‘Ocean–climate nexus’ explains how the oceans and atmosphere together control and express both the Earth’s daily weather systems and the long-term changes in planetary climate. The natural state for Earth during most of its history has been one of warm (greenhouse) conditions. These have been sporadically interrupted by cold (icehouse) conditions with a long-period cyclicity. For the past 3 million years, Earth has been in the grips of an icehouse period, during which glacial and interglacial periods have alternated with regularity. The human impact has been to influence these natural cycles of change dramatically, enhancing the greenhouse effect, and causing sea-level to rise. Global warming is one of the largest environmental issues facing humankind.