In Part 2 of Skill 3: Energy Systems, you will learn what we need to do about shifting away from an unsustainable energy system. Part of this understanding includes the difference between carbon sinks and sources.
Anything that absorbs carbon from the atmosphere is called a carbon sink. The ground contains carbon, locked up in rocks and soil. Other carbon sinks include the ocean and plants.
The ocean absorbs roughly 70Gt of carbon a year, while plants absorb 120Gt of carbon annually. Plants and plankton absorb carbon via photosynthesis, which along with energy from the sun, is converted into sugars.