The Toba eruption marks the onset of
the coldest two millennia of
the Greenland ice cores (Dansgaard et al., 1993; Zielinski et al., 1996;
Lang et al., 1999; North Greenland Ice Project Members, 2004). It is
likely that the formation of the fossil soil carbonates in the Rehi section
and the first 5–10 cm of the marine core above the Toba ash span the
duration of this stadial interval. Small numbers of Middle Palaeolithic
artifacts from gravels and sands stratified below and above a thick
bed of ash in south India have been interpreted as demonstrating
insignificant impacts of Toba on terrestrial environments and human
adaptations in India (Petraglia et al., 2007). Our results challenge this
conclusion because they show that the Toba eruption led to prolonged
drought and deforestation in India, probably lasting for 1000–
2000 years. Cooling arising from the Toba super-eruption is considered
responsible for the extreme cold of ice core stadial 20 (Zielinski
et al., 1996) and is supported by our work. The precise magnitude and
duration of the Toba-induced cooling in other regions of the world is
still not well known, because their environmental records are not
stratified with clear markers of the 73 ka Toba eruption. However,
cores from three large, deep lakes in tropical Africa (Lakes Malawi,
Tanganyika and Bosumtwi) have unusual depositional events at
∼73 ka, reflecting apparently synchronous abrupt drops in lake levels
(Scholz et al., 2007). This is consistent with a severe global environmental
impact for the Toba-induced cooling.