The Surface Ocean CO₂ Atlas (SOCAT, www.socat.info) is a synthesis activity by the international marine carbon community (>100 contributors) with support from SOLAS, IMBER, IOCCP, IOC and (inter-)national agencies. SOCAT brings together quality-controlled fCO₂ (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.5 million surface water fCO₂ values for the years 1957 to 2014 with more than 1.0 million fCO₂ values per year for 2006 to 2012. SOCAT now accepts well-calibrated, good quality fCO₂ measurements from alternative sensors and platforms. Dataset flags reflect the accuracy of surface water fCO₂ values, ranging from better than 2 micro-atm (for the highest quality data) to better than 10 micro-atm (for alternative sensors). Automation of data upload is now enabling annual SOCAT releases from version 4 onwards. The interactive Data Set Viewer allows effective interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. SOCAT version 4 is planned to be made public in early September 2016, and we'll highlight its updates above version 3 including observations to end of 2014. We will also present scientific applications of SOCAT including quantification of the ocean carbon sink and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. SOCAT represents a milestone in coordinating international researchers, for the delivery of publically accessible and uniformly quality-controlled datasets, for marine and global carbon research and for informing government climate policy.