雅思阅读中提及自然现象或自然灾害的文章一般会遵循问题解决型说明文的结构走向，即提出现象—该现象带来的影响—造成该现象的原因—应对／解决措施—结论。剑4中Test3 Passage2介绍火山喷发的文章就基本上是按照这条思路行文的。考场真题文章A new ice age虽然在具体结构上稍有改动，但对于小冰河期的影响及原理作者还是给出了较为清晰的说明。

文章首先从两幅名画入手引出气温骤降冰冻天气的反常现象：And now there is mounting evidence that the chill could return. A growing number of scientists believe conditions are ripe for another prolonged cooldown, or small ice age. While no one is predicting a brutal ice sheet like the one that covered the Northern Hemisphere with glaciers about 12,000 years ago, the next cooling trend could drop average temperatures 5 deGREes Fahrenheit over much of the United States and 10 deGREes in the Northeast, northern Europe, and northern Asia. （注意寒潮的表达）

随即，作者提到了气候变化带来的影响。Both economically and ecologically, such quick, persistent chilling could have devastating consequences（灾难性的影响）. A 2002 report titled ‘Abrupt Climate Change: Inevitable Surprises,’ produced by the National Academy of Sciences, pegged the cost from agricultural losses alone at $100 billion to $250 billion while also predicting that damage to ecologies could be vast and incalculable. A grim（严峻的） sampler: disappearing forests, increased housing expenses, dwindling（减少的） freshwater, lower crop yields（作物产量）, and accelerated species extinctions（物种灭绝）. Political changes since the last ice age could make survival far more difficult for the world’s poor（让穷人的生活更加困难）. During previous cooling periods, whole tribes simply picked up and moved south, but that option doesn’t work in the modern, tense world of closed borders.

文章最后几段重点探讨了造成小冰期的原因之一：洋流（currents）的转变。气象学家Joyce explains how such warming（指气候变暖） could ACTually be the surprising culprit（罪魁祸首）of the next mini-ice age. 这正是由于全球变暖导致了极地冰川的融化，the freshwater trend could cause a little ice age by subverting（颠覆）the northern penetration of Gulf Stream（墨西哥湾流）waters.

原本墨西哥湾流（Gulf stream）承载着流经热带所吸收的热量（laden with heat soaked up in the tropics）在向北流的过程中慢慢地把热量释放出来（surrenders heat to the air），渐渐冷却下来的湾流变得密度越来越大而沉积到北大西洋的底层（the now-cooler water becomes denser and sinks into the North Atlantic）。正是这种冷暖交替形成了调节全球大气的热盐环流（thermohaline circulation）。而随着北极冰川的融化，北大西洋淡水含量增加（the North Atlantic fills with freshwater）, 使得洋流密度变小而不易下沉（it grows less dense, making the waters carried northward by the Gulf Stream less able to sink）。这股加入的大量淡水就很有可能会影响热盐环流的走向（The new mass of relatively fresh water sits on top of the ocean like a big thermal blanket, threatening the thermohaline circulation. That in turn could make the Gulf Stream slow or veer southward.）

文章虽然没有给出解决建议和做最终conclusion，但作为说明文还是清晰地给出了自然现象的原理和造成的影响。所以学生在遇到自然现象或自然灾害类的文章时，可以带着该类文章常见结构来分析文章和解题，即使有学科类专业生词也能把握文章大致走向。

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