Extended Data Fig. 10: Future drought trajectories.

Simulated future trajectories of the turn-of-the-21^st-century drought by extending the observed 2000–2021 record of southwestern North American soil moisture anomalies for 40 additional years (2022–2061) with each of the 1,183 40-year sequences from 800–2021. In both cases, when 2022–2061 soil moistures were replaced with 40-year soil moisture samples from within the observed period (1901–2021), we used soil moistures calculated after the removal of CMIP6 anthropogenic climate change (ACC) trends. In (a), 2022–2061 soil moisture anomalies were artificially dried by the 5-year mean ACC effect during 2017–2021 (−0.46 σ), representing a world in which the future drying effect from ACC is held at its 2017–2021 mean. In (b), no such adjustment to represent ACC drying is made, representing a future in which ACC has no effect. In both panels, the axis on the left corresponds to the red observed time series of cumulative soil moisture anomaly as well as the gridded percentages of the 1,183 simulations that result in a given cumulative soil moisture anomaly in a given year. The axis on the right corresponds to the black-and-white time series of the probability that the turn-of-the-21^st-century drought survives to each year from 1 to 62. The vertical black dotted line identifies year 23, the duration of the shortest of the reconstructed megadroughts, and the horizontal black dotted line indicates the probability (P(drought)) that the turn-of-the-21^st-century drought continues through a 23^rd year. Determination of drought termination is made following the methods described in the Methods section.