Carbon sink
An environment, such as a forest or the ocean, that absorbs and stores more carbon than it releases over some period of time, which helps to offset greenhouse gas emissions.

Density
The number of organisms per unit of space.

Decomposition
The process of mechanically or chemically breaking down dead material.

Cyrosphere
The frozen water part of the Earth system, including areas with snow, glaciers, sea ice, and frozen earth.

Conservation
The use of natural resources in a way that assures their continuing availability to future generations; the intelligent use of natural resources for long-term benefits.

Conifer
A plant that bears its seeds in cones. Usually refers to NEEDLELEAF trees, although some needleleaf trees, such as the yew, do not bear cones.

Climatologist
A person who is expert in climatology, the study of long-term weather trends.

Climate
The kind of weather a place has over a period of years, based on conditions of heat and cold, moisture and dryness, clearness and cloudiness, wind and calm.

Claim
A concluding statement that answers a research question.

Carbon source
A carbon pool that releases more carbon than it absorbs over some period of time. Examples include the burning of fossil fuels, forest fires, and livestock.