Extended Data Fig. 6: Modern Instrument-derived self-calibrating Palmer Drought Series Index (scPDSI) values and correlations ad 1901–2012 for January-August for central Anatolia from the Old World Drought Atlas (OWDA)58.
From: Severe multi-year drought coincident with Hittite collapse around 1198–1196 bc
a, Comparison of a west-east transect across the core Hittite region in central Anatolia from Polatlı (39.58N, 32.14E) to Kirikkale (39.85N, 33.5E) to Boğazkale (40.02N, 34.61E) (location of Hattusa) to Sivas (39.75N, 37.02E) and for a major center to the southeast (Kayseri) (38.72N, 35.48E) (see Extended Data Fig. 1). The scPDSI series from Polatlı has Pearson correlation coefficients (r) = 0.78, 0.7, 0.48, and 0.6 respectively; thus positive and suggesting a general regional pattern, except for Sivas in the east. b, Critically, the one extreme drought event in the dataset, centered 1928, occurs as a < scPDSI -4 event across all five loci, and c., is reconstructed across the entirety of central Anatolia, suggesting that extreme arid events recorded at Polatlı are likely regionally effective (see also Fig. 3 and Extended Data Fig. 7).
