When scientists evaluate the connection between tornadoes and climate change, there are two big questions they’re asking: First,

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问题 When scientists evaluate the connection between tornadoes and climate change, there are two big questions they’re asking: First, are the 2011 tornadoes part of a trend? Has tornado activity changed along with rising global temperatures so far? Second, scientists ask whether the factors that create tornadoes have been affected by climate change and whether those factors are likely to be affected in the future.
For one thing, our data on tornado trends are imperfect. At first glance, you might think the number of tornadoes has increased since the 1990s. But most of that is actually the result of more public awareness and better reporting and technology, improving our ability to spot smaller, weaker tornadoes and to notice tornadoes in places where few people live. Bad datum means that we can’t reliably say whether tornado counts are increasing.
There are many things that can affect the factors that make tornadoes more likely. Scientists have found that climate change is something that can affect tornado conditions. But when they looked at data for the past 30 years’ worth of Aprils in the Mississippi Valley, they don’t see evidence of any trends that would mean tornado weather is already becoming more frequent.
Because of that, it would be problematic to claim that the recent spate of tornadoes in the Southeast was caused by climate change. But that’s not the same as saying tornadoes can’t be caused by climate change. It’s not the same as saying that climate change isn’t a contributing factor. Or that tornadoes won’t be caused by climate change in the future. It’s not even the same as saying that, years from now, with better data and technology, we won’t look back and see a trend happening that isn’t obvious today. The big question—are tornadoes caused by climate change? —is made up of lots of little questions. And we don’t know all the answers to the little questions yet.

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答案 当科学家评估龙卷风与气候变化的联系时,通常会问两大问题:第一,2011年的龙卷风是否是一种趋势?到目前为止,龙卷风的活性是否因全球气温的上升发生了改变?第二,造成龙卷风的因素是否受到了气候变化的影响,这些因素未来是否可能受到影响。 首先,我们有关龙卷风趋势的数据还有待完善。乍一看,你可能认为龙卷风的数量自20世纪90年代后有所增加。但这极有可能是人们公众意识的提高、媒体对龙卷风的正面报道以及技术改进的结果,这些提高了人们发现小型、微弱龙卷风和人烟稀少地区龙卷风的能力。而不良数据意味着,我们不能肯定龙卷风发生的频率是否在增加。 很多事情都能够影响那些引发龙卷风的因素。科学家发现,气候变化便是其中之一。但当科学家们查阅密西西比河流域过去30年间四月份的数值时,他们并没有找到任何显示龙卷风天气已经变得越来越频繁的证据。 因此,我们不能将东南亚最近一连串龙卷风天气归咎于气候变化。但也不能说气候变化不能引发龙卷风天气,或气候变化不是导致龙卷风天气的一个因素,或气候变化将来不会造成龙卷风天气。甚至也不能说从现在起几年内,随着更多的数据和先进技术的出现,我们不会发现一个在今天看来不明显的趋势。那个至关重要的问题一龙卷风是否是由气候变化引起的?——是由许多小问题组成的。对于这些小问题,我们尚未找到答案。

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