The ocean absorbs around 30% of human-caused CO₂ emissions each year. Accurate and up-to-date estimates of ocean carbon uptake are therefore essential for effective policies on climate mitigation, adaptation, and carbon management. Current knowledge of this uptake is derived from estimates that integrate surface ocean CO2 observations from regional seas and the open ocean worldwide.This audit provides a first assessment of Europe’s contribution to global ocean carbon monitoring and assessment, covering the observational, data synthesis, analytical, and modelling roles. It shows that European biogeochemical models and data products are the primary engines driving the Global Carbon Budget and international climate assessments. However, the audit identifies a critical “leadership mismatch”: Europe’s excellent capacity in modelling and data products rests on a fragile and declining observational foundation and weak data stewardship capacity. Addressing this imbalance is essential for Europe’s strategic autonomy and for meeting its European Ocean Pact goals and Paris Agreement commitments. Key findings• European leadership: Europe leads globally in ocean carbon modelling and data products; its outputs are the gold standard for tracking changes in the global ocean carbon sinks.• Measurement-model mismatch: Europe’s advanced modelling and data product capacity increasingly depends on surface ocean CO2 observations provided by a shrinking number of countries.• Regional blind spots: Severe and persistent gaps in observations remain around Europe in the Black Sea and the Mediterranean Sea, as well as in the climatically important Southern Ocean.• Stewardship risks: The absence of an operational European SOCAT (Surface Ocean CO2 Atlas) data synthesis hub creates a global single point of failure for the quality and continuity of data stewardship across the value chain from observations to policy-relevant information.