Common But Differentiated Responsibilities (CBDR) is a principle that was formalized in the United Nations Framework Convention on Climate Change (UNFCCC) of Earth Summit in Rio de Janeiro, 1992.
[8] In the Earth Summit, the CBDR principle was established to apprise the world that pollution transcends political boundaries and that environmental protection should be achieved through means of cooperation.
UNFCCC 1992, Article 3 paragraph 1, "The Parties should protect the climate system for the benefit of present and future generations of humankind, on the basis of equity and in accordance with their common but differentiated responsibilities and respective capabilities.
Accordingly, the developed country Parties should take the lead in combating climate change and the adverse effects thereof.
There were other protocols and agreements that employed a principle of differential treatment: Todd Stern, then U.S. Special Envoy on Climate Change, said in his commencement speech at Dartmouth's 2012 graduation ceremony that the world can no longer have two distinct categories of countries having different responsibility for climate change mitigation.
Countries should instead follow differentiation of a continuum, where states are required to act vigorously according to their own circumstances, abilities and responsibilities.