PrepTest 150

Topic: Science

Paragraph 1

• Paragraph note
  • Phenomenon: Earth's annual temperature increase; evidence links the increase to the greenhouse effect
• Views, minor Meta-Structures, and the author's attitude
  • Comparison:
    • The current average temperature is about 0.5 degrees Celsius higher than it was 100 years ago (second sentence)
  • Cause-and-effect relationship, according to proponents of the greenhouse effect:
    • Elevated levels of certain gases cause heat to be trapped in the earth's atmosphere (last sentence)
  • Author's attitude: "quite compelling" (first sentence); "unprecedented" (second sentence); "strengthened" (last sentence); "controversial" (last sentence)

Paragraph 2

• Paragraph note
  • Inconsistencies in greenhouse effect data and correction with updated data taking sulfates into account
• Views, minor Meta-Structures, and the author's attitude
  • Comparison, according to early models of the greenhouse effect:
    • Models estimate that increase in the earth's atmosphere should have been higher than the observed increase (first sentence)
    • Taking into account sulfates causes data to be consistent with observed temperatures (last sentence)
  • Cause-and-effect relationship:
    • Airborne sulfates cause solar energy to reflect back to space, which causes a lowering of the temperature (third sentence)
  • Example of sources of sulfates:
    • Natural sources, like volcanoes (third sentence)
    • Human technological sources (third sentence)
  • Author's attitude: "somewhat inconsistent" (first sentence); "more accurately" (second sentence); "important factor" (second sentence)

Paragraph 3

• Paragraph note
  • Alternative explanation (solar energy) and rebuttal (can't explain long-term and extreme fluctuations); author's conclusion
• Views, minor Meta-Structures, and the author's attitude
  • Solar energy view:
    • The sun's heating effects have changed the earth's atmospheric temperature (first and second sentences)
  • Author's view:
    • Solar energy models can explain yearly fluctuations but not the long-term, extreme increases in average temperature (third through fifth sentences)
    • The earth's annual temperature has increased, and the greenhouse effect is the best explanation for that increase (last sentence)
  • Author's attitude: "strong" (second sentence); "cannot account for the entirety" (third sentence); "it seems reasonable to conclude" (last sentence)

Main Point: New methods in data collection and analysis establish the greenhouse effect as the most likely cause of the rise in annual global temperatures.

Paragraph 1, Sentence 1 (P1, S1) - Description of phenomenon (rise in temperatures)

P1, S3 - Explanation of phenomenon (greenhouse effect)

P2, S1 - Issue with explanation (inconsistencies in early models)

P2, S2-4 - Correction of the issue (airborne sulfates account for inconsistencies)

P3, S1 - Alternative explanation (changes are due to variations in solar energy)

P3, S3 - Rebuttal of the alternative explanation (can't account for the entirety)

P3, S6 - Author's conclusion

Phenomenon/Explanation: This passage follows the Phenomenon/Explanation Meta-Structure. When passages utilize this Meta-Structure, the initial paragraphs typically describe an observable fact, behavior, or situation. We call these "phenomena." The author then describes one or more "explanations" of why the observable fact, behavior, or situation occurs in later paragraphs.

This passage follows that model closely. In the first two sentences of the first paragraph, the author describes and supports the phenomenon — Earth's increasing annual temperatures — through references to data. In the last sentence of that paragraph, the author introduces a "controversial" explanation for the increase: the greenhouse gas effect. The author describes and accounts for some issues with this explanation in the second paragraph and rebuts an alternative explanation in the third paragraph*. Ultimately, the author concludes that the greenhouse effect is the best explanation for the phenomenon in the last sentence. Since the main point is generally the explanation the author presents or endorses in a Phenomenon/Explanation passage, we can use that sentence to help us answer the main point question.

*Because the author uses the second and third paragraphs to rebut criticisms or issues with the greenhouse effect explanation, some may view this as a Rebutting Critics or Criticizing a Viewpoint passage. However, these rebuttals support the author's preferred explanation, so we felt the Phenomenon/Explanation Meta-Structure fit this entire passage's structure better.

Passages tend to be a bit dated in Reading Comprehension. So, if you felt it was odd that the passage referred to the link between atmospheric gases and temperature increases as "controversial" within the scientific community, that's your explanation. (Helpfully, the caption above the passage clarifies how old this passage is.) Let this remind us that we shouldn't bring our prior knowledge or assumptions about a topic into our reading method. While we may rely on some well-known or common-sense beliefs and suppositions in Reading Comprehension (for instance, it would be difficult to understand this passage without knowing that there's an atmosphere surrounding the earth), almost everything we'll need to answer the questions is written in the passage. We need to read and understand the actual text of the passage — we shouldn't rely on any specific or specialized extra-textual knowledge or beliefs about the subject matter on Reading Comprehension.