Significance of the oceanic CO2 sink for national carbon accounts

BACKGROUND Under the United Nations convention on the law of the sea (1982), each participating country maintains exclusive economic and environmental rights within the oceanic region extending 200 nm from its coastline, known as the Exclusive Economic Zone (EEZ). Although the ocean within each EEZ has a vast capacity to absorb anthropogenic CO2 and therefore potentially be used as a carbon sink, it is not mentioned within the Kyoto Protocol most likely due to inadequate quantitative estimates. Here, I use two methods to estimate the anthropogenic CO2 storage and uptake for a typically large EEZ (Australia). RESULTS Depending on whether the Antarctic territory is included I find that during the 1990s between 30-40% of Australia's fossil-fuel CO2 emissions were absorbed by its own EEZ. CONCLUSION This example highlights the potential significance of the EEZ carbon sink for national carbon accounts. However, this 'natural anthropogenic CO2 sink' could be used as a disincentive for certain nations to reduce their anthropogenic CO2 emissions, which would ultimately dampen global efforts to reduce atmospheric CO2 concentrations. Since the oceanic anthropogenic CO2 sink has limited ability to be controlled by human activities, current and future international climate change policies should have an explicit 'EEZ' clause excluding its use within national carbon accounts.