The adoption of the 1.5°C long-term warming limit in the Paris Agreement made 1.5°C a “hot topic” in the scientific community, with researchers eager to address this issue. Long-term warming limits have a decade-long history in international policy. To effectively inform the climate policy debate, geoscience research hence needs a core understanding of their legal and policy context. Here we describe this context in detail and illustrate its importance by showing the impact it can have on global carbon budget estimates. We show that definitional clarity is essential on this important matter.
