At present time, the international community has accepted a 2°C temperature increase above preindustrial levels as the maximum tolerable limit for global warming. Extrapolating from current global CO₂ emissions and results from current climate models, the equivalent emission budget will last only for little more than a decade. It therefore seems prudent to consider all possible options in addressing potentially dangerous climate change. Researchers from the Cluster have provided a comprehensive assessment that combines scientific, economic and legal issues of the potential and risks of one such option for enhancing the ocean carbon uptake: ocean iron fertilization (OIF).

From a scientific perspective, the potential of carbon sequestration of large-scale OIF is considerable (see Fig.), but there is also evidence for significant perturbations of marine biogeochemistry and ecology. These are partly desired but may also have potentially significant unintended consequences including enhanced production of nitrous oxide (N₂O) and methane (CH₄) (Oschlies et al. 2010). From an economic perspective, the potential of OIF is significant in relation to other abatement options. First estimates of the costs associated with this technology are in the same order of magnitude as the estimates of the costs associated with forestation projects. OIF could also generate more carbon credits, even taking into account the possibility that emissions will shift to other regions or that the reductions are not permanent. As for the conformity of OIF with the requirements of public international law, the pertinent agreements dealing with the protection of the marine environment indicate that OIF is to be considered lawful to the extent to which it represents legitimate scientific research. According to Güssow et al. (2010), further scientific research must be permitted to explore the carbon sequestration potential of the ocean. Such research is necessary to make an informed decision on whether to reject ocean iron fertilization or to integrate it into the flexible mechanisms contained in the Kyoto Protocol.

References:
Güssow, K., Proelss, A., Oschlies, A., Rehdanz, K., Rickels, W. (2010) Ocean Iron Fertilization: Why Further Research is Needed. Mar. Policy 34, 911–918.

Oschlies, A., Koeve, W., Rickels, W., Rehdanz, K. (2010) Side effects and accounting aspects of hypothetical largescale Southern Ocean iron fertilization. Biogeosciences 7, 4017–4035.

Rickels, W., Rehdanz, K., Oschlies, A. (2010) Methods for Greenhouse Gas Offsets Accounting: A Case Study of Ocean Iron Fertilization. Ecol. Econ. 69, 2495–2509.

Caption: Annual average nitrate concentrations in the surface waters of the oceans. Source: http://www.atmosphere.mpg.de/enid/1vv.html