Carbon dioxide, commonly known as CO₂, is a gas with many faces. It is a vital ingredient in photosynthesis—the process that plants use to make food. It also blankets the Earth, keeping our planet warm enough to sustain life.
But too much carbon dioxide in the atmosphere can keep the Earth too warm and cause extreme weather patterns like floods and droughts.
How much CO₂ is out there? This line graph tracks the level of CO₂ in the atmosphere over 400,000 years. The level of CO₂ is measured in parts per million, or ppm. (1 ppm means for every million pound of gas, there’s 1 pound of CO₂.)