the capacities of the land and oceans to act as repositories for anthropogenic carbon dioxide (co₂) may be limited if we maintain or accelerate our current course of fossil fuel emissions, according to a us study.

Using a new generation computer carbon-climate model, the study conducted at Berkeley University shows carbon sink strengths vary with the rate of fossil fuel emissions, so that carbon storage capacities of the land and oceans decrease and climate warming accelerates with faster co₂ emissions. The co₂ absorption rate in plants is limited by their metabolic reactions, by water and nutrient availability. Increasing temperatures and drought frequencies also lower plant uptake of co₂ as plants breathe in less to conserve water.

In the oceans, mixing by turbulence is essential for moving co₂ down into the deep ocean. Carbon absorption takes place in the top 100 metres. When temperatures increase, mixing becomes harder as the oceans stratify more, and the co₂ accumulates in the surface ocean. This accumulation saturates the top layer, lowering co₂ absorption. The findings were published in the Proceedings of the National Academy of Sciences (Vol 102, No 32, August 9).