Climate Science

Penultimate Monsoons

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Science  17 Mar 2006:
Vol. 311, Issue 5767, pp. 1523
DOI: 10.1126/science.311.5767.1523c

Analysis of stalagmites has provided remarkably detailed records of precipitation patterns and particularly of changes in monsoonal rainfall. Some stalagmites have been used to chronicle variations of the Asian monsoon for most of the past 160,000 years, revealing close connections between these variations and regional climate behavior in distant locations. The data also help to deepen understanding of how climate dynamics have operated in the past.

Cheng et al. add to this body of knowledge with a record of oxygen isotopes from three stalagmites in Hulu Cave, China, characterizing most of the interval between 128,000 and 178,000 years ago. Most of the penultimate deglaciation period—during which atmospheric CO2 concentration rose and much of the accompanying rise in atmospheric methane took place—occurred during a time of weak Asian monsoons, when the high northern latitudes likely were cold. Thus, the penultimate deglaciation seems to have been a two-phase process driven by orbital forcing in both hemispheres. — HJS

Geology 34, 217 (2006).

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