Entry points for assessing 'fair shares' in national mitigation contributions
'Entry points' for embedding clear, transparent fairness into national mitigation contributions
Making fairness claims legible in NDCs
Fairness has long been central to the climate mitigation discourse, and both the Paris Agreement and the first Global Stocktake mandate that successive nationally determined contributions communicate fairness considerations clearly and transparently. Practical guidance for doing so is lacking.
The consequence is visible in submitted contributions, where fairness assertions frequently rest on a single indicator presented without the reasoning that selected it, or invoke principles whose interpretation is never stated. A party can appear to have justified its ambition while leaving every consequential judgement implicit. We examine the entry points along the path by which a party develops and communicates a normative stance on fairness in domestic mitigation effort, asking what has to be made explicit for a quantitative 'fair share' claim to be assessable by anyone other than its author. Without that, a fairness assertion cannot be compared across parties, and the transparency the Paris Agreement requires is not delivered.
Four decision stages, then an EU27 case
We propose a set of 'entry points', the key decision stages in quantifying a 'fair share'. These run from the foundational principles and their interpretation, through the allocation quantity, meaning the object to be allocated and whether it is fixed over a period or considered annually, to the allocation approach used to distribute that quantity, and finally to the indicators, the measurable data used to operationalise the approach. Alongside these we recognise the importance of communicating the implications of a specific assertion by one party for all other parties.
We demonstrate the approach through a case study of the European Union, selected in light of a contemporaneous science-policy process in the region that has considered the implications of relative 'fair shares' in informing climate targets. The illustrative quantification draws its principles from the EU Climate Law, namely polluter pays, do no harm, and precaution, together with common but differentiated responsibilities and respective capabilities under the Paris Agreement, and applies two allocation approaches: equal cumulative per capita allocation from 1990, and the same rule scaled in inverse proportion to cumulative per capita GDP.
Every approach returns a negative remainder
The allocation quantity is built from a remaining carbon budget of 247 GtCO2 from 2023 consistent with limiting warming to 1.5C at 50% likelihood, to which we add global CO2 emissions from 2020 to 2022 of 117 GtCO2, from which we subtract projected median international bunker emissions of 46 GtCO2, and to which we add CO2-FFI emissions from 1990 to 2019 inclusive of 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. Under the same rule adjusted for capability, the 1990 allocation falls to 27.1 GtCO2-FFI and the 2023 remainder to -86.1 GtCO2-FFI. The outcomes show remaining allocations in our case study that are negative as of 2023, and that result holds 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 is what makes those judgements visible and contestable. The central theme in this work is the importance of transparently communicating the foundational principles considered, their interpretation, and their practical application in quantitative assessments of fairness in national mitigation contributions.
A negative remaining allocation does not close the question, and we argue it should not be read as an argument for abandoning the target. By upholding a fixed climate target and following principles that are considered foundational, parties can motivate the pursuit of highest possible domestic ambition while transparently communicating and addressing 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, in a form that recognises 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},
}