Published on February 25th, 2011 | by Joshua S Hill
Ancient Megadrought Asks Big Questions for Future
With scientists unsure as to the endgame of the current climate change affecting our planet, one big question is always on peoples’ lips; how severe can climate change get?
According to the results of a study published in the latest edition of the journal Science, the answer is not good.
An international team of scientists compiled 48 paleoclimate records from sediment cores extracted from Lake Tanganyika and other locations in Africa, and found that one of the most widespread and intense droughts of the last 50,000 years struck Africa and Southern Asia between 17,000 and 16,000 years ago.
“The height of this time period coincided with one of the most extreme megadroughts of the last 50,000 years in the Afro-Asian monsoon region with potentially serious consequences for the Paleolithic humans that lived there at the time,” says Paul Filmer, program director in the National Science Foundation’s (NSF) Division of Earth Sciences, which funded the research along with NSF’s Division of Atmospheric and Geospace Sciences and its Division of Ocean Sciences.
The time period in question saw large amounts of ice and meltwater entering the North Atlantic Ocean, causing regional cooling as well as major drought in the tropics, says Filmer, a drought now known as the H1 megadrought, which is one of the most sever climate trials ever faced by modern humans.
Effects of the drought saw the Lake Victoria, which is currently the world’s largest tropical lake, dry out entirely, as well as Lake Tana in Ethiopia and Lake Van in Turkey. The Nile, the Congo, and other major rivers shrunk dramatically in size, and Asian summer monsoons weakened or failed entirely from China to the Mediterranean, diminishing dramatically the rainfall in the region.
No one is quite sure exactly what caused the megadrougt, and climate models have yet to be able to simulate the full scope of the event, but scientists to suggest that it is linked to Heinrich Event 1, which took place approximately at the same time, and saw a massive surge of icebergs and meltwater make their way into the North Atlantic at the close of the last ice age.
Other hypotheses included a southward shift of the tropical rain belt as a localized cause, but the massive coverage of the megadrought suggests that this is too little to be the main cause.
“If southward drift were the only cause,” says Curt Stager of Paul Smith’s College, New York, lead author of the Science paper, “we’d have found evidence of wetting farther south. But the megadrought hit equatorial and southeastern Africa as well, so the rain belt didn’t just move–it also weakened.”
Source: National Science Foundation
Image Source: Curt Stager