Fig. 2: From annual ∆14C records to solar modulation.
From: Tracing ancient solar cycles with tree rings and radiocarbon in the first millennium BCE
a Annual ∆14C records with 2-σ error bars. Δ 14C (‰) denotes the decay corrected 14C/12C ratio of a sample relative to a standard and normalized for isotope fractionation. b Normalized 14C production rates relative to the steady state production rate of 6.6 kg/year calculated with a carbon cycle box model. c Reconstructed solar modulation parameter Φ from 14C production rates. The shaded bands indicate the uncertainty estimated by Monte Carlo simulations. d 50-yr low-pass-filtered Φ compared to existing reconstructions of solar modulation36,37. The two grand solar minima are indicated by the blue shaded areas and the Hallstatt-plateau is indicated by the red shaded area.
