Between 1995 and 2005, the North Atlantic averaged 4.1 major hurricane

Question

﻿ ‎ ‎ ‎ ‎ Between 1995 and 2005, the North Atlantic averaged 4.1 major hurricanes (category 3 or stronger) yearly. From 1971 through 1994, however, only 1.5 such hurricanes had swept through each year. According to an analysis by K. Halimeda Kilbourne, this spike in major-hurricane activity reflects a return to normal frequency after a lull in the 1970s and 1980s, rather than the development of a new pattern. Two factors thought to strongly influence hurricane development are wind shear an atmospheric phenomenon in which adjacent layers of air move at different speeds or in different directions-and sea-surface temperature. Strong wind shear tends to rip apart tropical storms before they strengthen into hurricanes, while higher sea-surface temperatures can provide more energy to a forming hurricane.

‎ ‎ ‎ ‎ Kilbourne and her colleagues noted that observed variations in wind shear and sea-surface temperature correlate not only with variations in hurricane activity but also with corresponding variations in two biological phenomena. The luminescence of coral growth rings under ultraviolet light reveals periods in which more organic matter was washed from land by heavy storm rains, which are less likely in conditions that favor higher wind shear. And populations of the microorganism G. bulloides in the upper layers of the tropical ocean are more abundant when there is persistent upwelling of relatively cool, nutrient-rich waters. This upwelling occurs as a result of strong trade winds, which also correlate with relatively high wind shear. When these microorganisms die, they become deposited in seafloor sediments, which thus record changes in their abundance.

‎ ‎ ‎ ‎ The researchers examined these biological phenomena in samples from North Atlantic areas in which hurricanes form. Based on these observations, they concluded that overall, between 1730 and 2005, the North Atlantic experienced an annual average of 3.25 category-3-or-stronger hurricanes. However, at least six lengthy intervals since 1730 showed increased hurricane activity.

‎ ‎ ‎ ‎ Other analyses of long-term natural records bolster these results. Coastal geologist Jeffrey Donnelly studied lake and lagoon sediments to compare the timing of hurricanes during the past 5,000 years with that of El Niños-weather phenomena that increase North Atlantic wind shear-and found that periods with strong, frequent El Niños experienced a lower-than-average number of hurricanes.   1 
 1. According to the passage, which of the following statements about hurricane frequency in the North Atlantic is true?

A. Hurricane frequency before the mid-twentieth century cannot be reliably estimated without accurate records of when El Niños occurred.
B. Major-hurricane frequency has remained at above-average levels during some protracted periods in the past few centuries.
C. Periods during which North Atlantic hurricane frequency is low are characterized by high sea-surface temperatures.
D. An increase in hurricane frequency can sometimes contribute to an increase in wind-shear strength.
E. From 1971 through 1994 in the North Atlantic, hurricane intensity was lower, but hurricane frequency was greater, than the historical average

2 
 2. Which of the following most accurately describes the way in which the second paragraph functions in the context of the passage?

A. It summarizes, and discusses some further possible consequences of, the conclusions reached in the study described in the passage.
B. It introduces some crucial elements of the study described in the passage and summarizes the goals of that study.
C. It provides background information essential for understanding why the study described in the passage was needed.
D. It describes some long-established methodologies in order to emphasize, by contrast, the innovative nature of the study described in the passage.
E. It explains the relevance of certain types of observations that formed the basis of the methodology used in the study described in the passage.

3 
 3. The passage indicates that which of the following is true of Kilbourne's research?

A. Based on indirect evidence, it drew conclusions that Donnelly's research corroborated through direct observations of weather phenomena.
B. It was based on observations of marine biological records whose relevance to weather phenomena was first established by Donnelly's research.
C. It used the same methods that Donnelly's research used in investigating weather phenomena but arrived at conclusions that were inconsistent with Donnelly's.
D. Its conclusions were about weather phenomena that overlapped with, and time periods that were a subset of, those investigated by Donnelly's research.
E. The questions that it was designed to answer were raised by, but not answered by, the research that Donnelly had previously conducted

4 
 4. Based on the passage, it can be most reasonably inferred that at the time Kilbourne undertook the study described in the passage, at least some hurricane researchers were

A. skeptical toward proposed explanations regarding the mechanisms by which wind shear influences North Atlantic tropical storm development
B. unable to form useful working hypotheses regarding recent sea-surface temperature ranges in the North Atlantic
C. sympathetic to the idea that the frequency of major North Atlantic hurricanes from 1995 to 2005 represented a significant departure from historical norms
D. receptive to the notion that reliable records of El Ninos are a sufficient basis for accurate predictions of annual numbers of North Atlantic major hurricanes
E. dismissive of attempts to correlate seafloor sediment composition with wind shear in areas of the North Atlantic in which hurricanes form

GMATNinja · Accepted Answer

Question 3

Question 3 asks us which answer choice is true of Kilbourne's research. The best way to answer this is to find evidence in the passage to eliminate the options one-by-one:

Donnelly's research certainly corroborated Kilbourne's conclusions. But was Kilbourne's work based on "indirect evidence"?

Nope, Kilbourne used "biological phenomena in samples from North Atlantic areas." These samples are  direct  evidence, not indirect evidence (which would be something like computer models, etc).

(A) is out.

The words that stand out here are "first established" -- did Donnelly  first  establish something that Kilbourne  later  observed?

This timeline is just not laid out in the passage. We know that Kilbourne's work was bolstered by Donnelly's, but there is no indication that Kilbourne's work was based on something that Donnelly said first.

Eliminate (B).

Kilbourne's conclusions were actually quite consistent with Donnelly's.

(C) is out.

(D) talks about two things: the weather phenomena and the time periods studied by Donnelly and Kilbourne. Did they study "overlapping" weather phenomena? And was Kilbourne's timeframe a subset of that studied by Donnelly?

Starting with weather phenomena: both researchers studied hurricanes, we know that there was overlap here. So far, so good.

Now, timeframes: Looking back at paragraph 3, we can see that Kilbourne studied the weather between 1730 and 2005. In paragraph 4, we learn that Donnelly studied weather patterns "during the past 5,000 years" -- in other words, from 5,000 years ago to today. This means that Kilbourne's timeframe is a  subset  of Donnelly's, just as (D) indicates.

(D) lines up with the info in the passage, so keep (D) for now.

Again, there is no indication that Donnelly's research came first. Additionally, Donnelly didn't just ask questions -- he found some answers as well.

Eliminate (E), and (D) is the correct answer to question 3.

I hope that helps!

GMATNinja · Answer

Question 4

Here's the question again:

So we're trying to figure out what some hurricane researchers might have believed at the time Kilbourne conducted her research. So let's go through the options one by one and see if we can find any support for each.

Nah. There's no evidence that any researchers had doubts about how wind shear influences hurricanes. (A) is out.

No evidence for this one, either. We'd need some sentence suggesting that researchers had tried and failed to come up with a hypothesis about the sea-surface temp ranges. And we don't see that anywhere.

Interesting. In the first paragraph we see the following clause: "this spike in major-hurricane activity reflects a return to normal frequency after a lull in the 1970s and 1980s,  rather than the development of a new pattern ."

In other words, it sounds as though Kilbourne and her team are shooting down an old belief, namely, that hurricane activity between 1995 and 2005 was "a new pattern." A new pattern certainly sounds like a departure from historical norms. Hang on to (C).

Not much evidence for this one, either. We do get the some research from Jeffrey Donnelly suggesting a correlation between El Nino and lower hurricane activity, but is that alone sufficient for "accurate" predictions? Well, I know that it rains more in the spring than the summer, but I haven't exactly made an accurate predication about rainfall in the spring.

So (D) is out.

"Dismissive?" Nah. No reason to think anyone doubts the correlation between seafloor sediment composition and wind shear. Kill (E).

That leaves us with (C), which is our answer.

InduV · Answer

GMATNinja  could you please help with the explanation of Q4?

einstein801 · Answer

Hi there,

I think the best way of doing it is via process of elimination and paying attention to this part of the passage "According to an analysis by K. Halimeda Kilbourne, this spike in major-hurricane activity reflects a return to normal frequency after a lull in the 1970s and 1980s, rather than the development of a new pattern." which will lead you to (C)

sachi-in · Answer

2. Which of the following most accurately describes the way in which the second paragraph functions in the context of the passage?

To ans this let's once revisit the para 2

Kilbourne and her colleagues noted that observed variations in wind shear and sea-surface temperature correlate not only with variations in hurricane activity but also with corresponding variations in two biological phenomena. The luminescence of coral growth rings under ultraviolet light reveals periods in which more organic matter was washed from land by heavy storm rains, which are less likely in conditions that favor higher wind shear. And populations of the microorganism G. bulloides in the upper layers of the tropical ocean are more abundant when there is persistent upwelling of relatively cool, nutrient-rich waters. This upwelling occurs as a result of strong trade winds, which also correlate with relatively high wind shear. When these microorganisms die, they become deposited in seafloor sediments, which thus record changes in their abundance.

Thus this para2 introduces the biological litmus tests that the researchers performed to support their thesis.

Thus this para2 introduces the biological litmus tests that the researchers performed to support their thesis.

para 1 describes the phenomenons affecting the hurricane frequencies.

A. It summarizes, and discusses some further possible consequences of, the conclusions reached in the study described in the passage.
 Wrong: The elements described are not consequences of the study but rather are evidience on which their study ( Para 1 ) is based 
B. It introduces some crucial elements of the study described in the passage and summarizes the goals of that study.
 Wrong: It does introduce crucial elements but those are njot goals but rather evidience that gives support to the theory 
C. It provides background information essential for understanding why the study described in the passage was needed.
 Wrong : the study was needed to prove that the change in hurricane frequency is not a deviation but rather a standard over years 
D. It describes some long-established methodologies in order to emphasize, by contrast, the innovative nature of the study described in the passage.
 Wrong: It doesn't mention if these are long-established methodology 
E. It explains the relevance of certain types of observations that formed the basis of the methodology used in the study described in the passage.
  Correct: It definitely tells us why certain observations that were used in the study are relevant

Pr4n · Answer

1. According to the passage, which of the following statements about hurricane frequency in the North Atlantic is true? 
 
A. Hurricane frequency before the mid-twentieth century cannot be reliably estimated without accurate records of when El Niños occurred.

- There are 2 research models in this passage and both are showing similar and consistent results hence we cannot say El Ninos record is the only way we can estimate.

B. Major-hurricane frequency has remained at above-average levels during some protracted periods in the past few centuries.

- Look at the last line of the 3rd Para, this is paraphrasing of that line. Hence, keep this one

C. Periods during which North Atlantic hurricane frequency is low are characterized by high sea-surface temperatures.

- This is actually quite the opposite plus no direct mention about frequency to high sea surface has been established. But indirectly even if we infer it is opposite.

D. An increase in hurricane frequency can sometimes contribute to an increase in wind-shear strength.

- This again is changing the cause and effect based upon inference from the passage, hence incorrect.

E. From 1971 through 1994 in the North Atlantic, hurricane intensity was lower, but hurricane frequency was greater, than the historical average

- The only thing mentioned explicitly mentioned in the passage is that category 3 (higher intensity) hurricanes was lower, no mention of other type of comparison is made, hence this can't be reasonably inferred, if anything this is speculation

Therefore, ans is B)

Therefore, ans is B)

Robo_123 · Answer

Did not understand this passage. What could I do to still answer most of them?

miag · Answer

Hi,

Here are a couple of articles you can refer to for strategies. I would suggest try implementing some of these and see which works best for you - you can follow through the steps, and it ensures your required accuracy level too:
https://e-gmat.com/blogs/improve-gmat-r ... rehension/
https://gmatclub.com/forum/gmat-club-s- ... 83101.html
https://www.gmatninja.com/articles/gmat ... rehension/

Robo_123

Did not understand this passage. What could I do to still answer most of them?

Sajjad1994 · Answer

1. According to the passage, which of the following statements about hurricane frequency in the North Atlantic is true?

Explanation

Keep the passage summary in your mind and attack each answer choice one by one.

A)  Not supported. Passage says other long-term records (sediment, coral) already gave estimates for 1730–2005. El Nino timing is used for comparison but not essential to get frequency estimate.

B)  Seems good. “at least six lengthy intervals since 1730 showed increased hurricane activity” means  “increased”  relative to long-term average of 3.25 means above-average.  “Lengthy intervals” = protracted periods.  Let's keep it.

C)  Actually high SST favor hurricanes; low hurricane freq is linked to high wind shear (which might occur with cooler SST in some contexts? Not necessarily high SST). So not stated.

D)  Not Supported. wind shear influences hurricanes, not hurricanes influencing wind shear. No causality in reverse direction stated.

E)  1971–1994 had only 1.5/year vs. historical avg 3.25 ----> frequency lower, not greater. Hence wrong.

Answer: B

eaat · Answer

Here are my notes from the passage. I got 3/4 wrong when I did the practise test, but having redone it with better process I was able to get 4/4 correct.

Kilbourne: spike is actual normal frequency, lull in 70s and 80s rather than new pattern
Influence hurricane development 
* Wind shear - prevents hurricanes
* Sea-surface - higher temps provide energy to hurricanes

Kilbourne: wind shear & temp not only with hurricane activity but also 2 biological phenomena 
* Periods where more organic matter washed from land (less lively in conditions with heavy wind shear)
* Bulls more abundant in upwelling, cooler waters 
Upwelling is result of strong wind shear

Scientists used these samples to see when hurricanes formed
1730 - 2005 - 3.25 hurricanes, lengthy showed between

Donnelly: studied sentiments, agree with Kilbournes results
Strong wind shear = less hurricanes

Between 1995 and 2005, the North Atlantic averaged 4.1 major hurricane

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GMAT Reading Comprehension (RC) Questions

Between 1995 and 2005, the North Atlantic averaged 4.1 major hurricane

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