fair-shares library

2026

A Python library that turns fair-share carbon budget allocation into transparent, reusable code

We operationalise 'fair shares' of remaining carbon budgets and emission pathways in an open-source Python library, developed with five collaborators. It computes budget and pathway allocations under equal-per-capita, capability-adjusted, and responsibility-weighted approaches, with equity principles, allocation years, and budget sources all configurable. Although allocation between countries is the central use case, the allocation mathematics is general: the same machinery applies to any set of parties for which emissions, population, and capability data can be supplied.

Building on the 'entry points' argument, we treat each equity assumption as a setting a user selects, not a default the code hides. Worked templates cover budget and pathway allocation from user-supplied inputs, and a dedicated template ingests IAMC-format reporting data, so allocations attach directly to scenario ensembles such as the AR6 database. Swapping a principle or a start year changes the allocation transparently, and the contested values remain visible in the output.

The library also reproduces published allocation studies as executable notebooks, including the 2023 equity evaluation for the European Scientific Advisory Board on Climate Change, which can be updated as input data are revised, alongside reproductions of other published approaches. It underpins the quantitative analysis in several of our climate-equity papers, giving those results a single auditable engine, and is public at github.com/setupelz/fair-shares.

@software{pelz_fairshares_2025,
	title = {fair-shares: {Python} package for calculating fair shares of remaining carbon budgets and emission pathways},
	author = {Pelz, Setu and Holz, Ceecee and Lamboll, Robin and Weber, Konstantin and Lewis, Jared and Nicholls, Zebedee},
	year = {2025},
	version = {0.2.0},
	license = {BSD-3-Clause},
	url = {https://github.com/setupelz/fair-shares},
}