Extended Data Fig. 6: Statistically significant increases in dry and wet local deviation frequency, separately for DJF and JJA months.

Panels show increases in dry and wet local deviation frequency for streamflow (a, b) and for soil moisture (c, d), during DJF months (a, c) and JJA months (b, d). Changes in the frequency of local deviations are computed by comparing the ensemble median frequency of local deviations during the DJF/JJA months in 1976–2005 against the DJF/JJA months in 1691–1860, and significance of change is tested at a 95% confidence level (P = 0.05) with R package stats function prop.test⁹⁶ (one-sided test). Colours denoted with + indicate statistically significant increases with magnitude ≤5 pp (minor), whereas colours denoted with ++ indicate statistically significant increases with magnitude >5 pp (major). Colours denoted with +(+) pool together any statistically significant increase (minor or major). It should be noted that because the sample size for testing statistical significance of local deviation frequency here is smaller (510 pre-industrial months & 90 industrial months) than in analyses with all months (Fig. 3, Extended Data Figs. 5, 7; 2040 & 360 months), significant changes classified as minor are rare. However, for consistency, we retain the same categorisation for minor and major increases.