This work was supported by Católica Research Centre for the Future of Law and Vieira de Almeida & Associados. 2024-2025 marks a pivotal shift in international climate law, as advisory opinions before international and regional courts and tribunals begin to shape the global response to the climate crisis. With one advisory opinion already issued and two more anticipated in 2025, this collective effort to define and enforce States’ climate obligations is gaining momentum. This book captures this critical juncture, featuring chapters by leading scholars and litigators involved in these landmark advisory opinions. Against the backdrop of decades of domestic climate litigation, the transition to international courts reflects the urgent need for global solutions to a challenge that transcends borders, offering vital insights for the path forward.