Atmospheric carbon dioxide (C02) has been increasing since 1700

Question

Atmospheric carbon dioxide (CO2) has been increasing since 1700, but the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed. Plant ecologist Allen Auclair claims that the woodlands of the Northern Hemisphere have been acting as a carbon sink, absorbing carbon from the atmosphere and turning it into wood. Auclair uses measurements of factors affecting the area and density of a forest—such as logging, fires, and pests — and estimates of tree growth rates to argue that increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon.

To determine whether the woodlands as a whole are releasing or absorbing carbon, the volume of wood added to the woodlands must be compared with the wood lost. Auclair's analysis of the past hundred years shows the woodlands changing from a carbon source to a carbon sink. Before 1890, northern woodlands were a source of CO2 mainly because of forest fires and logging. Such deforestation releases CO2 because debris from the forest floor rots more quickly when the trees are cleared. After 1920, the steep increase in tree growth rates surpassed the losses stemming from fire and logging, turning the northern forests from a carbon source into a carbon sink and storing CO2 from fossil fuel over the next fifty years.   1 
 1. The passage is primarily concerned

A. refuting a claim about the causes of a phenomenon
B. presenting an analysis of a common natural process
C. providing an explanation for a puzzling phenomenon
D. evaluating the methodology used in a recent study
E. contrasting two explanations of an unexpected phenomenon

2 
 2. It can be inferred from the passage that Auclair's claim about carbon and the northern woodlands would be most seriously undermined if which of the following were true?

A. The northern woodlands functioned as a carbon source rather than as a carbon sink prior to 1890.
B. The rate of tree growth in the northern woodlands increased throughout the twentieth century.
C. The northern woodlands absorbed larger amounts of carbon after 1920 than they had in previous years.
D. During the twentieth century, the total volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume.
E. The northern woodlands lost trees to forest fires and logging in the early twentieth century.

3 
 3. It can be inferred from the passage that the northern woodlands would be more likely to function as a carbon source if which of the following were to occur?

A. Vegetation regrowing on land from which trees had been cleared grew back fast enough to absorb as much CO2 as was released by deforestation.
B. Debris from the forest floor rotted less quickly after the rate of tree growth increased.
C. A significant increase in the number of pests that destroy trees caused an increase in tree loss.
D. Pollution resulting from burning fossil fuels provided trees with extra nutrients, thus increasing the rate of their growth.
E. A decrease in temperature caused a significant decrease in the number of fires in the northern woodlands.

guddo · Accepted Answer

﻿Atmospheric carbon dioxide (CO2) has been increasing since 1700, but the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed. Plant ecologist Allen Auclair claims that the woodlands of the Northern Hemisphere have been acting as a carbon sink, absorbing carbon from the atmosphere and turning it into wood. Auclair uses measurements of factors affecting the area and density of a forest-such as logging, fires, and pests - and estimates of tree growth rates to argue that increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon.

To determine whether the woodlands as a whole are releasing or absorbing carbon, the volume of wood added to the woodlands must be compared with the wood lost. Auclair's analysis of the past hundred years shows the woodlands changing from a carbon source to a carbon sink. Before 1890, northern woodlands were a source of CO2, mainly because of forest fires and logging. Such deforestation releases CO2, because debris from the forest floor rots more quickly when the trees are cleared. After 1920, the steep increase in tree growth rates surpassed the losses stemming from fire and logging, turning the northern forests from a carbon source into a carbon sink and storing CO2 from fossil fuel over the next fifty years.   1 
﻿ 1. It can be inferred from the passage that the northern woodlands would be more likely to function as a carbon source if which of the following were to occur?

A. Vegetation regrowing on land from which trees had been cleared grew back fast enough to absorb as much CO2 as was released by deforestation.
B. Debris from the forest floor rotted less quickly after the rate of tree growth increased.
C. A significant increase in the number of pests that destroy trees caused an increase in tree loss.
D. Pollution resulting from burning fossil fuels provided trees with extra nutrients, thus increasing the rate of their growth.
E. A decrease in temperature caused a significant decrease in the number of fires in the northern woodlands.

2 
 2. The passage is primarily concerned with

A. refuting a claim about the causes of a phenomenon 
B. presenting an analysis of a common natural process 
C. providing an explanation for a puzzling phenomenon
D. evaluating the methodology used in a recent study
E. contrasting two explanations of an unexpected phenomenon

3 
 3. It can be inferred from the passage that Auclair's claim about carbon and the northern woodlands would be most seriously undermined if which of the following were true?

A. The northern woodlands functioned as a carbon source rather than as a carbon sink prior to 1890. 
B. The rate of tree growth in the northern woodlands increased throughout the twentieth century.
C. The northern woodlands absorbed larger amounts of carbon after 1920 than they had in previous years.
D. During the twentieth century, the total volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume.
E. The northern woodlands lost trees to forest fires and logging in the early twentieth century.

MartyMurray · Answer

Explanation for Question 1

﻿ 1. It can be inferred from the passage that the northern woodlands would be more likely to function as a carbon source if which of the following were to occur?

Key to getting this question correct is being clear about what it's asking. The passage is focused on woodlands being a carbon sink, but this question is about the woodlands being more like to function as a carbon source. So, we have to be sure keep which one the question is about straight.

A. Vegetation regrowing on land from which trees had been cleared grew back fast enough to absorb as much CO2 as was released by deforestation.

Absorbing CO2 would not result in the the woodlands being a carbon source.

Eliminate.

B. Debris from the forest floor rotted less quickly after the rate of tree growth increased.

According to the passage, "deforestation releases CO2, because debris from the forest floor rots more quickly." So, debris rotting "more quickly" results in woodlands releasing CO2 or being a carbon source.

However, this choice is about the opposite, debris rotting "less quickly."

Eliminate.

C. A significant increase in the number of pests that destroy trees caused an increase in tree loss.

According to the passage, "deforestation releases CO2."

So, since "tree loss" is the same as deforestation, we would expect "a significant increase in the number of pests that destroy trees" to cause an increase in release of CO2, in other words, to cause the woodlands to be "more likely to function as a carbon source."

Keep.

D. Pollution resulting from burning fossil fuels provided trees with extra nutrients, thus increasing the rate of their growth.

Scanning the passage for "tree growth," we find the following:

the steep  increase in tree growth rates  surpassed the losses stemming from fire and logging,  turning the northern forests from a carbon source into a carbon sink

So, increased tree growth would result in the woodlands being less, rather than more, likely to function as a carbon source.

Eliminate.

E. A decrease in temperature caused a significant decrease in the number of fires in the northern woodlands.

Scanning the passage for "fires," we find the following:

northern woodlands were a source of CO, mainly because of forest fires

So, fires cause the woodlands to be a source of CO2.

Thus, a "decrease in the number of fires" would result in the woodlands being less, rather than more, likely to function as a carbon source.

Eliminate.

The correct answer is (C).

Explanation for Question 2

2. The passage is primarily concerned with

A. refuting a claim about the causes of a phenomenon

The passage does not refute any claim about causes. The only claim mentioned is Allen Auclair's claim, and the passage explains rather than refutes that claim.

Eliminate

B. presenting an analysis of a common natural process

This choice is a little tough to eliminate, but we can eliminate it because it doesn't quite capture what the passage does.

The passage does mention some natural processes, but it doesn't primarily "present an analysis" of one of them. In fact, the passage doesn't really present an analysis of any process.

Rather, it mentions those processes in order to present an explanation for the fact that "the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed."

Eliminate.

C. providing an explanation for a puzzling phenomenon

This is exactly what the passage does.

It first presents a puzzling phenomenon: "the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed."

The it presents Allen Auclair's explanation for that phenomenon.

Keep.

D. evaluating the methodology used in a recent study

The passage does not evaluate or even mention the methodology used in any study.

Eliminate.

E. contrasting two explanations of an unexpected phenomenon

This choice is half correct since the passage does discuss an explanation of what could be considered "an unexpected phenomenon," which is that "﻿the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed."

However, since the passage presents only one explanation and is not "contrasting two explanations," this choice is incorrect.

Eliminate.

The correct answer is (C).

Explanation for Question 3

3. It can be inferred from the passage that Auclair's claim about carbon and the northern woodlands would be most seriously undermined if which of the following were true?

A. The northern woodlands functioned as a carbon source rather than as a carbon sink prior to 1890.

Scanning the passage for "1890," we find the following:

Auclair's analysis of the past hundred years shows the woodlands changing from a carbon source to a carbon sink. Before 1890, northern woodlands were a source of CO, mainly because of forest fires and logging.

We see that the idea that the northern woodlands functioned as a carbon source rather than as a carbon sink prior to 1890 is in line with what Auclair says.

Eliminate.

B. The rate of tree growth in the northern woodlands increased throughout the twentieth century.

Scanning the passage for "the twentieth century," we find the following part of Auclair's explanation:

increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon

Since "increases in the growth rates of individual trees in these forests since 1920" is basically the same as "The rate of tree growth in the northern woodlands increased throughout the twentieth century," what this choice says is in line with Auclair's explanation.

Eliminate.

C. The northern woodlands absorbed larger amounts of carbon after 1920 than they had in previous years.

Scanning the passage for "1920," we find the following part of Auclair's explanation:

increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon

So, this choice is in line with Auclair's explanation.

Eliminate.

D. During the twentieth century, the total volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume.

Auclair's explanation involves the following:

increases in the growth rates of individual trees in these forests since 1920 have created a large volume of wood that accounts for the missing carbon

We see that his explanation requires that, "after 1920," in other words, during the 20th century, the volume of wood in the northern woodlands increased. For that outcome to have occurred, the rate of wood creation must have "surpassed" the rate of wood destruction.

So, if "volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume," then the volume of wood decreased, and Auclair's explanation doesn't make sense.

Keep.

E. The northern woodlands lost trees to forest fires and logging in the early twentieth century.

Auclair's explanation does not require that the northern woodlands did not lose any trees to forest fires and logging. Rather, the passage says of his explanation, "After 1920,  the steep increase in tree growth rates surpassed the losses stemming from fire and logging , turning the northern forests from a carbon source into a carbon sink."

So, trees were lost to fires and logging, but tree growth rates surpassed those losses.

So, what this choice says is in line with Auclair's explanation.

Eliminate.

The correct answer is (D).

SudipM7 · Answer

Q1. C. providing an explanation for a puzzling phenomenon - This can be directly derived from the below portion of the text.
Atmospheric carbon dioxide (CO2) has been increasing since 1700, but the amount of CO2 produced in that time by burning fossil fuels should have resulted in a much greater increase than has been observed

Q2. D. During the twentieth century, the total volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume.
I was slightly shaky here considering the mentioned timeline of the whole twentieth century whereas there's a clear divide given in the question in the form of before 1920 and after 1920. But if this were to be true, no matter the growth of woodlands - the actual amount of woodland would be less which will release more CO2 because debris from the forest floor rots more quickly when the trees are cleared.

Q3. C. A significant increase in the number of pests that destroy trees caused an increase in tree loss.
This similar to forest fire/deforestation will reduce the amount of woodland and add to atmospheric Co2.

YuktiMaheshwari · Answer

Hi  GMATNinja   karisma   Veritas

Could you please explain question 2?

Posted from my mobile device

Sajjad1994 · Answer

Explanation

2. It can be inferred from the passage that Auclair's claim about carbon and the northern woodlands would be most seriously undermined if which of the following were true?

Difficulty Level:   Easy

Explanation

Auclair's claim in the passage relies on the argument that the northern woodlands have acted as a carbon sink since 1920, absorbing carbon from the atmosphere and turning it into wood. To undermine this claim, you would need to find information that suggests the northern woodlands were not acting as a carbon sink during this period. Let's evaluate the options:

A.  This statement is consistent with the information provided in the passage and would not undermine Auclair's claim.

B.  If the rate of tree growth continued to increase throughout the twentieth century, it would support, rather than undermine, Auclair's claim about the woodlands acting as a carbon sink after 1920.

C.  This statement actually strengthens Auclair's claim, as it suggests an increase in carbon absorption by the woodlands, which is consistent with his argument.

D.  This statement would seriously undermine Auclair's claim because it suggests that the woodlands were not acting as a carbon sink, as they were losing more carbon through rot and fires than they were absorbing.

E.  This statement, if true, is consistent with the information in the passage regarding early-century losses from fires and logging, and it does not necessarily undermine Auclair's claim about the woodlands acting as a carbon sink after 1920.

The option that would most seriously undermine Auclair's claim is D. If the total volumes of wood lost to rot or fire exceeded the increases in wood volume during the twentieth century, it would challenge his assertion that the northern woodlands acted as a carbon sink during this period.

Answer: D

Raman109 · Answer

Q1 - The passage is primarily concerned

Let's see the passage structure first 
 1. The passage introduces a puzzling or strange phenomenon. What phenomenon? With the increasing use of fossil fuels, the amount of CO2 should have increased and not the other way around. So where is this excess CO2 going? 
2. That's where the author introduces Allen Auclair's claim. 
3. In the 2nd passage, the author introduces the minimum condition "must be compared with the wood lost" for the claim or theory to be true and then provides the supporting evidence.
4. Finally, the author concludes that "turning the northern forests from a carbon source into a carbon sink and storing CO2 from fossil fuel over the next fifty years." In a way supporting "Allen Auclair's claim."

A. refuting a claim about the causes of a phenomenon - opposite. The author is supporting a claim and not refuting it.

B. presenting an analysis of a common natural process - it's not "common." Opposite.

C. providing an explanation for a puzzling phenomenon - Yes. The puzzling phenomenon is "With the increasing use of fossil fuels, the amount of CO2 should have increased and not the other way around," and what is the explanation? "Allen Auclair's claim or theory."

D. evaluating the methodology used in a recent study - "evaluate" means discussing the strengths and weaknesses and then coming to a conclusion. There is no critique here. Above all the passage doesn't talk about any "methodology." The passage only shares an explanation of the puzzling phenomena and doesn't talk about the methods he measured, whether these methods were good or bad, or whether some other methods could be better.

E. contrasting two explanations of an unexpected phenomenon - there is only one explanation.

GMAT695 · Answer

Bunuel  please change the tag to GMAT PREP ( Focus ) .

Bunuel · Answer

_______________
Done. Thank you!

Prajeesh · Answer

I got all the three answers right but it took me 15 minutes to answer the whole thing. The whole being a carbon source and sink felt puzzling to me and I had to read the passage 4 times to get the gist of it. Was the passage that complicated (I don't think so). Why am I taking so much time, seeking an expert Advice.  MartyMurray   GMATNinja

MyNameisFritz · Answer

1. It can be inferred from the passage that the northern woodlands would be more likely to function as a carbon source if which of the following were to occur?

Answer to this question can be inferred from   “Auclair uses measurements of factors affecting the area and density of a forest-such as logging, fires, and pests”

A. Vegetation regrowing on land from which trees had been cleared grew back fast enough to absorb as much CO2 as was released by deforestation. - wrong effect, trees will absorb more co2
B. Debris from the forest floor rotted less quickly after the rate of tree growth increased. - wrong effect, will be less co2
C. A significant increase in the number of pests that destroy trees caused an increase in tree los - correct as mentioned from the text above
D. Pollution resulting from burning fossil fuels provided trees with extra nutrients, thus increasing the rate of their growth - wrong effect, more tree growth, more co2 they will absorb
E. A decrease in temperature caused a significant decrease in the number of fires in the northern woodland - wrong effect, there will be less fires and less co2

2. The passage is primarily concerned with

Answer to this question can be inferred from   “﻿Atmospheric carbon dioxide (CO2) has been increasing since 1700, but the amount of CO2 produced in that time by burning fossil fuels SHOULD have resulted in a much greater increase than has been observed. Plant ecologist Allen Auclair CLAIMS that...”

A. refuting a claim about the causes of a phenomenon - nothing is being refuted
B. presenting an analysis of a common natural process - not a common process as per fragment mentioned above
C. providing an explanation for a puzzling phenomenon - correct as per fragment mentioned above
D. evaluating the methodology used in a recent study - Evaluation? No pros and cons are given! Not correct!
E. contrasting two explanations of an unexpected phenomenon - no 2 explanations given

3. It can be inferred from the passage that Auclair's claim about carbon and the northern woodlands would be most seriously undermined if which of the following were true?

Answer to this question can be inferred from : “ Allen Auclair claims that the woodlands of the Northern Hemisphere have been acting as a carbon sink, absorbing carbon from the atmosphere and turning it into wood .”

A. The northern woodlands functioned as a carbon source rather than as a carbon sink prior to 1890 - Not correct, irrelevant information
B. The rate of tree growth in the northern woodlands increased throughout the twentieth century - this choice strengthens the argument, not undermines
C. The northern woodlands absorbed larger amounts of carbon after 1920 than they had in previous years - this choice strengthens the argument, not undermines
D. During the twentieth century, the total volumes of wood lost to rot or fire in the northern woodlands exceeded increases in wood volume - correct, if more wood is lost than regenerated, the northern woodlands do not act as carbon sink but as a source
E. The northern woodlands lost trees to forest fires and logging in the early twentieth century - so what? if more wood is regenerated than lost, it still acts as a carbon sink. This choice does not undermine the argument

soumyab12 · Answer

Could you please post official explanation of questions 1 and 3 as well?

Sajjad1994 · Answer

1. The passage is primarily concerned

Explanation

The passage discusses the   increase in atmospheric CO2 since 1700   and notes that the amount from fossil fuels should have caused   a greater increase than observed.   Allen Auclair claims that Northern Hemisphere woodlands have acted as a carbon sink, absorbing carbon and turning it into wood. The passage describes   how Auclair uses measurements of factors like logging, fires, pests, and tree growth rates   to argue that increased growth rates since 1920 have created a large volume of wood that accounts for the   "missing" carbon.   It further explains that before 1890, these woodlands were a carbon source due to fires and logging, but after 1920, increased growth rates turned them into a carbon sink.

A. The passage is not refuting a claim; it is supporting Auclair's explanation. It presents his analysis without challenging it.

B. Although the carbon cycle is a natural process, the passage is specifically focused on explaining a particular discrepancy (the "missing" carbon) rather than presenting a general analysis of the process itself.

C. fits well. The  "puzzling phenomenon"  is why the increase in CO2 is less than expected from fossil fuel burning. Auclair's explanation (that Northern woodlands absorbed the carbon) is presented as the solution to this puzzle.

D. The passage mentions Auclair's methodology (using measurements of factors affecting forests and growth rates), but it does not critically evaluate it. It simply describes it to support the explanation.

E. The passage does not contrast two explanations. It only presents Auclair's explanation. The shift from source to sink is part of his analysis, not a contrasting explanation.

Therefore, the passage is primarily concerned with providing an explanation (Auclair's) for the puzzling phenomenon of the less-than-expected increase in atmospheric CO2.

Answer: C

Sajjad1994 · Answer

3. It can be inferred from the passage that the northern woodlands would be more likely to function as a carbon source if which of the following were to occur?

Explanation

To determine what would make the northern woodlands more likely to function as a carbon source, we need to understand  what causes them to be a carbon source versus a carbon sink.  According to the passage:

The woodlands are a carbon source when they release more carbon than they absorb. This happened before 1890 due to forest fires and logging, which release CO2 (because debris rots more quickly when trees are cleared).

They are a carbon sink when they absorb more carbon than they release. This happened after 1920 because the increase in tree growth rates (which adds wood, thus absorbing carbon) surpassed the losses from fires and logging.

Therefore, for the woodlands to be a carbon source, the losses (from events like fires, logging, pests) must exceed the gains from tree growth.

A.  This would balance the carbon release from deforestation, making it less likely to be a net source. It might even make it a sink if growth exceeds loss.

B.  Slower rotting means less CO2 released from debris. This would reduce carbon release, making it more likely to be a sink, not a source.

C.  This is corect! Pests destroy trees, which increases loss (similar to logging or fires). This would release carbon and reduce growth. If losses increase significantly, they could exceed gains, turning the woodlands into a carbon source.

D.  Increased growth means more carbon absorption, making it more likely to be a sink, not a source.

E.  Fewer fires mean less carbon release from burning and debris. This would reduce losses, making it more likely to be a sink.

Only option C describes a scenario where losses (from pests) increase, which could cause the woodlands to release more carbon than they absorb, making them a carbon source.

Answer: C

Atmospheric carbon dioxide (C02) has been increasing since 1700

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GMAT Reading Comprehension (RC) Questions

Atmospheric carbon dioxide (C02) has been increasing since 1700

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615 to 715 in 15 Days (Ria's Strategies)

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