Measurements of the ocean’s carbonate system (e.g. CO₂ and pH) have increased greatly in recent years, resulting in a need to combine these data with satellite measurements and model results, so they can be used to test predictions of how the ocean reacts to changes such as absorption of the CO₂ emitted by humans. We show a method of combining data into regions of interest (100 km circles over a 10 d period) and apply it globally to produce a harmonised and easy-to-use data archive.