Billy did you see this doc on Nova:
http://www.pbs.org/wgbh/nova/cavedive/
There was a really interesting finding in those caves from stalagmite that showed a increase in Sahara sand in the layer right before major climate shifts, showing that it was a consistent sign of an upcoming climate change
Now having said that they suggested that we've seen a big rise in Sahara sand in the last few decades hinting that we have reason to worry that this is a real sign of an upcoming dramatic climate shift.
Quote:
NARRATOR: At 150 feet, Brian and Kenny transit a series of rooms girded by stalagmites. These mineral formations grow from the ground up. Some in this cave took more than 200,000 years to form.
It started in a dry cave, when water percolated through the ceiling and fell in different spots. Stalagmites are built by the slow accumulation of the minerals and sediments contained in the water. So these beautiful columns are more than geological ornaments. Locked inside is a biography of Earth and its atmosphere.
The stalagmites Brian and Kenny are harvesting may help answer critical questions about the history of Earth's climate. That's what geo-chemist Peter Swart wants to know about.
At the end of the last Ice Age, about 11,000 years ago, conditions changed radically, from dry to wet, within 50 years. This change was probably accompanied by a rise in temperature and sea level.
And Swart notices something else: some of these climate events are preceded by a mysterious dark band. When he samples the dark bands, he finds iron.
So is there some link between iron and climate change? How could that be? The Bahamas are made of coral; there's no iron anywhere.
In the blue hole where they cut the stalagmite, Brian and Kenny noticed something that might help solve the mystery. In the cave wall, they found a layer of red sediment. The color is the key here: the red in the dust means it's loaded with iron. And that means that thousands of years ago, a thick layer of iron-rich red dust covered the island's surface.
Repeated rains washed it through the rock, leaving a bright red band.
So how did the red dust get here? One theory suggests it came from the Sahara Desert, some 4,000 miles away.
NARRATOR: The areas with the highest concentration of iron correspond almost exactly to the places on the stalagmite where the chemical composition indicates a period of major climate change.
That probably means a major Sahara dust event came right before each change, when temperatures and sea levels rose.
The fact that Saharan dust storms happen with greater frequency today is raising concerns that history could be repeating itself.
PETER SWART: Now, we know, for the last 40, 50 years, there's been a major drought in Africa. And that has seen an input in the amount of dust which is coming from the Sahara region to the Bahamas.
NARRATOR: It's estimated that over the past five decades, the Sahara has seen a ten-fold increase in large-scale dust storms. If we are witnessing the beginning of a major climate change, it could happen fast, just as it happened in the past, maybe in as little as a lifetime.
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http://www.pbs.org/wgbh/nova/transcr..._cavedive.html