The principle of Common But Differentiated Responsibilities and Respective Capabilities (CBDR-RC) is a foundational concept in international environmental law, specifically within the global climate change regime. It was officially enshrined in the United Nations Framework Convention on Climate Change (UNFCCC) at the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro. The concept was created to solve the problem of how to address a global environmental crisis while acknowledging the historical and economic disparities between nations.
The "common" element signifies that all states share an obligation to protect the global climate system. The "differentiated" element recognizes that states have varying duties and abilities to address climate change, primarily because developed countries have historically contributed the largest share of greenhouse gas emissions and possess greater technological and financial resources. Article 3, paragraph 1 of the UNFCCC states that parties should protect the climate system "on the basis of equity and in accordance with their common but differentiated responsibilities and respective capabilities," and that developed country parties "should take the lead". This mechanism initially divided countries into Annex I (developed and transition economies) and Non-Annex I (developing countries), with Annex I countries having stricter obligations for mitigation and providing financial and technological assistance.
CBDR-RC is closely connected to the Paris Agreement of 2015, which explicitly references the principle in Article 2. The Paris Agreement introduced a significant change by moving away from the rigid Annex I/Non-Annex I dichotomy toward a system where all parties submit Nationally Determined Contributions (NDCs). While the core principle of differentiation remains, the Paris Agreement added the phrase "in the light of different national circumstances" to the principle, introducing a more dynamic element that acknowledges that a country's status and capabilities are not static. This shift allows countries to determine their own pledges based on their perceived responsibility and capability, while still expecting developed countries to "take the lead" in mitigation and finance under Article 4.4.