The Kyoto Protocol, adopted in 1997 under the UN Framework Convention on Climate Change and in force from 2005, was the first treaty to set binding greenhouse-gas reduction targets for industrialised countries. It introduced market mechanisms such as emissions trading and the Clean Development Mechanism to help meet those targets. Its commitments applied to national governments rather than directly to cities. By pricing and capping emissions, it created pressure for lower-carbon energy, transport and land use.
The protocol began the formal carbon accounting that increasingly governs urban form, favouring compact development, public transit and energy-efficient buildings. It established the principle of binding emissions limits that later shaped municipal climate planning and the wider climate-policy regime.