Question

What role does the combustion of fossil fuels have in the carbon cycle?

Answer 1

They release sequestred carbon.into the atmosphere making it available for uptake by plants.

Explanation:

The carbon cycle is the process by which carbon (in the form of various compounds) is released into the atmosphere from where it is taken up into living tissue by plants and hence enters the food chain.

This carbon in living organisms is released back into the atmosphere through processes such as respiration, death and decay, and combustion (including that of fossil fuels).

The flip side is that fossil fuels comprise carbon sequestred naturally over billions of years that enabled Earth to develop into a planet that could support life with an atmosphere of largely `N_2` and `O_2`. So the combustion of fossil fuels combined with severe deforestation and depletion of oceanic species is causing an overload of `CO_2` in the atmosphere.