http://www.canadafreepress.com/index.php/article/45199
Africa: The Next Megadrought
Author
- Dennis Avery Monday, March 12, 2012
Africa is suffering serious drought again—in both the Horn of Africa
(Somalia, Ethiopia, and Kenya) and in West Africa’s Mali. How bad is
the drought likely to get, Lake Bosumtwi, Little Ice Age,
Three years ago, the New York Times reported a study of the lakebed
sediments in Ghana’s Lake Bosumtwi. Lead author Tim Shanahan of the
University of Texas said Africa gets serious drought every 30 to 65
years—but “changing Atlantic sea-surface temperatures” are capable of
triggering “much longer and more severe future droughts.”
The Bosumtwi mud revealed a West African megadrought during the Little
Ice Age that lasted from 1400 to 1750! The trunks of ancient dead
trees now submerged in deep water show the lake lost four times as
much water in the Little Ice Age as in the severe Sahel droughts of
the ‘70’s. Meanwhile, Africa’s population has expanded from 110
million to 1 billion in the intervening centuries.
It gets worse. In East Africa, Karl Butzer of Switzerland found long
wet-dry cycles in Ethiopian valley sediments during the “little ice
age” called the Dark Ages. The culture collapsed in AD 600 and did not
re-emerge until more than 600 years later.
Fast forward to 2011 when University of Washington’s oceanographer
Julian Sachs’ article, “A Shifting Band of Rain” appeared in
Scientific American. He studied the Intertropical Convergence Zone,
the tropical rainbelts near the equator. Lakebed sediments across a
whole north-south range of Pacific islands show him that the tropical
rains have moved north 550 km in the years since the Lake Bosumtwi
megadrought.
Sachs predicts the rain belt could move another 550 km north in the
centuries ahead, as the Modern Warming continues. The Mexican desert
could come to the southern U.S. The rains that now support farming in
Ghana and Ethiopia could move north to the Sahara and North Africa, as
they did during the Roman Warming (200 BC–AD 600). The Roman Empire
fed itself on grain from then-wetter North Africa and Egypt—while
Ghanaians and Ethiopians starved or moved. Came the Dark Ages and the
ITCZ moved south again, while both North African and Egyptian cultures
collapsed for centuries.
Shanahan is describing the effects of the 1,500-year
Dansgaard-Oeschger cycle, discovered in the Greenland ice cores in
1984. He referred to “changing North Atlantic sea-surface
temperatures”—but he’s really talking about a solar-driven cycle that
has produced more than 500 global warmings and “little ice ages” in
the past million years. Our study of paleoclimate proxies is only now
getting good enough to show us the drastic climate consequences of the
shifting rain belts.
Is Africa starting the next megadrought now? I think that unlikely.
We’re only 150 years into the Modern Warming and even the short
Medieval Warming lasted 350 years. It is more likely a repeat of the
1970s “serious drought” that cost 100,000 lives.
What will the world do when the tropical rains leave sub-Saharan
Africa sometime in the centuries ahead for several hundred years,
leaving behind many millions of Africans who will not be able to walk
to sustainability? Ditto for Latin America. Where would we put them
and how would we get them there?
Human numbers will be declining naturally after 2050—but mid-Africa’s
population may double before it stabilizes. Organic or traditional
primitive farming won’t feed them, or protect Africa’s unique wild
species from the stew pots of the starving.
During the famines of the Little Ice Age, human ingenuity produced the
gang plow to crop the heavy, rich soils of the valleys that had defied
earlier plows. “New” crops brought by Spanish ships from the New World
included the potato, the tomato, maize and sweet potatoes—radically
increasing food yields per acre for both Europe and Africa. Industrial
nitrogen fertilizer is currently feeding 5.5 billion of our fellow
humans. We’ll need all our inventiveness and our persistence to adapt
in the earth’s future droughts; and enlightened consensus to then
accept the technology.
Sources:
T. Shanahan et al, “Atlantic Forcing of Persistent Drought in West
Africa,” Science 324 (2009): 377–380.
Karl Butzer, “Paleoenvironmental Changes during the Last 4000 yr in
the Tigray, Northern Ethiopia,” Quaternary Research 49 (1998):
312–321.
Julian Sachs and Conor Myrdahl, “A Shifting Band of Rain,” Scientific
American, (March, 2011): 60–65.
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Received on Mon Mar 12 2012 - 23:06:00 EDT
