Book excerpt: This book takes a critical lens to humanity’s collective regulatory response to the existential threat of climate change. It explores those aspects of the international climate change regime that, albeit born of political dysfunction, demonstrate ingenuity, innovation and experimentation. This includes aspects relating to the legal form of instruments in the regime, the legal character of its provisions, as well as norm hybridity and mutation, and the nature, extent and evolution of differential treatment in the regime. This book argues that innovations and experiments in the international climate change regime have resulted in a highly sophisticated and nuanced legal regime – one that challenges the conceptual boundaries of international law, enriches the core of treaty law and practice and is likely to have an enduring impact on international law, legal practice and diplomatic intercourse.