Abstract
Future sea-level change is characterized by both quantifiable and unquantifiable uncertainties. Effective communication of both types of uncertainties is a key challenge for translating sea-level science to inform long-term coastal planning. Scientific assessments play a key role in the translation process and have taken diverse approaches to communicating sea-level projection uncertainty. Here, we review how past Intergovernmental Panel on Climate Change (IPCC) and regional assessments have presented sea-level projection uncertainty, how IPCC presentations have been interpreted by regional assessments, and how regional assessments and policy guidance simplify projections for practical use. This information influenced the IPCC Sixth Assessment Report (AR6) presentation of quantifiable and unquantifiable uncertainty with the goal of preserving both elements as projections are adapted for regional application.