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草莓小菇凉:说的非常好,十分有道理,棒棒棒!

06-08 15:44:55

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TPO-10-Variations in the Climate

One of the most difficult aspects of deciding whether current climatic events reveal evidence of the impact of human activities is that it is hard to get a measure of what constitutes the natural variability of the climate. We know that over the past millennia the climate has undergone major changes without any significant human intervention. We also know that the global climate system is immensely complicated and that everything is in some way connected, and so the system is capable of fluctuating in unexpected ways. We need therefore to know how much the climate can vary of its own accord in order to interpret with confidence the extent to which recent changes are natural as opposed to being the result of human activities.

Instrumental records do not go back far enough to provide us with reliable measurements of global climatic variability on timescales longer than a century. What we do know is that as we include longer time intervals, the record shows increasing evidence of slow swings in climate between different regimes. To build up a better picture of fluctuations appreciably further back in time requires us to use proxy records.

Over long periods of time, substances whose physical and chemical properties change with the ambient climate at the time can be deposited in a systematic way to provide a continuous record of changes in those properties overtime, sometimes for hundreds or thousands of years. Generally, the layering occurs on an annual basis, hence the observed changes in the records can be dated. Information on temperature, rainfall, and other aspects of the climate that can be inferred from the systematic changes in properties is usually referred to as proxy data. Proxy temperature records have been reconstructed from ice core drilled out of the central Greenland ice cap, calcite shells embedded in layered lake sediments in Western Europe, ocean floor sediment cores from the tropical Atlantic Ocean, ice cores from Peruvian glaciers, and ice cores from eastern Antarctica. While these records provide broadly consistent indications that temperature variations can occur on a global scale, there are nonetheless some intriguing differences, which suggest that the pattern of temperature variations in regional climates can also differ significantly from each other.

What the proxy records make abundantly clear is that there have been significant natural changes in the climate over timescales longer than a few thousand years. Equally striking, however, is the relative stability of the climate in the past 10,000 years (the Holocene period).

To the extent that the coverage of the global climate from these records can provide a measure of its true variability, it should at least indicate how all the natural causes of climate change have combined. These include the chaotic fluctuations of the atmosphere, the slower but equally erratic behavior of the oceans, changes in the land surfaces, and the extent of ice and snow. Also included will be any variations that have arisen from volcanic activity, solar activity, and, possibly, human activities.

One way to estimate how all the various processes leading to climate variability will combine is by using computer models of the global climate. They can do only so much to represent the full complexity of the global climate and hence may give only limited information about natural variability. Studies suggest that to date the variability in computer simulations is considerably smaller than in data obtained from the proxy records.

In addition to the internal variability of the global climate system itself, there is the added factor of external influences, such as volcanoes and solar activity. There is a growing body of opinion that both these physical variations have a measurable impact on the climate. Thus we need to be able to include these in our deliberations. Some current analyses conclude that volcanoes and solar activity explain quite a considerable amount of the observed variability in the period from the seventeenth to the early twentieth centuries, but that they cannot be invoked to explain the rapid warming in recent decades.

其中一个决定是否当前气候事件的最困难的方面揭示人类活动的影响的证据是,它是很难得到的东西构成了气候的自然变化的措施。我们知道,过去几千年来,气候发生了重大变化,没有任何重大的人为干预。我们也知道,全球气候系统是非常复杂的,一切都在某种程度上是相互联系的,所以这个系统是能够以意想不到的方式波动的。因此,我们需要知道有多少的气候下能以自信地解释到最近的变化是自然的而不是作为人类活动的结果在某种程度上它自己的协议而有所不同。

 

仪器记录不足以为我们提供长达一个世纪的时间尺度上全球气候变率的可靠测量。我们所知道的是,由于我们包括更长的时间间隔,记录显示越来越多的证据表明不同政权之间的气候变化缓慢。为了更好地构建更好的波动图,需要我们使用代理记录。

 

在很长一段时间内,物理和化学性质随着周围环境变化的物质可以以系统的方式沉积,以提供连续记录这些性质随时间变化的有时数百或数千年的变化。一般来说,分层是每年进行一次,因此观察到的记录变化可能会过时。有关温度,降雨等气候信息可以从系统性质的变化中推断出来,通常称为代用数据。根据格陵兰岛中部冰盖钻出的冰芯,西欧层状湖泊沉积物中嵌入的方解石贝壳,热带大西洋洋底沉积物岩芯,秘鲁冰川冰核和东部冰芯,重建了代用温度记录南极洲。尽管这些记录提供了广泛一致的迹象,表明温度变化可能在全球范围内发生,但仍然有一些有趣的差异,这表明区域气候中的温度变化模式也可能彼此显着不同。

 

代理记录清楚地表明,在几千年以上的时间尺度上,气候发生了重大的自然变化。然而,同样引人注目的是过去一万年(全新世时期)气候的相对稳定。

 

如果从这些记录所涵盖的全球气候可以提供其真实变率的衡量标准,那么至少应该说明气候变化的所有自然原因如何结合起来。其中包括大气混乱的波动,海洋中较慢但同样不稳定的行为,地表变化以及冰雪的范围。还包括由火山活动,太阳活动以及可能的人类活动引起的任何变化。

 

估计所有导致气候变率的各种过程如何结合的一种方法是使用全球气候的计算机模型。它们只能代表全球气候的完整复杂性,因此可能只能提供有限的自然变异信息。研究表明迄今为止,计算机模拟的可变性要比从代理记录中获得的数据要小得多。

 

除了全球气候系统本身的内部变化之外,还有外部影响因素,如火山和太阳活动。越来越多的观点认为,这些物理变化对气候有着可衡量的影响。因此,我们需要能够将这些纳入我们的审议。目前的一些分析认为火山和太阳活动解释了从十七世纪到二十世纪初期观测到的相当多的变化,但是它们不能用来解释近几十年来的迅速变暖。


中文翻译

According to paragraph 1, which of the following must we find out in order to determine the impact of human activities upon climate?

  • One of the most difficult aspects of deciding whether current climatic events reveal evidence of the impact of human activities is that it is hard to get a measure of what constitutes the natural variability of the climate.  A The major changes in climate over the past millennia B The degree to which the climate varies naturally C The best method for measuring climatic change D The millennium when humans began to interfere with the climate
正确答案: B

网友解析

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    joannazz  发表于 2017-12-28 17:45:29

    事实信息题
    解析:根据human activities定位到本段首句,说确定人类对气候影响的难点在于难以测量什么构成了气候的自然变化,所以要确定人类影响,首先就要测量气候的自然变化,选B

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