deposits in Sanbao cave in Central China tell the story of the region's climate more than 200,000 years ago. They also reveal the working of the East Asian monsoon over timescales that range over thousands of years. The information was brought out in a paper in the February 28 issue of Nature.

But the significance of the paper extends beyond caves and monsoons. The rainfall patterns revealed by the study provide evidence for a bold hypothesis about climate change: wobbles in the earth passage round the sun are a prime mover of long-term monsoon variations.

As the Earth moves around the Sun, its orbital eccentricity