Climate models predict that tropical precipitation will increase under global warming, but the extent of increase in annual mean precipitation keeps uncertain. Geochemical proxies provide long-term hydroclimatic records in tropics, but the quantitative calibration of these records to annual mean precipitation keeps unsolved, as the climatic information recorded in paleoclimate proxies can vary seasonally, leading to weak link to annual-mean climate changes. Here we quantitatively reconstructed the annual mean precipitation in the Asian-Australian monsoon domain (AAMD, 30S-30N and 65-125E) over the past 118,000 years from spatially separated cave records (Sanbao cave and Yangzi cave in central China), to understand the tropical precipitation dynamics at millennial and orbital scales. The difference in speleothem δ¹⁸O between two sites (Δ¹⁸O_YZ-SB) robustly responds to the annual average tropical precipitation (dynamic effect) in AAMD, while the seasonal effect of temperature and special humidity (thermodynamic effect) is offset. Since the last interglacial period, AAMD precipitation exhibit orbital and millennial scale variations, consistent with the Greenland ice core δ¹⁸O, with an average of 4.01 ± 0.09 mm/day. The annual mean precipitation during the last interglacial period (118.1-70.0 kaBP), the last glacial period (70.0-11.5 kaBP), and the Holocene (11.5-0 kaBP) was 4.06, 3.96, and 4.05 mm/day, respectively, close to the modern observed 4.00 mm/day (1979-2022, GPCP data), indicating that global warming has strengthened the tropical hydrological cycle, but the variation amplitude is relatively small.

annual mean precipitation, tropical monsoon, speleothem delta-18 O, glacial-interglacial period