Assessing processes and evidence for highest possible ambition in Nationally Determined Contributions under the Paris Agreement
- 1Grantham Institute for Climate Change and the Environment, Imperial College London
- 2Centre for Environmental Policy, Imperial College London
- 3International Institute for Applied Systems Analysis
Abstract
The Paris Agreement establishes that Parties’ Nationally Determined Contributions (NDCs) will represent a progression, a country’s highest possible ambition (HPA), and an equitable contribution to the collective long-term temperature goal. However, the agreement provides no guidance on how the HPA standard should be interpreted, assessed, or operationalised in practice. In response to this gap, initial scholarship has proposed frameworks to interpret HPA based on the treaty’s text and the wider international environmental law context, which includes the 2025 Advisory Opinion on Obligations of States in Respect of Climate Change from the International Court of Justice. Altogether, this has clarified how HPA is part of states’ due diligence obligations and sets the stage for the next challenge: how can the theoretical understanding of HPA be practically applied to assess whether NDCs reflect this norm? Here, we build on existing reporting obligations under the United Nations Framework Convention on Climate Change (UNFCCC), emerging approaches reflected in the UNFCCC NDC synthesis report, and best practices from the research community. We describe expectations for the process, conduct, presentation, and documentation of NDCs of HPA. These expectations provide qualitative benchmarks and criteria for assessing whether Parties have undertaken a rigorous and reasoned process to identify their highest possible mitigation efforts, and whether the evidence provided is sufficient to make that reasoning open to scrutiny. This promotes transparency and consistency in the formulation and assessment of NDCs, whilst intentionally not assessing targets against quantified mitigation benchmarks. Finally, the proposed expectations are contextualised and illustrated with examples from the latest round of NDC submissions. This practical translation of theoretical obligations can serve as a starting point for a deeper policy conversation on how HPA of NDCs can be evidenced, assessed or challenged.
Related
- Assessing Dynamical Contributions to SWOT Sea Surface Height in an Internal Tide Hotspot
- Variable contributions of vertical land motion to sea-level change inferred at tide gauges
- Stewardship practices enhance nature’s contributions to people
- Volatile organic compound emissions in croplands: The contributions of crops, soil, and agricultural management practices
- State-resolved multimodal contributions to stratospheric polar vortex predictability
BibTeX
@article{schonfeld2026assessing,
title = {{Assessing processes and evidence for highest possible ambition in Nationally Determined Contributions under the Paris Agreement}},
author = {Julia K Schönfeld and Setu Pelz and Hamish Beath and Joeri Rogelj},
journal = {Environmental Research Letters},
year = {2026},
month = oct,
doi = {10.1088/1748-9326/aeb55f},
url = {https://iopscience.iop.org/article/10.1088/1748-9326/aeb55f},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Assessing processes and evidence for highest possible ambition in Nationally Determined Contributions under the Paris Agreement
AU - Julia K Schönfeld
AU - Setu Pelz
AU - Hamish Beath
AU - Joeri Rogelj
PY - 2026
DA - 2026/10/26
JO - Environmental Research Letters
DO - 10.1088/1748-9326/aeb55f
UR - https://iopscience.iop.org/article/10.1088/1748-9326/aeb55f
AB - The Paris Agreement establishes that Parties’ Nationally Determined Contributions (NDCs) will represent a progression, a country’s highest possible ambition (HPA), and an equitable contribution to the collective long-term temperature goal. However, the agreement provides no guidance on how the HPA standard should be interpreted, assessed, or operationalised in practice. In response to this gap, initial scholarship has proposed frameworks to interpret HPA based on the treaty’s text and the wider international environmental law context, which includes the 2025 Advisory Opinion on Obligations of States in Respect of Climate Change from the International Court of Justice. Altogether, this has clarified how HPA is part of states’ due diligence obligations and sets the stage for the next challenge: how can the theoretical understanding of HPA be practically applied to assess whether NDCs reflect this norm? Here, we build on existing reporting obligations under the United Nations Framework Convention on Climate Change (UNFCCC), emerging approaches reflected in the UNFCCC NDC synthesis report, and best practices from the research community. We describe expectations for the process, conduct, presentation, and documentation of NDCs of HPA. These expectations provide qualitative benchmarks and criteria for assessing whether Parties have undertaken a rigorous and reasoned process to identify their highest possible mitigation efforts, and whether the evidence provided is sufficient to make that reasoning open to scrutiny. This promotes transparency and consistency in the formulation and assessment of NDCs, whilst intentionally not assessing targets against quantified mitigation benchmarks. Finally, the proposed expectations are contextualised and illustrated with examples from the latest round of NDC submissions. This practical translation of theoretical obligations can serve as a starting point for a deeper policy conversation on how HPA of NDCs can be evidenced, assessed or challenged.
SN - 1748-9326
ER -