# Tracking country-level mitigation progress using NGHGI-consistent carbon budgets

## TL;DR

This study aligns carbon budgets with national emissions accounting, showing that many countries may have already exceeded their fair share of allowable emissions for 1.5°C.

## Contribution

The novel contribution is aligning remaining carbon budgets with national greenhouse gas inventory standards to provide more accurate and equitable benchmarks.

## Key findings

- Aligning with NGHGI reduces the 1.5°C (50%) global RCB by ~100 GtCO2, likely to be depleted by 2027.
- 64–85 countries could have exceeded their fair-share RCB for 1.5°C (50%) by 2025.
- NGHGI-consistent national RCBs are provided for most countries and common allocation methods.

## Abstract

The remaining carbon budget (RCB) of countries provides a benchmark for evaluating national mitigation efforts and was central to a recent European Court of Human Rights’ ruling. However, estimates of national RCBs are inconsistent with CO2 accounting in national greenhouse gas inventories (NGHGIs). Here, we align RCBs with NGHGI accounting standards. For 2024, NGHGI alignment reduces the 1.5 °C (50%) global RCB by  ~100 GtCO2 ( ≈ 50%) and the 2 °C (66%) RCB by  ~200 GtCO2 ( ≈ 20%). Thus, we estimate the 1.5 °C (50%) NGHGI-consistent global RCB to be depleted by 2027. We provide NGHGI-consistent national RCBs for common allocation methods and most countries. Following Paris Agreement equity principles, we find that by 2025, 64–85 countries could have exceeded their fair-share RCB for 1.5 °C (50%). While national RCBs depend on normative choices and are unlikely to directly drive negotiations, our framework enables more methodologically robust RCB calculations to track country-level mitigation progress.

This study shows that aligning remaining carbon budgets with national greenhouse gas inventory accounting reduces the global 1.5 ∘C (50%) budget by  ~100 GtCO2, with possible depletion around 2027, and suggests that 64-85 countries could have exceeded their fair share by 2025.