COP30: Study reveals “highest possible ambition” for countries' climate pledges

A new study, for the first time, shows how the ‘highest possible ambition’ of countries' climate pledges can be assessed.

Under the Paris Agreement, each country’s Nationally Determined Contribution (NDC) – or climate pledge – must reflect its “highest possible ambition”. However, in the 10 years since the Agreement was signed, there has been little guidance on what this entails, allowing governments to assert ambition without evidence. 

A study, led by researchers at Imperial College London and published today in Environmental Research Letters, has created a framework to assess if countries' pledges are really meeting this requirement. 

“The Paris Agreement sets a clear expectation for high ambition, but there is currently no clear way to measure and assess that ambition,” says co-author Professor Joeri Rogelj. “We have developed a framework to fill that gap, providing a way to both design and assess climate pledges – and hold governments accountable if they’re not taking sufficient action.” 

The framework developed to assess ‘Highest Possible Ambition’ identifies three core pillars, each supported by specific criteria, to evaluate whether a country’s NDC reflects its best efforts. 

1. Domestic: NDCs should be based on a faithful assessment of mitigation options, using national capabilities. 
2. International: NDCs should support the achievement of the Paris Agreement temperature goals, while balancing equity 
3. Implementation: NDCs should account for the co-impacts of the measures and be actionable in the near-term to ensure ambition is translated into action. 

Drawing on the International Court of Justice (ICJ)’s recent opinion that countries have a legal obligation to address climate change, the authors clarify that the ‘highest possible ambition’ should be understood as a due-diligence obligation, which requires countries to make fair, evidence-informed, and proportionate contributions to the global temperature goal. 

Collective progress towards the Paris Agreement’s long term temperature goal remains hugely insufficient. Many countries’ updated NDCs have been delayed, and current pledges still fall far short of limiting global temperature rise to well below 2°C, let alone 1.5°C. 

 "Applying our Highest Possible Ambition framework to the assessment and formulation of NDCs will provide a foundation for transparent, consistent analysis, supporting accountability in global and national climate action and help to ensure that future climate pledges are both more ambitious, and credible," said lead author Julia Schönfeld.  

The study, A Framework to Assess Highest Possible Ambition in Nationally Determined Contributions under Article 4 of the Paris Agreement, by Julia Schönfeld (Imperial College London) and Professor Joeri Rogelj (Imperial College London), is published in Environmental Research Letters on 6 November 2025.