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  3. For more than a decade, scientists have been trying to determine whether climate change is linked to intense storms, such as 200

For more than a decade, scientists have been trying to determine whether climate change is linked to intense storms, such as 200

admin2012-06-02  68
问题     For more than a decade, scientists have been trying to determine whether climate change is linked to intense storms, such as 2005’s Hurricane Katrina. Meteorologist Michael Mann of Pennsylvania State University, and colleagues attacked the question by turning to the past. They looked through drill cores from coastal waters for signs that sediments had been disturbed by major storms. Eight sites along the U. S. East Coast and Puerto Rico provided a reliable record of the number of significant hurricanes going back about 1500 years. Other climate data and models added clues to water temperatures and hurricane intensity.
    As the researchers report tomorrow in Nature, they found strong evidence that Atlantic hurricane activity peaked about 1000 years ago, producing up to 15 hurricanes a year on average — a level matched in recent times only over the past decade and a half. At the time, according to estimates constructed from other geologic data, Atlantic water temperatures were relatively warm, "though not as warm as today," Mann says. And Pacific temperatures were relatively cool, thanks to La Nina events. Warmer Atlantic waters whip up more storms, but warmer Pacific temperatures tend to create stronger jet streams that break up those storms. So the twin conditions a millennium ago produced kind of a "Perfect Storm" for hurricanes, he explains.
    Of particular interest, the sediments reveal a close link between warmer water and the number of hurricanes during the past 150 years or so. Dropping temperatures produced seven or eight hurricanes a year, while a rising thermometer, such as in the earlier part of this decade, pushed the total to 15. "All other things being equal, " Mann says, "this suggests that we are indeed likely to see not only stronger hurricanes in the Atlantic but perhaps more of them" in the near future.
    Meteorologist James Eisner of Florida State University in Tallahassee agrees with the findings, but adds a caveat. The historical data do show that a link between warmer ocean temperatures and higher hurricane frequencies has existed for at least 1500 years, he says. However, there’s a high degree of uncertainty in the data. That and the fact that the physics explaining the link haven’t yet been established, Eisner explains, "indicate this is not the ’ smoking gun’ we’ve been looking for that would allow us to confidently project what will happen as the oceans continue to warm. "
The most useful information Michael Mann could directly see from the drill cores should be
选项 A、how Hurricane Katrina had disturbed the sediments.
B、how often hurricanes occurred over the past 1500 years.
C、how many times hurricanes had occurred in the last 1500 years.
D、how water temperatures had changed in the last 1500 years.
答案C
解析 事实细节题。由题干关键词将答案依据定位于第一段。第一段第四句说位于美国东海岸和波多黎各的8个观察点提供了一份1500年来大飓风发生次数的可靠记录。由下文的调查内容可知他们要找的就是在1500年间的发生次数与时间之间的关系，也就是发生的频率。频率不能直接看到，能看到的是发生次数，选项[C]符合题意，排除[B]。选项[A]“沉积物如何被卡特里娜飓风搅乱的”，不是该研究要找的最有用的信息。水温是通过其他数据和模型获得的，排除[D]。
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