Re-evaluating progress towards climate targets with consistent national carbon budgets

Country-level Remaining Carbon Budgets (RCBs) can act as tools for evaluating progress in climate policy under the Paris Agreement. However, current national RCB calculations often lack comparability with National Greenhouse Gas Inventories (NGHGIs), hindering accurate assessment of Nationally Determined Contributions and progress towards emission reduction targets. Here, we developed a NGHGI-compatible methodology for calculating RCBs, revealing a significant decrease in global RCB available for allocation to countries when aligned with NGHGI accounting principles.

Our analysis further demonstrates that over 50 countries have already exceeded their fair share of the 1.5°C-compatible RCB under this NGHGI-compatible framework, when considering responsibility for historical emissions. While developed countries with lower RCBs exhibit greater emission reduction ambitions, their efforts remain minuscule compared to their accrued carbon debt.

This research is particularly relevant in light of the recent European Court of Human Rights (ECHR) ruling in the KlimaSeniorinnen vs Switzerland case, which emphasized the importance of quantifying national GHG emission limitations, including through the establishment of national carbon budgets. We aim to highlight the need for a consistent and NGHGI-compatible approach to evaluate national climate policies and take a step towards aligning national RCB assessments with the realities of national emission reporting for more accurately assessing domestic climate action on a global scale.