Evolution of carbon sinks in a changing climate

This new research, conducted using computer models, shows that there may be an inverse link between anthropogenic carbon dioxide emissions and the ability of the earth to sequester, or absorb, the excess CO2.

The authors focus primarily on the global carbon–climate feedbacks and the biogeochemical mechanisms that amplify or diminish physical climate change. These include the attributes and functions of things such as plants, bacteria, soil, rain and oceans.

Climate change is expected to influence the capacities of carbon sinks to act as repositories for anthropogenic carbon dioxide and hence provide a feedback to climate change. Using a coupled carbon-climate model, the authors find that the capacity of carbon sinks strengths vary with the rate of fossil fuel emissions, meaning that carbon storage capacities of the land and oceans decrease and climate warming accelerates with faster carbon dioxide emissions. In the oceans, rising sea temperatures increases stratification of the water column and inhibits mixing of the layers, meaning absorbed carbon dioxide is less able to leak to the bottom and remain sequestered. On land, the model indicates that tropical areas in particular are prone to drying, hindering plant growth and reducing carbon uptake through photosynthesis.

The authors also find there is a positive feedback between the carbon and climate systems, so that climate warming acts to increase the airborne fraction of anthropogenic CO2 and amplify the climate change itself. However, on a global scale the model indicates that this amplification is small at the end of the 21st century.

Comparing the results of this study to other similar models suggests that negative impacts on the tropical land sink (such as ecosystem changes) are likely, although the degree is uncertain.