Carbon dioxide isn't stuck in the atmosphere once it gets there. It moves into and out of living organisms, soil, rock, and water. For example, plants take up carbon dioxide in the air to make wood, stems, and leaves, and then release it back into the air when the leaves fall or the plants die. Forest fires release large amounts of CO₂, providing an important reason to preserve forests. Animals, including humans, take up carbon when they eat plants, and then release CO₂ back into the atmosphere via respiration.

Over very long time frames, the weathering of rocks can add carbon to surface waters that run into the ocean. Eventually, this carbon is removed from the water and forms limestone. It can later be released back into the atmosphere from volcanoes when the rock is melted.

In ancient times when Earth had a much warmer climate, huge swamps buried plant material faster than it could decay, and when the buried remains were subjected to heat and pressure, they became coal. In similar ways, microorganisms buried on lake and sea bottoms throughout Earth's history produced oil. These processes locked up lots of carbon as oil, gas, and coal. By burning these fuels in the last 150 years, we have suddenly released into the atmosphere carbon that took hundreds of millions of years to store.