• Nitrogen is the main component of the atmosphere, a key nutrient for organisms, and exerts con- trol over climate via direct warming, as N2O, and indirect effects, including pressure-broadening • Previous models linked N to C, and typically only considered biologic or geologic fluxes in detail, focusing on sedimentary rocks. These studies suggest atmospheric mass steady over Earth history, which does not match new geochemical and physical paleobarometers • New approach is to more completely include biologic and geologic fluxes, and link N behavior to PO4 and O2 abundance through time • This approach is consistent with large-scale changes in atmospheric mass through time, up to 3 present atmospheric masses of nitrogen (1 PAN = 4 × 10^18 kg N) supporting geochemical proxies that indicate atmospheric drawdown through time