Fig. 1: Map of cave locations, precipitation, surface relative humidity (%), and air temperature (°C).

a The precipitation amount is expressed as the difference between June through September (JJAS) and November through February (NDJF) from 1980 to 2010 in the western Pacific and East Asia, based on the data from the Global Precipitation Climatology Project (GPCP)75. b Annual surface relative humidity (1980-2010) and (c) annual air temperature (1991–2020) are based on the data from National Centers for Environmental Prediction/National Center for Atmospheric Research, NCEP/NCAR (https://www.esrl.noaa.gov)76. The site locations of the speleothem samples are in the Asian monsoon region (cave informations are listed in Supplementary Table 1). Blue and gray circles show cave sites: NB-Niubi Cave (112.58°E, 24.26°N, 174 m a.s.l.)77, SN-Shennong Cave (117.25°E, 28.70°N, 383 m a.s.l.)78, YQ-Yongquan Cave (115.65°E, 29.61°N, 100 m a.s.l.), SH-Shuanghe Cave (107.28°E, 28.25°N, 1170 m a.s.l.), LT-Longtan Cave (106.22°E, 28.22°N, 1230 m a.s.l.), FR-Furong Cave (107.90°E, 29.22°N, 480 m a.s.l.)79, LH-Lianhuan Cave (109.55°E, 29.15°N, 455 m a.s.l.)80, SB-Sanbao Cave (110.43°E, 31.67°N, 1900m a.s.l.)23, YXG-Yangxingui Cave (115.35°E, 29.68°N, 400 m a.s.l.), CJP-Cijiaping Cave (110.47°E, 31.76°N, 2000 m a.s.l.), QJ-Qujia Cave (118.42°E, 35.71°N, 456 m a.s.l.)81, ZJ-Zhangjia Cave (105.92°E, 32.51°N, 680 m a.s.l.), QF-Qianfo Cave (109.38°E, 33.23°N, 1500 m a.s.l.), DSY-Dongshiya Cave (111.57°E, 33.77°N, 840 m a.s.l.)82, JM-Jimao Cave (115.88°E, 39.81°N, 330 m a.s.l.), SHH-Shihua Cave (115.93°E, 39.78°N, 251 m a.s.l.)83, RG-Rige Cave (97.20°E, 32.22°N, 4252 m a.s.l.)84, TNL-Tham Nhong-Lha Cave (99.00°E, 9.10°N, 112 m a.s.l.), TSK-Tham Sing Khon Cave (99.04°E, 9.04°N, 106 m a.s.l.), LNT-Lin Noe Twin Cave (96.41°E, 21.24°N, 1220 m a.s.l.), ML-Mawmluh Cave (91.88°E, 25.26°N, 1160 m a.s.l.). The abbreviation of a.s.l. indicates above sea level. Dashed arrows depict wind directions of the Indian summer monsoon (ISM; white), East Asian summer monsoon (EASM; white), and the mid-latitude westerly (black).