Over the past 800 thousand years, variations in the Earth’s orbit and tilt have caused antiphased solar insolation intensity in the Northern and Southern Hemispheres. Paradoxically, glacial records suggest that global ice sheets have responded synchronously to major cold glacial and warm interglacial episodes. To address this puzzle, we present a new detailed glacier chronology that estimates the timing of multiple Patagonian ice-sheet waxing and waning cycles over the past 300 thousand years.