Extended Data Fig. 8: Drought attribution.
From: Rapid intensification of the emerging southwestern North American megadrought in 2020–2021
(a) Standardized anomalies (σ) of southwestern North American (SWNA) summer soil moisture calculated from (black) observed climate data and (turquoise) counterfactual climate data in which CMIP6 multimodel mean anthropogenic climate change (ACC) trends in temperature, relative humidity, and precipitation have been removed. (b) Same as (a) but the bold blue line shows the contribution of ACC, which is the bold black time series minus the bold turquoise time series in (a). Thin grey lines show results when the analysis is repeated removing climate trends simulated by each of the 29 CMIP6 individually (dotted blue lines show the interquartile values among the 29 grey time series). All standardization is relative to 800–2021, in which reconstructed values are used for 800–1900 and observation-based values are used for 1901–2021. Twenty-two year running means in (a) are displayed on the final year of each 22-year window.
