We are thrilled to inform you that the Surface Ocean CO₂ Atlas (SOCAT) version 2025 is now available on the SOCAT website. We would like to congratulate and thank the entire SOCAT team, as well as all data providers, for their enormous continuous efforts related to annual releases of the product.

The annual mean growth rate of atmospheric carbon dioxide (CO₂) was 3.77 ppm (µmol mol-1) in 2024, a record high rate, highlighting the urgent need for quantification of the ocean carbon sink. Since 2011, the community-led Surface Ocean CO₂ Atlas (SOCAT; www.socat.info) offers an annual public update of global in situ oceanic fCO₂ (fugacity of CO₂) measurements. Version 2025 adds 451 new data sets and updates 44 data sets from ships, yachts, uncrewed surface vehicles (USVs), moorings and drifting platforms. Version 2025 contains 41.4 million, quality-controlled, in situ surface ocean fCO₂ measurements with an estimated uncertainty of better than 5 μatm collected between 1957 and 2024, which constitute the main SOCAT synthesis and gridded products. In addition, 8.2 million fCO₂ values with an uncertainty of 5 - 10 µatm, mainly from membrane-based sensors, are made separately available. Open ocean CO₂ data submissions have stabilised, as shown by the number of monthly, 1° by 1° gridded, surface ocean fCO₂ values in 2020 to 2023. Documentation of data sets has improved over time (reduction in D flags). SOCAT is key for quantification of ocean CO₂ uptake and ocean acidification, providing vital information for climate policy. As the importance of constraining ocean CO₂ uptake is well recognized by the WMO Global Greenhouse Gas Watch (G3W) and the UNFCCC Global Stocktake, there is an urgent need for sustained funding of accurate surface ocean CO₂ measurements and their synthesis. The SOCAT synthesis effort remains at risk by reliance on a single hub and funding.

 
For more information, please see the SOCAT v2025 release poster and visit www.socat.info