Supervolcano may not have been as devastating as thought

New Scientist : The last supervolcano eruption occurred 75â000 years ago on the Indonesian island of Sumatra. The Toba eruption was believed to have produced enough sulfur dioxide to cause a global, 1000-year volcanic winter that killed a significant portion of the plants and large animalsâmdash;including humans. After studying sediment layers taken from the floor of Lake Malawi , however, Christine Lane of the University of Oxford and her colleagues are challenging that idea. They were able to relate the ash layer created by the Toba eruption to chemical traces left by microbes that adapt their structure to changes in the climate. Based on that evidence, they estimated a 1.5 °C cooling that lasted for just 20 to 30 years. Such short-term cooling suggests that the eruption had minimal impact on climate in eastern Africa, and therefore likely had minimal impact globally. However, what the actual effects may have been is still being debated. Even a short period of notable cooling could have significantly affected plant growth without affecting the animal and human populations. Why the measured amount of cooling was less than expected is uncertain. One possibility is that the chemicals released by the eruption combined in ways that countered much of the cooling from the sulfur dioxide.