Efforts to validate, monitor, and verify ocean-based carbon dioxide removal (CDR) will require a rich understanding of the ocean carbon system. Ocean observations anchor this understanding, but we know that some ongoing observations are precariously funded, that data products like SOCAT rely on volunteer effort, that regions essential to our understanding of the ocean carbon system are under-observed, and that some observation data is under-used. We tried to identify what ocean observation data already exists, and how it is being used internationally. This will help us identify where we need more data in order to build a complete picture of the ocean carbon system.