Extended Data Fig. 7: Comparison of Δ36 values in measurements of ice-core, firn and modern air.
From: Isotopic constraint on the twentieth-century increase in tropospheric ozone
a, Firn and ice-core Δ36 values (means of replicates) plotted against mean gas age. b, Kernel-smoothed probability density distributions of bootstrap-resampled mean values of each dataset, showing a significant (P < 0.002) difference between the means of the ice-core and firn (above 105 m) datasets. Uncertainties are omitted for clarity. Pooled standard deviations for each sample type are 0.03‰–0.04‰ (see Methods). C.E., common era.
