Ocean iron fertilization for carbon dioxide removal and climate change mitigation

Just turning off the tap does not empty the bathtub, the bottom plug has to be opened. Similarly, just switching slowly from fossil to renewable energies will not stop in time the accumulation of huge amounts of greenhouse gases in the atmosphere. Among these gases, carbon dioxide will impact adversely all society and the planet. Indeed, natural processes are able to store carbon in terrestrial and marine environments, yet at a too slow rate compared to carbon dioxide emissions, promoting carbon dioxide accumulation in the atmosphere. Therefore, there is an urgent need to accelerate natural carbon storage to maintain the planet temperature 1.5–2.0 °C above the pre-industrial era. Thus, negative emission technologies should be developed and tested quickly. While these interventions are still debated due to possible negative effects, humans will not have another choice to avoid unprecedented changes in the Earth system. Here, we discuss ocean iron fertilization as a feasible, large-scale technique to increase atmospheric CO₂ capture and sequester carbon in the deep sea from decades to thousands of years.