Posts Tagged ‘Milankovitch cycles’

Weathering Reinforced Orbital Glaciation Theory

January 15, 2019

I suggested that one could absorb CO2 by deliberately watering vast hot expanses of basalt and, or calcium or magnesium bearing tropical wastelands.
Friend Ian Miller pointed out in a comment that crushing rocks to achieve this required energy. I replied that, actually, I have seen immense expanses of desert in North America, South America, Mexico, Iran, Africa with such rock in a pulverulent form: no need to crush them, they are already completely crushed.

Then I remembered the Sahara, with thousands of kilometers of such pitiless desert. The highest mountain in the Sahara, as in Iran, is a volcano… But then I also remembered seeing prehistoric paintings there, of bucolic hunting scenes complete with hippopotamuses and trees… Imagine: that’s now an absolute desert: seeing one tree is seeing a miracle (one such tree is called “l’arbre du Tibesti”; it’s many thousands years old…).. Ah, but then, when the Sahara was wet, the watering, and the weathering, were achieved! CO2 was withdrawn from the atmosphere!

The white substance is natron, well-known to the Egyptians, in a giant caldera, the Trou au Natron, at the foot of an enormous shield volcano in Chad… In the middle of the Sahara. And not the largest volcano there. The cliffs are 1,000 meters tall. Yes, this all absorbs CO2 when wet…

So I suggest this: glaciations, in the last 2.75 million years were accentuated, reinforced by CO2 absorption from chemically interacting with rocks in the desert. Indeed, during glaciations, the giant circulation cells which create the arid subtropics are less aggressive and move south: the deserts become wet and green.

Now make no mistake: I am NOT saying that the orbital glaciation theory is false. I am just correcting it. I am adding a factor. The orbital theory of glaciation says that glaciations occur when it is too cold in July-August to melt snows in the Northern Hemisphere… where the continents mostly are (the southern equivalent is mostly ice-free: it’s an ocean, the “Roaring Forties”). The theory was first suggested by French mathematicians Joseph Alphonse Adhémar (1797–1862) who computed that ice ages were controlled by astronomical forces in his 1842 book Revolutions of the Sea. The idea is now associated with Milankovitch’s name. The theory’s recent Computer simulations show that this is (roughly) correct… Although various sticky mysteries remain.

I am just suggesting that the glaciating effect found by pure orbital and Earth rotation dynamics is amplified by the mechanism of CO2 diminution from rock chemistry I just described, in this essay and the preceding one.
Indeed orbital effects come short of explaining what is observed. Simulations and paleoclimate analysis show that the variation in Earth’s climate is much more extreme than the variation in the intensity of solar radiation calculated as the Earth’s orbit evolves. Methane release and the like doesn’t cut it yet. If orbital forcing causes climate change, and it does, science needs to explain why the observed glaciation effect is amplified compared to the theoretical, purely astronomical effect.

I just did.

Patrice Ayme