Carbon Dioxide composes about 0.04% of the atmosphere. It is not famous for being a large component of the atmosphere by volume (it's not) but rather by being a very effective greenhouse gas and being part of the Carbon cycle. Carbon Dioxide is composed of a Carbon atom and two Oxygen atoms (CO2). Plants use this gas in the photosynthesis process and animals use its components that become part of sugar molecules. Animals breathe out this gas in the respiration process. As Carbon based life forms, Carbon Dioxide is a critical component for life. The Carbon in Carbon Dioxide is used in sugar molecules and this sugar is used for energy and other functions in living organisms.

Carbon Dioxide is a greenhouse gas. It is effective at absorbing and emitted longwave radiation. This helps traps extra energy in the lower atmosphere and causes the Earth’s atmosphere to be warmer than it otherwise would be. As Carbon Dioxide increases, then more energy can be trapped and surface temperature will warm. This is the concern involved in the global warming debate. The emissions of CO2 in the atmosphere contribute to increased greenhouse warming. Even with the small amount of CO2 in the atmosphere, significant greenhouse warning occurs. The concern is that even small increases in CO2 can cause significant global temperature increases.