Lennart T Bach1
1Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
Atmospheric CO2 removal (CDR) is likely required as a supplement to rapid emission reductions to keep global warming below 2°C. Ocean afforestation has been proposed been proposed as a marine CDR (mCDR) method, but there is controversy around the effectiveness of this approach. A useful, yet underutilized, framework to assess the efficiency of ocean afforestation is “additionality” – defined as the difference of carbon sequestration by ocean afforestation relative to a baseline scenario where no ocean afforestation was plugged into the Earth System. Rigorous application of this framework shows that CO2 sequestration with ocean afforestation is (1) less efficient and (2) harder to verify than widely believed. This presentation argues that ocean afforestation may theoretically lead to CDR but is limited by fundamental biogeochemical constraints.