Recently, Wang Lei, a doctoral student of Department of Earth System Science, published a paper in Scientific Reports titled “Narrowing the spread in CMIP5 model projections of air-sea CO2 fluxes”.

The ocean is a large carbon sink on earth. Limited by the lack of understanding of ocean carbon cycle and the development level of the models, a large spread exists in the CMIP5 model simulation and projection of air-sea CO2 fluxes, which contributes to the uncertainty in model simulation and projection of climate change. Two methods are applied to narrow the spread in CMIP5 model projections of air-sea CO2 fluxes in this study. One method involves model selection based on the ability of models to reproduce the observed air-sea CO2 fluxes from1982-2005. The other method involves constrained estimation based on the strong relationship between the historical and future air-sea CO2 ?0?4uxes. The estimated spread of the projected air-sea CO2 ?0?4uxes is e?0?2ectively reduced by using these two approaches. These two approaches also show great agreement in the global ocean and three regional oceans of the equatorial Pacific Ocean, the North Atlantic Ocean and the Southern Ocean, including the average state and evolution characteristics. Based on the projections of the two approaches, the global ocean carbon uptake will increase in the first half of the 21st century then remain relatively stable and is projected to be 3.68–4.57 PgC/yr at the end of 21st century. The projections indicate that the increase in the CO2 uptake by the oceans will cease at the year of approximately 2070.

Figure Historical (1861–2005) and projected (2006–2099) air-sea CO2 ?0?4uxes. The air-sea CO2 ?0?4uxes in the 21st century are projected via the selected models method (thin colored lines represent the selected models and the thick blue lines show the multi-model ensemble mean of the selected models) and via the constrained estimation method (thick black lines) for the global ocean and the three regional oceans (equatorial Pacific Ocean, North Atlantic Ocean and Southern Ocean).