The ocean represents 97% of the physical habitable space on the planet and is central to sustaining all life on Earth. Since 2000 significant and dedicated effort has been directed at raising awareness and understanding of the consequences of greenhouse gas emissions on the ocean. Carbon dioxide emitted by human activities is driving the ocean towards more acidic conditions. Only in the past decade has it started to become more widely recognized that the temperature of the global ocean is also being significantly affected as a result of the effect that the carbon dioxide and other potent greenhouse gases are having in the Earth’s atmosphere. The heating of seawater and progressive acidification are not the only major global consequences of greenhouse gases emissions in the marine realm. It has been known for some decades that nutrient run-off from agriculture causes oxygen-depleted zones to form in the sea, as life-giving oxygen is used up in the water column and on the sea floor. This phenomenon is called ‘ocean deoxygenation’. Ocean deoxygenation: everyone's problem tells the scale and nature of the changes being driven by ocean deoxygenation.