Over oceans, high uncertainties in satellite CO₂ retrievals exist due to limited reference data. We combine commercial ship and aircraft observations and, with the aid of model calculations, obtain column-averaged mixing ratios of CO₂ (XCO₂) data over the Pacific Ocean. This new dataset has great potential as a robust reference for XCO₂ measured from space and can help to better understand changes in the carbon cycle in response to climate change using satellite observations.