A principle-based framework to determine countries' fair warming contributions to the Paris Agreement

Area of Science:

• Climate science
• Environmental policy
• International relations

Background:

• Equity is central to global climate policy, but consensus on allocating mitigation efforts is lacking.
• Existing research often overlooks non-carbon dioxide (CO2) emissions and their warming impacts.
• A comprehensive approach considering all greenhouse gases is needed for fair climate action.

Purpose of the Study:

• To establish a global warming budget encompassing all anthropogenic greenhouse gases.
• To allocate this budget to countries based on international treaty and environmental law principles.
• To assess countries' progress toward climate goals considering their fair share of emissions.

Main Methods:

• Developed a global warming budget framework for all greenhouse gases.
• Allocated budget shares to countries using principles from international law.
• Analyzed country-level emissions against allocated budget shares for 1.5°C and 2°C warming scenarios.

Main Results:

• By 2021, 84-90 countries, including major developed nations, had exhausted their 1.5°C budget share.
• A similar trend was observed for the 2°C warming limit.
• Many nations will exceed their fair share even with maximal Paris Agreement pledges.

Conclusions:

• Current national emission reduction pledges may be insufficient to meet global climate targets equitably.
• Fairness considerations must extend beyond domestic emissions to encompass broader responsibilities.
• Rethinking climate equity requires exploring factors beyond national mitigation efforts.