* Astronomy

Title: Aerosol size confines climate response to volcanic super-eruptions
Authors: Timmreck, C., H.-F. Graf, S. J. Lorenz, U. Niemeier, D. Zanchettin, D. Matei, J. H. Jungclaus  and T.J. Crowley

Read more (Subscription, PDF)

Supervolcano eruption in Sumatra deforested India 73,000 years ago
In a new study, scientists have come across what they call incontrovertible evidence that the volcanic super-eruption of Toba on the island of Sumatra about 73,000 years ago deforested much of central India, some 3,000 miles from the epicenter.
Washington, November 24 : In a new study, scientists have come across what they call "incontrovertible evidence" that the volcanic super-eruption of Toba on the island of Sumatra about 73,000 years ago deforested much of central India, some 3,000 miles from the epicenter.
The volcano ejected an estimated 800 cubic kilometres of ash into the atmosphere, leaving a crater that is 100 kilometres long and 35 kilometres wide.
Ash from the event has been found in India, the Indian Ocean, the Bay of Bengal and the South China Sea.

Read more

Title: Did the Toba volcanic eruption of ~74 ka B.P. produce widespread glaciation?
Authors: Alan Robock, Caspar M. Ammann, Luke Oman, Drew Shindell, Samuel Levis, Georgiy Stenchikov

It has been suggested that the Toba volcanic eruption, approximately 74 ka B.P., was responsible for the extended cooling period and ice sheet advance immediately following it, but previous climate model simulations, using 100 times the amount of aerosols produced by the 1991 Mount Pinatubo eruption, have been unable to produce such a prolonged climate response. Here we conduct six additional climate model simulations with two different climate models, the National Centre for Atmospheric Research Community Climate System Model 3.0 (CCSM3.0) and National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE, in two different versions, to investigate additional mechanisms that may have enhanced and extended the forcing and response from such a large supervolcanic eruption. With CCSM3.0 we include a dynamic vegetation model to explicitly calculate the feedback of vegetation death on surface fluxes in response to the large initial reduction in transmitted light, precipitation, and temperature. With ModelE we explicitly calculate the effects of an eruption on stratospheric water vapour and model stratospheric chemistry feedbacks that might delay the conversion of SO2 into sulphate aerosols and prolong the lifetime and radiative forcing of the stratospheric aerosol cloud. To span the uncertainty in the amount of stratospheric injection of SO2, with CCSM3.0 we used 100 times the Pinatubo injection, and with ModelE we used 33, 100, 300, and 900 times the Pinatubo injection without interactive chemistry, and 300 times Pinatubo with interactive chemistry. Starting from a roughly present-day seasonal cycle of insolation, CO2 concentration, and vegetation, or with 6 ka B.P. conditions for CCSM3.0, none of the runs initiates glaciation. The CCSM3.0 run produced a maximum global cooling of 10 K and ModelE runs produced 8 - 17 K of cooling within the first years of the simulation, depending on the injection, but in all cases, the climate recovers over a few decades. Nevertheless, the "volcanic winter" following a supervolcano eruption of the size of Toba today would have devastating consequences for humanity and global ecosystems. These simulations support the theory that the Toba eruption indeed may have contributed to a genetic bottleneck.

Read more

A stash of ancient tools in India hints that life carried on as usual for humans living in the fall-out of a massive volcanic eruption 74,000 years ago.
Michael Petraglia, from the University of Cambridge, UK, and his colleagues found the stone tools at a site called Jwalapuram, in Andhra Pradesh, southern India, above and below a thick layer of ash from the eruption of the Toba volcano in Indonesia an event known as the Youngest Toba Tuff eruption.
The tools from each layer were remarkably similar, and Petraglia says that this shows that the huge dust clouds from the eruption didn't wipe out the population of tool-using people.

"Whoever was there seems to have persisted through the eruption".

This is the first archaeological evidence associated with the Toba super eruption,  and it contradicts theories that the eruption had a catastrophic effect on the area that its ash blanketed.

Read more