Fig. 2: Timing of the first emergence (TFE) of consecutive unprecedented regional drought conditions (during the low-flow season).

a Timing of the first onset of consecutive exceedance for equal to or more than five years compared to the historical maximum value (TFE₅) under RCP2.6 and RCP8.5 in the 59 regions. The ensemble median results derived from the resampled time series are presented. Only regions in which the ensemble median TFE₅ obtained during the 21st century is statistically robust at the \(\pm\)5% level by the bootstrap test are shown in color (see Methods). Otherwise, regions are shown in gray. The hatched areas indicate robust TFE₅ signals; in these regions, more than 95% of the bootstrap ensemble members showed TFE₅ during the 21st century. b The cumulative distribution functions (CDFs) of TFE₅ occurrences under the two considered RCPs as a function of time, i.e., the likelihood of TFE₅ occurrence over time, in three regions with particularly robust TFE₅ signals concerning RCP8.5. The CDFs shown as solid lines are estimated from the entire resampled results. Considering the internal variabilities and original ensemble member spreads, the shading represents the uncertainty in the cumulative probability of TFE₅ estimated from resampled ensemble member subsets (see Methods). The cumulative probabilities of TFE₅ occurrence by 2050 and by the end of the 21st century are given in Supplementary Table 1. The same CDF plots for all regions with the median TFE₅ shown in color in a are presented in Supplementary Fig. 11. The regional definitions were derived following the HydroBASINS level-2 product⁴⁴ (Supplementary Fig. 3).