Fig. 4: Comparison between Asian summer monsoon/South American summer monsoon and ice-core records.

a Cherrapunji δ¹⁸O record (this study) from Cherrapunji Cave in the ISM domain, b Antarctica WDC ice-core CH₄ record²⁴, c MAG δ¹⁸O record (this study) from Marota Cave in the SASM domain, d Antarctic ice-core composite Δε_LAND proxy⁷¹, e Greenland NEEM ice-core δ¹⁸O record (Supplementary Note 1.5) on the improved chronology (GICC05 timescale +320 years)(see main text), f, g are Antarctic ice-core δ¹⁸O records from WDC¹³ and EDML⁹⁵, respectively. Antarctic ice-core records are plotted on the WD2014 chronology⁶³, which is shifted by +400 years via a correlation based on the volcanic triplet spike (depicted by the orange diamond and the vertical bar at ~24.94 ky BP). It is noted that the EDML δ¹⁸O record has been tuned to the WD2014 chronology in a previous study¹⁶. Red dots and associated error bars in (e) and (f) indicate the timing and combined uncertainties (2σ) of the change points in Greenland and Antarctic ice-core δ¹⁸O records (Supplementary Table 2). The Brown error bar depicts the ¹⁴C age⁶⁶ and uncertainty (1σ) of the Oruanui eruption from the Taupo volcano. The vertical bar at ~25.72 ky BP marks the tephra layer of the Oruanui eruption recorded in the WDC ice core⁶⁴. The two vertical dashed lines depict the DO-2.1 and DO-2.2 peaks. Cave, ice-core and volcano locations are shown in Supplementary Fig. 2. Vertical bars are the same as in Fig. 2. AIM Antarctic isotope maximum⁹⁵, ppb parts per billion, ISM Indian summer monsoon, SASM South American summer monsoon.