The rapid increase in atmospheric carbon dioxide (CO2) levels has stimulated a growing interest in understanding biogeochemical processes in the ocean and their interactions with the atmosphere. Interestingly, surface CO2 is also reported to be rising at the Joint Global Ocean Flux Study (JGOFS) ocean time series sites off Hawaii and Bermuda. Potential effects of rising CO2 levels include increases in global atmospheric and oceanic temperatures, melting of ice caps, sea-level rise and shifts in regional weather patterns, that lead to droughts and floods. One important question concerns our ability to discern natural versus anthropogenic contributions to this rise. Another question concerns the role the ocean plays in the cycling and variability of CO2. These and other unanswered questions stimulated the development and execution of JGOFS, a multidisciplinary and international program carried out between 1987 and 2001 by more than 20 nations. JGOFS was designed to study oceanic biogeochemical cycles and their interaction with a changing climate.