The study of climate change has established retreating glaciers and

Question

The study of climate change has established retreating glaciers and rising global temperatures from a number of data sources. Establishing the influence of mankind upon these effects has been more difficult, because the climate is subject to oscillations that are much longer in duration than our record of direct temperature measurements, which extends back only about 150 years.
 
By drilling and conducting chemical and physical studies of ice cores on six of the seven continents, scientists have developed a method of estimating climatic information that had previously been thought inaccessible. Ice cores removed from the earth's crust and studied in order to draw such inferences are termed paleo-proxies. The values of various climatic variables at a particular time and place can be inferred through some form of proxy analysis in a given ice core sample. For example, deuterium excess indicates humidity levels, electrical conductivity indicates volcanic activity, beryllium levels indicate solar activity, and particle size and concentration indicate wind speeds. Temperature, in particular, can be inferred from the ratios of water molecules composed of stable isotopes of oxygen and hydrogen, namely 1H2H16O and 1H218O. Because molecules consisting of these isotopes have slightly different weights than their more common counterparts, their concentration in the ice core in a given epoch depends on the condensation temperature prevailing at the time. This technique enables scientists to estimate the air temperature of condensation when the snow fell and establish variations in temperature over a series of multiple samples.
 
One advantage of using ice cores as a paleo-proxy is that ice core samples can be extracted from across the world using different drilling techniques, for analysis either on-site or in a laboratory, with results that can be compared to each other and stitched into a coherent global picture. The primary sources of ice cores are the ice sheets of Antarctica and Greenland, whose thickness allows scientists to extract long cores representing time spans of up to 100,000 or even 400,000 years. Nevertheless, samples representing spans of multiple centuries have been extracted more recently at low latitudes--for example, at Mt. Kilimanjaro, in the Andes Mountains, and on the Himalayan plateau. Depending on the objectives of the project and the nature of the ice core, scientists use a variety of types of drill ranging from hand-powered auger drill to electro-mechanical drills. A limitation of using ice cores is that they represent data for conditions during snowfall only. Periods bereft of snowfall will fail to leave a record in the ice and can even disrupt the essential step of dating the samples. To mitigate this problem, multiple cores are typically extracted from nearby locations. A more critical limitation of the ice core method, one indicative of the larger problem at hand, is that as ice fields continue to retreat, the ability to measure in some locations will disappear entirely.   1  
 1. In the passage, the author is primarily interested in

A. describing the data that supports a scientific theory
B. illustrating how a research method has generated results that challenge an accepted theory
C. arguing that data obtained from a particular research method are as useful as data obtained directly
D. describing a scientific challenge and a research technique to address that challenge
E. providing an overall evaluation of a research technique

2  
 2. The author of the passage would be most likely to agree with which of the following statements about using ice cores as paleo-proxies?

A. It is the only feasible method to collect climate data.
B. It yields data that are insufficient to determine the influence of mankind on retreating glaciers.
C. It should not be widely adopted, since it will be impossible in the near future.
D. It is one of multiple valid sources of data on the climate.
E. It yields unreliable data about global temperature but has advanced the state of our scientific knowledge.

3  
 3. It can be inferred from the passage that the technique of using ice cores to determine historical temperatures would be less advantageous if which of the following were true?

A. It indicated different temperatures at different times for a particular location, according to different isotope concentrations in the sample.
B. It indicated different results at the same location, according to differing extraction methods of the samples.
C. It yielded information dating back only 80,000 years in most locations.
D. It indicated that the ratios of oxygen isotopes in the air in a given location varied over time.
E. It indicated that ice sheets were not retreating.

4  
 4. According to the passage, which of the following is true of the ice cores extracted at low latitudes?

A. They indicate that sediments found during an ice age contain more calcium carbonate than sediments formed at other times.
B. They are less reliable than the evidence from rocks on land in determining the volume of land ice.
C. They can be used to deduce the relative volume of land ice that was present when the sediment was laid down.
D. They are more unpredictable during an ice age than in other climatic conditions.
E. They can be used to determine atmospheric conditions at various times in the past.

5  
 5. It can be inferred from the passage that the air temperature of condensation at a time in the past when snow fell

A. can be determined from the ratio of hydrogen and oxygen isotopes in the air
B. correlates with the average air temperature in that area at that time
C. correlates with the average air temperature in that area at the time of measurement
D. creates land ice of a higher density at higher temperatures
E. rises during periods in which glaciers are retreating

6  
 6. It can be inferred from the passage that snowfall at locations where ice cores are extracted

A. is generally heavier than at other land locations covered with ice
B. is invariably more common during colder periods
C. fails to leave a record in the ice at entirely unknown dates in time
D. becomes less common as ice fields continue to retreat
E. is consistent enough within an area to reduce dating errors

Source:  GMAT Free  (14)

Sajjad1994 · Answer

Official Explanation

2. The author of the passage would be most likely to agree with which of the following statements about using ice cores as paleo-proxies?

Difficulty Level:   700

Explanation

In this question, and as we have seen in other questions, the phrase  "would be most likely to agree"  sounds like mind-reading. In fact, we want to find a statement that is supported by the passage, and preferably a statement that must be true on the basis of the passage.

If the author would have to believe a given statement in order to be consistent with what's stated in the passage, that statement is objectively the best answer choice. Which answer choice must the author agree with?

Choices (B), (C), and (E) are all out , because they express opinions too strong to be drawn from the passage.

Meanwhile,  (A) and (D)  are mutually exclusive, hinting that one must be wrong and one must be right. Is using ice cores the only way to collect climate data? No; we have direct measurements going back 150 years (and maybe other methods).

The correct answer is (D).

Hope it helps

Sajjad1994 · Answer

Official Explanation

5. It can be inferred from the passage that the air temperature of condensation at a time in the past when snow fell

Difficulty Level:   700

Explanation

In this question, before heading to the answer choices, we can briefly refresh our memory about the  "air temperature of condensation"  by looking back at the passage. This phrase is referred to specifically only in lines:  "This technique enables scientists to estimate the air temperature of condensation when the snow fell and establish variations in temperature over a series of multiple samples."

The clearest inference we can draw is a simple one, which is that, if you can establish the air temperature of condensation at a point in the past, you can establish the temperature then or the variations in temperature.

That, in fact, is exactly what answer  choice (B)  communicates. Answer choices  (A) and (C)  both confuse the conditions of measurement and the conditions we are trying to infer knowledge about in the past.

Choices (D) and (E)  are out of the scope of the passage.

The correct answer is (B).

6. It can be inferred from the passage that snowfall at locations where ice cores are extracted

Difficulty Level:   700

Explanation

In this question, we are asked about snowfall. A glance at the answer choices reveals a theme: we care specifically about the amount or frequency of this snowfall. That means we are talking about the  final paragraph , specifically in ending lines. There are two key points. One is that  "periods bereft of snowfall"  leave a gap in the record and can mess up assigning a date to the records.

The second key point is that the problem is  "mitigated,"  or partly solved, by extracting samples from an area. We will look for one or both points, the drawback and the mitigation, in the answer choices.

Choices (A), (B) and (D)  all fail to touch on either the drawback or the mitigation. Meanwhile,  choice (C)  is relevant to the drawback, and  choice (E)  to the mitigation. One of the two must have an objective error, while the other is likely to be necessarily true.

Choice (E)  is necessarily true: if snowfall were not consistent enough within an area to reduce dating errors, then the mitigation described in the passage--taking multiple samples in an area--would not be a mitigation at all.

Choice (C)  must have an objective error. It slightly distorts the drawback described in the passage, because we are not told that the dates in time are unknown, only  "disrupted."  Moreover, the fact that the disruption can be mitigated means that the dates are ultimately not entirely unknown.

The correct answer is (E).

Hope it helps

mimishyu · Answer

6. It can be inferred from the passage that snowfall at locations where ice cores are extracted

A. is generally heavier than at other land locations covered with ice
B. is invariably more common during colder periods
C. fails to leave a record in the ice at entirely unknown dates in time(it should be “if these snowfall didn’t even appear”)
D. becomes less common as ice fields continue to retreat
E. is consistent enough within an area to reduce dating errors

Explanation

In this question, we are asked about snowfall. A glance at the answer choices reveals a theme: we care specifically about the amount or frequency of this snowfall. That means we are talking about the final paragraph, specifically in ending lines. There are two key points. One is that "periods bereft of snowfall" leave a gap in the record and can mess up assigning a date to the records.

The second key point is that the problem is "mitigated," or partly solved, by extracting samples from an area. We will look for one or both points, the drawback and the mitigation, in the answer choices.

Choices (A), (B) and (D) all fail to touch on either the drawback or the mitigation. Meanwhile, choice (C) is relevant to the drawback, and choice (E) to the mitigation. One of the two must have an objective error, while the other is likely to be necessarily true.

Choice (C) must have an objective error. It slightly distorts the drawback described in the passage, because we are not told that “the snowfall’s date in time” are unknown, only "disrupted." Moreover, the fact that the disruption can be mitigated means that the dates are ultimately not entirely unknown.
I can understand this explanation quite well….
The correct answer is (E).

Choice (E) is necessarily true: if snowfall were not consistent enough within an area to reduce dating errors, then the mitigation described in the passage--taking multiple samples in an area--would not be a mitigation at all.

Periods bereft of snowfall will fail to leave a record in the ice and can even disrupt the essential step of dating the samples. To mitigate this problem, multiple cores are typically extracted from nearby locations.
So “periods which had the occurrence of snowfall” can leave a record in the ice and can access the essential step of dating the sample.

How in anywhere of this passage has mentioned that if we want “to reduce dating errors”, then snowfall must be “consistent within an area”????
The passage only mention that if we want to ‘’date the sample”, there must be the “occurrence of snowfall”….???

To mitigate this problem, multiple cores are typically extracted from nearby locations.
How can we infer from this sentence that snowfall at location must be “consistent within an area”…???

kunalc20 · Answer

For question 1, why E is not the answer ?
Please explain

Sajjad1994 · Answer

This is a must be true question and we have to find an answer which can be validated by the information in the passage, E is an extreme answer choice and we can not draw this information based on the text of the passage. So E is wrong here.

bestreturn · Answer

I don't get Q3.

How do you negate C? If you only have upto 80,000 years in most places, then you wouldn't be able to get the whole picture prior to 80,000 right?
On the other hand, B if we can agree on an extraction method then at least we still can get consistent result

miag · Answer

Hi,

That is a good question, let me try to help you out with it:
- Why choice C) does not weaken. It says that:

Far exceed the 150-year instrumental record mentioned in paragraph 1
Still allow scientists to study long-term climate oscillations

So while 80,000 years is less than 100,000 or 400,000, it’s still a huge improvement, not something that makes the technique less advantageous

- Choice B on the other hand, says different extraction methods at the same location give different results.
That directly undermines:

Comparability of samples
The ability to stitch into a coherent global picture (explicitly stated in the passage)

Hope this helps clarify!

bestreturn

I don't get Q3.

How do you negate C? If you only have upto 80,000 years in most places, then you wouldn't be able to get the whole picture prior to 80,000 right?
On the other hand, B if we can agree on an extraction method then at least we still can get consistent result

MacT750 · Answer

Can someone explain Q1 and Q4

guddo · Answer

1. In the passage, the author is primarily interested in

The passage begins by explaining the challenge of understanding long-term human influence on climate due to short historical temperature records. It then introduces ice core analysis as a method to infer past climate conditions, detailing how it works, its advantages, and its limitations. The primary focus is on presenting this research technique as a response to the scientific challenge.

A. describing the data that supports a scientific theory

Incorrect. The passage describes a research method and its applications, not data that supports a specific scientific theory. No particular theory is presented or defended.

B. illustrating how a research method has generated results that challenge an accepted theory

Incorrect. The passage does not discuss any accepted theory being challenged. It explains how ice cores provide historical climate data, not how that data contradicts existing beliefs.

C. arguing that data obtained from a particular research method are as useful as data obtained directly

Incorrect. While the passage shows ice core data is valuable, it never argues that proxy data is "as useful as" direct measurements. It presents the method as a necessary alternative due to the lack of direct historical data.

D. describing a scientific challenge and a research technique to address that challenge

Correct.  This captures the structure: first, the challenge (short direct records, need for long-term climate understanding), then the technique (ice core analysis) to address it, including its workings, strengths, and weaknesses.

E. providing an overall evaluation of a research technique

Incorrect. The passage provides an overview and description of the technique, including its pros and cons, but "overall evaluation" is too narrow. The main interest is broader: introducing the method as a solution to the identified challenge.

Answer: D

guddo · Answer

4. According to the passage, which of the following is true of the ice cores extracted at low latitudes?

A. They indicate that sediments found during an ice age contain more calcium carbonate than sediments formed at other times.
B. They are less reliable than the evidence from rocks on land in determining the volume of land ice.
C. They can be used to deduce the relative volume of land ice that was present when the sediment was laid down.
D. They are more unpredictable during an ice age than in other climatic conditions.
E. They can be used to determine atmospheric conditions at various times in the past.

The passage indicates that ice cores, including those extracted from low-latitude sites such as Mt. Kilimanjaro, the Andes Mountains, and the Himalayan plateau, are used to infer various past climatic conditions. Specifically, it states that through proxy analysis, scientists can estimate values for climatic variables such as humidity, volcanic activity, solar activity, wind speeds, and temperature, all of which are atmospheric conditions.

Answer: E

Sajjad1994 · Answer

Official Explanation

1. In the passage, the author is primarily interested in

Explanation

We have already answered this question: the author's purpose here is to describe the ice core method. The most fitting answer  choice is (D) .

Choices (A), (B),  and  (C)  are out because the passage reveals nothing about the data or results obtained from ice core research.

(E)  would entail passing judgment on the ice core method, which the author does not do; the tone is only subtly positive.

The correct answer is (D).

Sajjad1994 · Answer

Official Explanation

3. It can be inferred from the passage that the technique of using ice cores to determine historical temperatures would be less advantageous if which of the following were true?

Explanation

The point of the ice core method for temperatures that the isotope ratios in the ice indicate what the temperature was at a point the past. That's a pretty basic fact about the technique, but we can compare to the answer choices and see how far it gets us.

Answer  choice (A)  might sound at first like it describes some sort of inconsistency, but, in fact, answer  choice (A)  would imply that the technique is working, or at least might be working correctly. So  (A)  is out.

(B)  is similar to  (A) , but it mentions getting different results for different extraction methods. That contradicts one of the big advantages of this technique, as stated in paragraph three--near the end of the paragraph, it talks about using big drills and hand drills, for example. If we have eliminated an advantage of the technique, we have made the technique less useful.

Answer  choices (C)  and  (E)  are plausible but are not supported by the passage.

Choice (D)  is out on similar grounds to  (A) .

The correct answer is (B).

4. According to the passage, which of the following is true of the ice cores extracted at low latitudes?

Explanation

In this question, we are asked about ice cores extracted at low latitudes--that is, away from the poles. This subject came up in the context of the advantages of the ice core method, so we should expect a correct answer here that has a positive slant on the method. That point discredits  (B)  and  (D) .

(A)  and  (C)  are plausible, but unsupported.

Choice (E)  is the whole point of the passage.

The correct answer is (E).

The study of climate change has established retreating glaciers and

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The study of climate change has established retreating glaciers and

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