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2,300-year climate record suggests severe tropical droughts as northern temperatures rise



A sediment core from a South American lake revealed a steady, sharp drop in crucial monsoon rainfall since 1900, leading to the driest conditions in 1,000 years as of 2007 and threatening tropical populations with water shortages, according to a team of researchers, which includes Donald Rodbell, chair of the Geology Department.

A 2,300-year climate record University of Pittsburgh researchers recovered from an Andes Mountains lake reveals that as temperatures in the Northern Hemisphere rise, the planet’s densely populated tropical regions will most likely experience severe water shortages as the crucial summer monsoons become drier. The Pitt team found that equatorial regions of South America already are receiving less rainfall than at any point in the past millennium.

The researchers report in the Proceedings of the National Academy of Sciences(PNAS) that a nearly 6-foot-long sediment core from Laguna Pumacocha in Peru contains the most detailed geochemical record of tropical climate fluctuations yet uncovered. The core shows pronounced dry and wet phases of the South American summer monsoons and corresponds with existing geological data of precipitation changes in the surrounding regions.

Rodbell was the co-designer of the study.

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