The Comprehensive Ocean-Atmosphere Data Set (COADS) is a comprehensive and easily accessible archive of global weather observations taken near the ocean's surface since 1854, primarily from merchant ships. The project, a cooperative effort between the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research (NCAR), aims to provide a detailed and consistent record of ocean-atmosphere behavior. The data set includes 70 million unique marine reports for 1854-1979, processed into monthly statistical summaries using 2° latitude × 2° longitude boxes. These summaries cover eight observed variables (air and sea-surface temperatures, scalar and vector wind, pressure, humidity, and cloudiness) and 11 derived variables. The development of COADS involved several stages, including data reduction, storage, quality control, and variable selection. The data set addresses known problems such as biases in sea-surface temperature measurements, inconsistencies in wind observations, and errors in ship identification and reporting codes. COADS is widely used by researchers and institutions for studying ocean climate and has been updated through 1986, with plans for further updates.The Comprehensive Ocean-Atmosphere Data Set (COADS) is a comprehensive and easily accessible archive of global weather observations taken near the ocean's surface since 1854, primarily from merchant ships. The project, a cooperative effort between the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Atmospheric Research (NCAR), aims to provide a detailed and consistent record of ocean-atmosphere behavior. The data set includes 70 million unique marine reports for 1854-1979, processed into monthly statistical summaries using 2° latitude × 2° longitude boxes. These summaries cover eight observed variables (air and sea-surface temperatures, scalar and vector wind, pressure, humidity, and cloudiness) and 11 derived variables. The development of COADS involved several stages, including data reduction, storage, quality control, and variable selection. The data set addresses known problems such as biases in sea-surface temperature measurements, inconsistencies in wind observations, and errors in ship identification and reporting codes. COADS is widely used by researchers and institutions for studying ocean climate and has been updated through 1986, with plans for further updates.