Carbon cycle: Carbon sinks

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Any process that absorbs carbon from the atmosphere is known as a carbon sink. There are large carbon sinks both in the oceans and on land, such as the absorption of carbon dioxide by plants and plankton during photosynthesis. Natural carbon sinks don’t change the total amount of carbon in the atmosphere, because over timescales of decades to centuries the amount of carbon absorbed from the atmosphere by natural sinks is balanced out by the amount added to the atmosphere by natural sources. Over the last 100 years or so, humans have released increasing amounts of carbon into the atmosphere. The ocean and land carbon sinks have responded by increasing the amount of carbon they absorb each year – compensating for about half of human greenhouse gas emissions. The other half has accumulated in the atmosphere.