In order to keep global warming below 2°C, the use of geoengineering is being considered. Geoengineering is a human large-scale, long-term intervention in natural cycles with the goal to mitigate global warming. One broadly discussed way of extracting CO2 from the atmosphere is iron-fertilization of the ocean, in particular the Southern Ocean. This essay will examine the ocean as a natural carbon dioxide sink and how it could be utilized by this geoengineering method. Some practicalities and risks are looked at and evaluated to come to the conclusion that iron-fertilization of the Southern Ocean could mitigate rising CO2 levels. Nevertheless, we should not do it, because the potential benefits of the technology do not weigh up its risks for the ecosystem.