Carbon that is not released into the atmosphere and is, instead, sequestered by a tree or some other type of biomass, is said to be in carbon storage. Carbon sinks increase the size of the carbon storage. Carbon storages are everywhere in our natural environment – for example, the soil and forests are significant carbon storages.
In the natural cycle of carbon, plants capture carbon from the atmosphere and release some of it back as they decompose – part of the carbon they have captured will be stored in the soil. This means that carbon is not necessarily permanently stored, and many carbon storages are susceptible to rapid changes: once captured, carbon is not “safe” and can be released back into the atmosphere. If a carbon storage, such as a forest, is allowed to grow, it is able to capture more carbon than it releases, which makes is a carbon sink.
To achieve the 1.5 degree target as specified in the Paris Agreement, all fossil fuel emissions should stop and carbon should be sequestered from the atmosphere back into carbon storages (see carbon sink and carbon negativity).