Evidence that the earth's atmosphere has warmed has become quite

Question

The following passage was written in the mid-1990s.

Evidence that the earth's atmosphere has warmed 
has become quite compelling, in part because it has
been reinforced recently by the development of 
accurate profiles of average annual temperatures
  (5)   throughout the last 1,000 years. These data, inferred
from studies of geological patterns and samples of ice
deposits, tree rings, and coral growth layers, indicate
that the recent increase in average temperature—a rise
of about one half of a degree Celsius over the last 100
  (10)   years—is unprecedented in the previous 1,000 years.
At the same time, other recent studies have
strengthened the controversial link between this
increase and the "greenhouse effect." Proponents of
the greenhouse effect claim that the increase was
  (15)   caused by elevated levels in the atmosphere of certain
gases that prevent heat from radiating back into space.

Early models charting the greenhouse effect were
somewhat inconsistent with observed data; they
estimated that the increase in the earth's atmospheric
  (20)   temperature over recent decades should have been
higher than the increase observed in actuality, which
led opponents to question the validity of the greenhouse
theory. But new methods have enabled scientists to
gauge the effect of greenhouse gases more accurately
  (25)   by taking into account an important factor that earlier
studies overlooked: airborne sulfates. Sulfates from
natural sources such as volcanoes as well as from
human technological sources tend to counteract the
heating effect of greenhouse gases by reflecting solar
  (30)   energy back into space. Taking into account the
varying levels of airborne sulfates indicated by the
concentration of sulfates in successive ages of glacial
ice, these scientists have calculated theoretical
temperatures for recent decades that are consistent
  (35)   with observed temperatures.

Another question for proponents of the greenhouse
theory comes from scientists who have attempted to tie
changes in the earth's atmospheric temperature to
variations in solar energy. From observations of cycles
  (40)   in several types of solar phenomena, these scientists
have developed models that chart variations in the
sun's heating effects, and the models do show a strong
decade-by-decade correspondence between solar 
activity and atmospheric temperature fluctuations. But the
  (45)   models cannot account for the entirety of the recent
rise in atmospheric temperature. While researchers
have found that the average annual atmospheric
temperature fluctuates from one year to the next, its
temperature over the long term has been relatively
  (50)   stable—deviations from the long-term average
atmospheric temperature have inevitably reverted to
this average, or equilibrium, temperature. But the
current rise in temperature surpasses the most extreme
fluctuations in temperature consistent with the models
  (55)   based on variations in solar energy. In light of all this,
it seems reasonable to conclude that changes in the
earth's atmosphere have raised its equilibrium
temperature, and that greenhouse gases represent the
best explanation of that shift.    1 
 1. Which one of the following most accurately states the main point of the passage?

(A) Though many accept the theory that the greenhouse effect is causing the recent global warming, that theory is somewhat questionable in light of recent data concerning sulfates and solar cycles.
(B) Scientific models of the effects of greenhouse gases, modified to incorporate the effects of airborne sulfates, are important because they predict that the earth's average temperature will continue to rise.
(C) New scientific evidence shows that the earth's equilibrium temperature has been rising in a way that is consistent with the greenhouse
theory, but that the increase has been less than this theory originally estimated.
(D) Recent scientific data and calculations support the claims that the earth's atmosphere is becoming warmer and that the greenhouse effect is a major cause of this warming trend.
(E) The greenhouse theory is a reasonable explanation of a recent upward trend in the earth's atmospheric temperatures only if it is combined with the solar-fluctuation theory.

2 
 2. Which one of the following most accurately describes the relation between the argumentation in the second paragraph and that in the third paragraph?

(A) Two complementary theories that the author compares in the second paragraph are then contrasted in the third paragraph, where the first theory is ultimately rejected in favor of the second.
(B) A theory that the author shows to be problematic in the second paragraph is tentatively rejected in the third paragraph in light of compelling evidence that runs counter to the theory.
(C) A theory that the author discusses in the second paragraph is tentatively accepted after weighing additional considerations in the third paragraph.
(D) A theory that the author proposes and defends in the second paragraph is substantially revised in the third paragraph in response to new findings.
(E) A theory whose validity is questioned by the author in the second paragraph is shown in the third paragraph to be consistent with observed data.

3 
 3. Which one of the following is mentioned in the passage?

(A) the way in which sulfates in the earth's atmosphere produce an effect on temperatures
(B) that airborne sulfates are the main greenhouse gases
(C) the usual duration of one cycle of varying solar energy output
(D) predictions as to the effects of global warming on glacial ice
(E) an example of a technological source of airborne sulfates

4 
 4. It can be reasonably inferred from the passage that the author considers which one of the following most crucial in judging the success of a model developed to explain the global warming trend of the previous100 years?

(A) a strong correspondence between the model's calculated average global temperatures in the last few years and data from actual temperature observations
(B) that the model predicts an increase in the earth's temperature on the basis of a simple explanatory framework
(C) the extent to which the model has been revised in light of experimental findings
(D) a close fit between the warming mechanisms postulated by the theory and those that are generally acknowledged to be able to raise atmospheric temperatures
(E) a long-term match between the model's estimated changes in the earth's temperature and data indicating the actual temperatures that have occurred

5 
 5. Which one of the following most accurately states the author's primary purpose in lines 26-35?

(A) to provide an example of a set of observations that has been predicted by a theory
(B) to argue that a new theory will need to be formulated in order to accommodate certain recent findings
(C) to demonstrate the degree to which a previously accepted theory fails to account for observed phenomena
(D) to show that a certain theory that was previously in doubt can be defended in light of additional data
(E) to propose a way of resolving a dispute between proponents of two competing theories

mailolo · Answer

Plz explain choosing E over A & how they're different in Q4)

Sajjad1994 · Answer

(A)  is a Distortion. Both the greenhouse eðect theory and the solar-fluctuation theory produce models that correspond well with temperature observations. The author ultimately rejects the solar-fluctuation models because they were unable to anticipate the drastic change (or fluctuations) in temperature  (lines 52–55).

AkankshaUniyal · Answer

In question 1,
Is option C wrong because it talks about the equilibrium temperature not the atmospheric temperature?

Sajjad1994 · Answer

Yes!  (C)  is too narrow. This only refers to the equilibrium temperature information from the third paragraph. Furthermore, although the author does state that the greenhouse effect theory models initially overestimated the temperature increase, new methods have yielded results that are consistent with the temperature increase.

Sajjad1994 · Answer

Explanation

Step 1: Identify the Question Type

The question asks for something that can  “reasonably be inferred,”  making this an Inference question.

Step 2: Research the Relevant Text

The question refers to what the author uses to judge a model’s success. The author’s judgments comeprimarily in the  third paragraph.

Step 3: Make a Prediction

In the  third paragraph , the author introduces the solar fluctuation theory. Like the greenhouse effect theory, the solar-fluctuation theory produced some convincing models. However, in  lines 44–55 , the author presents the reasoning for judging the solar-fluctuation models as inadequate: The fluctuations in the models just weren’t as drastic as the actual change in temperatures. Thus, it can be inferred that anticipating such changes is a vital factor in judging a model’s success.

Step 4: Evaluate the Answer Choices

(E)  matches the prediction and is correct.

(A)  is a Distortion. Both the greenhouse effect theory and the solar-fluctuation theory produce models that correspond well with temperature observations. The author ultimately rejects the solar-fluctuation models because they were unable to anticipate the drastic change (or fluctuations) in temperature  (lines 52–55).

(B)  is Out of Scope. The author never suggests that any theory has a  “simple explanatory framework.”

(C)  is a Distortion. In the second paragraph, the greenhouse eðect theory was revised to account for sulfates. However, there is no suggestion that experimental õndings were the cause of that revision. And even if they were, it wasn’t the deciding factor that swayed the author in the third paragraph.

(D)  is not supported. The author’s judgments are based on how well the models õt temperature data, not about the warming mechanisms they describe.

Answer: E

Raman109 · Answer

2. Which one of the following most accurately describes the relation between the argumentation in the second paragraph and that in the third paragraph?

(A) Two complementary theories that the author compares in the second paragraph are then contrasted in the third paragraph, where the first theory is ultimately rejected in favor of the second. - There are no "Two complementary theories." The author talks about old models and new models.

(B) A theory that the author shows to be problematic in the second paragraph is tentatively rejected in the third paragraph in light of compelling evidence that runs counter to the theory. - "tentatively rejected in the third paragraph." opposite.

(C) A theory that the author discusses in the second paragraph is tentatively accepted after weighing additional considerations in the third paragraph. - The greenhouse theory.

(D) A theory that the author proposes and defends in the second paragraph is substantially revised in the third paragraph in response to new findings. - the author doesn't propose or defend any theory.

(E) A theory whose validity is questioned by the author in the second paragraph is shown in the third paragraph to be consistent with observed data. - the author questions no theory in the second paragraph. There have been some inconsistencies in the earlier model, but the author never questions whether the theory of greenhouse gases affecting the temperature rise is valid.

nikitathegreat · Answer

Q4

(A) a strong correspondence between the model's calculated average global temperatures in the last few years and data from actual temperature observations

(E) a long-term match between the model's estimated changes in the earth's temperature and data indicating the actual temperatures that have occurred

Can we reject option choice A basis the timeline - in the last few years??  GMATNinja

Also, can you explain Q2 ans choice - why are we saying tentaively accepted? Doesnt the last para says that it is the best explanation.

GMATNinja · Answer

Question 4 
 
Yup, the "last few years" part is enough to eliminate (A) in question 4.

As for choice (C) in question 2, the first part of the final sentence is key:
 
So the author doesn't quite say that greenhouse gases represent the best explanation. Instead, the author says that   it seems reasonable to conclude   that greenhouse gases represent the best explanation (and that changes in the earth's atmosphere have raised its equilibrium temperature).

Saying that those two conclusions are   reasonable   is consistent with "tentatively accepting" greenhouse theory, so (C) works.

I hope that helps!

Evidence that the earth's atmosphere has warmed has become quite

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Evidence that the earth's atmosphere has warmed has become quite

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