Figure 2.

Diagram of ¹⁴C in the global carbon cycle showing the pools interacting with atmospheric CO₂ on the timescale of the Industrial Period. Typical ranges of Δ¹⁴C are shown for each of the pools. Global average Δ¹⁴CO₂ was approximately 15‰ in 2015 and 0‰ in 1850, whereas Δ¹⁴CO₂ in the troposphere was much higher in 1964–1965, 600‰ to 1,000‰ (Figure 3). In the shallow ocean, average Δ¹⁴C was approximately 5‰ in 2015 and −50‰ in 1850. Production of ¹⁴C occurs naturally through cosmic radiation and anthropogenically through nuclear activities. All ¹⁴C undergoes radioactive decay with a half‐life of 5,700 years.