Fig. 2: Trends in drought magnitude and frequency for 6-month SPEI during 1981–2022.
a,b, The trend in magnitude (z-units yr−1; a) and frequency (months yr−1; b) of droughts (SPEI < −1) for the period 1981–2022 based on observed precipitation and AED (‘Observed’). c,d, The trend in magnitude (c) and frequency (d) based on observed precipitation and AEDclm (‘AEDclm’). e,f, The difference in trend between observed precipitation and AEDclm for drought magnitude (e) and frequency (f). The SPEI is based on MSWEP_hPET. The trend and regional average exclude dry land areas with average annual rainfall below 180 mm. Non-significant trends (P > 0.05) are marked in grey to enhance clarity. Magnitude is calculated as the cumulative sum of SPEI < −1 values during a drought event for each year and frequency represents the number of events in a year with SPEI < −1. g–r, The average magnitude (units yr−1; g–i) and frequency (months yr−1; m–r) of droughts averaged over South America (g,m), Africa (h,n), Australia (i,o), Europe (j,p), Asia (k,q) and North America (l,r).
