Timescales for detection of trends in the ocean carbon sink

A climate modelling experiment is used to identify where ocean carbon uptake should change as a result of anthropogenic climate change and to distinguish these changes from internal climate variability; we may be able to detect changing uptake in some oceanic regions between 2020 and 2050, but until then, internal climate variability will preclude such detection. The oceanic carbon sink over time The world's oceans have taken up vast amounts of amount of carbon produced by fossil fuel burning during the industrial era. These authors use a large ensemble of a single Earth system climate model, the Community Earth System Model–Large Ensemble (CESM–LE), to assess variability and change in the ocean carbon cycle in recent decades and through to 2100. This approach allows for a separation between trends in the air–sea carbon flux due to anthropogenic climate change and those due to internal climate variability. The study reveals how the ocean carbon sink may be expected to change throughout this century in different oceanic regions. The findings suggest that a large internal climate variability makes it unlikely that changes in the rate of anthropogenic carbon uptake can be directly observed in most oceanic regions at present, but that this may become possible between 2020 and 2050 in some regions. The ocean has absorbed 41 per cent of all anthropogenic carbon emitted as a result of fossil fuel burning and cement manufacture 1 , 2 . The magnitude and the large-scale distribution of the ocean carbon sink is well quantified for recent decades 3 , 4 . In contrast, temporal changes in the oceanic carbon sink remain poorly understood 5 , 6 , 7 . It has proved difficult to distinguish between air-to-sea carbon flux trends that are due to anthropogenic climate change and those due to internal climate variability 5 , 6 , 8 , 9 , 10 , 11 , 12 , 13 . Here we use a modelling approach that allows for this separation 14 , revealing how the ocean carbon sink may be expected to change throughout this century in different oceanic regions. Our findings suggest that, owing to large internal climate variability, it is unlikely that changes in the rate of anthropogenic carbon uptake can be directly observed in most oceanic regions at present, but that this may become possible between 2020 and 2050 in some regions.