Climate Science

Dueling Monsoons

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Science  01 Jul 2011:
Vol. 333, Issue 6038, pp. 14
DOI: 10.1126/science.333.6038.14-b

Stalagmites recovered from caves in southern and eastern Asia contain a remarkable chronicle of changes in rainfall over the course of the last glacial cycle, including millennial-scale warm intervals and more prolonged episodes of cooling called Heinrich events. The oxygen isotope record of those stalagmites has been interpreted as reflecting mostly the amount of East Asian summer monsoonal rainfall there. Things may not be quite what they seem, however, according to a report by Pausata et al., who use a climate model to assess the causes of the observed oxygen isotopic variations during a simulated Heinrich event. They found that Northern Hemispheric cooling during the event weakens the Indian monsoon and shifts water vapor enriched in 18O from India to China. Therefore, they conclude, Chinese stalagmite oxygen isotopes actually record changes in the Indian monsoon over thousand-year time scales.

Nat. Geosci. 4, 10.1038/NGEO1169 (2011).

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