Speleothem CaCO δ O is a commonly employed paleomonsoon proxy. However, inferring local rainfall amount from speleothem δ O can be complicated due to changing source water δ O, temperature effects, and rainout over the moisture transport path. These complications are addressed using δ O of planktonic foraminiferal CaCO , offshore from the Yangtze River Valley (YRV). The advantage is that the effects of global seawater δ O and local temperature changes can be quantitatively removed, yielding a record of local seawater δ O, a proxy that responds primarily to dilution by local precipitation and runoff. Whereas YRV speleothem δ O is dominated by precession-band (23 ky) cyclicity, local seawater δ O is dominated by eccentricity (100 ky) and obliquity (41 ky) cycles, with almost no precession-scale variance. These results, consistent with records outside the YRV, suggest that East Asian monsoon rainfall is more sensitive to greenhouse gas and high-latitude ice sheet forcing than to direct insolation forcing.