This dataset is Surface Ocean CO2 Atlas (SOCAT) version 4. This dataset includes surface underway, chemical, meteorological, navigational and physical data collected from unknown platforms in the world-wide oceans from 1968-11-16 to 2014-12-31. These data include BAROMETRIC PRESSURE, LATITUDE, LONGITUDE, Partial pressure (or fugacity) of carbon dioxide - water, SALINITY and SEA SURFACE TEMPERATURE. The Surface Ocean CO2 Atlas (SOCAT) is an international effort, endorsed by the International Ocean Carbon Coordination Project (IOCCP), the Surface Ocean Lower Atmosphere Study (SOLAS) and the Integrated Marine Biogeochemistry and Ecosystem Research program (IMBER), to deliver a uniformly quality-controlled surface ocean CO2 database.

This dataset includes Surface Ocean CO2 Atlas (SOCAT) version 2, a synthesis product of the surface water fugacity of CO2 (fCO2) for the global oceans and coastal seas from 1968-11-16 to 2011-12-31. The Surface Ocean CO2 Atlas (SOCAT) is an international effort, supported by the International Ocean Carbon Coordination Project (IOCCP), the Surface Ocean Lower Atmosphere Study (SOLAS), and the Integrated Marine Biogeochemistry and Ecosystem Research program (IMBER), to deliver a uniformly quality-controlled surface ocean CO2 database.

This dataset includes Surface Ocean CO2 Atlas Database Version 1.5 (SOCATv1.5)

This dataset consists of the Surface Ocean CO2 Atlas (SOCAT) data product files. SOCAT is a synthesis activity by the international marine carbon research community and has more than 100 contributors worldwide. SOCAT provides access to synthesis and gridded, quality controlled, observational products of surface ocean fCO2 (fugacity of carbon dioxide) for the global oceans and coastal seas. SOCAT version 6 has 23.4 million, in situ, surface ocean fCO2 measurements with an accuracy of better than 5 μatm and a WOCE flag of 2 (good) from 1957 to 2017. Calibrated sensor data with an accuracy of better than 10 μatm are also available. During quality control, marine scientists assign a flag to each data set, as well as WOCE flags of 2 (good), 3 (questionable) or 4 (bad) to individual fCO2 values. Data sets are assigned flags of A and B for an accuracy of better than 2 μatm, flags of C and D for an accuracy of better than 5 μatm and a flag of E for an accuracy of better than 10 μatm. Bakker et al. (2016) describe the quality control criteria used in SOCAT versions 3 to 6. Quality control comments for individual data sets can be accessed via the SOCAT Data Set Viewer (www.socat.info). All data sets, where data quality has been deemed acceptable, have been made public. The main SOCAT synthesis files and the gridded products contain all data sets with flags of A to D and fCO2 values with a flag of 2. Access to data sets with a flag of E and fCO2 values with flags of 3 and 4 is via additional data products and the Data Set Viewer (Table 8 in Bakker et al., 2016). SOCAT publishes a global gridded product with a 1° longitude by 1° latitude resolution. A second product with a higher resolution of 0.25° longitude by 0.25° latitude is available for the coastal seas. Gridded products are available monthly, per year and per decade. Two powerful, interactive, online viewers, the Data Set Viewer and the Gridded Data Viewer (www.socat.info), enable investigation of the SOCAT synthesis and gridded data products. SOCAT data products can be downloaded. Matlab code is available for reading these files. Ocean Data View also provides access to the SOCAT data products (www.socat.info). SOCAT data products are discoverable, accessible and citable. SOCAT versions 3 to 6 should be cited as Bakker et al., 2016 (until a publication on versions 4, 5 and 6 is published). The SOCAT Fair Data Use Statement (www.socat.info) asks users to generously acknowledge the contribution of SOCAT scientists by invitation to co-authorship, especially for data providers in regional studies, and/or reference to relevant scientific articles. The SOCAT website (www.socat.info) provides a single access point for online viewers, downloadable data sets, the Fair Data Use Statement, a list of contributors and an overview of scientific publications on and using SOCAT. Automation of data upload and initial data checks allows annual releases of SOCAT from version 4 onward. SOCAT enables quantification of the ocean carbon sink and ocean acidification and evaluation of ocean biogeochemical models. More than 210 peer-reviewed scientific publications and high-impact reports cite SOCAT. SOCAT represents a milestone in research coordination, data access, biogeochemical and climate research and in informing policy.

This dataset consists of the Surface Ocean CO2 Atlas Version 2021 (SOCATv2021) data product files. The Surface Ocean CO2 Atlas (SOCAT) documents the increase in surface ocean CO2 (carbon dioxide), a critical measure as the oceans are taking up one quarter of the global CO2 emissions from human activity. SOCAT version 2021 has 30.6 million quality-controlled surface ocean fCO2 (fugacity of CO2) observations with an estimated accuracy of better than 5 μatm and a WOCE flag of 2 (good) from 1957 to 2020 for the global oceans and coastal seas. In addition, 2.1 million values with an estimated accuracy of 5 to 10 μatm are available. During quality control, marine scientists assign a flag to each data set, as well as WOCE flags of 2 (good), 3 (questionable) or 4 (bad) to individual fCO2 values. Data sets are assigned flags of A and B for an estimated accuracy of better than 2 μatm, flags of C and D for an accuracy of better than 5 μatm and a flag of E for an accuracy of better than 10 μatm. Bakker et al. (2016) describe the quality control criteria used in SOCAT versions 3 to 2021. Quality control comments for individual data sets can be accessed via the SOCAT Data Set Viewer (www.socat.info). All data sets, where data quality has been deemed acceptable, have been made public. The main SOCAT synthesis files and the gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Access to data sets with an estimated accuracy of 5 to 10 (flag of E) and fCO2 values with flags of 3 and 4 is via additional data products and the Data Set Viewer (Table 8 in Bakker et al., 2016). SOCAT publishes a global gridded product with a 1° longitude by 1° latitude resolution. A second product with a higher resolution of 0.25° longitude by 0.25° latitude is available for the coastal seas. The gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Gridded products are available monthly, per year and per decade. Two powerful, interactive, online viewers, the Data Set Viewer and the Gridded Data Viewer (www.socat.info), enable investigation of the SOCAT synthesis and gridded data products. SOCAT data products can be downloaded. Matlab code is available for reading these files. Ocean Data View also provides access to the SOCAT data products (www.socat.info). SOCAT data products are discoverable, accessible and citable. The SOCAT Data Use Statement asks users to generously acknowledge the contribution of SOCAT scientists by invitation to co-authorship, especially for data providers in regional studies, and/or reference to relevant scientific articles. The SOCAT website (www.socat.info) provides a single access point for online viewers, downloadable data sets, the Data Use Statement, a list of contributors and an overview of scientific publications on and using SOCAT. Automation of data upload and initial data checks allows annual releases of SOCAT from version 4 onwards. SOCAT-based data products are used for quantification of the ocean carbon sink, to estimate ocean acidification, for evaluation of biogeochemical sensor data and to evaluate climate models (CMIP). Since 2013 SOCAT products inform the annual Global Carbon Budget. The annual SOCAT releases are made by the SOCAT scientific community as a Voluntary Commitment for United Nations Sustainable Development Goal 14.3 (Reduce Ocean Acidification) (#OceanAction20464). More broadly the SOCAT releases contribute to UN SDG 13 (Climate Action) and SDG 14 (Life Below Water), and to the UN Decade of Ocean Science for Sustainable Development. Hundreds of peer-reviewed scientific publications and high-impact reports cite SOCAT. The SOCAT community-led synthesis product is a key step in the value chain based on in situ inorganic carbon measurements of the oceans, which provides policy makers with essential

This dataset consists of the Surface Ocean CO2 Atlas (SOCAT) data product files. SOCAT is a synthesis activity by the international marine carbon research community and has more than 100 contributors worldwide. SOCAT provides access to synthesis and gridded, quality controlled, observational products of surface ocean fCO2 (fugacity of carbon dioxide) for the global oceans and coastal seas. SOCAT version 2020 has 28.2 million quality-controlled surface ocean fCO2 (fugacity of CO2) observations with an estimated accuracy of better than 5 μatm and a WOCE flag of 2 (good) from 1957 to 2020 for the global oceans and coastal seas. In addition, 2.3 million values with an estimated accuracy of 5 to 10 μatm are available. During quality control, marine scientists assign a flag to each data set, as well as WOCE flags of 2 (good), 3 (questionable) or 4 (bad) to individual fCO2 values. Data sets are assigned flags of A and B for an accuracy of better than 2 μatm, flags of C and D for an accuracy of better than 5 μatm and a flag of E for an accuracy of better than 10 μatm. Bakker et al. (2016) describe the quality control criteria used in SOCAT versions 3, 4, 5, 6, 2019 and 2020. Quality control comments for individual data sets can be accessed via the SOCAT Data Set Viewer. All data sets, where data quality has been deemed acceptable, have been made public. The main SOCAT synthesis files and the gridded products contain all data sets with an estimated accuracy of better than 5 µatm (flags of A to D) and fCO2 values with a flag of 2. Access to data sets with an estimated accuracy of 5 to 10 (flag of E) and fCO2 values with flags of 3 and 4 is via additional data products and the Data Set Viewer (Table 8 in Bakker et al., 2016). SOCAT publishes a global gridded product with a 1° longitude by 1° latitude resolution. A second product with a higher resolution of 0.25° longitude by 0.25° latitude is available for the coastal seas. Gridded products are available monthly, per year and per decade. Two powerful, interactive, online viewers, the Data Set Viewer and the Gridded Data Viewer (www.socat.info), enable investigation of the SOCAT synthesis and gridded data products. SOCAT data products can be downloaded. Matlab code is available at www.socat.info for reading these files. Ocean Data View also provides access to the SOCAT data products (www.socat.info). SOCAT data products are discoverable, accessible and citable. SOCAT versions 3 to 2020 should be cited as Bakker et al., 2016 (until a publication on versions 4 to 2020 is published). The SOCAT Data Use Statement (www.socat.info) asks users to generously acknowledge the contribution of SOCAT scientists by invitation to co-authorship, especially for data providers in regional studies, and/or reference to relevant scientific articles. The SOCAT website (www.socat.info) provides a single access point for online viewers, downloadable data sets, the Data Use Statement, a list of contributors and an overview of scientific publications on and using SOCAT. Automation of data upload and initial data checks allows annual releases of SOCAT from version 4 onwards. SOCAT enables quantification of the ocean carbon sink and ocean acidification, as well as evaluation of sensor data and ocean biogeochemical models. More than 329 peer-reviewed scientific publications and 80 high-impact reports cite SOCAT. SOCAT represents a milestone in biogeochemical and climate research. SOCAT informs policy and high-profile climate negotiations. Maintenance and annual updates of the SOCAT product require sustained funding and community involvement.

The ocean absorbs one quarter of the global CO2 emissions from human activity. The community-led Surface Ocean CO2 Atlas (www.socat.info) is key for the quantification of ocean CO2 uptake and its variation, now and in the future. SOCAT version 2025 has quality-controlled in situ surface ocean fCO2 (fugacity of CO2) measurements on ships, moorings, sailing yachts, autonomous and drifting surface platforms for the global ocean and coastal seas from 1957 to 2024. The main SOCAT synthesis and gridded products contain fCO2 values with an estimated accuracy of better than 5 μatm. Sensor fCO2 data with an estimated accuracy of better than 10 μatm are separately available. During secondary quality control, marine scientists assign a flag to each data set, as well as WOCE flags of 2 (good), 3 (questionable) or 4 (bad) to individual fCO2 values. Data sets are assigned flags of A and B for an estimated accuracy of better than 2 μatm, flag of C (and D) for an accuracy of better than 5 μatm and a flag of E for an accuracy of better than 10 μatm. Bakker et al. (2016) describe the quality control criteria used from SOCAT version 3 onward. SOCAT quality control cookbooks provide quality control updates (www.socat.info), with (Gkritzalis et al., 2024) used for version 2025. Quality control comments for individual data sets can be accessed via the SOCAT Data Set Viewer (www.socat.info). All data sets, where data quality has been deemed acceptable, have been made public. The main SOCAT synthesis files and the gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Access to data sets with an estimated accuracy of better than 10 µatm (flag of E) and fCO2 values with flags of 3 and 4 is via additional data products and the Data Set Viewer (Table 8 in Bakker et al., 2016). SOCAT publishes a global gridded product with a 1° longitude by 1° latitude resolution without gap filling. A second product with a higher resolution of 0.25° longitude by 0.25° latitude is available for the coastal seas. The gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Gridded products are available monthly, per year and per decade. Two powerful, interactive, online viewers, the Data Set Viewer and the Gridded Data Viewer (www.socat.info), enable investigation of the SOCAT synthesis and gridded data products. SOCAT data products can be downloaded. Matlab code is available for reading these files. Ocean Data View also provides access to the SOCAT data products (www.socat.info). SOCAT data products are discoverable, accessible and citable. The SOCAT Data Use Statement (www.socat.info) asks users to generously acknowledge the contribution of SOCAT scientists by invitation to co-authorship, especially for data providers in regional studies, and/or reference to relevant scientific articles. It also asks users to cite the relevant SOCAT data set, the relevant methods paper(s), and to use acknowledgement text (https://socat.info/index.php/citing-socat/). The SOCAT website (www.socat.info) provides a single access point for online viewers, downloadable data sets, the Data Use Statement, a list of contributors and an overview of scientific publications on SOCAT and using SOCAT. Automation of data upload and initial data checks have allowed annual releases of SOCAT from version 4 onwards. Automation of metadata upload is ongoing. SOCAT is used for quantification of ocean CO2 uptake and ocean acidification and for evaluation of earth system models and sensor data. SOCAT products inform on ocean CO2 uptake in the annual Global Carbon Budget since 2013. SOCAT is a key element of the World Meteorological Organization’s (WMO) Global Greenhouse Gas Watch (G3W) program and is a key resource for Copernicus’ evaluations. The annual SOCAT releases by the SOCAT scientific

This dataset consists of the GLODAPv2.2020 data product composed of data from 946 scientific cruises covering the global ocean between 1972 and 2019. It includes full depth discrete bottle measurements of salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon (TCO2), total alkalinity (TAlk), CO2 fugacity (fCO2), pH, chlorofluorocarbons (CFC-11, CFC-12, CFC-113, and CCl4), various isotopes and organic compounds. It was created by appending data from 106 cruises to GLODAPv2.2019 (Olsen et al., 2019, NCEI Accession 0186803). The data for salinity, oxygen, nitrate, silicate, phosphate, TCO2, TAlk, pH, CFC-11, CFC-12, CFC-113, and CCl4 were subjected to primary and secondary quality control. Severe biases in these data have been corrected for, and outliers removed. However, differences in data related to any known or likely time trends or variations have not been corrected for. These data are believed to be accurate to 0.005 in salinity, 1% in oxygen, 2% in nitrate, 2% in silicate, 2% in phosphate, 4 µmol kg-1 in TCO2, 4 µmol kg-1 in TAlk, and for the halogenated transient tracers: 5%.

This dataset consists of GLODAPv2.2019 data product composed of data from 840 scientific cruises covering the global ocean between 1972 and 2017. It includes full depth discrete bottle measurements of salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon (TCO2), total alkalinity (TAlk), pH, chlorofluorocarbons (CFC-11, CFC-12, CFC-113, and CCl4), various isotopes and organic compounds. It was created by appending data from 116 cruises to GLODAPv2 (Olsen et al., 2016, NCEI Accession 0162565). The data for salinity, oxygen, nitrate, silicate, phosphate, TCO2, TAlk, pH, CFC-11, CFC-12, CFC-113, and CCl4 were subjected to primary and secondary quality control. Severe biases in these data have been corrected for, and outliers removed. However, differences in data related to any known or likely time trends or variations have not been corrected for. These data are believed to be accurate to 0.005 in salinity, 1% in oxygen, 2% in nitrate, 2% in silicate, 2% in phosphate, 4 µmol kg-1 in TCO2, 4 µmol kg-1 in TAlk, and for the halogenated transient tracers: 5%.

The ocean is a sink for ~25% of the atmospheric CO2 emitted by human activities, an amount in excess of 2 petagrams of carbon per year (PgC yr−1). Time-resolved estimates of global ocean-atmosphere CO2 flux provide an important constraint on the global carbon budget. However, previous estimates of this flux, derived from surface ocean CO2 concentrations, have not corrected the data for temperature gradients between the surface and sampling at a few meters depth, or for the effect of the cool ocean surface skin. Here we calculate a time history of ocean-atmosphere CO2 fluxes from 1992 to 2018, corrected for these effects. These increase the calculated net flux into the oceans significantly.