Anthropogenic carbon dioxide that is not absorbed by sinks in the carbon cycle will remain in the atmosphere. The concentration of carbon dioxide in the atmosphere plays a crucial role in determining a significant portion of atmospheric warming due to greenhouse gases. Non-condensing greenhouse gases, including carbon dioxide, control the concentration of the most abundant greenhouse gas in the atmosphere: water vapour. You will learn more about water vapour feedbacks later in this lesson.

As the most abundant non-condensing greenhouse gas, carbon dioxide plays a vital role in the majority of climate regulating feedback cycles. For this reason, we can think of carbon dioxide as earth's thermostat. By increasing atmospheric carbon dioxide concentrations, human activity is tampering with the natural regulation of the carbon cycle, effectively increasing the set point of our climate's thermostat.

Question: In what ways does carbon dioxide act as a feedback and in what ways does it act as a forcing in the climate system?