AI Tutor
Every time you exhale, you release carbon atoms that might have once lived inside a leaf, a prehistoric fern, or deep at the bottom of the ocean.
Earth holds a fixed amount of carbon, but it is constantly moving between giant storage zones called reservoirs (or sinks).
To measure these planetary quantities, scientists use the gigaton of carbon (abbreviated as GtC), where one gigaton equals one billion metric tons.
If thousands of gigatons of carbon are locked away in rock and water, how does any of it actually reach the air we breathe?

Flux: Tracking Carbon on the Move

A flux is the rate at which carbon transfers from one reservoir to another over a specific amount of time, usually measured in GtC per year.
On land, total photosynthetic uptake—known as Gross Primary Productivity—pulls roughly 120 Gt C/yr120\text{ Gt C/yr} from the atmosphere into terrestrial ecosystems.
Simultaneously, autotrophic respiration by plants alongside heterotrophic respiration and decay release ∼120 Gt C/yr\sim 120\text{ Gt C/yr} back into the air, creating a near-balanced natural sub-cycle.
When the downward flux matches the upward flux, the system is in dynamic equilibrium — carbon moves rapidly, but reservoir sizes stay steady.
What happens when we suddenly introduce a brand-new one-way pipeline into this balanced cycle?

Quantifying the Human Flux