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

Area of Science:

• Climate Science
• Environmental Policy
• Earth System Science

Background:

• Remaining carbon budgets (RCBs) are crucial for assessing national climate mitigation efforts.
• Current RCB estimates lack consistency with national greenhouse gas inventory (NGHGI) accounting standards.
• Inconsistencies challenge accurate tracking of global climate goals and national responsibilities.

Purpose of the Study:

• To align national RCB calculations with established NGHGI accounting standards.
• To provide updated, methodologically consistent global and national RCB estimates.
• To assess country-level progress towards climate targets like 1.5°C and 2°C.

Main Methods:

• Reconciling RCB calculations with CO2 accounting principles used in NGHGIs.
• Quantifying the impact of NGHGI alignment on global RCBs for 1.5°C and 2°C scenarios.
• Calculating NGHGI-consistent national RCBs using common allocation methods.
• Evaluating national RCBs against equity principles outlined in the Paris Agreement.

Main Results:

• NGHGI alignment reduces the global 1.5°C (50%) RCB by ~100 GtCO2 (~50%) and the 2°C (66%) RCB by ~200 GtCO2 (~20%) for 2024.
• The NGHGI-consistent global RCB for 1.5°C (50%) is estimated to be depleted by 2027.
• By 2025, 64-85 countries may have surpassed their equitable share of the 1.5°C (50%) RCB.

Conclusions:

• Aligning RCBs with NGHGI standards provides a more robust framework for tracking mitigation progress.
• Current national mitigation efforts, when assessed against NGHGI-consistent RCBs, reveal significant overspending of equitable carbon shares for many countries.
• The developed framework supports more accurate country-level assessments of climate action and accountability.