Lake Victoria, photo: Marc Veraart/Creative Commons
Take this next one as a sign of how dry the climate has gotten and could get, not a specific prediction, projection or anything like that: New research published in Science shows how dry things got in a massive megadrought that spanned Africa and southern Asia between 15,000-18,000 years ago and details what may have caused it. The scale of it is pretty crazy.At the time of what's known as the H1 megadrought (get this...) Lake Victoria, the world's current largest tropical lake, dried up. Lake Tana in Ethiopia in did too, as did Turkey's Lake Van. Lake Victoria has an average depth of 130 ft, dropping off to 272 ft; it covers about 26,600 square miles... and it dried up. It stayed dried out for about 2600 years. At the same time the Nile, Congo and other major rivers shrank, the summer monsoon failed from China to the Mediterranean. It was one of the most intense droughts of the past 50,000 years.
Lake Van, photo: Wikipedia
Now I don't want to sound too breathless here. There have certainly been plenty of dramatic changes to the world's coastlines, islands (coming and going), lakes, rivers, forests and wetlands over than past several millennia, let alone on a geologic time scale. But listen to what this new research links to the the H1 megadrought, even if we still don't know specifically what caused it.
Its timing suggests a link to Heinrich Event 1, a massive surge of icebergs and meltwater into the North Atlantic at the close of the last ice age. Previous studies had implicated southward drift of the tropical rain belt as a localized cause, but the broad geographic coverage in this study paints a more nuanced picture.
"If southward drift were the only cause," says Stager, 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." (Science Daily)
Lake Tana, photo: Marc Veraart/Creative Commons
The part about a massive surge of meltwater in the Atlantic, could it happen again? It could, but the paper's authors say that because there is so much less ice now remaining to collapse it would be surprising if it could happen again, "at least on such a huge scale."
Which isn't to say the implications for sea level rise of the Greenland ice sheet collapsing aren't real, just that Lake Victoria won't dry up because of it like it did 17,000 years ago.
Read the original research: Catastrophic Drought in the Afro-Asian Monsoon Region During Heinrich Event 1
More on Global Climate Change:
Global Warming to Blame for 37% of Droughts
Drought Uncovers City Submerged for Decades
Drought Could Overtake the World by 2030, Rise to Unprecedented Levels by 2100