What would lead to an increase in carbon dioxide in the atmosphere?

Continuing to burn fossil fuels (coal, oil and natural gas) would lead to an increase in carbon dioxide levelsbecause we are adding long-buried carbon to the atmosphere and the carbon cycle is unable to cope with this extra amount.

Natural sources of atmospheric carbon dioxide include volcanic outgassing, the combustion of organic matter, and the respiration processes of living aerobic organisms.

Man-made sources of carbon dioxide include the burning of fossil fuels for heating, power generation and transport, as well as some industrial processes such as cement making.