The drought hit almost all of southern Asia and most of the African continent. During the drought, Africa's Lake Victoria — the world’s largest tropical lake and the source of the Nile — dried out, as did Lake Tana in Ethiopia and Lake Van in Turkey.
By looking at climate records, including samples of ancient sediments taken from Lake Victoria and Lake Tanganyika in Tanzania, the researchers pegged the timing of the megadrought to the peak of a 3,000-year period when icebergs and their meltwater surged into the North Atlantic. This fresh water discharge in the North Atlantic ocean, which occurred as the last ice age came to a close, had also an impact at the tropical latitudes.
Unclear cause
The exact cause of the harshest megadrought in at least the past 50,000 years, however, remains unclear. Previous research points to a southward shift in the Intertropical Convergence Zone, i.e. the rain belt encircling the Earth between tropics and the equator. The southern shift would have starved the region of rainfall. However, evidence collected in this study suggests that such a shift could not explain the extension of the drought.
They suggest, that in addition to the convergence-zone move, the tropical rainfall systems over Africa and Asia must have weakened dramatically, perhaps in response to cooling sea surface and less water evaporating off it.