Entry points for assessing 'fair shares' in national mitigation contributions
'Entry points' for clear and transparent fairness claims in national mitigation contributions
Read the published paper ↗doi.org/10.1088/1748-9326/ada45f
Making fairness claims legible in NDCs
Fairness has long been central to the climate mitigation discourse. Decisions under the Paris Agreement, recalled in the first Global Stocktake, mandate that nationally determined contributions (NDCs) include clear and transparent fairness considerations. Yet practical guidance for doing so is lacking.
Illustrative examples from current NDCs show the consequence. Some fairness assertions invoke principles without saying how they are interpreted or applied. Others describe the quantity being allocated so ambiguously that the underlying temperature target and its likelihood cannot be inferred. An ambiguous assertion can also allow several plausible indicators, each leading to substantively different allocations. We examine the entry points along the path by which a party develops and communicates a normative stance on fairness in domestic mitigation effort. We ask what has to be made explicit for a quantitative 'fair share' claim to be assessed by anyone other than its author.
Four decision stages applied to the EU27
We propose a set of 'entry points', the key decision stages in quantifying a 'fair share'. The first is the foundational principles and their interpretation. The second is the allocation quantity, meaning the object to be allocated and whether it is fixed over a period or considered annually. The third is the allocation approach used to distribute that quantity. The fourth is the indicators, the measurable data used to operationalise the approach. Alongside these, we recognise the importance of communicating what one party's assertion implies for all other parties.
We demonstrate the approach through a case study of the European Union (EU27). We selected it in light of a contemporaneous science-policy process in the region that has considered relative 'fair shares' in informing climate targets. The illustrative quantification draws on polluter pays, do no harm and precaution from the EU Climate Law, together with common but differentiated responsibilities and respective capabilities under the Paris Agreement. It applies two allocation approaches: equal cumulative per capita allocation from 1990, and the same rule scaled in inverse proportion to cumulative per capita GDP.
Both approaches return a negative remainder
The allocation quantity starts from a remaining carbon budget of 247 GtCO2 from 2023, consistent with limiting warming to 1.5 °C at 50% likelihood. We add global CO2 emissions from 2020 to 2022 (117 GtCO2) and subtract projected median international bunker emissions (46 GtCO2). We then add CO2 emissions from fossil fuels and industry (CO2-FFI) from 1990 to 2019 (852 GtCO2-FFI) to define a total budget from 1990.
Under equal cumulative per capita allocation from 1990, the EU27 is allocated 77.5 GtCO2-FFI in 1990, leaving a remaining allocation of −35.7 GtCO2-FFI as of 2023. Adjusted for capability, the 1990 allocation falls to 27.1 GtCO2-FFI and the 2023 remainder to −86.1 GtCO2-FFI. In our case study, the remaining allocation is negative as of 2023 under both approaches considered.
Naming the judgement makes it assessable
Each stage encodes a value judgement that is usually left implicit, and naming the stages makes those judgements visible and open to critique. The central theme of this work is transparently communicating the foundational principles considered, their interpretation, and their practical application in quantitative assessments of fairness.
A negative remaining allocation does not close the question. By upholding a fixed climate target and following principles considered foundational, parties can motivate the pursuit of the highest possible domestic ambition. They can also transparently communicate and address any resulting breach of 'fair shares' through negative emissions targets and international cooperation, in line with global climate goals. The entry points are a step towards bridging scholarly fairness debates and the practical work of preparing national contributions. They recognise responsibility for past inaction under a rapidly approaching overshoot trajectory.
@article{pelz_entry_2025,
title = {Entry points for assessing ‘fair shares’ in national mitigation contributions},
volume = {20},
copyright = {All rights reserved},
issn = {1748-9326},
url = {https://iopscience.iop.org/article/10.1088/1748-9326/ada45f},
doi = {10.1088/1748-9326/ada45f},
abstract = {Abstract
Fairness considerations have long been central to the international climate change mitigation discourse, generating numerous scientific and philosophical debates. Yet, there remains a pressing need for practical guidance on developing assertions of fairness in national mitigation contributions. The Paris Agreement mandates that subsequent nationally determined contributions (NDCs) submitted under Article 4 represent a progression compared to previous NDCs. Further decisions under the Paris Agreement mandate that NDCs include clear and transparent considerations of fairness, as recalled in the first Global Stocktake. We propose a practical approach to this, comprising a set of ‘entry points’ that represent key stages where decisions are taken in ‘fair share’ quantifications, from interpreting foundational principles to selecting indicators and presenting results. By bridging the gap between scholarly debates and practical application, this work supports the integration of clear and transparent fairness considerations into climate policy commitments. We demonstrate the use of our approach through a case study.},
number = {2},
urldate = {2025-01-20},
journal = {Environmental Research Letters},
author = {Pelz, Setu and Ganti, Gaurav and Pachauri, Shonali and Rogelj, Joeri and Riahi, Keywan},
month = feb,
year = {2025},
pages = {024012},
}