The Official Guide for GMAT Verbal Review 2018 New RC This passage is excerpted from material published in 1997. Scientists have been puzzled by the seeming disparity between models of global warming based on greenhouse gas emissions and actual climatological data. In short, the world is not warming up as much as these models have predicted. In the early 1990s, Pat Michaels sought to explain this disparity, suggesting that sulfate emissions in industrial areas had a cooling effect, thus temporarily retarding global warming. Michaels later came to doubt this idea, however, pointing out that since most sulfate is emitted in the Northern Hemisphere, its cooling influence should be largely limited to that hemisphere. Yet, since 1987, warming in the Southern Hemisphere, which had been relatively intense, has virtually ceased, while warming in the north has accelerated. Thus, Michaels not only doubted the idea of sulfate cooling, but came to feel that global warming models themselves may be flawed. Ben Santer disagrees. Santer contends that, in general, global warming occurs more slowly in the south because this hemisphere is dominated by oceans, which warm more slowly than the landmasses that dominate the Northern Hemisphere. But, according to Santer, the situation remains complicated by sulfate cooling, which peaked in the north in the mid-twentieth century. It drastically slowed warming in the Northern Hemisphere, and warming in the Southern Hemisphere raced ahead. Since 1987, Santer argues, the greenhouse effect has reasserted itself, and the north has taken the lead. Thus, Santer disputes Michaels’s claim that model predictions and observed data differ fundamentally. 1 (Book Question: 92) 1. The passage suggests that, in the early 1990s, Michaels would have been most likely to agree with which of the following statements about the disparity mentioned in lines ( Highlighted )? A. This disparity is relatively less extreme in the Northern Hemisphere because of sulfate cooling. B. This disparity is only a short-term phenomenon brought about by sulfate cooling. C. This disparity is most significant in those parts of the world dominated by oceans. D. The extent of this disparity is being masked by the temporary effect of sulfate cooling. E. The disparity confirms that current models of global warming are correct. 2 (Book Question: 93) According to the passage, Santer asserts which of the following about global warming? A. It will become a more serious problem in the Southern Hemisphere than in the Northern Hemisphere in spite of the cooling influence of oceans in the south. B. It is unlikely to be a serious problem in the future because of the pervasive effect of sulfate cooling. C. It will proceed at the same general rate in the Northern and Southern Hemispheres once the temporary influence of sulfate cooling comes to an end. D. Until the late 1980s, it was moderated in the Northern Hemisphere by the effect of sulfate cooling. E. Largely because of the cooling influence of oceans, it has had no discernible impact on the Southern Hemisphere. 3 (Book Question: 94) The passage suggests that Santer and Michaels would be most likely to DISAGREE over which of the following issues? A. Whether climatological data invalidates global warming models B. Whether warming in the Northern Hemisphere has intensified since 1987 C. Whether disparities between global warming models and climatological data can be detected D. Whether landmasses warm more rapidly than oceans E. Whether oceans have a significant effect on global climate patterns

Hi, Let me try to help break it down: Relevant sentence from the passage: "In the early 1990s, Pat Michaels sought to explain this disparity, suggesting that sulfate emissions in industrial areas had a cooling effect, thus temporarily retarding global warming." B) matches Michaels early view: Models are basically fine Sulfate cooling is temporarily slowing warming Once sulfate effects fade, the disparity should disappear D) on the other hand: For D to be true, the passage would need to suggest that the real disparity is larger, and that sulfate cooling is hiding part of it. However this is not true and instead sulfates are introduced to explain why the disparity exists at all, not to hide a deeper one. Hope this helps!

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Scientists have been puzzled by the seeming disparity between models

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26 Aug 2024, 19:50

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Question 3

Neetikasah

If M is already questioning the validity of the models based on the data how could he disagree with the issue that climatological data invalidates global warming models

He is questioning the models based on the data derived from Climatological data

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Yes, Michaels thinks the models are flawed and does question the models based on the data.

Santer, however, does not. Santer "disputes Michaels’s claim that model predictions and observed data differ fundamentally." Santer doesn't blame the models; instead, he blames the differences in the hemispheres that the models are being applied to (i.e. amount of landmass vs. ocean, sulfate cooling).

So Michaels and Santer do in fact disagree over whether climatological data invalidates global warming models.

For more on Question #3, check out this post: https://gmatclub.com/forum/scientists-have-been-puzzled-by-the-seeming-disparity-between-models-242687.html#p1892735.

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23 Jun 2025, 09:17

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@Bunuel why the answer for 1st question is not D?

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23 Jun 2025, 20:11

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shubhim20

@Bunuel why the answer for 1st question is not D?

Hi shubhim20

The best answer is B, not D, because Michaels saw the disparity itself as a short-lived by-product of sulfate cooling, not as something whose true size was being hidden by that cooling.

Because option D mis-represents the relationship (cooling isn’t hiding the gap; cooling is the gap), it cannot be correct.

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01 Feb 2026, 18:29

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AjiteshArun

I am still not clear how is B any different from D

AjiteshArun

Look at it this way (I'm assuming numbers):

1. Global warming was expected (predicted by models) to be (say) 5°.
2. Actual warming observed was only (say) 2° (less than what the models predicted).
3. The disparity between predicted and actual temperature increases was 3° (5 - 2)°.

4. In the early 1990s, Michaels thought that this difference was attributable to sulfate emissions, which had a temporary cooling effect. That was the reason that the actual figure (2°) was less than the predicted figure (5°).
5. He later had doubts about this explanation, because (a) most sulfate is emitted in the Northern Hemisphere and (b) after 1987, warming in the Southern Hemisphere ceased while warming in the Northern Hemisphere increased.

The question is asking us what Michaels would have been likely to agree with in the early 1990s about the disparity mentioned in lines 3-4. The disparity mentioned in those lines is the difference between predicted and actual temperature increases.

Option A: This disparity is relatively less extreme in the Northern Hemisphere because of sulfate cooling.
Michaels did not ever think that the disparity between the predictions by the models and actual warming was less extreme in the Northern Hemisphere. In fact, we have no idea about what the models predicted for the Northern and Southern Hemispheres (separately).

Option B: This disparity is only a short-term phenomenon brought about by sulfate cooling.
This is exactly what the passage says (Michaels sought to explain this disparity, suggesting that sulfate emissions in industrial areas had a cooling effect, thus temporarily retarding global warming).

Option D: The extent of this disparity is being masked by the temporary effect of sulfate cooling.
"The extent of this disparity is masked" means that the actual disparity was greater than what was seen ("masked" means "hidden"). That is, the actual disparity was greater than (5 - 2 = 3)°. Let's say the actual disparity was 4°. That is not what Michaels thought. Michaels said that the reason that the disparity was 3° was sulfate emissions. That is, if sulfate emissions had not been present, the disparity would have been smaller, not greater, because actual global warming would have been closer to what the models predicted.

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01 Feb 2026, 22:20

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Hi,

Let me try to help break it down:
Relevant sentence from the passage: "In the early 1990s, Pat Michaels sought to explain this disparity, suggesting that sulfate emissions in industrial areas had a cooling effect, thus temporarily retarding global warming."

B) matches Michaels early view:

Models are basically fine
Sulfate cooling is temporarily slowing warming
Once sulfate effects fade, the disparity should disappear

D) on the other hand:
For D to be true, the passage would need to suggest that the real disparity is larger, and that sulfate cooling is hiding part of it. However this is not true and instead sulfates are introduced to explain why the disparity exists at all, not to hide a deeper one.

Hope this helps!

rak08

AjiteshArun

I am still not clear how is B any different from D

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01 Feb 2026, 22:37

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rak08

AjiteshArun

I am still not clear how is B any different from D

Hi rak08,

Sure. Let's say you tried to predict the Indian team's score in a match. Your prediction was that they'd score 240 (X), but the actual score was 190 (Y). What's the disparity between your prediction and the actual? It's 50 (X - Y). Let's call this disparity Δ.

Michaels wanted to explain Δ. That's like "what is the reason for Δ?". In the team example, we could say that something like a batting collapse or exceptional fielding by the other team was the reason or explanation for the disparity.

Option D says The extent of this disparity is being masked by the temporary effect of sulfate cooling. This means that we aren't able to see the true extent of the disparity. In our example, that'd mean that Δ is not 50. Let's say (X - Y) is somehow greater than 50. But that can only happen if your prediction was greater than 240, or the actual score was less than 190 (or both). This is not what Michaels is trying to imply about the model's prediction or about the actual increase in temperature.