Variations in the Climate

One of the most difficult aspects of deciding whether currentclimatic events revealevidence 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 climaticvariability 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 ambientclimate at the time can be deposited in a systematic way to provide a continuousrecord 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 relativestability 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 leastindicate how all the natural causes of climate change have combined. These include the chaotic fluctuations of the atmosphere, the slower but equally erraticbehavior 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 volcanicactivity, solaractivity, and, possibly, human activities.

One way to estimate how all the various processes leading to climatevariability 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 internalvariability of the global climate system itself, there is the added factor of external influences, such as volcanoes and solaractivity. 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 solaractivity explain quite a considerableamount 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.

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

B. With human activities as the key word, go to the first sentence and say that B must be determined before determining the impact of humans on the climate. So B is correct. Both A and D mentioned millenium. This is not what the sentence says, so both are wrong. C's best method did not say either.

According to paragraph 2, an advantage of proxy records over instrumental records is that

A. they are more-reliable measures of climatic variability in the past century

B. they provide more-accurate measures of local temperatures

C. they provide information on climate fluctuations further back in time

D. they reveal information about the human impact on the climate

C. Using proxy records as a keyword to locate the last sentence, a better picture of fluctuations further back in time, referring to the time is longer, so the answer is C, this is relatively simple, exactly the same as the article.

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

A. Because physical and chemical properties of substances are unchanging, they are useful records of climate fluctuations over time.

B. For hundreds or thousands of years, people have been observing changes in the chemical and physical properties of substances in order to infer climate change.

C. Because it takes long periods of time for the climate to change, systematic changes in the properties of substances are difficult to observe.

D. Changes in systematically deposited substances that are affected by climate can indicate climate variations over time.

D, after removing the attributive clause, the original text becomes substance can be deposited to record blabla. The causal relations between A and C are hard, the original is not, and wrong; and A is unchanging, the original is change, A is antithetical; B Is record, not infer, B wrong; and C said difficult to observe, the original did not say, wrong; D correct.

According to paragraph 3, scientists are able to reconstruct proxy temperature records by

A. studying regional differences in temperature variations

B. studying and dating changes in the properties of substances

C. observing changes in present day climate conditions

D. inferring past climate shifts from observations of current climatic changes

B. Use the word "peoxy temperature records" to locate the key word in the fourth sentence. This sentence says that many methods for reconstructing temperature, whether it is glaciers, sediments, or carbonates, belong to substance, so B is correct and others have not said.

The word "striking" in the passage is closest in meaning to

A. noticeable

B. confusing

C. true

D. unlikely

Striking: Significant and attractive. A is significant and worth noting; B is confusing; C is correct; D is impossible. So noticeable is rightly noticeable. Corresponding to the original sentence: Equally striking, however, is the relative stability of the climate in the past 10,000 years (the Holocene period). The sentence begins with the same stricking, indicating that there must be a very striking thing before. The previous sentence says there are significant natural changes, so the synonyms for significant are streking.

According to paragraphs 3 and 4, proxy data have suggested all of the following about the climate EXCEPT:

A. Regional climates may change overtime.

B. The climate has changed very little in the past 10,000 years.

C. Global temperatures vary more than regional temperatures.

D. Important natural changes in climate have occurred over large timescales.

The fourth paragraph is very short and I finished it quickly. A and D correspond to the fourth sentence of the first sentence: 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. The climate will change in a period of time; the second sentence The stability in B corresponds to changed little:Evenly striking, however, is the relative stability of the climate in the past 10.000 years (the Holocene period). So this B option is correct, not selected; only the comparison of C is in the original Did not say so C is the answer.

The word "erratic" in the passage is closest in meaning to

A. dramatic

B. important

C. unpredictable

D. common

Erratic: Weird, unstable, erratic. A is dramatic and attracts attention; B is important; C is unpredictable; D is common and common. So C, unpredictable is correct. Corresponding to the original: 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. The original sentence is equal to erratic, so before there must be one with erratic Words with similar meaning have chaotic fluctuations before, so erratic and chaotic are synonyms, chaotic chaos, and the only unpredictable option in the alternative is reliable. ABD is not right.

All of the following are mentioned in paragraph 5 as natural causes of climate change EXCEPT

A. atmospheric changes

B. the slow movement of landmasses

C. fluctuations in the amount of ice and snow

D. changes in ocean activity

B EXCEPT questions, exclusion method. A corresponds to the second sentence of the fluctuation of the atmosphere, correct, not selected; B and the original changes in land surface there is a clear distinction, wrong, election; C corresponds to the original text of the extent of ice and snow, correct, not selected; D corresponds to the original Erratic behavior of the ocean, correct, not selected.

According to paragraph 6, which of the following is true of computer models of the global climate?

A. The information they produce is still limited.

B. They are currently most useful in understanding past climatic behaviors.

C. They allow researchers to interpret the data obtained from proxy records.

D. They do not provide information about regional climates.

A. Use computer models as the key word to locate the first sentence, but this sentence is just a matter of repeating the problem. Say the computer model can give the climate complexity and give limited info, only A answer says limited info, so A is correct. Did not say anything else.

The word "deliberations" in the passage is closest in meaning to

A. records

B. discussions

C. results

D. variations

Deliberation: Thoughtful deliberation. A is a record; B is a discussion; C is a result; D is a change. So B's discussions are correct. Corresponding to the original text: Thus we need to be able to include these in our deliberations. This sentence begins with thus, indicating that this sentence is a result. The reason for the result is that more and more people think that these physical changes are The impact is computable, so we must include it in what we do. A record and C result can't be covered by subjective things, so it's wrong; our change is completely insensitive.

The word "invoked" in the passage is closest in meaning to

A. demonstrated

B. called upon

C. supported

D. expected

Invoke: cause, help. In indicates internal, voke indicates sound, so B's call upon causes correct. A is an exhibition; C is a support; D is an expectation. Corresponding to the original: Some current analyses precipitate that volcanoes and solar activity explain quite a substantial 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. The analysis can lead to some conclusions, but these conclusions cannot explain the rapid climate warming. Demonstration and support are wrong. Even if it is correct to support interpretation and display of explanations, it cannot be used dynamically; expecting substitution is correct, so we must rely on understanding.

What is the author's purpose in presenting the information in paragraph 7?

A. To compare the influence of volcanoes and solar activity on climate variability with the influence of factors external to the global climate system

B. To indicate that there are other types of influences on climate variability in addition to those previously discussed

C. To explain how external influences on climate variability differ from internal influences

D. To argue that the rapid warming of Earth in recent decades cannot be explained

B. Asked the first sentence of the entire paragraph. This sentence says that in addition to the internal, there is an external, a typical sentence. The first part is what is to be said, which is the part of the external, so the answer It is B. Both A and C say that they are compared, and the original text has no comparison at all; D is wrong because the original text does not have an argument.

Indeed, the contribution of volcanoes and solar activity would more likely have been to actually reduce the rate of warming slightly..

A

B

C

D

D three transition points, nouns volcanoes and solar activity, warming and adverbs indeed, according to the volcanoes and solar activity to determine the correct C or D; indefinite turning meaning, the previous saying fast warming, followed by the turning point should be to reduce the warming, so The correct answer is D.

A number of different and complex factors influence changes in the global climate over long periods of time.

A.In the absence of instrumental records, proxy data allow scientists to infer information about past climates.

B.Scientists see a consistent pattern in the global temperature variations that have occurred in the past.

C.Computer models are used to estimate how the different causes of climate variability combine to account for the climate variability that occurs.

D.Scientists have successfully separated natural climate variation from changes related to human activities.

E.Scientists believe that activities outside the global climate system, such as volcanoes and solar activity may have significant effects on the system.

F.Scientists have concluded that human activity accounts for the rapid global warming in recent decades.

A.C.E In the absence of options corresponds to the first and last sentence of the second paragraph of the original text, correct. The Scientists see option is the opposite of the third sentence, wrong, not selected. The Computers option corresponds to the sixth paragraph of the original text, correct. The Scientists have successfully option is the opposite of the first sentence of the first paragraph. The Scientists believe option corresponds to the first sentence of the original paragraph, correct. The Scientists have concluded the option did not say, do not choose.