The book deals with the question whether the investment treaty law system could be harmonized with the climate change international legal framework and the climate interest that lies beyond. The answer to this research question is divided into three parts. The first examines the relevance of the climate change international legal framework in investment treaty disputes as a natural pre(logical)interpretative stage. The second focuses on the BIT content-interpretation, which is the orthodox approach to solve the fragmentation between the system of investment treaty law and the system of international climate change law. Finally, the third part tackles this fragmentation through a heterodox approach that is grounded in the direct application of climate change principles through law ascertainment. Apart from concluding that harmonization between investment treaty law and international climate change law is possible through the orthodox approach to the expropriation and the FET standards, as well as through the direct application of the climate change precautionary principle and the CBDRRC principle − heterodox approach, the book suggests that tribunals are expected soon to openly address climate change disputes in their rulings.