This manuscript presents the development of our current understanding of how the oceans operate and how past climates are reconstructed from the personal viewpoint of the author. It begins with the application of radiocarbon dating of carbonate rocks to deduce past climatic conditions. Age dating of carbonate sediments and microfossils provides a history of sea level rise and fall that closely matches fluctuations in temperature, which in turn correspond with cyclic changes in the Earth’s orbit. The origins of our understanding of how ocean circulation can affect global climate are reviewed and the essential role of atmospheric carbon-dioxide content is explored. Central to this climate link is the rate of CO2 flux between the various terrestrial reservoirs including seawater, glacial ice and the terrestrial biota. The manuscript concludes by describing how the collected knowledge about the carbon cycle provides insight into capture of CO2 from the atmosphere with the aim of storing it and attenuating the potentially devastating effects of fossil fuel burning on global climate change.