Reconstructing the history of tropical hydroclimates has been difficult, particularly for the Amazon basin—one of Earth’s major centres of deep atmospheric convection. For example, whether the Amazon basin was substantially drier or remained wet during glacial times has been controversial, largely because most study sites have been located on the periphery of the basin, and because interpretations can be complicated by sediment preservation, uncertainties in chronology, and topographical setting.

What caused the series of more than 20 ice ages that have come and gone during the past 2 million years of Earth history? On page 860 of this issue, Dorale et al. (1) reveal a new twist in the most recent ice age cycle and demonstrate once again the rapidity with which large ice sheets can come and go.

²³⁰Th-dated oxygen isotope records of stalagmites from SanbaoCave, China, characterize Asian Monsoon (AM) precipitation throughthe ends of the third- and fourthmost recent ice ages.

High-resolution speleothem records from China have provided insights into the factors that control the strength of the East Asian monsoon.