Study: Ancient Toba supereruption had little lasting effect on climate
A new study of lake mud from East Africa suggests the Toba supereruption 74,000 years ago caused only about half a degree of cooling for under two years, challenging the idea that it nearly wiped out humanity.
The researchers looked for records of the catastrophe in mud taken from the bottom of a small crater lake on the Kenya-Tanzania border. Volcanic eruptions inject sulfur dioxide into the stratosphere, where it becomes a haze of tiny droplets that reflect sunlight back into space. Bigger eruptions eject more sulfur dioxide and, in principle, cause more cooling. But this trend stops working when the eruption exceeds a certain magnitude. “Bigger sulfate aerosols settle quickly, because they are heavier,” Park explains. This quick settling makes them less effective in scattering incoming solar radiation.
The findings, based on the sediment core, provide a direct record of regional climate response near the site where early modern humans lived. The study challenges a popular theory that the Toba eruption created a volcanic winter that pushed human populations to the brink of extinction. Instead, the data indicate that while the eruption was colossal, its climatic impact was relatively minor and brief, at least in East Africa.