万物简史 第621期:冰河时代(18)

Climate is the product of so many variables—rising and falling carbon dioxide levels, the shifts of continents, solar activity, the stately wobbles of the Milankovitch cycles—that it is as difficult to comprehend the events of the past as it is to predict those of the future. Much is simply beyond us. Take Antarctica. For at least twenty million years after it settled over the South Pole Antarctica remained covered in plants and free of ice. That simply shouldn't have been possible.

气候是多种变量的产物——二氧化硫含量的上升和下降，大陆的漂移，太阳的活动，米兰柯维契周期的变更——因此，要理解过去的事情就像预言将来的事情那样困难。许多事情我们完全无法理解。举一个例子，南极洲漂移到南极地区以后，至少有2000万年的时间，那里就一直不曾有过冰川，而是为植被所覆盖着。这一切在今天听上去简直就像天方夜谭。

No less intriguing¹ are the known ranges of some late dinosaurs². The British geologist³ Stephen Drury notes that forests within 10 degrees latitude⁴ of the North Pole were home to great beasts, including Tyrannosaurus rex. "That is bizarre," he writes, "for such a high latitude is continually dark for three months of the year." Moreover, there is now evidence that these high latitudes⁵ suffered severe winters. Oxygen isotope⁶ studies suggest that the climate around Fairbanks, Alaska, was about the same in the late Cretaceous period as it is now. So what was Tyrannosaurus doing there? Either it migrated seasonally⁷ over enormous distances or it spent much of the year in snowdrifts in the dark. In Australia—which at that time was more polar in its orientation—a retreat to warmer climes wasn't possible. How dinosaurs managed to survive in such conditions can only be guessed.

更不可思议的是一些已知的晚期恐龙的栖息场所。英国地质学家斯蒂芬·特鲁里发现，北极周围10纬度范围内的森林是包括霸王龙在内的这类大动物的老家。“这简直令人费解。”他写道，“因为在这样的高纬度地区，一年中有3个月的时间处于黑暗中。”更有甚者，现在有证据显示，那些高纬度地区的冬天也十分寒冷。氧同位素研究表明，在阿拉斯加的费尔班克斯地区，白垩纪晚期的气候和现在是一样的。那么，霸王龙在那里做什么呢？它要么季节性地长距离迁徙，要么一年中有很长一段时间在冰雪交加的黑暗中度过。在澳大利亚——那时的位置比现在离南极更近——要撤到气候比较暖和的地方是不可能的。恐龙又是怎样在这样的环境中设法生存下来的呢？对此我们只能猜猜而已。

One thought to bear in mind is that if the ice sheets did start to form again for whatever reason, there is a lot more water for them to draw on this time. The Great Lakes, Hudson Bay, the countless⁸ lakes of Canada—these weren't there to fuel the last ice age. They were created by it.

有一点必须记住，要是由于无论什么原因再次开始形成冰盖，这一次有多得多的水可以利用。五大湖、哈得孙湾，以及加拿大无数的湖泊，它们那时还不存在，没有为上一个冰川期提供原料，它们是上一个冰川期的产物。

1 intriguing   

adj.有趣的；迷人的v.搞阴谋诡计(intrigue的现在分词)；激起…的好奇心

参考例句：

• These discoveries raise intriguing questions. 这些发现带来了非常有趣的问题。
• It all sounds very intriguing. 这些听起来都很有趣。 来自《简明英汉词典》

2 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

3 geologist   

n.地质学家

参考例句：

• The geologist found many uncovered fossils in the valley.在那山谷里，地质学家发现了许多裸露的化石。
• He was a geologist,rated by his cronies as the best in the business.他是一位地质学家，被他的老朋友们看做是这门行当中最好的一位。

4 latitude   

n.纬度，行动或言论的自由(范围)，(pl.)地区

参考例句：

• The latitude of the island is 20 degrees south.该岛的纬度是南纬20度。
• The two cities are at approximately the same latitude.这两个城市差不多位于同一纬度上。

5 latitudes   

纬度

参考例句：

• Latitudes are the lines that go from east to west. 纬线是从东到西的线。
• It was the brief Indian Summer of the high latitudes. 这是高纬度地方的那种短暂的晚秋。

6 isotope   

n.同位素

参考例句：

• The isotope ratio is directly used for comparing oils or gases.同位素比率直接用于比较各种石油或天然气。
• How to apply a radio isotope?如何运用放射性同位素？

7 seasonally   

参考例句：

• The price of vegetables fluctuates seasonally. 蔬菜的价格随季节变动。 来自《简明英汉词典》
• They moved seasonally among various vegetation types to feed on plants that were flourishing. 它们还随着季节的变化而在各种类型植物之间迁移，以便吃那些茂盛的植物。 来自辞典例句

8 countless   

adj.无数的，多得不计其数的

参考例句：

• In the war countless innocent people lost their lives.在这场战争中无数无辜的人丧失了性命。
• I've told you countless times.我已经告诉你无数遍了。