Figure 3: Estimated uncertainties on paleointensity data used to constrain the Levantine geomagnetic spike.

(a) Black circles give age uncertainty estimates, σ_age, for 4,128 paleointensity estimates spanning the interval 0–10 ka used in the construction of the CALS10k.2 Holocene field model⁹ as described in the text. Green circles highlight the 143 data lying in the interval 1150–850 BC. Red circles mark estimates associated with the peak value at each of the 23 sites used in Fig. 4. (b) Black, green and red symbols as in the upper panel but now showing σ_lab. Blue circles show σ_t, which incorporates uncertainty effects arising from dating (σ_age) and age bias Δ arising from the discrepancy in the assigned age relative to the date of the Levantine spike, taken here to be 1000 BC (Methods). The total uncertainty is , with the rate of intensity change ∂F/∂t taken to be 0.15 μT yr⁻¹.