Maybe supervolcano didn't nearly kill us all
About 70,000 years ago, the Toba supervolcano erupted in what is now Indonesia. After the eruption, the ground collapsed and left behind a depression called a caldera, which is not filled by Lake Toba and volcanic domes that have emerged in the time since, as seen in this set of images taken Jan.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 May 1, 2013
The main point about this eruption is that it occurred in a glacial period (the last one); which initiated about 110,000 Bp, well before the eruption of the YTT.
The glacial periods involve 2 climate modes.
Climate mode#1 results in a double tropical rainbelt either side of an equatorial savannah from downwelling. This is then followed N. & S. of the jungle zone by classical desert and then by temperate rainbelt at about the latitude of the N. Sahara (it is a glacial period) then by (further N. & S. a polar high pressure hood with strong katabatic airflow into the temperate rainbelt.
This is NOT a very efficient mode with the result that the equator heats rapidly and the poles refrigerate.
Climate mode#4 is composed of 3 cells per hemisphere running in a fixed geographic location with a conveyor belt of warm inflow low pressure cells in the SE sector, lots of rain in the E. lots of snow in the NE. cold return flow in the NW. slightly warmer inflow to the W. and warmer inflow SW.(all highly evaporative over land and carrying snow showers & squalls over the sea. The centre of each mode#4 cell is a high pressure cell the size of Australia.
This is a VERY efficient mode and is responsible for the glacial period, able during operation tapping the El Nino hot pool of dropping global temperatures by ~7 deg c from the interglacial norm and depositing a large ice cap on the Laurentide shield. Geometry & fixed locations mean that few other ice caps except Antarctica & Patagonia develop in mode#4.
The net effect of the operation of the mode is that equatorial oceanic heat is redistributed to the pole which remains relatively warm except in the NW, sector where the return flow occurs.
During the glacial period after initiation climate mode#4 does not run for very long (a few centuries) and will shut down when the excess equatorial heat is removed from the ocean.
Following the shutdown of climate mode#4 the cold default climate mode#1 breaks out which cause the ice caps deposited under mode#4 to refrigerate and ablate VERY slowly, while the equatorial regions warm rapidly.
Toba YTT would have caused a major dust veil index. The cooling would have resulted in an outbreak of climate mode#4 which would have drained the oceanic equatorial heat pool & dumped most of the dust veil & H2So4 aerosol onto the icecaps in a long term snowstorm during the chaos typical of the storms in the inswing sector of mode#4 running from equator to pole (reaching from ground to stratosphere).
The result of the Toba YTT was a doubling of the size of the laurentide icecap so there was a LOT of heat exchange and a hell of a lot of snow. The chaos of course would have removed the dust veil very quickly so the shutdown of mode#4 would have been typical of global temperatures in prior shutdowns (equator maybe 1 to 5 degrees c cooler than usual during mode#4 shutdowns, and equatorial ocean somewhat cooler still than the average).
Expect therefore the average day temperature to be around 18 to 20 degrees c rather than 25 to 27 degrees c and a lot of retained heat in the jungle high humidity zones.
Following the shutdown of climate mode#4 the climate mode reverts to climate mode#1 (cold default) at which point the equator heats rapidly topping out at 28 to 35 deg c which is the likely land temperature when the next mode#4 event triggers.
No doubt the jungle/savannah transition @ lake malawi would have survived without frost burns. It is also likely therefore that the Indian aboriginees would have survived (if they had a food source under all that ash).
The big hit would strike in the area of the Temperate rainbelt & N. which would have refrigerated strongly after the climate mode#4 snowdump ended. Many of the frozen carcasses in the NW. extremities of the mammoth steppes of mode#4 would be likely to remain solid for millennia.
Have a nice day: Ag
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