Mount Toba eruption doesn't seem like it could nearly kill our species
摘要
对印度尼西亚多巴火山约7.4万年前超级喷发的研究显示，其气候影响远小于此前假设。德国科学家通过分析肯尼亚-坦桑尼亚边境湖泊沉积物发现，该次喷发造成的降温幅度仅约0.5摄氏度，持续不足两年。研究指出，超大规模喷发释放的硫酸盐气溶胶颗粒较重、沉降快，对太阳辐射的散射效率反而低于中等规模喷发，因此并未对古人类生存构成显著威胁。
Mount Toba was the biggest volcanic eruption in the last 2.6 million years, and some have suggested it nearly wiped out humanity. Around 74,000 years ago, a caldera on what is now Sumatra emptied thousands of cubic kilometers of magma in about two weeks, roughly a thousand times more than Mount Pinatubo spewed out in 1991. “People thought it might have caused massive cooling of the planet, and hence threatened the survival of our ancestors,” says Jinheum Park, a geoscientist at Johannes Gutenberg University in Mainz, Germany.
Park and his colleagues went looking for the records of that catastrophe in the mud taken from the bottom of a small crater lake on the Kenya-Tanzania border. They found instead that the effects of the Mount Toba eruption lasted under two years and amounted to perhaps half a degree of cooling.
Muddy calendars
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.
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