Carbon cycle: Carbon sinks    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.