An extended yardstick for climate variability

Decoded and precisely dated information encrypted in stalagmites from a cave in China reveal past climatic changes and provide insight into the complex interactions in today's climate system. See Letter p.640 A 640,000-year record of the Asian monsoon Prior records of the Asian monsoon have revealed cyclic variations over hundreds of thousands of years, probably driven by variations in insolation caused by the precession of Earth's orbit. Hai Cheng and colleagues now provide a speleothem record from Chinese cave samples that extends earlier records to 640,000 years ago, close to the maximum age possible with uranium/thorium dating. This spectacular record confirms that the characteristic '100,000-year' ice age cycle corresponds to an integral number (four or five) of precession cycles, and that insolation influences millennial-scale variations in monsoon strength.