A principle-based framework to determine countries' fair warming contributions to the Paris Agreement
We allocate an all-greenhouse-gas warming budget to countries using principles from international treaties and law
Read the published paper ↗doi.org/10.1038/s41467-025-56397-6
We find that by 2021, between 84 and 90 countries, including but not limited to all major developed countries, had exhausted their share of a budget compatible with keeping warming to 1.5 °C (50% likelihood). This holds under every allocation approach we consider, and a similar picture emerges for 2 °C (67% likelihood).
Most effort-sharing work allocates CO2 alone, leaving a gap for non-CO2 gases such as methane and their warming contributions. We address this by defining a global warming budget that covers all anthropogenic greenhouse gases, expressed in CO2 warming-equivalent emissions. We allocate it to countries using equity principles drawn from international treaties and environmental law.
As a result, a large group of countries will exceed their 'fair share' even if their Paris Agreement pledges represent their deepest possible emissions reductions. Considerations of fairness should therefore start exploring aspects beyond domestic emissions reductions.
@article{li_principle-based_2025,
title = {A principle-based framework to determine countries’ fair warming contributions to the {Paris} {Agreement}},
volume = {16},
copyright = {All rights reserved},
issn = {2041-1723},
url = {https://www.nature.com/articles/s41467-025-56397-6},
doi = {10.1038/s41467-025-56397-6},
abstract = {Abstract
Equity is a cornerstone of global climate policy, yet differing perspectives mean that international agreement on how to allocate mitigation efforts remains elusive. A rich literature informs this question, but a gap remains in approaches that appropriately consider non-CO
2
emissions and their warming contributions. In this study, we address this gap and define a global warming budget applicable to all anthropogenic greenhouse gases that is allocated to countries based on principles drawn from international treaties and environmental law. We find that by 2021 a range of 84 to 90 countries, including but not limited to all major developed countries, exhausted their budget share compatible with keeping warming to 1.5 °C (with 50\% likelihood) under all allocation approaches considered in this study. A similar picture emerges for limiting warming to 2 °C (with 67\% likelihood). A large group of countries will hence exceed their fair shares even if their pledges under the Paris Agreement represent their deepest possible emission reductions. Considerations of fairness should therefore start exploring aspects beyond domestic emissions reductions.},
language = {en},
number = {1},
urldate = {2025-01-30},
journal = {Nature Communications},
author = {Li, Mingyu and Pelz, Setu and Lamboll, Robin and Wang, Can and Rogelj, Joeri},
month = jan,
year = {2025},
pages = {1043},
}