The CARBON-OPS data set comprises partial pressure of carbon dioxide (pCO2) and ancilliary parameters, measured aboard selected UK research vessels between 2007 and 2008. The parameter suite includes geographical position; partial pressure and fugacity of CO2; sea surface temperature, salinity, and dissolved oxygen concentration; air pressure, temperature and humidity; occasionally the parameter suite also includes fluorescence, transmittance, wind speed and direction. CARBON-OPS, led by Nick Hardman-Mountford at Plymouth Marine Laboratory, was funded by the Natural Environment Research Council under the Knowledge Transfer initiative (2007-2009). The aim of the project was to develop an automated supply chain of ocean surface and atmospheric carbon dioxide measurements from research ships to operational end-users. The data were first provided in near real-time following an initial level of automated quality control and processing. Following a secondary level of manual quality control and processing (delayed mode) the data are integrated into the BODC National Oceanographic Database. Measurements were taken aboard five UK research vessels: RRS Discovery, RRS James Clark Ross; RRS James Cook; RV Plymouth Quest; and RV Prince Madog.