This chapter explores the overall architecture of international climate change law. Following a discussion of the defining features of climate change law, it discusses the origins and development of the 1992 United Nations Framework Convention on Climate Change (UNFCCC) and subsequent arrangements adopted under its auspices, notably the 1997 Kyoto Protocol and the 2010 Cancún Agreements. The authors argue that while the UNFCCC process has grown more complex over time – in terms of its rules, institutions and the actors involved – so has international climate change law and governance more generally. It illustrates this argument by drawing attention to six observable trends: (i) the multiplication of international forums addressing climate change; (ii) the softening of commitments; (iii) the changing nature of differentiation; (iv) the utilization of innovative policy instruments; (v) the increasing focus on litigation; and (vi) the growing importance of nonstate actors and transnational governance.