A new approach to climate management

March 17 2017

It is increasing likely we will have to develop negative emissions if we are to meet the COP21 target of less than 2 degrees rise in the temperature. Negative emissions are where you draw carbon dioxide from the atmosphere and store in geological structures or in the ocean. A new paper by Dr Daniel Harrison of the University of Sydney has evaluated the capacity of the ocean to store carbon dioxide away from the atmosphere for a millennium. The process is termed ocean fertilisation and involves providing nutrients to the open ocean. In an earlier paper Dr Harrison showed that while iron fertilisation seems attractive, the scavenging of iron in the ocean leads to low sequestration efficiency. In the present paper he shows you would expect to sequester 2,600 million tonnes per year of carbon dioxide by using reactive nitrogen as a fertiliser. If you wished to add an additional nutrient, eg phosphate, this amount would increase to 5,800 million tonnes of carbon dioxide per year.

To keep the temperature rise to less than 2 degrees net emission must fall to zero. It is difficult to carry out a number activities without emitting carbon dioxide to the atmosphere. Aviation is one such activity that emits 780 thousand tonne per year (2015) of carbon dioxide. Ocean fertilisation has the capacity to remove this and other emissions that are hard to avoid at a modest cost.

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The capacity of the ocean to sequester carbon by the addition of reactive nitrogen.