A new monsoon record

Scientists toiling to understand past climate change and predict future trends now have a high-resolution, absolute-dated record of the strength of the East Asian monsoon. Presented in Nature this week, the record or ‘speleothem’, taken from 12 stalagmites in Sanbao cave of central China, stretches back some 224,000 years.

Completing a Chinese-cave based record of monsoon history over the past two interglacial–glacial cycles, the record shows that the monsoon responds directly to Northern Hemisphere summer solar radiation on orbital timescales. It also indicates that the duration and pacing of so-called ‘Chinese interstadials’— millennial-scale strong-monsoon events—are affected by ice sheet size.

A team of scientists in China and the US, led by Hai Cheng of Nanjing Normal University and the University of Minnesota, produced the oxygen isotope speleothem that may also serve as a benchmark for correlating other climate records.

Speleothems are relatively new proxies of past climate change compared with tree-rings, sediments, ice cores and corals that also record the ratios of different oxygen and carbon isotopes in material laid down over time. These proxies can all be used to track changes over time in factors such as rainfall, temperature and vegetation.