A framework to assess highest possible ambition in nationally determined contributions under Article 4 of the Paris Agreement
File(s)
Published version
Author(s)
Schönfeld, Julia Katharina
Rogelj, Joeri
Type
Journal Article
Abstract
Collective progress towards meeting the Paris Agreement’s long-term temperature goal (LTTG) remains insufficient, a shortfall to be addressed by new Nationally Determined Contributions (NDCs). The Agreement stipulates that countries’ NDCs will represent a progression and reflect their highest possible ambition (HPA). However, the vague conceptualisation of this HPA norm challenges its translation into practice, allowing states to reference ambition in their NDC without clear evidence. Recently, the International Court of Justice’s (ICJ) advisory opinion on climate change provided clarification regarding this norm. The level of ambition communicated in an NDC is not entirely left to the discretion of states but must constitute an adequate contribution to the collective achievement of the global temperature goal. States are obliged to exercise due diligence to ensure their NDCs reflect their best efforts. Building on the ICJ’s interpretative guidance, we propose a structured framework to operationalise the HPA norm and reflect upon considerations of ambition in countries’ NDCs. The framework’s core pillars incorporate domestic, international, and implementation considerations in NDCs, elaborated upon in two elements per pillar. Under domestic considerations, NDCs should be based on a faithful assessment of mitigation options utilising national capabilities. International considerations require contributions that adequately support the LTTG while balancing equity. Implementation considerations demand that NDCs account for the co-impact of the measures considered and be actionable in the near term to ensure ambition is translated into action. The Paris Agreement-HPA Framework can support transparent communication of the conditions under which more ambitious targets can be pursued. We apply the framework to explore the engagement of current NDCs with the framework’s elements. Finally, the framework empowers societal stakeholders to interrogate, verify and, when necessary, challenge whether NDC preparations were carried out with due diligence, supporting accountability in global and national climate action.
Date Issued
2025-11-01
Date Acceptance
2025-10-21
Citation
Environmental Research Letters, 2025, 20 (11)
ISSN
1748-9326
Publisher
IOP Publishing
Start Page
114081
End Page
114081
Journal / Book Title
Environmental Research Letters
Volume
20
Issue
11
Copyright Statement
© 2025 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
License URL
Publication Status
Published
Article Number
114081
Date Publish Online
2025-11-06