FOR IMMEDIATE RELEASE
Contact: Nicole Russell
Data showing the amounts of rainfall in east Africa over the past 1,100 years are available from NOAA's National Geophysical Data Center in Boulder, Colo. The data were from sediment and fossils taken from a lake in Kenya. They were used to provide information about what the climate was like then.
The sources, from Lake Naivasha in Kenya, include sediment and fossils. Using these and other sources, scientists determined that over the past millennium, the climate in equatorial east Africa has alternated between drier than today, and relatively wet. The drier climate took place during the Medieval Warm Period (~AD 1000-1270); the relatively wet climate during the Little Ice Age (~AD 1270-1850). The Little Ice Age was interrupted by three prolonged dry episodes.
The droughts during the Little Ice Age wreaked havoc on the region, said Bruce Bauer data manager for the Paleoclimatology and NOAA Paleoclimatology Program of NGDC. "Each of the dry episodes was more severe than any recorded in the 20th century," he said. "Oral histories recount famine, human migrations, and political unrest coinciding with the reconstructed drought intervalswhile population growth and political stability occurred during the wetter periods."
Data collected from the lake are especially important because other forms of proxy data are scarce in the area. There are only a limited number of natural records from tree rings and ice cores, and there is a lack of long-term instrumental records. Having knowledge of natural long-term rainfall variability is essential for water-resource and land-use management.
This project is a collaboration among researchers at NGDC, the University of Minnesota, the University of Gent in Belgium, and Queens University in Canada.
Note to Editors: Data from the study are available at: http://www.ngdc.noaa.gov/paleo/data.html