follows Keep a Changelog, and this project adheres to Semantic Versioning.

Version 2.1.0 (2026-01-01)

Initial public release of CNit as a Python package with enhanced code and full documentation.

Previous Versions

The source code for earlier versions of CNit is available from previous Zenodo releases:

  • Tang, G., Nicholls, Z., Norton, A., Zaehle, S., & Meinshausen, M. (2024). Model Source Code for “Coupled Carbon-Nitrogen Cycle in MAGICC: Model Description and Calibration”. Zenodo. https://doi.org/10.5281/zenodo.12204421

  • Tang, G., Zaehle, S., Nicholls, Z., Norton, A., Ziehn, T., & Meinshausen, M. (2025). Model Source Code for the MAGICC Coupled Carbon–Nitrogen Cycle Model – CNit. Zenodo. https://doi.org/10.5281/zenodo.15569386

Added

  • Python package structure with pip/conda installation and dependency management

  • Unit handling with Pint integration for robust physical quantities

  • Comprehensive Sphinx documentation with scientific background and API reference

  • Quick start guide and complete example notebook with code, outputs, and visualizations

Model Features

  • Coupled carbon-nitrogen cycle for terrestrial ecosystems

  • Four nitrogen pools (plant, litter, soil, mineral) and three carbon pools

  • CO₂ fertilization, temperature sensitivity, and land use change effects

  • Nitrogen limitation on carbon uptake

  • Annual timestep with sub-annual process representation

  • Separation of deforestation/afforestation for land use emissions

  • Computationally efficient for integrated assessment modeling

  • MAGICC integration ready

See the CNit Model Overview for detailed model description.

Upcoming

Future versions may include:

  • Enhanced representation of nitrogen deposition

  • Additional nitrogen input pathways

  • Improved parameterization options

  • Additional example notebooks and use cases

  • Performance optimizations

  • Extended calibration examples

Note

Version numbering follows Semantic Versioning (MAJOR.MINOR.PATCH):

  • MAJOR: Incompatible API changes

  • MINOR: New features, backward-compatible

  • PATCH: Bug fixes, backward-compatible