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  3. One fine day about 74,000 years ago, a giant volcano on Sumatra blew its top. The volcano, named Toba, may have ejected (喷射) 1,0

One fine day about 74,000 years ago, a giant volcano on Sumatra blew its top. The volcano, named Toba, may have ejected (喷射) 1,0

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问题     One fine day about 74,000 years ago, a giant volcano on Sumatra blew its top. The volcano, named Toba, may have ejected (喷射) 1,000 times more rock and other material than Mount St. Helens in Washington state did in 1980. In the process, it cooled the climate by at least 10°C, causing a global famine.
    Paleoclimate (古气候) evidence suggests that the Toba eruption, which occurred during the last ice age, emitted lots of sulfur dioxide—vastly more than Mount St. Helens did. The eruption also coincided with the start of a 1,000-year period of even colder temperatures. Some scientists have suggested that Toba caused the deep freeze and that perhaps such an event happening today could bring on a new ice age. But models developed by National Aeronautics and Space Administration and the National Center for Atmospheric Research in Boulder, Colorado, argue otherwise.
    Researchers led by climatologist Alan Robock of Rutgers University in New Brunswick, New Jersey, ran scenarios that featured eruptions producing up to several times more sulfur dioxide than
    Toba. The result, published 27 May in the Journal of Geophysical Research: Atmospheres, was a cooler climate that lasted only a few decades. So the 1,000-year cold spell was probably part of the natural cycle that has produced more than a dozen ice ages over the past couple of million years.
    "The results virtually eliminate mega (非常大的) volcanic eruptions as one of the key drivers of global-scale glaciation," says climatologist Ellen Mosley-Thompson of Ohio State University in Columbus, who was not involved in the study. So, paleoclimatologists should focus on more likely climate coolers, she says, such as changes in ocean circulation or cyclical variations in Earth’s orbit around the sun.
    Still, if Toba erupted today like it did in the past, the results would be catastrophic. Although the volcano isn’t expected to blow its top for thousands of years, Robock and colleagues estimate a mega eruption could lower global temperatures by as much as 17°C for several years, followed by a recovery to normal conditions that could take decades. That would hit the human population with the double whammy of dramatically reduced agricultural production and widespread loss of vegetation, leading to widespread food shortages and starvation.
Which view did Alan Robock’s research verify?
选项 A、Ancient volcanic eruptions caused the Earth to freeze.
B、The 1,000-year cold spell was not caused by the Toba eruption.
C、The ice age is part of natural cycle of volcanic eruptions.
D、There won’t be any new ice age in the future.
答案B
解析 由题干中的Alan Robock’s research定位到第三段第二、三句。推理判断题。由定位句可知，模拟实验的结果显示，火山爆发所导致的气候变冷仅能持续几十年，千年寒冷期很可能是自然循环的一部分，这种循环在过去的几百万年中产生了不下12个冰河时代。因此，可以推断B)为正确答案。
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